JP2009166050A - Laser beam welding method for steel plate, and its apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam welding method and its apparatus capable of preventing any damage of an optical component due to sputtering, and preventing the adhesion of sputtering to a workpiece to be welded. <P>SOLUTION: In the method for welding butted steel plates by using laser beam which is emitted from an oscillator 11 consisting of a plurality of crystalline bodies, transmitted via optical fibers 12, and condensed by an optical system 14, a first gas jetting means 17 for jetting gas from the transverse direction to sputtering scattered from a molten pool C formed by irradiation with the laser beam is arranged between the optical system and the steel plates, and the laser beam is emitted to perform the welding while jetting the gas across just above the molten pool so that the vertical distance from an extension A<SB>k</SB>along a lower end of a jet port of the first gas jetting means and the molten pool is in a range of ≤3 mm. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser welding method and apparatus for a steel sheet, and more particularly, to suppress deterioration in welding quality due to spatter generated during welding adhering to the surface of a material to be welded and damage due to adhering to a laser optical component. The present invention relates to a method and apparatus for laser welding of steel plates that can be used.

  Laser welding is a welding method in which a laser beam, which is a high-density energy beam, is condensed by an optical component, irradiated to a material to be welded, and the material to be welded is melted. Laser welding has characteristics that high-speed welding is possible and its heat-affected range is small compared to other welding methods such as arc welding.

  Laser welding takes advantage of these characteristics, and examples include application to member welding such as automobile assembly welding and tailored blank welding, as well as continuous processing of steel sheets such as pickling lines and cold rolling lines. In a continuous line, in order to supply steel sheets to the continuous line without interruption, it is applied to the so-called coil splicing welding process that connects the end surface of the welding material, which is the preceding steel plate, and the end surface of the welding material, which is the subsequent steel plate. An example is seen.

  However, on the other hand, since the high-density energy is irradiated, the metal melts rapidly from the molten pool formed due to rapid melting of the metal. This can be a problem in ensuring the quality of the weld. This scattered molten metal is called spatter.

  For example, in the member assembly welding, when the appearance quality is required for the welded portion, the spatter adheres to the vicinity of the welded portion, so that the appearance quality is remarkably impaired. In addition, spatter adhering to the periphery of the welded part by the coil joint welding as described above is rolled by a roll in the next rolling step, for example. The dents are transferred from the roll to the surface of the steel sheet, which deteriorates the appearance quality of the product. Or the sputter | spatter adhering to the steel plate surface is pushed in in a steel plate, and becomes a factor of the welding part fracture | rupture in a rolling process. Thus, since the spatter adhering to the material to be welded deteriorates the quality of the welded portion, it is necessary to perform grinding or the like, which is an impediment to production efficiency.

  Furthermore, adhesion to optical components (protective glass and lenses) by sputtering often becomes a problem in maintaining the welding quality. As described above, laser welding uses light condensed by an optical component as a welding heat source. For this reason, the spatter adhering to the surface of the condensing lens or the protective glass absorbs the laser beam, reduces the amount of laser irradiation to the material to be welded, and causes a defective welding. Furthermore, the spatter that has absorbed the laser beam becomes high temperature, and there is a possibility that the condensing lens and the protective glass are damaged.

  Patent Documents 1 to 5 are disclosed as countermeasures against such adhesion of spatter generated during welding. Japanese Patent Application Laid-Open No. H10-228561 discloses a spatter adhesion prevention method using a sputter shielding plate and a high-speed airflow. According to this, the spatter is shielded by the shielding plate, and the spatter passing through the light transmission hole in the shielding plate can be blown off by the high-speed air flow. Patent Document 2 discloses that the tip of a laser processing head is a double tubular nozzle and a shielding curtain is formed by an outer nozzle. Patent Document 3 discloses a method in which a gas having a gas pressure of 0.6 to 1.2 times the gas pressure supplied from a center cone is sprayed from a nozzle provided on a side from above an acute angle to scatter sputtering. Has been. According to this, for the spatter scattered from the molten pool, directivity can be given by the side gas flow immediately after detachment, and the amount of spatter entering the laser head can be reduced.

