JPH01197086A - Method for welding inside magnetic field - Google Patents

Abstract

PURPOSE:To easily perform a normal welding without receiving any magnetic effect even in a strong magnetic field by executing welding by projecting a laser beam on the zone to be welded located inside a magnetic field. CONSTITUTION:An ultra-high temp. can be generated by concentrating an optical energy in an extremely small area by stopping a laser beam by a converging implement and yet even in the strong magnetic field of >=500 gauss it is the light receiving no magnetic action at all. The welding can therefore be easily performed by projecting a laser beam to the zone to be welded located inside magnetic field. The oscillation source of the laser beam is not specially limited but a CO2 laser is optimum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to the assembly and manufacture of various equipment and equipment using permanent magnets, such as magnetic coupling type pumps, in which the constituent members are placed near the magnets. This invention relates to a welding method in a magnetic field, such as when welding in a magnetic field.

(Prior art and its problems) Generally, electric welding methods such as arc welding are widely used for welding metal materials, but when the part to be welded is in a strong magnetic field, the weld metal Normal welding is impossible by normal means because a phenomenon called magnetic blowing occurs in which (?8 contact rod material) is scattered. Particularly, when components of equipment that use permanent magnets are welded in the vicinity of the magnets, there is the disadvantage that the magnets are demagnetized due to the welding heat input as well as the above magnetic blowing phenomenon.

Therefore, in the past, it was necessary to set the welding position away from the permanent magnet to reduce the influence of the magnetic field.
This requires an extra area structurally, which imposes major restrictions on the design of equipment, which poses a problem especially when downsizing, and also causes problems such as large waste of materials and high costs. there were.

Although pulse-driven electric welding machines can alleviate the magnetic blowing phenomenon and demagnetization to some extent, it is not sufficient.
For example, if the part to be welded is in a strong magnetic field of 500 Gauss or more, welding becomes difficult even for highly skilled workers.

(Means for Solving the Problems) The present invention was made to solve the above-mentioned conventional problems, and it is possible to easily perform normal welding without being affected by magnetic fields, no matter how strong the magnetic field is. The purpose is to provide a way to do so.

That is, in order to achieve the above object, the magnetic field welding method of the present invention is characterized by welding by irradiating a laser beam onto a part to be welded which is within a magnetic field.

(Function) As is well known, the laser beam used in the method of the present invention is a coherent light beam with a uniform phase due to laser oscillation.
By concentrating light energy in an extremely small area by narrowing it down with a focusing device such as an optical lens or concave mirror, it is possible to generate extremely high temperatures.When used for welding, it is possible to Even in a strong magnetic field of 500 gauss or more, where magnetic blowing phenomenon is unavoidable, normal welding can be easily performed because the light is completely unaffected by magnetic effects. In addition, since the area that becomes high temperature is minute, the overall welding heat input is 1.15~
Since it is about 1/10 the size, it has the advantage that demagnetization is less likely to occur even if welding is performed near a permanent magnet, and changes in the structure of the welded part are suppressed, resulting in less deterioration of material properties. Furthermore, when welding with a laser beam, there is less oxidation on the surface of the welded part, resulting in a better appearance and less internal distortion.
, and high welding accuracy can be obtained.

Laser beams have already been used for cutting, drilling, microfabrication, etc. of high-melting point materials such as metals and ceramics by taking advantage of their properties, and their use for welding has also been reported, although most are still in the experimental stage. ing. However, application to magnetic field welding like the present invention is not known. On the other hand, electron beams, which are typical of other energy beams, can be treated in the same way as laser beams, but cannot be used for welding in a magnetic field because they are subject to magnetic action.

(Detailed Structure of the Invention) The oscillation source of the laser beam used in the present invention is not particularly limited, and various sources such as gas lasers, solid-state lasers, and semiconductor lasers can be used, but carbon dioxide lasers are particularly preferred.

Although the laser output varies depending on the oscillation source and the type of object to be welded, it is generally about 0.5 to 2 KW when welding ordinary metal materials using a carbon dioxide laser.

The focal position of the laser beam is determined according to the welding depth, bead stability, bead width, etc., but numerically it is better to set it slightly inside the workpiece rather than on the surface to obtain better results. . However, if the focal point is too deep, the reflection will be large, causing damage to lenses and other equipment, or reducing the welding rate. Preferably around 1 crane.

Further, as the optical lens used for converging the laser beam, one having a focal length of usually 250 mm or less and a relatively long one is preferable. In other words, as the focal length becomes longer, the aperture angle of the beam becomes smaller and the influence of reflection is alleviated. The usable area for welding is widened, and the vertical positioning of the welded object is made easier. In addition, deep welding can be performed with a narrow bead width, making it particularly suitable for welding corrosion-resistant steels such as stainless steel and Hastelloy alloy.

