JP5422030B2 - Steel plate laser welding method and laser welding apparatus - Google Patents

Description

The present invention relates to a laser welding method and a laser welding apparatus for a butt portion of steel plates.

  In general, in process lines (lines for pickling, annealing, rolling, rewinding, inspection, etc.) for processing steel sheets such as hot-rolled steel sheets and cold-rolled steel sheets, steel sheets are continuously supplied and supplied. A continuous line is often used for continuously processing.

  In order to continuously supply the steel plate to be processed to such a continuous line that can be processed continuously, the steel plate can be cut without interruption by butt welding the steel plate and the steel plate in the upstream process of this continuous line. It is necessary to supply to a continuous line.

  As a general welding device arranged in the upstream process of this continuous line, it is a steel plate that follows the end surface of a welding material that is a preceding steel plate (hereinafter referred to as a preceding welding material) and a preceding welding material. There is a welding apparatus that welds and connects an end surface of a welding material (hereinafter referred to as a subsequent welding material). Further, when the materials to be welded are high-carbon steel and high-tensile steel plate, a laser welding apparatus that uses laser light for the purpose of improving productivity and stabilizing quality is often used. However, in such laser welding of high-carbon steel and high-tensile steel plate, weld cracks often occur with the generation of martensite inside the material to be welded by rapid cooling after welding. Therefore, in order to reduce the degree of martensite generation and reduce weld cracking, it has been necessary to reduce the rapid temperature change of the workpiece.

  For example, in Patent Document 1, a carriage that travels in synchronization with the movement of a welding torch of a welding machine along a butt weld portion of a steel plate with opposed end faces for laser welding, and is disposed rotatably on the carriage. A plate-type joint comprising a rotary backing member configured to back the welded portion from below as the carriage travels, and a coil for preheating the butted portion and its vicinity prior to the welding torch as the carriage travels A welding device is described.

  Patent Document 2 discloses a laser welding method for a high-tensile steel sheet that prevents the weld metal from hardening and forms a weld with good formability by heating to a predetermined temperature after the laser beam passes. Yes.

Japanese Patent Laid-Open No. 6-312285 JP 2004-209497 A

  However, the plate joining apparatus described in Patent Document 1 has the following problems. That is, a laser welding apparatus used for a continuous line in which a steel plate is continuously processed accurately welds the end of the preceding welded material and the end of the subsequent welded material. Then, the end of the workpiece to be welded is cut with a cutting device built in the plate joint welding device. At this time, the end portion that forms the abutting portion is not a flat surface, but may cause minute variations in shape, and burr may occur. When induction heating and laser welding are performed in such a state that the shape of the end portion varies or burr is generated, the shape of the welded portion such as step welding or hole welding is generated due to a change in the butt gap at the plate end. There was a problem.

  Further, in the plate joint welding apparatus described in Patent Document 1, when the plate thickness of the preceding welded material is different from the plate thickness of the subsequent welded material, a step is generated between the base material and the welded portion. For this reason, when the material to be welded is supplied to a continuous line, which is a subsequent process, and repeatedly bent in a state where this level difference occurs, there is a problem that bending stress acts locally on the welded portion and the welded portion breaks. It was.

  Furthermore, in the plate welding apparatus described in Patent Document 1, magnetic flux is generated in the thickness direction of the material to be welded. Therefore, the amount of penetrating magnetic flux varies depending on the contact state between the end faces of the material to be welded, and stable and uniform heating is performed. There is a problem that is difficult.

  By the way, before a steel plate is provided to a continuous line, it is generally performed to supply spray water to the steel plate surface in order to remove foreign matters such as scale powder on the steel plate surface. Or it may pass through, spraying spray water on the roll surface so that foreign materials, such as scale powder on the steel plate surface, may not adhere to the roll. Even when spray water is not supplied, cooling water may remain on the steel sheet when the steel sheet has undergone a water cooling step or the like. Therefore, when performing the above-described welding of the steel plates, the butted portions of the steel plate end portions are often wet with cleaning water or cooling water. When welding is performed by irradiating a laser to the butt portion where moisture remains, water vapor is generated. This water vapor blows away the molten metal to form a defect in which the surface of the weld is greatly depressed, or remains in the weld metal to form a blowhole defect. A weld including such a defect causes a decrease in bonding strength. As a result, the steel sheet breaks from the welded part in the middle of the continuous line, and the production line is stopped. It is necessary to recover the stopped production line by taking a predetermined measure. Such line stoppage and restoration are problems to be avoided from the viewpoint of manufacturing efficiency.

  On the other hand, when washing with water is not performed because laser welding is used, scale powder or the like remains on the steel sheet, and this may cause scratches or the like generated on the steel sheet surface by subsequent processing.

  In the conventional techniques including the invention described in Patent Document 2 and the like, although laser welding is applied to a steel sheet, the above problem is not solved and the demand for a solution is still high.