  In Patent Document 4, in addition to the protection by the protective glass, by flowing ultrasonic gas into the processing head and making the processing nozzle tip a funnel shape, the ability to suck spatter from the nozzle tip hole is improved, It is disclosed that the spatter scattered inside the processing nozzle is efficiently blown off. Patent Document 5 discloses a technique for injecting a fluid from a lateral direction between a laser processing nozzle and a material to be welded for circumferential welding of a pipe.

Japanese Patent No. 2667769 JP-A-11-123578 Japanese Patent Laid-Open No. 10-328876 JP-A-9-164495 JP 2003-334686 A

  However, the welding described in Patent Documents 1 to 3 does not take into consideration the spatter property of being generated radially from the molten pool, and in particular, it has not always been possible to prevent the spatter from adhering to the material to be welded. Further, in the welding described in Patent Document 4, the suction force generated by the supersonic gas flow is essential, but naturally, in order to draw all the spatter scattered radially from the molten pool into the nozzle only by the suction force, A large suction force is required, and this suction force also affects the molten pool, and there is a problem that there is a high possibility of causing a welding defect.

  In the welding described in Patent Document 5, especially when the laser output is large, the amount of spatter scattering increases, so that spatter adheres to the processing head.

  In view of the above problems, it is an object of the present invention to provide a laser welding method and apparatus capable of preventing optical component damage due to sputtering and preventing spatter from adhering to a workpiece.

As a result of intensive studies, the inventors obtained the following knowledge and completed the invention.
(1) By blowing a gas (inert gas, air, or a mixed gas thereof) from a direction lateral to the scattering direction of sputtering, the molten metal is blown off in the gas injection direction. As a result, the spattering time until the spatter adheres to the surface of the steel sheet is prolonged, so that the surface of the spatter is sufficiently cooled, and the steel sheet is scattered further away from the molten pool to a place where the temperature of the steel sheet is low, thereby preventing sticking to the steel sheet surface. Thus, it is possible to prevent the occurrence of weld quality defects accompanying the adhesion to the steel sheet surface.
(2) Since spatter scatters radially from the molten pool, spatter adhesion can be effectively prevented by blowing gas at a position close to the steel plate surface.
(3) When the injection speed directly above the molten pool is high, molten metal flows out of the molten pool, and spatter increases. Therefore, for example, by injecting gas from a nozzle having two injection ports in the width direction and increasing the surrounding injection speed compared to directly above the molten pool, the molten metal flows out of the molten pool due to the blowing of gas. Suppressed and can prevent deterioration of welding quality.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiment.

The invention according to claim 1 uses a laser beam emitted from an oscillator (11) composed of a plurality of crystal bodies, transmitted by an optical fiber (12), and collected by an optical system (14). A method of welding the butted steel plates, wherein a gas is injected from a lateral direction toward a spatter scattered from a molten pool (C) formed by laser beam irradiation between an optical system and a steel plate. A gas jetting means (17) is arranged, directly above the molten pool so that the vertical distance between the extension line (A _k ) along the lower end of the jet port of the first gas jetting means and the molten pool is 3 mm or less. The above-mentioned problem is solved by providing a laser welding method for a steel sheet, characterized in that welding is performed by irradiating a laser beam while jetting a gas across the plate.

Here, the “extension line along the lower end of the injection port” in the first gas injection means is determined by the lower end shape of the injection port. For example, the lower end of the injection port is the steel plate 1 as in the example shown in FIG. If it is parallel to the upper surface, the extension line _Ak is also parallel to the steel plate 1. Further, for example, when the lower end of the injection port is divergent, an extension line is formed so as to extend the divergent lower end.

  The invention according to claim 2 is characterized in that the gas in the laser welding method of the steel sheet according to claim 1 is injected in the welding progress direction.

