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采用自制的稀土-低熔点合金对一种含碳量为1.9%的超高碳钢进行了变质处理,通过OM,SEM,EDS,DSC研究了变质处理和热处理工艺对超高碳钢的微观组织和力学性能的影响。结果表明:超高碳钢经变质处理后,共晶碳化物断网,获得了不连续的块状碳化物,初生奥氏体晶粒明显细化;由于Ce2O2S的吉布斯自由能负值较大,其稳定性较高,因此,稀土元素与O,S在钢中最易形成的稀土氧硫化合物为Ce2O2S;同时稀土与低熔点合金元素的加入,是强烈促进珠光体的元素,具有稳定珠光体的作用,提高了奥氏体化温度;经淬火与低温回火后,获得了马氏体基体上分布着弥散均匀、细小的不连续断网碳化物,冲击韧性得到了明显提高,其ak值由5.8.Jcm-2增加到12.5.Jcm-2,且硬度值基本保持HRC=65,获得了良好的综合力学性能。
A homemade rare earth-low melting point alloy was used to modify a super-high carbon steel with a carbon content of 1.9%. The effects of modification and heat treatment on the microstructure of ultra-high carbon steel were investigated by OM, SEM, EDS and DSC. And mechanical properties. The results show that after the super-high carbon steel is altered, the eutectic carbide is broken to obtain discontinuous massive carbides, and the primary austenite grains are obviously refined. Since the negative Gibbs energy of Ce2O2S is negative Large, and its stability is high. Therefore, rare earth elements and O, S are the most easy to form rare earth oxysulfide compounds in Ce2O2S. At the same time, the addition of rare earth and low melting point alloying elements strongly promote pearlite and have stable Pearlite role to improve the austenitizing temperature; after quenching and tempering at low temperature, the martensite matrix was obtained on the distribution of uniform, small broken discontinuous carbide, the impact toughness has been significantly improved, its ak value increased from 5.8.Jcm-2 to 12.5.Jcm-2, and the hardness value was basically maintained HRC = 65, obtained a good comprehensive mechanical properties.