Duplex stainless steel welding. Best practices

Abstract

Duplex stainless steels have an ex- tensive, successful, track record in a multitude of corrosive and erosive environments up to 315°C (600°F), while providing high immunity to stress corrosion cracking (SCC). Althoughduplex stainless steels are, in many cases, superior in corrosion resistance and strength compared to 304 and 316 austentic stainless steels, many fabricators continue to have difficulties creating welding procedures that yield repeatable weldments with optimum proper- ties. This paper offers practical weld- ing guidelines to new fabricators who want to archieve high quality, robust stainless steel weldments supplementing API 938-C,. Use of Duplex Steels in Oil Refining Industry. Discussion includes the impor- tance of balancing fer- rite to austenite, reducing formation of deleterious intermetallic and nonmetallic phases, measuring fer- rite contents, and suggested welding parameters. 0.03 1.2 0.02 0.035 1.00 24.0-26.0 6.0-8.0 3.0-5.0 0.5 … 0.24-0.32 �41 S32760 Zeron 100 0.03 1.0 0.01 0.03 1.00 24.0-26.0 6.0-8.0 3.0-4.0 0.5-1.0 0.5-1.0 0.30 �40 S32906 Safurex 0.03 0.8-1.5 0.03 0.03 0.50 28.0-30.0 5.8-7.5 1.50-2.60 0.80 … 0.30-0.40 �41 S39274 DP3W 0.03 1.0 0.02 0.03 0.80 24.0-26.0 6.0-8.0 2.50-3.50 0.20-0.80 1.50-2.50 0.24-0.32 42 S39277 AF 918 0.025 … 0.002 0.025 0.80 24.0-26.0 4.5-6.5 3.0-4.0 1.2-2.20 0.80-1.20 0.23-0.33 �41 (a) Single values are maximum (b) PREN = %Cr + 3.3x(%Mo + 0.5x%W) + 16x%N Intermediate-alloy grades (PREN 32-39) S31200 44LN 0.03 2.0 0.03 0.045 1.00 24.0-26.0 5.5-6.5 1.2-2.0 … … 0.14-2.0 33 S31260 DP3 0.03 1.0 0.03 0.03 0.75 24.0-26.0 5.5-7.5 2.5-3.5 0.20-0.80 0.10-0.50 0.10-0.30 38 S31803 2205 0.03 2.0 0.02 0.03 1.00 21.0-23.0 4.5-6.5 2.5-3.5 … … 0.08-0.20 34 S32205 2205+ 0.03 2.0 0.02 0.03 1.00 22.0-23.0 4.5-6.5 3.0-3.5 … … 0.14-0.20 35-36 S32550 255 0.03 1.5 0.03 0.04 1.00 24.0-27.0 4.5-6.5 2.9-3.9 1.5-2.5 … 0.10-0.25 38 S32900 10RE51 0.06 1.0 0.03 0.04 0.75 23.0-28.0 2.5-5.0 1.0-2.0 … … … 33 S32950 7-Mo Plus 0.03 2.0 0.01 0.035 0.60 26.0-29.0 3.5-5.20 1.0-2.5 … … 0.15-0.35 35 Low-alloy grades (PREN <32) S31500 3RE60 0.03 0.2-2.0 0.03 0.03 1.4-2.0 18.0-19.0 4.25-5.25 2.5-3.0 … … 0.05-0.10 28 S32001 19D 0.03 4.0-6.0 0.03 0.04 1.00 19.5-21.5 1.0-3.0 0.60 1.00 … 0.05-0.17 23.6 S32304 2304 0.03 2.5 0.04 0.04 1.00 21.5-24.5 3.0-5.5 0.05-0.60 0.05-0.06 … 0.05-0.20 25 S32404 UR50 0.04 2.0 0.01 0.30 1.00 20.5-22.5 5.5-8.5 2.0-3.0 1.0-2.0 … 0.20 31