  According to a third aspect of the present invention, in the cross section parallel to the steel plate surface, the velocity distribution of the gas injected from the first gas injection means (27) in the laser welding method of the steel plate according to the first or second aspect is the above. It is characterized in that the velocity on both sides is larger than that directly above the weld pool.

  According to a fourth aspect of the present invention, there is provided a method in which the spattering is applied between the optical system (14) and the first gas injection means (17) in the laser welding method for a steel sheet according to any one of the first to third aspects. A second gas injection means (37) for injecting a gas from the direction is arranged, and a laser beam is emitted from the second gas injection means while injecting a gas above the gas injection range of the first gas injection means. And welding.

  The invention according to claim 5 is a laser welding apparatus (10, 30, 40) for a steel plate that abuts the end of the steel plate and welds the butted portion by irradiating a laser with the laser, and is composed of a plurality of crystals. An optical system (11), an optical fiber (12) for transmitting a laser beam emitted from the oscillator, an optical fiber connected to the optical fiber, and a collimating lens (15) and a condenser lens (16). 14) and first gas injection means (17) for injecting gas from the lateral direction toward the spatter scattered from the molten pool (C) formed by laser beam irradiation, the first gas injection The means is arranged to be able to inject the gas across the molten pool so that the vertical distance between the extension line along the lower end of the injection port of the first gas injection means and the molten pool is 3 mm or less. Steel characterized by The problem is solved by providing a laser welding apparatus for a plate.

  The invention according to claim 6 is characterized in that the first gas injection means (27) in the laser welding apparatus according to claim 5 comprises a nozzle having a plurality of injection ports arranged in parallel with the steel plate. And

  The invention described in claim 7 is the height adjusting means (48) for adjusting the distance between the first gas injection means (17, 27) and the steel sheet in the steel plate laser welding apparatus according to claim 5 or 6. It is characterized by providing.

  Invention of Claim 8 is between the optical system (14) and 1st gas injection means (17, 27) in the laser welding apparatus of the steel plate as described in any one of Claims 5-7, Sputtering is provided with second gas injection means (37) for injecting gas from the lateral direction and above the gas injection range of the first gas injection means.

  According to a ninth aspect of the present invention, the oscillator (11) in the laser welding apparatus for a steel sheet according to any one of the fifth to eighth aspects includes a plurality of fiber-shaped or disk-shaped crystals arranged in parallel. It is comprised from these.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that a sputter | spatter adheres to a to-be-welded material or an optical component in laser welding, and can improve the quality of a to-be-welded material and can protect an optical component.

  Such an operation and a gain of the present invention will be clarified from the best mode for carrying out the invention described below.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  First, the example of the apparatus provided for the laser welding method of the present invention will be described. FIG. 1 is a diagram schematically showing each configuration provided in the laser welding apparatus 10 of the present invention according to the first embodiment. The welding apparatus 10 includes a laser oscillator 11, an optical fiber 12, a welding head 14, and a nozzle 17. The welding head 14 includes a condensing system including a collimating lens 15 and a condensing lens 16. Each configuration will be described below.

  The laser oscillator 11 is a device that oscillates a laser serving as a welding heat source. The type of laser used for laser welding by the welding apparatus 10 is not particularly limited as long as it can be transmitted by the optical fiber 12, and it is sufficient that such a laser can be oscillated. Examples thereof include an oscillator such as a YAG laser, a disk laser, and a fiber laser. Thus, it is possible to perform welding efficiently by using a laser that can be transmitted through an optical fiber and can obtain a high output. The laser output is not particularly limited, but the effect of the present invention becomes more remarkable as the output is higher.

  The optical fiber 12 is means for transmitting a laser from the laser oscillator 11 to the welding head 14. By applying an optical fiber, it is possible to provide a welding apparatus 10 that can easily transmit a laser and can be easily maintained. The diameter of the optical fiber 12 is not particularly limited, but a fiber having a diameter of 1.0 mm or less is usually used. The diameter is preferably small from the viewpoint of the size and energy density of the condensing optical system, and is 0.6 mm or less. Preferably there is. More preferably, it is 0.2 mm or less.

