JP2013166160A - Shielding gas jetting method in laser welding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a shielding gas jetting method in which laser welding with less defects is executed by changing the jetting direction of shield gas to cover a weld part.SOLUTION: In a shielding gas jetting method for jetting shielding gas to a weld part of a first base material 11 to be welded and a second base material 12 to be welded which are subjected to the laser welding, the shielding gas is jetted from a nozzle 18 parallel to at least any one surface of the first and second base materials 11, 12 to be welded and immediately above the weld part. Preferably, the flow rate of shielding gas to be jetted from the nozzle 18 is in a range of 8-30 L/min, the distance between the axis of the nozzle 18 and the weld part is in a range of 15-30 mm, and the distance between a jetting port 23 of the nozzle 18 and the laser beam for executing the laser welding is in a range of 20-50 mm.

Description

The present invention relates to a shielding gas ejection method used when laser welding is performed on first and second workpieces to be welded using laser light.

Usually, as a method for shielding a welded portion in laser welding, a center nozzle method for injecting a shielding gas to the welded portion along a laser beam and a side nozzle method for injecting a shielding gas obliquely from above (see Patent Document 1) have been proposed. It was. In particular, Patent Document 2 is a side nozzle system in which a shielding gas is directed to plasma, and the shielding gas is sprayed in a curtain shape to remove the plasma that causes stagnation of melting, and the melting portion is cooled by this shielding gas to melt. A technique for narrowing the width and increasing the penetration depth has been proposed.

Patent Document 3 describes that when a relatively thick material is welded by a high-power laser, the angle of the gas nozzle is changed to reduce spot defects and improve the quality and yield of the welded portion.

JP 2003-154476 A Japanese Patent No. 3098088 Japanese Patent No. 3694979

However, as shown in FIG. 2B, when butt welding is actually performed with the angle of the gas nozzle inclined with respect to the laser beam irradiation direction, the gas pushes the molten metal into the groove, and porosity ( It was found that air bubbles) were generated, which caused poor welding.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for jetting shield gas in laser welding in which laser welding with fewer defects is performed by changing the jet direction of the shield gas covering the welded portion. To do.

A method for jetting shield gas in laser welding according to the present invention that meets the above-described object is a method for injecting shield gas to a welded portion of a first welded base material and a second welded base material that perform laser welding. ,
The shield gas is ejected from the nozzle in parallel to at least one of the surfaces of the first and second workpiece base materials and directly above the weld.

In the method for jetting shield gas in laser welding according to the present invention, the flow rate of the shield gas blown from the nozzle is in the range of 8 to 30 L / min (liters / minute), and the distance between the axis of the nozzle and the welded portion is 15. The distance between the nozzle outlet and the laser beam for laser welding is preferably in the range of 20 to 50 mm.

Further, in the method for jetting shield gas in laser welding according to the present invention, the nozzle has a cylindrical jet nozzle, and a gas lens for equalizing the flow of the shield gas is provided inside the nozzle. preferable.

In the method for ejecting shield gas in laser welding according to the present invention, the flow rate of the shield gas ejected from the nozzle is preferably in the range of 6 to 25 m / sec.

Then, the ejection method of shielding gas in the laser welding according to the present invention, preferably the shielding gas is Ar or N _2.

In the method of jetting shield gas in laser welding according to the present invention, the shield gas is parallel to at least one of the surfaces of the first and second workpieces to be welded and directed from the nozzle directly above the weld. Since it is ejected, the molten metal in the welded portion is covered with the shielding gas, and the molten metal is not forced into the root gap and does not block the minute space generated in the welded portion. Therefore, the welded portion has no or very little porosity.

In the method for jetting shield gas in laser welding according to the present invention, the flow rate of the shield gas blown from the nozzle is in the range of 8 to 30 L / min, the distance between the nozzle axis and the welded portion is in the range of 15 to 30 mm, and the nozzle When the distance between the jet port and the laser beam for laser welding is in the range of 20 to 50 mm, the shield gas covers the weld and the force of the shield gas that pushes down the molten metal at the weld is small. The generation of porosity is drastically reduced as compared with the case where the shielding gas is blown from the oblique direction or upward direction to the welded portion.

