JPS60240394A - Laser welding method - Google Patents

Abstract

PURPOSE:To improve the quality of a weld zone by condensing and irradiating a laser beam to a base metal via a static magnetic field formed in approximately parallel with the surface of the base metal. CONSTITUTION:A notch 71 for insertion of a laser beam is provided to a magnetic core 7 and DC current is conducted to a coil wound on the core 7 to form the static magnetic field H in parallel with a weld line 9. The evaporated metallic atoms or molecule of the base metal are made into positive ions at the irradiating point O of the laser and are released in an X-axis direction but the orbit thereof is bent in the direction of the curve I. The orbit of the charge particles is similarly bent approximately orthogonal with the line 9. All the charge particles toward the incident direction of the laser beam are therefore bent in the orbit toward the outside of the beam condensing part, by which the particles forming the plasma are surely removed. The quality of the weld zone is improved by the above-mentioned method.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser welding method suitable for welding, for example, heat exchangers, etc., which requires deep insertion.

Generally, in this type of laser welding method, as shown in FIG. 1, a laser beam 1 supplied from a laser source (not shown) is applied to a base metal 4 using a condensing lens 3 protected with an inert gas 2.
This is done by irradiating the area with focused light.

By the way, when the laser beam 1 in the above laser welding method is focused and irradiated onto the base metal 4, the irradiated portion of the base metal 4 is melted and evaporated to generate gold-gold vapor. This metal vapor has the problem that it is ionized by thermal energy and also ionized by absorbing the energy of the laser beam 1, forming plasma 5 near the surface of the base metal 4. That is, as shown in FIG. 2, this plasma 5 absorbs the energy of the laser beam 1 and forms the base metal 4.
In order to reduce the energy reaching the surface of the weld, the penetration depth 6 of the weld is reduced and fluctuates, which is a factor that deteriorates the quality of the weld.

For this reason, conventionally, in order to prevent the generation of the plasma 5, there is a method in which the inert gas 2 is directly blown onto the welded part of the base metal 4 to blow away the metal vapor. It is taken.

However, the method of preventing the generation of plasma 5 using the inert gas 2 as described above has various disadvantages.

The first problem is that plasma 5 cannot be reliably prevented.

The second point is that thermionic electrons released from the high-temperature metal surface and electrons generated by the ionization of metal vapor collide with inert gas molecules blown from the atmosphere at high pressure, ionizing them and creating new The problem is to form plasma 5.

(In other words, since the inert gas 2 has a higher pressure than the atmosphere,
This is because the molecular density is high and the collision cross section is large, so there is a high probability that electrons and molecules will collide. The problem is that there are differences in welding results.

The fourth problem is that since plasma 5 is generated intermittently, there is a possibility that the penetration depth 6 may vary.

This invention was made in view of the above circumstances, and in the Rade welding method in which welding is performed by concentrating a laser beam on a base metal, a static magnetic field approximately parallel to the surface of the base metal is applied to the base metal by concentrating the Rade beam. The laser beam is formed in a corresponding manner to the base metal, and the base metal is irradiated with the laser beam through the static magnetic field to perform welding, thereby reliably preventing a decrease in the energy of the laser beam. It is an object of the present invention to provide a laser welding method that can efficiently and reliably remove plasma from a Zapem condensed light irradiation part and contribute to improving the quality of a welded part.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, here, the same parts as in FIGS. 1 and 2 described above are given the same reference numerals, and the explanation thereof will be omitted.

In FIG. 3, reference numeral 7 denotes a magnetic core provided at the laser beam condensing irradiation section on the surface of the base metal 4. A cutout (gap) 71 for laser beam insertion is provided in a part of the magnetic core 7, and a coil 8 connected to a power source E is wound around the outer circumference of the cutout (gap) 71. When the DC current I is supplied to the coil 8 of the magnetic core 7, the magnetic core 7 functions to form, for example, a static magnetic field substantially parallel to the base metal 4 and the welding line 9.

That is, as shown in FIG. 4, when DC current I is supplied to the coil 8 of the magnetic core 2, the laser irradiation point 0 is first
A uniform magnetic field H approximately parallel to the weld line 9 is formed in the vicinity. Here, at the laser irradiation point 0, the metal atoms, children, or molecules of the base metal 4 vaporized by the focused laser beam irradiation are positively ionized due to thermal ionization, etc., and are
It is emitted in the axial direction (the direction of Radhe beam incidence). At this time, the ions are subjected to a force F in the y-axis direction, which is approximately perpendicular to the welding line and the X-axis direction, due to Fleming's left-hand modus.
As shown by the curve (■), the trajectory of the electron is bent, and the trajectory of the electron generated by the ionization of the metal molecules or atoms of the base metal 4, and the trajectory of the hot electron emitted from the surface of the high temperature base metal 4 in the laser beam incident direction. It is bent in the −y-axis direction, which is the opposite direction to positive ions (not shown).

