耐磨鑄铁热处理.docVIP

In this paper, three different kinds of heat treatment were applied to three test samples of cast iron: quenching at 980°C for three hours and tempering at 220°C for three hours; quenching at 530°C for six hours; and quenching at 1120°C for six hours and tempering at 220°C for three hours. The samples were then examined, and a comparison made of the as-cast microstructure obtained in the different heat-treatment processes. The result was that the morphologies – specifically, the amount and distribution of precipitation carbide – were found to be different. Of the different processes, the test material which had undergone the process of quenching at 980°C for three hours and tempering at 220°C for three hours was found to have the most dispersed, homogeneous, and stable microstructure. Through measuring and comparing the Rockwell hardness value (HRC), obtained that when the test material that had undergone the process of 980°C for three hours and tempering at 220°C for three hours, the Rockwell hardness value (HRC) was highest. In summary, the test material in the heat treatment process of 980°C for three hours and tempering at 220°C for three hours resulted in the most homogeneous, hard, and stable microstructure. Keywords: wear resisting white iron; quenching; microstructure; hardness. 耐磨铸铁有两种形式，它是根据两种不同的磨损形式划分的。磨损通常存在两种不同的形式，一种为干式磨损，如轧辊、球磨机磨球以及喷丸机叶片等工件的磨损；另一种为润滑磨损，如滑块、轴承以及机床导轨等工件的磨损。用于前一种磨损形式的耐磨铸铁为抗磨铸铁，用于后一种形式的耐磨铸铁为减磨铸铁。铬系白口铸铁就是抗磨铸铁的一种。高铬铸铁属于耐磨铸铁中的抗磨白口铸铁，它是现今性能最好，应用最广泛的一种合金铸铁。合金白口铸铁是在普通白口铸铁基础上添加一些合金元素如镍、锰、钨等形成的，这些合金元素的主要作用是形成耐磨基体和提高淬透性[3]。 根据铬碳化物的类型将耐磨白口铸铁分为三个品种：加入铬但未改变渗碳体晶体类型，即碳化物仍为M3C型的铬白口铸铁称为低铬白口铸铁；加入铬量较高，大多数铬碳化物已由M3C型转变为M3C7型的铬白口铸铁称为高铬白口铸铁；组织中兼有M3C型和M3C7型的铬白口铸铁称为中铬白口铸铁。 表1-1 耐磨白口铸铁的牌号和化学成分[2] Table 1-1 Grade and chemical composition (wt.%) of wear cast iron. 牌号 化学成分（质量分数，%） C Si Mn P S Cr Ni Mo Cu KmTBCr12 2.0~3.3 1.5 2.0 0.10 0.06 11.0~14.0 ≦2.5 3.0 1.2 高铬铸铁的w（Cr）为12%~30%，表1-1中的KmTBCr12、KmTBCr15Mo、KmTBCr20Mo、KmTBCr26都是高铬白口铸铁。高铬铸铁的重要组织特点是基体上均匀分布着M7C3型