JPS62238324A - Laser hardening method - Google Patents

Abstract

PURPOSE:To execute local hardening to require both wear resistance and fatigue resistance to a part where hardening is difficult by irradiating a laser beam to a work to alternately produce parts hardened by the laser and temperature parts. CONSTITUTION:The laser beam OAB is irradiated to the surface of the work to form the hard part of the hardened part AB in the thin region under the surface. The laser beam or the work is then shifted by a specified distance until the irradiating parts are partly overlapped. The laser beam O'CD is then irradiated thereto. The hard part of the hardened part CD is formed by such irradiation and tempering is generated in the outside edge part PQRC of the region CD in the region AB by which said part is softened. The hardened parts and tempered parts are alternately produced on the surface of the work by repeating the above-mentioned heat treatment operation. The hardening consisting of the former having the wear resistance and the latter having the fatigue resistance is thus executed.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for hardening various mechanical parts using a laser beam. The present invention provides a new hardening method for articles that require both wear resistance and fatigue resistance.

[Prior Art and Problems to be Solved by the Invention] Conventionally known quenching techniques include a method using high frequency and a method of quenching and tempering by carburizing. The former is caused by high-frequency induced current! This is a method of hardening the skin of material A by rapidly heating and cooling it, and is used as a surface hardening method for mechanical parts that require wear resistance with a tensile strength/v. However, this method has a major drawback in that hardening cannot be done if the part that requires hardening is the bottom of a concave spherical surface. The latter is a method in which the steel material is heated in a carburizing agent, the surface is carburized, and then the carburized part is hardened by mastication, which improves wear resistance, fatigue resistance, and hardness. There is a drawback that even parts of the target product that are not desired to be hardened are hardened, and therefore parts that do not require hardening must be annealed as a post-treatment.

As an alternative to this, laser hardening has recently been researched.
It has come to be put into practical use. This is 103~105W/
When irradiated with a laser beam focused to the energy density of CIi, the beam is absorbed by the extremely thin surface of the metal, and the surface hardens by utilizing the sudden heat generation. Laser hardening based on this principle allows the laser beam to be irradiated only on the areas that require hardening, so there is less deformation or cracking due to thermal strain, and it is possible to harden even products with complex shapes. There is water for self-cooling,
It has many advantages, such as heat treatment in the atmosphere without the need for cooling means such as oil, and the depth of hardening can be precisely controlled by output and processing speed.

In order to eliminate the drawbacks of the above-mentioned surface hardening method using high frequency and hardening and tempering methods using carburizing, the present inventors have devoted themselves to research using a hardening method that uses a laser beam. The present inventors have discovered a new hardening method for parts that need to be hardened and that require both wear resistance and fatigue resistance, and have completed the present invention.

[Means for solving problems]

That is, the present invention alternately creates hardened portions and tempered portions using a laser, and performs heat treatment so that the hard hardened portions have wear resistance and the soft tempered portions have fatigue resistance.・This is a laser hardening method with one characteristic.

(Function) A method of alternately creating hardened areas and tempered areas using Rayleigh will be explained. When the surface of the workpiece is irradiated with laser beams 0 to 6 shown in FIG. 1, a hardened portion (hardened portion) indicated by AB is generated in a thin region under the surface. Next, shift the laser beam or the workpiece by a certain distance U so that the irradiated parts partially overlap, and irradiate the laser beam 0'CD.The CD area will be hardened and hardened, but the area AB will be hardened. Tempering occurs at the outer edge PQRC of the CD, and this region becomes soft.

The present invention skillfully utilizes this phenomenon, and by repeating the above-mentioned heat treatment operation, as shown in Fig. 2, hardened parts and tempered parts are alternately exposed on the surface of the workpiece, and the former has wear resistance. The latter is responsible for fatigue resistance, and the material is modified in areas that are difficult to harden.

In reality, the surface to be hardened is a flat or curved surface.
Hardening is then carried out on these surfaces according to a suitable hardening pattern - for example, a family program as shown in FIG. Once the laser beam has gone around the spiral, the irradiation position of the laser beam will be adjacent to the previous irradiation position, and the heat treatment shown in FIG. 1 will be performed over this entire region.

