There are two main types of Ni-hard Iron Castings: Ni mass fraction is 4% and Cr mass fraction is about 2%. The metallographic structure of this nickel hard white cast iron consists of M3C carbide and the mixed matrix of martensite and austenite. The mass fraction of the other nickel is 6% and the mass fraction of chromium is about 9%. The carbide of this nickel hard cast iron is mainly M7C3 type.
The main characteristics of nickel hard white cast iron are as follows:
(1) Good casting performance. Because the total amount of alloy elements is low, nickel hard white cast iron is easy to smelt and has good casting performance.
(2) heat treatment is simple and convenient. Martensite matrix can be obtained in the as-cast state without high-temperature treatment, thus avoiding the danger of cracking caused by too high heating temperature. Usually, only stress-relieving annealing and low-temperature tempering treatment are required to obtain tempered martensite with small brittleness.
(3) good wear resistance. Compared with common white cast iron, it has higher hardness, better hardenability and better wear resistance. The application of nickel hard cast iron in various occasions of industrial production, whether wet grinding or dry grinding, has proved to have good wear resistance.
It is worth noting that, due to the shortage of nickel resources and high price, nickel hard white cast iron is mainly used to manufacture important wear resistant castings such as rollers, lining plates and grinding rollers, while ordinary castings such as grinding balls are generally not made of nickel hard cast iron.
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