Stainless steels, problems causes-remedies

(02). Chapters / Topics List 2
(A). General info on Stainless Steel (Austenitic) Page
(A1) Introduction to Austenitic Stainless Steels 4
(A2) Monuments & Extraordinary Structures, made of Stainless Steels 6
(A3) Austenitic Stainless Steel - Family 8
(A4) Austenitic Stainless Steel - Properties 12
(A5) Why Stainless Steel is Shining and not Rusting : Passive Layer 23
(A6) Austenitic Stainless Steel, Selection & Applications 26
(A7) SS200 series, Alternative to SS300 series 33
(A8) Stainless Steel Surface Finishes 35
(A9) Advances in Stainless Steel Making 50
(A10) Stainless Steels, Consumption, Production, Cost 54
(B). Stainless Steels (Austenitic) : Problems, Causes, Cures
(B0) Brief Indtroduction to SS Problems and Problems List 58
(B1) Cold Work on SS, increases Strength, Hardness, Brittleness. Decreases Ductility 61
(B2) Galling & Jamming of Threads of SS Fasteners , moving components 65
(B3) Sensitization , Weld Decay, Knifeline Attack 66
(B4) Corrosion Attack Specific to Stainless Steels 72
(B4a) Corrosion - General 76
(B4b) High Temperature Corrosion 87
(B5) Delta Ferrites, in Stainless Steel Welds and Base Metal 91
(B6) Solidification Hot Crack on Castings and Welding 97
(B7) Formation of Brittle Sigma Phase 118
(B8) Large Thermal Expansion and Poor Heat Conduction of Stainless Steels 122
(B9) Zinc Poisoning of Stainless Steels 124
(B10) Contamination or Pollution on Stainless Steel Surface 126
(B11) Stains on Stainless Steel surface. Cause and Removal 131
(B12) Stainless Steel Mafg: Difficulties-Casting, Machining, Forming, Cutting, Welding, HT 140
(B13) SS Welding, List of Problems 153
(B14) SS Welding, Control of Root Welding (Critical SS Works) 156
(B15) SS Welding, SS Weld HAZ Surface Area is Colored or Tinted 157
(B16) SS Welding, Welding Distortion of Stainless Steel Material 159
Stainless Steels (Austenitic) : Problems, Causes, Remedies By JGC Annamalai

(02). Chapters / Topics List 2
By JGC Annamalai
(C). Annexure
An1 Annexure, Pickling & Passivation of Stainless Steel Products 161
An2 Annexure, Solution Annealing of Stainless Steel Products 166
An3 Annexure, Chronology, Events & Mile-Stone Developments of Stainless Steel 171
An4 Annexure, ASTM List of Stainless Steel & Literatures for Further Reading. 181
An5 Annexure, Galvanic Tables for Metals. 184
An6 Annexure, ACI, Cast Stainless and Heat Resisting Steels, Grades & Equivalents 185
An7 Annexure, Stainless Steels, Equivalents 186
An8 Annexure, Role of Alloying Elements in Stainless Steels 191
An9 Annexure, Purging, during Welding 194
An10 Annexure, Development of Stainless Steel Constitution Diagrams 197
An11 Annexure, Chemical Resistance Tables 205
An12 Annexure, Quick Guide to Type-304 and Type-316 209
Total Pages 214
Authored by R.Annamalai, (former Chief Equipment Engineer, JGC Corporation), rannamalai.jgc@gmail.com

Stainless Steels (Austenitic) : Problems, Causes, Remedies
Stainless Steel, other names : SS, SUS. Inox, Silver Steel, Rustless Steel
Aus. SS are face-centered cubic structure. Though generally SS is ductile, easily formable and easily weldable, some
grades can be prone to sensitization at the weld heat-affected zone and crack at hot weld metal or in service condition.
Engineers aware that stainless steel is corrosion resistant, strong, good for high temperature and low temperature service.
Metallurgists define, stainless steel as an alloy of iron, with carbon from 0.03 to 0.55% and Chromium from 10.5 to 30%
General public know about stainless steel that it is shining and strong and not rusting.
Chapter-A1 Introduction to Stainless Steels
Stainless Steel(SS-410) was discovered in 1913 by Sheffield Metallurgist, Harry Brearley. There were also claims, from
Germany, France, Poland, Sweeden and Russia as first to invent SS, in the same period. Established record shows, in
1912 Maurer and Strauss, Krupp Works, Germany, found Austenitic alloy(SS 3xx), containing 20%Cr and 7% Ni(similar
to today 18-8 alloy or SS type 304).
In metallurgy, Stainless Steel, (Inox for SS in French), is a steel alloy with a minimum/threshold limit of 10.5% chromium
content by mass. Normally, 12% Cr is fixed as min. for commercial stainless steel. Some SS has as high as 30% Cr.
Chromium produces a thin transparent passive layer of Chromium Oxide (1 to 5 x 10-6
mm or 1 to 5 nm (1 to 5 x10
-9
m)
thick) on the surface of the SS. Increasing the amount of Chromium and Nickel gives higher passive layer thickness and
increased resistance to corrosion.
Compare,
Stainless
Steel, with
other
common
metals /
alloys
By JGC Annamalai
Alloy C Mn P S Si Cr Ni Mo Cu N
304L 0.03 2 0.045 0.03 1 18.00-
20.00
8.00-
12.00
0.75 0.75 0.1
Alloy Temper Tensile
StrengthMin.
Yield StrengthMin.
0.2% offset
Elongation in 2"
Min.(%)
304L Annealed 70000 psi 25000 psi 40%
482 MPa 172 MPa
Melting
Point
Density Specific
Gravity
Modulus of
Elasticity in
2550-2590° F 0.285 lb/in³ 7.90 29 X 106
psi
1399-1421° C 7.90 g/cm³ 200 GPa
4

Chapter-A1 Introduction to Stainless Steels
By JGC Annamalai
Alloy C Mn P S Si Cr Ni Mo Cu N
304L 0.03 2 0.045 0.03 1 18.00-
20.00
8.00-
12.00
0.75 0.75 0.1
Alloy Temper Tensile
StrengthMin.
Yield StrengthMin.
0.2% offset
Elongation in 2"
Min.(%)
304L Annealed 70000 psi 25000 psi 40%
482 MPa 172 MPa
Melting
Point
Density Specific
Gravity
Modulus of
Elasticity in
2550-2590° F 0.285 lb/in³ 7.90 29 X 106
psi
1399-1421° C 7.90 g/cm³ 200 GPa
Many Problems, Failures, Difficulties, mentioned here, are noticed in Service. Source location is mostly Fabrication Shop.
 In 1919, Elwood Haynes obtained a patent on martensitic stainless steel





 In 1926, the first surgical implants made of stainless steel were performed

 In the 1930s, the first stainless steel train was built in the USA
 The year 1931 witnessed the creation of the first stainless steel aircraft
 By 1935, stainless steel kitchen sinks were widely used




 Global production of stainless steel reached 31 million Mt in 2010
 About 11 million washing machines with stainless steel drums were produced in China in 2010
 Over the last 100 years, over 200 grades of stainless steels have been discovered and made commercially available
Stainless Steel Today
In this Document, we will limit our discussion to the Austenitic Stainless Steels, although many of the discussion /
comments will apply to the other types as well. We had discussed many issues, common to all stainless steels. Common
Defects related to manufacturing, like for Welding(slags,porosity, LP etc), or for Casting(segrigation, porosity etc), for
Forming (like cold shuts, flakes, wrinkles, spring back, Die Shift etc) are not discussed here.
Between the years 1919 and 1923, the use of stainless steel was adapted
to the manufacturing of surgical scalpels, tools, and cutlery in Sheffield
In 1930, duplex stainless steel was first produced in Sweden at the Avesta
Ironworks
Invention and major achievements in Stainless Steel:
In 13 Aug 1913, Harry Brearley of Sheffield, UK discovered "rustless" steel. Although
there had been many prior attempts, Brearley has been credited with inventing the first
true stainless steel, which had a 12.8% Chromium, 0.24% Carbon content. The SS was
produced in an electric furnace. Total weight was about 6 tons. Harry Bearley was
subsequently awarded the Iron and Steel Institute's Bessemer Gold Medal in 1920
American Society for Metals (ASM) gives the date for Brearley's creation of casting
number 1008 (85.32% iron, 0.24% carbon, 12.8% chromium, 0.44% manganese, 0.2%
silicon) as 20 August 1913. The steel was close to present Martensitic SS.
in 1929 William J. Kroll of Luxembourg was the first to discover
precipitation-hardening stainless steel
After the initial discovery, further improvements to stainless steel occurred
at a fairly rapid pace
Stainless steel has found a myriad of applications from the tiniest structural parts in artificial heart valves to the largest
architectural structures and process equipments. Several world famous monuments, such as the Cloud Gate sculpture in
Chicago, Gateway Arch, in St. Louis, have been constructed using stainless steel.
In the early 1920s, a variety of chromium and nickel combinations were
tested. Stainless steel was referred to as “18/8” to indicate the percentage
of chromium and nickel in the steel.
In 1925, a stainless steel tank was used to store nitric acid, thereby
establishing the fact of this unique metal's resistance to corrosion
The hygienic aspect of the stainless steel was demonstrated in 1928 when
the first stainless steel fermenting vessel was used to brew beer. Since
then the food and beverage industry have widely used this stainless steels.
Today, China is the largest producer of stainless steel in the world. One of the leading stainless steel producers and
distributors is Outokumpu, a group of companies headquartered in Espoo, Finland.
In 1954, First AOD was invented (Ar-O2 Decarburization) to refine(low C &
low S) stainless steel, by Union Carbide
In 1966, the first tidal power station with stainless steel turbine blades was
completed in France
In the 1980s, stainless steel was used to build the longest movable flood
barrier in the world on the river Thames
Type 430 stainless steel (ferritic chromium alloy) was used to make a wire
0.1mm in diameter for a voice-recording machine
Earlier to 1950, process vessels were mostly made of CS. Due to corrosion etc, SS are prefered. But considering cost,
people go for coating/lining, Ni-Cr Plating or clading or Weld overlay with SS on CS base metal to withstand corrosion.
Mild steel(MS or CS) is the most commonly used material in metal fabrication. Stainless steel and aluminum alloys, are
attractive for many applications, like corrosion resistance, aesthetics, high strength-to-weight ratio, thermal properties,
Cryogenic properties and impact loading, high vacuum services etc.
5

Stainless Steels (Austenitic): Problems, Causes, Remedies
Monuments & Extraordinary Structures, made of Stainless Steels
Chapter-A2
SS surface is highly polished to have mirror effect
By JGC Annamalai
6

Monuments & Extraordinary Structures, made of Stainless Steels
Chapter-A2
By JGC Annamalai
22
7

Other names : Stainless Steel Group, Stainless Steel Types, Stainless Steel Categories
* Austenitic Stainless Steels: which contain
* Ferritic stainless steels: which contain
* Martensitic Stainless Steels: around
* Duplex Stainless Steels:
Stainless Steel Family : Stainless steels contain typically 10-30 % chromium besides other elements like C, Mn, Si,
S etc. Chromium gives corrosion resistance to steel. Varying amounts of other alloying elements like Ni, Mo, V, Ti, N, etc
may be added to obtain certain specific property. There are different types of stainless steels like
13% Cr and C varying in 0.15 to 0.95%
* Precipitation Hardenable Stainless Steel:
Chapter-A3 Stainless Steel Family (Austenitic, Ferritic, Martensitic, Duplex, PH)
12% to 30% Cr and 0.08% to 0.12%C
Cr is around 25% (≈50% Austenite &≈ 50% Ferrite)
contains:18-20% Cr, 8 to 10 % Ni and Cu, Al, Ti
18% Cr, 8% Ni, and C is in between 0.03-0.15%
By JGC Annamalai
8

Al Aluminum Co Cobalt N Nitrogen Se Selenium
C Carbon Cu Copper Ni Nickel Si Silicon
Cr Chromium Mn Manganese P Phosphorus Ta Tantalum
Cb Columbium Mo Molybdenum S Sulfur Ti Titanium
Alternative
Type
of
Austenitic
Stainless
Steel
Tree 9

Others, commonly used are:
Grain Structures of : Ferrite, Austenite, Martensite, Duplex Stainless Steels & Unit Cells
Here 17/4 means :
average 17% Cr & 4% Ni.
Precipitation Hardened(PH) Steels, are
either Martensitic or Ausitinitic-
Martensitic Stainless Steels
Duplex Stainless Steels
PH Stainless Steels
Duplex Stainless Steels are 50% Ferritic
& 50% Austenitic Stainless Steels
10