In the present invention, the ratio of the hardened part to the tempered part is the cross section of the hardened part, and when the width of the first hardening along the surface, that is, AB in FIG. It is desirable that the width of the first quenched portion excluding the portion, that is, AP in FIG. 1, is 10 to 80%. Figure 2(a).

(b), (c), and (d) are four cases in which the ratio of the hardened part and the tempered part is different, that is, AP is 15 each.
, 50.65.85%.The quenching positions do not necessarily overlap, but if they are too far apart and AP reaches &5% as in (d), the softened portion will be small. , are unsuitable for the purpose of the present invention. The ratio of the hardened part to the tempered part can be changed depending on the purpose of the heat-treated part by changing the distance between the spiral lines in Figure 3. If wear resistance is important, increase the hardened part to improve fatigue resistance. If this is important, try not to create too many soft parts during tempering. Also, the intervals between the hardened parts or tempered parts may be equal as shown in Figure 2, but depending on the shape of the product to be hardened, the distances between the lines of the R family program may be made unequal to make the intervals unequal. You can also do that.

Examples will be described below with reference to the drawings, but the present invention is not limited thereto.

〔Example〕

The spindle lever was laser hardened using the Zura family program shown in FIG. The appearance of this spindle is as shown in FIG. 4, and the purpose is to harden only the bottom of the concave spherical surface at the lower left. The appearance of hardening when laser hardening is performed according to the present invention is shown in FIG.
As shown in 1), only the predetermined bottom part is accurately hardened, and the internal hardening state of the A-A' cross section and the enlarged view of the hardening state of the concave spherical bottom part marked with a circle are shown in Figure 5. It looked like examples (2) and (3). (3)
The quenched structure and tempered structure appear alternately.

Comparative example 1> The same spindle lever as in the example was hardened at high frequency.

The hardened appearance is as shown in Comparative Example 1 (4) in Figure 5.
The surface of the spindle body and the outer wall of the concave spherical surface were hardened, and the bottom, which was the most important part, could not be hardened. FIG. 5 Comparative Example 1 (5).

(6) is an enlarged view of the internal hardening state of the A-A' cross section and the bottom hardening state of the round part.

Comparative Example 2> The same spindle lever as in the example was hardened by carburizing. As for the appearance of the hardened spindle, as shown in Comparative Example 2 (7) in FIG. 5, the entire surface of the spindle is hardened, and even the threaded portion that does not require hardening is hardened. Therefore, subsequent annealing is necessary. . Figure 5 Comparative Example 2 (8), (9
) is an enlarged view of the internal hardening state of the AA' cross section and the bottom hardening state of the round part, similar to the above two examples. In (9), the structure is carburized and quenched, but it is not possible to create the quenched part and the tempered part in an alternating manner (31).

(Effects of the Invention) As is clear from the above explanation, it is possible to locally harden hard-to-harden parts, which was impossible with the prior art, and the hardened parts and tempered parts can be alternated according to a certain pattern. The method of the present invention, which can be developed in this manner, is extremely useful as a surface hardening technique for mechanical parts having complex shapes, and is of great benefit to the world.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a method for alternately revealing hardened portions and tempered portions according to the present invention, and FIG. 2(a). (b), (c), and (d) are explanatory diagrams in which the ratio of the hardened part and the tempered () part are changed; FIG. 3 is a diagram showing an example of the pattern of laser hardening according to the present invention; FIG. Fig. 5 is an external view of the binder lever used in Examples and Comparative Examples.
), (7) ), Internal quenching status of A-A' cross section ((
2), (5), (8)) and enlarged views ((3), (6), (9)) of the hardening state of the concave spherical bottom of the round part. In FIGS. 1 and 2, the shaded area indicates a quench hardened area, and the shaded area 75 indicates a tempered softened area. Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] A laser is used to create hardened and tempered parts alternately.
A laser hardening method characterized by applying heat treatment so that the hard part of the quenching process provides wear resistance and the soft part of the tempering process provides fatigue resistance.