活性化TIG焊熔深增加机理的研究

以不锈钢0Crl8Ni9为实验对象，涂敷含有Bi的SiO2和TiO2活性剂，通过1mm厚高熔点薄钨板挡住熔池流动的方法进行焊接实验．对钨板两侧Bi颗粒的分布进行了测试，分析涂敷SiO2和TiO2后熔池流动方向的变化，同时采集了电弧电压．结果表明：活性剂SiO2和TiO2改变了熔池的流动方向；SiO2使电压提高约4．2V，而TiO2对电弧电压没有影响；活性剂并未使电弧整体发生收缩，而使电弧整体发生了膨胀；SiO2使等离子体发生了收缩；电弧等离子体收缩和电弧导电通道变长是SiO2活性剂提高电弧电压的主要原因．分析认为，SiO2增加熔深是等离子体收缩、阳极斑点收缩和表面张力温度梯度由负变正共同作用的结果；TiO2增加熔深只是表面张力温度梯度由负变正的作用．

MECHANISM OF INCREASING A-TIG WELDING PENETRATION

By using an 1 mm thick tungsten plate blocking the flow of molten metal, welding was performed on three specimens of 0Cr18Ni9 coated with active additions containing Bi, SiO2 and TiO2. The distributions of Bi after adding SiO2 and TiO2 at the both sides of the tungsten plate were measured, and the arc voltages are collected. The results show that additional SiO2 and TiO2 change the flow direction of the melting metal. Arc voltage increased 4.2 V due to adding SiO2, whereas no change occurs when adding TiO2. The active flux doesn't make the arc wholly constrict, but inflate. SiO2 leads to the constriction of plasma. Thus, the main reason of SiO2 increasing arc voltage is plasma constriction and the increase in length of electrical path. Improvement of penetration by SiO2 is resulting from plasma constriction, anode spot constriction and the change of surface tension temperature coefficient instead of arc constriction. However, the mechanism improving penetration by TiO2 is only the change of surface tension temperature coefficient.