1000 MPa级高强钢熔敷金属强韧化机理分析

Analysis of the strengthening and toughening mechanism of deposited metal of 1000 MPa grade high strength steel

自主设计4种不同镍含量(ω_(Ni))的Ni-Cr-Mo系焊丝,采用TIG焊制备1000 MPa级高强钢熔敷金属.利用光学显微镜、扫描电子显微镜、透射电子显微镜、X射线衍射仪等对不同镍含量的熔敷金属微观组织进行表征,通过拉伸、冲击、硬度试验对熔敷金属力学性能进行测试,探求镍含量对1000 MPa级高强钢熔敷金属强韧性机理的影响规律.结果表明,不同镍含量熔敷金属组织均由板条马氏体、板条贝氏体、联合贝氏体和残余奥氏体组成;镍含量不同,微观组织不同;随着镍含量增加,柱状晶宽度增大,板条马氏体、联合贝氏体和残余奥氏体增多,板条贝氏体减少,熔敷金属强度提高,塑性降低;当ω_(Ni)为5.44%时,强韧匹配最佳,屈服强度为1005 MPa,−50℃下冲击吸收能量为95 J.创新点:阐明了1000 MPa级海工用钢熔敷金属强韧化机理,揭示镍含量对1000 MPa级熔敷金属强韧化机理的影响.

Four kinds of Ni-Cr-Mo wire with different Ni contents were designed,with which the deposited metal of 1000 MPa high strength steel was prepared by TIG welding.Optical microscope,scanning electron microscope,transmission electron microscope,and X-ray diffractometer were used to characterize the microstructure of the deposited metal with varying Ni contents.The mechanical properties of the deposited metal were tested in terms of tensile,impact and hardness to investig-ate the influencing mechanism of varying Ni contents on the strength and toughness of deposited metal of 1000 MPa high strength steel.The results show that the microstructure of the deposited metal,though with different Ni contents,is composed of lath martensite,lath bainite,combined bainite and retained austenite.Different Ni contents result in different microstructures.With the increase of Ni contents,the width of columnar grains grows,the number of lath martensite,combined bainite and retained austenite also increases,and the number of lath bainite decreases,which have enhanced the strength but weakened the plasticity of the deposited metal.When the Ni content is 5.44%,the strength-toughness matching is optimal,with the yield strength reaching 1005 MPa,and the impact energy is 95 J at−50℃.Highlights:The strengthening and toughening mechanism of 1000 MPa offshore steel deposition metal was explicated,and the influencing mechanism of Ni content on the strength and toughness of 1000 MPa deposited metal was revealed.