In particular, in the method for jetting shield gas in laser welding according to the present invention, when the nozzle nozzle has a cylindrical nozzle and a gas lens for equalizing the flow of the shield gas is provided inside the nozzle, the nozzle is jetted from the nozzle. The flow of shielding gas is rectified and can cover a wider area directly above the weld.

In the method of jetting shield gas in laser welding according to the present invention, when the flow velocity of the shield gas jetted from the nozzle is in the range of 6 to 25 m / sec, a plume (metal vapor or (Plasma) is blown away, and the shielding of the laser beam is reduced, and the efficiency of laser welding is increased.

It is a schematic explanatory drawing of the ejection method of the shield gas in the laser welding which concerns on one embodiment of this invention. (A) is explanatory drawing of the injection method of the shield gas in the laser welding, (B) is explanatory drawing of the injection method of the shield gas in the laser welding which concerns on a prior art example. It is an arrangement plan of the 1st welding base material and the 2nd welding base material which were performed in order to confirm the operation and effect of the shielding gas ejection method in the laser welding. (A), (B) is a graph which shows the supply amount of shield gas, and generation | occurrence | production of a porosity, respectively. (A), (B) is a graph which shows the supply amount of a shield gas, and the generation | occurrence | production state of a plume, respectively. It is a graph which shows the relationship between average plume height, shield gas supply amount, and porosity. It is a graph which shows the relationship between a shield gas supply amount, a groove gap, and a porosity.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.
First, with reference to FIGS. 1 and 2, a welding method and apparatus to which a shield gas injection method in laser welding according to an embodiment of the present invention is applied will be described.

As shown in FIG. 1, a gantry 10 having a gap in the center, and a first welded base material 11 and a second welded material arranged on the gantry 10 so as to face each other in front and back of FIG. 1. A test material 13 composed of a base material 12 (each base material), a laser welding head 14 disposed toward a welded portion (butting portion) of the test material 13, and a laser welding head 14 are held in a vertical state to guide And a carriage 16 that moves in the horizontal direction along the member 15.

The carriage 16 is provided with a nozzle 18 that ejects shield gas through a support member (not shown). The nozzle 18 is parallel to the surfaces (planes) of the first and second workpiece base materials 11 and 12 and is disposed immediately above the welded portion (more precisely, the planned welding portion, that is, the weld line). The distance c between the axis of the test material 13 and the surface of the test material 13 is in the range of 15 to 30 mm (preferably 18 to 25 mm), and the laser beam from the vertically oriented laser welding head 14 and the jet port 23 of the nozzle 18 The distance d is in the range of 20-50 mm. If the distance c is shorter than 15 mm, the nozzle 18 may come into contact with the surface of the test material 13, and if the distance c exceeds 30 mm, the gas generated from the nozzle 18 does not shield the weld. Moreover, when the distance d is out of the range of 20 to 50 mm, it is difficult to cover the welded portion with gas. As a result, the portion directly above the weld that is directly irradiated with the laser light is covered with the shielding gas.

A fiber laser welding method is applied to the laser welding head 14, and laser light emitted from the laser oscillator main body 19 is sent to the laser welding head 14 via the optical fiber 20. In this embodiment, a laser beam having a maximum output of 2 kW was irradiated from the laser welding head 14 to the welded portion, and the focal length was 250 mm and the focused diameter was 480 μm.

