JPH0242307B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device that enables laser processing in a vacuum atmosphere, and is capable of depositing a vapor deposition substance onto a laser transmission window provided in a vacuum processing chamber. Relating to a device for preventing.

[Conventional technology]

FIG. 6 is a sectional view showing an example of a conventional laser processing apparatus in the atmosphere. In the figure, 1 is a laser beam, 2 is a lens for condensing the laser beam 1 and irradiating it onto the workpiece 3, and 4 is a lens ejected from the same direction as the laser beam 1 toward the workpiece 3. 5 is the evaporated substance such as the workpiece 3, 6 is the nozzle of this device,
15 is the traveling direction of the laser beam 1 with respect to the workpiece 3.

When welding is carried out using such equipment,
Plasma is formed near the laser irradiation area. Since plasma absorbs or reflects laser light, the amount of laser light reaching the workpiece is significantly reduced, making it impossible to obtain the required penetration depth. Also, workpiece 3
The formation of the bead 17 in the molten part becomes unstable, and the cross section of the weld bead (see Figures 8a and b) contains microporosity (small pores) or pinholes 16 due to the instability of solidification of the molten metal. The occurrence of (see Figure 8a) is observed.

FIG. 7 is a sectional view showing a conventional laser welding method within the vacuum processing chamber 8. As shown in FIG.

In the figure, 1 is a laser beam, 3 is a workpiece, 5 is an evaporated material of the workpiece 3, 7 is a laser transmission window at one end of the vacuum processing chamber 8 through which the laser beam 1 passes, and 15 is a workpiece. 3. This is the traveling direction of the laser beam 1 with respect to 3.

When laser processing is performed in a vacuum chamber (600 Torr or less) in this way, problems such as the occurrence of microporosity in the apparatus shown in FIG. A problem arises in that it adheres to the transmission window 7 and prevents the laser beam 1 from passing through. As a countermeasure to this problem, an air curtain method (aero
There is a method of partitioning the vacuum processing chamber 8 from the outside using the dynamics window method, but this method is applicable only when the pressure in the vacuum processing chamber 8 is approximately 50 Torr or more, and when the pressure is lower than that, the vacuum processing chamber 8 is separated from the outside. The pressure in chamber 8 cannot be maintained. As shown in FIG. 5b, the effect of pressure reduction becomes noticeable when the pressure is below 30 Torr, and in the case of such a low pressure, the use of the transmission window 7 is inevitable.

[Problem that the invention seeks to solve]

In the conventional atmospheric laser processing equipment as described above, plasma is generated by the interaction between the center gas for protecting the lens, evaporated matter from the workpiece, and the laser beam, which reaches the workpiece. There were problems with weakening the laser beam and forming pinholes.

In addition, in a laser processing device that is simply installed in a vacuum container, vaporized substances generated from the workpiece during laser processing may contaminate the laser transmission window, weakening the laser beam and reducing processing efficiency. Thermal distortion occurred in the laser transmission window, causing damage.

This invention was made in order to solve the above-mentioned problems, and the transmission window is not contaminated by vapor deposited substances from the workpiece during vacuum processing.
To enable efficient processing.

[Means for solving problems]

This invention was made to solve the above-mentioned problems, and includes a container connected to a vacuum pump and a beam guide having an uneven inner diameter inside a laser beam transmission window of the container. It is.

[Effect]

In this invention, a workpiece is inserted into a vacuum processing chamber (pressure vessel) having a laser beam transmission window, and a beam guide having an uneven inner diameter is provided between the transmission window and the workpiece, and the laser beam is transmitted through the workpiece. Processing is applied to the workpiece by irradiating the beam. The shape to be processed can be changed by moving the laser beam and the workpiece relative to each other as necessary.
In addition, the plasma vapor generated during processing is diffused into the vacuum chamber and removed, and the laser beam is prevented from advancing because it is restricted from reaching the transmission window by the beam guide, which has irregularities on the inner diameter side. Processing can be continued without any problems.

