Why should annealing and normalizing be preheated?

Because the preheating treatment is to prepare the structure for the final cold treatment, after casting or forging, the grains are coarse. If the quenching and tempering heat treatment is directly carried out, the coarse original structure will be inherited and quenched unevenly, or the defects such as quenching cracking will be caused, resulting in the decline of properties. Normalization or annealing can refine austenite grains, reduce chemical composition segregation, obtain uniform and fine structure in subsequent quenching, and avoid quenching cracking.

1. heat treatment process: heat treatment is a hot working process in which steel is heated to a predetermined temperature in solid state, kept at this temperature for a period of time, and then cooled down at a certain speed. The function and purpose of heat treatment is to change the internal structure of steel to improve its properties.

2. Proper heat treatment can significantly improve the mechanical properties of steel and prolong the service life of machine parts.

3. Heat treatment technology can not only strengthen metal materials, fully tap the material performance potential, reduce structural weight, save materials and energy, but also improve the quality of mechanical products and greatly extend the service life of machine parts.

4. Appropriate heat treatment process can eliminate all kinds of defects caused by hot working processes such as casting, forging and welding, refine grains, eliminate segregation, reduce internal stress, and make the structure and properties of steel more uniform.

5. Heat treatment is also an important process in the processing of mechanical parts.

6. In addition, heat treatment can also make the surface of the workpiece have special physical and chemical properties such as wear resistance and corrosion resistance.