  This invention is made | formed in view of the said subject, and provides the laser welding method of the steel plate which can reduce the shape defect of a to-be-welded material welding part, and can obtain sufficient joint strength, and its apparatus. Let it be an issue.

  The present invention will be described below.

  The invention according to claim 1 is a method of laser welding a steel plate in which end faces of a plurality of steel plates to which water has adhered are butted together, and the butted portions of the butted steel plates are irradiated with a laser beam to weld the butted portions. A cutting process for forming the end face of the material into a shape suitable for matching, a butting process for matching the end faces formed by the cutting process, a first heating process for heating the butted portion and removing water, and a first heating process The said subject is solved by providing the laser welding method of the steel plate provided with the laser welding process which welds the butt | matching part heated by laser with a laser.

  A second aspect of the present invention is the laser welding method for a steel sheet according to the first aspect, wherein the first heating step is performed by a coil that generates a magnetic flux penetrating in parallel with the surface of the steel sheet. .

  According to a third aspect of the present invention, in the laser welding method for a steel sheet according to the first aspect, the butt portion is further pressed from the vertical direction of the plate thickness between the butt step and the first heating step. It is characterized by comprising a shaping step of shaping the front and back surfaces of the steel plate of the part.

  According to a fourth aspect of the present invention, in the laser welding method for a steel plate according to the first aspect, the second heating step for heating the welded portion of the steel plate welded in the laser welding step, and the heating by the second heating step. And a pressurizing step for shaping the welded portion by pressing the welded portion from above and below the plate thickness.

  According to a fifth aspect of the present invention, in the laser welding method for a steel sheet according to the fourth aspect, the second heating step is performed by heating with a coil that generates a magnetic flux penetrating in parallel with the surface of the steel sheet. .

  The invention according to claim 6 is characterized in that the heating by the second heating step in the laser welding method of the steel sheet according to claim 4 is performed simultaneously with the laser welding step.

  Invention of Claim 7 is a 1st heating process in the laser welding method of the steel plate in any one of Claims 1-6, All the temperature of the steel plate front and back of this butt | matching part by heating of a butt | matching part It reaches 200 ° C. or higher.

  Invention of Claim 8 is arrange | positioned in the downstream of the apparatus which contacts water with a steel plate, but the end surfaces of several steel plates are faced | matched, a laser beam is irradiated to the butt | matching part of the butt | matched steel plate, and a butt part is welded A laser welding apparatus for a steel plate, which is heated by a cutting means for forming the end face of the steel plate into a shape suitable for butting, a first heating means for heating the butted portion to remove water, and a first heating means. The above-mentioned problems are solved by providing a laser welding apparatus for a steel plate provided with laser welding means for welding the butted portion with a laser.

  A ninth aspect of the present invention is the laser welding apparatus for a steel sheet according to the eighth aspect, wherein the first heating means is a coil that generates a magnetic flux penetrating in parallel with the surface of the steel sheet.

  The invention according to claim 10 is the steel plate of the butt portion by pressing the butt portion from the vertical direction of the plate thickness before the butt portion is welded by the laser welding means in the laser welding apparatus of the steel plate according to claim 8. A shaping means for shaping the front and back surfaces is provided.

  According to an eleventh aspect of the present invention, there is provided a second heating means for heating a welded portion of the steel plate welded by the laser welding means in the laser welding apparatus for the steel sheet according to the eighth aspect, and heating by the second heating means. And pressurizing means for shaping the welded portion by pressing the welded portion from above and below the plate thickness.

  According to a twelfth aspect of the present invention, in the laser welding apparatus for a steel sheet according to the eleventh aspect, the second heating means is a coil that generates a magnetic flux penetrating in parallel with the surface of the steel sheet.

  According to a thirteenth aspect of the present invention, the welding carriage having the shaping means, the first heating means, the laser welding means, the second heating means, and the pressurizing means in the laser welding apparatus for the steel sheet according to the eleventh aspect can run. It is characterized by providing in.

  According to a fourteenth aspect of the present invention, the laser welding means in the steel plate laser welding apparatus according to any one of the eighth to thirteenth aspects comprises a plurality of fiber-like or disk-like crystals arranged in parallel. A laser beam oscillator and an optical fiber for transmitting laser light emitted from the oscillator are provided.

  According to the laser welding apparatus and the laser welding method of the present invention, it is possible to reduce the shape defect of the welded material welded portion and further reduce the weld cracking of the welded material. Further, it is possible to prevent the welded portion from being broken during the continuous process, thereby preventing the production line from being stopped and improving the productivity.

