JP2012206144A - Laser narrow groove multi-pass welding method and apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser narrow groove multi-pass welding method and apparatus which can securely perform, with a low output laser, narrow groove multi-pass welding of a welding base metal made of metal which is a thick plate, where a narrow groove of width 4-6 mm is provided.SOLUTION: In the laser narrow groove multi-pass welding method, a laser spot 21 obtained by removing the focus of laser light 2 is irradiated to a welding base metal 8 made of metal which is processed so as to be a narrow groove, and at the same time, a hot wire 3 is supplied to the center of molten portion of the base metal 8 to form a molten metal pool 7, welding is performed by reciprocatingly scanning the laser spot 21 on an approximately U-shaped trajectory passing through on the borderline of the molten metal pool 7 and a front groove bottom face 12 so as not to irradiate between the borderline of a groove wall surface 10 or 11 which is respectively on the same side sandwiching the wire 3 and the molten metal pool 7 and the side edge of the wire 3, and the wire 3.

Description

  The present invention relates to a welding method in which laser welding and hot wire welding are combined, and particularly to a laser narrow gap multi-layer welding method and apparatus suitable for high-efficiency welding of steel plates or steel pipes having a thickness of 20 mm or more used for pressure vessels. .

  Laser welding is welding using laser light as a heat source. In laser welding, due to the difference in energy density, (a) "Keyhole type welding" in which the laser beam is concentrated at one point to evaporate the material at the irradiation position and deep penetration is obtained by the reaction force of the generated metal vapor jet. And (b) “thermal conduction type welding” in which fusion bonding is performed by dispersing a laser beam in a relatively wide range.

  For keyhole type welding, there is a method of using a laser of 10 kW to 20 kW, for example, for thick plate welding of 20 mm or more. While this method makes it possible to improve the efficiency of welding, it becomes a so-called deep-penetration weld metal whose depth increases with respect to the width of the weld metal. Cracks are likely to occur at the center of the part, resulting in welding defects.

  For heat conduction type welding, there is a method using a low to medium power laser of about 0.1 kW to 5 kW for thin plate or foil welding or brazing (joining method in which the base material does not melt). Although this method does not generate metal vapor and hardly causes defects, it cannot be used for welding thick plates because the penetration is shallow.

  Patent Document 1 discloses a method of performing laser welding while adding a filler wire to a workpiece in which a narrow groove is provided on the end face of the material, with regard to welding of thick materials. According to this method, there is provided a narrow groove laser welding method for promoting melting of the groove wall surface by installing a mirror above the groove and amplifying the laser beam transversely with respect to the welding progress direction by the mirror. It is disclosed. This method melts the part of the groove wall directly irradiated by the laser and ensures that the weld metal and the metal weld base are integrated, so there are few welding defects even with a low-power laser. Thick plates can be melt-bonded.

  Patent Document 2 discloses a method of periodically swinging an irradiation position of a laser beam with a predetermined amplitude at a bottom portion of a groove in a left-right direction with respect to a traveling direction and a direction perpendicular to a groove wall surface in narrow groove welding. And a control method for maintaining the target position of the filler wire at the center of the groove, and a method of feeding an inert gas shield for eliminating metal vapor. According to these methods, inadequate fusion between the weld bead and the groove wall surface is prevented, and the filler wire is welded to the groove wall surface, the feeding failure, and the fusion defect due to a shift in the target position of the filler wire. High-efficiency welding is possible while preventing this.

JP-A-62-220293 JP 2011-5533 A

  The laser welding methods described in Patent Document 1 and Patent Document 2 have a great effect on melting of the groove wall surface by amplifying the laser beam in the lateral direction or the vertical direction with respect to the traveling direction. On the other hand, since the groove bottom is heated through the molten pool, unwelded defects are likely to occur between the weld layers when the weld beads are stacked inside the groove with a relatively low laser output.

  As described above, in laser narrow groove welding of a high-strength heat-resistant material used for a boiler main pipe having a groove width of 3 mm to 10 mm, when the low-power laser is used, the groove bottom surface and the left and right openings are opened. It has been a conventional problem to reliably weld the front wall surface. In addition, when a high-power laser is used, it is a problem to prevent defects called pear-shaped bead cracks caused by the deep penetration shape of the weld metal.

