JP5580788B2 - Laser welding method for thick steel - Google Patents

Description

  The present invention relates to a laser welding method for thick steel materials used in shipbuilding, bridges, heavy electrical fields, and the like, and more particularly, to a laser welding method for thick steel materials capable of stably multilayer laser welding thick steel materials having a plate thickness of 50 mm or more.

  Recently, with the high output and high performance of laser welding equipment, laser welding has been applied to welding of steel materials with a plate thickness of 50 mm or more, particularly in the shipbuilding, bridge and heavy electric fields. Many of these laser welding methods for thick steel materials are laser-arc hybrid welding (for example, Patent Document 1) in which a groove is widely set, or laser welding (for example, filler wire or flux cored wire) (for example, Patent Documents 2 to 7).

  Patent Documents 2 and 8 provide a welding method in which a groove groove having a width of 1/6 and a depth of 1/3 of the plate thickness is provided at a butt portion between base materials, and laser welding is performed using a welding wire (Patent Document). 2) and a welding method (Patent Document 8) in which welding is performed by laser without adding a molten material.

  Further, Patent Document 9 discloses a laser welding method in which a plate-like workpiece is provided with a U-shaped groove and the workpieces are overlapped so that the grooves face each other. Is disclosed, and a through-hole having a rectangular cross-section made of the groove is formed in the overlapped portion between the workpieces. A light guide member having an entrance and an exit for laser light and having a mirror finish inside is inserted into the through hole, and the laser light is guided to the groove bottom. In Patent Document 10, the surface of the I-shaped groove (groove wall surface) is processed to have a surface roughness that allows laser light to be reflected, and the laser light is reflected on the groove wall surface to cause laser light on the groove bottom. In addition, a laser welding method is disclosed in which a filler wire such as a filler wire and metal powder supplied to the groove bottom is melted and laser welding is performed. After welding the groove bottom, a supply position of the filler material is disclosed. Is moved upward, and the inside of the groove is successively welded in multiple layers.

JP 2002-301582 A JP-A 61-17389 JP-A-7-323386 Japanese Patent No. 2711655 Japanese Patent No. 2853800 JP 2010-172941 A JP 2011-5533 A Japanese Patent Laid-Open No. 61-17388 Japanese Patent Publication No. 7-29210 Japanese Examined Patent Publication No. 7-45112

  However, recently, laser welding has been applied to welding of thick steel materials in which the groove width of the joint is extremely small, for example, 6.5 mm or less. However, the techniques of Patent Documents 1 to 8 are all applicable when the groove width is wide. For example, when the groove width is smaller than the diameter of the welding torch or welding wire. It is not applicable. In particular, in Patent Documents 4, 5 and 7, as shown in each drawing, a filler wire supply nozzle is inserted into a groove, and laser welding with a groove width of 6.5 mm or less is performed. Difficult to apply.

  The method of guiding the laser beam to the groove bottom using a light guide member as in Patent Document 9 is that the tip of the light guide member is close to the welded part, and therefore fumes and fine spatters generated during welding are lasers. It adheres to the light exit and tends to accumulate. Therefore, there is a problem that long-time welding cannot be realized. Also in Patent Document 10, fume and spatter generated during welding adhere to the groove wall surface, the groove wall surface processed to a predetermined surface roughness is roughened, and the energy of the laser beam reaching the groove bottom is reduced. However, there is a problem that multilayer welding cannot be stably performed. In this Patent Document 10, regarding the groove width of the I-shaped groove, when welding a material to be welded having a plate thickness of about 70 mm, welding is possible even if the groove width is about 1 to 3 mm. Although described, there is no disclosure of a method for supplying filler material such as filler wire and metal powder, and in practice, stable multilayer welding cannot be realized. In consideration of the attenuation data of the laser light energy described in Patent Document 10, it is estimated that the technique of Patent Document 10 is applied to a material to be welded having a plate thickness of less than 100 mm.

