JP2873418B2 - Laser beam welding method for strip-shaped metal materials having different thicknesses - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for laser beam welding of metal strips having different thicknesses. Butt laser welding method for obtaining a laser beam.

[0002]

2. Description of the Related Art For example, as in laser beam welding,
In the welding method using a high-density energy beam, a beam is penetrated from one side of a material to be welded, and a front bead and a back bead are formed on both sides. However, when butt-welding metal materials having different thicknesses by laser beam welding or the like, it is difficult to smooth the front bead and the back bead, and burn-through, misalignment, or Welding defects such as excessive excess are likely to occur.

In order to improve this, various methods have been proposed as follows.

First, as a first method, when a welding defect such as excessively large excess or misalignment occurs, as shown in Japanese Patent Application Laid-Open No. 57-75295, the welding defect is removed. A method of grinding and removing with a grindstone has been proposed.

As a second method for improving burn-through and misalignment, a backing device has been proposed as disclosed in Japanese Utility Model Publication No. 62-27347.

Further, as a third method, for welded joints having different plate thicknesses, as shown in Japanese Patent Publication No. 3-10089, the focal position of the laser beam is adjusted by shifting the focal point of the joint from the center of the groove of the joint. There has been proposed a method of moving in parallel to the thick side.

[0007]

However, in the first method, the shape of the front and back beads is improved by grinding the weld defect, but the grinding dust is scattered and the surface of the material to be welded is scratched. In addition, since the number of processing steps is increased by one, the loss of production time is large and productivity is impaired.

The second method can improve burn-through and misalignment on the back side, but it is difficult to improve a front bead of a welded portion having a different thickness.

In the third method, the shape of the front bead is adjusted well, but the heat input becomes excessive near the thick bead. For this reason, crystal grains are coarsened, and in particular, in a ferritic stainless steel that requires low heat input welding, a decrease in the strength of the weld heat affected zone (hereinafter, HAZ) is inevitable. On the other hand, near the back bead on the thick plate side, laser beam energy is consumed on the front surface side, so that there is a problem that insufficient penetration occurs in a thick plate range.

As described above, the conventional method is limited in the application method depending on the type of steel and the thickness of the steel, and is not sufficient for continuously producing multiple types of steel.

An object of the present invention is to solve the above problems, and specifically, a front bead and a back bead of a welded portion.
It is an object of the present invention to provide a laser beam welding method which has both improved shape of a metal and prevention of HAZ deterioration and insufficient penetration.

[0012]

That is, in the method of the present invention, opposing ends of strip-shaped metal materials having different plate thicknesses are butted to form a butt groove, and a laser beam is obliquely downwardly directed to the butt groove. And butt welding.

More specifically, opposing ends of strip-shaped metal materials having different plate thicknesses are joined to form a butt groove, and the butt groove is changed from a thick strip-shaped metal material to a thin strip-shaped metal material. And a laser beam is emitted obliquely downward toward the center, and the focal position is adjusted to the center of the butt groove.

[0014] Furthermore, the opposite ends of the band-shaped metal materials having different plate thicknesses are butted to form a butt groove, and a filler wire is supplied on the thin band-shaped metal material at the butt groove, and the butt groove is formed. Then, while irradiating the laser beam obliquely downward from the thin metal strip to the thick metal strip, align the center line between the center of the diameter of the filler wire and the corner of the opposite end face of the thick metal strip. It is characterized by matching on the connected line.

The configuration and operation of these means will now be described in more detail with reference to the drawings.

FIG. 1 is an explanatory view showing an example of a case where welded joints having different thicknesses are formed without using a filler wire according to the present invention, and FIG. 2 is an explanatory view showing the details in an enlarged manner. FIG. 3 is an explanatory view showing an example of a case where welded joints having different plate thicknesses are formed with a filler wire interposed therebetween according to the present invention, FIG. 4 is an explanatory view showing the details thereof in an enlarged manner, and FIG. FIG. 6 is a graph showing the results of a comparative test between the method of the present invention and the conventional method when no filler wire is used, and FIG. 6 shows the results of a comparative test between the method of the present invention and the conventional method when a filler wire is interposed. It is a graph.

First, in FIGS. 1, 2, 3 and 4, reference numeral 1 denotes a thick band-shaped metal material, 2 denotes a thin band-shaped metal material,
Reference numeral 3 denotes a backing metal, 4 denotes an output side clamping device, 5 denotes an input side clamping device, 6 denotes a laser beam, and 7 denotes a groove center line. Prior to welding, the thick metal strip 1 is clamped by the clamp device 4 on the output side, while the thin metal strip 2 is clamped by the clamp device 5 on the input side, and the opposite end faces of both metal materials 1 and 2 are butted. To form a butt groove.

If, for example, no filler wire is interposed in the butt groove, the laser beam 6 is irradiated obliquely downward from the thick metal strip 1 to the thin metal strip 2. In addition, the focal point of the laser beam 6 is brought into contact with the center of the groove.

When welding is performed in this manner, the passage of the laser beam 6 is centered on the groove from the shoulder 1a of the thick metal strip 1, so that the HAZ of the thick metal strip 1 is not embrittled. Insufficient penetration does not occur.