SS Group AISI Type % Carbon%Chrome%Nickel % Other Elements Prime Uses
405 0.08 max 11.5-14.5 0.5 max 0.1-0.3 Al Al prevents hardening
430 0.12 max 14-18 0.5 max - Auto trim, tableware
442 0.25 max 18-23 0.5 max - Resists O and S at high temp
446 0.20 max 23-27 0.5 max 0.25N max
201 0.15 max 16-18 3.5-5.5 5.0-7.5 Mn 0.25N max Mn substitute for Ni
202 0.15 max 17-19 4-6 7.5—10 Mn 0.25N max Strain hardens
301 0.15 max 16-18 6-8 2 Mn max Architectural uses
302 0.15 max 17-19 8-10 2 Mn max Si for high-temp.oxidation
302B 0.15 max 17-19 8-10 2-3 Si Continuous 18-8S
304 0.08 max 18-20 8-12 1 Si max Very low carbon
304L 0.03 max 18-20 8-12 1 Si max "High" 18-8
308 0.08 max 19-21 10-12 1 Si max 25-12, hear resistance
309 0.2 max 22-24 12-15 1 Si max Lower carbon
309S 0.08 max 22-24 12-15 1 Si max 25-20, heat resistance
310 0.25 max 24-26 19-22 1.5 Si max Lower carbon
310S 0.08 max 24-26 19-22 1.5 Si max Si for high-temp.
314 0.25 max 23-26 19-22 1.5-3.0 Oxidation
316 0.10 max 16-18 10-14 2-3 Mo 18-SS MO
316L 0.03 max 16-18 10-14 2-3 Mo Very low carbon
317 0.08 max 18-20 11-14 3-4 Mo Higher Mo
321 0.08 max 17-19 8-11 Ti 4 X C(min) Ti stabilized
347 0.08 max 17-19 9-13 Cb + Ta10 X C(min) Cb stabilized
Alloy 20* 0.07 max 29 20 3.25 Cu, 2.25 Mo Best corrosion resistance
SS Group AISI Type % Carbon%Chrome%Nickel % Other Elements Prime Uses
410 0.15 max 11.5-13.5 - - Turbine blades, valve trim
416 0.15 max 12-14 - Se, Mo, or Zr "Free" machining
420 0.35-0.45 12-14 - - Cutlery
431 0.2 max 15-17 1.25-2.5 - Improved ductility
440A 0.60-0.75 16-18 - - Very hard; cutters
322 0.07 17 7 0.07 Ti, 0.2 Al
17-7PH 0.07 17 7 1.0 Al
17-4PH 0.05 16.5 4.25 4.0 Cu
14-8MoPH 0.05 max 14 8.5 2.5 Mo, 1% A1
AM350 0.1 16.5 4.3 2.75 M0
CD4MCu 0.03 25 5 3.0 Cu, 2.0 Mo
2101 0.04 21 1.5 Mo=0.5,N=0.22,Mn=5
2102 0.03 21.5 1.5 Mo=0.5,N=0.21,Mn=2.5
2202 0.03 22 2 Mo=0.5,N=0.22,
2304 0.03 23 4 Mo=0.5,N=0.12,
2205 0.03 22.5 5 Mo=3.2,N=0.16,
2003 0.03 20 3.5 Mo=1.5,N=0.22,
2404 0.03 24 3.5 Mo=1.5,N=0.22,
2507 0.03 25 7 Mo=4,N=0.28,Cu=0.5
255 0.03 25.5 5.5 Mo=3.4,N=0.2,Cu=2
Z100 0.03 25 7 Mo=3.5,N=0.25,W=0.75,Cu=0.75
Stainless Steel Family & Chemical Composition Stainless Steel Family & Chemical Composition
Austenitic
Chromium-Nickel
SS
Ferritic
Non-
hardenable
SS
Martensitic
Chromium
SS
Age
Haredenable
SS
Used in oil and gas, nuclear
and aerospace industries
where a combination of high
strength, corrosion
resistance required. Not
good for cryo service.
Lean
Duplex
SS
Corrosion resistance, tensile,
yield, % elangation, Fatique
resitance better than
SS304L & SS316L. Can be
used upto -46°C
Duplex
SS
Super
Duplex
SS
Extensively used for Chloride
Stress Corrosion service
11

* Austenitic Stainless Steels: which contain
* Ferritic stainless steels: which contain
* Martensitic Stainless Steels: which contain
* Duplex Stainless Steels:
Cr is around 25% (50% Austenite & 50% Ferrite)
18-20% Cr, 8 to 10 % Ni and Cu, Al, Ti
around 13% Cr and C varying in 0.15 to 0.95%
* Precipitation Hardenable Stainless Steel: contain
(1). Stainless Steel Family : Stainless steels contain typically 10-30 % chromium besides other elements like C,
Mn, Si, S etc. Chromium gives corrosion resistance to steel. Varying amounts of other alloying elements like Ni, Mn, Mo,
V, Ti, N, etc may be added to obtain certain specific properties. Majority of Stainless steels are grouped into 5 types.
12% to 30% Cr and 0.08% to 0.12%C
18% Cr, 8% Ni, and C is in between 0.03-0.15%
Stainless Steel - Properties
Chapter-A4
By JGC Annamalai
Ferrite Formers Cr, Si, Mo, Nb, W
Austenite Formers C, Ni, Mn, Cu, N
12

Chapter-A4
By JGC Annamalai
(2). Why Stainless Steel is Shining, non rusting & corrosive resistance ? ; Reason - Passive Layer
(3). Some more metallurgical properties of Austenitic Stainless Steels:
(a).
(c).
(d).
(e).
(f).
Stainless steels is not affected by Citric Acid and vinegars and acids in the vegitables .From 1920, all most all kitchen
hardwares/ tablewares and vessels and tools to store or handle food related items use stainless steel material.
Corrosion Resistant: Due to Corrosion Resistance, Stainless Steel is used in Food Industry, Diary, Distillary, Chemical
and Oil & Gas Industry, Nuclear Plants, Space Research & in household utencils and hand rails, stairs, decorative frames
etc. (it is not fully stain-proof in low-oxygen, high-salinity, or when it is contaminated).
Steel with chromium 10.5% and above is called Stainless Steel. If the surface is cut or machined, a passive layer of
chromium oxide (say 3.5 nm thickness) is immediately formed. This layer protect the SS from general corrosion. So, it is
Stainless Steel. More details are found on "Passive Layer" in the forth-coming pages.
Stainless steels are not rusting and not affected by body fluids and fairly maintenance free. It has hygienic surface and so
used in surgery tools. (EHEDG,European Hygenc Engg & Design Gr, Doc. 8, 2004: Hygienic Equipment Design Criteria).
High Temperatures: Higher carbon will increase the mechanical strength. 0.25% C is allowed in SS310 and 0.2 to
0.6%C is allowed in HK high temperature steels. Here corrosion is considered , as second priority.
Heat Treatment: Nickel stabilizes the austenite at room temperature or further below. There is no phase change.
So, austenitic stainless steel cannot be quenched and hardened or heat treatment cannot improve mech.
properties. There is no formation of martensite (the hardening component), due to temperatures increase from
room tempertures. .
Further, no heat treatment is done above 450°C as there is a possibility of forming Sensitization. So, normally,
Heat Treatment is not recommended. Sometime, Stress relieving is done below 450°C. This way only 20 to 30% of
residual stresses are removed.
PWHT: Normally, PWHT is not done. Reason, same as for Heat Treatment. Sometime, PWHT is applied or
thicker SS or CS cladded with SS.
As Nickel % increases, alpha (α) region is suppressed and gamma(γ) loop is expanded. At room temperature, only
austenite and carbides are present, for all Carbon percentage. At room temperature, no hardenable Alpha ferrite or
no martensite , is present.
(b). For corrosion applications, the carbon content, should be controlled. Say, for SS304, Carbon is 0.08%C
maximum. For welding, the carbon should be further lowered. Say for SS304L, the Carbon is 0.03%C maximum.
Welding: On CS, 0.35% max carbon is allowed by ASME. On SS, higher the %Carbon, higher the sensitization.
For Extra Low Carbon,"L or ELC" grades, lowering the carbon(say from 0.08 to 0.03%), will decrease the
mechanical strength. Stabilizing elements, Titanium, (Ti, in SS321) or Colombium or Niobium (Cb or Nb in SS347)
have more affinity to Carbon and these stabilzing elements are added, to form their carbides, thus freeing
Chromium. Chromium will stay in solid solution and give corrosion resistance and Carbon will give Strength.
Stainless Steel, 300 series. Effect of Nickel and Carbon on a 18% Chrome Steel. Gamma, "γ" , representing
austenitic SS loop expands as Nickel % is increased. Delta ferrite is almost invisible, for 8% Nickel and above.
13

Chapter-A4
By JGC Annamalai
(g).
(h).
(4). SS Castings are always specified by ACI numbers. Wrought grades are specified by AISI number. Their equivalents
(5). Cold Working on Stainless Steels:
(6). Electricity and Magnetism, (of Stainless Steels)
Preheating, before welding: Normally Carbon Steel, over 3/4"(20mm) or low alloys require preheating, as
welding heat spread to the (far away) lower temperature area, at a faster rate. This type of high speed cooling
is like quenching and normally increases the formation of martensite or cementite. These are hard material/
compounds and may produce fissures or cracks. Preheat retards the speed of heat spreading. Preheat is also
used to drive away the Hydrogen.
In Aus SS, there is no phase change or there is no hard material formed because of fast rate of cooling. So no
preheat is required.
However, in cold countries, to drive away the moisture, often, the base material is heated to hand warm
temperature or to a temperature max. 250°C for distortion control purpose.
Ferritic SS are fully magnetic. Martensitic SS are slightly magnetic. Wrought & fully annealed Austenitic SS, is
normally non-magnetic.
Due to ferrite present in SS Castings and cold rolled Aus SS(due to slight martensitic formation) and martensitic
SS are slightly magnetic. Cryogenic temperature also causes straining and longer grains and martensitic and high
tensile strengths are observed.
It is not possible to increase the strength of Austenitic Stainless
steels, by Heat Treatments, as it contains no martensite or
negligible martensite.
Often, for thick carbon steel and low alloy steel, minimum preheat & interpass temperatures, are mentioned. For
SS304 & other Aus SS, maximum preheat and interpass temperatures (250°C) are mentioned.
However, cold working on stainless steel, forms martensite /
elangated grains and it is possible to increase the Strength,
hardness. Cold work on SS causes SS to brittle and crack, pre-
maturedly.
Castings are normally made for valves, pumps, and machinery parts, where no further rolling action will be followed. Their
wall thickness are normally thin and intricate shapes can be made. To control fluidity/liquid viscosity, Silicon is added, upto
2%. Wrought steels, used to have silicon less than 1%. Higher the ferrite number, higher the strength. Often, rolling mill
rolls fails, because of high forces due to high ferrite numbers. So, wrought products are ferrite number controlled to
reduce the rolling forces. As there is no rolling operation, Castings always have higher ferrite number. Foundries control
the ferrite number by adjusting the ferrite formers(Cr, Si, Mo , W, Ti) and Austenite formers(Ni,C, Mn, N, Cu) etc.
are for guidance only. They are not fully equivalents. (Please refer Annex-6, for Cast and Wrought SS equivalents)
Like steel, Stainless steels are relatively poor conductors of electricity, comparing to copper.
Due to cold work, the residual stress may stay with the material,
after cold work. The material may fail, with the residual stress,
and increase in service stress, stresses due to temperature or
shock. Further, % elangaton is reduced and the surface is
hardened..
Remedy : Cold working on SS , need slow & at room
temperature operation, with lubrication. Solution Annealing,
between stages are highly recommended. Also long radius
should be followed for bending
Ferritic SS are fully magnetic, Martensitic SS are slightly magnetic and Wrought fully annealed Austenitic SS, is normally
non-magnetic. Solution annealing makes the austenitic stainless steels non-magnetic.
Work hardened / cold worked or welded material will make austenitic stainless steels slightly magnetic
Any process which can change the crystal structure of stainless steel can cause austenite to be converted to the
ferromagnetic martensite or ferrite forms of iron. These processes include (1). cold working, (2). welding, (3). cold
temperature causes length reduction and straining. Austenite is spontaneously converted to martensite at low
temperatures / cryo temperatures.
The following properties
are Increasing:
The following properties
are Decreasing:
(1). Hardness (1). Ductility, % Elangation
(2). Tensile Strength (2). Corrosion Resistance
(3). Brittleness (3). Impact Strength
(4). Magnetism
14

Chapter-A4
By JGC Annamalai
Tensile Strength for some common ASME materials:
(8). Compare, Physical & Mechanical Properties of Mild Steel & Stainless Steel with Temperature :
(9). Compare, Thermal Conductivity & Linear Thermal Expansion of Stainless Steels with Temperature :
Cure: Removal of Magnetism & residual stresses : (1). Non-
corrosive Service, by Stress Relieving at 425 to 925°C (2).
Corrosive Service, as SS will be sensitized at the 450 to
925°C, Full solution annealing of SS at 1080°C followed by
rapid cooling, eliminates all magnetism & residual stresses
(7). It is stronger than CS:
Thrmal conductivity : Comparison on 3 class of SS, Martensitic stainless steel is having high thermal conductivities.
Austenitic Stainless steel is having low conductivity. Ferritic stainless steel has moderate thermal conductivity.
So, martensitic stainless steels can be used in heater, heat exchangers, boiler etc for higher better thermal conductivity.
Welding, ductility(% elangation) are poor. So, they are not used, where such properties are required.
Thermal Expansion: Austenitic stainless steel has very high expansion and ferritic and martensitic stainless steels have
low thermal expansion (they are similar to CS, in thermal expansion).
Applications: Electrodes : Coated electrodes of Aus.SS are shorter by about 30%, comparing to CS, as Aus SS has very
high thermal expansions and poor heat conductivity. The electrodes are heated by welding current and the coating are
found spalling and the rods are bent, due to excess heat. Aus SS structures have high distortions due to high expansion.
Ferrites are considered that they produce magnetism.
Most of the instruments and magnetic type apparatus,
require non-magnetic stainless steels, to control effect of
Hysterisis losses and Eddy current losses and magnetic pull.
ITER (International Thermonuclear Experimental Reactor, for
Fusion Energy, France) - two helical coils and three pairs of
poloidal coils, are made of superconducting conductors,
using, SUS 316 materials, with ferrite, less than 1.5%, to
control magnetism / Hysterisis and Eddy current losses.
The mechanical tensile strength, is more than CS. .
Where-ever, weight ratio of SS to CS is lesser and less
weight ratio is preferred, SS is used, eg. airplane
structures.
15

