控轧控冷型高强钢高温下的力学性能试验研究

Experimental study on mechanical properties of TMCP high strength steel at elevated temperatures

通过稳态法进行了控轧控冷(TMCP)型Q550高强钢在不同温度下的力学性能试验研究,得到常温及200~800℃9个不同高温下钢材的表观特征、应力-应变关系与基本力学性能参数,包括弹性模量、屈服强度、抗拉强度及断后伸长率。结果表明:应力-应变关系曲线在常温时有屈服平台而高温下没有,在超过300℃的高温下曲线形状不同;温度不超过300℃时弹性模量与强度小幅增长,此后二者皆随温度升高而减小,且400~700℃为主要的衰减区间;温度不超过450℃时断后伸长率有所折减,此后则随温度升高而增大。与已有的淬火回火(QT)型Q550高强钢相应研究结果的对比表明,TMCP与QT型Q550高强钢高温下的强度折减规律与程度基本一致,但TMCP型Q550高强钢高温下的弹性模量折减程度比QT型Q550高强钢严重。从微观组织方面解释了Q550高强钢高温力学性能的变化。根据试验结果,建立TMCP型Q550高强钢高温下的力学性能参数模型。

An experimental study was conducted on TMCP(Thermo-Mechanical Controlled Process) high-strength steel Q550 by the steady-state method to investigate its mechanical properties at different temperatures.The experimental phenomena, stress-strain relationship and basic mechanical properties including elastic modulus, yield strength, ultimate strength and ultimate elongation at 30~800℃ were obtained.Results show that the yield plateau of the stress-strain curve only exists at 30℃, and the curve shape changes significantly at above 300℃.Elastic modulus and strength increase slightly at 200~300℃ but decrease at above 300℃ and mainly reduce at 400~700℃.Ultimate elongation decreases at 200~450℃ but increases at above 450℃.The comparison between the test results and corresponding research results of QT(Quenched and Tempered) high-strength steel Q550 shows that, at the same temperature the degree of strength reduction of TMCP Q550 steel is almost consistent with QT Q550 steel, while the degree of reduction on elastic modulus of TMCP Q550 steel is more serious than that of QT Q550 steel, which can be explained by microstructure.Based on test results, a mathematical model on the mechanical properties of TMCP Q550 steel at elevated temperatures is established.