  Accordingly, an object of the present invention is to provide a laser narrow opening capable of reliably performing narrow groove multi-layer welding of a metal welding base material, which is a thick plate and provided with a groove having a width of 4 mm to 6 mm, with a low output laser. It is to provide a multi-layer prime welding method and apparatus.

The above problem is solved by the following configuration.
According to the first aspect of the present invention, energization is performed between the welding base material and the filler wire while irradiating a laser beam out of focus on the molten pool formed on the groove bottom surface of the metal base material subjected to narrow groove processing. In the laser narrow gap multi-layer welding method performed while supplying the hot wire, the laser spot obtained by defocusing the laser beam on the surface of the molten pool formed on the bottom surface of the groove is the same across the filler wire A substantially U-shaped trajectory that passes between the boundary surface of the groove wall on the side and the boundary of the molten pool and the side edge of the filler wire, and passes through the boundary line between the molten pool and the front groove bottom without irradiating the filler wire. A laser narrow gap multi-layer welding method characterized in that continuous welding is performed by reciprocating the top.

In the invention according to claim 2, when the laser spot diameter (R) is the width (t) of the pair of groove wall surfaces and the wire diameter (w), the following formula (1)
(T−w) / 4 ≦ R ≦ (t−w) / 2 (1)
The range of the laser spot diameter (R) satisfying the above relationship and the range of the energy density of the laser spot at the target position of the laser light is 0.5 to 2.0 kW / mm ^2. 1 is a laser narrow gap multi-layer welding method.

  In the invention according to claim 3, the number of times that the laser spot passes between the boundary line between the molten pool and the left and right groove wall surfaces and the filler wire in one laser spot scanning cycle passing through the substantially U-shaped locus, 3. The laser narrow gap multi-layer welding method according to claim 2, wherein the number of passes through the boundary line between the molten pool and the front groove bottom surface is changed.

  According to a fourth aspect of the present invention, there is provided a filler wire feeding nozzle for feeding a filler wire to a groove center portion of a metal weld base material processed into a narrow groove shape, and a filler for obtaining a hot wire. Heating power supply device for wire, inert shield gas supply device for supplying inert shield gas to welded portion, monitoring camera for monitoring molten pool formed in molten portion, filler wire on molten pool A substantially U-shaped trajectory that passes between the boundary of the groove wall and the molten pool on the same side and the filler wire side edge, and on the boundary between the molten pool and the front groove bottom surface so as not to irradiate the filler wire. Laser equipped with a laser device having a laser spot scanning mechanism for reciprocally scanning a laser spot obtained by removing the focal point of the laser beam and irradiating the weld with the laser beam. The groove is a multi-pass welding equipment.

(Function)
The inventions according to claims 1 to 4 of the present invention have the following effects.
According to the first aspect of the present invention, the laser spot is formed between the groove wall surface on one side of the molten pool surface with respect to the traveling direction on the surface of the molten pool, the boundary line of the molten pool, and the filler wire side edge. Laser spot reciprocatingly scans on a substantially U-shaped trajectory passing through the boundary line between the molten pool and the front groove bottom, thereby promoting the welding promotion of the weld metal constituting the groove wall surface and the groove bottom surface And the formation of a concave weld bead has the effect of suppressing weld defects when depositing weld metal.

  Among these, the laser spot passes between the groove wall and the boundary between the molten pool and the filler wire side edge, so that the laser beam reflected by the molten pool surface irradiates and melts the groove wall. And the weld metal are promoted. Furthermore, the irradiation position of the laser spot exceeds the filler wire and is irradiated to the rear side with respect to the welding direction, so that the center part of the weld bead is lower than the wall surface part, so-called concave bead is formed and welded. Generation of defects during the lamination of metal (welded weld metal) is suppressed.

  On the other hand, when the laser spot does not pass between the boundary between the groove wall and the molten pool and the filler wire side edge, a groove-like weld defect called undercut is formed between the weld bead and the weld base material. At the same time, a convex bead is formed. When a weld metal is laminated on the convex bead, an unwelded defect is generated in which no welding is performed on the groove wall surface between the layers (see FIGS. 9D and 9E).

