Wear resistant cast materials for the mining industry

Wear Resistant Cast Materials
for the Mining Industry

Ricardo Fuoco
METSO Minerals – Brazil

Outline
• 1. Introduction

• 2. Types of wear in the mining industry (comminution)

• 3. Wear resistant cast materials to:
• Crushers
• SAG/AG mill
• Balls mill / Vertimill

• 4. Summary

WEAR RESISTANT CAST MATERIALS FOR THE MINING INDUSTRY
© Metso RICARDO FUOCO - 2ND BRICS FOUNDRY FORUM - CHINA – MAY 8-11, 2012
2

Introduction

3

Introduction
Typical mining operations

• 1. Drilling

• 2. Blasting

• 3. Comminution

4

Introduction
Typical mining operation

Drilling

5

Introduction
Typical mining operation

Blasting

6

Introduction
Typical comminution operation in the mining industry

• Comminution:

• 1. Crushing

• 2. Grinding (AG/SAG Mills, Ball Mills and Vertimills)

7

Introduction
1. Crushers

8

Introduction
1. Crushers 2. SAG Mill

9

Introduction
1. Crushers 2. SAG Mill 3. Ball Mill/Vertimill

10

Types of wear in the mining industry
(comminution)

11

(comminution)

Vertimill

12

(comminution)
High stress abrasion and impact

Vertimill

13

(comminution)
High stress grinding abrasion

Vertimill

14

(comminution)
High stress grinding abrasion

Erosion

Vertimill

15

(comminution)
• Crushers:
• High stress abrasion
• High impact forces
• Gouging abrasion

Wear resistant material with high toughness:
Austenitic Mn steels

16

(comminution)
• AG/SAG mills and large balls mills:
• High stress grinding abrasion
• Medium impact forces
• Scratching and micro-cracking resistant

Wear resistant material with some toughness:
Cr-Mo low alloy steels

17

(comminution)
• Small ball mills and Vertimills:
• Erosion
• Low stress scratching abrasion
• Low impact forces

Very high wear resistant material:
High Cr white cast iron

18

(comminution)
• Hardness (and wear resistance):
Hardness (HB)
700

600
600 HB
500

400
450 HB
300 Series1
375 HB
320 HB
200

100 200 HB

0
Hadfield Hadfield Cr-Mo low Cr-Mo low Hi Cr White
Steel (initial) Steel alloy steel alloy steel Cast Iron
(deformed) (pearlitic) (martensitic)

19

(comminution)
• Charpy Impact test (toughness):

Impact (J)
200
200 J
180
160
140
120
100 Series1
80
60
40
20 10 J 15 J 2J
0
Hadfield Steel Cr-Mo low alloy Cr-Mo low alloy Hi Cr White Cast
(initial) steel steel Iron
(pearlitic) (martensitic)

20

Wear resistant cast materials
Crusher parts

21

Types of crushers: Primary gyratory

22

Types of crushers: Jaw crusher

23

Types of crushers: Cone crusher

24

Austenitic Mn steel - Typical castings

25

Austenitic Mn steel - Typical castings

26

Austenitic Mn Steels for Crushers Parts

• Typical Spec described in the ASTM A128 Grades B and C:
• 12 – 14% Mn / 1.1 – 1.25% C

• High Mn special grades:
• 17 - 19% Mn
• 19 - 22% Mn

27


High Mn special
grades

28

Austenitic Mn Steels for Crushers Parts – wear mechanisms

Gouging abrasion (deep surface scratching and high energy indentation)

29

Surface layer: microstructure
after deformation

400 to 500 HB

Core: original microstructure

200 HB

© Metso WEAR RESISTANT CAST MATERIALS FOR THE MINING INDUSTRY
30
RICARDO FUOCO - 2ND BRICS FOUNDRY FORUM - CHINA – MAY 8-11, 2012

Austenitic Mn Steels – Heat treatment

• Critical step in the production: Heat Treatment

• Solution heat treatment at 1050 – 1100°C
• Quench in water

31


Microstructure in the as cast condition Microstructure after solution HT

Charpy impact energy = 10J Charpy impact energy = 180J

32


• Typical problem in the heat treatment (low toughness).

