Mn含量对超低碳调质高强钢组织和性能的影响

Effect of Mn content on microstructure and mechanical properties of ultra-low carbon high strength steel after quenching and tempering

研究了Mn含量的变化(Mn含量由1.8%至5.0%)对超低碳高强钢经调质热处理工艺后,其相变行为以及组织性能的变化规律。结果表明:随着Mn含量的提高,淬火相变温度呈线性降低,显微组织由仿晶界铁素体(FGBA)和粒状贝氏体(GB)向马氏体(M)转变;2.4%~5.0%Mn钢经930℃淬火和300~600℃回火后,其屈服强度可达690~960 MPa级别,且-20℃冲击性能良好;但是,1.8%Mn和2.4%Mn试验钢的低温冲击性能明显优于3.0%Mn和5.0%Mn的试验钢,主要是由于前者组织中FGBA和GB发生了较大的塑性变形,而后者M组织变形非常小。

Phase transformation behavior, microstructure and mechanical properties of ultra-low carbon high strength steels with Mn content ranging from 1.8% to 5.0% were studied after hot rolling, quenching and tempering heat treatment. The results show that with the increase of Mn content, the phase transformation temperature during quenching decreases linearly and the microstructure changes from grain boundary allotrimorphic ferrite （FGBA ） and granular bainite （GB） to martensite （M）. The yield strength of the steel containing 2.4%-5.0% Mn quenched at 930 ℃ and tempered between 300-600 ℃ can reach 690-960 MPa, and with good impact toughness at -20 ℃. But the impact toughness of steels containing 1.8% and 2.4% Mn is much better than that of steels containing 3.0% and 5.0% Mn, due to a larger plastic deformation of FGBA and GB microstructure in the former, while the martensite has little deformation ability in the latter.