| A series of study using Argon/CO₂ gas mixture in shielded gas welding was carried out to overcome some difficulties in CO₂-arcwelding or MIG-welding. In this paper, single bead was performed on mild steel and low alloy steel pipes using bare electrode and CO₂ and Argon, singly or mixed, as shielding gas. The mode of metal transfer, bead shape, blow holes, chemical composition and non-metallic inclusions of weld metal, further, V-Charpy impact value of weld metal were investigated on these metal. The results obtained are as follow: 1) With increasing Argon content, the mode of metal transfer was observed to be of Spray transfer type. In the range of Ar 40% per CO₂60%-Ar 60% per CO₂ 40%, the mode of transfer is observed to be a combination of spray and globular types. 2) The penetration depth with increasing Argon content decreases and the bead shape factor (W/P) increases. The flank angle (θ) decreases a little with increasing CO₂ content. 3) If the welding is performed with appropriate shielding gas under appropriate welding conditions, the welding defects (mainly blow holes) hardly occurs. 4) The carbon content of deposited metal is not affected by change in Ar/CO₂ composition of shelding gas, but the contents of silicon and manganese decrease with increasing CO₂. The Chromium and molybdenum contents hardly depend on the composition of shelding gas in the case of low alloy steel. 5) The non-metallic inclusions hardly depend on the composition of shielding gas. 6) The V-Charpy Impact value is practically not affected by the shielding gas composition for mild steel but decreases a little with increasing Argon content in the case of low allay steel. |
|
