JP2001353589A - Method and equipment of laser beam welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent oxidation of a sample in a high-power laser beam welding. SOLUTION: The sample is irradiated with a laser beam by passing the laser beam through a laser beam transmitting material whose transmitivity is 90% or greater in a chamber filled with a fluidizing inert gas. In this case, the laser beam transmitting material is not located on the inner wall of the chamber positioned in the extended direction of the normal line of the irradiated face, the laser beam is made to irradiate through a laser beam transmitting material whose transmitivity is 90% or greater and which has a form of a convex circle vertically directed downwards in the chamber, the sample is irradiated with the laser beam while the gas is fluidized in the chamber which is connected with the emitting head part of the laser beam by a guide pipe, and further the laser beam is made to irradiate by transmitting through an air curtain which is made by fluidizing the gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for preventing oxidation of a sample during laser welding.

[0002]

2. Description of the Related Art Laser welding is a method in which a laser beam is focused by a condenser lens, a sample is irradiated at a high energy density, and the sample is melted and joined by heat. It has various features, such as high accuracy and high efficiency, and is possible in the atmosphere. Starting with steel materials,
It is widely applied to welding of non-ferrous materials such as aluminum and copper.

However, since the sample is melted by irradiating a beam with a high energy density in the atmosphere, the temperature around the weld bead reaches a considerably high temperature. Preventive measures are required, and the condensing lens of the laser device is contaminated by spatter, fume, and soot from the sample, and the laser light is absorbed at that location, causing fluctuations in focal length and energy density. Therefore, these preventive measures have conventionally been required. Therefore, conventionally, these problems have been dealt with by spraying a shielding gas that shields the fusion zone onto the fusion zone while irradiating the laser with laser.

As an example of a shielding gas, for example, according to "Laser welding" (edited by Amada Laser Processing Research Group, Machinist Publishing (1996), p. 12), a center gas method in which a shielding gas is supplied from a nozzle coaxial with a laser beam, Furthermore, a side gas system that blows from the side is cited. However, there is no description of a specific sample as an example, especially in the case of side gas, depending on the pressure, penetration depth, humping bead, occurrence of porosity may occur, `` If the target position is slightly shifted, irregular bead Becomes
It is easily anticipated that considerable contrivance is required, as described in "Obstacles to practical use of this method", and this technique cannot be easily applied. This is a phenomenon that is easily assumed even in the center gas method. Therefore, in order to prevent oxidation of a steel material or aluminum, molybdenum, or the like, which is easily oxidized, there remains a problem which cannot be solved simply by spraying a shielding gas. This method is disclosed in JP-A-5-3
1583, JP-A-9-150290, JP-A-10-32
Although 8876 is employed, similar problems are easily envisioned.

As another oxidation preventing method, Japanese Patent Laid-Open No.
No. 71795 proposes laser welding in water, but there is a problem that the target material is limited because it is difficult to apply to a material such as steel that easily forms a corrosion product.

In general, in order to prevent oxidation, it is easy to enclose a sample with an inert gas to cut off oxygen. However, as the output increases, the glass melts due to radiant heat from the sample irradiated with the laser, and spatter, fumes, and soot adhere to the glass surface and hinder the passage of the laser. Therefore, there is a problem that cannot be simply applied.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to improve the oxidation prevention during laser welding of any sample at a high output, which is a problem of the prior art, and to improve the inside of a chamber filled with a gas for preventing oxidation. Accordingly, there is provided a method and an apparatus capable of laser welding without damaging an apparatus such as a glass which transmits a laser.

[0008]

In order to solve the above-mentioned problems, the present invention provides a method for welding a sample while irradiating a laser, wherein at least one gas selected from argon gas, helium gas and nitrogen gas is used. In a chamber filled with flowing gas with the laser transmitting material side upstream and the sample side to be welded downstream,
% Of the laser transmitting material is transmitted through the sample, and the sample is irradiated. The laser transmitting material is not installed on the inner wall of the chamber located in the direction perpendicular to the irradiation surface, and the laser transmits 90% or more of the laser in the chamber. Irradiating by transmitting a laser-transmissive material having a characteristic and a convex circular shape in a vertically downward direction, and irradiating the sample with a laser while flowing the gas into a chamber connected to a laser emission head and a guide tube. Another object of the present invention is to provide a laser welding method for irradiating a laser beam through an air curtain in which a gas flows, and an apparatus therefor.