Chapter-A4
By JGC Annamalai
(11). Forming is easier on Full annealed Austenitic SS and to Weld:
(12). SS High Temperature Properties & Applications, Material Selection, for High Temperature Service:
Selection of material, for high temperature service is mainly based on their stability (not oxidized and not much scale is
formed) at high temperatures (compared to CS).
(10). No Phase Change: Unlike carbon and low alloy steels the austenitic stainless steels undergo no big phase changes
as they cool from melting temperatures.
Welding and Heat Treatment do not increase hardness. Cold
(hydrogen induced) cracking is therefore not a problem and
preheat for welding is not necessary, irrespective of
component thickness. Strength and hardness cannot be
improved by Heat Treatment. Cold work on Aus SS can give
higher strength and hardness . For limited distortion control,
PWHT can be conducted below 400°C. Over 400°C ,
sensitization occurs, so PWHT is not followed.
Annealed Aus SS has 40% elangation and forming is easier. It can be welded by most of the welding processes.
SS 310 or SS 309, the High Chromium - high nickel SS makes them, as oxidation resistance and used in high temperature
furnace & flare services. Stainless steel is scale resistance upto 1000°C, wheras scales are found on CS around 600°C.
So, SS is used in boilers, heaters, flare stack supports and similar applications.
16

Chapter-A4
By JGC Annamalai
Material Selection for High Temperatures : (5). Inside Fluids : Resitance to the new corrodants, formed
due to high temperatures of fluids.
(6). Flue Gases : Resistance to High Temperature Corrosion
due to burning of the combustion gases, flue gases and
flare gases
For moderate temperatures, Boiler Drums are made up of Carbon Steel. As the temperature increases, low alloy
(chromium-molibdenum alloy) are used. Super heater tubes are made up Cr-Mo steels, stainless steels. Often Flare tips
& Furnace Burner Tips are made up of Stainless Steels 310 and 309 and Inconel 600, 625, Incoloy 800, to resist high
temperature oxidation, scalling and corrosion. Super heater tubes and headers in Super-critical thermal power plants, are
made with SS 316L material.
(1). Higher Strength at the higher temeperatures
(2). Resistance to oxidation
(3). Resistance to scale formation.
(4). Low coefficient of Thermal Expansion of parts,
for machines, gas Turbines etc
17

Chapter-A4
By JGC Annamalai
(14). Material Selection, High/ultra high Vacuum Service:
(17). Stainless Steel for Food and Sanitation(Medical):
EHEDG Material Requirement: (3).mechanically stable (6). Inert to the Product,
(1).Not tranfer undesirable odours. (4).non-toxic, (7).corrosion resistant,
(2). Inert to the detergents and disinfectants (5).non-tainting, (8).their surface finish must not be adversely affected
EN1672-2, Food Processing Machinery, Basic Concept; EHEDG Glossary EHEDG Position Papers
ISO14159, Safety of Equipments, Hygienic requirements EHEDG Spreads, Issue
EHEDG Doc-3, Packing Food EHEDG Overview – Guidelines
EHEDG Doc-4, Pesturization of Food Processing Eqpt EHEDG Doc 17- Hygienic design of pumps, homogenizer
EHEDG Doc-08, Design Principle EHEDG Doc-45, Cleaning;
How to identify Austenitic Stainless Steel:
Metal Identification Methods / Tests:
(1). Detailed Chemical Analysis for elements, from Chips and Samples(ASTM E350, E352, Chemical Analysis Methods)
(2). Detailed Spark Spectrum-Analysis on Chips and Samples
(3). Spot Analysis on object, using, Portable Metal Analysers (working on X-ray Diffraction / Fluorescence Technique)
(13). Material Selection, for Low Temperature &
Cryogenic Temperature Service:
Cryo Service: Due to exceptional toughness qualities of SS,
it is used in Cryo Services. Aus SS is face centered and has
high impact strength, at low and cryo temperatures. So, SS is
used for components in low and cryo temperature services.
SS components absorb more impact energy and they are
ductile at cryo temperatures. During accidents, the damages
are not severe, comparing to similar CS components and low
impact materials.
Stainless steels, are the logical preference for metallic materials of construction used for wet cleaned process plants but
the specific alloy depends on the application. Of them, SS304 and SS316L are mostly used.
Use of other metals(eg: mild steel, anodized aluminum) may be appropriate in a dry environment.
Quantitative chemical analysis is performed to accurately determine the concentration of elements in the material
comprising a given sample. A variety of analysis (gravimetric and titrimetric) techniques are used for metals and
alloys to determine the alloy composition of raw materials to verify conformance to a specification or to identify the
alloy used to make a specific component.
An x-ray tube or isotopes are used to irradiate the sample. This causes excitation and x rays are emitted
(fluorescence) to balance the energy difference between the electron states. The x ray energy is characteristic of
the element from which it was emitted. The fluorescence x rays are collimated and directed to an x ray detector.
Spark (optical) emission spectroscopy where rapid series of high energy sparks are created across the argon
filled gap between an electrode (cathode) and the prepared sample’s surface (acting as the anode). The sparks
first ionize the argon, the sparks melt & evaporate and excite. When the excited atoms relax to a lower energy
state, they emit light at characteristic wavelengths for each element. The wavelengths are measured and
identified,as %elements.
(15). Radition has little effect on Impact Strength and Ductility of Stainless Steel. (Due to irradiation, Carbon steel, losses
impact strength and effect: it becomes brittle, after long exposure to radiation, in service.)
The following documents of EN, ISO, EHEDG(Europian Hygienic Engineering & Design Group, part of Europian Union),
etc may be consulted for further info.
Most of the carbon steels, alloy steels are found leaking(de-gassing) through the grains and fails to maintain the high
vacuum (>10-6
torr)requirements. SS material has favorable degassing qualities(prevents permeation of air/gas through
SS material) and used for ultra high vacuum services. The SS grains are compact and they are resistant to de-gassing at
ultra high vacuum (>10-6
torr).
During 1900s, the potential use of stainless steel as an ideal material for food contact applications was recognized.
18

Chapter-A4
By JGC Annamalai
(4). The following tests are quick test to identify Stainless Steels.
Grain Structures of : Ferrite, Austenite, Martensite, Duplex Stainless Steels & Unit Cells
19

DIN
AISI UNS DIN C Mn Si P S Cr Ni Mo N OTHERS
Strength
limit
(MPa)
Yield
strength
(MPa)
Elon'n
50mm
(%)
Rockwell
-
B
Cold
bending
Erichsen
cup
test(mm)
Formability
Weldability
Corrosion
Density
(g/cm
3
)
Spe.
Heat
0-100
°C
(J/Kg.K)
Coeff.
of
thermal
Expansion
(μ/m
°C)
Melting
Range
(°C)
Magnetism
Elec.
Resist.
@20°C
(nΩ.m)
HeatCond.
@100
°C
(w/m.K)
Elasticity
Modulus
(GPa)
Rigidity
Modulus
(GPa)
201LN S20153 1.4376 0.03
'6.40-
7.50
0.20-
0.60
0.05 0.015
17.0-
17.5
4.0-4.5 -
0.15-
0.25
700 500 45 95 - - Good Excellent Fair 7.8 500 17.1
1400 -
1450
Annealed.
non-magnetic
690 16.2 197 86.2
201 S20100 1.4618 0.15
'5.50-
7.50
1 0.06 0.03
16.0-
18.0
3.5-5.5 - 0.25 515 260 40 - - - Good Excellent Fair 7.8 500 17.1
1400 -
1450
Annealed.
non-magnetic
690 16.2 197 86.2
301 S30100 1.4310 0.05 2 1
0.045
0.015
16.0-
18.0
6.0-8.0 - 0.1 - 910 320 46 86 180° 13 Better Better Fair 8 500 17.5
1400 -
1420
Annealed.
non-magnetic
720 16.2 193 86.2
301LN S30153 - 0.03 2 1 0.05 0.03
16.0-
18.0
6.0-8.0 -
0.07-
0.20
700 400 50 90 180º - Good Excellent Fair 8 500 17.5
1400 -
1425
Annealed.
non-magnetic
720 16.2 193 86.2
304 (1) S30400 1.4301 0.07 2 0.75
0.045
0.015
17.5-
19.5
8.0-
10.5
- 0.1 c 720 320 57 84 180° 12 Better Better Good 8 500 17.8
1400 -
1450
Annealed.
non-magnetic
720 16.2 193 86.2
304L S30403 1.4307 0.03 2 0.75
0.045
0.015
17.5-
19.5
8.0-
10.5
- 0.1 - 690 320 51 80 180° 12 Better Excellent Good 8 500 17.8
1400 -
1450
Annealed.
non-magnetic
720 16.2 193 86.2
304T S30400 1.4301 0.03 2 0.75 0.05 0.015
17.5-
19.5
9.0-
10.5
- 0.1 610 280 58 74 180º 12 Excellent Excellent Good 8 500 17.8
1400 -
1450
Annealed.
non-magnetic
720 16.2 196 86.2
304 (2) S30400 1.4301 0.07 2 0.75 0.05 0.015
17.5-
19.5
8.0-
10.5
- 0.1 600 280 58 75 180º 12 Excellent Better Good 8 500 17.8
1400 -
1450
Annealed.
non-magnetic
720 16.2 196 86.2
304H S30409 -
0.04-
0.10
2 0.75 0.05 0.03
18.0-
20.0
8.0-
10.5
- - 710 320 58 83 180º - Better Better Good 8 500 17.8
1400 -
1450
Annealed.
non-magnetic
720 16.2 193 86.2
316 S31600 1.4401 0.07 2 0.75
0.045
0.015
16.5-
18.0
10.0-
13.0
2.00-
2.5
0.1 - 650 340 51 82 180° 12 Better Better Better 8 500 16.5
1375 -
1400
Annealed.
non-magnetic
740 16.2 193 86.2
316L S31603 1.4404 0.03 2 0.75
0.045
0.015
16.5-
18.0
10.0-
13.0
2.00-
2.5
0.1 - 650 340 51 82 180° 12 Better Excellent Better 8 500 16.5
1375 -
1400
Annealed.
non-magnetic
740 16.2 193 86.2
317L S31703 - 0.03 2 0.75 0.05 0.03
18.0-
20.0
11.0-
15.0
3.0-4.0 0.1 650 330 45 87 180º - - Excellent Better 8 500 17.5
1375 -
1400
Annealed.
non-magnetic
790 14.4 200 86.2
310S/H
S31008 1.4845 0.035-
0.08
2 1.5 0.05 0.015
24.0-
26.0
19.0-
22.0
- - 600 380 42 83 180º - - Good Better 8 500 16.5
1400 -
1450
Annealed.
non-magnetic
780 14.2 200 86.2
321 S32100 1.4541 0.08 2 0.75
0.045
0.015
17.0-
19.0
9.0-
12.0
- 0.1 5(C+N)<Ti<0.70 670 260 42 78 180° 12 - Excellent Good 8 500 17.5
1400 -
1425
Annealed.
non-magnetic
720 16.1 193 86.2
347/H S34709 -
0.04-
0.08
2 0.75 0.05 0.03
17.0-
19.0
9.0-
13.0
- 0.02
Nb = 10 C min1.00
máx.
645 345 51 87 180º - - Better Good 8 500 17.5
1400 -
1425
Annealed.
non-magnetic
730 16.1 193 86.2
- - 1.4003 0.03 1.5 1 0.04 0.015
10.5-
12.5
1 - 0.03 475 280 30 80 180° - - Good Poor 7.8 460 11
1480 -
1530
Magnetic 570 24.9 200
409 S40910 1.4512 0.03 1 1 0.04 0.015 10.50-
11.7
0.5 - 0.03
6(C+N) < Ti < 0.50;
Nb = 0.17 máx.
420 250 40 67 180° 10 Better Good Poor 7.8 - 11.7
1480 -
1530
Magnetic - - - -
SS Physical Properties
ASTM SS Chemical Composition SS Mechanical Properties Service & Fabrication
20

