The preparation for heat treatment of die steel is primarily to improve processing performance, eliminate internal stress and prepare excellent metallographic structure for heat treatment after all.
1. Annealing and normalizing annealing and normalizing are used for hot worked blanks. In order to reduce the hardness of carbon steel and alloy steel with carbon content more than 0.5%, annealing treatment is often used; for carbon steel and alloy steel with carbon content less than 0.5%, normalizing treatment is used to prevent tool sticking when cutting with low hardness.
Annealing and normalizing can refine grain size and uniform structure, which can be used for subsequent heat treatment. Annealing and normalizing are carried out after blank manufacturing and before rough machining.
2. Aging treatment is mainly used to eliminate the internal stress in blank manufacturing and machining.
In order to prevent excessive transportation workload, the parts with general precision should be treated with aging treatment before finishing. However, parts with high precision requirements (such as the box of coordinate boring machine) should be treated twice or several times. General aging treatment is not allowed.
In addition to castings, for some precision parts with poor rigidity (such as precision lead screw), in order to eliminate the internal stress in machining and stabilize the machining accuracy of parts, multiple aging treatments are often organized between rough machining and semi finishing machining. Some shaft parts processing, in the straightening process after the organization of aging treatment.
3. Quenching and tempering is the high temperature tempering treatment after quenching. It can obtain uniform and detailed tempered sorbite structure, which is prepared for reducing deformation during surface quenching and nitriding treatment. Therefore, quenching and tempering can also be used as preparation heat treatment.
Because the mechanical properties of quenched and tempered parts are better, some parts with low hardness and wear resistance can also be used as heat treatment process after all.