Method for laser welding a workpiece

Abstract

In the past, there has been a problem that a cladding member inserted between base materials is gasified by heating of laser, and thereby the cladding member is mixed into the melted base materials to generate a bubble in the inside of the base materials. In a method of laser welding a workpiece (W1) and a workpiece (W2), a laser (LB) is generated and irradiated to the workpiece (W1), and by oscillating an irradiation point (P) of the laser (LB) in a heating region, which is a region determined on the workpiece (W1) so as to include a welding site at which laser welding should be performed, an overlapping surface region of the workpiece (W1) and the workpiece (W2) corresponding to the heating region is heated to a temperature above a boiling point of a cladding member of the workpiece (W1) and lower than a melting point of a base material of the workpiece (W1), and by gasifying the cladding member by heating thereof, a gap is formed between the workpiece (W1) and the workpiece (W2), the cladding member is discharged to an outside of the overlapping surface region via the gap, and the base material of the workpiece (W1) and the base material of the workpiece (W2) are melted at the welding site to weld the workpiece (W1) and the workpiece (W2) to each other.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a method of laser welding workpieces. BACKGROUND

[0002] A method of laser welding a pair of workpieces (galvanized steel sheets) overlapped in a manner that a clad member (galvanizing) is interposed between the pair of workpieces is known (for example, Patent Literature 1).

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: International Publication No. 2015 / 104781 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Conventionally, there is a problem that a clad member interposed between base materials is gasified by heating of laser, and thereby the clad member is mixed into the molten base materials to generate a bubble in the inside of the base materials.

[0008] SOLUTION TO PROBLEM

[0009] In one embodiment of the present disclosure, in a method of laser welding a first workpiece and a second workpiece, the first workpiece and the second workpiece are overlapped in a manner that they face each other, the first workpiece and the second workpiece each have a base material, and at least one of the first workpiece and the second workpiece has a clad member interposed between the base material of the first workpiece and the base material of the second workpiece, in the method, laser is generated by a laser oscillator, and the laser is irradiated to the first workpiece, a region of an overlapped surface of the first workpiece and the second workpiece corresponding to a heating region is heated to a temperature above a boiling point of the clad member and lower than a melting point of the base material of the first workpiece by oscillating an irradiation point of the laser in the heating region, the heating region is a region determined in a manner that the first workpiece includes a welding site at which laser welding is to be performed, the clad member of the region of the overlapped surface is gasified by heating, thereby forming a gap between the first workpiece and the second workpiece, the clad member is discharged to an outside of the region of the overlapped surface through the gap, and after the clad member is discharged to the outside of the region of the overlapped surface, the laser is irradiated to the welding site, and the base material of the first workpiece and the base material of the second workpiece are molten at the welding site to weld the first workpiece and the second workpiece to each other.

[0010] EFFECT OF THE INVENTION

[0011] According to this disclosure, the cladding can be discharged from the overlapping area through the gap, thus reliably removing the cladding from the area where the base material is molten. Therefore, it is possible to prevent bubbles generated by the vapor of the cladding from mixing into the interior of the base material when it is melted at the weld joint. Furthermore, it is not necessary to form through holes in the base material for releasing the vapor of the cladding to the outside, thus simplifying the welding process. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a laser welding system according to one implementation method.

[0013] Figure 2 yes Figure 1 The diagram shows a block diagram of a laser welding system.

[0014] Figure 3 yes Figure 1 An example of a laser irradiation device and an irradiation point moving mechanism is shown.

[0015] Figure 4 yes Figure 1 The image shows an enlarged cross-sectional view of a pair of workpieces.

[0016] Figure 5 An example of a welded area and heated zone is shown.

[0017] Figure 6 An example of a teaching point set in a heating zone is shown.

[0018] Figure 7 This shows an example of a forward path for the movement of an irradiation point set in the heating zone.

[0019] Figure 8 This illustrates an example of the reverse path of the irradiation point movement path set in the heating area.

[0020] Figure 9 This illustrates an example of the movement path of the irradiation point set in the heating area.

[0021] Figure 10 This is a flowchart illustrating an example of a welding process performed by a laser welding system.

[0022] Figure 11 It is a diagram used to illustrate the overlapping area, and Figure 4 Correspondingly.

[0023] Figure 12 An example of a graph showing the temperature distribution in the overlapping area.

[0024] Figure 13 schematically showing through Figure 10 Step S2 in the process creates a gap between a pair of workpieces.

[0025] Figure 14 This is a schematic diagram of a laser welding system according to another embodiment.

[0026] Figure 15 yes Figure 14 The diagram shows a block diagram of a laser welding system.

[0027] Figure 16 It is shown by Figure 14 The flowchart shows an example of the welding process performed by the laser welding system.

[0028] Figure 17 Show Figure 16 An example of the process of step S2' in the process.

[0029] Figure 18 This shows another example of the movement path of the irradiation point set in the heating area.

[0030] Figure 19 This shows another example of the movement path of the irradiation point set in the heating area.

[0031] Figure 20 This illustrates an example of controlling the speed of the irradiation point and the laser power in a heating process. Detailed Implementation

[0032] Hereinafter, embodiments of the present disclosure will be described in detail based on the accompanying drawings. Furthermore, in the various embodiments described below, the same reference numerals will be used to label the same elements, and repeated descriptions will be omitted. Additionally, in the following description, the orthogonal coordinate system C1 in the figures will be used as the directional reference. For ease of explanation, the positive x-axis direction of coordinate system C1 will be referred to as the right, the positive y-axis direction as the front, and the positive z-axis direction as the top.