DIN
Strength
limit
(MPa)
Yield
strength
(MPa)
Elon'n
50mm
(%)
Rockwell
-
B
Cold
bending
Erichsen
cup
test(mm)
Formability
Weldability
Corrosion
Density
(g/cm
3
)
Spe.
Heat
0-100
°C
(J/Kg.K)
Coeff.
of
thermal
Expansion
(μ/m
°C)
Melting
Range
(°C)
Magnetism
Elec.
Resist.
@20°C
(nΩ.m)
HeatCond.
@100
°C
(w/m.K)
Elasticity
Modulus
(GPa)
Rigidity
Modulus
(GPa)
ASTM SS Chemical Composition SS Mechanical Properties Service & Fabrication
409 S40920 14512 0.03 1 1 0.04 0.015 10.50-
11.7
0.5 - 0.03
10 (C+N)<Ti<0.50;
Nb=0.17max
410 245 40 67 180° 10 Better Good Poor 7.8 - 11.7
1480 -
1530
Magnetic - - - -
430 S43000 1.4016 0.08 1 1 0.04 0.015
16.0-
18.0
0.75 - - - 520 350 30 81 180° 9 Fair Fair Fair 7.8 460 10.9
1425 -
1510
Magnetic 600 26.1 200 86.2
- S43000 1.4016 0.08 1 1 0.04 0.015
16.0-
18.0
0.75 - - Nb = 0.60 máx. 480 330 31 79 180° 10 Better Good Fair 7.8 460 10.9
1425 -
1510
Magnetic 600 26.1 200 86.2
- S43932 - 0.03 1 1 0.04 0.015
17.0-
19.0
0.5 - 0.03
0.20 + 4(C + N) < Ti
+ Nb<0.75 Al =0.15
AI máx
460 305 34 76 180° 10 Better Good Fair 7.8 460 10.9 - Magnetic 630 24.2 200 86.2
- - 1.4509 0.03 1 1 0.04 0.015
17.5-
18.5
0.5 - 0.03
3C + 0.30 < Nb
<1.00; Ti = 0.10 a
0.60
460 295 35 77 180° 10 Better Good Fair - - - - Magnetic - - - -
- S44400 1.4521 0.025 1 1 0.04 0.03
17.5-
18.5
1
1.75-
2.50
0.035
0.20 + 4(C + N) < Ti
+ Nb<0.80
520 350 31 83 180° 9 Good Good Better 7.8 420 10.7 - Magnetic 620 26.8 200 86.2
410 S41000 1.4006
.08-
0.15
1 1 0.04 0.03
11.5-
13.5
0.75 65000 30000 20 80 Good Fair Fair 7.74 460 10.9
1450 -
1510
Magnetic 550 24.9 200 81
420 S42000 1.4028
0.15
min
1 1 0.04 0.03
12.0-
14.0
0.75 0.5 - - 620 370 26 87 - - - Poor Poor 7.8 460 10.9
1450 -
1510
Magnetic 550 24.9 200 81
- - 1.4116
0.45-
0.55
1 1 0.04 0.015
14.0-
14.5
-
0.50-
0.80
- V = 0.1 a 0.2 - - - 100 - - - Poor Poor 7.8 Magnetic
2304 S32304 1.4362 0.03 2 1 0.04 0.015
22.0-
24.0
3.50-
5.50
0.10-
0.60
0.05 a
0.20
Cu = 0.10 a 0.60 740 560 30 96 - - - Good Better 7.8 450 13.5 1465 Magnetic 800 17 200 86.2
2205
S32205/
S31803
1.4462 0.03 2 1 0.03 0.015
22.0-
23.0
4.50-
6.50
3.00-
3.50
0.14-
0.20
- 840 660 27 98 - - Good
Excell
ent
7.8 460 14.3
1460 -
1465
Magnetic 800 16 200 86.2
SSC
6Mo
S31254 1.4547 <0.02 1 0.70 0.30 0.010 20 18 6.1 0.2 Cu0.75 675 310 35 90 Difficult
Excell
ent
8.2 500 15.3
1354-
1404
890 11.8 196
PH-
17.4
S17400 0.07 1 1 0.04 0.03 17 4 Cu4,Nb&Ta0.3 1319 1170 5min
108-
116
Hard Fair Good 7.8 460 10.4
1400-
1450
Magnetic 800 17.9 197 70
21

Duplex Stainless Steel-Cast-Forged-Plate Equivalents: Group AISI Type % Carbon%Chrome%Nickel % Other Elements Prime Uses
201 0.15 max 16-18 3.5-5.5 5.0-7.5 Mn 0.25N max Mn substitute for Ni
202 0.15 max 17-19 4-6 7.5—10 Mn 0.25N max Strain hardens
301 0.15 max 16-18 6-8 2 Mn max Architectural uses
302 0.15 max 17-19 8-10 2 Mn max Si for high-temp.oxidation
302B 0.15 max 17-19 8-10 2-3 Si Continuous 18-8S
304 0.08 max 18-20 8-12 1 Si max Very low carbon
304L 0.03 max 18-20 8-12 1 Si max "High" 18-8
308 0.08 max 19-21 10-12 1 Si max 25-12, hear resistance
309 0.2 max 22-24 12-15 1 Si max Lower carbon
309S 0.08 max 22-24 12-15 1 Si max 25-20, heat resistance
310 0.25 max 24-26 19-22 1.5 Si max Lower carbon
310S 0.08 max 24-26 19-22 1.5 Si max Si for high-temp.
314 0.25 max 23-26 19-22 1.5-3.0 Oxidation
316 0.10 max 16-18 10-14 2-3 Mo 18-SS MO
316L 0.03 max 16-18 10-14 2-3 Mo Very low carbon
317 0.08 max 18-20 11-14 3-4 Mo Higher Mo
321 0.08 max 17-19 8-11 Ti 4 X C(min) Ti stabilized
347 0.08 max 17-19 9-13 Cb + Ta10 X C(min) Cb stabilized
Alloy 20* 0.07 max 29 20 3.25 Cu, 2.25 Mo Best corrosion resistance
405 0.08 max 11.5-14.5 0.5 max 0.1-0.3 Al Al prevents hardening
430 0.12 max 14-18 0.5 max - Auto trim, tableware
442 0.25 max 18-23 0.5 max - Resists O and S at high temp
446 0.20 max 23-27 0.5 max 0.25N max
410 0.15 max 11.5-13.5 - - Turbine blades, valve trim
416 0.15 max 12-14 - Se, Mo, or Zr "Free" machining
420 0.35-0.45 12-14 - - Cutlery
431 0.2 max 15-17 1.25-2.5 - Improved ductility
440A 0.60-0.75 16-18 - - Very hard; cutters
322 0.07 17 7 0.07 Ti, 0.2 Al
17-7PH 0.07 17 7 1.0 Al
17-4PH 0.05 16.5 4.25 4.0 Cu
14-8MoPH 0.05 max 14 8.5 2.5 Mo, 1% A1
AM350 0.1 16.5 4.3 2.75 M0
CD4MCu 0.03 25 5 3.0 Cu, 2.0 Mo
2101 0.04 21 1.5 Mo=0.5,N=0.22,Mn=5
2102 0.03 21.5 1.5 Mo=0.5,N=0.21,Mn=2.5
2202 0.03 22 2 Mo=0.5,N=0.22,
2304 0.03 23 4 Mo=0.5,N=0.12,
2205 0.03 22.5 5 Mo=3.2,N=0.16,
2003 0.03 20 3.5 Mo=1.5,N=0.22,
2404 0.03 24 3.5 Mo=1.5,N=0.22,
2507 0.03 25 7 Mo=4,N=0.28,Cu=0.5
255 0.03 25.5 5.5 Mo=3.4,N=0.2,Cu=2
Z100 0.03 25 7 Mo=3.5,N=0.25,W=0.75,Cu=0.75
Stainless Steel Group & Chemical Composition Table
Duplex
SS
Super
Duplex
SS
Austenitic
C
hromium-Nickel
SS
Age
Haredenable
SS
Martensitic
Chromium
SS
Lean
Duplex
SS
Extensively used for
Chloride Stress Corrosion
service
Corrosion resistance, tensile,
yield, % elangation, Fatique
resitance better than
SS304L & SS316L. Can be
used upto -46°C
Used in oil and gas, nuclear
and aerospace industries
where a combination of high
strength, corrosion
resistance required. Not
good for cryo service.
Ferritic
Non-
hardenable
SS
22

Why Stainless Steel is Shining, corrosive resistance & non rusting?
2Fe+O2D2FeO 3FeO+CO2DFe3O4+CO FeO, metallurgical ore(rust) name is "wustite", Gray or Red color
4FeO+O2D2Fe2O3 Fe+H2ODFeO+H2 Fe2O3, metallurgical ore(rust) name is "hematite", Red color
Fe+CO2DFeO+CO 3FeO+H2ODFe3O4+H2 Fe3O4, metallurgical ore(rust) name is "magnetite", Black color
How Passive layer forms :
When carbon steel and stainless steel are
lathe machined, both have shining surfaces.
However, carbon steel surface is slowly
oxidized (normally, in 2 hours) .Most of the Iron
oxides(rust) are Red or dark brown or black in
color. The rust is mostly Fe2O3, Hematite type.
Chapter-A5 Why, SS Surface is Shining and not Rusting - Passive Layer
Passivation, means material becoming "passive," that is, less affected or not corroded by the environment.
Passivation involves creation of an outer layer of shield material that is applied as a microcoating, created by chemical
reaction with the base material, or allowed to build from spontaneous oxidation in the air. This light coat is mostly from Cr,
Ni, Mo oxides, on the surface of the Stainless Steel, is often called passive Layer.
Carbon Steel or Mild Steel is called "Black Steel" , as it is often seen, as rusty or blacky . Just machined carbon steel is
shiny like Stainless Steel. When CS is oxidized , it is black or dark brown rust color. Stainless steel is normally shining
and often called "Stainless Steel". Rust Volume is 2 to 3 times steel volume, if allowed the rust in confined space, will
initiate crack..
Passive layer, is resitant to many chemicals.Chlorine or chlorine based compounds break the passive layer and corrode.
Passive Layer : When the chromium in steel, is equal or over 10.5% and sufficient oxygen is present, Chromium forms a
passive surface layer of Chromium oxide (Cr2O3) and the passive layer is dominant and it spreads to full surface and it
prevents iron to form iron oxide and protects SS surface from outside corrosion.
Corrosion resistance is greatest when the SS is boldly exposed and the surface is maintained free of deposits (biofouling,
painting, or gasket etc) . The SS surface should have oxygen environment to form chromium oxide passive layer quickly.
Sometime it takes one day to form fully grown passive layer, equivalent to 80 nm(80x10
-9
meter).
By JGC Annamalai
Mechanism
of
Rusting
23

By JGC Annamalai
(1). passive layer is damaged,
(2).
(3).
Examples of some of the monuments / large structures, made up of Stainless Steels.
Damages to Passive Layer and Corrosion (SS304)
Passivation: ASTM A380 states that "Passivation is the removal of exogenous or free iron or iron compounds from the
surface of a stainless steel by chemical dissolution, most typically by a treatment with an acid solution that will remove the
surface contamination but will not significantly affect the stainless steel itself.
Passive Layer Thickness : Passive layer is transparent
and the thickness is from 2 to 80 nm(nanometer),
depending on the situation, availability of O2 etc.. The
passive layer is stable in many environments.
Corrosion will start and the surface will be rusty if
oxygen is not sufficient to form chromium oxide film
the corrodant chemical is strong and
reducing (like aquous chlorine, HCL acid)
SS surface is electrochemically passive. SS surface has normally, 1 to 5 nanometres,nm, (1 to 5 x 10-9
metres) thickness
of passive layer(mostly made up of Chromium Oxide(Cr2O3)). Passivation processes are generally controlled by industry
standards, the most popular among them today is ASTM A380, ASTM A967 and AMS 2700
Corrosion Resistant: Due to Corrosion Resistance, SS is used in Food Industry, Diary, Distillary, Chemical and Oil &
Gas Industry, Nuclear Plants, Space Research & in household utencils and hand rails, stairs, decorative frames etc. (it is
not fully stain-proof in low-oxygen, high-salinity, or when it is contaminated). SS is used for decorative and architectural
fittings. It is used on most of the oxidising environments.
Stainless steels is not affected by Citric Acid and vinegars and acids in the vegitables. From 1920, all most all kitchen
Stainless steels are not rusting and not affected by body fluids and fairly maintenance free. It has hygienic surface and so
used in surgery tools.
Stainless Steels, are member of Steel family. But, Stainless steel is corrosion and oxidation resistance, due to the
presence of Chromium, Nickel, Molybdenum etc. When the top surface of Stainless steel, is damaged (machined,
scratched, peeled off etc) or cut into two, a passive layer is immediately formed on SS surface. For forming passive layer,
the steel should have min 10.5% Chromium level and Oxygen present for oxidation.
SS, Cloud Gate, Chicago, USA
(Highly polished & shining)
SS, Atomium, representing
BCC, Iron crystal model, Brussels
SS, cladding is used on the Walt
Disney Concert Hall, LA, USA
SS, Giant Statue for Genghis Khan,
Mangolia
24

