JPH06248327A - Laser beam processing method - Google Patents

Abstract

PURPOSE:To improve the efficiency of the way how the energy possessed by a laser beam is used by specifying the power density distribution of the laser beam with which the surface of a member to be processed is irradiated. CONSTITUTION:The member to be processed is processed by using the beam which has the power density distribution possessing the peak of power density on the rear side in a relative beam moving direction between the member to be processed and the laser beam. The largest surface processing depth is obtd. if such beam is used. The depth of the surface hardened layer is larger than in the case of use of the laser beam having a uniform power density distribution if surface processing is hardening. The hardening is thus efficiently executed. The lowering of the output of the laser beam is possible if the hardening treatment to the same extent as in the case of use of the laser beam having the uniform power density distribution suffices.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser processing method used for irradiating a surface of a member to be processed with laser light to perform processing such as laser hardening.

[0002]

2. Description of the Related Art As a conventional laser processing method, in particular, a laser quenching method, for example, the Japan Welding Association, High Power Laser Metal Processing Method Study Group, published in 1982.
"Laser Processing Technology Manual" Page 42 or 116
The method as described on the page has been considered superior.

That is, in the metal working method described here, a laser beam having a power density distribution having a uniform power density in the beam width direction is formed by some method and this laser beam is used for quenching. .

[0004]

However, in the method of performing the laser hardening using the laser light having the uniform power density distribution which has been used conventionally,
It is very difficult to find the optimum power density distribution shape by changing the power density distribution arbitrarily, and the uniform power density distribution is superior to the multi-, ring-, and single-mode circular beams directly obtained from the laser oscillator. Has only been confirmed analytically or experimentally.
Therefore, it has not been proved that the one having a uniform power density distribution is the optimum beam, and it is a subject to clarify what kind of power density distribution is suitable for laser processing. there were.

Therefore, the present inventor has studied the optimum power density distribution by developing a system capable of simulating the laser hardening phenomenon by numerical analysis.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a laser processing method capable of performing laser processing such as laser hardening in which energy is efficiently used. Is intended to provide.

[0007]

According to a laser processing method of the present invention, when a surface of a member to be processed is irradiated with a laser beam for processing, a relative beam between the member to be processed and the laser beam is provided. The present invention is characterized in that processing is performed using a beam having a power density distribution having a peak of power density on the rear side in the moving direction. As a means to solve

The basic structure of the present invention will be described below with reference to FIGS.

FIG. 1 shows beam lengths of a beam Bac having a power density distribution in which the peak of the power density is deviated in the beam moving direction and a beam Bb having a power density distribution having a uniform power density in the beam moving direction. It is an example of a change in the power density in the direction.

That is, the deviated beam Bac has a power density distribution having a peak of power density on the front side (that is, in the case of beam c) or the rear side (that is, in the case of beam a) in the beam moving direction. However, the uniform beam Bb is composed of the beam b having a power density distribution having a completely uniform power density in the beam moving direction.

When laser processing is performed on the workpiece 1 shown in FIG. 2 using such beams a, b, and c, the power having a peak of power density on the rear side in the beam moving direction. When the beam a having a density distribution is used, a deeper surface-processed portion 2 is formed and the heating effect becomes the largest (see FIG. 2A), and the power having a uniform power density in the beam moving direction is obtained. When the beam b having the density distribution is used, the depth of the surface-processed portion 2 becomes slightly shallower and the heating action becomes smaller than that when the beam a is used (see FIG. 2B).
Furthermore, when a beam c having a power density distribution having a power density peak on the front side in the beam moving direction is used, the surface processed portion is not substantially formed, and a sufficient heating action can hardly be obtained. It was.

[0012]

When the temperature history at the center of the beam surface is examined during laser surface processing, a temperature change pattern as shown in FIG. 3 is obtained, and the relative beam movement direction between the workpiece and the laser beam. It was found that the maximum temperature reached was highest when the beam a having a power density distribution having a power density peak on the rear side was used. on the other hand,
It was confirmed that the maximum temperature reached was lower in the case of using the beam b having a power density distribution having a uniform power density in the beam moving direction than in the case of using the beam a. Further, it was confirmed that the maximum temperature reached was lowest when the beam c having the power density distribution having the peak of the power density on the front side in the relative beam moving direction was used.

As a result, when the beam a having the power density distribution having the peak of the power density on the rear side in the relative beam moving direction is used, the surface processing depth becomes maximum and the surface processing is quenching. In this case, the depth of the surface-hardened layer becomes larger than that in the case where the laser beam having a uniform power density distribution is used, and the quenching process can be performed efficiently, and the beam b having a uniform power density distribution is obtained. If the quenching treatment to the same extent as that of the case of using, the output of the laser light may be further reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS.

FIG. 4 shows laser beams used in the examples and comparative examples of the present invention. The beam Bac has a power density distribution in which the peak of the power density is deviated in the moving direction of the beam, and a beam Bac of the beam. Beam B having a power density distribution having a uniform power density in the moving direction
It shows an example of a change in the density of b in the beam length direction.

That is, in the deviated beam Bac, the beam c of the comparative example of the present invention has a power density distribution having a power density peak on the front side in the beam moving direction, and the power density peak on the back side in the beam moving direction. The beam a of the embodiment of the present invention having a power density distribution is included. Further, the uniform beam Bb is the beam b of the comparative example of the present invention having a power density distribution having a completely uniform power density in the beam moving direction. The output of each of the beams a, b and c is constant at 1850W.

