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Butt welding duplex stainless steel butterfly valve, the valve body is 2205 or 2507 duplex steel, when welding with the pipeline, follow the welding process and welding material selection manual. The presence of too much ferrite can cause some problems when welding duplex stainless steel butterfly valves (the heat of the arc causes the atoms in the ferrite matrix to reorder). To do this, the welding material needs to provide more austenite-forming elements, usually 2-4% higher than the base metal Ni. For example, flux-cored wire for welding 2205 stainless steel contains 8.85% Ni.
After welding, the ferrite content in the weld is between 25-55% (and possibly higher). Note: The post-weld cooling rate should be slow enough to allow the austenite to re-form, but not too slow, which will precipitate intermetallic phases, and not too fast, which will generate too much ferrite in the heat-affected zone.
Usually, the austenite phase and ferrite phase in the duplex stainless steel butterfly valve material structure each account for about 50%. The presence of the ferrite phase can improve strength and stress corrosion resistance, while the austenite phase can improve toughness. The combined action of the two phases makes the performance of the duplex stainless steel butterfly valve more excellent. *The most common duplex steel type is 2205: 22%Cr, 5%Ni, 3%Mo and 0.15%N.
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