By JGC Annamalai
(1).
(2).
(1).
(2).
(3).
(4).
(B2). Galling & Jamming of Threads of SS Fasteners , moving components
(B3). Sensitization , Weld Decay, Knifeline Attack
(B4). Corrosion Attack on Stainless Steels
(B9). Contamination or Pollution on Stainless Steel Surface
(B12). Stainless Steel Weld HAZ Area is Colored or Tinted
Bright Annealing or Solution Annealing : Bright annealing (partly Solution Annealing) is heating the stainless steel to a
suitably high temperature (usually more than 1,900°F(1,040°C) in a reducing atmosphere such as dry hydrogen gas.
Organic contaminants are volatilized and most metal oxides (including those of iron, nickel, and chromium) will be reduced,
resulting in a clean, oxide-free surface. The stainless steel then is rapidly cooled (through the temperature range of 1,600
and 800°F(870 and 425°C) to prevent carbide precipitation, and then at lower temperatures exposed to air, where the
protective oxide film forms spontaneously.
Creating the Passive Film or Passive Layer : Passive layer forming is instant, when SS surface is freshly exposed, in the
presence of oxygen. Passivation is the process of retaining the shining surface and it is required when the SS surface is
contaminated. Passivation is accomplished (1). either through an appropriate Bright Annealing / Solution Annealing of the
stainless steel or (2). by subjecting the surface to an appropriate chemical treatment. In both procedures the surface is
cleaned of contaminants and the metal surface is subsequently oxidized.
Halides(Chlorine, Florine, Bromine, Iodine) will damage the passive layer and cause accelerated corrosion(like pitting).
So, avoid using them (like common salt, sea water, HCL, pickles etc. ) on SS surface.
Problems related to Stainless Steel Passivation Damage, is also discussed in Group-B Chapters:
4 to 10% citric acid plus 0.5 to 2.0% EDTA (ethylene-diamine-tetraacetic acid) at 170 °F (77°C) for one to 10 hours.
EDTA is a chelating agent that keeps iron in solution over a wide pH range. This solution is less costly, and is
considered environmentally friendly when used properly
Quick way to Test & measure Passivation : Many tests are available per ASTM A380. Most commonly used is, Copper
Sulfate Test : Sulfuric acid-Copper sulfate solution is swabbed on the surface for six minutes. The presence of any free iron
(inadequate passivation) is indicated by the deposition of red copper particles on the surface where free iron is present.
(not good for equipments, used for food processing, as copper sulfate is toxic / poisonous).
The surface should be clean and there should not be any material, masking the surface thus preventing oxygen
supply.
AWS D18.2, SS Welding Tints: When stainless steel is exposed to an oxidizing environment (air) at higher
temperatures/welding arc temperatures, say around 3000°C (or to a more highly oxidizing environment) will result in the
formation of an oxide (heat tint) of increasing thickness, ranging in color from a light straw to a dark black. The oxide layer
is mostly from Chromium oxide and it is complex in nature and it is different from Chromium Oxide passive layer
(protecting the SS suface). The thicker this heat tint oxide is, the greater the probability that corrosion will occur beneath
the oxide film.(more information on Tint Layer is found in Chapter B.12, “Tint on Welding”.
How to preserve the Stainless Steel Passivation :
For passivation to occur and for self-repair, the surface should be well airy / ventilated.
Chemical Treatment. Typical chemical treatment involves exposing the stainless steel surface to an oxidizing acid solution
in which the significant variables are (1). time, (2). temperature, and (3). Acid Concentration. Many combinations of these
variables can be used, but two of the most common are:
20% nitric acid at 70 to 120 °F(20 to 50°C) for 20 to 120 minutes. Acid concentrations up to 50% can be used.
25

Advantage of using Austinitic Statainless Steel (ASS):
Stainless Steel is selected for the following special properties:
u Higher Corrosion Resistance u Higher Ductility
u Higher Cryogenic Toughness u Higher Strength and Hardness
u Higher Work Hardening Rate u More Attractive Appearance
u Higher Hot Strength/scaling resistance @ high temp
(1). Why Stainless Steel is Shining, non rusting & corrosive resistance ? : (also refer Chapter A5)
Carbon Steel is called "Black Steel" or Mild Steel, as it is often seen, as rusty and black or dark brown rust color.
Stainless steel is normally shining and often called "Stainless".
When carbon steel and stainless steel are lathe machined, both have shining surfaces. However, carbon steel
surface is immediately oxidized ( and forms as FeO, FeO2, Fe3O4), due to oxygen, water / wet atmosphere or corrosive
environment(rain and light sea breeze etc.). Most of the Iron oxides are normally dark brown or black color.
Chapter-A6 Stainless Steel - Selection, Applications and Uses
Stainless steels is not affected by Citric Acid and vinegars and acids in the vegitables .From 1920, all most all kitchen
Stainless steels are not rusting and not affected by body fluids and fairly maintenance free. It has hygienic surface and
so used in surgery tools.
When the chromium, is equal or over 10.5%, it forms a passive
surface layer of Chromium oxide (Cr2O3) and it is dominant and it
spreads to full surface and it prevents iron to form iron oxides and
protects SS surface from corrosion.
Passive Layer: Passive layer is transparent and the thickness
is from 2 to 80 nm(nanometer), depending on the situation.
The passive layer is stable in many environments , but
damaged and SS starts corroding if oxygen is not sufficient to
form chromium oxide film or the chemical is strong and
reducing (like aquous chlorine, HCL acid or like). Corrosion
resistance is greatest when the SS is boldly exposed and the
surface is maintained free of deposits (biofouling, painting, or
gasket etc) .
SS surface is electrochemically passive. SS surface has
normally, 1 to 5 nanometres,nm, (1 to 5 x 10-9
metres)
thickness of passive layer(mostly made up of Chromium
Oxide(Cr2O3)). Passivation processes are generally controlled
by industry standards, the most popular among them today is
ASTM A 967 and AMS 2700
(a). Corrosion Resistant: Due to Corrosion Resistance, SS is
used in Food, diary, beverage etc Industry; Chemical and Oil
& Gas Industry & in household utencils and hand rails, stairs,
decorative frames etc. (it is not fully stain-proof in low-oxygen,
high-salinity, or when it is contaminated).
(2). Applications: Due to its ever shining, non-rusting surface,
SS is used for decorative and architectural fittings.
Lube-Oil Systems to machineries, like Pumps,
Compressors, Turbines, Bearings … System parts, are
often made of Stainless Steel material for its corrosion
resistance properties and to avoid, rust gathering and
scratching at the machinery bearings etc.
Stainless Steels, are member of Steel family. But, Stainless steel is corrosion and oxidation resistance, due to the
presence of Chromium. When the top surface of Stainless steel, is damaged (machined, scratched, peeled off etc) or cut
into two, a passive layer is immediately formed on SS surface. SS contains Chromium and /or Nickel, Molybdenum etc
elements for corrosion resistance. When Cr level is less than 10.5%, iron forms iron oxide on the surface and iron oxide
is dominant. Steel is corroding and forms rust on surface. Passive Layers, obtained by Thickness
, nm
Machined surfaces 2
Mechanically machined & polished surfaces 5
30 minute, passivation(with HNO3) 19
60 minute, passivation (with HNO3) 50
Higher Cr & Higher Ni, Higher Passive layer Higher
Higher O2 availability, Higher passive layer Higher
By JGC Annamalai
26

Passive Layers, obtained by Thickness
, nm
Machined surfaces 2
By JGC Annamalai
(e). Material Selection, for High Temperature Service:
(d). Full annealed Austenitic SS is easy to form and
Weld:
Stainless Steel, Max. Service Temperatures
The temperature given here are based on scale
and oxidation resistance point of view.
For high temperature corrosion service, stainless
steel selection should also be based on
sensitization temperature range.
(b). It is stronger than CS:
(c). No Phase Change: Unlike carbon and low alloy steels the austenitic stainless steels undergo no big phase changes
as they cool from melting temperatures. Welding and Heat Treatment do not increase hardness. Cold (hydrogen
induced) cracking is therefore not a problem and preheat for welding is not necessary, irrespective of component
thickness. Strength and hardness cannot be improved by Heat Treatment. Cold work on Aus SS can give higher
strength and hardness . For limited distortion control, PWHT can be conducted below 400°C. Over 400°C , sensitization
occurs, so PWHT is not followed.
The mechanical tensile strength, yield strength are more than CS. Where-ever, weight ratio of SS to CS is lesser and
preferred, SS is used, like airplane structures.
Annealed Aus SS has 40% elangation and easy to form.
It can be welded by most of the welding processes.
Stainless steel is scale resistance upto 1000°C, wheras
scales are found on CS around 600°C. So, SS is used in
boiler, heaters, flare stack supports and similar
applications.
Selection of material, for high temperature service is
mainly based on their stability at high temperatures.
Main properties for High Temperature Usage selection
are :
(1). Their stability at the higher temeperatures
(2). Their resistance to oxidation resistance
(3). Their resistance to scale formation.
(4). Resistance to High Temperature Corrosion due to
burning of the combustion gases and flare gases
For moderate temperatures, Boiler Drums are made up
of Carbon Steel. As the temperature increases, low
alloy chromium-molibdenum alloy are used. Super
heater tubes are made up Cr-Mo steels, stainless
steels. Often Flare tips & Furnace Burner Tips are made
up of Stainless Steels 310 and 309 and Inconel 600,
625, Incoloy 800, to resist high temperature oxidation,
scalling and corrosion.
27

, nm
Machined surfaces 2
By JGC Annamalai
SS HEAT TREATMENTS :
Ferritic SS, like SS-430,Heat Treatments
Anneal: Heat to 1400 – 1525 °F (760 – 829 °C), air cool or water quench
Martensitic SS, like SS-410, Heat Treatments
Annealing: Heat slowly to 1500 – 1650 °F (816 – 899 °C), cool to 1100 °F (593 °C) in furnace, air cool.
Process Annealing: Heat to 1350 – 1450 °F (732 – 788 °C), air cool.
Hardening: Heat to 1700 – 1850 °F (927 – 1010 °C), air cool or oil quench. Follow by stress-relief or temper.
Stress Relieving: Heat at 300 – 800 °F (149 – 427 °C) for 1 to 2 hours, air cool.
Tempering: Heat to 1100 – 1400 °F (593 – 760 °C) for 1 to 4 hours, air cool
Austenitic SS, like SS-304, Heat Treatments
(A). Type 304 is not hardenable by heat treatment. So, heat treatment is not recommended.
(1).
(2).
(3). Hold at 800°F±25°F(427°C±14°C) for 2 hr.
(4).
(5). Hold at 1925°F±25°F(1052°C±14°C) for 1 hr.
(6). Air cool
Heat from room temperature to 600°F(316°C),
uncontrolled heating.
Heat from 600°F to 800°F(316°C to 427°C) at a
max. rate of 300°F(167°C) per hr.
Heat from 800°F to 1925°F(427°C to 1052°C) at
a max.rate of 600°F(333°C) per hr.
The following PWHT procedure was followed on welded
joints :
(g). Material Selection, High/ultra high Vacuum Service:
SS material has favorable degassing qualities(prevents permeation of air/gas through SS material) and used for ultra
high vacuum services. It is used in Nuclear field due to its, high corrosion resistance and high strength. Radition has
little effect on Impact Strength and Ductility. (Due to irradiation, Carbon steel, losses impact strength and effect: it
becomes brittle.)Most of the carbon steels, alloy steels are found leaking(de-gassing) through the grains and fails to
maintain the high vacuum (>10-6
torr). The SS grains are compact and they are resistant to de-gassing at ultra high
vacuum (>10-6
torr).
(B). On sensitized SS, if stainless steel is used in corrosive service, Solution Annealing: Heat to 1900 – 2050 °F (1038 –
1121 °C), then cool rapidly. Thin strip sections may be air cooled, but heavy sections should be water quenched to
minimize exposure in the carbide precipitation region.
(C). Some users like, Super Critical thermal power plant, use SS316L for tubes and headers in superheaters. They
follow solution annealing on shop and field welded joints : heating to 1050°C, hold for min 1 hour , cool in still air. The
service is pure steam (pressure-5325 psig (36.7 MPa) and temperature, 1210°F(655°C)) and no corrosive material with
steam. Sensitization is tolerated. Min.Life 100,000 hr.
Due to its exceptional toughness qualities, it is used in Cryo
Services. High Chromium - high nickel SS makes them, as
oxidation resistance and used in high temperature furnace &
flare services. Aus SS is face centered and has high impact
strength, at low and cryo temperatures, so, SS is used for
components in low and cryo temperature services. SS
components absorb more impact energy and they are ductile
at cryo temperatures and during accidents, the damages are
not severe, comparing to similar CS components and low
impact materials.
Martensitic SS are not good for low and cryogenic temp <25°C
Ferritic SS are not good for low and cryogenic temp <-20°C
Duplex SS are not good for low and cryogenic temp <-20°C
(f). Material Selection, for Low Temperature & Cryogenic
Temperature Service:
28

, nm
Machined surfaces 2
By JGC Annamalai
Some Important Charts, relevant to Stainless Steels Selection:
(E) If stainless steel (including sensitized Stainless steel) is not used in corrosive service, stress relieving between 425
to 950°C can be used, to (a).stress relieve, (b). remove magnetism and (c). to soften the material. .
Internal and external thermocouples were installed on one joint to determine the temperature differential between the
inside and outside walls. The max. difference is 60°F(33°C). The gap closed as the temperature approached the holdng
range.
(D). Stress Relief Annealing: Cold worked parts should be stress relieved at 750 °F (400°C) for 1/2 to 2 hours
Set-up: All grith (C-seam) welds were stress relieved after welding. An argon purge was maintained on the pipe
interior during the heat treating operations. The heat treating was performed using induction heating with water-cooled
flexible copper coils. Eight loop, single layer were wrapped around the outside of the weld. The induction frequency was
800 Hz.
29

