Application of 2205 Duplex Stainless Steel in Pharmaceutical and Biotechnology

2205 Duplex Stainless Steel Machining characteristics

The machining of 2205 duplex stainless steel is similar to that of 316L, but there are still some differences. Cold forming operations must take into account the higher strength and higher work hardening properties of duplex stainless steels. Forming equipment may require higher load capacities, and in forming operations, 2205 stainless steel will exhibit higher resilience than standard austenitic stainless steels. The higher strength of 2205 duplex stainless steel makes it more difficult to machine than 316L.

The welding of 2205 duplex stainless steel can use the welding method of 316L stainless steel. However, heat input and interpass temperature must be tightly controlled to maintain the desired austenite-ferrite phase ratio and avoid precipitation of detrimental intermetallic phases. A small amount of nitrogen in the welding gas helps avoid these problems. When performing welding procedure qualification for duplex stainless steels, the commonly used method is to use a ferrite meter or to evaluate the austenite-ferrite ratio by metallographic examination. The presence of deleterious intermetallic phases is usually verified using the ASTM A 923 test method.

The recommended filler metal for welds is ER2209 (UNS S39209, EN 1600), and self-fusion welding without filler metal is only used if the weld can be solution annealed after welding to restore corrosion resistance. For solution annealing, the part is heated to a temperature of at least 1040°C and then rapidly cooled.

Duplex stainless steel such as 2205 has poorer penetration and fluidity than 316L stainless steel, so the welding speed is slower. Because 2205 duplex stainless steel has poor penetration, it is necessary to modify the shape of the joint. 2205 duplex stainless steel requires a wider bevel angle, larger root clearance and less blunt edge than 316L stainless steel in order to obtain a full penetration weld.

Orbital welding of 2205 stainless steel pipe is possible with 2209 filler wire if the welding equipment allows the use of filler wire. Instead of filler wire, it is also possible to use consumable slugs suitably over-alloyed in composition.

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Application of 2205 Duplex Stainless Steel in Pharmaceutical and Biotechnology

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