The welding head 14 is connected to the output end 13 of the optical fiber 12 and is a means for introducing a transmitted laser, controlling the laser to be suitable for welding, and emitting the laser to a welded portion. The welding head 14 includes a collimating lens 15 and a condensing lens 16, and the focal diameter is determined by the diameter of the optical fiber 12 described above and the ratio of the focal lengths of both lenses. For example, the focal diameter can be reduced by reducing the diameter of the optical fiber 12 and reducing the focal length of the condenser lens relative to the focal length of the collimating lens. Specifically, when the fiber diameter is D _fiber , the focal length of the collimating lens is F1, and the focal length of the condenser lens is F2, the spot diameter D at the focal position is expressed by D = D _fiber · (F2 / F1). Is done.

  The nozzle 17 is a normal nozzle having a so-called injection port, and can inject gas from the injection port in a predetermined direction. Here, the type of nozzle is not particularly limited, and any form of nozzle can be applied. Examples thereof include a flat nozzle having a rectangular injection port and a round tube nozzle made of a circular tube.

The broken line indicated by A in FIG. 1 indicates the axis of the nozzle 17 in the gas injection direction, and the portion surrounded by the dotted line indicated by B indicates the region where the jet flows. A _k indicates an extension line along the lower end of the injection port of the nozzle 17 and substantially coincides with the lower end of the region where the jet flow indicated by B. Moreover, the site | part shown by C is a site | part in which the molten pool C in the steel plate 1 which is a to-be-welded material is formed. Thus, in the welding apparatus 10, with the axis A and extension A _k of the nozzles 17 are configured to pass directly over the molten pool C, approximately said axis A and extended line A _k is the upper surface of the steel sheet 1 Parallel. The axis A and the extension line _Ak and the welding direction do not necessarily need to coincide with each other, but the axis A and the extension line _Ak and the welding direction preferably coincide with each other in order to prevent spatter adhesion more efficiently. Further, in addition to the case where the extension line _Ak is parallel to the upper surface of the steel plate 1 like the nozzle 17 shown in FIG. 1, the nozzle 17 ′, the extension line A ′ _k , or the nozzle 17 ′ shown in FIG. It may be arranged as indicated by ', extension line A ″ _k . That is, the nozzle 17 ′ is inclined θ ′ with the extension line A ′ _k upward with respect to the extension line A _k , and the nozzle 17 ″ has the extension line A ″ _k with θ ′ downward with respect to the extension line A _k . 'It is arranged to tilt. Even with such a nozzle arrangement, the welding apparatus of the present invention can be obtained. Here, the magnitudes of θ ′ and θ ″ are not particularly limited, but θ ′ and θ ″ are preferably 0 ° to 30 ° from the viewpoint of nozzle arrangement and the like, and in particular, θ ″. Is more preferably 0 to 20 degrees.

  The width of the nozzle 17 (the width of the injection port in the direction perpendicular to the welding progress direction and the plate thickness direction of the steel plate) is about one time the width of the molten pool C at the surface position of the steel plate 1 so as to cover the molten pool C. That's it. Preferably it is 3 times or more. The thickness of the nozzle (the size of the injection port perpendicular to the width) is appropriately set depending on the injection flow rate and the injection pressure.

The height direction of the nozzle 17 (the vertical position in FIG. 1 and FIG. 2) is extended lines A _k , A _k ′, A _k ″ along the lower end of the nozzle 17, as will be described later. The vertical distance from C (the distance indicated by D in FIGS. 1 and 2) is adjusted to be 3 mm or less.

  FIG. 3 is a view for explaining the nozzle 27 provided in the welding apparatus of the present invention according to the second embodiment. In the welding apparatus according to the second embodiment, since the components other than the nozzle 27 are common to the welding apparatus 10, the description thereof is omitted here. 3A is a view of the nozzle 27 viewed from the injection port side, and FIG. 3B is a view of the nozzle 27 viewed from the upper surface side in a posture in which the nozzle 27 is attached to the welding apparatus. Represents.