DIN
Strength
limit
(MPa)
Yield
strength
(MPa)
Elon'n
50mm
(%)
Rockwell
-
B
Cold
bending
Erichsen
cup
test(mm)
Formability
Weldability
Corrosion
Density
(g/cm
3
)
Spe.
Heat
0-100
°C
(J/Kg.K)
Coeff.
of
thermal
Expansion
(μ/m
°C)
Melting
Range
(°C)
Magnetism
Elec.
Resist.
at
Room
Temp.
Heat
Cond.
100
°C
(w/m.K)
Modulus
of
Elasticity
Modulus
of
Rigidity(G
201LN S20153 1.4376 0.03
'6.40-
7.50
0.20-
0.60
0.05 0.015
17.0-
17.5
4.0-4.5 -
0.15-
0.25
700 500 45 95 - - Good Excellent Fair 7.8 500 17.1
1400 -
1450
Annealed.
non-magnetic
690 16.2 197 86.2
201 S20100 1.4618 0.15
'5.50-
7.50
1 0.06 0.03
16.0-
18.0
3.5-5.5 - 0.25 515 260 40 - - - Good Excellent Fair 7.8 500 17.1
1400 -
1450
Annealed.
non-magnetic
690 16.2 197 86.2
301 S30100 1.4310 0.05 2 1
0.045
0.015
16.0-
18.0
6.0-8.0 - 0.1 - 910 320 46 86 180° 13 Better Better Fair 8 500 17.5
1400 -
1420
Annealed.
non-magnetic
720 16.2 193 86.2
301LN S30153 - 0.03 2 1 0.05 0.03
16.0-
18.0
6.0-8.0 -
0.07-
0.20
700 400 50 90 180º - Good Excellent Fair 8 500 17.5
1400 -
1425
Annealed.
non-magnetic
720 16.2 193 86.2
304 (1) S30400 1.4301 0.07 2 0.75
0.045
0.015
17.5-
19.5
8.0-
10.5
- 0.1 c 720 320 57 84 180° 12 Better Better Good 8 500 17.8
1400 -
1450
Annealed.
non-magnetic
720 16.2 193 86.2
304L S30403 1.4307 0.03 2 0.75
0.045
0.015
17.5-
19.5
8.0-
10.5
- 0.1 - 690 320 51 80 180° 12 Better Excellent Good 8 500 17.8
1400 -
1450
Annealed.
non-magnetic
720 16.2 193 86.2
304T S30400 1.4301 0.03 2 0.75 0.05 0.015
17.5-
19.5
9.0-
10.5
- 0.1 610 280 58 74 180º 12 Excellent Excellent Good 8 500 17.8
1400 -
1450
Annealed.
non-magnetic
720 16.2 196 86.2
304 (2) S30400 1.4301 0.07 2 0.75 0.05 0.015
17.5-
19.5
8.0-
10.5
- 0.1 600 280 58 75 180º 12 Excellent Better Good 8 500 17.8
1400 -
1450
Annealed.
non-magnetic
720 16.2 196 86.2
304H S30409 -
0.04-
0.10
2 0.75 0.05 0.03
18.0-
20.0
8.0-
10.5
- - 710 320 58 83 180º - Better Better Good 8 500 17.8
1400 -
1450
Annealed.
non-magnetic
720 16.2 193 86.2
316 S31600 1.4401 0.07 2 0.75
0.045
0.015
16.5-
18.0
10.0-
13.0
2.00-
2.5
0.1 - 650 340 51 82 180° 12 Better Better Better 8 500 16.5
1375 -
1400
Annealed.
non-magnetic
740 16.2 193 86.2
316L S31603 1.4404 0.03 2 0.75
0.045
0.015
16.5-
18.0
10.0-
13.0
2.00-
2.5
0.1 - 650 340 51 82 180° 12 Better Excellent Better 8 500 16.5
1375 -
1400
Annealed.
non-magnetic
740 16.2 193 86.2
317L S31703 - 0.03 2 0.75 0.05 0.03
18.0-
20.0
11.0-
15.0
3.0-4.0 0.1 650 330 45 87 180º - - Excellent Better 8 500 17.5
1375 -
1400
Annealed.
non-magnetic
790 14.4 200 86.2
310S/H S31008 1.4845
0.035-
0.08
2 1.5 0.05 0.015
24.0-
26.0
19.0-
22.0
- - 600 380 42 83 180º - - Good Better 8 500 16.5
1400 -
1450
Annealed.
non-magnetic
780 14.2 200 86.2
321 S32100 1.4541 0.08 2 0.75
0.045
0.015
17.0-
19.0
9.0-
12.0
- 0.1 5(C+N)<Ti<0.70 670 260 42 78 180° 12 - Excellent Good 8 500 17.5
1400 -
1425
Annealed.
non-magnetic
720 16.1 193 86.2
347/H S34709 -
0.04-
0.08
2 0.75 0.05 0.03
17.0-
19.0
9.0-
13.0
- 0.02
Nb = 10 C min1.00
máx.
645 345 51 87 180º - - Better Good 8 500 17.5
1400 -
1425
Annealed.
non-magnetic
730 16.1 193 86.2
- - 1.4003 0.03 1.5 1 0.04 0.015
10.5-
12.5
1 - 0.03 475 280 30 80 180° - - Good Poor 7.8 460 11
1480 -
1530
Magnetic 570 24.9 200
409 S40910 1.4512 0.03 1 1 0.04 0.015
10.50-
11.7
0.5 - 0.03
6(C+N) < Ti < 0.50;
Nb = 0.17 máx.
420 250 40 67 180° 10 Better Good Poor 7.8 - 11.7
1480 -
1530
Magnetic - - - -
409 S40920 14512 0.03 1 1 0.04 0.015
10.50-
11.7
0.5 - 0.03
10 (C+N)<Ti<0.50;
Nb=0.17max
410 245 40 67 180° 10 Better Good Poor 7.8 - 11.7
1480 -
1530
Magnetic - - - -
430 S43000 1.4016 0.08 1 1 0.04 0.015
16.0-
18.0
0.75 - - - 520 350 30 81 180° 9 Fair Fair Fair 7.8 460 10.9
1425 -
1510
Magnetic 600 26.1 200 86.2
- S43000 1.4016 0.08 1 1 0.04 0.015
16.0-
18.0
0.75 - - Nb = 0.60 máx. 480 330 31 79 180° 10 Better Good Fair 7.8 460 10.9
1425 -
1510
Magnetic 600 26.1 200 86.2
- S43932 - 0.03 1 1 0.04 0.015
17.0-
19.0
0.5 - 0.03
0.20 + 4(C + N) < Ti
+ Nb<0.75 Al =0.15
AI máx
460 305 34 76 180° 10 Better Good Fair 7.8 460 10.9 - Magnetic 630 24.2 200 86.2
- - 1.4509 0.03 1 1 0.04 0.015
17.5-
18.5
0.5 - 0.03
3C + 0.30 < Nb
<1.00; Ti = 0.10 a
0.60
460 295 35 77 180° 10 Better Good Fair - - - - Magnetic - - - -
- S44400 1.4521 0.025 1 1 0.04 0.03
17.5-
18.5
1
1.75-
2.50
0.035
0.20 + 4(C + N) < Ti
+ Nb<0.80
520 350 31 83 180° 9 Good Good Better 7.8 420 10.7 - Magnetic 620 26.8 200 86.2
410 S41000 1.4006
.08-
0.15
1 1 0.04 0.03
11.5-
13.5
0.75 65000 30000 20 80 Good Fair Fair 7.74 460 10.9
1450 -
1510
Magnetic 550 24.9 200 81
420 S42000 1.4028
0.15
min
1 1 0.04 0.03
12.0-
14.0
0.75 0.5 - - 620 370 26 87 - - - Poor Poor 7.8 460 10.9
1450 -
1510
Magnetic 550 24.9 200 81
- - 1.4116
0.45-
0.55
1 1 0.04 0.015
14.0-
14.5
-
0.50-
0.80
- V = 0.1 a 0.2 - - - 100 - - - Poor Poor 7.8 Magnetic
Dupl
ex
SS
- S32304 1.4362 0.03 2 1 0.04 0.015
22.0-
24.0
3.50-
5.50
0.10-
0.60
0.05 a
0.20
Cu = 0.10 a 0.60 740 560 30 96 - - - Good Better 7.8 450 13.5 1465 Magnetic 800 17 200 86.2
-
S32205/
S31803
1.4462 0.03 2 1 0.03 0.015
22.0-
23.0
4.50-
6.50
3.00-
3.50
0.14-
0.20
- 840 660 27 98 - - Good
Excell
ent
7.8 460 14.3
1460 -
1465
Magnetic 800 16 200 86.2
SSC
6Mo
S31254 1.4547 <0.02 1 0.70 0.30 0.010 20 18 6.1 0.2 Cu0.75 675 310 35 90 Difficult
Excell
ent
8.2 500 15.3
1354-
1404
890 11.8 196
PH
PH-17.4 S17400 0.07 1 1 0.04 0.03 17 4 Cu4,Nb&Ta0.3 1319 1170 5min 108-
116
Hard Fair Good 7.8 460 10.4 1400-
1450
Magnetic 800 17.9 197 70
Austenitic
Stainless
Steel
Ferritic
SS
ASTM
Mart.
SS
SS Mechanical Properties Service & Fabrication
SS
Group
SS Chemical Composition
SS Applications-1 30

SS AISI UNS DIN Stainless Steel Applications, Uses
201LN S20153 1.438 Structural applications.
201 S20100 1.462
Sinks and bowls, forks and knives, washing-machine baskets, dishwashers cabinets, stove tops, external covering of fridges, pipes for the furniture-making industry, internal parts of
facades in civil construction, wall covering for elevators, industrial restaurants and kitchens, evaporators pipes, boilers of sugar plants, evaporators casing, boilers and other equipments and
mirrors of sugar plants.
301 S30100 1.431
Used for structural purposes on equipment intended for the food processing, aeronautical, railway and oil industries; for manufacturing of knives and blades, sinks and bowls, friezes; for
boilerwork and general drawing and deep-drawing applications.
301LN S30153 - Railway industry: trains and subway carriages for transportation of passengers.
304 S30400 1.43
Civil construction and architecture; equipment intended for the industries: aeronautical, railway, shipbuilding, petrochemical, pulp and paper, textile, cold-store/refrigeration, hospital, food
processing, dairy, pharmaceutical, cosmetic, chemical; household utensils, cryogenic installations, distilleries, ethanol distilleries, photography, pipes and tanks in general, general drawing,
deep-drawing and precision drawing applications.
304L S30403 1.431
Equipment intended for the industries: aeronautical, railway, shipbuilding, petrochemical, pulp and paper, textile, cold-store/refrigeration, hospital, food processing, dairy, pharmaceutical,
cosmetic, chemical; household utensils, cryogenic installations, distilleries, photography, pipes and tanks in general, general drawing and deep-drawing applications.
304T S30400 1.43
cosmetic, chemical; household utensils, cryogenic installations, distilleries, photography, pipes and tanks in general, general drawing, deep-drawing and precision drawing applications.
304 S30400 1.43
cosmetic, chemical; household utensils, cryogenic installations, distilleries, photography, pipes and tanks in general, general drawing, deep-drawing and precision drawing applications.
304H S30409 -
Equipment intended for the industries: petrochemical, pulp and paper, textile, cold-store/refrigeration, hospital, food processing, dairy, pharmaceutical, cosmetic, chemical; cryogenic
installations, distilleries, photography, pipes and tanks in general. Equipment requiring greater resistance under high-temperature conditions, in addition to stricter requirements relative to
weldability.
316 S31600 1.44
Civil construction and architecture; equipment intended for the industries: aeronautical, railway, shipbuilding, chemical and petrochemical, pharmaceutical, cosmetic, textile, rubber, paints,
dairy, hospital; mining and steelmaking; refrigeration, refineries, manufacturing of pipes and pressure vessels, alcohol distilleries, ethanol distilleries and boilerwork.
316L S31603 1.44
Civil construction and architecture; equipment intended for the industries: aeronautical, railway, shipbuilding, chemical and petrochemical, pharmaceutical, cosmetic, textile, rubber, paints,
dairy, hospital; mining and steelmaking; refrigeration, refineries, manufacturing of pipes and pressure vessels, alcohol distilleries, ethanol distilleries and boilerwork.
317L S31703 - Chemical/petrochemical industries and pulp/paper manufacturing industries; such as capacitors for electric-power generating stations based on fossil and nuclear fuels.
310S/H S31008 1.485
Heat treatment industry for furnace parts, such as anchoring for refractory materials, parts of burners, belt conveyors, furnace lining, fans and pipe hooks, etc. For the food-processing
industry, they are used in contact with heated citric and acetic acids.
321 S32100 1.454 Thermo-resistant components for the electric industry, welded components, food-processing industry, pipes and tanks in general.
347/H S34709 -
Equipment for aeronautical industry, such as slip rings of turbines and exhaust systems, expansion joints and also for equipment intended for high-temperature chemical processes. It is
also applied to the oilindustry, particularly during refinement, in a form of pipes, fittings and flat plates.
- - 1.4
Transports: railway carriages, wagons, busses; alcohol and sugar plants: bagasse collectors, sides of feeding tables, floor and sides of intermediary tables, sugarcane conveyors, Shut
Donelly, diffusers, juice collectors; buildings, urban furniture, beams and girders for bridges, etc.
409 S40910 1.451 Gas exhaust systems for combustion engines and stamping in general, in addition to capacitors boxes.
409 S40920 14512 Gas exhaust systems for combustion engines and stamping in general, in addition to capacitors boxes.
430 S43000 1.402
Civil construction and architecture; household utensils (serving trays, sinks and cutlery), electrical appliances (stoves, fridges, microwave ovens and washing machines), minting and
stamping of coins, coun-ters incorporating a refrigerating unit, and stamping in general.
- S43000 1.402 Household utensils (serving trays, sinks and cutlery), minting and stamping of coins, counters incorporating a refrigerating unit, general stamping and deep drawing.
- S43932 - Civil construction and architecture: sugar plants, exhaust systems (exhaust pipe mufflers), electrical appliances (washing machines, stoves and microwave ovens) and stamping in general.
- - 1.451 Exhaust systems (pipes and flat), stamping (catalyst unit casing, exhaust pipe mufflers, etc).
- S44400 1.452 Civil construction and architecture: sugar plants, water tanks, household water heaters, applications in chemical and petrochemical industries.
420 S42000
1.4028
Cutlery, measurement instruments, hospital, odontological and surgical instruments; mining and steelmaking applications, in addition to cutting blades and brake discs, knives, blades and
chains for bottle washing machines.
- - 1.412 Professional cutlery (cold stores, slaughterhouses and butchery).
- S32304 1.436
Digesters for paper and pulp industries, chemical and petrochemical industries, bridges and viaducts, heat exchangers and pipes for handling oil and gas, storage tanks, cargo tanks for
ships and cargo compartments for trucks, sea water systems, food-processing equipment.
-
S32205/
S31803
1.446
Digesters for paper and pulp industries, chemical and petrochemical industries, bridges and viaducts, heat exchangers and pipes for handling oil and gas, storage tanks, cargo tanks for
ships and cargo compartments for trucks, sea water systems, food-processing equipment.
PH
PH17.4 S17400 Applications for PH steels include aerospace components, flat springs, and retaining rings.
Ferritic
Stainless
Steel
Marten.
SS
Duplex
SS
Austenitic
Stainless
Steel
SS Applications-2 31

