摘要
为了进一步优化贝氏体非调质钢锻件的组织和性能,采用组织观察、力学性能测试等方法研究了回火温度(200~500℃)对一种钒钛微合金化Mn-Cr系贝氏体型非调质钢锻后微观组织及力学性能的影响。结果表明,实验用钢锻态时的组织为板条状下贝氏体+粒状贝氏体的混合组织。随着回火温度升高,组织逐渐发生回复,马氏体/奥氏体(M/A)组元逐渐分解,并析出细小的渗碳体;回火温度提高到500℃时,M/A组元完全分解,渗碳体球化。随着回火温度升高,实验用钢的抗拉强度逐渐降低,从锻态的1418 MPa逐渐降低到500℃回火时的1094 MPa;而屈服强度则呈现先缓慢增加后降低的变化趋势,在400℃回火时达到峰值;屈强比由锻态时的0.73逐渐升高至500℃回火时的0.93。与强度变化趋势不同,实验用钢的冲击功随回火温度呈现先增加后降低,最后再增加的变化特征,在400℃回火时冲击吸收功最小,呈现出一定的回火脆性;而500℃回火后冲击功最大,较锻态样品提高约27%。因此,对实验用钢锻后进行适当的回火处理,有利于获得与调质合金钢相当的良好综合力学性能,从而有助于扩大其应用范围。
With continuous demands for cost reduction and environmental protection, bainitic forging steels, which have notably higher strength and toughness combination than ferritic-pearlitic forging steels, have been developed and gained an increasingly applications in a variety of critical automotive parts. In order to optimize the microstructure and properties of bainitic forging steel, the influences of tempering temperature ranging from 200 ℃ to 500 ℃ on the microstructure and mechanical properties of a Mn-Cr type bainitic forging steel were investigated based on microstructural observations and mechanical property tests. The results show that the microstructure in the as-forged condition of the tested steel is a mixture of lower lath-bainite and granular bainite. With the increase of tempering temperature(Ttemp), the microstructure began to recover and the large blocky martensite/austenite(M/A) constituents decomposed granularly with the precipitation of fine cementites. Further increasing Ttempto 500 ℃, the blocky M/A constituents decomposed completely and the cementites were spheroidized. Consequently, the ultimate tensile strength(UTS) decreases gradually from 1418 MPa of the as-forged specimen to 1094 MPa of the specimen tempered at 500 ℃ with increasing Ttemp, while the yield strength(YS) increases gradually with increasing Ttemp at first, reaching a peak at 400 ℃, and then decreases with further increasing Ttemp.As a result, the yield strength ratio(YS/UTS) increases continuously from 0.73 in the as-forged state to0.93 of the specimen tempered at 500 ℃. Unlike those of the strengths, the impact energy increases at Ttemp of 200 ℃ at first, then it decreases and reaches a valley at 400 ℃, and finally it increases notably again at Ttempof 500 ℃, an increase of about 27% than that of the as-forged one. It is concluded that suitable tempering treatment after forging can obtain better strength and toughness balance of the tested bainitic forging steel, and thus help to expand its application range.
作者
王占花
惠卫军
谢志奇
张永健
赵晓丽
WANG Zhanhua;HUI Weijun;XIE Zhiqi;ZHANG Yongjian;ZHAO Xiaoli(School of Mechanical,Electronic and Control Engineering,Beijing Jiaotong University,Beijing 100044,China)
出处
《金属学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第11期1441-1451,共11页
Acta Metallurgica Sinica
基金
国家重点研发计划项目No.2016YFB0300100。
关键词
贝氏体型非调质钢
回火温度
力学性能
微观组织
bainitic forging steel
tempering temperature
mechanical property
microstructure
