JPS61284519A - Laser hardening method - Google Patents

Abstract

PURPOSE:To form a uniform quench hardened layer on the surface of the required part of a molded part by forming a laser beam absorption film on the surface of the region to be hardened of said part then irradiating the laser beam thereon. CONSTITUTION:The laser beam absorption film 2 is coated on the surfaces of the tooth side walls 3 and tooth bottoms 4 except the tips 2 of the molded part such as internally toothed gear. The laser beam 6 is passed through a condenser lens 7 and is changed in a rectangular direction by a mirror 8. The laser beam 6 is irradiated on the inside surface of the internally toothed gear 1. The laser beam 6 is reflected by the gloss of the member at the tips 2. Only the desired parts of the gear 1 are hardened and the surface of the tips 2 is left as the non-hardened part by the above-mentioned method. The incident angle of the laser beam 6 at the wall parts 3 increases and said parts are more likely to be heated if the mirror 8 is offcentered in the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for surface hardening using a laser, and more particularly to an improvement in a method for hardening molded parts.

[Prior art] In the surface hardening method using a laser, only the local surface is heated to the H1 transformation point or higher using a high-energy-density laser beam, and the hardened layer is formed by self-cooling due to heat diffusion into the member. Ru. Therefore, since only the surface layer needs to be heated, there are advantages such as a small amount of heat input and less thermal distortion.

FIG. 5 is a vertical cross-sectional view schematically showing an internal gear used for automobile parts, etc., and FIG. 6 is an enlarged cross-sectional view taken along the line ■-■. Laser hardening is also applied to such internal gears. Fig. 7 (A> shows the state before laser hardening, and Fig. 7 (B) and <C> show the state after applying the conventional laser hardening method. In the figure, crosshatching is applied. Portion X indicates a hardened layer due to quenching.

[Problem that the invention seeks to solve]

By the way, in the case of hardening a molded part, a special problem exists because the form of heat diffusion is different from that of a flat plate. That is, the fifth
When laser hardening is applied to the internal gears shown in Figs.
Since thermal diffusion is large, it is difficult to heat up. In addition, the tooth side wall 3
Since the incident angle of the laser beam is different from the tooth tip and tooth bottom,
The irradiation energy density of the beam is small, making it difficult to heat the beam.

As a result, when hardened so that a hardened layer is formed on the tooth side wall 3 and the tooth bottom as shown in Figure 7 (8), the tooth tip melts and cracks as shown by the blacked out area y in the figure. is more likely to occur. On the other hand, hardening 1 that does not melt on tooth tip 2
When quenching is performed to form 1x, a problem arises in that a hardened layer cannot be obtained on the tooth side wall 3 and the tooth bottom 4.

In view of the above circumstances, the technical object of the present invention is to form a uniform hardened layer on the surface of a required portion of a molded part.

[Means for solving problems]

In the laser hardening method according to the present invention, a laser beam absorbing coating is applied to the surface of the area of the molded part to be hardened, excluding the parts that have a small heat capacity and are easily hardened, and a laser beam is applied to the molded part coated with the laser beam absorbing coating. It is characterized by irradiation.

In addition, in order to form a good hardened layer in areas that are difficult to harden, such as the side walls of gear teeth, a laser beam absorbing coating is applied as described above, and the laser beam is decentered to reduce the irradiation energy density of the beam in the area. It is desirable to make it larger.

[Effect]

According to the above-mentioned method of the present invention, since the laser beam is reflected by the metallic glossy surface of the member and is not hardened in the parts that do not require hardening, it is possible to harden only the necessary parts.

In addition, parts that have a small heat capacity and are easily hardened, such as the tips of gear teeth, are not directly heated by laser beam absorption, but are heated by heat conduction during hardening heating, so the hardened layer can be heated without melting the surface. can be formed.

〔Example〕

An example in which the laser hardening method of the present invention is applied to an internal gear for automobile parts will be described below.

First, as shown in FIG. 1, a laser beam absorbing liquid 815 was applied to the surfaces of the tooth side wall 3 (excluding the tip 3') and the tooth bottom 4, excluding the tooth tip 2. Next, this internal gear was laser hardened as shown in FIG. 2(A) (8).

