TWI Industrial Member Report Summary 593/1997
Welding trials using the TIG and CO2 laser processes indicate that superaustenitic stainless steels can be autogenously welded to give excellent pitting resistance.
Austenitic stainless steels offer an attractive combination of corrosion resistance, toughness, ductility and ease of fabrication. The highest alloy grades have become known as 'superaustenitic' steels and may contain 6-7%Mo and up to 0.5%N for excellent pitting corrosion resistance. Welding of older superaustenitic grades is limited by their inability to produce weldments with corrosion resistance matching that of the parent, due to molybdenum segregation in the weld metal and nitrogen loss from the molten weld pool. The conventional approach is to use an overalloyed nickel-based filler. However, problems may arise due to a tendency for corrosion at the fusion line unmixed zone when such a filler type is used. This project was undertaken to examine corrosion resistance of autogenous weldments, both in an established grade, ie S31254, and also in two recently developed superaustenitic steels with 0.5% nitrogen, ie UNS S34565 and S32654.
- To quantify and optimise corrosion resistance of autogenous weldments in new high nitrogen superaustenitic stainless steels, made using the TIG and CO2 laser welding processes.