JPS6338516A - Laser hardening method - Google Patents

Abstract

PURPOSE:To form a uniformly hardened layer without forming an annealing region to a curved surface of a member, etc., by projecting laser light to the member having the curved surface, etc., to be hardened while rotating said member to heat the surface, then allowing the heated surface to cool of itself. CONSTITUTION:A tappet 1 is imposed on a table 6 in such a manner that the tappet can rotate perpendicularly to a push rod receiving surface 2 under rotation by an off-focusing method in such a manner that a spot size 8 covers a central point 10 and the outside peripheral edge of the surface 2. The entire surface 2 is thereby uniformly heated to the temp. above the transformation point of steel without generating thermal melting even at the surface corresponding to the central point 9 of the projection. The projection of the laser light 4 is then stopped and the heated surface is allowed to cool of itself. The uniformly hardened layer is thus formed on the surface 2. The same effect is also obtainable by rotating the projecting device of the laser light 4 without rotating the tappet 1.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for forming a surface hardened portion having a predetermined hardened layer depth t without forming an annealed region on a surface having curvature. It is something.

[Conventional technology and its problems]

Conventionally, induction hardening or carbonitriding methods have been used to harden only the surface of automobile parts, etc. However, in both of these methods, the entire part is heated to a high temperature, resulting in thermal deformation. The thermally deformed parts are corrected by machining such as cutting.

However, it is difficult to machine parts that have been thermoset, and with these conventional methods, it is difficult to control the quenching width, quenching depth, quenching hardness, etc. It was difficult to harden just a small part of the surface.

Recently, a laser hardening method has been developed and put into practical use as a method to eliminate such drawbacks and harden the desired width and depth of automobile parts and the like at desired locations. This laser hardening method has an energy density of fjf 10” ~
10” W/cm” root circumference laser yt, fi! This is a method in which quench hardening is performed only on the surface area by irradiating the entire area desired for quenching, heating the irradiated area to a temperature above the transformation point of the steel, and then self-cooling. It is possible to do this accurately.

Then, while rotating the cylindrical steel material along its axis, a laser beam is irradiated to the hardened portion of the member, and after the entire outer surface to be hardened is heated to a predetermined temperature, the laser beam irradiation is stopped and the hardening is performed. A method of uniformly hardening the entire hardened area by cooling the hardened area was disclosed in Japanese Patent Application Laid-Open No. 57-171.
It is disclosed in Japanese Patent No. 618.

Further, while irradiating the inner peripheral surface of the cylindrical hollow body with a laser beam from one end of the cylindrical hollow body in a direction inclined with respect to the axis of the cylindrical body, the cylindrical hollow body and the laser beam A method is also known in which the inner surface of a cylindrical hollow body is hardened by tilting at least one of the devices for irradiating the irradiating device to the circumferential axis of the axis Q relative to the other and moving it along the axis. (Japanese Unexamined Patent Publication No. 58-77522) However, there is no known method for uniformly hardening in a circular manner over the entire concave curved surface having a concave curved surface such as a bushing rod receiving surface of a tappet, or within the concave curved surface.

[Purpose of the invention]

An object of the present invention is to provide a method for forming a uniform hardened layer on a curved surface of an automobile part or the like without forming an annealed area.

[Structure of the invention]

While rotating a member to be hardened having a curved surface around the center point of the curved surface, laser light was incident on the curved surface at a certain angle, and the entire desired hardening group was simultaneously heated to a temperature higher than the transformation point of the steel. This is a method of hardening a curved surface using laser light, which is characterized by self-cooling afterward.

The present inventor has developed an irradiation light introduction method, for example, by using a laser ft,'i that can locally harden a part of the inner surface of a small component by modifying the direction of reflection by a mirror, and defocusing.
focusa) As shown in Figure 3, an attempt was made to irradiate the beam source perpendicularly to the contact surface of the bushing rod on the inner surface of the tappet to harden the surface of the bushing rod, but the hardened layer formed was It was not enough to cover the face.

The following will explain based on the drawings.

