JP3223271B2 - Laser hybrid heating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating a surface of a metal material by irradiating an infrared laser beam and performing various processes to increase the absorption efficiency of the laser beam and suppress the reflection of the laser beam. To prevent damage to the optical system and the like.

[0002]

2. Description of the Related Art In recent years, with the emergence of high-power lasers having a large average output, laser processing technology has rapidly developed, and various fields, for example, various electronic components including semiconductors, precision machines, automobiles, steel, non-ferrous metals, and the like. In the fields of metals, ceramics, and the like, laser processing has been widely performed as a processing means.

In thermal processing using laser light, various types of processing such as evaporation processing such as trimming and drilling, melting processing such as welding, quenching, and solid-phase heating processing such as annealing are performed depending on the power density of the laser light applied to the metal material surface. Has been selected and implemented.

[0004] A typical type of laser for generating such laser light is to excite a laser medium contained in an optical resonator, operate the laser medium in an inverted population state, and generate laser light. , Depending on the type of medium, a solid-state laser (N
Known are d: YAG laser, Ti: sapphire laser, gas laser (carbon dioxide laser, argon ion laser, helium-neon laser, etc.), semiconductor laser, dye laser, excimer laser, free electron laser, and the like. Unlike the spontaneous emission light generated by other light sources, the laser light generated from these lasers is coherent light with almost perfect phase, monochromatic light with a narrow spectral width, remarkable coherence, and directivity. It becomes a narrow beam with sharp gender. If this laser beam is focused, theoretically, all outputs are concentrated at a focal point within the same size as the wavelength.

When the surface of a metal material is heated by using such a laser beam to perform thermal processing, if a material having a high reflectance or transmittance with respect to light is used, the processing capability is reduced and the energy efficiency is reduced. Various methods of improving laser light absorption have been tried so far, because not only the decrease but also the magnitude of the reflected power may damage the optical system and the like.

As a typical example, a method of applying an organic or inorganic absorbing paint on the surface of a metal material is known. In this method, a uniform laser light absorbing surface is formed on the surface of the material. In addition, it is difficult to perform the welding, and welding causes a defect. Further, among the absorbing paints used for such purposes, those having an absorption wavelength even from visible to near infrared, such as carbon black,
Problems such as the need for post-processing in appearance arise.

On the other hand, a method has been studied in which an oxide film formed when a high peak pulse laser beam such as an excimer laser beam is irradiated is used as an absorbing material. However, this method involves prior irradiation with an excimer laser beam. By
The oxide film originally adhered and the adhered impurities are removed, and an oxide film having a uniform thickness is newly formed to stably absorb infrared laser light.

However, such a method has a drawback that defects are formed by entrapment of an oxide film, and a film transparent to light having a wavelength from visible to far-infrared has been increasingly applied to laser processing in recent years. Almost no improvement in the absorptance is observed for the YAG laser light.
Further, the pre-irradiation of the excimer laser causes problems such as an increase in the number of steps and a need to control the direction of the optical system according to the heating direction.

[0009]

SUMMARY OF THE INVENTION Under such circumstances, the present invention provides a method for heating a surface of a metal material by irradiating an infrared laser beam having a large average output to perform various processes. It is an object of the present invention to provide a method for increasing the absorption efficiency of a beam, effectively transmitting the energy to a metal material, and suppressing the reflection of the laser beam to prevent damage to an optical system or the like. .

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object. As a result, when the surface of a metal material is irradiated with an infrared laser beam and a KrF excimer laser simultaneously, the vicinity of the surface is obtained. High-density plasma is induced in
The present inventors have found that this plasma easily absorbs an infrared laser beam and enhances the energy use efficiency, and based on this finding, completed the present invention.

That is, according to the present invention, when a surface of a metal material is irradiated with an infrared laser beam to heat-treat the surface,
Simultaneously irradiating a KrF excimer laser pulse beam,
Another object of the present invention is to provide a laser hybrid heating method characterized in that high-density plasma is induced in the vicinity of the surface, and the plasma absorbs an infrared laser beam.

As the metal material to which the method of the present invention is applied, various metals conventionally subjected to thermal processing by an infrared laser beam, for example, metals such as iron, nickel, cobalt, chromium, aluminum, copper, zinc, tin, and the like, Alloys based on these, for example, stainless steel, carbon steel, brass, white copper, aluminum alloys, and the like can be given.

In the method of the present invention, the infrared laser beam is
A laser beam having a large average output, such as an infrared laser including a near-infrared or far-infrared laser, for example, a continuous excitation type Nd: YAG laser, Yb:
There are laser beams generated from a YAG laser, a semiconductor laser, an iodine laser, a carbon dioxide laser, a CO laser, and the like. These infrared laser beams may be either pulse oscillation or continuous oscillation.

In the method of the present invention, a KrF excimer laser pulse beam is used together with the above-mentioned infrared laser beam. However, this method causes an ablation phenomenon and generates high-density plasma near the surface of the metal material. 20 kJ / m ² or more for the melting point metal material,
It is preferable to use a high melting point metal material at an irradiation intensity of 50 kJ / m ² or more.

