Superduplex Heat-Affected Zone Optimization
The process-technical control of heat input during welding to prevent a critical drop in the austenite fraction in the heat-affected zone. Correct cooling rates ensure phase integration.
Superduplex steels are highly alloyed and need to be treated cleanly when welding. The trick is to keep the microstructure in balance – too much heat or too slow cooling will tip the ferrite-to-austenite ratio, and then it gets hard and cracky. You have to control the cooling so that enough austenite reforms, but not so much that you get other problems. Keep the interpass temperature under control and don't let the part cool down before the weld is finished. If you want to mess up the structure, just heat it up too much – then you'll have a hard, brittle notch instead of a tough weld.