Austenitic stainless steel through the solution treatment to soften, the general stainless steel tube heated to 950 ~ 1150 ℃ or so, for some time, so that carbide and a variety of alloying elements are fully evenly dissolved in austenite, and then quickly quenched and cooled, carbon and other alloying elements too late to precipitate, access to pure austenite, known as the solution treatment. The effect of solution treatment is 3 points.
⑴ Make the steel pipe organization and composition of uniform, which is particularly important for raw materials, because the hot rolling wire sections of the rolling temperature and cooling rate is not the same, resulting in inconsistent organizational structure. At high temperatures, the atomic activity increases, the σ phase dissolves, the chemical composition tends to be uniform, and the uniform single-phase structure is obtained after rapid cooling.
⑵ Eliminate processing hardening, in order to facilitate the cold processing. Through the solution treatment, the crooked lattice recovery, elongation and fragmentation of the grains are recrystallized, the internal stress is removed, the tensile strength of the steel pipe decreases, and the elongation increases.
⑶ Restore the inherent corrosion resistance of stainless steel. Due to cold processing caused by carbide precipitation, lattice defects, so that the corrosion resistance of stainless steel decreased. After the solution treatment, the corrosion resistance of the steel pipe is restored to the best condition. For stainless steel, the three elements of the solution treatment are temperature, holding time and cooling rate.
