热输入对800MPa级超厚板窄间隙焊缝金属组织和性能的影响

Effect of heat input on the microstructure and properties of weld metal welding in a 800 MPa grade heavy steel plate with narrow gap groove

采用三种热输入进行超厚板窄间隙熔化极气体保护焊,借助金相显微镜、扫描电子显微镜及附带EDS系统和透射电子显微镜研究了热输入对焊缝金属组织和性能的影响.结果表明,三种热输入焊缝金属组织主要由板条马氏体、无碳化物贝氏体、M-A组元和残余奥氏体组成.随着焊接热输入的增加,焊缝组织中马氏体含量减少;也使无碳化物贝氏体形核率降低,造成无碳化物贝氏体粗化.并且当贝氏体相变时热输入的增加使碳原子扩散距离变远,促使残余奥氏体形状由膜状向块状转变.另外随着热输入的增加,焊缝金属强度下降,而冲击韧性对热输入不敏感.

The heavy steel plates with narrow gap groove were welded by gas metal arc welding under three heat inputs,and the effects of heat input on microstructure and properties of the weld metal were investigated by means of optical microscopy,scanning electron microscopy with energy dispersive spectroscopy,and transmission electron microscopy.The results indicate that the microstructure of the three weld metal consist predominantly of lath martensite,carbide free bainite,M-A constituent and retained austenite.The amount of martensite decreases with the increasing of the heat input.As the heat input increases,bainite nucleation rate decreases,resulting in coarser bainite,and C diffuses the farther distance,resulting in variation of retained austenite morphology from strip to block.The strength of weld metal drops with the increasing of heat input,while the toughness is not sensitive to heat input.