稀土-低熔点合金复合变质处理对超高碳钢微观组织及力学性能的影响

Influence of Multiple Modifier Containing Rare Earths and Low Melting-Point Alloy on Microstructure and Mechanical Properties of Ultrahigh Carbon Steel

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。

Ultrahigh carbon steel containing 1.9%C was modified with multiple modifier containing rare earths and low melting alloy.Microstructure and mechanical properties of ultrahigh carbon steel were studied with OM,SEM,EDS and DSC.The results showed that the continuous eutectic carbide network structure of the ultrahigh carbon steel was broken up,and the austenite grains became much finer after modification.Because Ce2O2S had much negative Gibbs energy,Ce was easy to react with O and S to form Ce2O2S in the steel.The austenitizing temperature was raised by addition of RE and low melting-point alloy which were the elements of strongly promoting and stabilizing the pearlite.After quenched and tempered,the isolated carbides were dispersed homogeneously in the martensite matrix.By multiple modification,the impact toughness of the steel ingot was greatly increased from 5.8 J·cm-2 to 12.5 J·cm-2 with hardness kept about HRC=65,indicating well comprehensive mechanical properties.