双相不锈钢水下局部干法TIG焊接工艺

Underwater Local Dry TIG Welding of Duplex Stainless Steel

为改善水下焊接环境,提高焊缝质量,研究适合水下焊接的TIG焊枪及其焊接方法。研制一把双层气体保护的小型可移动气罩式水下TIG焊枪,对2507双相不锈钢进行焊接,研究焊接工艺参数对焊接质量的影响。结果表明,当内气流量10L/min,外气流量5L/min时,焊缝成形最好,焊缝深宽比最大;保证内、外气流量不变,增大焊接电流会降低熔池稳定性,但电流过大时,电弧受到内喷嘴和内保护气的约束作用,会使得焊缝熔深和深宽比增加;同时发现脉冲焊接在水下环境中可以增加电弧稳定性。对水下、陆上焊接接头对比分析发现,水的快速冷却作用会促使铁素体晶粒内析出的奥氏体形状由针状转变为粒状,奥氏体相的析出方式由晶界转为晶内,并且奥氏体析出相减小,晶粒细化。试验证实,此焊枪可以实现水下TIG的稳定焊接,通过选择合适的焊接参数,能获得与陆上环境性能相似的焊缝,对于水下焊接维修有着重要意义。

To improve the underwater welding environment and weld quality, a small portable underwater TIG welding torch with movable gas hood is developed. With the double gas shielded welding torch, the influence of welding parameters on weld quality of 2507 duplex stainless steel is studied. The results show that when the internal gas flow rate is 10 L/min and the external gas flow rate is 5 L/min, the weld formation is the best and the depth-width ratio is the largest. When the internal and external gas flow are kept constant, the stability of the molten pool is reduced with increasing welding current. But when the welding current is too high, the welding arc may be restrained by the inner nozzle and the protective gas, which increases the penetration depth and depth-width ratio.It is also found that pulsed welding can increase the arc stability under the water environment. The comparative analysis of the underwater and onshore weld joints shows that the rapid cooling of water is conducive to the change of austenite precipitated on ferrite from needle to granular-like and from grain boundary precipitation to intragranular precipitation. At the same time, the austenite precipitated phase is decreased and the grain is refined. The test proves that this welding torch can realize the stable welding of underwater TIG. By selecting the appropriate welding parameters, the weld with similar performance to onshore environment can be obtained, which is of great significance for underwater welding maintenance.