Views: 3 Author: Site Editor Publish Time: 2020-12-08 Origin: Site
seamless pipe Solution treatment
seamless pipe Solution treatment is necessary for the seamless steel pipes,steel pipes and stainless steel pipes for the below reasons:
1. It is particularly important for raw materials to make the structure and composition of seamless stainless steel pipe uniform and consistent, because the rolling temperature and cooling rate of each section of hot-rolled pipe are different, resulting in the inconsistency of microstructure. At high temperature, the atomic activity is intensified, the σ phase dissolves, and the chemical composition tends to be uniform. After rapid cooling, the homogeneous single-phase structure is obtained.
2. Eliminate work hardening to facilitate subsequent cold working. After solution treatment, the distorted lattice was recovered, the elongated and broken grains recrystallized, the internal stress was eliminated, the tensile strength of steel wire decreased and the elongation increased.
3. The corrosion resistance of stainless steel pipe was restored. Because of the carbide precipitation and lattice defect caused by cold working, the corrosion resistance of stainless steel tube is decreased. After solution treatment, the corrosion resistance of stainless steel seamless pipe recovered to the best state.
The solution temperature is mainly determined by chemical composition. Generally speaking, the solution temperature should be increased for the grades 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 solution temperature and making it fully dissolved.
However, when the solution temperature is high, the carbides of stabilized elements are fully dissolved in austenite, and then precipitate in the form of Cr23C6 at the grain boundary in the subsequent cooling, resulting in intergranular corrosion. In order to keep the carbides (TIC and NBC) of stabilized elements from decomposition and solid solution, the lower limit solution temperature is generally adopted.
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