Quenching-tempering heat treatment method for large-scale module die steel

Abstract

The invention discloses a quenching-tempering heat treatment method for large-scale module die steel. The method comprises the following steps of carrying out heating; carrying out heat preservation;carrying out water-cooling and air-cooling alternate quenching multiple times; and carrying out high-temperature tempering. The method has the advantages that a water-quenching air-cooling mode is adopted, water-lifting air-cooling is carried out multiple times, self-tempering is carried out, the surface structural transformation stress is eliminated, the cooling strength is within oil quenching and water quenching, and therefore through quenching of a large-scale module is ensured, and meanwhile, water-quenching cracking is avoided; the perlitic transformation caused by water quenching is avoided, then water lifting is carried out multiple times to decrease the cooling speed, so that the quenching stress is decreased, and therefore the cooling speed of a high-temperature section is increased, and meanwhile, quenching cracking is also prevented; and when the temperature of martensite cooled to 1.2738 begins to change temperature, air cooling is carried out, so that the forming speed ofthe martensite is decreased, and therefore the structural stress can be greatly decreased, and cracking of a low-temperature section can be avoided.

Description

technical field [0001] The invention relates to a quenching and tempering heat treatment method for a large mold steel module, in particular to a water quenching and air quenching quenching and tempering heat treatment process applied to a large mold steel module of 1.2738. Background technique [0002] 1.2738 mold steel is a material used to make large-scale plastic molds, and has very strict requirements on hardness uniformity. The quenching and tempering heat treatment process of this material generally includes: heating, heat preservation, quenching, high temperature tempering and other steps. The following problems are prone to occur during the quenching and tempering process: 1. Uneven hardness; 2. Quenching is easy to crack; 3. The comprehensive mechanical properties are unqualified . Usually for small 1.2738 forgings, oil quenching can generally be used to improve material properties. As a large module of 1.2738, if the traditional oil quenching is used, it will no...

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Problems solved by technology

[0004] In view of the problems existing in the background technology, the purpose of the present invention is to propose a water quenching + air quenching process to replace the oil quenching method and solve the problems that the large-scale module of 1.2738 die steel is impenetrable by oil quenching and easy to crack due to the high cooling intensity of water quenching. Quenching and tempering heat treatment method for large modular mold steel to solve the problem of water quenching and easy cracking

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