〔Example〕

FIG. 1 is a sectional view of a laser processing apparatus showing an embodiment of the present invention. In the figure, 1 is a laser beam, 8 is a vacuum processing chamber of 600 [Torr] or less, and 3 is inside the vacuum processing chamber 8.
A workpiece is irradiated with the laser beam 1 that has passed through a transmission window 7 provided in the workpiece, 5 is an evaporated substance generated from the workpiece 3, and 9 is between the workpiece 3 and the transmission window 7. , and a beam guide 13 having an uneven inner surface, which is provided in contact with the transmission window 7 side, and 13 is a vapor deposition prevention gas (He, Ar,
(N ₂ , CO ₂ , air, etc.), 15 is the moving direction of the laser beam 1 with respect to the workpiece 3, and a vacuum pump is connected to the vacuum processing chamber 8, but is omitted.

Next, the operation of this device will be explained. When the laser beam 1 is irradiated around the workpiece 3 installed as shown in the figure with atmospheric pressure of air, the workpiece 3 begins to melt. The power density of laser beam 1 is
Since it is as high as 10 ⁶ to 10 ⁷ [Watt/cm ² ], evaporated substances 5 are generated from the workpiece 3. If there is no beam guide 9, this evaporated material 5 will contaminate the inside of the transmission window 7 and cause damage, but if the beam guide 9 with the uneven inner diameter is installed as shown in the figure, this vapor Although it adheres to the outer surface of the beam guide 9, it is difficult to penetrate into its inner diameter side. However, under atmospheric pressure, it will eventually contaminate the transmission window 7 at the top, weakening the light beam and causing damage to the window. In addition, in such a state, gas is drawn into the inside of the bead 17 of the workpiece 3 and microporosity 16 (small pores) is generated. Therefore, vapor deposition prevention gas 1
3 flows from above to the inner diameter side of the beam guide 9,
The evaporated substance 5 is pushed back downward by the flow of the vapor deposition prevention gas 13 and the unevenness provided on the beam guide 9, and no longer contaminates the transmission window.
Since the concentration of the evaporated substance 5 is high, the laser beam 1 tries to reach the workpiece 3 by scattering or absorption.
weaken.

Therefore, if the inside of the vacuum processing chamber 8 is sucked to 600 [Torr] or less using a vacuum pump (not shown), the penetration depth of the workpiece 3 will be increased extremely (5th
(see Figures a and b). FIG. 8b shows a case where the pressure inside the vacuum processing chamber 8 is set to 1 [Torr]. As is clear from this figure, no pinhole 16 is observed in the cross section of the penetration.

Figure 2 a, b, c and Figure 3 a, b, c, d
2A and 2B are cross-sectional views showing various shapes of the beam guide 9 according to the present invention. In FIGS. 2a to 2c, one to three rectangular recesses 11, a tapered nozzle-shaped recess, or an arc-shaped recess 11 are shown, but any of them are effective.

3a to 3d show an example in which it is effective to provide a large number of evaporated substance discharge holes 14 penetrating the side wall in addition to the above-mentioned uneven portions. It is shown that the evaporated substance discharge hole 14 may be provided in the beam guide internal concave portion 11 or in the beam guide internal convex portions 10 and 12.

In addition, the beam guide 9 shown in Figures 2 and 3 above is all equipped with an introduction path for the vapor deposition prevention gas 13, and a cylindrical nozzle made of SUS304 stainless steel is used. 〕×Small inner diameter 40
[mm] x large inner diameter 65 [mm].

In the embodiment shown in FIG. 1, the vacuum processing chamber 8
Evacuation was performed using a rotary pump and a diffusion pump (not shown). From above the beam guide 9, He,
Bubbled with Ar or _N2 gas. In the high vacuum range (≦10 ^-1 Torr), both the rotary pump and the diffusion pump are operated, and in the low vacuum range (>
10 ^-1 Torr), only the rotary pump is operated;
A predetermined degree of vacuum was obtained by adjusting the amount of gas blown from above each beam guide nozzle.

Workpiece 3 is made of SUS304 steel with a plate thickness of 10 mm.
Welding was carried out by keeping the carbon dioxide laser power constant at 5 kW, varying the degree of vacuum in the vacuum processing chamber 8 from 1×10 ⁻³ to 760 Torr, and varying the welding speed from 0.25 to 5 m/min. The lower the pressure, the more the amount of evaporated substances 5 generated during welding.
The lower the welding speed, the more the amount. For comparison, a straight-shaped beam guide 9 (inner diameter 40 mm) is shown in Figure 4.
For example, when welding under the conditions of an atmospheric pressure of 1 Torr, a welding speed of 0.5 m/min, and a power of laser beam 1 of 5 kW, the KCl transmission window 7 appeared just 10 seconds after welding started. Damaged. In this case, a large amount of evaporated substance 5 was deposited on the transmission window 7, and the transmission window 7 was almost opaque.

