Welding process

Abstract

Welding process comprising welding an upper plate (3) and a lower plate (2) overlapping with the upper plate (3) by irradiating a surface (3A) of the upper plate (3) with a laser beam, wherein the welding comprises forming a main weld path (42) that intersects a weld feed direction and includes inflection points on a vertically upper side and on a vertically lower side, wherein the upper plate (3) and the lower plate (2), viewed parallel to the welding feed direction, are mounted in an inclined manner with respect to a horizontal plane, and wherein, during the formation of the main welding path (42), while the irradiation with the laser beam continues, the movement of the laser beam is stopped for a specified period of time in an area near the inflection points on the vertically upper side, such that a welding speed in the area near the inflection points on the vertically upper side is made smaller than a welding speed in an area near the inflection points on the vertically lower side, and an amount of energy applied by the laser beam in the area in the vicinity of the inflection points on the vertically upper side is made greater than an amount of energy applied by the laser beam in the area in the vicinity of the inflection points on the vertically lower side, wherein the area near the inflection points on the vertically upper side is closer to the inflection points on the vertically upper side than to a centerline parallel to the welding feed direction, the centerline being located between the vertically upper side and the vertically lower side, and where the area near the inflection points on the lower vertical side is closer to the inflection points on the lower vertical side than to the center line.

Description

STATE OF THE ART

[0001] The present disclosure relates to a welding process.

[0002] A method for irradiating metal welding targets with a laser beam is known to weld metal elements together (JP 2005-527383 A, equivalent to WO 03 / 099505 A1). Such laser welding is also used to weld two overlapping metal plates.

[0003] DE 103 33 456 A1 discloses a method for machining workpieces with a moving laser beam, wherein the laser tool is held by a multi-axis mechanical manipulator on a manipulator hand at a distance above the workpiece and moved along a predetermined path in an offset movement.

[0004] DE 20 2004 003 775 U1 further describes a laser device for laser processing of workpieces with at least one laser source, which can be connected via a guide device to a laser tool on a multi-axis hand of at least one manipulator. BRIEF SUMMARY OF THE INVENTION

[0005] In a case where two metal plates are mounted at an angle to a horizontal plane, and where the gap between the two metal plates is large when they overlap, a conventional welding process may fail to adequately fill the gap between the metal plates with molten metal, leading to the risk of a poor weld.

[0006] One object of the invention is to provide a welding process which enables the improvement of the welding quality between an upper plate and a lower plate which are mounted in an inclined manner.

[0007] This problem is solved by a welding process according to claim 1 or according to claim 3. Advantageous embodiments are described in the dependent claims.

[0008] One aspect of the present disclosure is a welding process comprising welding an upper plate and a lower plate overlapping the upper plate by irradiating a surface of the upper plate with a laser beam. The welding includes forming a main weld path intersecting a weld feed direction and including inflection points. The upper plate and the lower plate are mounted at an inclination relative to a horizontal plane when viewed parallel to the weld feed direction. In forming the main weld path, the amount of energy applied by the laser beam in a region in the vicinity of the inflection point on a vertically upper side is designed to be greater than the amount of energy applied by the laser beam in a region in the vicinity of the inflection point on a vertically lower side.

[0009] In this configuration, a greater amount of energy is applied in the vicinity of the inflection point on the vertically upper side, where the molten metal tends to flow downwards, than in the vicinity of the inflection point on the vertically lower side. This facilitates the reduction of excessive melting in the vicinity of the inflection point on the vertically lower side and also allows for the compensation of insufficient molten metal in the vicinity of the inflection point on the vertically upper side. Consequently, weld quality can be improved. Furthermore, the inclined mounting of the upper and lower plates can increase the design flexibility of products and clamping devices.

[0010] According to one aspect of the present disclosure, when forming the main welding path, the welding speed in the region adjacent to the inflection point on the vertically upper side can be designed to be lower than the welding speed in the region adjacent to the inflection point on the vertically lower side. Such a design allows for simple and reliable adjustment of the amount of energy in the vicinity of the inflection points.

