As early as in, the United States studied high chromium cast iron. Due to the high content of chromium, on the one hand, chromium is easy to combine with carbon during cupola flame smelting, making the carbon content difficult to control; On the other hand, because chromium is easily oxidized and burned in the oxidation zone of cupola, the yield of chromium is very low. Therefore, only after World War II, with the large-scale use of electric furnace, high chromium cast iron has been greatly developed and applied.
When the addition of chromium reaches a certain value of chromium carbon ratio, the combination law of iron and carbon changes during solidification. The morphology and structure of eutectic carbide changes from continuous network type to disconnected and isolated type, and its hardness increases greatly. The Vickers hardness of prototype carbide is, while the hardness of transformed carbide increases to, The change of carbide composition and morphology improves the wear resistance and directivity of high chromium cast iron at the same time, so high chromium cast iron has been considered as an ideal wear-resistant material since its inception. As early as the early s of the century, Chinese scholars conducted in-depth research on the application of high chromium cast iron in wear-resistant castings. At present, it has been widely used in metallurgy, mining, building materials, electric power, transportation, machinery and other fields, especially in mining, building materials and electric ball mill, and achieved good economic benefits.
High chromium cast iron is divided into hypoeutectic and hypereutectic according to the content of carbon and chromium. At present, hypoeutectic high chromium cast iron is mostly used in actual production. The eutectic carbides of hypoeutectic high chromium cast iron are distributed in isolated strip and broken network. Therefore, hypoeutectic high chromium cast iron has high wear resistance and relatively good directivity. It can be applied to the production of parts and components under certain impact conditions, such as impact crusher hammer, ball mill lining plate, grinding ball and clarified vegetable loading overflow parts. Compared with hypoeutectic high chromium cast iron, hypereutectic high chromium cast iron has higher carbon and chromium content, significantly increased carbide volume fraction and unparalleled high wear resistance. However, increasing carbide volume fraction is a double-edged sword, especially there are a large number of primary phase carbides in hypereutectic still complex iron, This kind of carbide is coarse and the initial property is very low, which leads to the sharp decline of the overall properties of hypereutectic high chromium cast iron, and cracks are easy to appear in the process of casting and heat treatment, so as to improve the scrap rate of castings.
The modification principle of high chromium cast iron is mainly to add strong carbide metal to increase the crystallization core and add active elements such as rare earth and Zhong Na han to purify the liquid steel, enrich the grain boundary and inhibit the biased growth of carbide. Because the carbon content of hypereutectic high chromium cast iron exceeds the eutectic point, the primary phase carbide is the focus of modification, that is, to find the low-cost primary phase carbide crystallization core and the component supercooling element to narrow the carbide crystallization temperature range.