  The present invention has been made in view of such problems, and a laser welding method for a thick steel material capable of stably performing multilayer laser welding of a thick steel material having a plate thickness of 50 mm or more even when the groove width is extremely small. The purpose is to provide.

  A laser welding method for a thick steel material according to the present invention is a laser welding method for a thick steel material in which a pair of thick steel materials having a plate thickness of 50 to 200 mm are butted and laser-welded using the butted portion as a joint, The groove shape of the butt portion is a V-shaped groove or Y-shaped groove having a bottom width of 1.5 to 3.5 mm, the groove depth at the start of welding is X mm, and the groove opening at the start of welding When the width is Ymm, the groove opening width Y at the start of the welding satisfies the following formula with respect to the groove depth X, and a belt-like filler material is used with the wall surface of the groove as a guide. The laser beam is supplied to the bottom, and the bottom is irradiated with a laser beam, and the inside of the groove is multilayer welded. The laser beam has a laser spot diameter of 1.0 to 2.5 mm at the irradiation position. For shrinkage of groove opening width due to welding Ri, characterized in that GMA width of the laser beam irradiated portion is maintained at 1.5 to 3.5 mm.

  In the present invention, for example, the belt-like filler material has a plate thickness of 0.4 to 1.5 mm and a width of 5 to 15 mm.

  In the present invention, in the multilayer laser welding method between thick steel materials, the groove shape of the butt portion between the thick steel materials is a V-shaped groove or Y-shaped groove having a bottom width of 1.5 to 3.5 mm, and welding The width of the groove opening at the start is optimized with respect to the groove depth, and multilayer welding is performed within the groove with a laser beam having an optimum laser spot diameter by defocusing, etc. Due to the shrinkage of the width of the groove opening due to welding, the groove width at the laser beam irradiation site is maintained in the optimum width range, and a belt-like filler material supplied to the groove bottom portion using the wall surface of the groove as a guide is provided. It is possible to melt and stably perform multilayer laser welding.

It is a schematic diagram which shows the laser welding method of the thick steel material which concerns on this invention. It is a figure which shows the test piece in 1st Example of this invention. It is a figure which shows the test piece in 2nd Example of this invention. It is a graph which shows the relationship between the groove depth at the time of welding start, and the width | variety of a groove opening part. It is a figure which shows the test piece in 3rd Example of this invention. It is a figure which shows the test piece and strip | belt-shaped filler metal in 4th Example of this invention, (a) is a front view, (b) is side part sectional drawing.

  The inventors of the present application stably perform multi-layer laser welding even when a groove width is extremely small, for example, 6.5 mm or less when butt welding a thick steel material having a thickness of 50 mm or more, particularly 50 to 200 mm. In order to establish the technology to do, various experiments were examined. And it discovered that the width | variety of a groove opening part decreased gradually with progress of multilayer laser welding. Based on this knowledge, it was found that the groove width at the irradiation position of the laser beam can always be maintained at the optimum width by multilayer laser welding with the groove shape as a V-shaped groove or a Y-shaped groove. completed.

