Mechanical and microstructural properties of ultra-low carbon bainitic steel weld metal
Because of its reduced susceptibility to cracking, Ultra-Low Carbon Bainitic (ULCB) steel weld wire is being investigated as a consumable for Gas Tungsten Arc (GTA) and Gas Metal Arc (GMA) welding of Navy high strength (100 ksi) steels. In the present work, a candidate ULCB weld wire was investigated for GTA and GMA welding processes as a function of both welding power and cover gas. The strength and Charpy V-notch toughness of the resulting welds was investigated. It was found that the GTA weld using 100% argon cover gas had excellent toughness (well above Navy requirements), but the strength was at the minimum specification. The GMA welds using a cover gas of 95% argon - 5% CO2 (C5) showed the opposite trend in that they were well within the range of strength specifications, but their toughness was unsatisfactory. Chemical, mechanical and microstructural studies of these welds were performed. GMA welds using C5 cover gas had a higher weld metal.
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Monterey, California. Naval Postgraduate School