1. Stress relief annealing

Heat the pipe to 500-650°C, keep it warm for a certain period of time, and then cool it down slowly. Eliminate the internal stress generated during welding and cold straightening of rectangular hollow steel tubing, and eliminate the internal stress generated during cutting of precision parts to prevent deformation during subsequent processing and use. Stress relief annealing is suitable for various castings, forgings, weldments and cold extrusions.

2. Spheroidizing annealing

Heat the rectangular hollow steel tubing to 20-30°C above the critical temperature, and after heat preservation, slowly cool to below 500°C and then take it out of the furnace and air-cool it. Reduce the hardness of steel, improve cutting performance, and prepare for subsequent quenching to reduce deformation and cracking after quenching. Spheroidizing annealing is suitable for carbon steel and alloy pipes with a carbon content greater than 0.8%.

3. Fully annealed

Heat the rectangular hollow steel tubing to 30-50°C above the critical temperature, keep it warm for a certain period of time, and then cool it down slowly with the furnace. Refining grains, uniform structure, reducing hardness, and fully eliminating internal stress Complete annealing is suitable for forgings or steel castings with carbon content below 0.8%.