The diameter e of the cylindrical outlet 23 on the exit side of the nozzle 18 is 10 mm, Ar gas is used as a shielding gas, and a gas lens having a known structure for equalizing the flowing gas is arranged in the nozzle 18. ing. The flow rate at the nozzle 23 of the nozzle 18 is 6 to 25 m / sec, and a part of the laser beam irradiation position, that is, the axis of the laser welding head 14, diffuses at a low speed to cover the welded portion. It is like that. In addition, the nozzle 18 used the linear shape over the full length, and the bending part (bending on the way) which forms a turbulent flow and a bending flow from a jet nozzle does not exist. Here, the flow rate of the shield gas ejected from the nozzle 18 is about 8 to 30 L / min.

The first and second base materials 11 and 12 to be welded are made of a normal steel plate (SS400) having a thickness of 4.5 mm, arranged with a root gap (gap) of 0.1 to 0.3 mm, and a welding speed of 12 When welding was performed at ˜20 mm / sec (more specifically, 14-18 mm / sec), good welding with a back wave was possible. When the weld was cut and inspected for the presence of porosity, there was little porosity. FIG. 3 shows an example in which one route gap is 0, the other is 0.3 mm, the weld length is 220 mm, and the route gap is gradually changed.

Then, Example 1 performed in order to confirm the effect | action and effect of invention is demonstrated. In FIG. 2A, the nozzle 18 is horizontal to the surface of the test material 13 and parallel to the weld (that is, parallel to the surface of the weld line), but the nozzle 18 is horizontal. An experiment was conducted to check that the nozzle 18 was better than the case where the nozzle 18 was inclined as shown in FIG. In FIG. 2B, the angle of the nozzle 18 with respect to the surface of the test material 13 is 40 degrees, the distance from the welded portion to the nozzle outlet 23 of the nozzle 18 is 40 mm, the flowing gas, its flow rate, and other conditions Was the same as in FIG.

According to the experiment, when the nozzle 18 is inclined, the amount of porosity generated in the welded portion is larger than when the nozzle 18 is horizontal. The cause of this is that the gas generated from the nozzle 18 in which the molten metal melted by the laser beam is inclined is pushed into the welded portion, thereby increasing the amount of porosity generated. In addition, even in the method of flowing the gas flow coaxially with the laser beam, it is confirmed that the porosity is high because the weld is suppressed by the gas.
Here, it is conceivable to reduce the flow velocity from the nozzle. However, if the gas flow rate is reduced, the plume generated from the welded portion cannot be removed, and as a result, the plume blocks the laser beam, thereby reducing the welding heat input.

Next, in Example 2, an experiment was conducted to examine the relationship between the groove gap (root gap) of the first and second workpieces 11 and 12, the amount of gas supplied to the nozzle 18, and the porosity level. It was. The first and second welded base materials 11 and 12 (thickness is 4.5 mm, width is 100 mm, and length is 300 mm) in which the welded portion is flat are in contact with each other, and a 0.3 mm spacer is disposed on the other side. Then, laser welding was performed by gradually changing the groove gap and setting the nozzle 18 horizontal as shown in FIG. Thereby, the welding situation when the groove gap is changed can be easily grasped. The results are shown in FIGS. 4 (A) and 4 (B). When the welded portion does not penetrate vertically in the thickness direction and an unwelded portion remains on the back side (referred to as “partial penetration welding”), the welded portion has a groove gap. Is shown in the case of penetrating vertically (referred to as “penetrating welding”).

4 (A) and 4 (B), the case where the porosity reaches the entire welded line is 1, and the state where there is no porosity is 5, and it is shown in five stages according to the amount of porosity. When Ar is used as the shielding gas, no porosity is generated at a gas supply rate of 10 L / min in FIG. 4A, but a porosity is generated when the gas supply rate is increased (for example, 35 L / min). There was a trend. In addition, as shown in FIG. 4B, in the case of through welding (when all of the butt surfaces are melted), there was almost no generation of porosity. When the shielding gas was N ₂ , as shown in FIGS. 4A and 4B, no porosity was generated at a gas supply rate of 20 L / min.

