In the manufacturing of most austenitic stainless steel pipes, tubes, fittings and flanges, solution annealing is commonly applied after forming process is done. These stainless steel grades include SS304/ SS304L, SS316/ SS316L, SS317/ SS317L, SS321, SS347, etc. Generally, the term solution annealing is interchangeable with “solution treatment” or “annealing” in stainless steel, nickel and titanium alloy industry.

In the solution annealing heat treatment, austenitic stainless steels shall be generally soaked at the temperature no less than 1900°F[1038°C] for a long enough time to bring carbon in the steel into a solid solution. The material is then rapidly quenched by water or cool air to prevent the carbon’s reprecipitation. The solution annealing promotes a single phase microstructure resulting in stress-free and uniform mechanical properties. Meanwhile, the corrosion resistance and ductility of austenitic stainless steels are also improved.

There are two delivery conditions for austenitic stainless steel piping materials after solution annealing heat treatment:

• solution-annealed in cooled air, pickled in acids.
• bright-annealed in a high-temp hydrogen furnace.