高韧性海洋平台用钢E550-Z35的开发

Development of high toughness E550-Z35 steel plate for offshore platforms

通过理论分析设计了海洋平台用钢E550-Z35的成分体系,制定了两段轧制工艺。粗轧阶段采用大扭矩以减少轧制道次增加压下量,精轧开轧温度在900℃以下。通过未再结晶区的低温大变形诱导铁素体机制细化奥氏体晶粒。试验钢淬火温度设定为930℃,回火温度设定为650℃。淬火态显微组织为板条状马氏体,回火后显微组织为回火索氏体,50 mm厚钢板回火后上屈服强度670～700 MPa,抗拉强度720～750 MPa,断后伸长率18%～20%,-40℃冲击吸收能量在200 J以上,Z向拉伸断面收缩率在50%以上,满足船级社规范对E550-Z35的各项性能要求。

Chemical composition of E550-Z35 steel was designed through theoretical analysis.Based on its chemical composition,a two-stage rolling process was determined.In the process of rough rolling,high torque is used to reduce the roll pass and increase press quantity.The finish rolling initial temperature is below 900 ℃,and grain is refined through the decrease of rolling temperature and large strain accumulation.The quenching temperature was selected to be 930 ℃ and the tempering temperature to be 650 ℃.The microstructure is lath martensite after quenching and tempered sorbite after tempering.After tempering the yield strength and tensile strength can reach 670-700 MPa and 720750 MPa,respectively,the elongation can reach 18%-20%,the impact absorbed energy at-40 ℃ is more than 200 J,and the Z-direction reduction of area is more than 50%.The mechanical properties of E550-Z35 steel plates meet the classification society standards.