Gas-Metal-Arc Welding of Mild Steel in Pressurized Atmosphere

用直径1.6 mm的实心焊丝在加压Ar、Ar-CO_2和CO_2气氛中焊接低碳钢，绝对值压力高达2.0 Mpa。研究了环境气体压力和气体成分对电弧现象、合金化元素行为和焊缝力学性能的影响。当气压增加时，尤其是在纯CO2气氛下，室内压力会降低焊缝的外观、宽度和电弧稳定性。在纯Ar焊气氛下，电极熔化速度随压力的增加而降低。相反，在CO_2气氛中，随着压力的增加，温度升高。环境压力对硅、锰、碳、钛的损失没有显著影响。但在Ar-CO_2气氛和CO_22气氛下焊接的焊缝的氧含量随着压力的增加而增加。焊缝金属的拉伸性能随环境气体成分的变化而变化，但不受气体压力的影响。CO_2气氛下焊缝金属的CVN韧性随压力的升高而恶化。CO_2分压对加压Ar-CO_2气氛下焊接接头的韧性有显著影响。结果表明，CVN韧性受焊缝含氧量的控制。

Mild steel was welded in pressurized Ar,Ar-CO_2 and CO_2 atmospheres at pressure of up to 2.0MPa absolute,using a 1.6 mm diameter solid wire. The effects of ambient gas pressure and gas compositions on the arc phenomena, behaviour of alloying elements and mechanical properties of welds were studied.Chamber pressure when increased acts to reduce appearance, weld width and arc stability,especially under pure CO_2 atmosphere. In pure Ar welding atmosphere,the electrode melting rate decreases with increasing the pressure. On the contrary,in CO_2 atmosphere,it increases with the increase of the pressure. The ambient pressure has no significant influence upon the loss of Si,Mn,C,Ti. But the oxygen content of weld made in Ar-CO_2 atmosphere and CO_22 atmosphere increases with increasing the pressure. The tensile properties of weld metals are varied with the ambient gas composition but are not affected by the gas pressure. CVN toughness of weld metals made in CO_2 atmosphere are deteriorated at increased pressure. The toughness of welds made in pressurized ar-CO_2 atmosphere are changed markedly by CO_2 partial pressure. It suggested that the CVN toughness are controlled by the oxygen content of welds.