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Ferrite is important in avoiding hot cracking in during cooling from welding of austenitic stainless steels. The Schaeffler and Delong diagrams are the original methods of predicting the phase balances in austenitic stainless steel welds.
Maximum breaking torque values for property class 50, 70 and 80 austenitic fastener grades A1, A2, A3 A4 and A5 taken from BS EN ISO 3506-1 are shown. A link is provided to the Bulten Stainless web site where maximum tightening torque, yield load and failure load for austenitic stainless steel fasteners are tabulated.
An overview of welding stainless steels is given, with particular reference to the various welding methods that can be used. These include Gas Tungsten Arc Welding, (GTAW or TIG), Plasma Arc Welding, (PAW), Shielded Metal Arc Welding, (SMAW or MMA), Gas Metal Arc Welding, (GMAW or MIG / MAG), Flux Cored Arc Welding, (FCAW or FCW), Submerged Arc Welding, (SAW), Electric Resistance Welding, (ERW), Laser Welding. Standards mentioned include BS EN 1600, BS EN 12072, BS EN 12073, BS EN 760, BS EN 287 Part1, (Approved testing of welders for fusion welding), BS EN 288 Part 3, Welding Procedure tests for the arc welding of steels.
An overview of the skills required in welding stainless steel
Austenitic stainless steels are readily welded and widely used in fabrications. Ferritic, martensitic and austenitic-ferritic grades can also be welded but require more control. General guidelines on welding are given, including the need to avoid excessive heat input and to avoid contamination from contact with carbon steels.
Welding austenitic stainless steels to carbon and low alloy steels are established methods in the process and construction industries. Over-alloyed fillers are used to avoid dilution of the parent stainless steel in the fusion zone. Filler type 308 can be used for joining a 304 type ‘parent’ to a carbon steel but more highly alloyed fillers, such as the 309 type are preferable. There should be no risk of post weld bimetallic, (galvanic), corrosion, if the joint is repainted.
The optimisation of corrosion resistance and cleanability through the use of Automatic Penetration Control. Author – Ko Buis of Van Leeuwen Stainless. Reprinted from Stainless Steel World July/August 2007.