Heat treatment is the process of heating a material to a high temperature and rapidly cooling it, which changes its microstructure and consequently alters its physical, chemical, and mechanical properties. This process modifies the material's performance characteristics and improves its service life. Common heat treatment techniques include annealing, tempering, quenching, and normalizing.

Heat treatment is a crucial processing step in enhancing the intrinsic quality and service life of mechanical parts. It has a critical and long-lasting impact on the quality of the parts and the equipment they constitute. Heat treatment is an essential foundational technology in the mechanical engineering industry and modern manufacturing.

The development of the heat treatment industry has a significant impact on the progress of various industrial sectors, including machinery, electronics, energy, automotive, aerospace, and construction. Improving the level of heat treatment technology, equipment, and production techniques can lead to energy and material savings, as well as enhance the competitiveness of enterprises.

The basic process of heat treatment involves heating, holding, and cooling. The main technological facilities are heat treatment furnaces, such as vacuum furnaces and controlled atmosphere furnaces.

Nitrogen (N2) is used in the heat treatment process to protect the materials being processed and prevent the oxidation of metal materials. For example, nitrogen-based atmospheres are used in controlled atmosphere furnaces, as a protective gas for purging and displacement during the opening and closing of vacuum annealing furnaces, as a cooling gas for high-pressure gas quenching, and as a backfill gas during heating.