Further, when the laser spot passes over the filler wire, the filler wire is blown by laser irradiation. At that time, droplets (spatters) are scattered inside the groove wall surface or the groove bottom surface, or the filler wire is cut, so that the energization heating is stopped, which hinders the welding operation.
Furthermore, when the laser spot passes outside the groove wall surface, the upper surface of the metal weld base metal melts, which becomes an obstacle to continued welding, and the laser beam irradiation to the molten pool becomes insufficient. The welding operation is hindered.

  In addition, since the laser spot passes on the boundary line between the melt pool and the front groove bottom surface, there is an effect of promoting melting of the groove bottom surface. On the other hand, when the laser spot passes on the groove bottom surface on the front side in the traveling direction from the boundary line between the molten pool and the groove bottom, or when the laser spot passes on the surface of the molten pool, Unwelded defects occur between the weld layers.

  Furthermore, it is desirable that the scanning speed of the laser spot on the substantially U-shaped trajectory be in the range of 20 to 200 mm / s. When the scanning speed of the laser spot is larger than this range, the groove is not melted even by laser irradiation, and the weld metal is not deposited. If the scanning speed is less than this range, the melt pool shrinks and the filler wire cannot be inserted into the melt pool.

According to the second aspect of the present invention, the range of the spot diameter (R) of the laser that is reciprocally scanned is the following formula (1) between the width (t) of the pair of groove wall surfaces and the wire diameter (w). It is desirable that there is a relationship.
(T−w) / 4 ≦ R ≦ (t−w) / 2 (1)
When the spot diameter (R) is larger than this range, the laser beam interferes with the filler wire or the upper surface of the metal welding base material. Be inhibited. Further, when the spot diameter (R) is smaller than this range, it becomes difficult to sufficiently reflect the laser beam on the groove wall surface. That is, in the narrow groove welding method of the present invention, the groove wall surface is substantially parallel to the optical axis of the laser beam, and in order to promote welding of the groove wall surface and the weld metal, the laser beam is irradiated on the surface of the molten pool. It is necessary to reflect and melt the groove wall surface by the reflected light. For this reason, when the spot diameter (R) is smaller than this range, a portion that does not melt due to the reflection of the laser beam is likely to be generated, so that an unwelded defect on the groove wall surface is likely to occur.

Further, the energy density of the laser spot having the spot diameter (R), that is, the range of the value obtained by dividing the laser output by the area of the spot is preferably 0.5 to 2.0 kW / mm ² . When the energy density of the laser spot exceeds 2.0 kW / mm ² , the evaporation of the weld metal at the laser irradiation position becomes active, and the metal vapor adheres to the groove wall surface and inhibits the welding metal from being welded. It is limited to 2.0 kW / mm ² or less. Further, when the energy density is 0.5 kW / mm ² or less, the groove wall surface is not melted by the reflected light.

  According to the third aspect of the invention, by increasing the number of repetitions of the laser spot in the left molten pool region or the right molten pool region of the laser spot with respect to the welding progress direction in one laser spot scanning cycle. The effect of promoting melting of the groove wall surface is obtained. That is, for the four laser spot passing points A to D shown in FIG. 7, (B → A → B → A → B) → (C → D → C → D → C) → (B → A → B → A). By repeatedly scanning the laser spot as in (B) → (C → D → C → D → C), there is an effect of promoting the welding between the groove wall surface and the weld metal.

  When the number of repetitions increases, the width of the molten pool further increases. However, when the molten pool width increases excessively, a recess called an undercut is generated at the boundary between the groove wall surface and the molten pool. Since unwelded defects occur in the undercut portion, there is a range in the number of repetitions in which welding defects are suppressed. In addition, since there is an upper limit on the moving speed of the laser spot depending on the laser scanner device, if the number of repetitions is increased and the laser scanning cycle becomes longer, unmelted defects may occur periodically on the groove bottom surface. is there.

  According to the fourth aspect of the present invention, a laser device that combines a plurality of mirrors called laser scanners is used to scan a laser spot two-dimensionally with respect to the vicinity of the weld on the surface of the molten pool. The laser spot can also be two-dimensionally scanned by moving the head.

  The molten pool monitoring camera is a device that is used to observe the molten pool from the same direction as the laser beam irradiation direction and determine the scanning range of the laser spot, but is a camera installed in a direction different from the optical axis of the laser May be used.