  That is, as shown in FIG. 1, a pair of thick steel materials 1 having a thickness of 50 to 200 mm are butted together, and a V-shaped or Y-shaped groove 10 is provided at the butted portion of the thick steel material 1. The width Wg of the bottom 11 of the groove 10 is 1.5 to 3.5 mm. Then, when the groove depth at the start of welding is X mm and the width of the groove opening at the start of welding is Y mm, the groove opening width Y is expressed by the above formula with respect to the groove depth X. Set to satisfy 1. At the time of laser welding, the belt-like filler material 6 is supplied to the bottom portion 11 with the wall surface 12 of the groove 10 as a guide, and the bottom portion 11 is irradiated with laser light to perform multilayer welding inside the groove 10. If it does so, the width | variety of a groove opening part will shrink | contract with multilayer welding. For example, in the third layer laser welding, the groove bottom 11 is the upper surface of the second layer weld metal, and the width of the groove bottom 11 is 1.5 to 3.5 mm. A belt-like filler material 6 is supplied to the groove bottom 11 and irradiated with a laser beam. At this time, the laser spot diameter of the laser light is controlled by defocusing or the like so that the laser spot diameter at the irradiation position is 1.0 to 2.5 mm. If it does so, in the irradiation part of a laser beam, the filler material 6, the groove bottom part 11, and a groove wall part will fuse | melt, and it will be in the state fuse | melted mutually. In this state, the irradiated portion of the laser beam moves to cool the molten metal and solidify to form a third layer weld metal. In the process of solidification of the molten metal, the temperature of the weld metal decreases, and this temperature decrease causes thermal shrinkage of the weld metal. Therefore, the groove wall surface 12 is pulled by the weld metal in the direction in which the width of the groove opening is reduced. And the width | variety of the upper surface of the 3rd-layer weld metal is maintained in the range of 1.5 to 3.5 mm. In the present invention, due to the shrinkage of the width of the groove opening, the groove width at the laser light irradiation site can be maintained at 1.5 to 3.5 mm during laser welding.

  First, as shown in FIG. 2, the inventors of the present application, for example, arrange a pair of SM400 steel plates having a width of 48 mm, a thickness of 32 mm, and a length of 300 mm, and set the groove shape of the butt portion to the groove depth. Is a Y-shaped groove 20a having a width of 20 mm, and a dummy wall 21 having an upper opening width Wf of 3.8 to 5.3 mm is provided on the top of the test piece 20, and the groove 21 is formed using the wall surface 21b of the dummy wall 21 as a guide. The optimum width at the laser beam irradiation position was derived by supplying a belt-like filler material to the bottom and performing laser welding. That is, the groove width Wg of the Y-shaped groove 20a is changed within a range of 1 to 5 mm, and both the supplied filler material and the groove wall part are sufficiently melted to generate welding defects such as poor fusion. In order to prevent this, it has been found that the groove width at the laser beam irradiation position may be 1.5 to 3.5 mm.

  Next, the inventors of the present application examined conditions for stably performing multilayer laser welding up to the final layer. That is, as shown in FIG. 3, a pair of SM400 steel plates having a width of 30 mm, a thickness of 80 to 230 mm, and a length of 300 mm are arranged to face each other, and a V-shaped groove 30 having a bottom width Wg of 2.5 mm is provided at the abutting portion. The relationship between the groove depth D and the groove opening width Wf at the start of welding was examined using the test piece 3. And it is found that the groove width at the irradiation position of the laser beam can be maintained at 1.5 to 3.5 mm if the width of the groove opening at the start of welding satisfies a predetermined relationship with the groove depth. did. That is, by irradiating the groove bottom portion with laser light, the filler material supplied to the groove bottom portion and the steel material in the laser light irradiation region are melted and integrated, so that the width of the groove opening portion is obtained. Gradually contracts. Therefore, by providing the groove shape in a V-shape or Y-shape that gradually becomes wider toward the groove opening, the groove width at the laser light irradiation position can be maintained within an appropriate range. The inventors of the present application have found that the width Y of the groove opening at the start of welding only needs to satisfy Equation 1 with respect to the groove depth X by examining the test piece shown in FIG. That is, when the width Y of the groove opening at the start of welding is less than the lower limit value of Equation 1, the shrinkage increases along with multilayer laser welding, and the width of the groove opening interferes with the laser beam. It becomes extremely small, and a predetermined laser output cannot be obtained, so that the final layer cannot be stably welded. On the other hand, when the width Y of the groove opening at the start of welding exceeds the upper limit of Equation 1, the groove width at the laser beam irradiation position becomes excessive with multi-layer laser welding, and the filler material and the groove wall Both of them cannot be melted sufficiently, and poor fusion tends to occur.