[0011] According to one aspect of the present disclosure, when forming the main welding path, the movement of the laser beam can be stopped for a specified period in the area adjacent to the inflection point on the vertically upper side, while the laser beam irradiation continues. Such an embodiment enables a simple and reliable reduction of the welding speed in the vicinity of the inflection point on the vertically upper side.

[0012] According to one aspect of the present disclosure, the welding process can further comprise stopping the laser beam irradiation after the formation of the main weld path and then performing renewed irradiation. Such a configuration allows for slow cooling at the endpoint of the welding process. Consequently, the occurrence of solidification cracks at the endpoint of the welding process can be reduced.

[0013] According to one aspect of the present disclosure, the welding process may further include the formation of an auxiliary weld path that is continuous and comprises a reciprocating or circular path prior to the formation of the main weld path. Such a configuration makes it possible to generate the molten metal in the auxiliary weld path in order to supply the molten metal to the main weld path. This can reduce the formation of a gap due to insufficient molten metal in the main weld path.

[0014] According to one aspect of the present disclosure, the auxiliary welding path can have a circular shape. Such a design facilitates the formation of a chamber for the molten metal, thereby enabling the molten metal to be fed to the main welding path easily and reliably.

[0015] According to one aspect of the present disclosure, the main weld path can comprise: an initial region that is continuous from the auxiliary weld path; and a subsequent region that is located further forward in the welding feed direction than the initial region and that has a larger turning distance than the initial region. Such a configuration makes it possible to utilize the molten metal in the vicinity of the starting point of the main weld path effectively and also to aim for a reduction in the time required to form the main weld path. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Exemplary embodiments of the present disclosure are described below with reference to the accompanying drawings. These show: Fig. 1 a flow and block diagram of a welding device used in a welding process of one embodiment; Fig. 2A A schematic perspective view of a welded section in the welding process of Fig. 1 and Fig. 2B a schematic representation of the welded section in the welding process of Fig. 1; Fig. 3A a schematic representation of an auxiliary welding path, Fig. 3B a schematic representation of an auxiliary welding path of a different embodiment than that shown in Fig. 3A is shown, and Fig. 3C a schematic representation of a main weld path; Fig. 4 a schematic representation showing relationships between a welding feed direction and an energy level or welding speed; Fig. 5 a schematic representation showing relationships between time and an energy level or temperature at the end of welding; Fig. 6 a flowchart of the welding process of the embodiment; Fig. 7 a flowchart of a process for forming a main weld path with a small gap; Fig. 8 a flowchart of a process for forming a large-spaced main weld path; and Fig. 9 a schematic sectional view of the welded section. DETAILED DESCRIPTION OF EXAMPLE EXECUTIONS[1. First embodiment][1-1. Design]

[0017] A welding method of the present embodiment comprises a welding process for welding an upper plate and a lower plate overlapping with the upper plate by irradiating a surface of the upper plate with a laser beam.

[0018] In the welding process of the present embodiment, welding is carried out using a welding device 10 which is located in Fig. Figure 1 shows the welding device 10, which comprises an oscillator 12, a mirror 13, a motor 14 and a control unit 15.

[0019] In the welding process of the present embodiment, an upper plate 3 and a lower plate 2 are mounted at an angle with respect to a horizontal plane, viewed parallel to a welding feed direction (i.e., a direction normal to the paper). Fig. 1) In particular, the upper plate 3 and the lower plate 2 are rotated away from a horizontal plane about a roll axis parallel to the welding feed direction. An inclination angle (i.e., a roll angle) α of the upper plate 3 and the lower plate 2 with respect to the horizontal plane is greater than 0° and less than 90°.

[0020] The oscillator 12 generates a laser beam that applies energy to an upper surface of the upper plate 3 (i.e., a base material surface) that overlaps with the lower plate 2. Examples of a usable supply source for the laser beam include carbon dioxide gas (CO2). The mirror 13 directs a path of the laser beam generated by the oscillator 12 and irradiates the surface of the upper plate 3 with the laser beam. The motor 14 is mounted on the mirror 13 and is configured to change the angle of the mirror 13.