1 is a perspective view of a laser welding apparatus according to a first embodiment of the present invention. It is sectional drawing which showed the cross section of the welding carriage of the laser welding apparatus which concerns on 1st Embodiment. It is explanatory drawing of a guillotine shear which cut | disconnects a to-be-welded material. It is explanatory drawing explaining the heating effect | action of the induction heating head for pre-heat treatment, and the induction heating head for post-heat treatment. It is explanatory drawing which shows the cross section seen from the plate | board thickness direction which shows the state which faced the to-be-welded material cut | disconnected by the guillotine shear. It is a top view which shows the state which faced the to-be-welded material after cut | disconnecting with a guillotine shear. It is sectional drawing of the to-be-welded material pressed with the shaping roll. It is sectional drawing of the welding part at the time of welding a to-be-welded material without using a filler wire. It is sectional drawing of the welding part at the time of welding a to-be-welded material using a filler wire. It is sectional drawing of the to-be-welded material pressed with the process roll. It is sectional drawing of the to-be-welded material pressed with the process roll, when the thickness of to-be-welded material differs. It is a perspective view of the laser welding apparatus which concerns on 3rd Embodiment. It is a figure which shows the weld part cross section in an Example. It is a figure which shows the weld part cross section in an Example.

  EMBODIMENT OF THE INVENTION The form for implementing this invention is demonstrated referring drawings below.

<First Embodiment>
FIG. 1 is a perspective view of a laser welding apparatus according to the first embodiment of the present invention.

  As shown in FIG. 1, the laser welding apparatus 1 according to the first embodiment includes a clamp 2 that holds a plate-shaped workpiece, and a workpiece to be welded that is conveyed in the X direction while moving in the Y direction in FIG. 1. A welding carriage 3 for welding materials and a carbon dioxide laser oscillator 4 are provided.

  FIG. 2 is a cross-sectional view showing a cross section of the welding carriage 3 of the laser welding apparatus 1 according to the first embodiment.

  As shown in FIG. 2, the welding carriage 3 is formed by connecting the guillotine shears 5 a and 5 b that are means for cutting both ends of the material to be conveyed and the abutted portion of the material to be welded held by the clamp 2. Shaping rolls 6a and 6b which are means for shaping by pressing from above and below in the thickness direction, and an induction heating head for preheat treatment which is a first heating means for induction heating the work to be welded shaped by the shaping rolls 6a and 6b 7, a processing head 9 which is means for welding the welded material heated by the induction heating head 7 for pre-heat treatment by irradiating the welded material, and a welding head disposed immediately below the processing head 9, and welded A back low that supports the end surfaces of the preceding and succeeding welded materials from the lower surface and prevents laser light leaking from the lower surface of the welded material being welded from being exposed to the outside. 8 and a post-heat treatment induction heating head 10 which is a second heating means for induction heating the workpiece welded by the processing head 9 and the welded portion welded by the processing head 9 are sandwiched from above and below the plate thickness. And pressurizing rolls 11a and 11b which are pressurizing means for shaping.

  The welding carriage 3 is disposed so as to sandwich the material to be welded from above and below, and moves in the forward direction of the arrow Y or in the reverse direction of the arrow Y via a ball screw (not shown) whose rotational speed is controlled by a servo motor. To do. In addition, the guillotine shears 5a and 5b, the shaping rolls 6a and 6b, the preheating induction heating head 7, the back roll 8, the processing head 9, the post-heating induction heating head 10, and the pressure rolls 11a and 11b are spaced at predetermined intervals. It is provided and arranged on a straight line in the Y direction.

  FIG. 3 is an explanatory diagram of guillotine shears 5a and 5b for cutting a material to be welded.

  As shown in FIG. 3, the clamp 2 includes a front clamp 2F that clamps the preceding workpiece 100a and a rear clamp 2R that clamps the trailing workpiece 100b. The front clamp 2F includes a front clamp lower part 2Fa, a front clamp upper part 2Fb, and a front clamp cylinder 2Fc that drives the front clamp upper part 2Fb in the vertical direction. Similarly, the rear clamp 2R includes a rear clamp lower part 2Ra, a rear clamp upper part 2Rb, and a rear clamp cylinder 2Rc that drives the rear clamp upper part 2Rb in the vertical direction.

  As shown in FIG. 3, the guillotine shear 5 includes a lower shear blade 5a, an upper shear blade 5b, and a cylinder 5c that drives the upper shear blade 5b in the vertical direction. The guillotine shear 5 enters or retracts between the front clamp 2F and the rear clamp 2R as the welding carriage 3 moves.

  FIG. 4 is an explanatory diagram for explaining the heating action of the preheating induction heating head 7 and the post-heating induction heating head 10. Since the post-heat treatment induction heating head 10 has the same configuration as the pre-heat treatment induction heating head 7, only the pre-heat treatment induction heating head 7 will be described here.