  The filler wire is used for forming a weld metal for filling the space inside the groove. A current is passed between the filler wire and the weld base material by a hot wire heating power supply device, and the filler wire is Joule heated. Thereby, even if it uses a low output laser welding apparatus, there exists an effect by which the magnitude | size of a fusion pool is maintained.

The filler wire supply nozzle is made of, for example, a heat-resistant ceramic having a guide hole for the filler wire inside, and is used to guide the filler wire softened by energization heating to the center of the molten pool. The filler wire contacts the groove wall surface. It has the effect of preventing the welding operation from being hindered by adhering. By flowing argon, nitrogen, carbon dioxide gas, helium, or a mixed gas thereof from the inert shield gas supply device inside the guide hole, an anti-oxidation effect of the high-temperature molten pool, high-temperature deposited metal and filler wire is obtained. It is done.

  According to the first and fourth aspects of the present invention, any one of the wall surfaces of the groove on the same side of the molten pool surface with respect to the welding progress direction, the boundary line of the molten pool, and the welding wire side edge The laser spot is reciprocated on a substantially U-shaped trajectory passing through the boundary line between the molten pool and the front groove bottom surface so as not to irradiate the welding wire. Due to the melting acceleration effect and the formation of the concave weld bead, there is a weld defect suppression effect when the deposited metal is laminated.

  According to the second aspect of the present invention, the relationship of the above formula (1) among the spot diameter (R) of the laser that is reciprocally scanned, the width (t) of the pair of groove wall surfaces, and the wire diameter (w). As a result, the laser beam does not interfere with the filler wire or the upper surface of the metal welding base material, and the laser beam is sufficiently reflected on the groove wall surface, so that no unwelded defects on the groove wall surface are generated. .

  According to the third aspect of the present invention, the effect of promoting the melting of the groove wall surface is obtained by increasing the number of repetitions of the laser spot in the left melting pool region or the right melting pool region in one laser spot scanning period. It is done.

It is a schematic diagram which shows the apparatus structure used in the Example of this invention. It is a schematic diagram which shows the structure of the laser scanner of this invention. It is a molten pool image during welding acquired with the surveillance camera of the present invention. It is a figure explaining the boundary line of the left and right groove wall of this invention, a front groove bottom face, and a molten pool. It is a figure explaining the maximum diameter of the laser spot diameter of this invention. It is a figure explaining the laser irradiation range of this invention. The passing point of the laser irradiation path of the present invention is shown. It is a laser spot condition range used in the embodiment of the present invention. Cross-sectional schematic diagram of welding test results It is the penetration cross-sectional shape of the welding part obtained by the method of the Example of this invention. It is the penetration cross-sectional shape of the welding part obtained by conventional keyhole type welding.

[Example 1] to [Example 9]
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 schematically shows a configuration of a welding apparatus used for laser narrow gap multi-layer welding according to the present invention and a situation during welding as viewed from the right side with respect to the welding progress direction. Laser light 2 is irradiated toward the molten pool 7 from a laser welding head 1 provided in the laser device 24. The filler wire nozzle 4, which is a heat-resistant ceramic tube, has a guide hole for the filler wire 3, and the filler wire 3 is exposed from the tip of the filler wire nozzle 4. Further, the hot wire heating power supply device 5 causes a current to flow between the filler wire 3 and the base material 8 to heat the filler wire 3 by Joule heat. The filler wire nozzle 4 is fixed so that the filler wire 3 can be fed from the rear side in the welding direction toward the laser irradiation position at an angle of 80 ° from the rear side in the traveling direction with respect to the groove bottom surface 12.

  Then, the tip of the heated filler wire 3 is inserted into the molten pool 7 formed at the tip of the weld metal 20 of the base material 8. In order to prevent the molten pool 7 and the high-temperature weld metal 20 from being oxidized, the weld gas is ejected from the shield gas supply nozzle 6 to the weld using an inert gas such as argon gas. In this embodiment, argon gas is used as the inert gas, but nitrogen, carbon dioxide gas, helium, or a mixed gas thereof may be used.

  In this embodiment, the focal position of the laser beam 2 is set above the weld so that the laser spot 21 (see FIG. 5) is formed on the surface of the molten pool 7.

