JP2913018B2 - Metal surface treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a technique for melting a metal material surface by arc discharge, and dissolving another metal material or another material in the melted portion to reform the arc, whereby the arc fluctuates irregularly. The present invention relates to a method for stabilizing non-uniform processing by using laser beam irradiation in combination and efficiently modifying a metal material surface.

[0002]

2. Description of the Related Art A metal material is heated and melted by utilizing heat generated by arc discharge, and the metal used as an electrode is transferred to a base material to modify the surface of the metal material or to join the metal material. It is well known to do. However,
In this method, when the metal used as the electrode melts,
Since the size of the droplet formed by the working conditions is not always constant, the arc length tends to fluctuate with the transfer of the droplet, the arc tends to be unstable, and the metal material moves at high speed When this is done, this tendency is further strengthened, so that there is a disadvantage that processing cannot be performed at a high speed.

[0003] Other treatment methods for modifying the surface of the metal material include a method of irradiating a laser under a specific atmosphere to cause a thermochemical change on the metal surface, and a method of modifying the surface of the metal material. There are known methods of coating with a material and irradiating it with a laser to fuse it with the base material.However, using these methods to treat a large area of metal material at high speed, a special method is required. Since a high-power laser oscillator is required, the cost is inevitably high, and the utility is poor.

[0004] In addition, vacuum deposition, chemical vapor deposition, plating and the like are also known. However, in these methods, the surface of the base material is covered with a film made of a foreign material, so that the adhesion is not always sufficient. Use range is limited.

[0005]

SUMMARY OF THE INVENTION The present invention overcomes the drawbacks of the conventional method for treating the surface of a metal material using an arc, and provides a method for modifying the surface of a metal material at a high speed with a stable arc. It was made for the purpose of providing.

[0006]

The present inventors have conducted various studies on a method of modifying the surface of a metal material using an arc, and as a result, have found that when the surface of a metal material is modified by an arc, laser irradiation is performed. In this case, the arc is stabilized and the laser absorption efficiency is improved, even if the processing is performed while moving the material such that the poles of the material surface move irregularly in the processing of the arc alone at a high speed. Finds that the behavior of the arc can be controlled by
The present invention has been accomplished based on this finding.

That is, according to the present invention, an arc is generated between a metal material surface and a metal electrode, the metal material surface is melted, and a part of the metal constituting the electrode or a reactive gas in the atmosphere is introduced into the metal material. In the method of modifying the surface of a metal material while melting, a metal electrode is fixed, and the molten material is irradiated with the laser beam while moving the metal material and oscillating the laser beam in a direction intersecting the moving direction. And a method for treating a metal surface.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION There is no particular limitation on the metal material that can be surface-treated by the method of the present invention, and any metal material that has been surface-modified by arc-only treatment can be used. Can be.

For example, when a tungsten electrode is used in an inert gas atmosphere and the surface of a steel material or an aluminum alloy is subjected to an arc treatment, the periphery of the electrode material is coated with a flux, and the alloy element is contained in the flux as required. When adding and arc-treating the surface of various metal materials, titanium is melted and consumed in an inert gas atmosphere such as argon or helium, or in a reactive gas atmosphere such as carbon dioxide or nitrogen gas. When the surface of a metal material such as an alloy is subjected to arc treatment, when the metal or alloy coating previously formed on the surface of the metal material is nitrided using an arc in a nitrogen atmosphere to harden the surface and change the color tone. It can be suitably used when the sealing treatment of the thermal spray coating is performed using an arc.

Next, as a power source for arc generation in the method of the present invention, a power source commonly used in ordinary arc welding, for example, a Tig (Tungsten insert)
gas; TIG) power supply, MIG (Metal in)
It can be used irrespective of drooping characteristics and constant voltage characteristics such as a power supply for rt gas (MIG). The electrode may be a non-consumable electrode or a consumable electrode, and is not particularly limited as long as it is an electrode that has been used for ordinary arc welding. It can be appropriately selected from those that have been used.

The arc current at this time varies depending on the type of the power source for arc welding and the length of the arc used.
The range is from 0 to 1500A.

On the other hand, as a laser used together with the melting by the arc, a carbon dioxide laser or a YAG laser which can be focused by an optical system and has a power density for melting the surface of the metal material is used. The type may be a continuous oscillation type or a pulse oscillation type.