[0021] The controller 15 sets the irradiation position and energy level of the laser beam on the surface of the upper plate 3. Specifically, the controller 15 sets the irradiation position of the laser emitter by changing the angle of the mirror 13 using the motor 14. Furthermore, the controller 15 adjusts the energy level of the laser beam by varying the output of the oscillator 12.

[0022] The following describes a specific procedure for setting up the welding device 10. As in Fig. As described in 1, an operator first enters a laser output (laser power output target value) and a welding speed directly into the welding device 10 within a program (step S1).

[0023] In parallel to step S1, the operator can visually determine a welding position and teach it to the welding device 10, thereby automatically generating a welding position within the program (step S2). The operator can also determine (generate) the welding position by numerical input (step S3).

[0024] Control 15 generates a coordinate system (step S4) based on the inputs executed in step S2 and / or step S3. It is also possible to select and execute only one of the two steps, S2 or S3.

[0025] Based on the input in step S1 (i.e., the laser output and the welding speed) and the coordinate system generated in step S4, the controller 15 generates a movement pattern of the welding device 10 as a whole by means of a motion control (step S5).

[0026] Based on the motion pattern generated in step S5, the controller 15 sends a laser output command to the oscillator 12 (step S6). Additionally, the controller 15 sends an irradiation position command to a processing head comprising the mirror 13 and the motor 14 (step S7). Steps S6 and S7 are interconnected. <Schweißstruktur>

[0027] Welding using the welding device 10 results in the formation of a weld structure 1, which is in Fig. 2A is shown. The welded structure 1 is a structure with two metal plates welded together in one thickness direction. The welded structure 1 comprises the lower plate 2 (comprising a first surface 2A, which is an upper surface of the lower plate 2, and comprising a second surface 2B, which is a lower surface of the lower plate 2), the upper plate 3 (comprising a third surface 3A, which is an upper surface of the plate 3, and comprising a fourth surface 3B, which is a lower surface of the upper plate 3), a main weld section 4, and a weld bead 6.

[0028] The application of the weld structure 1 is not limited in particular as long as metal plates are welded together. The weld structure 1 can, for example, be appropriately used for mounting structures for automotive parts, such as for instrument panel reinforcement.

[0029] Examples of materials for the lower plate 2 can include iron, iron alloys such as steel, aluminum, or aluminum alloy. The thickness of the lower plate 2 is not specifically limited. Examples of materials for the upper plate 3 can include those listed as materials for the lower plate 2. The materials of the upper plate 3 and the lower plate 2 can be identical or different.

[0030] A section of the upper plate 3 overlaps with the first surface 2A of the lower plate 2 (an upper surface in Fig. 2A). The upper plate 3 can be a thin plate with an average thickness of 1 mm or less in an overlapping area O where it overlaps with the lower plate 2. The upper plate 3 can overlap completely with the lower plate 2. The average thickness of the upper plate 3 outside the overlapping area O can be greater than 1 mm.

[0031] In a welded section, the main weld section 4 is a section where the metals representing the lower plate 2 and the upper plate 3 are melted and solidified due to heat input from the laser beam. The weld bead 6 is formed around the main weld section 4. As shown in Fig. As shown in 2B, the main weld section 4 comprises a circular part 4A and a wave-shaped part 4B.

[0032] The circular part 4A in the main welding section 4 is generated by an auxiliary welding path 41 of the laser beam, shown in Fig. 3A. The wave-shaped part 4B of the main welding section 4 is generated by a main welding path 42 of the laser beam.

[0033] The welding process in the welding method of the present embodiment comprises a process for forming an auxiliary welding path 41, a process for forming a main welding path 42, and a re-irradiation process to stop the irradiation with the laser beam after forming the main welding path 42, and then performing re-irradiation. <Prozess zum Bilden eines Hilfsschweißpfads>

[0034] This process, which is formed prior to the process for forming the main weld path, is represented by the auxiliary weld path 41, which is continuous and comprises a reciprocating or circular path, or by a plurality of auxiliary weld paths 41. In the present embodiment, as shown in Fig. Figure 3A shows the auxiliary welding path 41 formed with a circular shape, which is a circular path. The “circular shape” is a concept encompassing an approximately spiral shape whose diameter decreases or increases along a circumferential direction.

