Material selection of high chromium cast iron in large autogenous mill liner

Commonly used lining materials are high manganese steel, low alloy wear-resistant alloy steel and white cast iron.

High manganese steel is widely used in various wear conditions because of its remarkable work hardening effect. High manganese steel is mainly composed of austenite, and its surface structure transforms into martensite under high impact load, so it is easy to realize work hardening; Under low impact load or low stress, due to insufficient work hardening, the wear resistance of high manganese steel is lower than that of non manganese wear-resistant alloy steel; In the case of large impact, high manganese steel is prone to rheology, resulting in a large amount of deformation of the lining plate, difficult to dismantle, and in serious cases, the bolt will be broken. This is because the yield strength of high manganese steel is low, and the phase transformation occurs on the surface of lining plate due to the continuous impact of materials and grinding balls, resulting in the increase of local volume and tangential size.

The microstructure of low-alloy wear-resistant alloy steel is typical lath martensite structure. Lath martensite has high density dislocation substructure, so it has higher hardness and strength, which is beneficial to improve wear resistance.

The representative material of white cast iron is high chromium cast iron, and the Cr content is usually higher than 12%. High chromium cast iron is a kind of excellent wear-resistant material. The hardness of M7C3 carbide in the structure is as high as 1200 ~ 1800 HV. At the same time, M7C3 carbide is isolated in rod shape. The damage effect of carbide on matrix is reduced, and the toughness of high chromium cast iron is obviously improved. High chromium cast iron is not suitable for strong impact load condition, but suitable for the condition of small impact energy and mainly grinding, which can give full play to the characteristics of high wear resistance.

The results show that under low stress impact load, the wear resistance of high chromium cast iron is the best, followed by low alloy steel and high manganese steel.