The excellent combination of strength and corrosion resistance in duplex stainless steels is due to their strict composition control and microstructural balance. The loss of these properties is an important consequence of secondary phases precipitation and unbalanced microstructure, due to thermal cycles and rapid cooling caused by the welding process. To ensure an optimized and well- controlled microstructure, a post-welding heat treatment is generally performed. This heat treatment usually consists in a heating up to a temperature higher than 1000 °C, followed by a rapid cooling. Accordingly, heat treatments parameters (such as cooling rate, temperature and time) must be controlled and optimised. By using the induction heat treatment, high heating and cooling rates can be reached with a reduction of the time-cycle compared to a furnace heat treatment. However different corrosion resistance seems to be obtained in the two processes. In this work, the influence of post-welding heat treatment on corrosion resistance of duplex stainless steel welded joints has been analysed. Particularly, a comparison between induction and furnace heat treatment was carried out.
Influence of post-welding heat treatments on corrosion properties of duplex stainless steels - a comparison between furnace and induction heat treatment
FERRO, PAOLO;TIZIANI, ALBERTO;BONOLLO, FRANCO;
2007
Abstract
The excellent combination of strength and corrosion resistance in duplex stainless steels is due to their strict composition control and microstructural balance. The loss of these properties is an important consequence of secondary phases precipitation and unbalanced microstructure, due to thermal cycles and rapid cooling caused by the welding process. To ensure an optimized and well- controlled microstructure, a post-welding heat treatment is generally performed. This heat treatment usually consists in a heating up to a temperature higher than 1000 °C, followed by a rapid cooling. Accordingly, heat treatments parameters (such as cooling rate, temperature and time) must be controlled and optimised. By using the induction heat treatment, high heating and cooling rates can be reached with a reduction of the time-cycle compared to a furnace heat treatment. However different corrosion resistance seems to be obtained in the two processes. In this work, the influence of post-welding heat treatment on corrosion resistance of duplex stainless steel welded joints has been analysed. Particularly, a comparison between induction and furnace heat treatment was carried out.
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