SS Grade Description Applications
201 High work hardening rate; low-nickel equivalent of type 301
202 Low nickel, high Mn General purpose low-nickel equivalent of type 302
205
Lower work-hardening rate than Type
202.
301 High work hardening rate;
302 High in Carbon than SS304 Higher strength
303S
Free machining, good mechanical and
corrosion resistant properties
Mechanical and pharmaceutical components and parts
304/304L/304H
General Purpose Chemical equipment, Pressure vessels, Cryogenic
vessels, Dairy equipment, Nuclear vessels and
components
316L
Mo added to increase corrosion
resistance
Chemical processing equipment, Food processing
equipment, Oil refining equipment, Paper industry
digesters, evaporators & handling equipment
317L/317LMN
More Mo and Cr added for better
corrosion performance
Chemical processing equipment, Dying equipment,
Pulp and paper manufacturing equipment;
Desalination equipment
321/321H
Ti added to prevent carbicle precipitation Plate heat exchangers, Chemical equipment, Fire walls,
Pressure tanks
347/347H
Stabilized, excellent resistance to
intergranular corrosion at elevated
temperatures
Radiant heaters, Aerospace components, Oil refining
equipment
309S
Cr and Ni increased for high temperature Annealing boxes, Chemical processing equipment
(elevated temperature), Conveyor parts, Dryers
310S
Same as 309, only more so Annealing boxes, Chemical processing equipment
(elevated temperature), Conveyor parts, Dryers
3Cr 12(1.4003)
430(1.4016)
410S
410 General Purpose Press plates, Coal chutes, Oil burner parts
410S
Restricted carbon modification that
prevents hardening and cracking when
exposed to high temperatures or welding
Petroleum refining, petrochemical processing, ore
processing, thermal processing, gate valves, press
plates
LDX 2101
General purpose lean duplex possessing
both superior strength and corrosion
resistance comparable to 304L and 316L
Air pollution control, biofuels, chemical processing,
food and beverage processing, infrastructure, pulp and
paper, desalination and water and wastewater
treatment
2304
Improved strength and stress corrosion
cracking compared to 304/316
Pulp & paper, Tanks, Digesters, Pharmaceutical, Food
industry
2205
High strength and superior corrosion
resistance
Pressure vessels, Tanks, Piping, Scrubber systems,
Digesters, Heat exchangers
2507
Exceptional strength and corrosion
resistance
Oil and gas equipment, Heat exchangers, Chemical
processing vessels, Desalination
Air pollution control, chemical processing, food and
beverage processing, ore processing, offshore oil and
gas production, petroleum refining, pharmaceutical
processing, power
generation, pulp and paper, desalination
PH
SS
17-4PH
Capable of precipitation hardening Aerospace, Pulp and paper, Valves, Fittings, Food
industry, Nuclear waste casks
Martensitic
SS
Duplex
SS
SSC-6MO
6% molybdenum superaustenitic alloy
with outstanding resistance to chloride
pitting, crevice corrosion and stress-
corrosion cracking.
Cost wise cheaper than SS304. Used as structure,
replacing SS304 and Duplex SS.
Ferritic
Austenitic
SS
SS Applications-3
32

Compare SS202 and SS304
Chemical Composion of SS202 and SS301 Ref: ASTM A240
Comparing to SS304 and SS202, Carbon, Manganese, Phosphorus, Silicon are reduced, in SS304.
Mechanical Properties of SS202 and SS304
Comparing to SS304 and SS202, tensile, yield strength and hardness are less in SS304.
In 2007-2008, most of Stainless Steel foundries were either
shut down or they were facing long delay. The reason is
Nickel was in short supply. The spot Nickel price had gone
high, 4 to 6 times.
Foundries were pressing the Users. Suppliers recommended
to use SS202 instead of SS304, as the nickel content in
SS202 was partially replaced by Manganese. The price of SS
was cheaper. Vendors claimed, SS202 was almost having
equivalent corrosion resistance and mechanical properties,
much above SS304.
Users with Project Specifications, did not accept to change
from SS304 to SS202. They insisted to follow Specification
and to use SS304
However, people making products, direct sales to people, like
utencils, architectural and decoration items, gift items,
ladders, stairs etc changed to SS202, instead of SS304.
Many shops branded the SS202 articles as SS304. There is
no easy way to check whether it is SS202 or SS304. To
check the chemisty of SS202 articles, we need to use
Spectrometer or portable X-ray fluorescence meters. Their
prices are exorbitant to Fabrication Shops or to the Sales
Shops or to the users.
SS202 series and SS300 series are Austenitic Stainless
Steels. To make the steel Austenitic, Austenitic formers, like
Nickel, Manganese, Copper, Nitrogen, Carbon are added.
During World War-II time, Nickel was in short supply.
Suppliers managed to maintain the Austenitic Sturcture, by
adding Manganese, Copper and Nitrogen. That time, there
was no controlling ASTM Specification, on Cr-Mn Austenitic
Stainless Steels. Such practice was continued.
ASM has listed the equivalents of SS200 series and SS300
series. In 1955, ASTM adopted SS201 and SS202 and
recognised. But other than SS201 and SS202, remaining
were not listed/not recognized by AISI / ASTM, till 2015.
Chapter-A7 SS200 series Stainless Steel, Alternative to SS300 series ?
Referring to the Property Table, in the following page and the
charts, shown here, we will find the SS202 has shining
surface, corrosion resistance, welding, mechanical properties
are generally equal or exceeds SS304.
The price of SS304 is roughly 1.5 times the price of SS202
Welding: SS304 has max.0.07%C and SS202 has
max.0.15%C. Cracking and sensitization are expected on
SS202 due to excess Carbon & Phosphorus.
Advise : Avoid welding on SS202
Recommendations: Avoid SS201 or 202, on jobs involving excessive or repeated bending or deep drawing/ stretching.
Compare Carbon,
%
Phosphorus,
%
Hardness,
Brinnel
Stretch,
%
Elangation,
in 2"
By JGC Annamalai
M
M
3
6
H
H
UNS Type Elongation Cold Bend
ksi MPa ksi MPa 2"(50 mm) Brinnel Rockwell-B
min%
S20100 201 75 515 38 260 40 217 95 . . .
S20200 202 90 620 38 260 40 241 . . . . . .
S30400 304 75 515 30 205 40 201 92 not required
S31600 316 75 515 30 205 40 217 95 not required
Hardness, max
Tensile Strength, min Yield Strength,B min
UNS Type Carbon Manganese Phosphorus Sulfur Silicon Chromium Nickel Molybdenum Nitrogen Copper Other
S20100 201 0.15 5.5–7.5 0.060 0.030 1.00 16.0–18.0 3.5–5.5 . . . 0.25 . . . . . .
S20200 202 0.15 7.5–10.0 0.060 0.030 1.00 17.0–19.0 4.0–6.0 . . . 0.25 . . . . . .
S30400 304 0.08 2.00 0.045 0.030 0.75 18.0–20.0 8.0–10.5 . . . 0.10 . . . . . .
S31600 316 0.08 2.00 0.045 0.030 0.75 16.0–18.0 10.0–14.0 2.00–3.00 0.10 . . . . . .
33

Chapter-A7 SS200 series Stainless Steel, Alternative to SS300 series ?
Compare Carbon,
%
Phosphorus,
%
Hardness,
Brinnel
Stretch,
%
Elangation,
in 2"
SS304 0.08 0.045 201 40 1.07"
By JGC Annamalai
M
M
3
6
H
H
UNS Type Elongation Cold Bend
ksi MPa ksi MPa 2"(50 mm) Brinnel Rockwell-B
min%
S20100 201 75 515 38 260 40 217 95 . . .
S20200 202 90 620 38 260 40 241 . . . . . .
S30400 304 75 515 30 205 40 201 92 not required
S31600 316 75 515 30 205 40 217 95 not required
Hardness, max
Tensile Strength, min Yield Strength,B min
UNS Type Carbon Manganese Phosphorus Sulfur Silicon Chromium Nickel Molybdenum Nitrogen Copper Other
S20100 201 0.15 5.5–7.5 0.060 0.030 1.00 16.0–18.0 3.5–5.5 . . . 0.25 . . . . . .
S20200 202 0.15 7.5–10.0 0.060 0.030 1.00 17.0–19.0 4.0–6.0 . . . 0.25 . . . . . .
S30400 304 0.08 2.00 0.045 0.030 0.75 18.0–20.0 8.0–10.5 . . . 0.10 . . . . . .
S31600 316 0.08 2.00 0.045 0.030 0.75 16.0–18.0 10.0–14.0 2.00–3.00 0.10 . . . . . .
Cracked Caps due to repeated press work: k
Remedy:
(4). Between Stages, Solution annealing(@1050°C) or stress relieving (≤400°C) can increase the ductility.
Product-Household utensil caps
Reject-Many Cracks on the rim
Cause-The material is SS202, Repeated pressing, spinning,
flanging had work hardened the caps and raised the residual
stresses. Cracks at the fab shop or Sales Shop is not known.
Delayed cracks happened at the user's premises
Stainless: Corrosion: Comparing to SS304, High passivity
causing elements, like Chromium, Nickel are less in SS202,
so SS202 articles may corrode sooner than SS304.
(please refer to Chapter B1. Cold Work on SS, for more details)
Fabricability (press brake, cold rolling, pressing, deep
drawing, flanging, spinning, wire drawing etc). SS202,
Carbon, Phosphorus, Silicon are in excess of SS304. They
cause high hardness & low ductility . Stainless steel is
hardenable, by cold work. High hardness, low ductility, high
residual stresses by repeated pressing/ work hardening
operations, will cause cracks. Residual stresses may be just
below max. tensile stress. So,the products do not crack at the
Production or Sales Shops and wait for the time to crack, say
at the users. They have delayed cracking. So, SS201/202 are
good for cutting, welding, assembly jobs and not good for
streching / deep drawing jobs.
As SS201/202 are shining. Fabricators use SS2xx as duplicate
for SS304. SS201/202 are less ductile comparing to SS304
To get the shape, the following pressing operations are carried
out. Deep Drawing, (2). Flanging, (3). Spinning.
(1). Lubricaiton: These operations need lubrication during the
pressing opeartions, as the product need high degree of surface
quality. Stainless steel has higher strength than CS, lower
thermal conductivity, higher co-efficient of friction. During cold
pressing/ drawing operation, work hardening and temperature
rise are expected to increase and galling and spalling are to
happen. So, lubricaiton is necessary during all pressing
operations. Graphite or molybdenum disulfide or chlorinated oils
or waxes can be used. Need cleaning the object immediately.
(2). Slow Strain rate/slow work(hydraulic pressing) should be
used..
(3). As SS202 has low ductility and low stretch limit, SS304 is preferred
Advise: Avoid SS202, using in the sensitizing
temperature range(450 to 850°C).
Press Work: Element to produce ductility is Nickel and
Nickel is less in SS202, comparing to SS304. Hardness of
SS202 is around 240 Brinnel, and for SS304, hardness is
around 200 Brinnel. SS202 is brittle comparing to SS304.
Stretching, for SS202 is about 50% SS304.
Advise : Avoid repeated press work and stretching or deep
drawing on SS202.
Heat : The carbon is around 0.15% and high. If the SS202
is heated in the sensitization zone(450 to 850°C), the
material will be sensitized and corroion happens / blackened.
Compare Carbon,
%
Phosphorus,
%
Hardness,
Brinnel
Stretch,
%
Elangation,
in 2"
SS304 0.08 0.045 201 40 1.07"
SS201 0.15 0.06 241 25 0.92"
34

