What is the bright heat treatment of stainless steel seamless pipes?

What is the bright heat treatment of stainless steel seamless pipes?

The so-called bright heat treatment includes bright annealing, bright normalizing, bright quenching and bright tempering. In order to prevent the surface of stainless steel seamless pipes from oxidation and decarburization so that they do not lose their metallic luster, heat treatment should be carried out in a protective atmosphere or vacuum as mentioned above.

Bright heat treatment process principle
1. Solid solution treatment: Stainless steel is a special steel containing a variety of alloy elements. After cold working, the original uniform austenite structure is destroyed and the hardenability is obvious. In order to restore the original grain structure, the cold-worked austenitic stainless steel seamless pipe is heated to the high-temperature single-phase zone and maintained at a constant temperature to dissolve various alloy components including impurities into each other. At the same time, during the cold working process, a large number of dislocation-deformed metal grains begin to expand, and eventually uniform grains are precipitated from the stable solid solution through rapid cooling, and return to the austenite structure.

2. Bright treatment. During the heating and insulation process of stainless steel seamless pipes, if air enters the surface, black oxide scale will appear. In order to ensure the brightness of the substrate, nitrogen and hydrogen gas decomposed by ammonia are passed through the heat treatment furnace tube or furnace as a protective atmosphere. Nitrogen is a neutral gas that protects the workpiece from oxidation and decarburization at high temperatures and keeps it bright, while hydrogen not only protects the brightness, but also has a strong reducing effect, making the workpiece brighter and silvery white, and improving the smoothness of the base material.

Common defects in bright heat treatment of stainless steel seamless pipes
1. Insufficient hardness
2. High hardness
3. There are black spots on the surface of the steel pipe, which is not beautiful.
4. The surface of the steel pipe is silvery white with rust.
5. The first batch of steel pipes had poor brightness
6. Black frost or white frost appears in batches

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