In FIG. 3, numeral 1 is a tappet, 2 is a bushing rod receiving surface, 3 is a quenched hardened layer, 4 is a laser beam, 5 is a lens,
8IIi Spot size of the irradiation source, 9 indicates the irradiation center〇 As mentioned earlier, in order to harden the entire bushing rod receiving surface of the tappet 1, set the spot size 8 perpendicular to the bushing rod receiving surface 2. Although the laser "J4" was irradiated, the hardened layer that was formed did not cover the entire sliding surface, leaving only the side edges of the bushing rod receiving surface as shown in 3. Therefore, the hardened layer was applied to the entire sliding surface. Attempts were made to harden the hardened layer by increasing the spot size or increasing the irradiation time or power in order to form the hardened layer, but in both cases, a melted area was generated near the irradiation center point 9 of the hardened layer, and the entire bushing rod receiving surface was quenched. It was not possible to form a uniform hardened layer covering the

So, after various considerations, the result was F! I ended up doing A.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 1 is a partially cross-sectional schematic diagram for explaining one embodiment of the present invention, in which reference numerals 1 to 5 and 8°9 have the same meanings as explained in connection with FIG. 3, and reference numeral 6 is a rotating table,
7 indicates the motor, and 10 indicates the center of the shaft.

As shown in FIG. 1, the tappet is placed on the rotary table 6 so that it can rotate around its axis center 10g, and while the motor 7 rotates the tappet, the tappet is placed at right angles to the bushing rod receiving surface of the tappet. By irradiating the laser beam using a defocusing method so that the spot size 8 covers the center point 10 and the outer periphery of the bushing rod receiving surface 2, thermal melting does not occur even on the surface that the irradiation center point hits, and The entire surface of the bushing rod receiving surface can be uniformly heated to a temperature higher than the thermal transformation point of the tappet forming material, and after heating to this temperature, the laser beam irradiation is stopped and cooling forms a uniform hardened layer on the bushing rod receiving surface 2. be able to.

In the example shown in FIG. 1, an example was shown in which the workpiece to be hardened was rotated, but in the example shown in FIG. Of course, both sides may be rotated at the same angle relative to that shown in FIG.

FIG. 2 shows yet another embodiment.

In the example shown in FIG. 2, the laser beam is reflected by the mirror 11, and the bushing rod holder of the tappet is configured to irradiate the side edge from the center of the surface 2, and 10t-
The mirror 11 is rotated so that the laser beam irradiates the entire surface of the bush rod holder, and the entire surface of the bush rod holder is uniformly heated to a temperature above the transformation point of the steel, and then the irradiated metal is fixed and cooled to achieve uniform hardening. It forms a layer.

In the present invention, as shown in FIG. 4, p1 is irradiated by setting the beam irradiation range to 12 at a position away from the axis center 10 while rotating the concave curved surface 2.
It is also possible to form a ring-shaped hardened part 3 within the concave curved surface, and as shown in FIG. It is also possible to form a hardened portion 3t only on O.Although the case where hardening is performed on a concave curved surface has been described above, hardening can be similarly performed on a convex curved surface.
Further, as shown in FIG. 6, it is possible to similarly harden the conical portion.

Example R=45 The bushing rod holder of the snow ball is a part, and as shown in FIG. The entire concave curved surface was hardened by self-cooling after being irradiated with laser light for 2 seconds while rotating r, p, and m. A uniform hardened layer was formed without melting at the center of the concave curved surface.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of the present invention, FIG. 2 is a schematic diagram for explaining an embodiment different from FIG. 1,
FIG. 3 is a schematic diagram for explaining one test conducted up to the present invention, FIGS. 4 and 5 are diagrams for explaining one shape of the hardened part obtained by the present invention, and FIG. 6 FIG. 2 is a schematic diagram showing a state in which a conical portion is hardened.

Claims (1)

[Claims] 1. A member to be hardened having a curved surface or a laser beam irradiation device is rotated around the center point of the curved surface, and a laser beam is incident on the curved surface at a certain angle to simultaneously heat the entire desired hardened area to a temperature higher than the transformation point of the steel. A method of hardening a curved surface using a laser beam, which is characterized by heating the surface to a temperature and then cooling it by itself.