More specifically, when the band-shaped metal members 1 and 2 having different plate thicknesses are butt-welded without using a filler wire, the energy of the laser beam irradiated is such that the filler wire is melted or thickened. The metal strip 1 is not consumed for melting over the entire thickness direction. On the other hand, since the laser beam 6 is irradiated only on the shoulder 1a of the thick metal strip 1, only the shoulder 1a of the thick metal strip 1 is melted and the molten metal is opened. Inflow first.
For this reason, excessive heat input can be avoided on the side of the thick strip-shaped metal material 1. Further, since the laser beam 6 has a focus at the center of the groove, the energy density at the center of the groove becomes extremely high, so that a sufficient and good stirring force is applied to the molten metal in the groove. Therefore, the vicinity of the back bead on the side of the thick strip-shaped metal material 1 is also joined to the base material by the convection of the molten metal, and defects such as insufficient penetration can be prevented.

When welding is performed with a filler wire 8 interposed in place of the example shown in FIGS.
As shown in FIGS. 3 and 4, a filler wire 8 is supplied onto the thin strip-shaped metal material 2 at a groove formed by abutting the thick strip-shaped metal material 1 and the thin strip-shaped metal material 2. The laser beam 6 irradiates obliquely downward from above the thin band-shaped metal member 2 toward the back corner 1b of the thick band-shaped metal member 1 via the center of the filler wire 8. When laser beam welding is performed in this manner, embrittlement and insufficient penetration of the HAZ can be avoided.

That is, as shown in detail in FIG.
The beam 6 does not pass through the thick metal strip 1 but passes through the filler wire 8 and the shoulder 2a of the thin metal strip 2. Therefore, the laser beam energy is not involved in the melting of the surface side shoulder 1a on the side of the thick band-shaped metal material 1, and
It is involved in melting only the filler wire 8 near the groove and the shoulder 2a of the thin strip-shaped metal material 2, and the molten metal flows into the groove. Therefore, excessive heat input of the thick band-shaped metal material 1 can be avoided.

Further, the laser beam 8 is made of the thick metal strip 1.
To the corner 1b on the back side of the
Since the density is increased, the molten metal is agitated at the groove root, so that insufficient melting can be prevented.

FIG. 5 shows that the plate thickness is 3.5 mm and 2.5 mm.
FIG. 5 shows the results obtained by investigating the number of bends until a welded portion is broken by repeated bending after welding a stainless steel plate (SUS430) of this example by a method according to the present invention and a conventional method without using a filler wire.

FIG. 6 also shows that the plate thickness is 3.0 mm and 2.0 mm.
The result is obtained when a 5 mm stainless steel plate (SUS420J2) is welded using a filler wire.

In each case, it can be seen that the method of the present invention has greatly improved the weld strength compared to the conventional method.

[0027]

As explained in detail above, the method of the present invention comprises:
This is a method in which opposing ends of strip-shaped metal materials having different plate thicknesses are butted, and a laser beam is radiated diagonally downward on the butted groove to perform butt welding. Therefore,
The laser beam irradiated obliquely downward only partially melts the thick band-shaped metal material, and the mechanical strength of the heat-affected zone is sufficiently maintained.

Further, even when no filler wire is interposed, the laser beam irradiated obliquely downward is directed from a thick metal strip to a thin metal strip.
When the focal position is aligned with the center of the groove, the energy density of the laser beam at the center of the groove is increased, and the effect of stirring the molten metal is given.

When a filler wire is interposed, the laser beam irradiated obliquely downward is directed from a thin metal strip to a thick metal strip, and the center line of the laser beam is set to the center of the filler wire. A line connecting the center of the diameter and the corner of the opposite end face of the thick band-shaped metal material is aligned. Also in this case, similarly, the effect of stirring the molten metal is given, and good beads can be obtained on both the front and back surfaces.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a case where welded joints having different plate thicknesses are formed without using a filler wire according to the present invention.

FIG. 2 is an explanatory diagram showing the details in an enlarged manner.

FIG. 3 is an explanatory view of an example of a case where welded joints having different plate thicknesses are formed with a filler wire interposed according to the present invention.

FIG. 4 is an explanatory diagram showing the details in an enlarged manner.

FIG. 5 is a graph showing a comparison test result between the method of the present invention and a conventional method when no filler wire is used.

FIG. 6 is a graph showing the results of a comparative test between the method of the present invention and the conventional method when a filler wire is interposed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thick strip-shaped metal material 2 Thin strip-shaped metal material 3 Backing metal 4 Clamping device on the outgoing side 5 Clamping device on the incoming side 6 Laser beam 7 Groove center line

Claims (2)

(57) [Claims] An abutting groove is formed by abutting opposing end portions of strip-shaped metal materials having different plate thicknesses, and the abutting groove is moved from the thick metal strip to the thin metal strip. A laser beam welding method for a strip-shaped metal material having a different plate thickness, wherein a laser beam is irradiated obliquely downward and the focal position is adjusted to the center of the butting groove. 2. A butt groove is formed by abutting opposing ends of strip-shaped metal materials having different plate thicknesses, and a filler wire is supplied on the thin strip-shaped metal material at the butt groove to form the butt groove. A laser beam is radiated obliquely downward from the thin strip-shaped metal material to the thick strip-shaped metal material, and the center line is set so that the center of the diameter of the filler wire faces the thick strip-shaped metal material. A laser beam welding method in which a filler wire of a band-shaped metal material having a different plate thickness is interposed on a line connecting a corner portion of an end face with a corner portion.