  The nozzle 27 is characterized by having two parallel injection ports 27b and 27c in the base portion 27a. Accordingly, the nozzle 27 can emit two jets B2 and B3 having two axes A2 and A3. Here, the nozzles 27 are arranged in the welding apparatus so that the respective injection holes 27b and 27c are at the same height from the surface of the material to be welded. In addition, it is installed so that A4, which is an intermediate line between the two axes A2 and A3, passes right above the melting portion. Also in this case, the vertical distance between the extension line along the lower ends of the injection ports 27b and 27c of the nozzle 27 and the molten pool is adjusted to be 3 mm or less.

  In FIG. 3 (a), if the interval inside the injection port indicated by Li becomes too narrow with respect to the molten pool width, the injection speed immediately above the molten pool increases, the molten metal flows out of the molten pool, and the spatter increases. On the contrary, if the width is larger than the molten pool width, the spatter scattered from the molten pool cannot be blown off, and therefore it is preferably 0.5 times or more and 1 time or less with respect to the molten pool width. Moreover, the space | interval of the outer side of the injection nozzle shown by Lo is 1 time or more of a molten pool width, Preferably it is 3 times or more so that a molten pool can be covered.

  4 and 5 are schematic views for explaining the welding apparatus 30 of the present invention according to the third embodiment, and in particular, the nozzle 17 of the first gas injection means and the second gas injection means provided in the welding apparatus 30. FIG. It is the figure which paid its attention to arrangement | positioning of the nozzle 37 of this. FIG. 4 schematically shows how the nozzles 17 and 37 are arranged when the welding apparatus 30 is viewed from the side of the steel plates 1 ′ and 2 ′ irradiated with the laser. FIG. 5 is a view of the welding apparatus 30 as viewed from the front side, and is a diagram schematically showing each configuration. As can be seen from FIGS. 4 and 5, the welding apparatus 30 is characterized in that another nozzle 37 is provided in addition to the configuration of the welding apparatus 10. Since the components other than the nozzle 37 in the welding apparatus 30 are the same as those in the welding apparatus 10, description thereof is omitted here. The line indicated by E in FIG. 4 represents the axis of the nozzle 37, and the area indicated by F represents the range through which the jet flows.

4 and 5, the nozzle 37 is arranged so that the axis A of the nozzle 17 and the axis E of the nozzle 37 have a relationship of being twisted at an angle φ. However, it does not necessarily have to be arranged so as to have a twisted position, and the axis A and the axis E may be arranged in the same direction. The angle φ is preferably within 50 degrees.
When the jet flow of the nozzle 37 interferes with the jet flow of the nozzle 17, the spatter blowing effect by the nozzle 17 is reduced. Therefore, it is preferable to select a distance G at which the jet flow of the nozzle 37 does not interfere with the jet flow of the nozzle 17. Here, E _k is an extension line of the lower end of the injection port of the nozzle 37. Specifically, it is desirable that the distance G of the nozzle 37 be equal to or greater than the height of the extension line parallel to the axis of the upper end of the nozzle 17 nozzle. Although the upper limit is not particularly limited, the nozzle 37 is installed below the condenser lens so that spatter does not substantially adhere to the condenser lens. 4 and 5 show an example in which one nozzle 37 is provided, the present invention is not limited to this example, and a plurality of nozzles may be arranged.

Similarly to the nozzle 17, the nozzle 37 is configured such that an extension line E _k along the lower end of the injection port passes directly above the molten pool C, and the extension line E _k is substantially on the upper surface of the steel plate 1 ′. Parallel. However, the present invention is not limited to this, and the nozzle 37 may also be arranged such that the extension line along the lower end of the nozzle injection port has an angle with respect to the upper surface of the steel plate, like the nozzles 17 ′ and 17 ″. Good. The nozzle 37 preferably has a horizontal injection port width that is not less than the width of the molten pool and not more than the diameter of the condenser lens. The injection port thickness of the nozzle 37 is appropriately set according to the injection flow rate and the injection pressure.