Next, a preferred embodiment of the method of the present invention will be described with reference to the accompanying drawings. FIG. 1 is an explanatory view showing the structure of an example of an apparatus used to carry out the method of the present invention. A laser beam 1 is converged by a condenser lens 2 and a tungsten electrode 4 and a gas nozzle 5 are provided around the beam 1. The TIG welding torch is placed, and a voltage is applied between the tungsten electrode 4 and the material 6 from the welding power source 3. The material 6 is fixed on an XY table 7 for driving the material. From the gas nozzle 5, as shown by the arrow, the shielding gas 11
For example, argon is introduced. Next, in order to facilitate the arc start, the high-frequency electrode 8 is arranged between the tungsten electrode 4 and the material 6 or the tub plate (disposal plate) 10 by using the high-frequency generator 9, and a spark is generated through this. .

In FIG. 1, A is the intersection between the central axis of the laser beam and the material surface, B is the intersection between the tungsten electrode and the material surface, F is the focal position of the beam, α is the inclination angle of the tungsten electrode, and a is the beam. Represents the distance between the focal point of the laser beam and the surface of the material, b represents the distance between the tungsten electrode and the material surface, and c represents the distance between the beam center axis and the electrode tip. Note that d indicates the distance between A and B, and this value is determined by c, b, and α.

FIG. 1 shows an example in which a TIG arc is used. If a tungsten electrode is connected to the positive side of a DC power source to make it reverse polarity, the electrode is severely consumed. Therefore, it is connected to the negative side to make it positive. ing. Therefore, when the melting efficiency of the consumable electrode is increased by using the MIG arc, the reverse polarity is advantageous.

In FIG. 1, the focal position F of the beam is on the upper side of the material. However, in order to obtain a plume by a stable laser (a gas which is ionized by the laser or heated to a high temperature and shines brightly), a laser output is required. Depending on the magnitude of the arc current or the magnitude of the arc current, it may be better to set the focal point to be focused inside the material.

Although the inclination angle α of the tungsten electrode in FIG. 1 can be arbitrarily selected, in relation to b and c,
If it is too large, the gas nozzle 5 contacts the beam, and if it is too small, it contacts the material 6,
When a gas nozzle having an outer diameter of about 25 mm is used, α is preferably set to about 40 ° to 70 °.

If b and c in FIG. 1 are made larger than 40 mm and 10 mm, respectively, the effect of the combined use is lost, so that it is necessary to set them below this. However, when the arc current increases, this numerical value can be slightly increased.

[0019]

Next, the present invention will be described in more detail by way of examples, which should not be construed as limiting the present invention.

REFERENCE EXAMPLE In the apparatus shown in FIG. 1, a condensing lens 2 made of ZnSe having a focal length of 254 mm so that the focal point F enters 3 mm from the surface of the material, b = 15 mm, c = 8. 6
The tungsten electrode 4 was arranged so that 6 mm and α = 60 ° C. The distance d between AB at this time is 0. The current setting of the welding power source 3 was 100 A. A stainless steel having a thickness of 6 mm was used as a metal material, and argon supplied at a rate of 60 L / min was used as a shielding gas.

In such an apparatus, an arc is generated on the tab plate 10 by using the high-frequency power source 9 and, at the same time, a laser whose output is set to 2 kW is irradiated on the tab plate.
-The Y table 7 was moved at a speed of 200 mm / s in the direction in which the arc was at the advance angle, that is, in the right direction in FIG.

FIG. 2A shows the time variation of the arc voltage under the above conditions, and FIG. 2B shows the oscilloscope waveform showing that of the arc alone. As can be seen, in the case of the arc alone, the melted portion becomes discontinuous,
Although the fluctuation of the arc voltage is large, when the laser of 2 kW and the TIG arc current of 100 A are used in combination, the arc voltage is stable and a continuous good fusion zone is formed.

Under the above conditions, if the laser is stopped in the course of forming the fusion zone by using both the laser and the arc, and the fusion zone is formed by the arc alone, the portion using the laser and the arc together has a good linear fusion zone. However, the portion of the arc alone became a discontinuous and stepped-stone-like molten portion. From this, it is clear that it is impossible to use the arc alone, and a practically usable fused portion was obtained by using the arc and the laser together.

FIGS. 3 (a) and 3 (b) are, respectively, a cross-sectional shape of the melted portion obtained by using both the laser and the arc under the above conditions, and a metallographic photograph showing the same when the laser is used alone. is there. Although the power consumption of the arc is approximately 2 kW, which is almost the same as the laser output of 2 kW, the cross-sectional area of the fusion zone differs by more than three times. This demonstrates that the combined use of arc and laser increases the efficiency of laser energy input to the material.