On the other hand, the charged particles in the plasma 5 diffuse at a very high speed in the laser beam incident direction due to their rapid thermal expansion, and arrive at the welding line 9 in almost the same way as the charged particles emitted from the surface of the base metal 4. The trajectory is bent in a direction substantially perpendicular to the other direction.

As a result, the trajectory of all the charged particles heading in the direction of laser beam incidence is bent to the outside of the Lede beam condensing irradiation section, and it is ensured that the particles forming the plasma 5 are efficiently transferred from the laser beam condensing irradiation section to the L. This results in a good quality weld with uniform penetration depth.

Here, when a monovalent positive ion is radiated in the X-axis direction with an initial velocity v6, the metal atom or molecule will not shift in the y-axis direction, assuming that the velocity is hardly attenuated for a certain period of time. expressed. However, e is the amount of monovalent charge, B is the magnetic flux density, m is the mass of the ion, and t is the time.

On the other hand, the initial velocity 16 of the ions is determined by the surface temperature T of the base metal 40, and is given by the following equation f, where K is the Delraman constant. Therefore, for example, in the case of Fe atoms, according to the above equations (1) and (2), while the Fe ion moves in the X-axis direction, 0.2WrM (
Calculate the magnetic flux density B required to move the C02 laser beam (corresponding to the spot diameter at the focal position of the laser beam) and the current value required to generate the magnetic flux density B.

For example, in welding using a 3 kW CO2 laser beam IK, the power density of the laser focused irradiation part is approximately 10'W/cm.
2. Therefore, the surface temperature T of the base metal 4 is considered to have reached the boiling point, which is 2750° C. for Fe. Therefore, according to the above equation (2), the initial velocity V6 is 71)x103mls, and the time required to move in the X-axis direction is t==1xios.

During this time, the magnetic flux density B necessary for moving 0.2 square meters in the y-axis direction is determined by the above equation (1). The current value required to form this magnetic flux density B is the length of the magnetic core 7 = 1
50m.

Gap length t6 = 5 rm *Number of turns of coil 8 N
When = 100, it can be determined as follows. However, μ0 is the magnetic permeability in vacuum, μS is the relative magnetic permeability of the magnetic core 7, and the relative magnetic permeability μ6 of Fe is μ 1000
It is.

Further, the present invention is not limited to the above-mentioned embodiments, and substantially the same effect can be expected even if the direction of the silent magnetic field is not made substantially parallel to the welding line 9, and the desired magnetic flux density B can be generated using a permanent magnet. Almost the same effect can be expected.

As described in detail above, 1. According to the present invention, in the Rade welding method in which welding is performed by condensing a laser beam onto a base metal, a quiet magnetic field approximately parallel to the base metal surface is applied to the laser beam condensing irradiation section. By forming the laser beam corresponding to the static magnetic field and performing welding by concentrating the laser beam on the base metal through the static magnetic field, the focused laser beam is irradiated so as to reliably prevent a decrease in the energy of the laser beam. It is possible to provide a laser welding method that efficiently and reliably removes plasma in the weld zone and contributes to improving the quality of the weld zone.

[Brief explanation of the drawing]

1 and 2 are configuration explanatory diagrams and detailed views of essential parts shown to explain a conventional laser welding method, and FIG. 3 is a configuration explanatory diagram shown to explain an embodiment of the present invention. FIG. 4 is a state diagram shown to explain the main part of FIG. 3. 1... Laser beam, 2... Inert gas, 3...
Condensing lens, 4... Base metal, 5... Plasma, 6
... Melting depth, 7... Magnetic core, 8... Coil,
9...Welding line. Applicant Sub-Agent Patent Attorney Takehiko Suzue

Claims (1)

[Claims] In a laser welding method in which welding is performed by condensing a laser beam onto a base metal, a static magnetic field approximately parallel to the surface of the base metal is formed corresponding to the Renide beam condensing irradiation section, and the laser beam is directed to the base metal. A laser welding method characterized in that welding is performed by irradiating the base metal with focused light through a magnetic field.