  FIG. 6 is a view for explaining a welding apparatus 40 according to the fourth embodiment. In addition to the configuration of the welding apparatus 10, the welding apparatus 40 further includes nozzle height adjusting means 48. Since the configuration other than the nozzle height adjusting means 48 is common to each configuration of the welding apparatus 10, the description thereof is omitted here.

  The nozzle height adjusting means 48 is a means for changing the position in the nozzle height direction (up and down direction in FIG. 6). According to this, for example, when the spot irradiated on the welded portion is shifted from the focal position (defocus) or the amount of defocus is changed, the height of the nozzle 17 can be easily changed as necessary. The position can be changed. As shown in FIG. 6, the nozzle adjustment means 48 may be incorporated in the optical system 14 and integrated.

  A mechanism or the like provided for adjusting the height of the nozzle height adjusting means 48 is not particularly limited. For example, it may be a mechanically configured mechanism, or may be configured to automatically move to a program position stored in advance by electrically detecting the position.

  By using the welding apparatuses 10, 30, 40, etc. as described above, it is possible to prevent optical component damage due to spatter and to prevent spatter from adhering to the material to be welded.

  Next, the welding method of the present invention will be described. For the sake of clarity, welding using the above-described welding apparatus will be described here, but the welding method of the present invention is not limited to this, and any apparatus that exhibits the effects of the present invention can be used.

The welding method M1 of the present invention according to the first embodiment is performed by welding using, for example, the welding apparatus 10. That steel plates 1 and 2 which are butted in the case of welding using a laser beam, and the extension line A _k along the injection port lower end of the nozzle, the vertical distance between the molten pool C (distance indicated by D in FIG. 1) Within 3 mm. Preferably, it is within 2 mm.

  Thereby, the molten metal scattered as spatter is blown off in the direction of the jet. And since the scattering time until the spatter adheres to the steel sheet surface becomes long, the surface of the spatter is sufficiently cooled, and the steel sheet is scattered farther away from the molten pool to a place where the steel plate temperature is low. The Thereby, generation | occurrence | production of the welded article defect accompanying adhesion to the steel plate surface can be prevented. Similarly, it is possible to suppress adhesion to the optical device.

  Further, by reducing the vertical distance between the extension line along the lower end of the nozzle and the molten pool to within 3 mm, the sputter that radiates upward from the molten pool is not yet spread out. In this way, a jet can be applied and spatter adhesion can be prevented efficiently.

  The jet is preferably horizontal with respect to the upper surface of the molten pool, but is not limited thereto, and may have an angle in a direction away from or closer to the upper surface of the molten pool. The angle is not particularly limited, but when the jet directly hits the molten pool, the molten metal may flow out of the molten pool. Therefore, in θ ′, θ ″ shown in FIG. Both θ ″ are preferably 0 ° to 30 °, and in particular, θ ″ is preferably 0 ° to 20 °.

  Although the kind of gas injected is not specifically limited, Compressed air, inert gas, oxygen, nitrogen, etc. can be used. As conditions for the jet flow, for example, compressed air and a pressure of 0.3 MPa to 0.7 MPa and a flow rate of 100 L / min to 300 L / min are desirable.

  The welding method M2 of the present invention according to the second embodiment is performed using, for example, a welding apparatus according to the second embodiment. That is, the welding method M2 is characterized by a jet velocity distribution in addition to the welding method M1. Specifically, as shown in FIG. 7, the flow velocity distribution becomes slower at the center. And in the said velocity distribution, it welds so that the slow part of the center may pass just above a molten pool. This makes it possible to reduce the direct influence of the jet flow on the molten pool. Therefore, it becomes possible to make the jet flow closer to the molten pool, and it is possible to more efficiently prevent spatter adhesion.

