JP2006167756A - Laser beam welding apparatus, and method for manufacturing welded structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a welding apparatus capable of performing a fusion welding while observing an object to be welded under inert atmosphere controlled in temperature and pressure, and to provide a method for manufacturing a welded structure by which the welded structure, which is excellent in the flexibility of working and has excellent mechanical characteristics without causing weld crack, can be obtained. <P>SOLUTION: The welding apparatus is provided with: a closed vessel 1, which is provided with a laser beam transmissive member 4 for transmitting the laser beam and can house the object to be welded; and a laser beam emitting part 15, which is arranged at the outer part of the closed vessel 1 and can emit the laser beam to the object housed in the inner part of the closed vessel 1 from the outer part of the closed vessel 1 through the laser beam transmissive member 4. The welded structure is manufactured by using the apparatus. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser welding apparatus and a method for manufacturing a welded structure.

  In the development of products using an intermetallic compound material such as a TiAl forged material, a joining technique capable of realizing an increase in the size of members and an improvement in yield is required.

  Intermetallic compound materials such as TiAl forgings are materials with excellent high temperature specific strength characteristics, but ductility at room temperature is extremely small, and when performing fusion welding such as laser welding on intermetallic compound materials, When the welded portion solidifies and shrinks after welding, there is a problem that the material cannot follow the shrinkage stress and causes a weld crack.

  Further, for example, since TiAl forging is composed of active elements Ti and Al, the welded portion structure and composition are likely to change depending on the atmosphere during joining, and the joint characteristics are also easily affected by the structure form. Therefore, when TiAl forging is welded in the atmosphere, Ti and Al react with oxygen and nitrogen to form brittle compounds (oxides and nitrides), which remain in the material as foreign matter. There was a problem of deteriorating.

  Therefore, as a method for bonding intermetallic compounds by controlling the groove temperature and atmosphere, a method of performing diffusion bonding or brazing at a high temperature and high pressure in a completely sealed furnace has been generally employed.

  In addition, while controlling the atmosphere by placing the welding object in the shield formed by blowing out the inert gas, and performing the temperature control by heating the welding object with a heat source different from the welding heat source, A method of performing laser welding has been proposed (see Patent Document 1 and Patent Document 2).

JP 2004-237327 A JP 2002-219589 A

However, when diffusion bonding or brazing is performed in a completely sealed furnace, the state of completion cannot be confirmed until the objects to be joined are put into the furnace, the prescribed temperature and pressure program is completed, and the furnace lid is opened. . Therefore, it is not possible to sequentially observe the state of the objects to be joined during joining, and when an abnormality occurs in the joining process, the operator cannot perform appropriate measures such as manually changing parameters. was there. In addition, these joining methods are also inferior in processing flexibility compared to fusion welding, which can be dealt with finely depending on the situation, because the quality of the joint part greatly depends on equipment and processes.
Moreover, even if laser welding is performed with a shield formed of an inert gas, the nitrogen content of the welded part can only be reduced to about 1%, and a practical strength of the welded part can be obtained. Can not.

  The present invention has been made in view of such circumstances, and a laser welding apparatus capable of performing fusion welding while observing a welding object in an inert atmosphere in which temperature and pressure are controlled, Another object of the present invention is to provide a method for producing a welded structure that is excellent in processing flexibility, has no weld cracking, and has excellent mechanical properties.

In order to solve the above problems, the laser welding apparatus and the method for manufacturing a welded structure according to the present invention employ the following means.
That is, a laser welding apparatus according to the present invention includes a laser light transmitting member that transmits laser light, and is disposed outside a sealed container that can accommodate an object to be welded, via the laser light transmitting member. And a laser beam emitting unit capable of irradiating the welding object accommodated in the sealed container from the outside of the sealed container.
With this apparatus, it is possible to perform fusion welding while observing the welding object in an inert atmosphere in which the temperature and pressure are controlled.

You may provide the heating apparatus which heats the said welding target object in the said laser welding apparatus.
By providing a heating device, even if the welding object is an intermetallic compound material such as TiAl having low ductility at room temperature, welding can be performed by increasing the ductility by heating, thus preventing weld cracking. it can.

The laser welding apparatus preferably includes a vacuum exhaust device that communicates with the inside of the sealed container and evacuates the inside of the sealed container.
The vacuum evacuation apparatus can remove the atmosphere in the sealed container and prevent the metal element in the welding target from reacting with oxygen or nitrogen in the atmosphere to form brittle oxides or nitrides.

