The recommended cooling methods for 304 stainless steel after heat treatment depend on the specific heat treatment process:
1. Annealing:
- Slow cooling: After annealing, slow cooling is generally used. For example, the cooling rate can be controlled at (20 – 50)°C/h. This slow cooling process helps to relieve internal stresses and obtain a more uniform microstructure, which is beneficial to the overall performance of the material, including its corrosion resistance and mechanical properties.
2. Solution treatment: - Rapid cooling (quenching): For solution treatment, rapid cooling is often necessary to achieve the desired properties. The cooling medium is generally clean water. Rapid quenching can help dissolve carbides fully and obtain a single-phase austenite structure, thereby maximizing the corrosion resistance of the steel.
3. Stress relief annealing: - For steel with titanium or niobium: It can be cooled directly in air after reaching the treatment temperature.
- For steel without titanium or niobium: It should be cooled to 500°C first and then cooled in air to avoid intergranular corrosion caused by chromium carbide precipitation.