As a specific method and apparatus for this purpose, for example, as shown in FIG. 1, a sample 4 is irradiated by transmitting a laser transmitting material 2 in a state where a laser emitting head 1 is inclined obliquely from a vertical direction. It is provided that an inert gas 9 is filled with the laser permeable material 2 as the upstream, and a heat resistant material is placed on the inner wall 8 of the chamber located in a direction normal to the irradiation part (welding position) so that the laser permeable material 2 is not installed. I do. As a result, spatter, fumes and soot are passed through the gas and
Further, the radiant heat from the sample is absorbed mainly by the heat-resistant material, so that the heat is hardly transmitted to the laser transmitting material 2 and the laser welding is performed in an inert gas filled state without damaging the laser transmitting material 2, thereby preventing oxidation.

As shown in FIG. 2, when a laser is irradiated through a laser transmitting material 12 having a vertically downwardly convex circular shape, spatter, fumes, and soot from a sample are caused by the flow of the gas 9 in the same manner as described above. It does not adhere because it is displaced from the convex circular laser transmitting material 12, and furthermore, because the 12 has a convex circular shape, it disperses heat from the sample in multiple directions. It can also prevent damage. In this case, the laser emission head 1 does not need to be tilted.

Further, as shown in FIG. 3, even if the laser transmitting material 2 or 12 is not provided, if the connection guide tube 13 for connecting the laser emission head and the chamber is provided and shielded by the connection band 14, the inert gas in the inert gas can be obtained. Enables laser welding.

In the case of welding by the above method, the laser emitting head 1 may be moved in the welding direction, or, as shown in FIG.
May be introduced into the chamber 3.

As shown in FIG. 4, if a laser is transmitted in a state where the air curtain 20 is formed, the sample can be irradiated without the need for the laser transmitting material 2 or 12, and the gas required for forming the air curtain can be supplied to the chamber. If air is blown into the inside, gas replacement can be performed at the same time, and oxidation can be economically prevented.

The reasons for limiting the present invention are described below.

The reason for limiting at least one gas selected from among argon gas, helium gas, and nitrogen gas into the chamber while flowing the gas with the laser-permeable material side upstream and the sample side to be welded downstream. First shown.

Argon gas, helium gas, and nitrogen gas are shielding gases at the time of general welding, and they are essential for preventing oxidation because they can drive out oxygen and perform laser welding in an oxygen-free state. These may be used alone or as a mixture, so that the number is limited to at least one. For example, helium gas has excellent shielding properties but is expensive,
It may be used in combination with a low-cost nitrogen gas. Also,
Spatter, fume and soot are scattered during welding,
When the gas is made to flow by making the laser-transmissive material 2 upstream and the sample 4 to be welded downstream, the gas flows away from the material 2 and does not adhere to the surface of the laser 2. Further, the heat from the sample by the laser irradiation is caused to flow by the flowing gas. 2, because it is difficult to transmit to them.

Next, the laser is transmitted through a material having a laser transmissivity of 90% or more to irradiate the sample, and the laser-transmissive material is not provided on the inner wall of the chamber located in the direction normal to the irradiation surface. At that point, the reason for the limitation of the heat-resistant material is described.

When the laser transmittance is less than 90%, as shown in Table 1, the laser-transmissive material accumulates heat during the laser irradiation, and thus has a high risk of causing damage such as melting or cracking. . The reason that the laser-transmissive material is not provided on the inner wall of the chamber located in the normal direction of the irradiation surface is that the radiant heat generated from the laser irradiation part of the sample is the inner wall of the chamber located in the normal direction which is the closest distance. When a low-melting-point laser-permeable material such as glass is provided at that location, damage such as melting and cracking is caused. Therefore, it is necessary to provide a heat-resistant material.

The reason for limiting the transmission of the laser through a laser transmitting material having a laser transmittance of 90% or more and a vertically convex circular shape in the downward direction is as described above. The reason for transmitting the laser transmitting material having a convex circular shape downward in the vertical direction is that the radiant heat from the sample is dispersed in multiple directions and it is possible to prevent the laser transmitting material from being damaged because it is not concentrated at one pole. That's why.

The reason for performing laser welding in the chamber connected to the laser emission head and the guide tube is that, even if the laser transmission material 2 or 12 is not provided, if the connection band 14 is used to shield the laser in an inert gas, This is because welding can be performed.

