The welding of experimental low-nickel Cr-Mn-N stainless steels containing copper

• Published in: Journal of the South African Institute of Mining and Metallurgy 1996-05, Vol.96 (3), p.99-108
• Main Authors: Coetzee, M, Pistorius, P G H
• Format: Article
• Language: English
• ISSN: 0038-223X

The susceptibility of experimental low-nickel Cr-Mn-N stainless steels to hot cracking, sensitization, and pitting corrosion in the as-welded condition was investigated. These steels were developed for deep-drawing applications and are similar in composition to type 201 stainless steel. In order to obtain good formability, the rapid rate of work-hardening (characteristic of the 200-series steels) was decreased by the addition of copper. The behavior of two sets of alloys during fusion welding was investigated: 17Cr-7Mn-4Ni-0.5Cu steels containing 0.001-0.27% nitrogen, and 17Cr-7Mn-2Ni-0.1N steels with Cu contents varying between 0.01 and 3.11%. All the steels in these two sets initially solidify as delta -ferrite, which transforms partially to austenite during cooling. As the N level increases, the microstructure of an autogeneous-weld metal ranges from large amounts of delta -ferrite, martensite, and Widmanstatten austenite, to austenitic structures with small amounts of vermicular delta -ferrite. The formation of delta -ferrite during solidification and the presence of ferrite retained in the weld metal indicate that the experimental alloys will not be susceptible to hot cracking during welding. Except for the alloy with 0.27% N, the resistance to pitting corrosion of the experimental steels in the as-welded condition is inferior to that of type 304 stainless steel. None of the experimental steels is susceptible to intergranular attack in the as-welded condition. The alloys with 0.19 and 0.27% N have properties (corrosion and microstructure) similar to those of type 304 stainless steel in the as-welded condition.