How straightforward is super duplex welding? Stainless Steels
Super duplex stainless steels have historically been considered difficult to weld. Incorrect welding conditions can lead to a change in the balance of austenite:ferrite, and also lead to the creation of deleterious intermetallic phases. Both phenomena can result in lessened corrosion resistance and impact toughness.
If subjected to temperatures between 450degC and 900degC for enough time, super duplex stainless steels can form several harmful intermetallic phases, including sigma phase. These chromium-rich regions result in areas where the chromium is denuded, which are subsequently prone to pitting corrosion.
To avoid the formation of sigma phase, the power input should be carefully controlled. Also the time between multi-pass welds should be sufficient to prevent the weld region spending too long at too high a temperature. ‘Over-matched’ weld fillers, containing a greater level of nickel, will also help to maintain a desirable balance between austenite and ferrite.
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If you have any more questions about austenitic or duplex stainless steels, please contact us today. A member of our team will be more than happy to help and can also advise you on the best option for your application.