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

在Ar、Ar-CO_2和CO_2气氛中，用直径为1.6mm的实芯焊丝，在2.0MPa的绝对压力下焊接低碳钢。研究了环境气体压力和气体成分对电弧现象、合金元素行为和焊缝力学性能的影响，结果表明，提高气室压力会使焊缝外观、焊缝宽度和电弧稳定性降低，特别是在纯CO_2气氛下。在纯Ar焊接气氛中，电极熔化速率随压力的增大而减小。而在CO_2气氛中，随着压力的增加，其值增大。环境压力对Si、Mn、C、Ti的损失没有显著影响。而在Ar-CO_2气氛和CO_22气氛中焊接的焊缝氧含量随压力的增加而增加。焊缝金属的拉伸性能随环境气体成分而变化，但不受气体压力的影响。在CO_2气氛中焊接的焊缝金属，随着压力的增加，CVN韧性下降。在加压氩-CO_2气氛中焊接的焊缝，其韧性随CO_2分压的变化而显著改变。结果表明，焊缝的氧含量是控制CVN韧性的主要因素。

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.