  In the present invention, since the belt-like filler material is supplied using the wall surface of the groove as a guide, multilayer laser welding can be stably performed. That is, the belt-like filler material can be easily supplied to a narrow groove, and can be easily deformed in the thickness direction, but hardly deformed in the width direction. Therefore, if it supplies along a groove wall surface, it can supply to the irradiation position of a laser beam correctly and stably also from the exterior of a groove. Therefore, it is not necessary to insert a supply guide such as a filler wire as used in the prior art, and the groove width can be made extremely small.

  Furthermore, in the present invention, the laser beam irradiated to the welded portion is controlled by defocusing or the like so that the laser spot diameter at the irradiation position is 1.0 to 2.5 mm. In addition, both the groove wall portion and the groove wall portion can be sufficiently melted, and an integrated good weld metal can be obtained. In the present invention, it is preferable to use a light source that emits laser light having a different focal length depending on the plate thickness.

  In the present invention, it is preferable that the cross-sectional dimensions of the belt-shaped filler metal are a plate thickness of 0.4 to 1.5 mm and a width of 5 to 15 mm. It is suitable at the point which obtains a weld metal.

  The effects of the groove shape (the width of the groove bottom at the start of welding, the width of the groove opening) and the like in the present invention will be described below with reference to the following examples.

(First Example) Appropriate groove width selection welding test First, in narrow groove laser welding using a belt-like filler material, a width of 48 mm, a thickness of 32 mm, and a length are selected in order to select an appropriate width of the groove bottom. , A pair of 300 mm SM400 steel plates are butted against each other, and as shown in FIG. 2, the groove shape of the butted portion is a Y-shaped groove 20a having a groove depth of 20 mm, and a groove width Wg of 1 to 5 mm. It changed to the range and used for the test piece 20 of the Example and the comparative example. For each test piece, a dummy wall having a height Hd of 60 mm at the top of the Y-shaped groove and a width Wf of the upper opening of 3.8 to 5.3 mm is used to make a welding test simulating an extremely thick material. 21. Using a wall surface 21b of the dummy wall 21 as a guide, a belt-like filler material made of low carbon steel having a thickness of 0.9 mm and a width of 13 mm is continuously supplied to the bottom of the Y-shaped groove, and a shielding gas is supplied. While supplying, laser light was irradiated from a fiber laser, and multilayer laser welding was performed under the welding conditions shown in Table 1. As the filler material, one having a chemical component composition corresponding to YGW16 defined in JIS Z3312 (2009) was used, and as the fiber laser, a focusing lens having a lens diameter of 23 mm and a focal length of 500 mm was used. In addition, the focus position shown in Table 1 indicates the position in the depth direction of the focus when the direction toward the groove opening is positive with respect to the groove bottom of each test piece.

  About the test piece of various groove width Wg, after welding, the cross section observation of the laser welding part was performed, and the penetration state of the welding part was investigated. Table 2 below shows the penetration state of the welds and the evaluation results for the test pieces of each Example and Comparative Example.

  As shown in Table 2, an example No. in which the groove width Wg of the Y-shaped groove is 1.5 to 3.5 mm. In Nos. 2 to 6, no poor fusion occurred, and the welded section had good penetration. On the other hand, comparative example No. whose groove width Wg is less than 1.5 mm. In No. 1, the output of the laser beam was dominant in the melting of the filler material, and the melting of the bottom of the groove was insufficient, resulting in poor fusion. On the other hand, Comparative Example No. In Nos. 7 to 9, since the groove width Wg exceeded 3.5 mm, the groove wall portion was insufficiently melted, resulting in poor fusion.