There is no restriction on the magnetic field strength of the part to be welded, and as mentioned above, welding can be performed without any problem even in a strong magnetic field of 500 Gauss or more, where magnetic blowing phenomenon is unavoidable in conventional electric welding methods. In addition, the members to be welded together are generally made of various metal materials, including magnetic metals such as iron and its alloys. Welding is also possible.

Note that in order to reliably prevent oxidative discoloration during welding, it is recommended that the laser beam irradiation position be placed in an inert gas atmosphere. As a concrete means, for example, Fig. 1A,
As shown in B, there is a method in which skirt-shaped gas caps 2a and 2b are integrally attached to the laser gun 1, and an inert gas such as a rare gas or nitrogen is spouted into the inside from a gas nozzle 3.

However, the gas camp 2a in Figure 1 is the laser gun 1.
It has a generally elliptical shape when viewed from the bottom, widening on the rear side in the direction of travel, and is usually made of transparent plastic or the like, and is set so as to form a slight gap with the surface of the workpiece 4 to be welded. In other words, when the laser output increases, the metal vapor generated from the beam irradiation part turns into a plasma state and absorbs the laser beam, but in the configuration shown in FIG. Since it is caught up and discharged to the outside through the gap, the reduction in welding efficiency due to the above-mentioned absorption is avoided. In addition, when welding a large number of objects of the same shape, and when the welding speed can be increased to such an extent that the generation of metal vapor can be ignored, welding to the workpiece 4 as shown in Figure 1B will completely eliminate the gas. A gas cap 2b made of rubber or the like that can provide shielding may be used.

On the other hand, when canning (enclosure) welding is performed by fitting a thin cylindrical cover 7 onto a ring-shaped base material 6 in which permanent magnets 5 are embedded at key points on the outer periphery as shown in FIG. If welding is performed by irradiating the laser beam 1a converged by the lens 1b from the radial direction as shown in the figure, sufficient welding is possible even if there is some gap between the base material 6 and the cover 7. On the other hand, when the beam 1a is irradiated parallel to the axial direction as shown in FIG. 7
Welding becomes difficult because the material is thermally deformed and tends to open outward.

It goes without saying that the method of the present invention is not limited to the exemplified embodiments, but can be similarly applied to various forms of welding metal materials within a magnetic field.

(Example) Using the welding configuration shown in FIG. 3A, canning welding between the base metal 6 and the cover 7 is performed using the laser output, welding speed, focal length of the converging lens, and focal position from the welding surface as shown in the table below. The external appearance and penetration conditions of the bead were tested by changing various conditions such as depth of the bead. In addition, other conditions are as follows.

Laser oscillation source... Carbon dioxide laser base material... 5LIS316 M, outer diameter 110 m Cover... Made of 5TLS316, wall thickness approx. 21 mm Permanent magnet...
Sanatorium made of cobalt, magnetic field strength: 11,000 gauss Maximum magnetic field strength of the welded part...11,000 gauss Distance from the welded part to the magnet...minimum 1 The evaluation in the Tsuru table is based on the smoothness of the bead regarding the external appearance of the bead. From the bead width,
Regarding the weld penetration condition, the bead width and weld penetration depth are determined by
Each is shown in the following three stages.

O...Good, Δ...Good, ×...Not good (effects unique to the invention) According to the method of the present invention, welding in a magnetic field where magnetic blowing phenomenon was unavoidable in conventional electric welding methods. Since this is done by laser beam irradiation, the above phenomenon does not occur at all, and there is no demagnetization due to heat input to the permanent magnet, making it possible to easily and normally perform high-precision welding. The effect is that compositional changes, surface oxidation, internal distortions, etc. are also extremely reduced.

[Brief explanation of the drawing]

1A and 1B are schematic side views showing an example of a welding form according to the method of the present invention, FIG. 2 is an axial sectional view showing an example of a welded product, and FIG. 3A is a preferred welding of the welded product of FIG. 2. It is a radial cross-sectional view without showing means. 1... Laser gun, Ia... Laser beam, 2a,
2b...Gas cap, 4...F6 contact object, 5.
... Permanent magnet, 6... Base metal (workpiece), 7... Metal cover (workpiece).

Claims (1)

[Claims] 1. A welding method in a magnetic field, characterized in that a part to be welded in a magnetic field is irradiated with a laser beam to weld. 2. The magnetic field welding method according to claim 1, wherein a part of the members to be welded together are made of magnetic metal. 3. The magnetic field welding method according to claim 1 or 2, wherein the magnetic field is generated from a permanent magnet placed in advance in the vicinity of the part to be welded. 4. The method of welding in a magnetic field according to any one of claims 1 to 3, wherein at least a part of the welded part is within a magnetic field of 500 Gauss or more. 5. The magnetic field welding method according to any one of claims 1 to 4, wherein the laser beam irradiation position is in an inert gas atmosphere. 6. The magnetic field welding method according to claim 5, wherein the inert gas is introduced into a gas cap attached to the laser gun and covering the part to be welded.