[0035] For example, the auxiliary welding path 41 is formed with a circular shape by first mapping a semicircle with a specified diameter from a starting point S of the irradiation with the laser beam along a welding feed direction L, secondly mapping a semicircle with a slightly larger diameter towards the starting point S, and then mapping a semicircle with an even larger diameter along the welding feed direction L.

[0036] The occurrence of voids can be reduced by applying the circular path in a non-overlapping manner, as previously described. Furthermore, forming the path in a circular shape facilitates the creation of a chamber C for molten metal. Thus, the molten metal can be adequately supplied to the main welding path 42.

[0037] As in Fig. As shown in Figure 3B, the auxiliary weld path 41 can have an approximately rectangular shape (generated by line segments). Alternatively, the auxiliary weld path 41 can have a polygonal shape, different from the rectangular shape. Furthermore, the auxiliary weld path 41 can be a linear path that runs back and forth in the specified directions. <Prozess zum Bilden des Hauptschweißpfads>

[0038] In this process, after the formation of the auxiliary welding path 41, the main welding path 42 is formed, which intersects the welding feed direction L and includes many turning points.

[0039] As in Fig. As shown in Figure 3A, a starting point of the main weld path 42 is an endpoint Q3 of the auxiliary weld path 41. That is, the main weld path 42 is continuous with the auxiliary weld path 41. As shown in Fig. As shown in Figure 3C, the main weld path 42 is designed to turn in directions that intersect the weld feed direction L, so that it crosses a center line M parallel to the weld feed direction L.

[0040] In the present embodiment, the main weld path 42 has a triangular wave shape. Alternatively, the main weld path 42 can be assumed to have a shape in which it gently curves at the tops of the triangular wave shapes or has a sinusoidal wave shape.

[0041] The main weld path 42 is formed by welding the third surface 3A of the upper plate 3 (an upper surface in Fig. 2A), which is a side opposite the lower plate 2, is irradiated with the laser beam while being pendulum welded with respect to the welding feed direction L.

[0042] The main weld path 42 comprises an initial region 42A, which is continuous from the auxiliary weld path 41, and a subsequent region 42B, which is located further forward in the weld feed direction L than the initial region 42A. A subsequent turning distance P2 in the subsequent region 42B is greater than an initial turning distance P1 in the initial region 42A.

[0043] Here, the "turnover distance" means the length in the welding feed direction L of one cycle (i.e., one wavelength) of the path in each region. Specifically, the turnover distance is the distance between the two most distant intersection points of three adjacent intersection points where the path in each region intersects the center line M.

[0044] As previously described, the initial turning distance P1 in the initial region 42A is smaller than the subsequent turning distance P2 in the subsequent region 42B. As in Fig. As shown in Figure 3A, this reduces the distance between the molten metal chamber C and an inflection point Q1 (an initial inflection point) on a vertically upper side of the main weld path 42. Consequently, the supply of molten metal from chamber C to the inflection point Q1 is facilitated. Furthermore, the auxiliary weld path 41 and the initial region 42A can be formed as a single piece (not separated by a gap).

[0045] In the present embodiment, the main weld path 42 in the initial region 42A has a length of one cycle, encompassing the initial turning points Q1 and Q2. That is, the length of the initial region 42A in the welding feed direction L is equal to the initial turning distance P1 in the initial region 42A.

[0046] The main weld path 42 in the subsequent region 42B has multiple cycles. The subsequent region 42B is a region that extends from an endpoint Q4 in the initial region 42A to a welding endpoint F. In the present embodiment, the length of the subsequent region 42B in the welding feed direction L is an integer multiple of the subsequent turning distance P2 in the subsequent region 42B.

[0047] In the present embodiment, the amount of energy applied by the laser beam to the vertically upper side in a region R1 in the vicinity of the inflection point Q1 is designed to be greater than the amount of energy applied by the laser beam to a vertically lower side in a region R2 in the vicinity of the inflection point Q2.

[0048] In particular, the welding speed in region R1, in the vicinity of inflection point Q1 on the vertically upper side, is designed to be lower than the welding speed in region R2, in the vicinity of inflection point Q2 on the vertically lower side. In other words, the irradiation time of the laser beam in region R1, in the vicinity of inflection point Q1 on the vertically upper side, is designed to be longer than the irradiation time of the laser beam in region R2, in the vicinity of inflection point Q2 on the vertically lower side.

