JPS62107885A - Magnetic agitation welding method - Google Patents

Abstract

PURPOSE:To prevent a high temp. crack and to improve the shape of a bead, etc. by arranging the stator of an alternating current linear motor just the above or the below of a molten pool in the laser beam welding that a welding current is not passed to the base metal. CONSTITUTION:The stator 21 of a cylindrical three phase AC linear motor is arranged at the position just the above or the below of a molten pool 2 in the laser beam welding, etc. which forms the molten pool 2 and melting metal 3 via a laser beam 30 on a base metal 1. The stator 21 is of annular shape, providing a radial projecting part on the lower face and is composed of the core which forms a notch part on one place thereof and a coil 25. A magnetic flux density is formed with the passing of a three phase alternating current to the stator 21, the waveform thereof forms a progressive magnetic field and the molten pool 2 is subjected to a magnetic agitation by the mutual action with the eddy current to be generated in the base metal. In this way, the prevention from high temp. cracks, the improvement of the bead shape and the structural improvement of the welding metal can be performed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a magnetic stir welding method, and more specifically, it is used for welding precision parts in iron and steel machinery, wind machinery, etc., as well as chemical machinery, nuclear power, ships, and iron bridges. This relates to a magnetic stirring welding method suitable for welding all kinds of welded structures such as.

[Conventional technology]

Stirring of the molten pool is a method for improving the structure of weld metal and preventing poor fusion, hot cracking, etc. As a method for stirring such a molten pool, a magnetic method has conventionally been put into practical use. This will be explained with reference to the principle diagram of FIG. 10, which is applied to TIG welding. In the figure, 1 is the base material, 2 is the molten pool, 3 is the weld metal, 4 is the tungsten electrode, 5 is the TIG welding torch, 6 is the excitation coil, 7 is the alternating magnetic field generator, 8
is a shield nozzle. First, the welding current 9 flowing from the tungsten electrode 4 to the molten pool 2 of the base material 1 flows radially around the molten pool 2 and approximately parallel to the surface of the base material 1 within the base material. In this state, when a magnetic field 10 perpendicular to the surface of the base metal 1 is applied from an excitation coil 6 placed around the welding torch 5, a Lorentz force F is generated by the welding current 9 flowing throughout the molten pool 2, causing the melt to melt. Metal rotates in one direction. Since the excitation coil 6 is connected to an alternating magnetic field generating power source 7, it can apply a periodic reversing force to the molten pool 2, and the molten pool 2 can be effectively stirred.

[Problem that the invention seeks to solve]

However, in the case of laser welding and non-transfer plasma welding, unlike TIG welding, MIG welding, and submerged arc welding, welding current does not flow through the molten pool or base metal, so magnetic stirring was not possible with conventional methods. .

The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic stirring welding method that can effectively magnetically stir a molten pool of a base material in laser welding or plasma welding.

[Means for solving problems]

The present invention provides a welding method in which a molten pool is formed in a base material by welding such as plasma welding or laser welding that does not flow a welding current into the base material, and in which an alternating current is applied to the back surface of the base material directly above or below the molten pool. This method is characterized in that a stator of a rust induction linear motor is arranged to generate an induced current in the base material and the molten pool, thereby rotating and stirring the molten pool.

The welding method of the present invention will be explained below with reference to FIGS. 1 to 3.

In the figure, 1 is the base material, 2 is the molten pool, and 3 is the weld metal. Directly above the molten pool 2, a stator 2 of a cylindrical three-phase AC IJ near motor is arranged. This stator 2 has a ring shape, has a plurality of radial protrusions 22 on its lower surface, and has a core 24 made of a ferromagnetic material with a notch 23 formed in one place of the protrusions 22. The coil 25 is arranged between the protrusions. The stator 2 is connected to a three-phase AC power source 26. A switching circuit 27 for periodically changing the polarity is interposed between the three-phase AC power supply 26 and the stator 2. Also.

A laser welding machine 29 having a lens 28 is disposed above the stator 21, and a laser beam 30 from this welding machine 29 is irradiated onto the base material 1 through the hollow part of the stator 2, forming a molten pool. form 2.

[Effect]

When three-phase alternating current is applied to the stator 21' as shown in Fig. 4,
A magnetic flux density B is generated. The waveform of this magnetic flux density B is when time is stopped, and the waveform moves to the right as time passes.

This is a traveling magnetic field, which is basically the same as a rotating magnetic field in a rotating induction machine.

Since the magnetic flux generated from the stator 27' is alternating current, eddy current is applied to the base material l according to Lenz's law. occurs. The e mark and the x mark shown on the base material 1 in FIG. 4 indicate the direction and magnitude of eddy current flow.・The mark and the X mark are perpendicular to the paper surface, respectively.
The directions are opposite to each other.