(2nd Example) Groove opening width selection welding test Next, in narrow groove laser welding using a filler material, an appropriate groove opening of a V-shaped groove or a Y-shaped groove at the start of welding. In order to select the width, a pair of SM400 steel plates having a width of 30 mm, a thickness of 80 to 230 mm, and a length of 300 mm are abutted against each other, and as shown in FIG. .5 mm V-shaped groove 30, groove depth D is 50 mm, 100 mm, 150 mm, and 200 mm, and for each groove depth D, the width Wf of the groove opening is changed variously to form test piece 3. Provided. Then, using the wall surface 31 of each groove as a guide, a belt-like filler material made of low carbon steel having a thickness of 0.9 mm and a width of 13 mm is continuously supplied to the bottom of the V-shaped groove 30 and also a shielding gas is supplied. The laser beam was irradiated from the fiber laser while performing multilayer laser welding under the welding conditions shown in Table 3. In this embodiment, the fiber laser has a focal length corresponding to the groove depth D so that laser light having a high energy density is irradiated to the groove bottom even when the groove depth D is deep. Two types of focusing lenses (a focusing lens having a lens diameter of 23 mm and a focal length of 500 mm and a focusing lens having a lens diameter of 23 mm and a focal length of 800 mm) were used. Moreover, as a filler material, what has a chemical component composition corresponded to YGW16 prescribed | regulated to JISZ3312 (2009) was used. In addition, the focus position shown in Table 3 shows the position in the depth direction of the focus when the direction toward the groove opening is positive with respect to the groove bottom of each test piece.

  For various groove depths D, is it possible to stably weld up to the final layer when multi-layer laser welding is performed on each test piece in which the width Wf of the groove opening at the start of welding is variously changed? Was investigated by the bead formation state during welding, and the penetration state of the laser weld and the presence or absence of welding defects were examined by a cross-sectional macro test. Table 4 below shows whether the test pieces of each Example and Comparative Example are weldable, the welded state of the welded portion, and the presence or absence of welding defects. Moreover, in each groove depth D and width Wf of a groove opening part, what was able to be welded stably is shown as (circle), and what cannot weld or the fusion defect generate | occur | produced in the welding part is shown in FIG.

  As shown in Table 4 and FIG. 4, for each groove depth D, there may be a width Wf of the groove opening at the start of welding that can be stably welded to the final layer and a good weld is obtained. confirmed. That is, when the width Wf of the groove opening at the start of welding is smaller than the appropriate range, the groove opening width shrinks due to the multi-layer welding when welding at the groove bottom or when welding the intermediate layer. The tip width was insufficient, and the laser beam interfered with the upper surface of the groove, making welding impossible. On the other hand, when the width Wf of the groove opening at the start of welding is larger than the appropriate range, poor fusion occurred in the groove wall. In contrast, Example No. 12 to 15, Example No. 18-20, Example No. 24 to 26, Example No. 31 to 33 and Example No. In Nos. 37 to 39, since the width of the groove opening at the start of welding is within the appropriate range, the width of the groove opening gradually decreases due to shrinkage as multilayer laser welding proceeds. While maintaining the optimum groove width at the laser beam irradiation position where welding proceeds, welding was possible up to the final layer.

  As shown in FIG. 4, when the groove depth is X mm and the groove opening width at the start of welding is Ymm, the groove opening width Y at the start of welding is relative to the groove depth X. By satisfying Formula 1 above, in multi-layer laser welding with a small groove width, it is possible to stably weld to the final layer, and a good weld is obtained.

(Third embodiment) Confirmation test of appropriate laser spot diameter Next, in order to confirm the appropriate laser spot diameter of the laser beam to be irradiated for the main groove bottom width Wg in the present invention, a width of 25 mm, a thickness of 32 mm, A pair of SM400 steel plates with a length of 300 mm are arranged to face each other, and as shown in FIG. 5, the groove shape of the butt portion is a Y-shaped groove 40a with a groove depth of 20 mm, and a groove width Wg is 2. It used for the test piece 40 which was 0 mm, 2.5 mm, and 3.0 mm. Then, each test piece 40, as shown in FIG. 5, by changing the focal position of the laser beam, by changing the laser spot diameter d _l of the groove bottom, thickness 0.4 mm, a width of 10mm low carbon While continuously feeding the steel strip-like filler metal to the bottom of the Y-shaped groove and irradiating laser light from the fiber laser while supplying the shielding gas, multilayer laser welding is performed under the welding conditions shown in Table 5. Carried out. Also in this example, the focal position shown in Table 5 indicates the position in the depth direction of the focal point when the direction toward the groove opening is positive with respect to the groove bottom of each test piece. As the filler material, one having a chemical component composition corresponding to YGW16 defined in JIS Z3312 (2009) was used, and as the fiber laser, a focusing lens having a lens diameter of 23 mm and a focal length of 500 mm was used.