The reason for irradiating the laser beam by passing it through an air curtain through which the gas flows is that the inert gas in the chamber is not released and the laser beam is not lost without using a laser permeable material such as glass. This is because irradiation can be performed inside. In order to form this air curtain, a high-speed gas supply device 18 is required so that the gas flows parallel to the laser incident wall surface of the chamber 3, and a device 19 that receives and sucks the gas because it is high-speed. Further, since it is uneconomical to discharge the gas to the outside air, 19 has a mechanism capable of directly supplying the gas into the chamber.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention can improve the prevention of oxidation of high-power laser welding for any sample, and provides an apparatus such as glass for transmitting laser in a chamber filled with a gas for preventing oxidation. The present invention provides a method and an apparatus that enable laser welding without causing damage, and can be implemented as follows.

[0023]

EXAMPLE In a butt YAG laser welding of SUS304 steel and SPCC steel having different thicknesses, the chamber was filled with at least one gas selected from argon, helium and nitrogen gas, and after sufficiently purging oxygen, The laser average output, the properties of the weld material (tensile fracture locations, defects due to X-ray transmission images), the oxidation state, and the state of the device after welding were observed. The YAG laser was used at a frequency of 10 Hz, a pulse width of 10 ms, and a sample transport speed of 200 mm / min. The chamber was basically selected from those shown in FIGS. For comparison, the difference between the upstream and downstream directions of the gas, the stop of the flow state, the welding by air filling, the installation of the laser permeable material at the position of the chamber inner wall 8 located in the direction of extension of the normal line of the laser irradiation surface, the installation of the guide tube 13 Tests were performed on the presence or absence of the connection band 14 and the presence or absence of the air curtain. A for laser transmitting material
Transparent glass with increased transmittance by R coating was used. Detailed conditions are shown in Tables 2-1 and 2-2.

The results are shown in Tables 2-3 and 2-4. If the tensile fracture point is the base metal part, it is evaluated as "good", if it is a welded part, it is evaluated as "poor", and if the defect has at least one size of 0.5 mm or more, it is unacceptable. ○ The oxidized state was evaluated by visual observation. When the color was blue or brown, etc., it was evaluated as "x" with oxidation, and when it was not colored at all, it was evaluated as "o" without oxidation. The status of the equipment after welding is evaluated as x when a failure occurs and cannot be used for the next test.
And

[0025]

[Table 2]

Comparative Example 1 was a case where the atmosphere gas to be filled in the chamber was air, and oxidation was not prevented during laser welding.

Comparative Example 2 is a flow reverse to that of the present invention in which the atmosphere gas in the chamber is introduced from the gas outlet pipe 6 and discharged from the gas inlet pipe 5 in FIG. 1, but the spatter, fume, and soot are generated. Since it adhered to the laser transmitting material 2, the glass as the laser transmitting material was melted by the absorption of the laser, and could not be used.

Comparative Example 3 is a case in which the gas inlet pipe 5 and the gas outlet pipe 6 are closed after the chamber is filled with the atmosphere gas, and the flow of the atmosphere gas in the chamber is eliminated. As a result, spatter, fumes, and soot slightly adhered to the glass, which is a laser transmitting material, and a small amount of oxygen remaining in the chamber reacted to cause slight oxidation.

In Comparative Example 4, the sample was irradiated vertically as shown in FIG. 2 without tilting the laser emission head 1 as shown in FIG. 1, and the inner wall of the chamber positioned in the direction normal to the laser irradiation surface was extended. Radiation heat from the laser irradiating part melted the glass because it became a glass instead of a heat-resistant material, and eventually the glass became cracked and unusable. Furthermore, oxidation occurred due to air leaking therefrom, and further, the laser was not uniformly irradiated on the welded portion, and defects were generated and welding was insufficient, resulting in a tensile fractured portion being a welded portion.

Comparative Example 5 is a case where the connection band 14 shown in FIG. 3 was not provided. Since the connection band was not tightly shielded, air was mixed in from the 14 locations and oxidation occurred.

In Comparative Example 6, the transmittance of the laser transmitting material was 90.
%, The transmittance was poor and heat was easily accumulated, and the glass was broken and cracked. Therefore, as in Comparative Example 4, oxidation, defects, and breakage of the weld occurred.

