In daily life, the use of stretch springs everywhere. So if the spring becomes hard, affect the elasticity, can no longer be used normally, then how to deal with, solve. The spring steel reed hardness of the stretch spring manufacturer is abnormal. The main reasons are as follows:

1. Reed heating temperature is too high or holding time is too long, resulting in decarburization of reed surface and low hardness

2. Reed tempering temperature is too high, and reed holding time is too long, resulting in low reed hardness after tempering.

3. Reed heating temperature is too low or holding time is insufficient. Under this condition, the content of carbon and alloying elements in austenite in reed tissue is not enough, and even there are still untransformed pearlite or undissolved ferrite in reed tissue, resulting in the hardness of reed after quenching.

4. The spring steel reed has a high hardness. The main reason is low tempering temperature or short holding time.

5. The reed is too hard after quenching, resulting in low hardness.

Some of the reed of same batch hardness is insufficient, some are on the high side, besides the reason on craft, heat treatment equipment also is a crucial influence factor. Reeds in bulk are often stacked in metal baskets, which leads to uneven heating, which is one of the important reasons for uneven hardness of reeds in the same batch.

Solution: Reasonable control of heating temperature and holding time, and after quenching should be corresponding inspection, to prevent the occurrence of tempering hardness. In addition, the box-type resistance furnace is a mesh belt furnace, which can solve the problem of uneven hardness of reeds in the same batch.

In recent years, the finite element design method of stretch spring has entered the practical stage, and there have been many reports of practical value, such as the effect of spiral Angle on the stress of compression spring; Finite element method is used to calculate the relationship between stress and fatigue life. The comparison between the current design method and the finite element method is shown. For springs of the same structure, under the same load, high stress compression spring with fewer effective rings or large spiral Angle, the results obtained by the two methods are quite different. This is because with the increase of the helix Angle, increase the eccentricity of the load, so that the spring outside diameter or transverse deformation is large, so the stress is relatively large. The current design and calculation methods can not be exactly reflected, but the finite element law can be more accurately reflected.