[0049] As in Fig. As shown in Figure 4, this makes the amount of energy applied to the vertically upper side of the main welding path 42 in the neighborhood of inflection point Q1 greater than the amount of energy applied to the vertically lower side at inflection point Q2.

[0050] As a means of varying the welding speed in the vicinity of each inflection point, as before, a timer can be used. Specifically, the welding speed in region R1 in the vicinity of inflection point Q1 on the vertically upper side can be set lower than the welding speed in region R2 in the vicinity of inflection point Q2 on the vertically lower side by stopping the movement of the laser beam for a specified period in region R1 in the vicinity of inflection point Q1 on the vertically upper side, while the laser beam irradiation continues.

[0051] The time period during which the laser beam is stopped using the timer can be set, for example, to 0.01 seconds or longer and 1 second or shorter. The output of the laser beam can be varied while its movement is stopped.

[0052] Furthermore, in the present embodiment, the amount of energy applied in regions R1 and R2 in the vicinity of inflection points Q1 and Q2 can be less than the amount of energy in regions not in the vicinity of inflection points Q1 or Q2. This can reduce the occurrence of hole openings due to excessive penetration at inflection points Q1 and Q2.

[0053] In particular, as in Fig. Figure 4 shows that the welding speed in area R1 in the vicinity of inflection point Q1 on the vertical upper side and the welding speed in area R2 in the vicinity of inflection point Q2 on the vertical lower side are designed to be higher than the welding speed in areas other than areas R1 and R2. <Erneuter Bestrahlungsprozess>

[0054] In this process, the laser beam irradiation is stopped at the end point F of the welding, and then the laser beam is re-irradiated at the end point F.

[0055] The interval between stopping and restarting radiation can be set to, for example, 0.05 seconds or longer and 2 seconds or shorter. The interval for re-irradiation can also be set to, for example, 0.05 seconds or longer and 2 seconds or shorter.

[0056] The laser beam output at the time of re-irradiation can be varied from the output during welding (i.e., during the formation of the main weld path 42), for example, by defocusing or the like. However, it is preferable to set the same output as during welding.

[0057] As in Fig. As shown in Figure 5, the laser beam irradiation is stopped at time T1, and the irradiation is resumed at time T2. This extends the cooling period at the terminal point F and delays the end of the period from time T3 to time T4. This allows the terminal point F to cool slowly, thus reducing the occurrence of solidification cracks. <steuerung>

[0058] The following describes a process performed by the welding device 10 to achieve the welding process of the present embodiment, with reference to a flowchart in Fig. 6 described.

[0059] First, the welding device 10 forms the auxiliary welding path 41 using the oscillator 12 and the motor 14 (step S10). After forming the auxiliary welding path 41, the welding device 10 performs a process to form a main welding path with a small gap in Fig. 7 out (step S20).

[0060] In the process of forming the main welding path with a small distance, the welding device 10 first sets a welding distance at a small distance (i.e. the initial turning distance P1 of the initial region 42A) (step S110).

[0061] Next, the welding device 10 locates the current irradiation position and determines whether the current irradiation position is in the vicinity of the inflection point Q1 or Q2 (step S120). If the current irradiation position is in the vicinity of the inflection point Q1 or Q2 (S120: YES), the welding device 10 issues a command to switch the welding speed to a high-speed mode or a command to maintain the high-speed mode (step S130).

[0062] If, on the other hand, the current irradiation position is not in the vicinity of inflection point Q1 or Q2 (S120: NO), the welding device 10 issues a command to switch the welding speed to a low-speed mode or a command to maintain the low-speed mode (step S140).

[0063] The welding device 10 repeatedly controls the welding speed until the irradiation position reaches the turning point Q1 (step S150). After the irradiation position has reached the turning point Q1, the welding device 10 stops at the turning point Q1 for a specified period using the timer, while continuing irradiation with the laser beam (step S160).

