1. The supercooled austenite of the cold-drawn steel pipe is very stable and has high hardenability. Even if it is air-cooled, the martensite structure can be obtained, but air-cooling will cause oxidation on the surface of the tool and may precipitate eutectoid carbides. , so do not use air cooling as much as possible.
2. Cold-drawn steel pipes For large and complex stainless steel pipes, in order to reduce deformation and cracking, cold-drawn steel pipes can be pre-cooled during quenching, but the time should be controlled. Cold-drawn steel pipes are generally controlled according to the shape of cold-drawn steel pipes. To tens of seconds, the premise is that secondary carbides cannot be precipitated to reduce the hardness and red hardness of the tool, and corrosion pitting is not allowed.
3. The graded quenching temperature should not exceed 650°C to prevent the transformation of pearlite and the precipitation of carbides.
4. Considering that the transformation temperature of the lower bainite is 320~250°C, the temperature of the cold-drawn steel pipe is 260~30CTC, so the isothermal temperature of 260~280°C is used for 2~4h in the production.
5. During the quenching operation, the cold-drawn steel pipe should be placed vertically in the cooling medium to reduce deformation.