In FIG. 2 (A>), 6 is a laser beam emitted from an oscillator (not shown). After passing through a condensing lens 7, the laser beam is converted into a right angle direction by a copper mirror 8. As shown in Figure (B), the laser beam 6 is irradiated onto the inner surface of the internal gear 1. Note that 9 is a rotating jig equipped with an elevating mechanism for elevating the entire optical system.

Moreover, FIG. 3 is a view of FIG. 2(B) viewed from above.

When laser hardening is performed as described above, the laser beam 6 is reflected by the gloss of the member at the tooth tip 2 to which the laser beam absorbing coating 5 is not applied. Note that the tip 3 of the tooth side wall 3
The reason why the coating 5 is not applied to the tip 2 is because the tip 2 tends to trap heat, and after the laser beam passes through the tooth side wall 3, the tip of the tooth side wall 3 is easily heated by heat conduction from the member. . Furthermore, by decentering the copper mirror 8, the angle of incidence of the laser beam 6 on the tooth side wall portion 3 increases, making it easier to heat the tooth side wall portion 3.

In this manner, when laser hardening is performed by the method of the above embodiment, only the portion 10 shown by crosshatching in FIG. 3 is hardened, and the tooth tip surface 11 becomes an unhardened portion. That is,
At the tip of the tooth, the laser beam is reflected due to the gloss of the member, and no hardened layer is formed.

However, like the tooth tip, the tips 3' of both side walls, which are not coated with a laser beam absorption coating, are heated to the A1 transformation point by heat conduction from the laser beam irradiation to the tooth side walls, so they are hardened and hardened. is obtained. In this case, since the irradiation energy density of the laser beam increases on the tooth side wall, sufficient heat input can be obtained to harden the tooth side wall tip 3'.

As a result, a uniform hardened layer can be formed on the tooth side wall and the tooth bottom while preventing the tooth tip from melting. In addition, since there is no hardening of unnecessary parts, the deformation of the product is very small and the performance is good.

Incidentally, the tooth tip diameter is 48a* and the tooth bottom diameter is 54. For internal gears, the quenching speed (inner circumferential speed of the tooth tip) is 1, On/min.
The rotating jig 9 was adjusted so that the laser beam diameter of the internal gear inner surface irradiation part was 6 m.

When the optical system was adjusted to a laser output of 0.7 kW and laser hardening was performed according to the above example, the hardness at the hardening depth of 0.1 was Hv-700 to Hv-750, as shown in Fig. 4. A uniform hardened layer was obtained.

Further, as a result of performing laser hardening on an external gear using a similar method, results similar to those for the internal gear were obtained.

In this case, in FIG. 3, after hardening one side of the tooth with the laser beam 6, the copper mirror 8 is moved to 8', and the remaining tooth side is irradiated with the laser beam 6' again.
Perform hardening.

〔Effect of the invention〕

As described in detail above, according to the present invention, a uniform hardened layer can be formed on the surface of a required portion of a molded part.

It is possible to obtain significant effects such as:

[Brief explanation of drawings]

1 to 4 are cross-sectional views for explaining a laser hardening method according to an embodiment of the present invention, and FIG. 5 is a longitudinal cross-sectional view schematically showing an internal gear to be laser hardened. 6th
The figure is a cross-sectional view along the VI-VI line, Figure 7 (A) ~
(C) is a cross-sectional view for explaining problems in the conventional laser hardening method. 1... Internal gear, 2... Tooth tip, 3... Tooth side wall, 4
...Tooth bottom, 5...Laser beam absorption coating, 6...
Laser beam, 7...Condensing lens, 8...Copper mirror, 9...Rotating jig Applicant sub-agent Patent attorney Takehiko Suzue 1st! ! J Figure 2 Figure 3 n Figure 4

Claims (3)

[Claims] (1) A laser beam-absorbing coating is applied to the surface of the area of the molded part to be hardened, excluding areas that have a small heat capacity and are easily hardened, and the molded part coated with the laser beam-absorbing coating is irradiated with a laser beam. Laser hardening method. (2) Claim (1) characterized in that the laser beam is irradiated with an eccentric angle of irradiation so that the irradiation energy density in the area where the laser beam absorption coating is applied is increased. Laser hardening method described in section. (3) Laser hardening according to claim (1) or (2), wherein the molded part is a gear, and the laser beam absorption coating is applied only to the tooth side wall surface of the gear. Method.