Study On Aluminum-deoxidized Wire For CO₂Gas Shielding Arc Welding

Almost all wires in today’s market of welding materials are not in line with theCO₂gas shielded welding of low carbon steels. For example, ER50-6wire is widelyused in the welding of low carbon steel and low strength steel. However, the strengthof deposited metal is much higher than that of base metal because of alloying ofsilicon, manganese and carbon contained in welding wire. Although over-match canincrease the strength of the joint, ductility and toughness are unfavorable. To ensureboth the strength and the toughness, equal match is expected.In this present study, aluminum-containing wires have been made to get equalmatch for the CO₂gas shielded welding of400MPa grade steel. The effects ofaluminum on pore sensitivity, inclusion, mechanical properties （hardness, strength andtoughness） and technological properties （formation of welds, splatter and drop transfer）of deposited metal have been studied by changing the aluminum content （0%¹%） inthe wire.The results showed that: with increasing of aluminum content, pore sensitivity ofwelds reduced obviously; the amount, together with the size of inclusions increasedand most of inclusions in aluminum-containing welds were Al2O3inclusions whileSi-Mn composite oxides were widespread in ordinary welds; the hardness of ordinarywelds was higher than those of aluminum deoxidation welds; with the increase ofaluminum content, the hardness first decreased and then increased, the tensile strengthincreased, the impact toughness first increased and then decreased, the weldpenetration first increased and then decreased while the change of spatter wasreversed; the welding arc was shorter than ordinary arc.When the aluminum content was0.48%, the weld forming was better and thepenetration was deeper than those of other welds. The improvement in impacttoughness was found satisfactory, the hardness and the tensile strength were nearest tothose of base metal. Besides, the arc and current waveform were relatively stable inthe welding process. The weld showed a good overall performance.