异步热轧对低合金钢显微组织及力学性能的影响

分别采用同步热轧及异速比为1.2的异步热轧对低合金钢进行热轧,研究异步热轧对低合金钢显微组织及力学性能的影响机制.结果表明,与同步热轧相比,异步热轧可显著促进低合金钢奥氏体/铁素体相变,提高热轧钢板厚度方向的组织均匀性.同步热轧工艺下,钢板表层为细晶铁素体层,厚度1/4或1/2处组织为粗大的贝氏体.异步热轧工艺下,钢板板厚方向主要为均匀的铁素体组织.两种热轧条件下,实验钢的抗拉强度和延伸率相当,分别为710~718 MPa和20%.采用异步热轧代替同步热轧后,实验钢的屈服强度由526MPa提高至561 MPa.这主要是由于同步热轧的钢板相变强化占主导,而异步热轧的钢板细晶强化相对较强.

Effect of Asymmetric Hot Rolling on Microstructure and Mechanical Properties in Low Alloy Steel

The effects of asymmetric hot rolling on the microstructure and mechanical properties of low alloy steel were investigated when the symmetric hot rolling and asymmetric hot rolling with roll velocity ratio of 1.2 were applied to the steel. The results show that asymmetric hot rolling can promote the austenite/ferrite transformation significantly and improve the microstructure uniformity along thickness direction of the steel strip. After the symmetric hot rolling process， the microstructure at the surface of the steel strip was fine ferrite layer and was coarse bainite at the thickness of 1/4 or 1/2. However， the microstructure through the thickness of the steel was the uniform ferrite after asymmetric hot rolling process. The tensile strength and elongation of the steel after these two rolling processes respectively， were very close， which were about 710~718MPa and 20%. After replacing the symmetric hot rolling process by the asymmetric one， the yield strength of the steel increased from 526MPa to 561MPa. The main reason is that the transformation strengthening is dominant in a symmetric hot-rolled steel， but grain refinement is more prominent for asymmetric hot-rolled steel.