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ABRASION RESISTANT IRONS
White Irons, Ni-Hard and High Chromes:
BS4844 ASTM A532
BS 4844 ASTMA532
White Irons
These irons, on fracture appear as white silvery fractures.
The carbon in the iron is no longer free grey coloured graphite but is locked in chemical compositions of hard wearing carbides.
The unalloyed White Irons have a hardness of 200-350 BHN the lower end of the hardness scale can be machined but generally are used as cast.

 The use of white irons is generally in low impact abrasive situations such as liner plates and abrasive material pump cases.

Chemical composition of unalloyed and low alloy grades                
  BS 4844 White Irons
Most Common Grade 1A

Grade
Carbon %
Silicon %
Manganeses %
Chrome %
Phosphorus %
1A
2.4 to 3.4
0.5 to 1.5
0.2 to 0.8
2.0 Max
O.15 Max
1B
2.4 to 3.4
0.5 to 1.5
0.2 to 0.8
2.0 Max
0.50 Max
1C
2.4 to 3.0
0.5 to 1.5
0.2 to 0.8
2.0 Max
0.15 Max

Ni-Hard
( Nickel - Chromium Alloyed )

In these irons a development of iron-chromium carbides produce a tougher more abrasion resistant iron.
The variation of carbon content effects the toughness and abrasion resistance.
Greater carbon increases the resistance to abrasion, however at the loss of toughness and vice versa lowering the carbon increases toughness but decreases the resistance to wear.
Hardness ranges dependent on section thickness can be between 450-600 BHN

 The use for Ni-Hards is in pulverising, crushing and impact wear plates also in heavy duty pump casings and impellers for slurry and gravel applications.

Chemical composition of nickel chromium alloys
BS 4844 Ni-Hard Irons
Most Common Grade 2B
Grade
Carbon %
Silicon %
Manganese %
Nickel %
Chrome %
2A
2.7 to 3.2
0.3 to 0.8
0.2 to 0.8
3.0 to 5.5
1.5 to 3.5
2B
3.2 to 3.6
0.3 to 0.8
0.2 to 0.8 3.0 to 5.5
1.5 to 3.5
2C
2.4 to 2.8
1.5 to 2.2
0.2 to 0.8 4.0 to 6.0
8.0 to 10.0
2D
2.8 to 3.2
1.5 to 2.2 0.2 to 0.8 4.0 to 6.0 8.0 to 10.0
2E
3.2 to 3.6
1.5 to 2.2 0.2 to 0.8 4.0 to 6.0 8.0 to 10.0

High Chromium Alloys

These irons produce a more continuous structure of iron-chromium carbides.
After heat treatment these irons have a hardness range of 600-650 BHN

All the white irons are difficult to machine, however advances in ceramic machining tips have vastly improved the prospects.
They are nearly impossible to drill and tap and hace steel inserts cast into the casting to allow drilling and tapping to take place.

Chemical Composition of High Chrome irons
BS 4844
Most Common Grade 3E
Grade
Carbon %
Silicon %
Manganese %
Moly.%
Nickel %
Chrome %
Copper %
3A
1.8 to 3.0
1.0 Max
0.5 to 1.50
2.5 Mx
2.0 Max
14 to 17
2.0 Max
3B
3.0 to 3.6
1.0 Max 0.5 to 1.5 3.0 Max
2.0 Max 14 to 17
2.0 Max
3C
1.8 to 3.0
1.0 Max 0.5 to 1.5 3.0 Max
2.0 Max 17 to 22
2.0 Max
3D
2.0 to 2.8
1.0 Max 0.5 to 1.5 1.5 Max
2.0 Max 22 to 28
2.0 Max
3E
2.8 to 3.5
1.0 Max 0.5 to 1.5 1.5 Max
2.0 Max 22 to 28
2.0 Max
3F
2.0 to 2.7
1.0 Max 0.5 to 1.5 2.5 Max
2.0 Max 11 to 13
2.0 Max
3G
2.7 to 3.4
1.0 Max 0.5 to 1.5 3.0 Max
2.0 Max 11 to 13
2.0 Max



 
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