JPS5976816A - Surface hardening method - Google Patents

Abstract

PURPOSE:To form a uniformly and satisfactorily hardened layer on the surface on the surface of a small heat capacity body or thin walled body by irradiating a laser beam to the beam irradiation point on the surface of said body while bringing the surface thereof except the irradiation point into contact with a cooling liquid. CONSTITUTION:A thin walled cylindrical body 1 made of 0.45% carbon steel having, for example, 70mm. inside diameter, 10mm. wall thickness and 80mm. length is fixed as a member to be hardened on a table 2 in such a way that the axis thereof is positioned in a perpendicular direction. Water 3 is circulated as a cooling liquid in a storage tank 5 provided tightly via an O-ring 4 on the outside wall of the body 1. A laser beam 6 is then irradiated spirally to the entier inside surface of the body 1 via a reflection mirror 9, thereby hardening the entire surface of said body. As a result, even if the heat capacity of the member is small, the temp. gradient near the heating part of the member during the laser hardening is maintained substantially large by the cooling effect of the water in contact with the outside wall. Thus the cooling rate in the region irradiated by the beam is thoroughly increased and the transformation hardened layer by the hardening is formed deep. The texture of the hardened layer consists of uniform martensite.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for surface hardening of small heat volume ridges or thin bodies using a laser beam.

The laser hardening method locally heats the surface of the material that is exposed to the laser beam, and the hardening strain is small due to heat diffusion to the 8-side motherboard, and the laser beam itself.

It is considered to be suitable for internal hardening of cylindrical materials such as cylinder liners, pipes, and axial housings because it can be easily transmitted to narrow spaces. In such a cylindrical part, the inner diameter is 80~IQOw+I11. Thickness or inner diameter l/20~1
/10 in many cases. However, when using the conventional laser hardening method to harden the entire inner surface of a thin-walled cylinder, the heat capacity is small from a microscopic perspective, so this self-cooling effect weakens, and a sufficient cooling rate can be obtained, resulting in 1-transformation hardening. 4 or so formed and female. A similar phenomenon also poses a problem in the surface hardening method of small heat chambers using a laser beam.

Also, for the purpose of assisting the self-cooling effect during surface hardening of such small heat capacity bodies or thin bodies.

It is also possible to directly bathe the beam irradiation iron parts in water and perform water quenching, but this would require leaving the parts untouched for the duration of the irradiation and quenching work, and the cooling rate would drop by 1 hour. It is necessary to be prepared for some defects in the hardened material, and in addition, there is a risk that the laser processing head and optical parts such as lenses and mirrors may be contaminated or damaged.

The present invention eliminates the drawbacks of the above-mentioned prior art, makes it possible to form a uniform and good surface hardening layer on a small thermal body or a thin body, and furthermore, it is possible to form a uniform and good surface hardening layer on a small thermal body or a thin body. The purpose of the present invention is to provide a surface hardening method that is free from the risk of quenching.

Therefore, the surface hardening method of the present invention is a surface hardening method in which a laser beam is irradiated onto a small heat capacity body or a thin body to harden the surface of the member.

The purpose is to irradiate the laser beam directly onto the laser beam without making at least one part other than the beam irradiation point come into contact with the cooling liquid.

Here, it is good to use a cooling liquid and a liquid that has a cooling power.
Needless to say, M4 is not limited to water.

Also, the effect of cooling the blood as close to the beam irradiation as possible is significant.

The present invention will be explained in detail with reference to the drawings below.

1st +1 # of the present invention! lRegarding the embodiment. FIG. 1 is a schematic cross-sectional view of a tool and a jig showing laser surface hardening of the inner surface of the kneading cylinder.

045% carbon #, ff r”T inner cylindrical body 1? Its axis is in one direction J, sea urchin table 2
Water 8 as a cooling liquid was circulated in a storage tank 5 which was fixedly attached to the outer wall of the thin-walled cylindrical body 1 via an oil puffer 4. Here, the outer diameter of the storage tank 5 was approximately 150 mm, which was twice the diameter of the cylindrical material. Further, a laser beam 6 generated from a laser beam generator (not shown) was irradiated spirally through a reflecting beam 9 to harden the entire surface of the inner surface of the cylinder.

The quenching conditions are as follows.

Laser power: 8 prefectures, laser beam diameter: 1! immφ Beam movement speed W 05III/min Furthermore, in order to clarify the effects of the present invention, laser surface casting of the inner surface of the tube was also performed without cooling with water as a comparative example. Surface hardening /Ii L, schematic cross-sectional diagram of the tube is shown in 7I.

In No. 21-gl, 8 indicates a hardened area, and b represents a hardness of 6111. The results of investigating the hardness distribution in the depth direction of these hardened portions are shown in No. 81-1.

Conventional methods without cooling require a small anchorage.

7. The whole old story. Since the temperature gradient [1] of the nine-part phase becomes small, the cooling rate of the area heated by the laser beam becomes low, and martensitic transformation does not occur, so the Vickers hardness is low. The Golden Cup organization was also mainly composed of intermediate organizations such as Bainite.

In contrast, in the embodiment of the present invention, the heat capacity of the cylindrical material itself is small, but due to the cooling effect of the water in contact with the wall, the temperature gradient near the heated part on the part side during laser hardening is kept sufficiently large, and the laser beam Since the cooling rate of the irradiated area becomes sufficiently fast, it is possible to form a deep transformation hardened layer by quenching. Here, the structure of the hardened layer was composed of uniform martensite.

In addition, according to this embodiment, there is a target in the laser beam irradiation area.
There was no risk of contaminating or damaging the laser treatment and optical parts such as lenses and mirrors, since the bath was not a liquid bath such as water.

As a second embodiment of the present invention, FIG. 4 shows a case where the shaft 7 has a small diameter for easy roasting, and FIG. 5 shows a case where the hardening member has a southeast 8 shaft as an eighth embodiment.

In both Example #1, the temperature gradient near the heating part is large due to cooling, so as the beam moves, heat conduction to the surroundings occurs rapidly.

A sufficient hardening effect can be obtained.

As detailed above, the surface hardening method of the great invention can create a hardened surface layer with sufficient hardness for small thermomorphic objects or natural bodies without contaminating or damaging the optical components of the laser beam generation and transmission system. Because it can be made, it can be used to make end pipes that require surface hardness.

It is especially suitable as a surface hardening method for engine cylinders and hydraulic pipes for construction machinery that require severe wear resistance.

4, +zl Menno+'111. Iv1. lt m
1, 4, and 5 are schematic cross-sectional views of a jig according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a surface-hardened tube, and FIG. FIG. 3 is a comparison diagram of hard IW distribution by surface hardening of Examples and Comparative Examples.

l: Heated member, 3: Coolant, 5: Storage tank, 6: Laser beam, a: Curing area, b: Will

Claims (1)

[Claims] In the surface hardening method in which a laser beam is irradiated onto a small heat capacity body or 7α body to harden the ablated surface, the laser beam is irradiated onto the irradiation point without contacting at least one surface outside the beam irradiation point with the cooling liquid. A surface hardening method that is characterized by