高圧ＣＯ?S２?T溶接ふん囲気中での鋼のアーク溶接現象

Abstract

Mild steel was welded in CO2 atmospheres at pressures between 1 and 6 Kg/cm2 abs. using an electrode wire of 1.6 mm diameter, commercially available for CO2 arc welding, in order to study the effect of ambient gas pressure on the characteristics of an arc, the mode of metal transfer, the geometry, composition and hardness of weld beads and so on.The results obtained are summarized as follows:(1) In welding under a shorting-arc condition at 22.5V, 250A, (a) the maximum arc voltage increases and the duration of short circuiting becomes longer with an increasing ambient gas pressure;(b) the ambient gas pressure has no significant influence on the melting rate of an electrode wire and the chemical composition of weld metals;(c) the hardness of weld metals increases with an increasing ambient gas pressure; and(d) the reinforcement of welds increases with an increasing ambient gas pressure.(2) In welding under a droplet transfer condition at 35V, 350A, (a) the melting rate of an electrode wire increases with an increase in the ambient gas pressure; (b) the arc voltage during welding under high pressure atmospheres appears in waves at intervals of some 25Hz, accompanied with many small fluctuations in a wave;(c) the ambient gas pressure has no significant influence on the chemical composition of weld metals;(d) the hardness of weld metals decreases with an increasing ambient gas pressure; and(e) the reinforcement and penetration depth of weld metals increase with an increasing ambient gas pressure.(3) In welding with 4 mm arc length under a droplet transfer condition at 350A, (a) manganese and silicon contents of weld metals decrease with an increasing ambient gas pressure;(b) the arc voltage during welding under high pressure atmospheres appears in waves in the same manner 35V, 350A; and(c) the hardness of weld metals decreases with an increase of the ambient gas pressure;(4) No porosity was observed in the weld metals made in the pressurized CO2 atmospheres.