The subcooled martensite of Q345C seamless steel pipe is very stable and has very high cutting performance. Even air cooling can obtain austenite mechanism, but air cooling will cause air oxidation on the surface of the CNC blade, and precipitation eutectoids may occur. Cementite, so air cooling is not used as much as possible.
In order to reduce the deformation and cracking of the Q345C seamless steel pipe, rapid cooling can be carried out during quenching, but the time should be controlled. Generally, the operation is performed in a few seconds to tens of seconds according to the appearance of the Q345C seamless steel pipe. The prerequisite is that it cannot be carried out. The precipitation of secondary cementite reduces the strength and red force of the CNC blade. In addition, it is not allowed to cause erosion and black spots.
The quenching temperature of Q345C seamless steel pipe should not exceed 650°C to avoid ferrite change and cementite precipitation. Fully consider that the martensite change temperature of Q345C seamless steel pipe is 320~250°C, and the change temperature is 260~30CTC. Therefore, the 260~280°C isothermal process is selected for 2~4h in the production of Q345C seamless steel pipe.
Q345C seamless steel pipe should be placed vertically in the cooling material during actual quenching operation to reduce deformation.