  The welding method M3 of the present invention according to the third embodiment is performed using, for example, the welding apparatus 30. That is, in addition to the first jet supplied in the welding method M1 or the welding method M2, welding is performed while the second jet is jetted at a height position closer to the optical device. The second jet is supplied by the nozzle 37 and the like, and the arrangement and the like of the jet are as described above. According to this, since the jet is provided on the side close to the optical device, it is possible to further suppress the adhesion of spatter to the optical device.

  By the welding methods M1 to M3 and the like described above, it is possible to prevent optical parts from being damaged by spatter and to prevent spatter from adhering to the material to be welded. In addition, although steel material was demonstrated to the example as a to-be-welded material so far, it is not limited to this, It can apply also to plate materials of other metals, such as stainless steel, titanium, and aluminum.

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

  In the examples, butt welding of steel sheets was performed under various conditions, and the sputter adhesion state at that time was evaluated. This will be described in detail below.

<Conditions>
The common conditions in each example are as follows.
-Test steel plate: Low carbon steel (C: 0.02 mass%), plate thickness 6.0 mm
・ Laser oscillator: Fiber laser oscillator, output 10kW
-Collimating lens: Focal length 125mm
・ Condenser lens: focal length 200mm
・ Spot condition: Defocus amount 5mm
・ Welding speed: 3.4 m / min

  Other conditions are shown in Table 1.

  Here, a flat nozzle or a round tube adjacent nozzle was used as the first injection nozzle. With a flat nozzle shape, a substantially uniform velocity distribution can be obtained in the cross section of the jet. On the other hand, the nozzle adjacent to the round tube uses a nozzle in which two round tubes having an inner diameter of 4 mm and an outer diameter of 6 mm are adjacent to each other in the horizontal direction, so that the velocity distribution at the center is slow in the cross section of the jet as shown in FIG. You can All nozzles were disposed at positions where the nozzle tip position was 12 mm away from the laser beam path, and compressed air was injected at a pressure of 0.5 MPa and 100 L / min.

  A flat nozzle having a width of 50 mm is used as the second injection nozzle, and is arranged at a height of 50 mm from the surface of the material to be welded so that its axis is in the same direction as the axis of the first injection nozzle. Of compressed air was injected at 300 L / min.

  The position in the height direction of the nozzle is defined by the vertical distance between the extension line along the lower end of the nozzle and the molten pool.

  The injection angle (vertical angle) means the vertical inclination with respect to a line parallel to the steel plate surface. 7 and 8 are 15 degrees and 40 degrees downward, respectively. The forward direction of the spray angle (horizontal angle) means spraying in the welding progress direction, and the angle is an angle with respect to the welding progress direction in a plane parallel to the upper surface of the workpiece. Further, “backward” means that the injection is performed in the direction opposite to the welding progress direction. In any example, the nozzle of the second jet has an injection angle (vertical angle) of 0 ° and an injection angle (horizontal angle) of 0 ° in the forward direction.

<Evaluation>
Welding was evaluated based on the spatter scattering height and the number of spatters attached to the material to be welded. The spatter scattering height is determined by observing the spatter scattered right above the welded part. If it exceeds 100 mm from the surface of the material to be welded, it will be “high”, if it exceeds 50 mm, it will be “medium”, and below that will be “low”. Judged at 3 levels. Then, “medium” and “low” were determined to be good with no spatter adhesion to the optical system lens. The number of spatters deposited on the material to be welded was determined by counting the number of spatters deposited per 100 mm weld length, and 5 or less. Further, from these evaluations, comprehensive determination as spatter adhesion was performed, and evaluation was made at three levels of ◎, ◯, and ×, and in order from the front, particularly good, good, and poor. The results are shown in Table 2.

  As can be seen from Table 2, according to the welding of the examples of the present invention, it was possible to reduce the number of spatters attached to the material to be welded. The overall judgment is also good or better. On the other hand, according to the welding of the comparative example, No. As in 1 and 2, the spatter adherence to the material to be welded increased to 20 or more. No. In No. 6, the vertical distance between the extension line parallel to the axis of the lower end of the first injection nozzle and the molten pool is 4 mm in height, and 10 or more large spatters of 4 mm or less adhered to the surface of the workpiece. .

