What is the role of solid solution treatment (annealing treatment) of stainless steel welded pipe
Austenitic stainless steel welded pipes are softened by solution treatment.-Generally, stainless steel pipes are heated to about 950 to 1150 ° C and held for a period of time, so that carbides and various alloy elements are fully and uniformly dissolved in austenite, and then quickly quenched Water cooling, carbon and other gold elements are too late to precipitate, and a pure austenite structure is obtained, which is called solid solution treatment. There are three effects of the solution treatment.
(1) Make the structure and composition of stainless steel welded pipe uniform, which is especially important for raw materials, because the rolling temperature and cooling rate of each section of hot-rolled wire are not the same, resulting in inconsistent microstructure. At high temperatures, atomic activity intensifies, phases dissolve, chemical composition tends to be uniform, and a uniform single-phase structure is obtained after rapid cooling.
(2) Eliminate work hardening to facilitate continued cold working. Through the solution treatment, the twisted lattice is restored, the elongated and broken grains are recrystallized, the internal stress is eliminated, the tensile strength of the steel pipe is reduced, and the elongation is increased.
(3) Restore the inherent corrosion resistance of stainless steel. Due to cold working, the precipitation of carbides and lattice defects reduce the corrosion resistance of stainless steel welded pipes. After solution treatment, the corrosion resistance of the steel pipe was restored to the best state.
Stainless steel welded pipe
For stainless steel welded pipes, the three elements of solution treatment are temperature, holding time and cooling rate.