  As shown in FIG. 2, the laser welding head 1 has a built-in laser beam two-dimensional scanning mechanism composed of an X-axis mirror 31 and a Y-axis mirror 32, that is, a so-called laser scanner. The light is reflected by the axial mirror 31 and the Y-axis mirror 32 to irradiate a two-dimensional irradiation range 34. A fusion pool observation coaxial camera 9 is connected to the laser welding head 1 and is surrounded by groove wall surfaces 10 and 11 and a groove bottom surface 12 of the base material 8 as shown in the plan view of the welded portion in FIG. The filler wire 3 is inserted into the region, and the molten pool 7 is formed around the tip of the filler wire 3 by an image obtained by the camera 9. From this image, a left molten pool region 16, a front molten pool irradiation region 17, and a right molten pool region 18 in the welding progress direction as shown in the plan view of the welded portion in FIG. 4 are obtained. The boundary line 13 between the molten pool 7 and the groove tip is formed by the irradiation of the laser beam 2 in the left molten pool region 16, the front molten pool irradiation region 17, and the right molten pool region 18, and the groove wall surfaces 10, 11 and the groove. It is formed between the bottom surface 12.

  The diameter R of the laser spot 21 shown in the plan view of the welded portion in FIG. 5 is assumed to be equal to the length from the side edge of the filler wire 3 to the groove wall surface 10 or 11 on the same side.

  As shown in correspondence with the plan view of the welded portion in FIG. 6, the movement locus 23 of the laser spot 21 is substantially U-shaped, and the laser beam 2 reciprocally scans the laser irradiation range 22.

表１には、本発明の各実施例と比較例で用いた溶接条件と、そのときの溶接欠陥の発生状況を示す。この溶接実験では、いずれの溶接速度も３００ｍｍ／分としたが、１００〜８００ｍｍ／分までの範囲での接合が可能である。また、フィラーワイヤ３の送給量Ｌ(ｍｍ／分)は開先幅ｔに対してＬ＝１９０×ｔ²とし、高さ約ｔ／２の分だけ、１パスごとに溶接金属が積層されるようにした。 Table 1 shows the results of a welding experiment that verified the effect of scanning the laser spot 21 on a substantially U-shaped movement locus. In this experiment, the base material 8 is the fire SCMV 28 plate material (thickness 30 mm), which is a steel material for boilers, and the opening angle is 1 ° and the opening width of the upper ends of the groove wall surfaces 10 and 11 is 2 to 10 mm. The filler wire 3 was TGS-9Cb (manufactured by Kobe Steel, Ltd.) having a diameter of 1.0 mm.

Table 1 shows the welding conditions used in the examples and comparative examples of the present invention, and the state of occurrence of welding defects at that time. In this welding experiment, all the welding speeds were set to 300 mm / min, but joining in the range of 100 to 800 mm / min is possible. The feed amount L (mm / min) of the filler wire 3 is set to L = 190 × t ² with respect to the groove width t, and the weld metal is laminated for each pass by the height of about t / 2. It was to so.

  Regarding the scanning speed of the laser spot 21, welding was possible in the range of 20 to 200 mm / second. If the scanning speed is too low as in Comparative Example 1, the molten pool region 17 and the molten pool region 18 are solidified while the laser is irradiating the molten pool region 16 in FIG. The joint could not be formed because it could not be inserted. On the other hand, as in Comparative Example 2, when the scanning speed was too high, the groove was insufficiently melted, resulting in an unwelded defect. In addition, when the groove width t is narrow as in Comparative Example 3, it is difficult to scan the laser spot 21 so as not to interfere with the filler wire 3, and the laser spot 21 becomes too small. Because of the high energy density, deep penetration occurred and cracks occurred in the center of the weld bead.

On the other hand, as in Comparative Example 4, when the groove width t is wide, the laser spot 21 becomes too large, and it becomes difficult to weld the groove wall surface. For this reason, the groove wall surface did not melt and welding of the weld metal was not performed.
Comparative Examples 5 and 6 are welding results when the laser beam 2 is swung left and right. When the groove width t was as narrow as 3 mm, a deep penetration shape was formed as in Comparative Example 3, and a crack occurred in the center of the weld metal. When the groove width t was 5 mm, this time, the melting of the groove bottom surface 12 became insufficient, and melt bonding was not performed.

  In Comparative Examples 7 and 8 in which the laser spot 21 was fixed, the laser beam 2 was reflected on the surface of the molten pool 7 and was welded to a part of the groove surface. As in this test example, Since the depth h of the weld bead was relatively large with respect to the groove width t, an unwelded defect was generated.

