Wear resistant cast materials for the mining industry

Ricardo Fuoco

METSO Minerals – Brazil

Wear Resistant Cast Materials

for the Mining Industry

© Metso

• 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

Outline

2

WEAR RESISTANT CAST MATERIALS FOR THE MINING INDUSTRY

RICARDO FUOCO - 2ND BRICS FOUNDRY FORUM - CHINA – MAY 8-11, 2012

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Introduction

3



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• 1. Drilling

• 2. Blasting

• 3. Comminution

4

Introduction Typical mining operations



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Introduction Typical mining operation

5

Drilling



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6

Blasting



Introduction Typical mining operation

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• Comminution:

• 1. Crushing

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

7

Introduction Typical comminution operation in the mining industry



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1. Crushers




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2. SAG Mill 1. Crushers




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




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Types of wear in the mining industry

(comminution)

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Vertimill

12


(comminution)



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(comminution)

Vertimill

High stress abrasion and impact



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(comminution)

Vertimill


High stress grinding abrasion



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(comminution)

Vertimill


High stress grinding abrasion

Erosion



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• Crushers:

• High stress abrasion

• High impact forces

• Gouging abrasion

Wear resistant material with high toughness:

Austenitic Mn steels

16


(comminution)



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• 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)



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• 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)



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• Hardness (and wear resistance):

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(comminution)

0

100

200

300

400

500

600

700

Hadfield

Steel (initial)

Hadfield

Steel

(deformed)

Cr-Mo low

alloy steel

(pearlitic)

Cr-Mo low

alloy steel

(martensitic)

Hi Cr White

Cast Iron

Series1

Hardness (HB)

200 HB

450 HB

320 HB

375 HB

600 HB



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• Charpy Impact test (toughness):

20


(comminution)

0

20

40

60

80

100

120

140

160

180

200

Hadfield Steel

(initial)

Cr-Mo low alloy

steel

(pearlitic)

Cr-Mo low alloy

steel

(martensitic)

Hi Cr White Cast

Iron

Series1

Impact (J)

200 J

10 J 15 J 2 J



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Wear resistant cast materials Crusher parts

21



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Wear resistant cast materials Types of crushers: Primary gyratory



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Wear resistant cast materials Types of crushers: Jaw crusher



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Wear resistant cast materials Types of crushers: Cone crusher



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25

Wear resistant cast materials Austenitic Mn steel - Typical castings



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Wear resistant cast materials Austenitic Mn steel - Typical castings



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Wear resistant cast materials 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



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28


High Mn special

grades



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29

Wear resistant cast materials Austenitic Mn Steels for Crushers Parts – wear mechanisms

Gouging abrasion (deep surface scratching and high energy indentation)



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Surface layer: microstructure

after deformation

Core: original microstructure

400 to 500 HB

200 HB

30




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Wear resistant cast materials Austenitic Mn Steels – Heat treatment

• Critical step in the production: Heat Treatment

• Solution heat treatment at 1050 – 1100°C

• Quench in water



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Microstructure in the as cast condition Microstructure after solution HT

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



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


Incomplete solution HT

(low temperature or insufficient time) Complete solution HT but ineffective

quenching (low cooling rate)



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

of Hadfield austenitic steel


• Typical quenching problem



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

of Hadfield austenitic steel

Solution Carbide re-precipitation





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36

Effect of the grain boundaries coverage by continuous carbide re-precipitation in the

Charpy impact energy of different grades of Hadfield austenitic manganese steels




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Wear resistant cast materials 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.



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Wear resistant cast materials SAG/AG Mills (and large ball mills)

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Feed end side



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Discharge side (grates)



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Lifting effects of the shell liners illustrated by charge motion simulation

(TCS - Total Critical Speed)



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Charge motion illustration showing the atriction and the impact grinding

mechanisms.



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Wear resistant cast materials SAG/AG Mills – Typical castings



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46

Wear resistant cast materials SAG/AG Mills – Alloy specification

• Typical Specification: Cr-Mo steels

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

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



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Wear resistant cast materials SAG/AG Mills – Heat treatment


• Pearlitic – Normalizing and Tempering

• Martensitic – Quenching in blown air and tempering



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• Schematic TTT curves of Cr-Mo steel showing the formation of Pearlite and Martensite during the heat treatment.

48

Wear resistant cast materials SAG/AG Mills – Heat treatment (TTT curve)



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• Cr-Mo steel (0.6%C) after normalizing and temper heat treatment

49

Wear resistant cast materials SAG/AG Mills – Typical microstructures

400x

Pearlite

Spheroidized

Pearlite



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• Cr-Mo steel (0.45%C) after quenching and temper heat treatment

50

Wear resistant cast materials SAG/AG Mills – Typical microstructures

200x



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51

Wear resistant cast materials 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.



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52

Wear resistant cast materials Improper mill operation causing direct impact of balls on liners

Charge motion simulation

(< 75% TCS - no impact)

Charge motion simulation

(> 75% TCS - direct impact on liners)



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Typical aspect of liner surface after direct impact of balls on liners

promoting accelerated wear and risk of liner breakage.

Wear resistant cast materials Improper mill operation causing direct impact of balls on liners



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Wear resistant cast materials Balls mills and Vertimills

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Wear resistant cast materials Balls mills



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Wear resistant cast materials Vertimills



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Wear resistant cast materials Vertimills – Grinding mechanism



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Wear resistant cast materials Ball mills – Typical wear parts



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Wear resistant cast materials Vertimills – Typical wear parts



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Wear resistant cast materials 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



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Wear resistant cast materials Balls mills and Vertimills – Alloy specification

ASTM A532 Grade III A

ASTM A532 Grade II E



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Wear resistant cast materials SAG/AG Mills – Heat treatment


• Solution (austenite destabilization) at 950 – 1000°C

• Quenching in calm air / blow air

• Tempering



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Wear resistant cast materials Balls mills and Vertimills - microstructures

1000x SEM, 2000x



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Wear resistant cast materials Balls mills and Vertimills – wear mechanism (erosion)



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Martensite HV=700

Carbides HV= 1500



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– Carbides (M7C3) has high hardness > 1500 HV

– Most important abrasive is quartz with 1.000 to 1.300 HV



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Wear resistant cast materials 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.



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Summary

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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.



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Wear resistant cast materials for the mining industry

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