球化退火工艺对55MnB钢碳化物球化效果的影响

Effect of spheroidizing annealing process on carbide spheroidization of 55MnB steel

针对55MnB钢设计了亚温退火、等温球化退火、周期球化退火3种球化退火工艺,通过组织观察和硬度测定、碳化物电解萃取、XRD物相分析等手段来研究球化退火工艺对55MnB钢碳化物球化效果的影响规律。结果表明,亚温退火的碳化物球化效果不明显,组织中仍有一些片状珠光体存在;等温球化退火和周期球化退火的碳化物球化效果较好,碳化物基本上呈球状或粒状弥散分布在铁素体基体上。在球化退火过程中,碳化物的主要类型为M3C,并且不随球化退火工艺的改变而改变。

Subcritical annealing, isothermal spheroidizing annealing and cyclic spheroidizing annealing were designed to analyze the effect of spheroidizing annealing process on spheroidization of carbide of 55MnB steel. Microstructure observation, hardness test, carbide electrolytic extraction and XRD phase analysis were carried out. The results show that when the sample was annealed by subcritical annealing, the spheroidization of carbides is not obvious, and there are still some lameiiae carbides existing in the microstructure; however, when the sample was annealed by isothermal spheroidizing annealing or cyclic spheroidizing annealing, the spheroidization of carbide is preferable, in generally the carbides which distribute dispersedly on the ferrite matrix are spherical or granular. During the process of spheroidizing annealing, the main type of carbides in 55MnB steel is M3C and it does not change with the change of spheroidizing annealing process.