Pipe1 1667543016442 1
yingyong 1667542400620 1
1 1667530337826 1
stainless steel welded tube19201072291 1664429820011
stainless steel t fitting34063968757 1664429811533
stainless steel polished tube44393498871 1664429817494


Significance Of Solution Annealing Treatment For Stainless Steel Pipes

The austenitic stainless steel is softened by solid solution treatment. Generally, the stainless steel pipe is heated to about 950¡«1150¡æ, kept for a period of time, so that the carbides and various alloying elements are fully and uniformly dissolved in the austenite, and then quickly quenched and cooled. , Carbon and other alloying elements are too late to precipitate to obtain a pure austenite structure, which is called solution treatment.

The effect of solution annealing treatment:

1. Make the structure and composition of the steel pipe uniform.

This is especially important for raw materials, because the rolling temperature and cooling rate of each section of the hot-rolled wire rod are different, resulting in inconsistent structure. At high temperatures, the atomic activity intensifies, the 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 distorted crystal 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 rate is increased.

3. Restore the inherent corrosion resistance of stainless steel.

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

For stainless steel 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 steels with high manganese, molybdenum, nickel, and silicon content, the softening effect can only be achieved by increasing the solid solution temperature and making it fully dissolved.

However, stabilized steel, such as 1Cr18Ni9Ti, 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 of stabilizing elements (TiC and Nbc) from decomposing and solid solution, the lower limit solid solution temperature is generally adopted.

As the saying goes, stainless steel is steel that is not easy to rust. In fact, some stainless steel contains both rust resistance and acid resistance (corrosion resistance). The rust resistance and corrosion resistance of stainless steel are due to the formation of a chromium-rich oxide film (passivation film) on its surface. Among them, rust resistance and corrosion resistance are relative.

Experiments have proved that the corrosion resistance of steel in weak media such as the atmosphere and water and oxidizing media such as nitric acid will increase with the increase of the chromium content in the steel, which is directly proportional. When the chromium content reaches a certain percentage, the corrosion resistance of steel changes suddenly, that is, from easy to rust to not easy to rust, from not to corrosion to corrosion.

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