热连轧高强钛合金厚壁管道的TIG工艺及组织和性能

TIG process, microstructure and properties of hot-rolled high-strength titanium alloy thick-walled pipe

针对采用新型的热连轧工艺生产的厚壁高强度无缝钛合金管,通过TIG自动送丝与手工填丝2种焊接方法进行了环缝对接焊工艺试验,对比分析了2种工艺下接头的焊缝成形、微观组织及力学性能。结果表明,2种焊接方法下的焊道表面均呈亮银色,无明显氧化现象,自动送丝接头表面成形更加平滑美观,而手工填丝接头表面成形有不规则的鱼鳞纹;热影响区中β相均发生了一定程度的粗化,并生成了一定量的细针状α’马氏体相。焊缝区组织主要为沿β相界生成的板条状和块状α相,以及晶粒内形成的少量针状α’马氏体组织;TIG自动送丝和手工填丝焊接接头的硬度都是热影响区最高,焊缝最软而母材居中;拉伸试验断裂位置均位于焊缝,平均抗拉强度分别为603.8 MPa和571.7 MPa;热影响区的冲击吸收能量分别达到了41.7 J和78.5 J,手工填丝下的热影响区表现出了比母材更好的冲击韧性。

For the thick-walled high-strength seamless titanium alloy pipe produced by the new hot continuous rolling process, the circular weld butt welding process test was carried out by the two welding methods of TIG automatic wire feeding and manual wire filling, and the joints under the two processes were compared and analyzed from aspects of formation of weld, microstructure and mechanical properties. The results showed that the surface of the weld pass under the two welding methods appeared bright silver without obvious oxidation. The surface of the joint under automatic wire feeding was smoother and beautiful, while the surface of the joint under manual wire filling had irregular fish scales. The β phase in the heat-affected zone got coarsened to a certain extent, and a certain amount of fine needle-like α’ martensite phase formed. The microstructure of the weld zone was mainly lath and block α phases formed along the β phase boundary, as well as a small amount of acicular α’ martensite formed in the crystal grains. Hardness of the TIG joint under both automatic wire feeding and manual wire filling were the highest in the heat-affected zone, hardness of the weld was the lowest and hardness of the base material was in the middle. The tensile test fracture positions all located in the weld, and the average tensile strength was 603.8 MPa and 571.7 MPa respectively. The impact energy absorption of the heat-affected zone reached 41.7 J and 78.5 J respectively, and the heat-affected zone under manual wire filling showed better impact toughness than the base metal.