Comparative Example 7 was a case where the convex circular laser transmitting material 12 of FIG. 2 was attached in an upward convex shape. Radiant heat from the sample was accumulated at 12, melted, and cracked. As a result, oxidation, defects, and breakage of the weld portion occurred as described above.

Comparative Example 8 is a case where the air curtain shown in FIG. 4 was not provided, and oxidation occurred because the interior of the chamber could not be filled with an inert gas.

On the other hand, in the embodiments of the present invention, oxidation, defects,
It shows good results without damage to the equipment after welding.

[0035]

The present invention can be implemented as described above.
There is a remarkable effect of solving the above-mentioned technical problem. In other words, according to the present invention, oxidation at the time of laser welding can be prevented even at a high output, and the industrial merit is great.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of the laser welding method of the present invention in which a laser is irradiated into a chamber through a laser transmitting material.

FIG. 2 is a front view showing an example of the laser welding method of the present invention in which laser irradiation is performed vertically through a laser-transparent material having a convex circular shape.

FIG. 3 is a front view showing an example of the laser welding method of the present invention using a chamber provided with a guide tube connecting a chamber and a laser emission head.

FIG. 4 is a front view showing an example of the laser welding method of the present invention for irradiating a laser into a chamber through an air curtain.

[Explanation of symbols]

1: laser emission head 2: laser transmission material 3: chamber 4: sample (in chamber 3) 5: gas inlet tube 6: gas outlet tube 7: sputter, fume, soot (in chamber 3) 8: laser of sample 4 9: Gas before filling 10: Gas after filling 11: Laser beam 12: Convex circular laser transmitting material 13: Connection guide tube between laser emission head and chamber 14: Connection band of 1 and 13 15: Sample transport belt (in chamber 3) 16: Sample transport roller (in chamber 3) 17: Sample transport mechanism (in chamber 3) 18: High-speed gas supply machine 19: Gas suction and chamber Gas supply machine 20: air curtain

Table 1 is a table showing the relationship between laser transmittance and melting and cracking of glass when glass is used as the laser transmitting material.

Table 2 is a table showing conditions and results of the examples.

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Masaomi Oguma 3-22 Tanozawa, Ichikawa-cho, Hachinohe-shi, Aomori Prefecture Hachinohe Intelligent Plaza Co., Ltd. BA00 CH07 CH08 CJ01

Claims (7)

[Claims] 1. A method for welding a sample while irradiating a laser, wherein at least one gas selected from argon gas, helium gas, and nitrogen gas is supplied with the laser-transmitting material side upstream and the sample side to be welded downstream. 90% laser in chamber filled with flowing gas as
A laser welding method characterized by irradiating a sample by transmitting the above laser-transmissive material and not installing the laser-transmissive material on the inner wall of a chamber located in a direction normal to the irradiation surface. 2. A laser according to claim 1, wherein a laser is transmitted through a laser transmitting material having a laser transmissivity of 90% or more and having a vertically convex circular shape. Laser welding method 3. A laser beam is applied to a sample placed in a chamber in a state where the gas described in claim 1 is filled while flowing into a chamber connected to the laser emission head section by a guide tube. Laser welding method 4. When performing laser welding in a chamber in a state where the gas according to claim 1 is charged while flowing the gas,
A laser welding method characterized by irradiating a laser through an air curtain through which a gas flows. 5. A gas inlet tube 5 and a gas outlet tube 6 are connected to a chamber 3, and a laser transmitting material 2 or 12 is provided on a laser incident surface side, and an inner wall of a chamber located in a direction normal to a laser irradiation surface of a sample 4 is extended. 8 is a laser welding apparatus characterized by having a heat-resistant material. 6. A gas inlet pipe 5 and a gas outlet pipe 6 are connected to the chamber 3, and a guide pipe 13 connected to the laser emitting head 1 is connected to the laser incident surface side. A laser welding apparatus characterized in that the guide tube (13) is fixed and shielded by a connection band (14). 7. A high-speed gas supply unit 18 and a facility 19 for sucking the gas and supplying the gas into the chamber are connected so that the gas flows parallel to the laser incident wall surface of the chamber 3, and the gas flows through the chamber. A gas outlet pipe 6 for discharging the gas, and a heat-resistant material provided on a chamber inner wall 8 located in a direction normal to the laser irradiation surface of the sample 4.