N和O元素引入对GPCA-TIG焊焊缝冲击韧性的影响

通过外层气体引入O和N元素,气体熔池耦合活性TIG焊(gas?pool?coupled?activating?TIG?welding)可以实现深熔深、高质量和连续焊接.?为了研究清楚O和N元素引入对焊缝冲击韧性的影响规律和机理,针对SUS304不锈钢分别测试了外层气体为O2,N2和O2?+?N2时的焊缝低温冲击韧性,并...

Effects of introductions of oxygen and nitrogen elements on impact toughness of gas pool coupled activating TIG weld metal

Through introducing oxygen and nitrogen elements from the outer gas of gas pool coupled activating TIG(GPCA-TIG) welding, deep penetration, high quantity and continuous welding are accessible. In order to obtain the dependence and mechanism of weld metal impact toughness on the introduced oxygen and nitrogen elements, GPCA-TIG welding for stainless steel SUS304 with the outer gases oxygen, nitrogen and nitrogen-oxygen gas mixture respectively were performed to gauge low temperature impact toughness of the weld metal. Then, a series of testing experiments including weld microstructure and chemical composition, nonmetallic inclusion and grain orientation were conducted. The results reveal that, the introduction of oxygen makes the low temperature impact toughness of weld metal decease obviously, nitrogen decease a little, while the low temperature impact toughness of weld metal can be increased a little conversely when oxygen and nitrogen are synchronously introduced. The main mechanism is proven that the synchronous introduction of oxygen and nitrogen elements leads to fine grain of weld microstructure, less increases of the contents of oxygen and nitrogen elements and the nonmetallic inclusions, much decrease of ferrite number in weld metal. Meanwhile, the high angle grain boundary number in austenite crystal and the matching property of grain orientations between ferrite and austenite are improved. All of these result in difficult cracking propagation and higher toughness.