The laser welding apparatus may include an inert gas supply device that communicates with the inside of the sealed container and supplies an inert gas into the sealed container.
By this inert gas supply device, an inert gas that does not react with the welding object can be supplied into the sealed container, and the pressure in the sealed container can be adjusted in accordance with the properties of the welding object.

Furthermore, the laser welding apparatus may include a pressurizing device that communicates with the inside of the sealed container and pressurizes the inside of the sealed container.
By pressurizing the sealed container with this pressurizing device, it is possible to prevent the metal element from being vaporized during welding even when the metal to be welded contains a metal element having a high vapor pressure such as manganese or aluminum. .

The laser beam emitting unit can be a YAG laser emitting unit.
By using a YAG laser beam, processing flexibility can be provided, and quality assurance is relatively easy.

As a material for the laser beam transmitting member, quartz glass is preferable.
By using quartz glass as the material for the laser beam transmitting member, the energy loss of the laser beam can be kept low.

The method for manufacturing a welded structure according to the present invention includes a step of accommodating a welding object in a sealed container provided with a laser light transmitting member that transmits laser light, and an outside of the sealed container via the laser light transmitting member. To welding by irradiating the welding object with laser light.
By this method, since fusion welding can be performed while the temperature and pressure in the sealed container are controlled, a welded structure having no weld cracking and excellent mechanical properties can be produced. Further, if the welding object is observed, welding can be surely performed.

In the method for manufacturing a welded structure, the welding object may be heated to perform welding.
When the welding object is an intermetallic compound having low ductility at room temperature such as TiAl, the ductility is increased by heating the welding object, so that the solidification shrinkage stress can be followed. Therefore, weld cracking can be prevented.

In the method for manufacturing a welded structure, a step of evacuating the sealed container may be provided.
By evacuating the sealed container, the atmosphere in the sealed container is removed, so that the metal elements in the welding object react with oxygen and nitrogen in the atmosphere to form brittle oxides and nitrides. Can be prevented. Therefore, it is possible to manufacture a welded structure excellent in mechanical characteristics of the joint.

In the method for manufacturing the welded structure, a step of filling the sealed container with an inert gas may be provided.
By filling the sealed container with an inert gas, an inert gas that does not react with the welding object is supplied into the sealed container, and the pressure in the sealed container is adjusted in accordance with the properties of the welding object.

In the method for manufacturing the welded structure, a step of pressurizing the inside of the sealed container may be provided.
By pressurizing the inside of the sealed container, even when a metal object having a high vapor pressure such as manganese or aluminum is contained in the welding object, the metal element can be prevented from being vaporized during welding.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to perform the fusion welding excellent in the flexibility on a process, observing a welding target object in the inert atmosphere where temperature and pressure were controlled. Further, a welded structure having no weld cracking and excellent mechanical properties can be obtained.

  Embodiments according to a laser welding apparatus and a welded structure manufacturing method of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of the laser welding apparatus of the present embodiment.
This laser welding apparatus has a sealed container 1 for accommodating an object to be welded. The sealed container 1 is a substantially columnar chamber, and includes a cylindrical body portion 2 whose bottom portion is closed and whose upper portion is opened, and a lid portion 3 that closes the upper opening of the body portion 2. The opening of the upper part of the body part 2 has a flange shape at the edge, and the lid part 3 is attached by bolts so that it can be opened and closed.

  A window-shaped laser light transmitting member 4 is provided on the side of the body 2. Laser light is irradiated from the outside of the sealed container toward the internal welding object via the laser light transmitting member 4. As a material of the laser beam transmitting member 4, a material that can withstand an environment such as temperature and pressure during welding and that does not absorb the energy of the laser beam is used. From these conditions, quartz glass can be suitably used as the material of the laser light transmitting member 4.

Inside the sealed container 1, a heating device 10 for heating the welding object is provided. The heating device 10 can be composed of a heater, a heater block, and the like. Intermetallic compound materials such as TiAl forged materials have low ductility at room temperature, but exhibit ductility of about 20 to 100% at 600 ° C. or higher. Therefore, when welding an intermetallic compound material, it is possible to follow the solidification shrinkage stress by heating the object to be welded with the heating device 10 and adjusting the groove temperature, thereby preventing weld cracking. Can do.
However, when welding a material having sufficient ductility, the heating device 10 may not be provided.

A laser head (laser light emitting portion) 15 is disposed outside the sealed container 1 at a position where a laser beam can be applied to the welding object accommodated inside the sealed container 1 via the laser light transmitting member 4. Yes. The laser head 15 is optically connected to a laser light source (not shown) by an optical fiber (not shown).
As the laser light source, YAG laser light that can have processing flexibility and is relatively easy to assure quality is preferable.