  In Comparative Examples 9 and 10 in which the laser spot 21 was swung back and forth, although melting of the bottom surface of the molten pool 7 was promoted, melting of the groove wall surface was not completely achieved.

[Example 10]
Welding when five-layer narrow groove welding is performed under the conditions of groove width t: 3 to 8 mm, filler wire diameter 1 mm, 1, 2 mm, welding speed: 300 mm / min, spot rocking speed: 100 mm / sec. The effect of laser spot condition on the defect was evaluated. FIG. 8 shows the laser output: P (kW), laser spot diameter R (mm), width t (mm) of the pair of groove wall surfaces 10 and 11, and wire diameter w (mm), and the specific spot diameter (= R / The state of welding was classified with ((t−w) / 2)) as the horizontal axis and energy density (= P / ((R / 2) ² · π)) as the vertical axis.

  In a region where the specific spot diameter exceeds 1, that is, in a region where the laser spot 21 interferes with the filler wire 3 or the metal welding base material upper surface (the base material upper surface adjacent to the groove wall surfaces 10 and 11), the filler wire 3 is blown, and laser irradiation is performed on the upper surfaces of the groove wall surfaces 10 and 11. In the case of the fusing of the filler wire 3, the droplet (sputter) in which the filler wire 3 was melted scattered inside the groove wall surfaces 10 and 11, which became an obstacle when the deposited metal was laminated. When laser irradiation is performed on the upper surface of the base material adjacent to the groove wall surfaces 10 and 11, the dimensions of the groove wall surfaces 10 and 11 are changed, making it difficult to continue welding. In the region where the specific spot diameter was 0.5 or less, the groove wall surfaces 10 and 11 were not sufficiently melted, and a portion where the weld metal and the groove wall surfaces 10 and 11 were not melt-bonded was observed.

In the region where the energy density exceeds 2.0 kW / mm ² , metal vapor was generated violently from the welded portion, causing deep penetration and cracking in the central portion of the weld metal. Further, in the region where the energy density is 0.5 kW / mm ² or less, the groove bottom surface 12 or the left and right groove wall surfaces 10 and 11 were not welded.

From the above results, as a condition range of the laser spot 21 that does not cause a welding defect, the geometric spot is a range in which the specific spot diameter is 0.5 to 1, that is, (tw) / 2 ≦ R ≦ (t− It is desirable to satisfy that the energy density range is 0.5 to 2.0 kW / mm ² as a thermal condition after satisfying the relationship of w) / 4.

[Example 11] to [Example 13]
Conditions of groove width t: 5 mm, filler wire diameter: 1 mm, welding speed: 300 mm / min, spot rocking speed: 100 mm / second, laser spot diameter: 2 mm, energy density of laser spot 21: 0.5 kW / mm ² Then, a welding method in which five layers of narrow gap welding are performed and the number of repetitions of the laser spot 21 is increased in the region of the left molten pool 7 or the region of the left molten pool 7 in one scanning cycle of the laser spot 21 is tested. did.

  Regarding four points of laser spot passing point A, passing point B, passing point C, and passing point D shown in FIG. 7, (B → A → B) → (C → D → C) → (B → A → B) → A scanning path corresponding to the substantially U-shaped scanning path of the first to ninth embodiments as (C → D → C) →... Is defined as a path having one iteration.

  On the other hand, (B → A → B → A → B) → (C → D → C → D → C) → (B → A → B → A → B) → (C → D → C → D → C) The case where the laser beam 21 is repeatedly scanned twice each in the region of the molten pool 7 on one side as defined in FIG.

  Table 2 shows a comparison of penetration shapes depending on the number of iterations. In the case of two or three iterations, the fusion of the groove wall surface was promoted to obtain a good weld cross section. When further increased, the groove wall surfaces 10 and 11 were melted significantly, resulting in a defect called undercut as shown in FIG. When the number of repetitions was further increased, an unmelted portion of the groove bottom surface 12 was observed.