Incomplete solution HT Complete solution HT but ineffective
(low temperature or insufficient time) quenching (low cooling rate)
33

• Typical quenching problem

TTT curves of carbides re-precipitation during the cooling after solution
of Hadfield austenitic steel
RICARDO FUOCO - 2ND BRICS FOUNDRY FORUM - CHINA – MAY 8-11, 2012 34


Solution
Carbide re-precipitation

TTT curves of carbides re-precipitation during the cooling after solution
of Hadfield austenitic steel


Effect of the grain boundaries coverage by continuous carbide re-precipitation in the
Charpy impact energy of different grades of Hadfield austenitic manganese steels

36

Austenitic Mn Steels

• The main problems in austenitic Mn steels production are
related to heat treatment;

• Ineffective heat treatments develops microstructures with
carbides which result in low toughness and possibility of
breakage problems in field.

37

SAG/AG Mills (and large ball mills)

38


Feed end side
39


Discharge side (grates)
40


Lifting effects of the shell liners illustrated by charge motion simulation
(TCS - Total Critical Speed)
41


42


43


Charge motion illustration showing the atriction and the impact grinding
mechanisms.
44

SAG/AG Mills – Typical castings

45

SAG/AG Mills – Alloy specification

• Typical Specification: Cr-Mo steels

• Cr-Mo steels (Pearlitic microstructure) - 320 HB

• Cr-Mo steels (Martensitic microstructure) - 375 HB

46

SAG/AG Mills – Heat treatment


• Pearlitic – Normalizing and Tempering

• Martensitic – Quenching in blown air and tempering

47

SAG/AG Mills – Heat treatment (TTT curve)
• Schematic TTT curves of Cr-Mo steel showing the formation of Pearlite
and Martensite during the heat treatment.

48

SAG/AG Mills – Typical microstructures
• Cr-Mo steel (0.6%C) after normalizing and temper heat treatment

Pearlite

Spheroidized
Pearlite

400x
49

SAG/AG Mills – Typical microstructures
• Cr-Mo steel (0.45%C) after quenching and temper heat treatment

200x

50

Cr-Mo steels

• The main problems in Cr-Mo steels production are related to
heat treatment;

• Inadequate microstructures and hardness result in low wear
resistance (premature wear) or low toughness and possibility of
breakage problems in field;

• Improper mill operation frequently promote direct impact of balls
on liners resulting in accelerated wear and risk of breakage.

51

Improper mill operation causing direct impact of balls on liners

Charge motion simulation Charge motion simulation
(< 75% TCS - no impact) (> 75% TCS - direct impact on liners)

52

Improper mill operation causing direct impact of balls on liners

Typical aspect of liner surface after direct impact of balls on liners
promoting accelerated wear and risk of liner breakage.


Balls mills and Vertimills

54

Balls mills

55

Vertimills

56

Vertimills – Grinding mechanism

57

Ball mills – Typical wear parts

58

Vertimills – Typical wear parts

59

Balls mills and Vertimills – Alloy specification

• Typical specification: ASTM A532

• Grade II E : 18 – 23% Cr / 2.0 – 3.0% C

• Grade III A : 23 – 28% Cr / 2.5 – 3.5% C

60

Balls mills and Vertimills – Alloy specification

ASTM A532 Grade III A

ASTM A532 Grade II E

61

SAG/AG Mills – Heat treatment


• Solution (austenite destabilization) at 950 – 1000°C
• Quenching in calm air / blow air
• Tempering

62

Balls mills and Vertimills - microstructures

1000x SEM, 2000x


Balls mills and Vertimills – wear mechanism (erosion)

64


Carbides HV= 1500

Martensite HV=700
65


– Carbides (M7C3) has high hardness > 1500 HV

– Most important abrasive is quartz with 1.000 to 1.300 HV

66

High Cr white cast irons

• The main problem in high Cr white cast iron production is crack
formation;

• Premature shake out, inadequate handling and thermal shock
are common causes of cracks in high Cr cast iron castings.

67

Summary

68

Summary

• The most commonly used cast materials in the mining industry
are:
• Austenitic Mn steels – normally used in Crusher
application due to its very high toughness and fairly good
wear resistance;
• Cr-Mo low alloy steels – normally used in SAG/AG
mills application due to its high wear resistance and
reasonable toughness;
• High Cr white cast iron – normally used in ball mills
and vertimills application due to its very high wear
resistance.

69

Wear resistant cast materials for the mining industry

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Wear resistant cast materials for the mining industry