[0064] After the specified time has elapsed, the welding device 10 again determines whether the current irradiation position is in the vicinity of the turning point Q1 or Q2 while welding at close range (step S170) and performs a shift between the high-speed mode (step S180) and the low-speed mode (step S190). When the irradiation position reaches the endpoint Q4 of the initial region 42A, the welding device 10 terminates the process of forming the main weld path at close range (step S200).

[0065] After completing the process for forming the small-distance main weld path, the welding device 10 performs a process for forming a large-distance main weld path in Fig. 8 out (step S30).

[0066] In the process of forming the main weld path with a large distance, the welding device 10 first sets the weld distance at a large distance (i.e. the subsequent turning distance P2 in the subsequent region 42B) (step S210).

[0067] Next, the welding device 10 locates the current irradiation position and determines whether the current irradiation position is in the vicinity of the inflection point Q1 or Q2 (step S220). If the current irradiation position is in the vicinity of the inflection point Q1 or Q2 (S220: YES), the welding device 10 issues a command to shift the welding speed to a high-speed mode or a command to maintain the high-speed mode (step S230).

[0068] If, on the other hand, the current irradiation position is not in the vicinity of inflection point Q1 or Q2 (S220: NO), the welding device 10 issues a command to switch the welding speed to a low-speed mode or a command to maintain the low-speed mode (step S240).

[0069] The welding device 10 repeatedly controls the welding speed until the irradiation position reaches the turning point Q1 (step S250). After the irradiation position has reached the turning point Q1, the welding device 10 stops at the turning point Q1 for a specified period using the timer, while continuing irradiation with the laser beam (step S260).

[0070] After the specified period has elapsed, the welding device 10 again determines whether the current irradiation position is in the vicinity of the turning point Q1 or Q2 while welding at a large distance (step S270) and performs a shift between the high-speed mode (step S280) and the low-speed mode (step S290). If the irradiation position reaches an endpoint Q5 at any cycle of the main weld path 42, the welding device 10 terminates the process of forming the main weld path at a large distance (step S300).

[0071] After completion of each cycle of the process for forming the main weld path with a large gap, the welding device 10 determines whether the irradiation position has reached the end point F of the welding (step S40 in Fig. 6) If the irradiation position does not reach the endpoint F (S40: NO), the welding device 10 repeats the process to form the main weld path at a large distance.

[0072] When the irradiation position reaches the endpoint F (S40: YES), the welding device 10 stops the irradiation with the laser beam (step S50). After a specified period of time, the welding device 10 performs another irradiation with the laser beam (step S60). <Querschnitt der Schweißstruktur>

[0073] A cross-section of the welded structure obtained by the welding process of the present embodiment is shown in Fig. 9 shown. Fig. Figure 9 illustrates the weld structure, which is welded in an inclined state, with the right side of it in Fig. 9 is positioned vertically at the top. The outline arrow in the drawing indicates the direction of irradiation with the laser beam.

[0074] In the welded structure of Fig. 9. There are no voids (i.e., cavities) within the main weld section 4. Molten metal 5, which constitutes the main weld section 4, is formed more on the vertically upper side than on the vertically lower side. In other words, a greater amount of molten metal is generated on the vertically upper side, thus compensating for the molten metal that runs downwards due to gravity.

[0075] The molten metal 5 penetrates the upper plate 3 and reaches the interior of the lower plate 2 and then the second surface 2B (a lower surface in Fig. 9), which is located on a side opposite the upper plate 3. The upper plate 3 and the lower plate 2 are welded together in the thickness direction thereof via the main weld section 4, which is welded on an inner surface of the upper plate 3 and on an inner surface of the lower plate 2.

[0076] The third surface 3A (i.e., a weld surface) of the upper plate 3, located on the opposite side from the lower plate 2, and an (upper) exposed surface 4C of the main weld section 4 in the upper plate 3 are continuous. That is, in the cross-section perpendicular to a longitudinal direction (i.e., the weld feed direction) of the main weld section 4, there are no steps in the thickness direction at joints between the upper plate 3 and the main weld section 4. The longitudinal direction of the main weld section 4 is a pendulum weld feed direction (i.e., a direction parallel to a line connecting the centers in the pendulum weld).