Next, FIGS. 5A and 5B show the relationship between the shielding gas supply amount and the plume height when the shielding gas is Ar or N ₂ , as shown in FIG. 5B. In the case of through welding, no correlation with the plume height was observed even when the flow rate of the shielding gas was changed. Further, as shown in FIG. 5A, in the case of partial penetration welding, it can be seen that the plume height is higher than that of through welding. From these facts, it can be seen that plumes are ejected from the irradiated surface side and the back surface side in the case of through welding. Note that the plume height did not change even when the gas type (Ar, N ₂ ) was changed.

FIG. 6 is a graph showing the amount of shield gas supplied and the occurrence of porosity. Here, a solid line shows penetration welding and a broken line shows partial penetration welding. Further, unless otherwise specified, 1) the shielding gas is Ar, 2) the nozzle is a horizontal nozzle, and 3) the direction of ejection from the nozzle is from the front to the rear in the welding direction. It can be seen that the use of a nozzle inclined with respect to the laser optical axis causes a lot of porosity, and if the nozzle is made horizontal, the generation of porosity decreases. Also, penetration welding has less porosity than partial penetration welding.

FIG. 7 shows the shielding gas supply amount and the gap (groove gap) where continuous welding is started and the porosity under the welding conditions. In the case where the nozzle is horizontally arranged, the inclined nozzle is used in any case. It can be seen that the porosity decreases more.
Table 1 shows the occurrence of porosity when the energy density such as laser output is changed. It can be seen that the occurrence of porosity is reduced or reduced in the case of a horizontal nozzle even if the laser output is changed. Here, the defocusing distance refers to the distance from the surface of the welded portion to the focal point of the laser beam (since it is in the test material, it is displayed as a minus sign).

Ar gas shielding gas, and _{N 2} do welding test using a gas, the joint tensile and bending test (JISZ3121, JISZ3122) were subjected to, in a tensile test fracture matrix, the tensile strength 515n / mm ² or more There was no flaw even in the bending test.

The present invention is not limited to the above embodiment, and can be changed without changing the gist of the present invention. For example, laser welding output, nozzle diameter, test material thickness, etc. are arbitrary.

For example, the position of the gas lens may be not only in the nozzle but also in the support member through which the gas passes in front of the nozzle. In addition, the joint to be welded is I-type butt in the embodiment, but the present invention can also be applied to Y-type butt, T-joint, square joint, lap joint, and helicopter joint.

The present invention can also be applied to the case where a filler wire is supplied to the laser welding portion, or to laser arc hybrid welding in which a voltage is applied to the wire to generate an arc.

10: mount, 11: first welded base material, 12: second welded base material, 13: test material, 14: laser welding head, 15: guide member, 16: carriage, 18: nozzle, 19: Laser oscillator body, 20: optical fiber, 23: jet outlet

Claims (5)

A method for injecting a shielding gas to a welded portion of a first welded base material and a second welded base material that performs laser welding,
The shield gas in laser welding, wherein the shield gas is jetted from a nozzle parallel to at least one surface of the first and second workpiece base materials and directly above the weld. How to erupt. 2. The method of jetting shield gas in laser welding according to claim 1, wherein the flow rate of the shield gas blown from the nozzle is in the range of 8 to 30 L / min, and the distance between the axis of the nozzle and the weld is in the range of 15 to 30 mm. And the distance of the nozzle outlet and the laser beam for laser welding is in the range of 20 to 50 mm, the method for jetting shield gas in laser welding. 3. The method of jetting shield gas in laser welding according to claim 2, wherein the nozzle has a cylindrical jet nozzle, and a gas lens for equalizing the flow of the shield gas is provided inside the nozzle. A method of jetting shield gas in laser welding. In the laser welding method in the laser welding in any one of Claims 1-3, the flow velocity of the shielding gas injected from the said nozzle exists in the range of 6-25 m / sec. Shield gas ejection method. The method for jetting shield gas in laser welding according to claim 1, wherein the shield gas is Ar or N ₂ .

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