The high-density plasma near the surface induced by irradiating the KrF excimer laser pulse beam on the metal surface in this way easily absorbs the infrared laser beam. Therefore, in the method of the present invention,
The KrF excimer laser pulse beam and the infrared laser beam are simultaneously irradiated to induce high-density plasma near the surface thereof, and the plasma absorbs the infrared laser beam. As a result, the absorption efficiency of the infrared laser beam is improved, and the energy is effectively transmitted to the metal material, so that the laser thermal processing can be performed efficiently and the reflection of the infrared laser beam can be suppressed. Therefore, damage to the optical system and the like can be prevented.

Next, the method of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram of an example of a laser heating apparatus for carrying out the method of the present invention, and FIGS. 2 to 5 show different examples of optical systems in the laser heating apparatus for carrying out the method of the present invention. FIG.

In FIG. 1, as an infrared laser beam,
When a near-infrared or far-infrared laser beam is used for pulse oscillation, the oscillation timing is controlled based on an output pulse from the pulse generator 1. The output pulse is input to the infrared laser oscillator 3 after the input signal level is adjusted by the driver 2, and the infrared laser beam 4 is output.
When the near-infrared or far-infrared laser beam is used in a continuous output state, the laser beam is output during heating regardless of the signal of the pulse generator. After the output laser beam is reflected by the plane mirror 5, it is focused on the metal material surface 7 by the convex lens 6. The same output pulse signal is input to the KrF excimer laser oscillator 9 by the delay control device 8 after being delayed by a predetermined irradiation start time difference from the internal delay time difference between the laser oscillators, and the KrF excimer laser pulse beam 10 is output.

After the output laser pulse beam is reflected by the plane mirror 5 ', it is condensed by the convex lens 6' in the infrared laser beam irradiation area of the metal material surface 7 or an area including the same. Note that the reflection state during laser beam irradiation is based on the KrF excimer laser cut filter 11.
Is monitored by the photodetector 12 and the waveform storage device 13 Reference numeral 14 denotes a laser irradiation optical system.

FIG. 2 shows an example of a coaxial irradiation optical system applicable to a case where a near-infrared laser beam is used as an infrared laser beam. The light passes through the excimer laser beam mirror 15 and is focused on the metal material surface 7 by the convex lens 6. K
The beam size of the rF excimer laser pulse beam 10 is adjusted by the convex lenses 6 ′ and 6 ″, and after being reflected by the KrF excimer laser beam mirror 15, the infrared laser beam irradiation area of the metal material surface 7 is projected by the convex lens 6. The beam size can be adjusted by combining a convex lens and a convex lens, or by combining a convex lens and a concave mirror, in addition to combining two convex lenses as in this example.

FIG. 3 shows an example of a coaxial irradiation optical system in which a near-infrared or far-infrared laser beam can be used as an infrared laser beam. The light is collected by the convex lens 6. The focused beam passes through the aperture of the perforated plane mirror 15 'and reaches the metal material surface 7. The KrF excimer laser pulse beam 10 is adjusted in beam size and focused by the convex lenses 6 'and 6 ", reflected by the perforated plane mirror 15', and then in the infrared laser beam irradiation area of the metal material surface 7 or The beam size can be adjusted and condensed by combining a convex lens and a convex lens, or by combining a convex lens and a concave mirror, in addition to combining two convex lenses as in this example.

FIG. 4 shows an example of a coaxial irradiation optical system which can use a high-power near-infrared or far-infrared laser beam, for which it is difficult to use a transmission optical system, as the infrared laser beam. The laser beam 4 is reflected and condensed by the concave mirror 16. The focused beam passes through the aperture of the perforated plane mirror 15 'and reaches the metal material surface 7. The KrF excimer laser pulse beam 10 is adjusted in beam size and condensed by the convex lenses 6 and 6 ′, and is reflected by the perforated plane mirror 15 ′. Is irradiated to the region including. Adjustment of the beam size and focusing can be performed not only by combining two convex lenses as in this embodiment but also by a combination of a concave lens and a convex lens, or a combination of a convex mirror or a concave mirror.

FIG. 5 shows a high-power near-infrared or far-infrared laser beam whose transmission optical system is difficult to use as the infrared laser beam, and furthermore, a collection of KrF excimer laser pulse beams due to the limitation of light resistance. This is a configuration example in which it is difficult to insert a mirror in the middle of light, and the infrared laser beam 4 is reflected and condensed by a concave mirror 16. The focused beam passes through the aperture of the concave concave mirror 16 'and reaches the metal material surface 7. The beam size of the KrF excimer laser pulse beam 10 is adjusted by the concave lens 17 and the concave mirror 1
After being reflected and condensed at 6 ′, it is applied to the infrared laser irradiation area of the metal material surface 7 or to an area including the infrared laser irradiation area.
In any case, high-density plasma is formed on the surface of the metal material by irradiation with the KrF excimer laser pulse beam, and the high-density plasma plays a role in transmitting the energy of the infrared laser beam to the metal material. Thus, in thermal processing using an infrared laser beam, the laser beam can be effectively used.