For respective holders destination width Wg, each test piece having a laser spot diameter d _l changed variously in the bottom of the groove, after welding, performing sectional observation of the laser weld, a state penetration of the filler material in the groove walls investigated. Table 6 below shows the penetration state and evaluation of the filler material in the groove wall for each test piece.

As shown in Table 6, when the laser spot diameter d _l of the groove bottom is less than 1.0 mm, although the filler metal melts, the spot diameter is insufficient, penetration is insufficient to groove wall, A poor fusion occurred. On the other hand, when the laser spot diameter d _l of the groove bottom is more than 2.5 mm, by the laser density is insufficient, the melting of the filler material and the groove wall becomes insufficient, failure occurred fusion. In contrast, for specimens laser spot diameter d _l is 1.0 to 2.5mm in the bottom of the groove, the melting of the filler material and the groove wall is sufficiently performed, portions is good weld Obtained.

(Fourth embodiment) Confirmation test for appropriate size of filler metal Next, in order to confirm the preferred dimensions of the belt-like filler material supplied to the groove bottom, laser welding was performed using various sizes of filler material. went. In this embodiment, as shown in FIG. 6 (a), a pair of SM400 steel materials having a width of 30 mm, a height of 60 mm, and a length of 300 mm are butted together, and a groove depth of 50 mm and a bottom width Wg are arranged at the butted portion. Was provided with a V-shaped groove 50 having a width Wf of 4.5 mm and a groove opening width Wf of 4.5 mm at the start of welding. And as shown in FIG.6 (b), it uses the groove wall 51 as a guide, and is strip | belt-shaped which consists of low carbon steel which has various thickness (0.3 to 1.5 mm) and width (3 to 20 mm). While the melt material 6 was continuously supplied to the bottom of the V-shaped groove and the shield gas was supplied, laser light was irradiated from the fiber laser, and multilayer laser welding was performed under the welding conditions shown in Table 7. As the filler material 6, a material having a chemical component composition corresponding to YGW16 defined in JIS Z3312 (2009) was used, and as the fiber laser, a converging lens having a lens diameter of 23 mm and a focal length of 500 mm was used. In the case of using strip-shaped filler metal having a plate thickness of 0.3 mm and 0.4 mm, the supply rate of the filler material is 9 m / min, and the strip-shaped filler metal having a plate thickness of 0.7 to 2.0 mm is used. In the case of using a filler, the supply rate of the filler was 6 m / min. The thickness and width of each filler material are shown in Table 8 below. And in multilayer laser welding using strip filler metal of various dimensions, the following can be obtained, where ○ can be stably welded and a good weld is obtained, and x is a case where a good weld is not obtained. Table 8 shows. The focal position shown in Table 7 indicates the position in the depth direction of the focal point when the direction toward the groove opening is positive with respect to the groove bottom of each test piece.

  As shown in Table 8, when the thickness of the belt-like filler material is less than 0.4 mm, the filler material is not easily fed due to insufficient rigidity of the filler material. Further, when the plate width of the filler material is less than 5 mm, the tip of the filler material is likely to fluctuate in the plate thickness direction, making it difficult to stably supply the laser spot position. On the other hand, when the plate thickness of the filler material exceeds 1.5 mm, the feeding of the filler material tends to be unstable, and when the plate width exceeds 15 mm, the weld metal is less likely to be formed in the center of the groove, It became a single-walled bead, and the filler material became insufficiently melted due to insufficient laser power, which caused poor penetration. On the other hand, when the plate thickness of the filler material was 0.4 to 1.5 mm and the plate width was 5 to 15 mm, multilayer laser welding could be stably performed, and a good weld was obtained.