Industry / Application requiring highly polished Stainless Steel: High degree of polish is required
The term “polished” defines a range of finishes which generally are of two types, either:
(a) Satin or Grained. Satin finish in stainless steel. It is less glossy than
a polished surface, with a unidirectional (linear grained) brushed finish having
transverse Ra of about 0.5 microns. Satin Polished stainless steel is practical
in use, widely available, relatively low cost and the most commonly used.
the surface for 5-10 minutes to create a mirror-like, highly reflective finish. A benefit of No. 8 Mirror finishing is that it
improves corrosion resistance. Polishing improves appearance and consistency, make cleaning easier and aids
practicality to fabricate and repair/ blend after welding and to mask minor damage.
(b) Brightened and Mirror Polished. Mirror finishes are highly reflective and
created by polishing the stainless steel. ... The final process involves buffing
Surface Finish : related terms, Roughness, Smoothness, Polished Surface
Surface Finish is important to the function of many kinds of industrial products ranging from optics to highways. Surface
roughness is a measure of the texture of a surface. Ra, is the Roughness (Average), unit is normally, µm or µinch
Stainless steel products are available in Mill finishes either cold finished or hot finished. Further processing is done for the
demanding architectural and aesthetic applications. More popular mill delivery finishes are 1D(1.5 to 7.5µm), 2D(0.4 to
1.0µm), 2B(0.1 to 0.5µm) and 2R(.05 to 0.1µm)
Why high degree of Polish is required: If the surface is rough, (a). sediments, products, dust etc will lodge/deposit on
the voids or on the shadow surfaces (of vessels, pipes etc) and start corroding (there is no oxygen for self-repairing the
damaged passive layer). (b). The deposit may decay and contaminate the product. (c). Cleaning is difficult.
(4). For maximum shining / reflection, for best aesthetic appearance, to have less
friction, to meet sanitation standards, we should have high polish, less than Ra<0.5
(3). For surgical and operation theater tools and instruments, require high polished
SS surfaces, to reduce the carry over of foreign material into the human body. SS
high polished duplicate human body parts are also embeded/implanted into the
human body for the same reason.
(2). Pharmaceutical, Fermentation, Biochemical, Food & Beverages, Surgical tools,
Dairy & Semiconductor industries etc requires high polish for the reason, given in
(1). above.
Chapter-A8 Stainless Steel Surface Finish
To achieve, Ra<0.5 µm. In practice, Ra<0.5 µm, level of roughness could most
easily be achieved by using 240 grit silicon carbide polishing belts rather than aluminium oxide abrasives
Cloth or Fiber (with abrasive paste) buffing will be used to increase the polish(Ra<0.05 µm) and to get the mirror finish.
The following machining will give,
(a). Ra, 0.5 to 0.05 µm: (1). Electro-chemical treating, (2). Barrel finishing,
(3). Electrolytic grinding, (4). Roller Burnishing.
(b). Ra<0.05 µm (1). Grinding, (2). Honing, (3). Electro polishing, (4).
Polishing, (5). Lapping, (6). Superfinishing
By JGC Annamalai
Canopy, Visitors Hall of an Office in Brussels, are
fully decorated with polished stainless steel sheets.
A metro station in Paris, uses, polished stainless steel
sheets extensively for the floor, office space etc.
35

By JGC Annamalai
Surface Finish/Roughness, Definitions:
ANSI B46.1: ANSI gives roughness achieveble by various workshop machines and processes.
1µm=40µinch
0.5µm=20µinch
RMS, is the root mean square, of the roughness
heights, over a length or an area, unit, µm
Ra, is the Arithmetic Average of Roughness Heights,
over a length, unit, µm. Also called, AA is Arithmetical
Average
36
The
following
machining
will
give,
Ra<0.5
µm:
(1).
Electro-
chemical
treating,
(2).
Barrel
finishing,
(3).
Electrolytic
grinding,
(4).
Roller
Burnishing,
(5).
Grinding,
(6).
Honing,
(7).
Electro
polishing,
(8).
Polishing,
(9).
Lapping,
(10).
Superfinishing

By JGC Annamalai
Scanning electron microscope provides the highest resolution direct images of solid surfaces (10 nm)
Roughness Measurements: Roughness is measured, by various methods, most common is comparators, Stylus
traction, Surface reflection / diffraction methods. The symbol is Ra(Roughness Average), in µ inch(µin) or in µ meter(µm).
Ra is also called AA(Arithmetic Average)
High Polish Machining :
General Machining :
Mechanical Finishes :
Surface Roughness(Ra) comparison :
(1). Comparators:
Most of the manufacturing
work shop / factories have
Roughness Comparators for
comparing the job finish to
standard surface finish.
(2). Stylus : Surface
roughness measurement
using Stylus on the job
surface is done. Permanent
record of the surface
roughness is available.
(3). Interferometer: Light rays
are projected on the standard
reference surface and the job
surface. The data from both
sample and job are recorded
and for study.
(4). Scanning Electron
Microscope: It provides the
highest resolution direct
images of solid surfaces (10
nm). Roughness height is not
measureable.
Steel Surface Roughness
Steel Surface Measurement by Stylus
Roughness Comparators
Steel Surface Roughness
Measurement by Interferometer
① ② ③
Surface Roughness Measurement, ANSI B46.1


37
Finish:
Ra
0.5
µm
or
less
required
bySanitation
standards.
Comparing
the
surface
finishes
obtainable
using
different
machine
tools,
surface
finish
N5
or
less
is
possible,
mosty
on
lapping
and
on
grinding.
Milling,
and
lathe
turning
gives
the
N5
or
less
finishes,
on
exceptional
cases

By JGC Annamalai
Surface Roughness/Finish
Mirror like Surface Finish on Cloud Gate(Bean), Chicago, USA:
To Achieve mirror finish , the following procedure is followed :
(1). Plan and specify in the PO, during Plate Procurement:
(2). To order annealed cold rolled plates, with high surface finish.
(3).
(4).
(5).
(6). Use GTAW process for filling. Use thinner welding filling rods and less ampherages and control welding heat.
Avoid, surface damages during welding and finishing.
Directional ‘dull’ polished finishes are often
specified for external architectural
applications but this type of surface finish can
exhibit a wide range of surface roughness
dependent upon the type of belt and
polishing grit that has been used. Coarse
polished finishes, with transverse Ra values
> 1 micron, will exhibit deep grooves where
chloride ions can accumulate and destroy the
passive film, thereby initiating corrosion
attack.
Importance of Surface Finish in the Supply
of Stainless Steel structures and facades. Corroded
(highly magnified)
During manufacture, handle and process the plates such
that negligible damages happen to the surface of the
plates.
Use consumable insert for the root. Tack weld using
GTAW process.
During assembly, use mechanical fixtures to set the alignment.
Fine Polished: In contrast, fine polished
finishes with Ra values < 0.5 micron will
generally exhibit clean-cut surfaces, with few
sites where chloride ions can accumulate. If
a directional polished finish is required, in a
coastal/ marine situation, it is important that
the specification should include a ‘maximum’
transverse surface roughness re-quirement
of 0.5 microns Ra .(e.g. a 2K surface finish in
EN10088-2).
A simple description, such as satin polish, is
not sufficient for good corrosion resistance.
The design of external architectural
applications should avoid introducing
features such as ledges, horizontal grooves
and perforations. All of these features will
increase the effective surface area that is
available for harmful species to accumulate
and consequently, the natural washing-off by
rainwater will be minimised
Surface Reflectivity In terms of reflectivity, a ‘smooth’ polished finish will produce a more reflective surface and this could
give significant and unacceptable dazzle, in bright sunlight, if large flat areas are part of the architectural design. For this
type of situation, it may be more appropriate to specify a ‘matt’ non-directional surface, such as a glass bead blasted
finish. However, as with dull polishing, it is important that a ‘fine’ glass bead option should be selected, to minimise the
surface roughness and give the best possible corrosion resistance.
It has long been recognised that the surface
finish on stainless steel has an important
effect on its corrosion resistance. The mere
specification of 1.4401 (316) type stainless
steel for exterior architectural applications is
not in itself sufficient.
Why Surface Finish is Important .
Cloud Gate, is the largest mirror finished SS object
38

By JGC Annamalai
Various Types of Finishings: The following finishes are available for stainless steel surface :
 Mill Finishes
 Mechanically Polished and Brushed Finishes
 Patterned Finishes
 Bead Blasted Finishes
 Electro-Polished Finishes
 Coloured Finishes
 Electrolytically Coloured Finishes
 Electrolytically Coloured and Patterned Finishes
 Organic Coatings
 Specialist Decorative Finishes
(2). Mechanically Polished and Brushed Finishes
(3). Patterned Finishes: These are few examples to illustrate the use of sheets patterned on one side only,known as 2M.
Construction Finishing(Coud Gate) : Welds: All weld reinforcement ridges were removed :
Maintenance:
The Could Gate is 10 m × 13 m × 20 m (33 ft × 42 ft × 66 ft), and weighs 100 tonnes. Plate is SS304 , 10 mm thick.
The surface is polished/buffed and has mirror like finish. The design life of the Cloud Gate, is expected for 1,000 years.
(a). The lower 6 feet (1.8 m) of Cloud Gate is wiped down twice a day by hand(use Windex like solution).
(b). The entire sculpture is cleaned twice a year with liquid detergent(use Tide like Soap solution).
(1). Mill Finishes, per EN10088-2 & ASTM A480, are detailed
in the following pages(Pg-A6-9,A6-10,A6-11,A6-12)
To achieve, Ra<0.5 µm. In practice, Ra<0.5 µm, level of
roughness could most easily be achieved by using 240 grit
silicon carbide polishing belts rather than aluminium oxide
abrasives
Cloth or Fiber buffing will be used to increase the polish
and to get the mirror finish
Abrasive blast pastes are available. Cloth or fiber buffing
wheels with abrasive pastes are also used.
Variety of finish surfaces are possible, with different type of
Buffing wheel material, speed, buffing paste and duration
of Buffing.
Manufacture : These are produced by combination of
(a). surface straining to have the pattern (patterned rolls) and
(b). electrolytically coloring them.
Household Utensils polished at Pedestal Buffing
Stage Name Equipment used Sandpaper type Purpose
1 Rough cut 5-pound (2.3 kg), 4½-inch
(110 mm) electric grinder
40-grit Removed welded seams
2 Initial
contour
15-pound (6.8 kg), 2-inch
(51 mm), air-driven belt sander
80-grit, 100-grit and 120-grit Shaped the weld contours
3 Sculpting air-driven 10-pound (4.5 kg), 1-
inch (25 mm) belt sander
80-grit, 120-grit, 240-grit and
400-grit
Smoothed the weld contours
4 Refining double action sander 400-grit, 600-grit and 800-grit Removed the fine scratches that
were left from the sculpting stage
5 Polishing 10-inch (250 mm) electric buffing
wheel
10 pounds (4.5 kg) of rouge Buffed and polished the surface
to a mirror-like finish
39

By JGC Annamalai
(4). Bead Blasted Finishes
Normally, the color is grey shades
Blast material-Glass Beads
Blast material-Shredded Glass
(5). Electro-Polished Finishes
(6). Coloured Finishes
Electropolishing, also known as electrochemical
polishing, anodic polishing, or electrolytic polishing
(especially in the metallography field), is an
electrochemical process that removes material
from a metallic workpiece, reducing the surface
roughness by levelling micro-peaks and valleys,
improving the surface finish. It is used to polish,
passivate, and deburr metal parts.
Manufacture : Air and granules are blasted on Stainless Steel material surface. Depending on granules size, granule
type/hardness, air pressure, blasting time, the surface will have different structure.
It is often described as the reverse of
electroplating.
It may be used
in lieu of
abrasive fine
polishing in
microstructural
preparation
These colors on the SS, are produced by
electrolytically colouring stainless steel
j. Electrolyte; k. Cathode; l. Work-piece to polish
(anode); m. Particle moving from work-piece to the cathode;
n. Surface before polishing; o.Surface after polishing
Available Beads : Stainless Steel particles,
ceramic beads, aluminum oxide, shredded
nut shells and glass
40

Stainless steels, problems causes-remedies

Stainless steels, problems causes-remedies

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