  Further, a vacuum pump (vacuum exhaust device) 25 communicating with the inside of the sealed container is provided outside the sealed container 1. By removing the atmosphere in the sealed container 1 with the vacuum pump 25, it is possible to prevent the metal element in the welding object from reacting with oxygen and nitrogen in the atmosphere to form brittle oxides and nitrides. .

  In addition, an inert gas cylinder (inert gas supply device) 20 communicating with the inside of the sealed container is provided outside the sealed container 1. By supplying an inert gas into the sealed container 1 with the inert gas cylinder 20, welding can be performed at medium and low pressures according to the properties of the object to be welded. Argon can be suitably used as the inert gas in the inert gas cylinder.

  Further, a pressurizing device (not shown) communicating with the inside of the sealed container may be provided outside the sealed container 1. When the welding object contains an element having a high vapor pressure such as manganese or aluminum, the element having a high vapor pressure is vaporized by performing the welding while the sealed container 1 is pressurized with a pressurizing device. Can be prevented.

  In order to manufacture a welded structure using the laser welding apparatus of the present embodiment, first, the welding object is arranged so as to be in contact with or close to the heating device 10 with the lid 3 opened. Next, the inside of the sealed container 1 is sealed by closing the upper opening of the body 2 with the lid 3. Next, the atmosphere inside the sealed container 1 is removed by the vacuum pump 25, and the pressure inside the sealed container 1 is appropriately adjusted by the inert gas cylinder 20 and a pressurizing device (not shown). The welding object is heated by the heating device 10 as necessary to adjust the groove temperature. Then, laser light is emitted from the laser head 15, and welding is performed by irradiating the object to be welded through the laser light transmitting member 4 to manufacture a welded structure.

  The welding apparatus and welded structure manufacturing method of the present invention are suitably employed for welding intermetallic compound materials, steel materials having a relatively large amount of carbon, etc. that require control of the atmosphere and temperature during welding. . Especially, it is employ | adopted especially suitably for welding of the TiAl forging material comprised from an active element. However, application of the welding apparatus and welded structure manufacturing method of the present invention is not limited to intermetallic compound materials and steel materials, and is also applied to other metal materials that are usually joined by a welding method.

Hereinafter, the present invention will be described in more detail by way of examples.
(Example)
Test materials and test methods:
Two pieces of Ti-28.6Al-6.9Mn forged material (200 ^L × 50 ^W × 4 ^t mm) were butted and welded. The joint shape was an I type. Before installing the forging material in the chamber, the groove surface and the front and back surfaces near the groove were cleaned by wire brushing. Further, for constraining the groove portion, both ends on the groove line were tack-welded by GTAW (Gas Tungsten Arc Welding) using a pure Ti welding rod.

  The laser welding apparatus shown in FIG. 1 was used for the welding test. As a laser welding machine, a YAG laser welding machine (fiber type: SI type fiber, fiber diameter: 0.8 mm, optical system: Bf 200 mm) with a rated output of 10 kW was used. The sealed container 1 is provided with a heating device (heater and heater block) 10 for heating the specimen, and an inert gas cylinder 20 and a vacuum pump 25 are connected so as to control the atmosphere for evacuation and introduction of inert gas. . Laser light is irradiated from the outside of the sealed container 1 for ensuring an inert atmosphere to a specimen groove portion through quartz glass (laser light transmitting member) 4 having a double-sided single layer coating for YAG laser. Welded. The specimen was placed vertically. Welding construction can ensure a stable molten pool shape, high quality welding construction is possible, and unevenness such as underfill and undercut is unlikely to occur, so finishing work after welding such as grinding of the welded part can be reduced as much as possible It was assumed that the construction work was upward. The specimen was heated with a heater block that also served as a jig for restraining the specimen groove, and the temperature of the specimen was controlled with a thermocouple attached directly to the groove surface. Before penetration welding on the groove, the gap and mismatch amount are reduced as much as possible, and spot welding (3 points on the groove) and seal welding (partial penetration welding) are performed to restrain the position of the groove. It was. Spot welding, seal welding, and penetration welding (main welding) were performed while heating the specimen with a heater block.

The applied welding conditions are summarized in Table 1. For basic welding conditions that directly affect the weld dimensions such as spot diameter, machining point output, and welding speed, optimum welding conditions that allow groove welding are set in advance, taking into account the specimen thickness of 4 mm. In addition, grasp how much the components with high vapor pressure of Mn and Al change between the material and the welded part, or the metallurgical and mechanical property change of the joint part where the component has changed. Therefore, the joint was formed by changing the welding atmosphere to high vacuum (10 ⁻³ Torr) and low vacuum (10 ⁻¹ Torr).

