The Research And The Application Of The Acicular Cast Iron At Wedges

Sound performance of acicular cast iron has been always deemed as an emphasis in current material research. Many countries such as China, America, Finland and so on did not announced to successfully develop the bainite cast iron until 1978. Acicular cast iron structure has excellent wear resistance, high strength and tenacity. After research, acquirement of acicular structure (bainite) cast iron has mainly two methods. One is to depend on rigid heat treatment processing on the basis of chemical ingredient, the other is to depend on the addition of some Nickel, Molybdenum, etc alloy elements, with the features of long production cycle, high energy consumption and unsuitable volume production. The latter method is suitable to volume production, which only is required to have rigid casting processing control in order to obtain ideal acicular structure.The article is to depend on the addition of some Nickel, Molybdenum, etc alloy ,defer the changing time of austenitic gray cast iron, achieve the acicular cast iron in the casting directly. On the basis of rigid processing control, depending on adjusting nucleating agent type and content in the smelting iron, and adjusting pouring temperature, cooling time and shakeout time to control acicular cast iron formation to research metallurgical structure and mechanical property. Acicular structure cast iron is successfully applied to friction shoe that satisfies all performance demands.By research and analysis,the result is: The addition of 0.90~1.00 percent of molybdenum added in gray cast iron is a key to obtain acicular structure. 1.20~1.40 percent of copper alloy added may promote transform from austenite to prevent against the formation of pearlitic. Nucleating treatment is a key to obtaining acicular structure cast iron. In the case of 0.10% addition, cementite is easy to be formed. While in the case of more addition, pearlitic is easy to be formed. The addition of 0.20%-0.25% is qualified. The hardness of friction shoe constantly decreases with the prolongation of shakeout time, basically it fluctuates around the line. Depend on controlling, shakeout in 15～40 minutes after pouring can obtain acicular structure cast iron. Practices proved, all kinds of performance of acicular structure cast iron friction shoe can satisfy using requirement.