Al含量及热处理对冷轧TRIP钢板组织与性能的影响

Influence of Al content and heat treatment on microstructure and properties of cold rolled TRIP steel

以Al含量分别为0.86%和1.5%的两种不采用Si合金化的冷轧TRIP钢为对象,研究Al含量和热处理工艺对其显微组织与力学性能的影响规律。结果表明,在两相区保温使铁素体与奥氏体体积分数相当后,在370～450℃的贝氏体区等温均得到包括铁素体、贝氏体、残留奥氏体和马氏体的多相组织。由于Al起到了有效的稳定奥氏体作用,含Al较高的1.5Al钢的残留奥氏体体积分数及其碳含量均高于0.86Al钢。力学性能试验结果表明,1.5Al钢的最佳性能是屈服与抗拉强度分别为452MPa和756MPa,伸长率达到34%,对应的热处理工艺是850℃×300s快冷到400℃等温180s。而0.86Al钢在最佳工艺(800℃×300s后370℃等温180s)下的强度与伸长率均明显低于1.5Al钢,屈服与抗拉强度分别为413MPa和708MPa,伸长率仅为27%。

Two kinds of Si-free cold rolled TRIP steels containing 1.5% Al and 0. 86% Al were studied. The influences of Al content and heat treatment on microstructure and mechanical properties were investigated. The muhiphase structures consisting of ferrite, bainite, retained austenite and martensite are obtained by intercritical annealing followed by isothermal bainitic transformation at 370 -450℃. The addition of Al increases the stability of austenite, and therefore the volume fraction and carbon content of the austenite of 1.5Al steel are higher than that of 0. 86Al steel. The optimal property of 1.5 Al is obtained by holding 300 s at 850 ℃ followed by 180 s at 400 ℃ ,the yield and tensile strength and elongation are 452 MPa ,756 MPa and 34% , respectively. The optimal property of 0. 86Al steel is obtained by holding 300 s at 800℃ followed by 180 s at 370 ℃ ,and the strength and elongation are 413 MPa,708 MPa and 27% ,which are inferior to 1.5Al steel.