This eddy electrician. According to Fleming's left-hand rule, a thrust force F is generated continuously from the magnetic flux density BK and the magnetic flux density BK.

The stator 21' mentioned above is made into a cylindrical stator 2 as shown in FIGS. , and rotational force is applied to the molten pool 2. Therefore, even if a laser welder 29, for example, which does not flow welding current to the molten pool 2, etc., is used, the molten pool 2f can be effectively stirred.

[Embodiments of the invention]

The present invention will be explained in detail below.

Example 1 First, as shown in Fig. 6, 250 x 100 x 30
20 on top of 3 restraining plates made of 5M50 material with dimensions lllll11
32 test pieces of 5M50 material with dimensions of 0 x 60 x 20 gourds
After installing the test piece 32, the periphery of the test piece 32 and the restraint plate 3 were welded and restrained by a restraint bead 33. Next, the center of the test piece 32 was melt-run welded using the apparatus shown in FIGS. 1 to 3 described above under the conditions shown in Table 1 below (no filler metal was used, just a bead was run). A test bead 34 was formed.

Therefore, regarding the test bead 34 after laser welding,
Defects (occurrence of blowholes) and cracking rates were investigated by line inspection. Regarding the cracking rate, the cross sections at five locations were
Investigate the crack as shown in Figure 8 and use the following formula t (crack length) / L (penetration depth) x 100 (%))
Calculated. These results are also listed in Table 1. In addition,
In Table 1, the blowhole and cracking rates obtained by laser welding without magnetic stirring are shown as Comparative Example 1.

As is clear from Table 1 above, it can be seen that the magnetic stirring welding of Example 1 can prevent the occurrence of blowholes and cracks.

Example 2 A mild steel plate 35 on which the stellite powder (not shown) shown in FIG. 9 was sprinkled to a thickness of 2 cm was laser-cut using the apparatus shown in FIGS. 1 to 3 described above under the conditions shown in Table 2 below. Overlay welding was performed to form an overlay weld bead 36.

In the above-mentioned overlay welding, from the viewpoint of material cost and work efficiency, it is desirable to form an overlay weld bead as thin and wide as possible, so a smaller H (bead height)/W (bead width) is better. You can say that. Furthermore, from the viewpoint of suppressing the occurrence of defects at the bead overlapped portion, it is desirable that the angle (θ) of the overlay weld bead toe be large. Therefore, regarding the overlay weld bead 36 formed in Example 2,
and θ were investigated. The results are also listed in Table 2. In addition,
In Table 2, the radius and θ of an overlay weld bead formed by laser welding without magnetic stirring are also listed as Comparative Example 2.

As is clear from Table 2 above, it can be seen that according to Example 2, the overlay weld bead shape can be improved.

In the above embodiment, a magnetic stirring welding method employing laser welding has been described, but the same effects can be achieved even by employing welding such as plasma welding in which no welding current is passed through the base material.

〔Effect of the invention〕

As detailed above, according to the present invention, in laser welding or plasma welding, it is possible to fully magnetically stir the molten pool of the base metal, and as a result, it is possible to prevent hot cracking, improve the bead shape, and improve the structure of the weld metal. A magnetic stir welding method can be provided.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus used for magnetic stirring welding of the present invention, FIG. 2 is a sectional view taken along line A-A' in FIG. 1, and FIG.
The figure is a sectional view taken along the line B-B' in Figure 1, Figure 4 is an explanatory diagram showing the principle of magnetic (W stirring) of the present invention, Figure 5 is an explanatory diagram showing the state of magnetic stirring of the molten pool, Figure 6 shows Example 1 of the present invention.
A plan view showing the test scissors piece used in Figure 7 is c- in Figure 6.
8 is an enlarged sectional view of section D in FIG. 7, FIG. 9 is a schematic diagram showing a mild steel plate on which a υ overlay weld bead is formed according to Example 2, and FIG. The figure is an explanatory diagram showing TIG welding using conventional magnetic stirring. No... Base metal, 2... Molten pool, 3... Weld metal, 2
1... Stator of AC induction linear motor, 24... Core, 2.5... Coil, 26... Three-phase AC power supply, 28
... Lens, 29... Laser welding machine, 30... Laser light, 3... Restriction plate, 32... Test piece, 34...
...Test bead, 35... Mild steel plate, 36... Overlay welding bead. Applicant Sub-Agent Patent Attorney Takehiko Suzue Figure 2
32 Figure 4 Figure 5 Figure 6 Figure 7 Figure 1 Figure 8

Claims (1)

[Claims] In a welding method in which a molten pool is formed in the base material by welding such as plasma welding or laser welding in which no welding current is applied to the base material, a stator of an AC induction linear motor is placed on the back surface of the base material directly above or below the molten pool. A magnetic stirring welding method characterized in that the molten pool is rotated and stirred by arranging the molten metal and the molten pool to generate an induced current in the base metal and the molten pool.