  As shown in FIG. 4, the preheating heat induction head 7 includes an iron core 7a and a coil 7b wound around the iron core 7a. Then, a current is supplied to the coil 7b from a power source (not shown) to generate a magnetic flux (alternating magnetic flux), and this magnetic flux is passed through the welded materials 100a and 100b, thereby generating an eddy current in the welded materials 100a and 100b. Induction and Joule heat is generated by this eddy current to heat the materials to be welded 100a and 100b.

  Here, the magnetic flux generated by the iron core 7a and the coil 7b of the preheating induction heating head 7 is perpendicular to the plate thickness direction of the workpieces 100a and 100b as shown in FIG. The welded materials 100a and 100b are penetrated in parallel to the surfaces of the materials 100a and 100b. Therefore, the magnetic flux penetrating through the materials to be welded 100a and 100b regardless of the contact / non-contact state in the plate width direction of the butted end surfaces of the materials to be welded 100a, that is, the presence or absence of a gap between the opposite end surfaces of the materials to be welded. The amount is about the same in the plate width direction. Thereby, the induction heating head 7 for pre-heat treatment and the induction heating head 10 for post-heat treatment uniformly heat and heat the butted portions (welded portions) of the materials to be welded 100a and 100b. It can be carried out. In addition, although the case where the induction heating head 7 for preheat treatment is provided below the material to be welded is shown in FIG. 4, the present invention is not limited to this and may be provided above the material to be welded.

  The degree of heating by the preheating induction heating head 7 depends on the degree of water washing in the upstream process, the thickness of the material to be welded, the positional relationship of the preheating induction heating head 7 with the material to be welded, etc. And a retention time is employed. Therefore, it is not particularly limited. Among them, moisture can be removed reliably, and from the viewpoint of manufacturing efficiency and energy efficiency, the temperatures of the front and back surfaces of the welded material in the abutted portions are both 200 ° C. or higher, and this is for 1 second. The heating maintained above is preferable. Thereby, it is possible to appropriately maintain the production efficiency without consuming more energy than necessary.

  In addition, as shown in FIG. 2, the back roll 8 is disposed directly below the processing head 9. The back roll 8 supports the end surfaces of the workpieces 100a and 100b being welded from the lower surface to improve the butt accuracy of the workpieces 100a and 100b, and leaks from the lower surfaces of the workpieces 100a and 100b being welded. This prevents the laser beam to be irradiated from the outside.

  As shown in FIG. 2, the shaping roll 6 includes a lower shaping roll 6a, an upper shaping roll 6b, and a cylinder 6c (not shown) that drives the upper shaping roll 6b in the vertical direction. The lower shaping roll 6a and the upper shaping roll 6b are linearly arranged up and down, and the vertical distance between the lower shaping roll 6a and the upper shaping roll 6b can be adjusted by the cylinder 6c. The lower shaping roll 6a and the upper shaping roll 6b each have a structure that rotates around a support shaft (not shown).

  As shown in FIG. 2, the pressure roll 11 includes a lower pressure roll 11a, an upper pressure roll 11b, and a cylinder 11c (not shown) that drives the upper pressure roll 11b in the vertical direction. . The lower pressure roll 11a and the upper pressure roll 11b are vertically arranged in a straight line, and the vertical distance between the lower pressure roll 11a and the upper pressure roll 11b is adjusted by the cylinder 11c. Each of the lower pressure roll 11a and the upper pressure roll 11b has a structure that rotates around a support shaft (not shown).

  Next, the operation of the laser welding apparatus 1 according to the first embodiment will be described with reference to the drawings.

  First, the preceding workpiece 100a is conveyed into the welding carriage 3 of the laser welding apparatus 1 in the direction indicated by the arrow X in FIG. Thereafter, the succeeding workpiece 100b is transported into the welding carriage 3 of the laser welding apparatus 1 with a predetermined distance from the tail end of the transported preceding workpiece 100a.

  Then, as shown in FIG. 3, the leading workpiece 100a transported into the welding carriage 3 is guided at the tail end of the leading workpiece 100a into the guillotine shear 5 and stops at the position shown in FIG. Similarly, the subsequent welded material 100b conveyed into the welding carriage 3 is similarly guided at the tip of the subsequent welded material 100b into the guillotine shear 5 and stopped at the position shown in FIG.

  Thereafter, the clamps 2F and 2R fix the preceding welded material 100a and the subsequent welded material 100b. Specifically, the front clamp upper portion 2Fb is lowered by the power of the front clamp cylinder 2Fc, and is fixed by sandwiching the preceding workpiece 100a with the front clamp lower portion 2Fa. Similarly, the rear clamp upper part 2Rb is lowered by the power of the rear clamp cylinder 2Rc, and is fixed by sandwiching the subsequent welding material 100b with the rear clamp lower part 2Ra.

