多层多道焊接DH40船用钢接头组织及力学性能

Structure and mechanical properties on DH40 ship building steel joints by multi-layer and multi-pass welding technology

使用药芯焊丝CO2焊,在多层多道焊条件下对大厚板DH40船用钢进行了焊接试验,并较为系统研究了接头组织及力学行为,重点探讨了焊接接头冲击韧性尤其是焊缝根部热影响区熔合线外5 mm区域冲击韧性严重衰减的原因.结果表明,焊接接头抗拉强度均高于母材,(大于母材抗拉强度515 MPa).弯曲试验所有样品均合格,满足塑性要求;采用CO2气体保护焊多层多道焊接DH40船用钢,易在焊缝根部热影响区熔合线外5 mm左右的狭窄范围内出现脆性带.其中"组织遗传"作用,造成晶粒粗大,是其冲击韧性下降的次要因素,该区域产生大量粒状贝氏体,是其冲击韧性严重衰减的根本原因.

The weldability experiments of DH40 ship building steel were carried out by using the flux-cored wire CO2 gas shielded multi-pass welding technology.The microstructure and mechanical properties of the joint were studied systematically and the impact toughness was discussed,especially the reason why the impact toughness at HAZ of 5 mm from fusion line of weld root decreased greatly.The results showed that the tensile strength of joints is higher than that of the base metal of 575 MPa.All the samples used in the bending test are qualified and meet the plasticity requirement.The brittleness band is easily formed at HAZ,5 mm from the fusion line at the weld root.The effect of microstructure heredity results in the coarse crystal grain,which is the secondary reason for the impact ductility decreasing,and the basic reason is the formation of a large amount of granular bainite.