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310S stainless steel plate is softened by solid solution treatment. Generally, the stainless steel is heated to 950 ~ 1150 ℃ for a period of time, so that carbides and various alloy elements are fully and evenly dissolved in austenite, and then rapidly quenched and cooled, so that carbon and other alloy elements can not precipitate in time to obtain pure austenite structure, which is called solid solution treatment. There are three effects of solution treatment.

(1) it is particularly important for raw materials to make the microstructure and composition of steel pipe uniform, because the rolling temperature and cooling rate of each section of hot rolled wire rod are not the same, resulting in inconsistent microstructure. At high temperatures, atomic activity intensifies, σ After rapid cooling, uniform single phase structure can be obtained.

The work hardening is eliminated to facilitate the continuous cold working. Through solution treatment, the distorted lattice is restored, the elongated and broken grains are recrystallized, the internal stress is eliminated, the tensile strength of steel pipe is decreased, and the elongation is increased.

The corrosion resistance of stainless steel was restored. Due to carbide precipitation and lattice defects caused by cold working, the corrosion resistance of stainless steel decreases. After solution treatment, the corrosion resistance of steel pipe returns to the best state.

For 310S stainless steel plate, the three elements of solution treatment are temperature, holding time and cooling rate.

The solution temperature is mainly determined by chemical composition. Generally speaking, the solid solution temperature should be increased for the brand with many kinds of alloy elements and high content. Especially for the steel with high content of Mn, Mo, Ni and Si, the softening effect can be achieved only by increasing the solid solution temperature and making it fully dissolved. However, the carbides of stabilized elements, such as 1Cr18Ni9Ti, fully dissolve in austenite at high solution temperature, and precipitate at grain boundaries in the form of Cr23C6 during subsequent cooling, resulting in intergranular corrosion. In order to keep the carbides (TIC and NBC) of stabilizing elements from decomposition and solid solution, the lower solution temperature is generally adopted.