JPH0118125B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method of manufacturing a coil spring.

Hot-formed steel springs, such as coil springs, leaf springs, stabilizers, etc. used in vehicle suspension systems, have traditionally been formed in the order of heating, forming, quenching, and tempering. In such conventional methods, heat treatments such as quenching and tempering are performed after forming, which tends to cause distortion.
It was necessary to provide a straightening process after the tempering process. However, providing such a straightening process itself not only increases costs, but also causes scratches on the product due to contact or sliding contact with the straightening jig, or residual stress, reducing the product's lifespan. There are problems such as. In addition, according to the press quenching method, which involves quenching in the pressed state to prevent deformation after forming, the shapes that can be held are limited to leaf springs, disc springs, etc.; The speed tends to be uneven, resulting in incomplete parts in the quenched composition, which may adversely affect the service life. Furthermore, according to the press tempering method, in which a product that has been hardened after forming is tempered in a pressed state, a press mold is required for each product with a different shape, which not only increases mold costs but also requires a lot of setup work. There are disadvantages in that it takes time, and in some cases requires temporary tempering to increase toughness before mounting the jig.

The present invention was made under the above circumstances, and its purpose is not only to eliminate the need for straightening after molding, but also to eliminate the need for shape retention during the heat treatment process. It is an object of the present invention to provide a method for manufacturing a coil spring that does not require molds, jigs, etc., and that can obtain high dimensional accuracy.

In the present invention, when metal is plastically deformed in the middle of transformation, it may exhibit extremely high ductility.The present invention involves heating the quenched steel material to an appropriate temperature and applying a load during the process of changing the metallographic structure during the tempering process. In addition, this method was developed based on the well-known fact that even a small load causes plastic deformation and exhibits large ductility.When winding a spring material such as a wire or rod into a coil, , which is characterized in that it is subjected to a quenching treatment and then molded in a state where it is heated to a tempering temperature or higher.

That is, in the present invention, a spring material formed from spring steel into a wire, bar, etc. shape with a desired cross-sectional shape is directly subjected to a predetermined quenching treatment, and then wound into a desired coil shape in the subsequent tempering process. be. The forming process in this tempering/forming process may be performed at the latter stage of the tempering process as shown in Figure 1, or at the middle stage of the tempering process as shown in Figures 2 to 4. It can be either. In these figures 1 to 4, the horizontal axis is time;
The vertical axis represents temperature, and the broken line portion represents the molding process. The heating temperatures _T1 and _T2 in the figure are each between 150 and 650°C, and the times _t1 and _t2 are each set appropriately between 5s and 90min, but preferably _T1 is between 300 and 550°C. and _t1 is 5s to 10min, and _T2 is 200 to 550°C and _t2 is 5s to 60min.

Example: A spring material formed from SUP7 into a round bar shape with an outer diameter of 12 mm is heated to 900°C using a high-frequency heating device, cooled by water spray, and then hardened to T ₁ = 450 using an electrical heating device. The sample was heated to 0.degree. C., maintained at this temperature for t ₁ =10 min, warm coiled, and further maintained at T ₂ =450° C. for t ₂ =30 min (see FIG. 2). The coil spring thus obtained had no loss in fatigue properties compared to those produced by the conventional method, and the absolute value of dimensional variation was about 1/2.

The present invention is characterized in that, as described above, the spring material is subjected to a quenching treatment and then heated to a tempering temperature and wound into a coil shape. Therefore, since the spring material before molding is directly quenched, the quenching equipment can be simplified and water spray quenching etc. can be easily applied. In addition, since the quenching process is applied to the simple shape before forming, there is no quenching distortion, and since the desired shape is formed during the tempering process, the dimensional accuracy of the product is improved. can be significantly improved.
Therefore, since there is no need for a straightening process, problems such as the occurrence of scratches and shortened lifespan caused by straightening can be completely eliminated, and since there is no need for special shape-retaining means, equipment costs can be reduced. It is possible to increase productivity and improve productivity.

[Brief explanation of drawings]

1 to 4 are diagrams for explaining the tempering and forming process of the present invention. T ₁ , T ₂ ... Tempering temperature, t ₀ ... Molding time, t ₁ , t ₂ ...
Tempering time.

Claims (1)

[Claims] 1. A coil characterized in that when a spring material such as a wire or rod is wound into a coil shape, the spring material is subjected to a quenching treatment and then heated to a tempering temperature before being formed. Spring manufacturing method.