Arc Welding of Mild Steel in Pressurized Ar and Ar-20%CO₂ atmospheres

Abstract

Mild steel was welded in pressurized Ar, Ar-20%CO₂ and CO₂ atmospheres in the pressure range from 0.1-2.0 MPa abs. using a solid wire of 1.6 mm dia.. The effects of ambient pressure on the melting rate of electrode wire, the geometry of weld metal and the behaviour of alloying element during the arc welding process were studied.
The results obtained are as follows:
1) In Ar atmosphere, the melting rate of an electrode wire decreases with the increase of pressure. On the contrary, in CO₂ atmosphere, it increases with the increase of pressure.
2) In each atmosphere, the penetration width decreases, and penetration depth increases with the increase of ambient pressure.
3) Except for manganese, the loss of alloying elements during the arc welding process is little in pressurized Ar atmosphere.
4) In pressurized Ar-20%CO₂ and CO₂ atmospheres, Si, Mn, Ti loss are observed during the arc welding process.
5) The decrease rate of alloying elements depend on the CO₂ partial pressures at a same ambient pressure.
6) In pressurized Ar-20%CO₂ and CO₂ atmospheres, the oxygen content of weld metal increases with increasing the pressure.
7) The oxygen content of weld metal made in Ar-20%CO₂ atmosphere is lowre than made in pure CO₂ atmosphere at a same CO₂ partial pressure.