  Then, the upper shear blade 5b of the guillotine shaft 5 built in the welding carriage 3 is lowered by the power of the cylinder 5c and is sandwiched between the lower shear blade 5a, whereby the preceding welded material 100a and the subsequent welded material. The opposite ends of 100b are cut simultaneously (cutting step). Thereby, the cross section of the preceding welding material 100a and the cross section of the subsequent welding material 100b can be made substantially parallel, and welding can be facilitated.

  Next, the guillotine shear 5 of the laser welding apparatus 1 raises the upper shear blade 5b. Then, the rear clamp 2R restraining the succeeding workpiece 100b is moved toward the front clamp 2F restraining the preceding workpiece 100a by the blade width W of the upper shear blade 5b. As a result, the tail end of the preceding workpiece 100a and the leading end of the subsequent workpiece 100b are abutted (butting step).

  FIG. 5 is a cross-sectional view showing a cross section of the preceding welded material 100a and the subsequent welded material 100b cut by the guillotine shear 5 when viewed from the plate thickness direction, and FIG. It is the top view which showed the state which faced the welding materials 100a and 100b.

  As shown in FIG. 5, after cutting with the guillotine shear 5, when the end surfaces of the preceding welded material 100 a and the subsequent welded material 100 b are brought into contact with each other, a minute shape variation or burr occurs. There is. Furthermore, as shown in FIG. 6, a gap may partially occur in the butted portion of the workpieces 100a and 100b.

  When the preceding welded material 100a and the subsequent welded material 100b are welded in such a butted state, step welding or perforated welding may occur due to a change in the butted gap at the plate end.

  Therefore, the shaping rolls 6a and 6b press the butting portion after cutting with the guillotine shear 5 (shaping step), thereby correcting the shape defect in the butting portion such as burr generated by cutting or variation in cutting shape. it can.

  Specifically, first, the laser welding apparatus 1 moves the welding carriage 3 in the direction indicated by the arrow Y shown in FIG. At that time, the upper shaping roll 6b is lowered by the power of the cylinder 6c so as to have a predetermined interval between the upper shaping roll 6b and the lower shaping roll 6a. Then, as the welding carriage 3 moves in the Y direction, as shown in FIG. 7, the upper shaping roll 6b rides on the abutting portion between the preceding welded material 100a and the subsequent welded material 100b and is set in advance while rotating. The butted portion of the preceding workpiece 100a and the subsequent workpiece 100b is pressed with the load. Thereby, the shape defect of the butt | matching part of the to-be-welded materials 100a and 100b which arises by a cutting | disconnection can be corrected.

  Next, the laser welding apparatus 1 further moves the welding carriage 3 in the direction indicated by the arrow Y shown in FIG.

  As the welding carriage 3 moves, the butted portions of the materials to be welded 100a and 100b pass over the preheating heat induction induction head 7 arranged at a predetermined distance from the shaping rolls 6a and 6b. At that time, the butted portions of the materials to be welded 100a and 100b are induction-heated by the preheating heat induction heating head 7 so as to have a temperature necessary for preheating of laser welding (first heating step). Specifically, an electric current is supplied from a power source (not shown) to the coil 7b of the preheating induction heating head 7 to generate a magnetic flux (alternating magnetic flux), and this magnetic flux is applied to the surface direction of the workpieces 100a and 100b. The materials to be welded 100a and 100b are penetrated so as to be parallel. As a result, eddy currents are induced in the workpieces 100a and 100b, and Joule heat is generated by the eddy currents and induction heating is performed.

  Thus, the induction heating head 7 for preheat treatment penetrates the magnetic flux in a direction perpendicular to the plate thickness direction of the workpieces 100a and 100b, that is, parallel to the surfaces of the workpieces 100a and 100b. Since the materials to be welded 100a and 100b are induction-heated, the welded portions of the materials to be welded 100a and 100b can be heated and heated uniformly. Thereby, the water | moisture content of the welding part of to-be-welded material 100a, 100b can be evaporated, and generation | occurrence | production of a weld defect can be prevented.

  In addition, the heating by the preheating induction heating head 7 can reduce the cooling rate of the welded portion, thereby suppressing the appearance of martensite and the effect of tempering martensite by heating. Furthermore, since the workpieces 100a and 100b are induction-heated after being shaped by the shaping rolls 6a and 6b, the butt gap can be optimized by thermal expansion. Further, it is possible to obtain the effects of reducing the laser power of the machining head 9 and increasing the welding speed, which will be described later. The degree of preheating by the induction heating head 7 for preheat treatment is the degree of water washing in the upstream process, the thickness of the materials to be welded 100a and 100b, and the position of the materials to be welded 100a and 100b of the induction heating head 7 for preheat treatment. Depending on the relationship and the like, an appropriate ultimate temperature and holding time are adopted. Therefore, it is not particularly limited. Among them, moisture can be removed reliably, and from the viewpoint of manufacturing efficiency and energy efficiency, the temperatures of the front and back surfaces of the welded material in the abutted portions are both 200 ° C. or higher, and this is for 1 second. The heating maintained above is desirable. Thereby, it is possible to appropriately maintain the production efficiency without consuming more energy than necessary.