From these results, the following can be understood. (1) A pole of an arc is formed in a portion irradiated with a laser beam, and the metal material in this portion is melted. In this part, the surface area of the fusion zone is smaller than the cross-sectional area of the laser beam because the laser has a high reflectivity on the material surface. (2) Since the pole of the arc is smaller than the melting portion, it moves around the surface of the melting portion and also melts the periphery of the melting portion formed by the laser, so that the surface area of the melting portion increases and becomes larger than the cross section of the laser beam. (3) In this way, the entire cross section of the laser beam is irradiated on the molten metal, the reflectance of the laser decreases, and the efficiency of inputting the laser energy to the material increases.

Next, in this example, when the state of the plume and the arc was observed from a direction perpendicular to the moving direction of the material by a high-speed video apparatus, the arc passed through the plume, and the material formed by the laser beam was melted. It was found that the arc formed in the portion was flying toward the other pole, ie, the anode. This indicates that the arc transfer path is regulated by the plume, and that the anode point is fixed to the laser-melted part and moves only on the surface of the melted part. This is the reason why the arc is stable even when the material is moved at a high speed.

Example In the reference example, the same conditions as in the reference example were used except that the moving speed of the material was 30 mm / s, and the distance c between the center line of the laser beam and the tip of the tungsten electrode was 6.66 mm. Was moved in a direction perpendicular to the moving direction of the material at a rate of 8 times per second at an amplitude on the surface of the material of 8 mm, and the state of the plume and arc was observed from the moving direction of the material by a high-speed video apparatus. As a result, the tip of the arc is guided by the laser beam or plume that moves to the left and right with respect to the traveling direction of the material, and the other pole of the arc, that is, the anode point, is fixed to the laser irradiation part on the material. I found out.

In the apparatus shown in FIG. 1, since the arc voltage tends to be stabilized as the distance b between the material 6 and the tungsten electrode 4 decreases, the moving speed of the material is increased to increase the processing speed. It turns out that is possible.

Further, in the apparatus shown in FIG. 1, since the arc voltage tends to be more stable as the laser output and the arc current value are increased, it is possible to increase the processing speed by increasing the material moving speed. It turns out that it is.

[0030]

According to the present invention, it is possible to suppress irregular fluctuation of an arc generated when a surface of a metal material is modified by using an arc discharge by irradiation with a laser beam.
In addition, an effect comparable to that obtained by an energy corresponding to several times the output energy of the laser beam used is obtained as compared with the case of single laser beam processing.

[Brief description of the drawings]

FIG. 1 is an explanatory view of an example of an apparatus for carrying out the method of the present invention.

FIG. 2 is an oscilloscope waveform showing a voltage change when a laser and an arc are used together and when an arc is used alone.

FIG. 3 is a micrograph showing a metal structure of a cross section of a fusion zone when a laser and an arc are used together and when a laser is used alone.

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 Laser beam 2 Condensing lens 3 Welding power supply 4 Tungsten electrode 5 Shield gas nozzle 6 Metal material 7 XY table 8 High frequency electrode 9 High frequency power supply 10 Tab plate (discard plate) 11 Shield gas flow

Continued on the front page (72) Inventor Munehide Katsumura 2214-14 Hayashi-cho, Takamatsu-shi, Kagawa Prefectural Institute of Industrial Science and Technology Shikoku Institute of Industrial Technology (56) References Hiroyasu Yano et al. 2), p. 463-471, "Speeding up of surface treatment in combination with laser and arc" PHYSICS AND CHEMI STRY OF MATERIALS TREAMMENT, 24 [1] (1990), p. 62-65 "Hardening aluminum alloys by laser arc treatment" (58) Fields investigated (Int. Cl. ⁶ , DB names) C23C 8/00-10/60 C23C 24/00-26/02 B23K 26 / 00-26/18 B23K 31 / 00,35 / 00

Claims (1)

(57) [Claims] An arc is generated between a surface of a metal material and a metal electrode, the surface of the metal material is melted, and a part of the metal constituting the electrode or a reactive gas in the atmosphere is dissolved therein while melting the metal. In the method of modifying a material surface, the molten metal is irradiated with the laser beam while fixing the metal electrode, moving the metal material, and oscillating the laser beam in a direction crossing the moving direction. Metal surface treatment method.