Three Elements and Functions of Solid Solution Treatment of Stainless Steel Seamless Pipe

For stainless steel seamless pipes, the three elements of solution treatment are temperature, holding time and cooling rate.

The solid solution temperature is mainly determined according to the chemical composition. Generally speaking, the solid solution temperature should be increased correspondingly for the grades with many kinds of alloying elements and high content. Especially for stainless steel with high content of manganese, molybdenum, nickel and silicon, the softening effect can only be achieved by increasing the solid solution temperature and making it fully dissolved. However, stabilized steel, such as 321 stainless steel tube, when the solid solution temperature is high, the carbide of the stabilizing element is fully dissolved in austenite, and will precipitate in the grain boundary in the form of Cr23C6 during subsequent cooling, causing intergranular corrosion. In order to prevent the carbides (TiC and NbC) of the stabilizing elements from decomposing or solid solution, the lower solid solution temperature is generally used.

What is the effect of solid solution treatment of stainless steel seamless pipes?

1. Make the structure and composition of the stainless steel seamless pipe uniform, which is especially important for the raw materials, because the rolling temperature and cooling rate of each section of the hot-rolled pipe are different, resulting in inconsistent structure. At high temperatures, the atomic activity is intensified, the σ phase is dissolved, and the chemical composition tends to be uniform. After rapid cooling, a uniform single-phase structure is obtained.

2. Eliminate work hardening to facilitate continued cold working. Through the solution treatment, the distorted crystal lattice is restored, the elongated and broken grains are recrystallized, the internal stress is eliminated, the tensile strength of stainless steel is reduced, and the elongation rate is increased.

3. Restore the inherent corrosion resistance of stainless steel seamless pipes. Due to the precipitation of carbides and lattice defects due to cold working, the corrosion resistance of stainless steel seamless pipes is reduced. After the solution treatment, the corrosion resistance of the stainless steel seamless pipe is restored to the best state.

As a seamless tube manufacturer, Permanent Steel Manufacturing Co.,Ltd specializes in the production and supply of seamless steel pipes: thin-wall/thick-wall seamless pipes, stainless steel seamless pipe, precision seamless pipes, small-diameter/large-diameter seamless pipes, providing various specifications and materials, large inventory, rich experience, and can be provided customized service according to customer requirements.