交流磁场辅助铜-钢TIG填丝焊接头组织和力学性能

Microstructure and mechanical properties of copper-steel TIG filling-wire welding joint assisted by AC magnetic field

通过添加纵向交流磁场,以HS201纯铜焊丝为填充金属,对厚度均为2 mm的T2紫铜和Q235钢板进行TIG对接实验,研究添加磁场时的接头成形、组织结构及力学性能。结果表明:添加磁场后的焊缝表面成形良好。最佳工艺参数为:当焊接电流I E=95 A,焊接速率v=95 mm/min,磁场频率f=25-35 Hz,磁场电流I=0.4-0.6 A,接头力学性能较好,其抗拉强度最高为223.5 MPa,相比无磁场提高了44.5%。铜-钢TIG焊接头主要分为钢侧热影响区、熔合区、焊缝区和铜侧热影响区。添加交流磁场后,钢侧热影响区中的铁素体形态由大块状变为针状和侧板条状;焊缝区组织由胞状晶转变为细密均匀的胞状树枝晶;铜侧热影响区组织明显细化。添加磁场后,接头熔合区和焊缝区的相的种类未发生变化,均由(α-Fe)+(ε-Cu)组成;熔合区的溶质偏析现象得到改善,其(α-Fe)+(ε-Cu)颗粒由粗大的弥散分布状态转变为细小的聚集分布状态;焊缝区组织细化,且其均匀性明显提高,使得接头熔合区与焊缝区的硬度梯度相对减小。

By adding a longitudinal AC magnetic field and using HS201 pure copper wire as the filler metal,TIG butt joint experiments were conducted on T2 copper and Q235 steel plates,both with the thickness of 2 mm,to study the joint formation,organization and mechanical properties when the magnetic field was added.The results show that the surface of weld zone is formed well after adding magnetic field.The best technological parameter is as follows:when welding current I=95 A,welding speed v=95 mm/min,magnetic field frequency f=25-35 Hz,magnetic field current I E=0.4-0.6 A,the mechanical properties of the joint is good,and the maximum tensile strength is 223.5 MPa,which is 44.5%higher than that without magnetic field.Copper-steel TIG welding joint is mainly divided into steel-HAZ,fusion zone,weld zone and copper-HAZ.After the addition of AC magnetic field,the morphology of ferrite in steel side heat affected zone changes from massive to needle like and lateral strip;the microstructure of weld zone changes from cellular crystal to fine and uniform cellular dendrite;the microstructure of copper-HAZ is obviously refined.After adding magnetic field,the types of phases in the fusion zone and weld zone of the joint have no change,which are composed of(α-Fe)+(ε-Cu);the solute segregation in the fusion zone is improved,and the(α-Fe)+(ε-Cu)particles change from coarse dispersion to fine aggregation;the microstructure of the weld zone is refined and its uniformity is obviously improved,which makes the hardness gradient of fusion zone and weld zone relatively decrease.