  Next, the laser welding apparatus 1 further moves the welding carriage 3 in the direction indicated by the arrow Y shown in FIG.

  As the welding carriage 3 moves, the butted portions of the materials to be welded 100 a and 100 b pass over the back roll 8. At this time, the workpieces 100a and 100b are laser welded by the processing head 9 and the back roll 8 (laser welding process). Specifically, the laser beam propagated in the air from the carbon dioxide laser oscillator 4 is irradiated from the processing head 9 to the butted portions of the workpieces 100a and 100b, whereby the preceding workpiece 100a and the subsequent workpiece 100b are welded. And are welded. Conditions such as laser output, focal diameter, focal position, welding speed, etc. are appropriately selected according to the type and thickness of the steel sheet, the size of the gap between the steel sheets in the butt, the distance between the steel sheet and the processing head, and the like.

  Further, the laser welding apparatus 1 moves the welding carriage 3 in the direction indicated by the arrow Y shown in FIG.

  As the welding carriage 3 moves, the butted portions (welded portions) of the materials to be welded 100 a and 100 b pass through the upper part of the post-heat treatment induction heating head 10. At that time, the butted portions (welded portions) of the workpieces 100a and 100b are induction-heated to a predetermined temperature by the post-heat treatment induction heating head 10 (second heating step). For example, heating is performed at a temperature of 400 ° C. or higher and 900 ° C. or lower. Thereby, since rapid cooling after welding is suppressed, excessive hardening of the welded part accompanying rapid cooling is suppressed, and breakage at the time of sheet passing is prevented. The heating temperature is preferably about 550 ° C. or higher and 800 ° C. or lower. Specifically, a current is supplied from a power source (not shown) to the coil 10a of the post-heat treatment induction heating head 10 to generate a magnetic flux (alternating magnetic flux), and this magnetic flux is applied to the workpieces 100a and 100b in the surface direction. Eddy currents are induced in the materials to be welded 100a and 100b by passing through them so as to be parallel to each other, and Joule heat is generated by the eddy currents to induce induction heating.

  Next, the laser welding apparatus 1 further moves the welding carriage 3 in the direction indicated by the arrow Y shown in FIG. At that time, the upper pressure roll 11b is lowered by the power of the cylinder 11c so as to have a predetermined distance between the upper pressure roll 11b and the lower pressure roll 11a. As the welding carriage 3 moves, the upper pressure roll 11b rides on the welded portions of the workpieces 100a and 100b and presses the welded portions of the workpieces 100a and 100b with a preset load while rotating ( Pressure step). As a result, the front and back surfaces of the welded materials 100a and 100b are smoothly finished. When the plate thickness of the preceding welded material 100a and the subsequent welded material 100b is the same, the thickness of the welded portion is set to be the same as that of the preceding welded material 100a and the rear It can be made substantially the same as the plate thickness of the row welding material 100b.

  Moreover, even when the plate thicknesses of the preceding welded material 100a and the subsequent welded material 100b are different, the surface shape of the welded portion can be made smooth by pressing the upper pressure roll 11b and the lower pressure roll 11a. .

  As described above, according to the laser welding apparatus 1 according to the first embodiment, the defective shape of the butted portion of the materials to be welded 100a and 100b is corrected to prevent welding defects such as perforation during welding, and further welding. Cracking can be prevented.

  The shaping rolls 6a and 6b, the preheating heat treatment induction heating head 7, the processing head 9, the back roll 8, the post heat treatment induction heating head 10, and the pressure rolls 11a and 11b are spaced at predetermined intervals in the welding direction. Is arranged in. Therefore, when welding pre-heat treatment by the induction heating head 7 for pre-heat treatment and / or post-heat treatment by the induction heating head 10 for post-heat treatment, the pre-heat treatment and / or post-heat treatment are not performed. It is also possible to control so as to omit.

<Second Embodiment>
In the laser welding apparatus 1 according to the first embodiment, a processing head for welding the workpieces 100a and 100b by irradiating laser beams to the workpieces 100a and 100b heated by the preheating induction heating head 7. 9 is provided.

  The laser welding apparatus 1a according to the second embodiment is configured to include a machining head 9a having a function of injecting a filler wire instead of the machining head 9.

  Here, the filler wire is a metal filler material, and is often used particularly when the materials to be welded 100a and 100b are difficult-to-weld materials such as high carbon steel and high Si steel. When laser welding is performed while injecting filler wire into the welded portion by the processing head 9a, there is an effect of diluting the weld metal, and welding quality can be improved. Further, even when the machine accuracy is lowered due to the aging of the guillotine shear 5 and the shape of the butt portion of the materials to be welded 100a and 100b varies, by performing laser welding while injecting filler wire into the welded portion, The variation in shape at the butted portions of the welded materials 100a and 100b can be absorbed.