[0077] The (upper) exposed surface 4C of the main weld section 4 is bent in a concave shape, recessed in the thickness direction of the upper plate 3. In other words, the exposed surface 4C acts like a bridge between two ends on the third surface 3A of the upper plate 3, spaced apart from the molten metal 5, and connects these ends uniformly.

[0078] As in Fig. As shown in Figure 9, the main weld section 4 within the upper plate 3 increases in width from the third surface 3A of the upper plate 3 towards an inner side in the thickness direction (i.e., as it gets closer to the lower plate 2). However, this increase in the width of the main weld section 4 within the upper plate 3 is not significant.

[0079] Furthermore, the width of the main weld section 4 within the lower plate 2 decreases from the first surface 2A of the lower plate 2 towards an outer surface in the thickness direction (i.e., when spaced from the upper plate 3). A lower surface 4D of the main weld section 4, exposed by the lower plate 2, has a smaller width in a direction perpendicular to the thickness direction than the exposed surface 4C of the main weld section 4 in the upper plate 3.

[0080] As in Fig. As shown in Figure 9, there is a gap D in an overlap direction between the fourth surface 3B of the upper plate 3 (a lower surface in Fig. 9), which faces the lower plate 2, and the first surface 2A of the lower plate 2. If this gap D becomes too large, the weld strength may be insufficient. The gap D between the upper plate 3 and the lower plate 2 is not necessarily required. [1-2. Effects]

[0081] The embodiment discussed in detail above offers the following effects. (1a) In the vicinity of inflection point Q1 on the vertically upper side, where the molten metal tends to flow downwards, a greater amount of energy is applied than in the vicinity of inflection point Q2 on the vertically lower side. This facilitates the reduction of excessive melting in the vicinity of inflection point Q2 on the vertically lower side and also allows for the compensation of insufficient molten metal in the vicinity of inflection point Q1 on the vertically upper side. Consequently, weld quality can be improved. Furthermore, the inclined mounting of the upper plate 3 and the lower plate 2 can increase the design tolerance of products and clamping devices. (1b) The movement of the laser beam is stopped for the specified period in the area R1 in the vicinity of inflection point Q1 on the vertically upper side, while the irradiation with the laser beam continues. This reduces the welding speed in the vicinity of inflection point Q1 on the vertically upper side, thereby enabling simple and reliable adjustment of the amount of energy in the vicinity of inflection points Q1 and Q2. (1c) The laser beam irradiation is stopped at the end point of the welding process, and then the irradiation is repeated. This allows for slow cooling at the end point of the welding process. Consequently, the occurrence of solidification cracks at the end point of the welding process can be reduced. (1d) The molten metal is generated in the auxiliary welding path 41, and the molten metal can be fed to the main welding path 42. This can reduce the formation of a gap due to insufficient molten metal in the main welding path 42. (1e) The main weld path 42 comprises the initial region 42A and the subsequent region 42B, which has a larger turning distance than the initial region 42A. This makes it possible to effectively utilize the molten metal in the vicinity of the starting point of the main weld path 42 and also to aim for a reduction in the time required for the process of forming the main weld path 42. [2. Other embodiments]

[0082] The embodiment of the present disclosure has been described as far as possible; however, the present disclosure is not limited to the embodiment mentioned above and can take various forms.

[0083] (2a) In the welding process of the aforementioned embodiment, the amount of energy applied in the neighborhood of the inflection point Q1 on the vertically upper side can be designed to be greater than the amount of energy applied in the neighborhood of the inflection point Q2 on the vertically lower side by controlling the output of the laser beam or the focus of the laser beam instead of, or in combination with, the welding speed.

[0084] When adjusting the welding speed at inflection point Q1, the movement of the laser beam does not necessarily have to be stopped for the specified period. In particular, the welding speed at inflection point Q1 can be set by a controller that reduces the welding speed.

[0085] Furthermore, instead of the amount of energy applied in region R1 in the neighborhood of inflection point Q1 on the vertically upper side being greater than the amount of energy applied in the other regions, the amount of energy applied in region R2 in the neighborhood of inflection point Q2 on the vertically lower side can be designed to be smaller than the amount of energy applied in the other regions.

