Long term industrial practice shows that chromium white cast iron has excellent stability and relatively low production cost in high temperature and high wear environment. Therefore, it is widely used in mining and mineral processing, cement production, pulp and paper industry to grind hard materials, such as ore, coal, gravel and cement. Among them, the working conditions of the impact crusher plate hammer are bad, especially in the crushing of high strength and hardness of hard to break materials, the requirements for the strength and toughness of materials are higher. The traditional sand mold casting method is used in the manufacture of plate hammer, and the material is ordinary high chromium cast iron. Although the wear resistance of high chromium cast iron is higher than that of other materials, its strength is not high, toughness is insufficient, notch sensitivity is high, and it is easy to fracture. Especially in the later period of use, when the thickness of the hammer is small, the fracture tendency of the hammer is intensified. In the process of use, once the fracture occurs, it will inevitably cause shutdown, and even cause damage to the crusher. In addition, the traditional sand casting plate hammer structure density is not high, more impurities, defects, which will reduce the service life of the plate hammer, increase the number of replacement, reduce production efficiency.
The reason of low strength, low toughness and easy fracture of high chromium cast iron in common sand mold casting is that the eutectic carbides in the solidification structure are usually coarse and continuous, which exist in the matrix grains, resulting in the matrix splitting and reducing the toughness of the material. In the further development and application, how to obtain fine primary carbide and eutectic carbide in the solidification structure of the alloy is of great significance to improve the wear resistance of chromium white cast iron.
In order to change the type, composition, quantity, size, shape and distribution of carbides, researchers have tried to improve the size and morphology of carbides by means of rapid cooling, low superheat, alloying, modification, semi-solid forming and rare earth processing.
Pressure casting can increase the temperature of solid-liquid phase line, shift the eutectoid transition point to low temperature, decrease the carbon content, appear new phases and phase regions, change the properties of known phases, and change the shape of equilibrium phase diagram. In addition, the morphology, solidification structure and morphology of the alloy were improved under high pressure. The grain size will change, resulting in a variety of non-equilibrium structures. Therefore, it is worth exploring to modify the solidification structure of chromium alloy by pressure casting technology.