预处理组织对低碳钢IQ&P工艺下组织及性能影响

采用γ单相区和γ+α双相区轧制并淬火工艺以及双相区再加热-淬火-碳配分( IQ&P)工艺,研究预处理组织对低碳钢室温状态多相组织特征及力学性能的影响规律. 实验用低碳钢经两种工艺轧制并淬火处理,获得马氏体和马氏体+铁素体的预处理组织,再经双相区IQ&P工艺处理后均获得多相组织. 马氏体预处理钢的室温组织由板条状亚温铁素体、块状回火马氏体以及一定比例的针状未回火马氏体和8. 2%的针状残余奥氏体组成;马氏体+铁素体预处理钢由板条状亚温铁素体、块状和针状未回火马氏体以及14. 3%的短针状或块状残余奥氏体组成. 在相同的双相区IQ&P工艺参数下,预处理组织为马氏体的钢抗拉强度为770 MPa,伸长率为28%,其强塑积为21560 MPa·%;而预处理组织为马氏体+铁素体的钢抗拉强度为834 MPa,伸长率增大到36. 2%,强塑积达到30190 MPa·%,获得强度与塑性的优良结合.

Effect of pretreated microstructure on the morphology and mechanical properties of low-carbon steel with IQ&P treatment

The effects of pretreated microstructure on the multiphase microstructure features at room temperature and the mechani-cal properties of low-carbon steel were studied by the treatment of water cooling after hot-rolling in the γ phase region or in the γ+αphase region followed by the treatment of intercritical reheating-quenching-partitioning ( IQ&P) . Two different pretreated microstruc-tures, which are martensite and martensite + ferrite, are obtained by the two different hot-rolling and quenching processes. After IQ&P, the steel with martensite as pretreated microstructure, in which the volume fraction of retained austenite is 8. 2%, is turned into a multi-phase structure composed of lath intercritical ferrite, block tempered martensite, needle-like untempered martensite, and retained austenite. While the steel with martensite + ferrite as pretreated microstructure, in which the volume fraction of retained austenite is 14. 3%, is turned into a multi-phase structure composed of lath intercritical ferrite, block or needle-like untempered martensite, and short needle-like or block retained austenite. With the same IQ&P process parameters, the tensile strength of the steel with martensite as pretreated microstructure is 770 MPa, the elongation is 28%, and the product of strength and elongation is 21560 MPa·%. While the tensile strength of the steel with martensite + ferrite as pretreated microstructure is 834 MPa, the elongation increases to 36. 2%, and the product of strength and elongation reaches to 30190 MPa·%. In other words, the steel has obtained a good combination of strength and ductility.