こうして図１０の溶接部の溶け込み断面図に示すような、未溶着欠陥の無い、幅が広くて浅い溶接金属が積層された多層盛溶接が得られる。これは図１１に示す従来のキーホール型溶接によって得られる溶接部の溶け込み断面図と比較して、深い溶込形状によって生じる溶接金属の割れの抑制が可能となることが分かる。 9A is a normal weld cross section, FIG. 9B is a weld cross section in which the penetration is too deep and a crack has occurred in the center of the weld metal, and FIG. 11 is a welded cross section when an unwelded portion is formed on the lower side of groove 11 and groove bottom surface 12, and (D) shows a convex beat, and groove wall surfaces 10, 11 between layers remain unwelded. (E) is a welded cross section when a convex beat is formed and unwelded portions are formed on the groove wall surfaces 10 and 11.

In this way, multi-pass welding in which a wide and shallow weld metal is laminated without unwelded defects, as shown in the penetration sectional view of the welded portion in FIG. Compared with the penetration cross-sectional view of the welded portion obtained by the conventional keyhole type welding shown in FIG. 11, it can be seen that the crack of the weld metal caused by the deep penetration shape can be suppressed.

DESCRIPTION OF SYMBOLS 1 Laser welding head 2 Laser beam 3 Filler wire 4 Filler wire nozzle 5 Hot wire heating power supply device 6 Shield gas supply nozzle 7 Molten pool 8 Base material 9 Coaxial camera for molten pool observation 10 Groove left wall surface 11 Groove right wall surface 12 Groove bottom surface 13 Boundary line between molten pool and groove bottom surface 16 Left molten pool region 17 Front molten pool irradiation region 18 Right molten pool region 20 Weld metal 21 Laser spot 22 Laser irradiation range 23 Laser spot locus 24 Laser device 30 Laser light source 31 X-axis mirror 32 Y-axis mirror 34 Two-dimensional irradiation range

From the above results, the condition range of the laser spot 21 that does not cause a welding defect is a geometrical condition in which the specific spot diameter is in the range of 0.5 to 1, that is, (t−w) / 4 ≦ R ≦ (t− It is desirable to satisfy that the energy density range is 0.5 to 2.0 kW / mm ² as a thermal condition after satisfying the relationship of w) / 2 .

Claims (4)

It is performed while supplying hot wire that is energized between the welding base material and the filler wire while irradiating the laser beam out of focus to the molten pool formed on the groove bottom surface of the metal base material subjected to narrow groove processing. In laser narrow groove multi-layer welding,
The laser spot obtained by removing the focal point of the laser beam on the surface of the molten pool formed on the bottom surface of the groove is between the boundary surface of the groove wall on the same side of the filler wire, the boundary of the molten pool, and the filler wire side edge. Narrow groove multi-layer, characterized in that continuous welding is performed by reciprocating scanning on a substantially U-shaped trajectory passing through the boundary line between the molten pool and the front groove bottom surface without passing through the filler wire. Prime welding method. When the diameter (R) of the laser spot obtained by removing the focus of the laser beam is the width (t) of the groove wall surface and the wire diameter (w), the following equation (1)
(T−w) / 4 ≦ R ≦ (t−w) / 2 (1)
The range of the laser spot diameter (R) satisfying the above relationship and the range of the energy density of the laser spot at the target position of the laser light is 0.5 to 2.0 kW / mm ^2. 2. A laser narrow groove multi-layer welding method according to 1.   In one laser spot scanning cycle that passes through a substantially U-shaped locus of the laser spot obtained by defocusing the laser beam, the laser spot passes between the boundary between the molten pool and the left and right groove wall surfaces and the filler wire. 3. The laser narrow gap multi-layer welding method according to claim 2, wherein the number of times of passage and the number of times of passage on the boundary line between the molten pool and the front groove bottom surface are changed. A filler wire feeding nozzle for feeding a filler wire to a groove central portion of a metal welding base material processed into a narrow groove shape;
A filler wire heating power supply device for obtaining a hot wire, an inert shield gas supply device for supplying an inert shield gas to the weld, and
A monitoring camera for monitoring the molten pool formed in the melting part;
Do not irradiate the filler wire between the groove wall on the same side across the filler wire on the molten pool and the boundary between the molten pool and the filler wire side edge, and on the boundary between the molten pool and the bottom of the front groove A laser device having a laser spot scanning mechanism for irradiating a laser beam to a welded portion by reciprocatingly scanning a laser spot obtained by removing the focus of the laser beam on a substantially U-shaped trajectory passing therethrough is provided. Laser narrow groove multi-layer welding equipment.

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