Fuse salt phase change medium used for spring steel step hardening

Abstract

The invention discloses a fuse salt phase change medium used for spring steel step hardening. The medium is the mixed fuse salt composed of, by mole percent, 5 to 10% of NaCl, 5 to 10% of Na2CO3 and 80 to 90% of NaOH. The application method of the fuse salt phase change medium used for spring steel step hardening comprises the following steps of austenitizing, wherein spring steel is heated to 860to 870 DEG C, and heat preservation is carried out for 30 to 40 min; secondly, step hardening, wherein the spring steel obtained in the first step is put into the fuse salt phase change medium, the spring steel is stirred, cooling is accelerated, and the fuse salt phase change medium is subject to continuous heat preservation at the temperature of 282.0 to 295.0 DEG C until the temperature of thespring steel is uniform; thirdly, oil cooling, wherein the spring steel obtained in the second step is put into room temperature quenching oil, and is cooled to the room temperature, and the step hardening of the spring steel is finished. The fuse salt phase change medium has the beneficial effects of being high in cooling speed, small in quenching inner stress, high in hardness, small in workpiece deformation amount, stable in hardening medium temperature and the like and can be applied to the step hardening process of the spring steel.

Description

technical field [0001] The invention relates to a molten salt phase change medium used for staged quenching of spring steel, which belongs to the technical field of heat treatment. Background technique [0002] In the production process of spring steel, the heat treatment process is an essential step. If the heat treatment process is not good, it will naturally fail to meet the production standards of spring steel. Generally, the main heat treatment process of spring steel is quenching and tempering at medium temperature. In the quenching process, the traditional quenching medium of spring steel is quenching oil or water, but the quenching medium of oil is relatively low in cooling rate, and the hardenability of spring steel is low, and quenching is not hard or hardened. Shallow layers and other issues. And after the quenching oil is used for a period of time in heat treatment, the chemical organic chain is easily broken and the chemical composition is unstable due to high...

AI Technical Summary

Problems solved by technology

In the quenching process, the traditional quenching medium of spring steel is quenching oil or water, but the quenching medium of oil is relatively low in cooling rate, and the hardenability of spring steel is low, and quenching is not hard or hardened. Shallow and other issues

And after the quenching oil is used for a period of time after heat treatment, the chemical organic chain is likely to be broken due to high temperature, and the chemical composition is unstable, resulting in uneven quenching of spring steel, forming quenching stress

In addition, the quenching oil needs to be replaced regularly, the waste is large, and it is easy to cause fire and have a serious impact on the environment.

The quenching medium of water-based solvent has a faster cooling rate, which can easily lead to the generation of quenching cracks and large deformation

Therefore, whether it is water quenching or oil quenching, the cooling rate of the two single media is not very ideal, and it cannot obtain a faster cooling rate at high temperature and a slower cooling rate at low temperature