Yes - but heat treatment of duplex stainless steel is usually restricted to its initial production. After forging or rolling, items are given a solution annealing heat treatment.
Held above 1040°C, the composition and microstructure normalise throughout the item. The hold time depends on the maximum section thickness, to allow the whole item to reach the required temperature. Solution annealing is then followed by a rapid quench in water, with minimal delay between the furnace and the bath.
Stress-relieving is not recommended for duplex or super duplex stainless steels, given their potential to form deleterious intermetallic phases at temperatures below the solution annealing temperature.
The effects of heat treatment
There are two main effects of heat treatment on these stainless steels:
- Solution annealing - at elevated temperatures the alloying additions effectively dissolve into solution and become more evenly distributed. Rapid quenching then freezes that composition in place.
- 475°C embrittlement - following long-term exposure at temperatures between 280 and 450°C, duplex stainless steels undergo thermal ageing embrittlement. The ferritic elements of the microstructure begin to decompose into iron-rich or chromium-rich areas, which significantly reduces corrosion resistance and mechanical properties.