On the other hand, when the beam guide 9 of the present invention is used, the atmospheric pressure is 1×10 ^-3 Torr, the welding speed is 0.25 m/min, and the power is
Even when laser welding was performed continuously for 15 minutes under the condition of 5 kW, no metal vapor was deposited on the laser transmission window, confirming that the present invention is highly effective.

As described above, it has been revealed that by using the beam guide 9 whose inner diameter changes discontinuously in an uneven manner, it is possible to prevent the vaporized substance 5 from being deposited on the laser transmission window 7.

Although a cylindrical beam guide 9 was used, the same vapor deposition prevention effect can be expected by discontinuously changing the diameter or size of the inside of the guide in any shape such as rectangular or hexagonal. Needless to say.

In addition, although laser welding was taken up in the example, it has been confirmed that surface treatment processes such as cladding and heat treatment have the same vapor deposition prevention effect.
The present invention can be effectively utilized for all laser processing performed in a vacuum atmosphere. In particular, the effects of the present invention are remarkable in processing performed in a vacuum atmosphere at a pressure of 600 Torr or less.

Furthermore, the material of the transmission window 7 of the device according to the present invention includes
It should be noted that ZnSe, KCl or Ge plates were used.

Next, we will add an explanation of the diagrams in Figures 5a and 5b. FIG. 5b shows the influence of the pressure of the welding atmosphere on the penetration depth. In welding under atmospheric pressure, saturation of penetration depth is observed in the low welding speed range, but when the pressure of the welding atmosphere is below 350 Torr, penetration is not saturated and increases as the welding speed decreases. For reference, the penetration depth of electron beam welding is also shown, but the penetration depth of laser welding in a vacuum atmosphere is extremely close to that of electron beam welding. The reason that penetration becomes saturated in the low welding speed range during welding under atmospheric pressure is due to the generation of a large amount of plasma.

〔Effect of the invention〕

As described above, in laser welding in a vacuum atmosphere using the beam guide or the like according to the present invention, an increase in penetration depth and an improvement in bead shape, as well as a significant improvement in porosity resistance due to this, are achieved. Since the progress of contamination of the laser transmission window is suppressed over a long period of time, laser processing in a vacuum atmosphere, which has been considered difficult in the past, can be performed stably over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a laser processing device showing one embodiment of the present invention, FIGS. b, c, d are other embodiments of this invention,
A cross-sectional view showing the configuration of a beam guide with an outlet,
Figure 4 is a cross-sectional view of a straight beam guide, Figures 5a and b are penetration depths, welding speeds,
Diagram showing the relationship between atmospheric pressures, Figure 6 is a cross-sectional view showing a conventional laser welding method in the atmosphere, Figure 7 is a cross-sectional view showing a conventional laser welding method in a vacuum processing chamber, and Figure 8 a. , b are cross-sectional views of the bead of the laser welded part, a is a cross-sectional view under atmospheric pressure, and b is a cross-sectional view under vacuum (1 Torr). In the figure, 1 is a laser beam, 3 is a workpiece, 5 is an evaporated substance, 7 is a transmission window, 8 is a vacuum processing chamber, 9 is a beam guide, and 13 is a vapor deposition prevention gas. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] 1. A laser processing device comprising: a vacuum vessel connected to a vacuum pump; and a beam guide having an uneven inner diameter provided inside a laser beam transmission window of the vacuum vessel. 2. The laser processing apparatus according to claim 1, wherein the pressure inside the vacuum container is 600 [Torr] or less. 3. The laser processing apparatus according to claim 1, wherein the beam guide is configured to have an evaporated substance exhaust port on a side wall, and a vapor deposition prevention gas is introduced from one end of the beam guide. 4. The laser processing apparatus according to claim 3, wherein the vapor deposition prevention gas is a gas such as He, Ar, _N2 , _CO2 , or air.