  FIG. 8 is a cross-sectional view of the welded portion when welding is performed without using the filler wire, and FIG. 9 is a cross-sectional view of the welded portion when welding is performed using the filler wire.

  As shown in FIG. 8, when the welded materials 100a and 100b are welded without a filler wire, the welded portion is slightly thinner than the original thickness of the welded materials 100a and 100b. On the other hand, as shown in FIG. 9, when it welds using a filler wire, a welding part becomes thick with respect to the original thickness of to-be-welded material 100a, 100b. Such a change in the weld joint shape of the materials to be welded 100a and 100b causes a breakage of the steel sheet when rolled in the rolling line.

  However, in the laser welding apparatus according to the second embodiment, as shown in FIG. 10, the welded portion is pressed by pressing the welded portion with the upper pressure roll 11b and the lower pressure roll 11a. The front and back of the can be finished smoothly.

  Therefore, the welded joint shape of the welded materials 100a and 100b in the welded portion does not change suddenly, so that the steel sheet can be prevented from being broken even in the rolling line.

  Further, even when the plate thickness of the preceding welded material 100a and the plate thickness of the subsequent welded material 100b are different from each other, as shown in FIG. Breakage can be prevented.

<Third Embodiment>
FIG. 12 is a perspective view of a laser welding apparatus according to the third embodiment.

  The laser welding apparatus 1 according to the first embodiment includes a carbon dioxide laser oscillator 4 and a processing head 9 that irradiates the butted portions of the workpieces 100a and 100b with laser light propagated in the air from the carbon dioxide laser oscillator 4. It was.

In the laser welding apparatus 1b according to the third embodiment, instead of the carbon dioxide laser oscillator 4, a YAG laser oscillator, an oscillator 4b such as a fiber laser oscillator or a disk laser oscillator in which a plurality of fiber crystals are arranged in parallel is provided. And a processing head 9b that irradiates the butted portions of the materials to be welded 100a and 100b with laser light emitted from the oscillator 4b and transmitted through the optical fiber 12.
The fiber-like laser oscillator means that Yb (ytterbium) is added to the core fiber of the double clad fiber, and LD (laser diode) pumping light introduced into the double clad layer is transmitted, thereby exciting the core fiber. This is a known oscillator configured to increase the output by connecting in parallel a module for extracting a laser beam by amplification.

  Thus, the laser welding apparatus according to the present invention can be applied to any laser oscillator, and can similarly reduce the shape defects and weld cracks of the welded portions of the workpieces 100a and 100b.

  Next, the embodiment will be described in more detail. However, the present invention is not limited to this embodiment.

In this example, moisture remains on the front and back surfaces, a steel plate whose ends are cut and formed into a butt shape, this steel plate is butted, the butt portion is heated to a predetermined temperature, and then the butt portion is welded with a laser. In the case of carrying out the inventive method (invention example) and in the case of welding with a laser without heating the butted portion (comparative example), the bonding strength was compared. In addition, the example of the present invention and the comparative example 2 are cases where a steel sheet having a large amount of residual moisture is used, and the comparative example 1 is a case where a steel sheet having a small amount of residual water is used.
<Conditions>
The conditions are shown below.
・ Laser type: Carbon dioxide laser, fiber laser ・ Laser output: 10 kW
・ Betting gap of steel plates: 0.0mm
-Steel plate thickness: 2.2 mm, 4.0 mm
-Welding speed: 8.0 m / min (when plate thickness is 2.2 mm), 6.0 m / min (when plate thickness is 4.0 mm)
-Heating of the butting part: The temperature of the front and back surfaces is 200 ° C or higher by induction heating, and the holding time of 200 ° C or higher is 1.0 second or longer

<Evaluation method>
A repeated bending test with a radius of curvature of 60 mm was performed, and the bonding strength was evaluated by comparing the number of times until fracture. The maximum number of repetitions was set to 20, and those that did not break even after repeated bending 20 times were judged to have good bonding strength.

<Result>
Table 1 shows the results.

  As shown in Table 1, a steel plate subjected to laser welding by the laser welding method of the present invention has a high repeated bending strength regardless of the plate thickness, and a good joint strength is obtained. On the other hand, in the comparative example, when the residual moisture amount is large (Comparative Example 1-2, Comparative Example 2-2), the bonding strength is extremely low regardless of the plate thickness, and the residual moisture amount is small (Comparative Example 1- 1 and Comparative Example 2-1), the bonding strength decreased at a plate thickness of 4.0 mm.

