焊接电流对TC4钛合金窄间隙TIG焊缝成形及组织的影响

Effect of Welding Current on Weld Formation and Microstructure of TC4 Titanium Alloy Narrow Gap TIG Weld

对30 mm厚的TC4钛合金板材进行窄间隙TIG单层填丝焊试验,研究了焊接电流对焊缝成形的影响,分析了焊接接头的显微组织和显微硬度。试验结果表明:随着焊接电流的增加,焊缝熔深、熔宽增加,焊缝表面下凹程度增大,但是焊缝熔宽增加幅度较小;焊缝区晶粒发生严重粗化,主要为粗大的柱状晶,其显微组织均为针状马氏体α'组织;靠近焊缝区侧的热影响区晶粒比靠近母材侧的粗化程度大。焊接接头显微硬度分布相似,焊缝区硬度稍高于母材硬度,并未存在明显的软化区;峰值硬度出现在热影响区,随着焊接电流增加,热影响区峰值硬度降低。

The narrow gap TIG single layer filler wire welding experiments of 30 mm thick TC4 titanium alloy plate were carried out. The influence of welding current on the weld formation was studied, and the microstructure and microhardness of the welded joints were analyzed. The test results show that with the increase of welding current, the weld depth and weld width increase, and the concave degree of the weld surface increases, while the increase amplitude of weld width is small. The grains of weld zone seriously coarsen, and the grains are mainly coarse columnar crystal, the weld microstructure is acicular martensite or＇ structure. The coarsening degree of grain in heat affected zone near the weld zone is bigger than that of the grain near the base metal. The microhardness distribution of the welded joints is similar. The hardness of weld zone is slightly higher than that of the base metal, and no obvious softening zone exists. The peak hardness is in the heat affected zone. With the increase of welding current, the peak hardness of heat affected zone decreases.