Test results and discussion:
(YAG laser welding test)
In the welded specimen, the lid 3 on the upper surface of the sealed container 1 is opened with a crane, and is inserted between the heater blocks in the sealed container 1 to be restrained. A standing posture was adopted as the welding posture, and the reflected light from the groove surface was tilted by 15 ° in the welding progress direction so as not to reach the condensing lens in the laser head 15 and the optical fiber ahead of the condensing lens. Therefore, when the welding head is moved upward, welding is performed at a backward angle with respect to the weld specimen. At the time of downward welding and vertical horizontal welding construction, it is common to employ welding construction at the advance angle in order to preheat the groove and stabilize the molten pool, but in the case of vertical upward welding, When welding at advancing angle is adopted, especially in welding methods that show keyhole-type melting, such as electron beam welding or laser welding, once molten metal sags under the influence of gravity, it is melted again. In this test, the metal is exposed to the irradiation beam and makes the behavior of the molten pool unstable, which can easily cause the gas generated from the evaporated metal and the material to get into the molten pool and cause internal defects such as porosity. Adopting reverse welding.

  Due to the appearance of the welded specimens laser welded in high and low vacuum atmospheres (as welded), the bead surface properties of the welded specimens welded in both atmospheres are almost free of dents due to undercut and underfill, etc. -Almost no discoloration due to nitriding was observed, and the metal was white. As a result of the penetrant inspection, no dot-like or linear indications suggesting the presence of surface porosity or weld cracks were found. In addition, as a result of the radiographic inspection, no internal defects such as porosity and foreign material entrainment were found in the welds of all the weld specimens welded in both atmospheres. The weld internal quality requirements specified in the welding specification AWS D17.1 (formerly AMS-STD-2219) applied in this way were satisfied.

(Component analysis test)
Table 2 shows the component analysis results of the specimen welds laser welded in the forging, high vacuum atmosphere and low vacuum atmosphere. In both welds welded in a high-vacuum atmosphere and a low-vacuum atmosphere, the amount of Al and Mn was reduced by about 1 wt% compared to those of the forged material, but there was no significant difference in constituent components between them. . The gas component amounts of C, N, and H were also almost equal and within the material standard value between the welded part and the forged material and between the high vacuum atmosphere and the low vacuum atmosphere. In both materials, the O content was slightly higher than the standard value. From the results of this test, it became clear that the constituent components of the specimen welded portion laser-welded in a high-vacuum atmosphere and a low-vacuum atmosphere did not change significantly compared to that of the forged material.

It is a schematic block diagram of the laser welding apparatus of embodiment of this invention.

Explanation of symbols

1 Sealed container 2 Body 3 Lid 4 Quartz glass (laser light transmitting member)
10 Heating device 15 Laser head (laser beam emitting part)
20 Inert gas cylinder (inert gas supply device)
25 Vacuum pump (evacuation device)

Claims (12)

A sealed container that includes a laser light transmitting member that transmits laser light and can accommodate a welding object;
A laser light emitting portion disposed outside the sealed container and capable of irradiating the welding object accommodated in the sealed container from the outside of the sealed container via the laser light transmitting member; Laser welding equipment.   The laser welding apparatus of Claim 1 provided with the heating apparatus which heats the said welding target object.   The laser welding apparatus according to claim 1, further comprising an evacuation device that communicates with the inside of the sealed container and evacuates the inside of the sealed container.   The laser welding apparatus according to any one of claims 1 to 3, further comprising an inert gas supply device that communicates with the inside of the sealed container and supplies an inert gas to the inside of the sealed container.   The laser welding apparatus according to any one of claims 1 to 4, further comprising a pressurizing device that communicates with the inside of the sealed container and pressurizes the inside of the sealed container.   The laser welding apparatus according to any one of claims 1 to 5, wherein the laser beam emitting unit is a YAG laser emitting unit.   The laser welding apparatus according to claim 1, wherein the laser light transmitting member is made of quartz glass. Storing the welding object in a sealed container provided with a laser beam transmitting member that transmits the laser beam;
And a step of performing welding by irradiating the welding object with laser light from the outside of the sealed container through the laser light transmitting member.   The method for manufacturing a welded structure according to claim 8, comprising a step of heating the welding object.   The method for manufacturing a welded structure according to claim 8, comprising a step of evacuating the inside of the sealed container.   The method for manufacturing a welded structure according to any one of claims 8 to 10, further comprising a step of filling the sealed container with an inert gas.   The method for manufacturing a welded structure according to any one of claims 8 to 11, further comprising a step of pressurizing the inside of the sealed container.

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