[0086] (2b) In the welding process of the aforementioned embodiment, the main welding path 42 need not necessarily include the initial region 42A and the subsequent region 42B. In particular, the turning distance of the main welding path 42 can be constant.

[0087] (2c) In the welding process of the aforementioned embodiment, the process for forming an auxiliary welding path is not an essential process. Thus, welding can be started from the starting point of the main welding path 42. Furthermore, the process of re-irradiation is also not an essential process and can therefore be omitted.

[0088] (2d) In the welding process of the aforementioned embodiment, the amount of energy supplied in the regions R1 and R2 in the vicinity of the inflection point Q1 and Q2 respectively need not necessarily be less than the amount of energy supplied in the regions other than in the vicinity of the inflection points Q1 and Q2.

[0089] (2e) The function(s) performed by a single element in the aforementioned embodiment can be performed by many different elements. The function(s) performed by many different elements can be performed by a single element. Part of the design of the aforementioned embodiments can be omitted. At least part of the design of the aforementioned embodiments can be added to or replaced by the design of the aforementioned other embodiments. All modes encompassed in the technical concept specified by enumerations in the accompanying claims are embodiments of the present disclosure.< / steuerung>

Claims

[1] Welding method comprising welding an upper plate (3) and a lower plate (2) overlapping with the upper plate (3) by irradiating a surface (3A) of the upper plate (3) with a laser beam, wherein the welding comprises forming a main weld path (42) that intersects a weld feed direction and includes inflection points on a vertically upper side and on a vertically lower side, wherein the upper plate (3) and the lower plate (2), viewed parallel to the welding feed direction, are mounted in an inclined manner with respect to a horizontal plane, and wherein, during the formation of the main welding path (42), while the irradiation with the laser beam continues, the movement of the laser beam is stopped for a specified period of time in an area near the inflection points on the vertically upper side, such that a welding speed in the area near the inflection points on the vertically upper side is made smaller than a welding speed in an area near the inflection points on the vertically lower side, and an amount of energy applied by the laser beam in the area in the vicinity of the inflection points on the vertically upper side is made greater than an amount of energy applied by the laser beam in the area in the vicinity of the inflection points on the vertically lower side, wherein the area near the inflection points on the vertically upper side is closer to the inflection points on the vertically upper side than to a centerline parallel to the welding feed direction, the centerline being located between the vertically upper side and the vertically lower side, and where the area near the inflection points on the lower vertical side is closer to the inflection points on the lower vertical side than to the center line. [2] Welding method according to claim 1, wherein the welding further comprises stopping the irradiation with the laser beam after forming the main welding path (42) and then performing renewed irradiation. [3] Welding method comprising welding an upper plate (3) and a lower plate (2) overlapping the upper plate (3) by irradiating the surface (3A) of the upper plate (3) with a laser beam, wherein the welding comprises forming a main weld path (42) that intersects the weld feed direction and has inflection points on a vertically upper side and a vertically lower side, wherein the upper plate (3) and the lower plate (2), viewed parallel to the welding feed direction, are arranged in an inclined manner with respect to a horizontal plane, and wherein, when forming the main welding path (42) from the laser beam in a region, an amount of energy applied by the laser beam near the inflection points on the vertically upper side is greater than an amount of energy applied by the laser beam in a region near the inflection points on the vertically lower side, wherein the area near the inflection points on the vertically upper side is closer to the inflection points on the vertically upper side than to a center line parallel to the welding feed direction, which is located between the vertically upper side and the vertically lower side, where the area near the inflection points on the vertically lower side is closer to the inflection points on the vertically lower side than to the center line, and wherein the welding further comprises forming an auxiliary welding path (41) which is continuous and includes a reciprocating or circular path prior to forming the main welding path (42). [4] Welding method according to claim 3, wherein the auxiliary welding path (41) has a circular shape. [5] Welding method according to claim 3 or 4, wherein the main welding path (42) comprises: an initial region (42A) extending continuously from the auxiliary welding path (41); and a subsequent region (42B) which is located on a more forward side of the welding feed direction than the initial region (42A) and which has a larger turning distance than the initial region (42A).

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