Heat treatment quenching and tempering method

Abstract

A heat treatment quenching and tempering method is disclosed, comprising the following steps of: (1) putting a cast in a heating furnace to be heated up to over AC3, followed by heat preservation; (2) after the heat preservation, taking out and putting the cast in a cooling medium for being cooled; (3) putting the cooled cast in the heating furnace once again to be heated up to the temperature between AC1 and AC3, followed by the heat preservation; (4) after the heat preservation, taking out and putting the cast in the cooling medium for being cooled; (5) putting the cooled cast back in the heating furnace to be heated up to the temperature between 500 DEG C and AC1, followed by the heat preservation; (6) after the heat preservation, taking out and putting the cast in the air for being cooled. Compared with the prior art, the invention has the advantages of low apparatus requirement, simple technological process, low technological cost, realizable batch operation, ideal resultant plastic index and high rate of finished products.

Description

Technical field: [0001] The invention belongs to the field of metal heat treatment, and in particular relates to a heat treatment quenching and tempering method. Background technique: [0002] Due to the crystallization defects of castings during the solidification process of molten steel, and it is impossible to eliminate them by rolling, the mechanical properties of castings, especially the plasticity index, are relatively poor compared to profiles, and the plasticity index in stabilizing and improving its mechanical properties becomes A problem that needs to be solved urgently. [0003] For a long time, in the prior art, there are roughly the following methods for the heat treatment of castings after casting, in order to better solve the above problems: [0004] 1. High-temperature diffusion: the purpose is to homogenize the crystallization, eliminate crystal deflection to the greatest extent, and try to change the distribution of impurities. However, since the casting n...

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Problems solved by technology

[0004] 1. High-temperature diffusion: the purpose is to homogenize the crystallization, eliminate crystal deflection to the greatest extent, and try to change the distribution of impurities. However, since the casting needs to be kept at 1200-1300 degrees Celsius for more than 24 hours, the requirements for equipment are very high, and The process cost is relatively high, and it is not used now;

[0005] 2. Cyclic heat treatment: Casting products are rapidly heated and cooled through multiple cooling steps to achieve refined structure and improve plasticity. However, due to the complicated process and limited by the geometric size, size and heating equipment of the casting, it is difficult to be used in actual production. Realize batch operation;

[0006] 3. High temperature normalizing plus quenching and tempering: it is a more common process method used in the prior art, but due to the limitation of temperature and holding time, the effect of improving the plasticity index of castings is still not ideal;

[0007] 4 Normalizing plus sub-temperature quenching and tempering: the purpose is to improve and improve the plasticity by refining the structure and adjusting the distribution of impurities, but the process effect fluctuates greatly, resulting in low yield

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