FIG. 5 shows a quench-hardened layer obtained when laser hardening is performed by irradiating the workpiece 1 (member made of S50C) with the above-mentioned three types of beams a, b, and c at a feed rate of 0.75 m / min. The pattern of (surface processed portion) 2 is shown.

As shown in FIG. 5, when the beam a of the embodiment of the present invention having a power density distribution having a power density peak on the rear side in the beam moving direction is used, a deeper quench hardening layer 2 is formed and heating is performed. When the beam b of the comparative example of the present invention having the power density distribution having a uniform power density in the beam moving direction is used, the quench hardened layer 2 has the largest effect (see FIG. 5A). Since the depth is slightly shallower, the heating action is smaller than that when the beam a of the embodiment of the present invention is used (see FIG. 5B), and the peak of the power density is on the front side in the beam moving direction. When the beam c of the comparative example of the present invention having a power density distribution having the above is used, the quench hardened layer is not substantially formed and a sufficient heating action is hardly obtained. It is had.

When the temperature history at the center of the beam surface was examined during laser hardening, a temperature change pattern as shown in FIG. 6 was obtained, and the relative beam movement direction between the workpiece 1 and the laser beam. When the beam a of the embodiment of the present invention having the power density distribution having the power density peak on the rear side is used, the highest temperature reached is highest (FIG. 6).
Indicates that Tm is the melting temperature and A ₃ is the A ₃ point transformation temperature of the steel. ) Was confirmed. On the other hand, it was confirmed that when the beam b of the comparative example of the present invention having a power density distribution having a uniform power density in the beam moving direction was used, the maximum temperature reached was lower than when the beam a was used. . Further, when the beam c of the comparative example of the present invention having the power density distribution having the peak of the power density on the front side in the relative beam moving direction is used, the maximum temperature reached is the lowest, and the A ₃ transformation point of the steel is the lowest. It was confirmed that when the temperature was slightly exceeded, the temperature rise necessary and sufficient for quenching the steel could not be obtained, and the quench-hardened layer could not be substantially obtained.

Therefore, when the beam a of the embodiment of the present invention having the power density distribution having the peak of the power density on the rear side in the relative beam moving direction is used, the quench hardened layer 2 becomes the largest and the quenching efficiency is high. It was confirmed that it could be done well.

[0021]

As described above, in the laser processing method according to the present invention, the processing is performed by using the beam having the power density distribution having the peak of the power density on the rear side in the relative beam moving direction. As a result, the temperature rise of the processed part occurs most rigorously, and the maximum temperature reached is highest when using the same output laser light, so the energy of the laser light can be used most efficiently. Therefore, the heating efficiency for the member to be processed can be increased, and in addition, the remarkably excellent effect that the surface processing such as quenching can be performed with the equipment having a lower laser output is brought about.

[Brief description of drawings]

FIG. 1 is a graph showing a form example of a power density distribution of a beam Bac having a power density distribution deviated in a beam moving direction and a beam Bb having a uniform power density distribution in a beam moving direction.

FIG. 2 shows one mode of the processing effect on the member to be processed when the beam a having the peak of the power density distribution is used on the rear side in the beam moving direction ((a) of FIG. 2), and a uniform effect in the beam moving direction. One mode of the processing effect on the member to be processed when the beam b having the power density distribution is used (FIG. 2B), and the case where the beam c having the peak of the power density distribution on the front side in the beam moving direction is used It is explanatory drawing which shows one aspect ((c) of FIG. 2) of the processing effect with respect to the to-be-processed member.

FIG. 3 is a graph showing one embodiment of heating / cooling curves by beam a, beam b, and beam c.

FIG. 4 is a beam Bac having a power density distribution deviated in the moving direction of the beam used in the examples and comparative examples of the present invention, and a uniform power density distribution in the moving direction of the beam used in the comparative example of the present invention. 6 is a graph showing a power density distribution of a beam Bb having a beam density of

5 is a pattern of a hardened layer depth when quenching is performed using a beam a having a peak of a power density distribution on the rear side in the beam moving direction in Examples and Comparative Examples of the present invention (FIG. 5). (A)), a pattern of the depth of the hardened layer when quenching is performed using the beam b having a uniform power density distribution in the beam moving direction ((b) in FIG. 5), and the front side in the beam moving direction. It is explanatory drawing which shows the pattern ((c) of FIG. 5) of the hardening hardening layer depth when hardening is performed using the beam c which has the peak of a power density distribution.

6 is a graph showing a temperature history at the center of the beam surface when quenching is performed using the beam a, the beam b, and the beam c shown in FIG. 4 (Tm: melting temperature, A ₃ : steel A _3;
Point transformation temperature).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Worked member 2 Quench hardened layer (surface processed part) a Beam having a power density distribution having a peak of power density behind the beam moving direction b Beam having a power density distribution having a uniform power density in the beam moving direction c Beam having a power density distribution having a power density peak on the front side in the beam moving direction

Claims (1)

[Claims] 1. A power having a peak of power density behind a relative beam moving direction between a member to be processed and laser light when the surface of the member to be processed is irradiated with laser light for processing. A laser processing method characterized by performing processing using a beam having a density distribution.