  Although 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, but is claimed. The laser welding method and apparatus accompanying such changes can be appropriately changed without departing from the scope of the invention and the gist or idea of the invention that can be read from the entire specification, and the laser welding method and apparatus accompanying such changes are also included in the technical scope of the present invention. Must be understood as.

It is the figure which showed typically each structure of the welding apparatus of this invention concerning 1st embodiment. It is a figure which shows the example in which the nozzle and the jet flow were inclined upward or downward. It is a figure for demonstrating the nozzle with which the welding apparatus of this invention concerning 2nd embodiment is equipped. It is a figure for demonstrating arrangement | positioning of the nozzle of the welding apparatus of this invention concerning 3rd embodiment. It is the figure which showed typically each structure of the welding apparatus of this invention concerning 3rd embodiment. It is the figure which showed typically each structure of the welding apparatus of this invention concerning 4th embodiment. It is a figure for demonstrating the relationship between the velocity distribution of a jet, and a molten pool in the welding method of this invention concerning 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 To-be-welded material 2 To-be-welded material 10 Laser welding apparatus 11 Laser oscillator 12 Optical fiber 14 Welding head 15 Collimating lens 16 Condensing lens 17, 27 Nozzle (1st gas injection means)
37 nozzle (second gas injection means)
48 Height adjustment means

Claims (9)

A method of welding steel plates that are emitted from an oscillator composed of a plurality of crystal bodies, transmitted by an optical fiber, and abutted using a laser beam collected by an optical system,
Between the optical system and the steel plate, a first gas injection means for injecting gas from the lateral direction toward the spatter scattered from the molten pool formed by irradiation of the laser beam,
A laser beam is emitted while jetting the gas across the weld pool so that the vertical distance between the extension line along the lower end of the jet port of the first gas jet means and the melt pool is 3 mm or less. A laser welding method for a steel sheet, characterized by irradiation and welding.   The method of laser welding a steel sheet according to claim 1, wherein the gas is injected in a welding progress direction.   The velocity distribution of the gas injected from the first gas injection means is such that, in a cross section parallel to the surface of the steel plate, the velocity on both sides thereof is greater than directly above the molten pool. A method for laser welding of steel sheets as described in 1. Between the optical system and the first gas injection means, a second gas injection means for injecting a gas from the lateral direction to the sputter is disposed,
The steel plate according to any one of claims 1 to 3, wherein welding is performed by irradiating a laser beam while injecting a gas from the second gas injection unit to above the gas injection range of the first gas injection unit. Laser welding method. It is a laser welding apparatus for a steel plate that abuts the end portion of the steel plate and irradiates the butt portion with laser to weld it,
An oscillator composed of a plurality of crystals,
An optical fiber for transmitting a laser beam emitted from the oscillator;
An optical system to which the optical fiber is connected and having a collimating lens and a condenser lens;
A first gas injection means for injecting a gas from the lateral direction toward the spatter scattered from the molten pool formed by the irradiation of the laser beam,
The first gas injection means traverses directly above the molten pool so that the vertical distance between the extension line along the lower end of the injection port of the first gas injection means and the molten pool is 3 mm or less. A laser welding apparatus for steel sheets, wherein the gas is arranged to be jettable.   The laser welding apparatus according to claim 5, wherein the first gas injection means includes a nozzle having a plurality of injection ports arranged in parallel with the steel plate.   The laser welding apparatus of the steel plate of Claim 5 or 6 provided with the height adjustment means which adjusts the distance of a said 1st gas injection means and the said steel plate.   Between the optical system and the first gas injection means, there is provided a second gas injection means for injecting gas from the lateral direction to the sputter and above the gas injection range of the first gas injection means. The steel plate laser welding apparatus according to any one of claims 5 to 7.   The steel plate laser welding apparatus according to any one of claims 5 to 8, wherein the oscillator includes a plurality of fiber-shaped or disk-shaped crystals arranged in parallel.

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