980MPa级冷轧双相钢组织性能研究

为研究980 MPa级C-Si-Mn-Nb系冷轧双相钢组织性能,在试验室冶炼该钢并采用临界区保温+两段式冷却+过时效处理的工艺进行热处理。研究表明,试验钢的屈服强度为476 MPa,抗拉强度为1 021 MPa,伸长率为15%,n值为0.29;试验钢热轧组织为(F+P),铁素体晶粒尺寸约为3.3μm;退火组织为(F+M),马氏体体积分数约为63%。微合金元素Nb的添加,起到细晶强化和析出强化的作用。与热轧组织相比,连续退火板带状组织得到明显改善,试验钢表现出良好的强韧性匹配。

Study on Microstructure and Mechanical Properties of 980 MPa Cold Rolled Dual Phase Steel

980 MPa cold rolled dual phase steel with C-Si-Mn-Nb has been developed in laboratory and heat treatment is made by the process consisting of steps such as warm-keeping in critical zone,two-stage cooling and overageing treatment in order to study the microstructure and mechanical properties of the said steel.The results show that these values of the yield strength,tensile strength,elongation,strain hardening exponent of the said steel are 476 MPa,1 021 MPa,15%,0.29,respectively.The microstructure of the hot-rolled steel is composed of ferrite and pearlite,in which the grain size of the ferrite is approximately 3.3 μm.While the microstructure of the annealed steel is composed of ferrite and martensite,in which the volume fraction of martensite is 63%.Microalloying Nb acts as the refining crystal grains and precipitation strengthening.Compared with the microstructure of the hot-rolled steel,the banded structure in the continuously annealed steel sheet is greatly improved,indicating that the experimental steel has an excellent balance between strength and toughness.