LNG船用因瓦合金脉冲TIG搭接仰焊工艺研究

采用搭建的薄板搭接仰焊系统进行1.5/0.7mm因瓦合金搭接脉冲TIG仰焊位置焊接,测试和分析焊缝宏观成形、微观组织和力学性能。研究结果表明,焊缝特征尺寸La(焊接长)与P(熔深)随脉冲峰值电流增加而明显增加,但R(焊喉)随峰值电流变化不明显。焊缝区由具有胞状晶亚结构的粗大奥氏体柱状晶组成,热影响区由粗大的等轴晶组成,熔合区由平面晶区和半熔化区构成。热影响区硬度明显低于焊缝和母材,接头最大拉伸承载力均为约4300N,所有接头断裂位置均在熔合区。

Study on pulsed TIG lap welding of Invar alloys in overhead position for LNG carrier

1.5 mm and 0.7 mm Invar sheets are lap-jointed by pulsed tungsten inert gas (pulsed TIG) welding in overhead position. The macro morphology,microstructure and mechanical properties of the lap joints are investigated. The results show that when the peak current increase,the characteristic dimensions La and P obviously increase and R rarely change. The weld metal (WM) zone is composed of coarse austenitic columnar crystal with cellular substructure,and the heat affected zone (HAZ) is composed of coarse equiaxial crystal. The plane grained region and partial melting region constitute the bond,which is the weakest region in the joint. Microhardness tests reveal that the microhardness value of HAZ is less than that of WM and base metal. The maximum tensile shear force of all samples is approximately 4 300 N,and all fractures are located in bond.