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Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

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Spring Heat Treatment Quality Inspection and Operation Precautions

Spring heat treatment quality inspection includes inspection before heat treatment and inspection after heat treatment.

1. Quality Inspection Before Heat Treatment:

The rolled surface of steel is often the surface after the spring is made, so there should be no cracks, folds, scars, hair lines, bubbles, interlayers, and pressed oxide scales.

Surface decarburization will significantly reduce the fatigue strength of the spring, so the depth of the decarburized layer should be inspected as required.

2. Quality Inspection After Heat Treatment:

There should be no cracks, corrosion pitting and severe quenching deformation on the surface of the spring when observed with the naked eye or a low-power magnifying glass.

The hardness and its uniformity meet the requirements. In mass production, it is allowed to use a file to sample the hardness, but it must be noted that the position of the file mark should not affect the final accuracy of the spring.

The metallographic structure should be Tobstone or a mixed structure of Tobstone and Sorbite.

After the leaf spring is assembled, the permanent deformation under working load and static load deflection test are usually carried out.

3. The Precautions For Spring Heat Treatment Operation Mainly Include the Following Four Aspects:

Check the surface for defects such as decarburization and cracks before heat treatment. These surface defects will seriously reduce the fatigue limit of the spring.

The quenching heating should pay special attention to prevent overheating and decarburization, do a good job in salt bath deoxidation, control the characteristics of the furnace gas, and strictly control the heating temperature and time.

In order to reduce deformation, attention should be paid to the way of loading the spring during heating, the form of fixtures, and the quenching cooling method during cooling.

Tempering as soon as possible after quenching, and heating should be as uniform as possible. Quick cooling after tempering can prevent temper brittleness and cause surface compressive stress, and improve fatigue strength.