  FIG. 13 and FIG. 14 show examples of the cross section of the welded portion using a carbon dioxide laser and a fiber laser, respectively. FIGS. 13A and 14A are obtained by the laser welding method of the present invention, and FIGS. 13B and 14B are welded by a comparative example. As shown in FIGS. 13B and 14B, by performing laser welding with moisture remaining, blow hole defects or defects shown in FIG. 13B are obtained. B) and a defect in which the surface shown in FIG. 14B is greatly depressed are observed, and it is presumed that the weld strength is reduced due to this defect.

  While the present invention has been described in connection with the most practical and preferred embodiments at the present time, the present invention is not limited to the embodiments disclosed herein. The present invention can be changed as appropriate without departing from the gist or concept of the invention that can be read from the claims and the entire specification, and a laser welding method for a steel sheet and a laser welding apparatus for such a method are also included in the technical scope of the present invention. It should be understood as encompassed by the scope.

1, 1a, 1b Laser welding equipment 2 Clamp (holding means)
3 welding carriage 4 carbon dioxide laser oscillator 4b YAG laser oscillator 5 guillotine shear 6 shaping roll (shaping means)
7 Induction heating head for pre-heat treatment (first heating means)
8 Back roll 9 Processing head (Laser welding means)
10 Induction heating head for second heat treatment (second heating means)
11 Pressure roll (Pressurizing means)
100a, 100b Material to be welded

Claims (14)

A method for laser welding of steel plates, in which end faces of a plurality of steel plates to which water is attached are butted against each other, and the butted portions of the butted steel plates are irradiated with a laser beam to weld the butted portions.
A cutting step of forming the end face of the steel sheet into a shape suitable for butting,
A butting step of butting the end surfaces formed by the cutting step;
A first heating step of heating the butted portion and removing the water;
A laser welding process for welding a steel sheet, comprising: a laser welding process for welding the butted portion heated by the first heating process with a laser.   The said 1st heating process heats with the coil which generates the magnetic flux which penetrates in parallel with the surface of the said steel plate, The laser welding method of the steel plate of Claim 1 characterized by the above-mentioned.   It further comprises a shaping step of shaping the steel sheet front and back surfaces of the butt portion by pressing the butt portion from above and below the plate thickness between the butt step and the first heating step. The laser welding method of the steel plate according to claim 1.   A second heating step for heating the welded portion of the steel plate welded in the laser welding step; and pressing the welded portion heated by the second heating step from the vertical direction of the plate thickness. A method for laser welding a steel sheet according to claim 1, further comprising a pressing step for shaping.   The said 2nd heating process heats with the coil which produces | generates the magnetic flux which penetrates in parallel with the surface of the said steel plate, The laser welding method of the steel plate of Claim 4 characterized by the above-mentioned.   The method according to claim 4, wherein the heating by the second heating step is performed simultaneously with the laser welding step.   In the said 1st heating process, the temperature of the said steel plate front and back of this butt | matching part reaches 200 degreeC or more by the heating of the said butt | matching part, The steel plate in any one of Claims 1-6 characterized by the above-mentioned. Laser welding method. A steel plate laser welding apparatus that is disposed on the downstream side of an apparatus for bringing water into contact with a steel plate, butts the end faces of the plurality of steel plates, irradiates the butted portion of the abutted steel plate with a laser beam and welds the butted portion. There,
Cutting means for forming the end face of the steel sheet into a shape suitable for the butting,
First heating means for heating the butted portion to remove the water;
A laser welding apparatus for a steel sheet, comprising: laser welding means for welding the butted portion heated by the first heating means with a laser.   9. The laser welding apparatus for steel sheets according to claim 8, wherein the first heating means is a coil that generates a magnetic flux penetrating in parallel with the surface of the steel sheet.   9. The apparatus according to claim 8, further comprising: shaping means for shaping the front and back surfaces of the abutting portion by pressing the abutting portion from above and below the plate thickness before the abutting portion is welded by the laser welding means. The steel plate laser welding apparatus as described.   The second heating means for heating the welded portion of the steel plate welded by the laser welding means, and the welding portion heated by the second heating means is pressed from above and below in the plate thickness. The steel plate laser welding apparatus according to claim 8, comprising pressurizing means for shaping the portion.   The said 2nd heating means is a coil which generates the magnetic flux which penetrates in parallel with the surface of the said steel plate, The laser welding apparatus of the steel plate of Claim 11 characterized by the above-mentioned.   The steel plate laser according to claim 11, wherein a welding carriage having the shaping means, the first heating means, the laser welding means, the second heating means, and the pressurizing means is provided to be able to travel. Welding equipment.   The laser welding means includes a laser beam oscillator composed of a plurality of fiber-shaped or disk-shaped crystals arranged in parallel and an optical fiber that transmits laser light emitted from the oscillator. The laser welding apparatus of the steel plate in any one of Claims 8-13.