White cast irons are widely used in abrasive wear applications involved in the crushing, grinding, milling and handling of abrasive materials such as minerals and ores, both dry and as slurries. Three types of irons are commonly used:
White Iron is unalloyed cast iron with low carbon and silicon content such that the structure is hard brittle iron carbide with no free graphite. These irons are limited in application because of the lack of impact resistance and the difficulty in maintaining the structure in thicker sections. In some cases the castings are designed and produced to have a white structure in certain areas and a grey or flake structure elsewhere to improve toughness.
Martensitic white cast irons containing nickel and chromium are commonly known as Ni-Hards. There are two general types containing 4% Ni-2% Cr, and 8% Cr-6% Ni. Both have a structure of iron and chromium carbides in a matrix of martensite and bainite, but the higher alloy content materials have a type of carbide which is discontinuous and confers greater impact and corrosion resistance.
These irons can be used as cast, but heat treatment improves the hardness and resistance to surface cracking and spalling.
High Chromium cast irons have typical compositions of 15%Cr-3%Mo and 23-28%Cr and a superior combination of abrasion resistance and toughness. In some cases they may be used as cast, but are normally air hardened to develop the optimum properties.
Some of these irons may also be machined after annealing and then hardened to produce a machined abrasion resistant part.
|Material Designation||Vickers Hardness |
|Chemical Composition (%)|
|EN-GJN-HV520||EN-JN2029||520||2.5-3.0||Max 0.8||Max 0.8||Max 0.10||Max 0.10||3.0-5.5||1.5-3.0||-||-|
|EN-GJN-HV550||EN-JN2039||550||3.0-3.5||Max 0.8||Max 0.8||Max 0.10||Max 0.10||3.0-5.5||1.5-3.0||-||-|
|EN-GJN-HV600||EN-JN2049||600||2.5-3.5||1.5-2.5||0.3-0.8||Max 0.08||Max 0.08||4.5-6.5||8.0-10.0||-||-|
|Max 1.0||0.5-1.5||Max 0.08||Max 0.08||Max 2.0||11.0-14.0||Max 3.0||Max 1.2|
|Max 1.0||0.5-1.5||Max 0.08||Max 0.08||Max 2.0||14.0-18.0||Max 3.0||Max 1.2|
|Max 1.0||0.5-1.5||Max 0.08||Max 0.08||Max 2.0||18.0-23.0||Max 3.0||Max 1.2|
|Max 1.0||0.5-1.5||Max 0.08||Max 0.08||Max 2.0||23.0-28.0||Max 3.0||Max 1.2|