Precise stainless steel pipe refers to stainless steel pipes with austenitic organization in normal temperature. Stainless steel tubes contain about 0.1% C, 18% Cr, 8% ~ 10% Ni, with stable austenite organization. Common heat treatment technologies are: solution treatment, stabilizing treatment and stress relief treatment.
Solution treatment
Heat precise stainless steel pipes to 1050-1150 degrees Celsius and then water quenching, making carbon dissolved in stainless steel and keep the state in room temperature, which is a method of heat treatment to prevent the intergranular corrosion and corrosion resistance of the steel will be improved greatly. For thin-walled precise stainless steel pipes, generally water cooling is adopted as well as air cooling.
Stabilizing treatment
Stabilizing treatment is commonly carried out after solution treatment. Heat precise stainless steel pipe to 850-880 degrees Celsius and perform air cooling after heat preservation, Cr carbide will be completely dissolved later on and sufficiently precipitate in cooling process, making it impossible for C to form Cr carbide again, achieving the goal of effectively eliminating intergranular corrosion.
Stress relief treatment
Stress relief treatment of precise stainless steel pipes is a kind of heat treatment process to eliminate residual stress of precise stainless steel pipes after welding or cold working, general tempering after heating to 300-350 degrees Celsius. For precise stainless steel pipes without stabilizing element Nb and Ti fine, heating temperature should not exceed 450 degrees Celsius, in case precipitated Cr carbide will cause intergranular corrosion. For precise stainless steel pipes with Nb, Ti and ultra low carbon should be heated in 500-950 degrees Celsius, slow cooling and stress relief can relieve the tendency of intercrystalline corrosion, improving stress corrosion resistance of precise stainless steel pipes.
