JPS5839887B2 - Induction hardening method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention aims to obtain a quenched layer having a substantially uniform thickness on the end surface of an object to be quenched.

For example, when hardening the end face of a cylindrical sample 1 as shown in the cutaway diagram in FIG. 1, a circular hardening coil 2 is placed opposite the sample to be hardened and a high-frequency current is applied. In this case, the shape of the hardened layer obtained is a concave shape extending along the side surface of the cylinder, as shown by the diagonal line A in sample 1, due to the skin action of the high-frequency current.

However, as shown in Fig. 2, when the center line of sample 1 and the center line of hardened coil 2 are separated by a certain distance d, the distance shown by diagonal line B in Fig. 2 a is A hardened layer is obtained with an asymmetrical shape.

At this time, when sample 1 is rotated around its central axis, the shape of the hardened layer obtained is symmetrical as shown by the diagonal line C in the same figure, and moreover, compared to the case of FIG. It becomes almost flat with less elongation.

For example, if the purpose of the present invention is simply to harden the end portion of a cylindrical sample, the hardening layer may have a concave shape as shown in Figure 1, or a concave shape as shown in Figure 2. Even if the degree of hardening is small, there is no big difference in the results of hardening.

However, as shown in Figure 3, when the central axis of the sample and the central axis of the quenching coil coincide, as is usually done in cases where there is a groove near the end, As shown, the hardened layer extends over the groove, and the sample suffers from quench cracking due to thermal strain occurring in this area.

The figure shows the case of quenching using the method shown in Figure 2.
The hardened layer does not extend into the concave grooves and does not cause quench cracks.

At −7° or more, we took the case where the cross section of the sample is circular, but it does not necessarily have to be circular, and even something close to circular can suffice to achieve the purpose. .

In addition, when quenching is automated and continuous operation is performed, the quenching coil 2 is made into a hairpin type as shown in FIG. 4a, and the sample 1 is rotated and moved inside the coil.

At this time, it is necessary to provide a certain distance d between the center line of the hairpin type coil 2 and the center line of the sample 1.

In the figure, 1 is a sample, and 2 is a hairpin type coil connected by a conducting wire 2. Both ends of the coil 20 are connected to a high frequency power source through a conducting wire 3.

FIG. 4 is a cross-sectional view.

[Brief explanation of drawings]

Figure 1 shows the case where the end of a cylindrical sample is induction hardened using the conventional method, and Figure 2 shows the case where a similar sample is hardened using the method of the present invention. FIG. 3 is a diagram showing that uniform heating can be obtained because of the FIGS. 3a and 3b are explanatory diagrams in which a cylindrical sample having a concave groove near the end face to be hardened is hardened by the conventional method (a) and the method of the present invention ff1b). FIG. 4 atb shows a perspective view and a sectional view in the case of moving hardening using a hairpin type hardening coil. 1... Sample, 2... Quenched coil, A. B. C...Chrysanthemum line (quenched part display), D...Concave groove.

Claims (1)

[Claims] 1. Induction hardening of an end face, which is characterized by making the center of a quenching coil facing the end face eccentric from the center of the object to be hardened, and performing hardening while rotating the object to be hardened. Law.