(Fifth Example) Narrow Gap Laser Welding Test on Extra Thick Steel Sheet A narrow gap laser welding test was conducted on an extra thick steel sheet based on the results obtained in the first to fourth examples. A pair of SM400 steel plates having a width of 30 mm, a thickness of 230 mm, and a length of 300 mm are arranged to face each other. As shown in FIG. 3, the groove shape of the butt portion is a bottom width Wg of 2.5 mm, and a groove opening at the start of welding. A V-shaped groove 30 having a width Wf of 6 mm and a groove depth D of 190 mm was used. As the filler material, a belt-like filler material having a chemical composition corresponding to YGW16 defined in JIS Z3312 (2009) and made of low carbon steel having a thickness of 0.9 mm and a width of 10 mm was used. Table 9 shows the belt-like filler metal continuously supplied to the bottom of the V-shaped groove 30 with the groove wall surface 31 as a guide, and irradiated with laser light from a fiber laser while supplying a shielding gas. Multi-layer laser welding was performed under welding conditions. As the fiber laser, a focusing lens having a lens diameter of 23 mm and a focal length of 800 mm was used. The shield gas was supplied into the groove from the outside of the groove.

  As a result of this welding test, as multi-layer laser welding progresses, the groove width gradually decreases due to shrinkage, and the groove width at the laser beam irradiation point where welding always proceeds is 2.5 to 3. The range of 0 mm was maintained, welding proceeded stably, and multilayer laser welding was completed in 20 passes to the final layer.

  After welding, the obtained welded portion was sliced to a width of 50 mm at a cross section including the weld line, and a radiation transmission test was performed from the side surface direction of the welded portion. As a result, no weld defect with a diameter exceeding 1 mm was observed, and a sound weld was obtained.

  As described above, according to the present invention, when a steel plate having a thickness of 50 mm or more is subjected to multi-layer laser welding with a very narrow groove width, highly efficient and stable multi-layer laser welding can be realized. Therefore, distortion due to welding is also suppressed. That is, according to the present invention, there are few fluctuation factors in welding construction, and for example, it is possible to apply to stable multilayer laser welding in a welding construction technique by remote control that is required for welding of nuclear equipment. .

1: thick steel material, 10: groove, 11: (groove) bottom, 12: wall surface, 20, 3, 4, 5: test piece, 21: dummy wall, 20a, 21a, 30, 40, 50: groove 20b, 21b, 31, 41, 51: (groove) wall surface, 6: (band-like) filler material

Claims (2)

It is a laser welding method of a thick steel material in which a pair of thick steel materials having a plate thickness of 50 to 200 mm are arranged to face each other, and this abutting portion is laser welded as a joint,
The groove shape of the butt portion is a V-shaped groove or Y-shaped groove having a bottom width of 1.5 to 3.5 mm, the groove depth at the start of welding is X mm, and the groove opening at the start of welding When the width of Y is Ymm, the groove opening width Y at the start of welding satisfies the following mathematical formula with respect to the groove depth X:
While supplying a belt-like filler material to the bottom portion using the groove wall surface as a guide, irradiating the bottom portion with a laser beam, multilayer welding the inside of the groove,
The laser beam has a laser spot diameter of 1.0 to 2.5 mm at the irradiation position,
A laser welding method for a thick steel material, characterized in that a groove width at a laser beam irradiation site is maintained at 1.5 to 3.5 mm by shrinkage of a groove opening width accompanying multilayer welding.

2. The method of laser welding a thick steel material according to claim 1, wherein the belt-like filler material has a plate thickness of 0.4 to 1.5 mm and a width of 5 to 15 mm.

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