[0023]

According to the method of the present invention, the surface of a metal material is heated by irradiating an infrared laser beam, and when performing various processing, the absorption efficiency of the laser beam is increased, and the energy is applied to the metal material. In addition to the transmission, the reflection of the laser beam can be suppressed to prevent damage to the optical system and the like. The method of the present invention can be used to heat metals such as iron, nickel, cobalt, chromium, aluminum, copper, zinc, and tin, and alloys based on these, such as stainless steel, carbon steel, brass, copper alloy, and aluminum alloy. It can be suitably used for processing.

[0024]

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

Example 1 A peak power of 500 W at which the aluminum surface does not melt,
1 Nd: YAG laser beam under the condition of a beam diameter of 3 mm
Irradiation was performed for only milliseconds, and the time change of the intensity of the reflected beam from the surface was measured. Also, when a KrF excimer laser pulse beam having a pulse width of 22 nanoseconds and an energy density of 63 kJ / m ² is simultaneously irradiated in the middle of the Nd: YAG laser pulse beam, the time change of the reflected beam intensity of the Nd: YAG laser beam is measured. did. FIG. 6 shows a reflected beam intensity signal in the Nd: YAG laser beam alone irradiation among the reflected beam intensities thus measured.
FIG. 7 shows a reflected beam intensity signal when a KrF excimer laser pulse beam is simultaneously irradiated. 7, the simultaneous irradiation reduces the reflected beam intensity simultaneously with the KrF excimer laser pulse beam irradiation.
It can be seen that about 00 microseconds are maintained. That is, Nd: Y is applied for 200 to 300 microseconds by the simultaneous irradiation of one pulse of the KrF excimer laser pulse beam.
The absorption ratio of the AG laser beam is increasing.

Example 2 In Example 1, the peak power of the Nd: YAG laser beam was adjusted to 3.6 kW, the beam diameter was set to 0.1 mm, the frequency was set to 50 Hz, the average output was set to 180 W, and the pulse width was set to 1 millisecond. The rising of the Nd: YAG laser pulse beam and the KrF excimer laser pulse beam are made simultaneous,
Irradiation on US 304 stainless steel surface. As a result, although the maintenance time t of the high-density plasma is 1/3 to 1/5 of the Nd: YAG laser pulse t ', KrF
Microscopic observation showed that the simultaneous irradiation with the excimer laser pulse beam increased the average melt cross-section depth by about 10% as compared with the case of the single irradiation of the Nd: YAG laser pulse beam.

[Brief description of the drawings]

FIG. 1 is a schematic structural view of an example of a laser heating device for performing a method of the present invention.

FIG. 2 is a configuration diagram of another example of an optical system in a laser heating device for performing the method of the present invention.

FIG. 3 is a configuration diagram of another example of an optical system in a laser heating device for performing the method of the present invention.

FIG. 4 is a configuration diagram of another example of an optical system in a laser heating device for performing the method of the present invention.

FIG. 5 is a configuration diagram of another example of an optical system in a laser heating device for performing the method of the present invention.

FIG. 6 is a diagram showing a reflection waveform when a single Nd: YAG laser beam is applied in the first embodiment.

FIG. 7 is a diagram showing a reflection waveform when a Nd: YAG laser beam and a KrF excimer laser pulse beam are simultaneously irradiated in the first embodiment.

[Explanation of symbols]

 Reference Signs List 1 pulse generator 2 driver 3 near-infrared or far-infrared laser oscillator 4 near-infrared or far-infrared laser beam 4 'near-infrared laser beam 5,5' plane mirror 6,6 ', 6 "convex lens 7 metal material surface Reference Signs List 8 delay control device 9 KrF excimer laser oscillator 10 KrF excimer laser pulse beam 11 KrF excimer laser cut filter 12 photodetector 13 waveform storage device 14 laser irradiation optical system 15 KrF excimer laser beam mirror 15 ′ perforated flat mirror 16 concave mirror 16 ′ Perforated concave mirror 17 concave lens

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masafumi Yoneda 2217-14 Hayashi-cho, Takamatsu-shi, Kagawa Prefecture Within the Institute of Industrial Science and Technology, Shikoku Institute of Industrial Technology (72) Munehide Katsumura 22217-14 Hayashi-cho, Takamatsu-shi, Kagawa Industrial Technology (56) References JP-A-10-323773 (JP, A) JP-A-63-177414 (JP, A) JP-A-63-295093 (JP, A) JP-A-3-238192 (JP, A) JP-A-56-129340 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 26/00 B23K 26/12

Claims (1)

(57) [Claims] 1. A metal material surface is irradiated with an infrared laser beam, and upon thermal processing of the surface, a KrF excimer laser pulse beam is simultaneously irradiated to induce high-density plasma in the vicinity of the surface. A laser hybrid heating method characterized in that an infrared laser beam is absorbed by plasma.