[0033] Reference Figure 1 and Figure 2 The following describes a laser welding system 10 according to one embodiment. The laser welding system 10 is a system for welding a pair of workpieces W1 and W2 using a laser. The laser welding system 10 includes a laser oscillator 12, a light guide member 14, a laser irradiation device 16, an irradiation device moving mechanism 18, an irradiation point moving mechanism 20, and a control device 22.

[0034] The laser oscillator 12 is a solid-state laser oscillator (e.g., a YAG laser oscillator or a fiber laser oscillator) or a gas laser oscillator (e.g., a carbon dioxide laser oscillator), etc. According to the instructions from the control device 22, it generates a laser LB internally through optical resonance and emits the laser LB out of the guide light member 14.

[0035] The light guide component 14 has optical elements such as an optical fiber, a light guide path made of hollow or transparent material, a reflector, or an optical lens, and is used to guide the laser LB generated by the laser oscillator 12 to the laser irradiation device 16. The laser irradiation device 16 is a laser scanner or laser processing head, etc., used to focus the laser LB incident from the light guide component 14 onto the workpiece W1.

[0036] The irradiation device moving mechanism 18 moves the laser irradiation device 16 relative to workpieces W1 and W2. For example, the irradiation device moving mechanism 18 is a vertical multi-joint robot capable of moving the laser irradiation device 16 to any position in coordinate system C1. Alternatively, the irradiation device moving mechanism 18 may also have multiple ball screw mechanisms that move the laser irradiation device 16 along the xy plane of coordinate system C1 and along the z-axis of coordinate system C1.

[0037] Coordinate system C1 is, for example, a world coordinate system that defines the three-dimensional space of the work unit, a moving mechanism coordinate system (e.g., a robot coordinate system) used to control the movement of the irradiation device moving mechanism 18, or a workpiece coordinate system that defines the coordinates of workpiece W1 and workpiece W2, etc. It is a control coordinate system used to automatically control the movement of each movable component (i.e., the irradiation device moving mechanism 18 and the irradiation point moving mechanism 20) of the laser welding system 10.

[0038] The irradiation point moving mechanism 20 moves the irradiation point P on the workpiece W1 relative to the workpiece W1 when the laser irradiation device 16 irradiates the workpiece W1 with laser LB. Specifically, the irradiation point moving mechanism 20 includes optical elements such as a reflector or optical lens, a drive device for driving the optical elements, or a worktable for moving the workpiece W1 and workpiece W2, and moves the irradiation point P relative to the workpiece W1 by actuating these components.

[0039] The control device 22 controls the operation of the laser oscillator 12, the laser irradiation device 16, the irradiation device moving mechanism 18, and the irradiation point moving mechanism 20. Specifically, the control device 22 is a computer having a processor 50, a memory 52, and an I / O interface 54. The processor 50 may have a CPU or GPU, and it is communicatively connected to the memory 52 and the I / O interface 54 via a bus 56. While communicating with the memory 52 and the I / O interface 54, the processor 50 performs computational processing to implement the various functions described later.

[0040] The memory 52 has RAM or ROM, etc., to temporarily or permanently store various data. The I / O interface 54 has, for example, an Ethernet port, a USB port, a fiber optic connector, or an HDMI terminal, and communicates with external devices in a wired or wireless manner under the instructions from the processor 50.

[0041] The control device 22 includes an input device 58 and a display device 60. The input device 58 has a keyboard, mouse, or touch panel, etc., for receiving data input from the operator. The display device 60 has a liquid crystal display or organic EL display, etc., for displaying various data. The laser oscillator 12, laser irradiation device 16, irradiation device moving mechanism 18, irradiation point moving mechanism 20, input device 58, and display device 60 are connected to the I / O interface 54 via wired or wireless communication.

[0042] Next, refer to Figure 3 To illustrate one embodiment, we will describe the laser irradiation device 16 and the irradiation point moving mechanism 20. Figure 3 The laser irradiation device 16 shown is a laser scanner, having a main body 24, a light-receiving part 26, an optical lens 28, a lens driving device 30, and an emission part 32. The main body 24 is hollow, and the propagation path of the laser LB is divided inside it. The light-receiving part 26 is provided in the main body 24 for receiving the laser LB propagating in the light guide member 14.

[0043] The optical lens 28 includes a focusing lens and is used to focus the laser LB. In this embodiment, the optical lens 28 is supported inside the main body 24 in a manner that allows it to move along the optical axis O of the laser LB incident on the optical lens 28. The lens driving device 30 includes a piezoelectric element, an ultrasonic transducer, or an ultrasonic motor, etc., and according to the command from the control device 22, the lens driving device 30 moves the optical lens 28 in the direction of the optical axis O, thereby shifting the focal point of the laser LB irradiating the workpiece W1 in the direction of the optical axis O. The emission section 32 emits the laser LB focused by the optical lens 28 to the outside of the main body 24.

[0044] The main body 24 also houses a reflector 34 and a reflector 36, a reflector drive device 38, and a reflector drive device 40. The reflector 34 (first reflector) is supported inside the main body 24 in a manner that allows it to rotate about axis A1. The reflector 34 is positioned on the optical path O of the laser LB that enters the interior of the main body 24 via the light receiving part 26, and is used to reflect the laser LB toward the reflector 36.

[0045] The mirror drive device 38, for example a servo motor, rotates the mirror 34 about axis A1 according to instructions from the control device 22. In this way, the mirror drive device 38 changes the orientation of the mirror 34 by rotating it, thereby changing the reflection direction of the laser LB reflected by the mirror 34.

[0046] On the other hand, the reflector 36 (second reflector) is supported inside the main body 24 in a manner that allows it to rotate about axis A2. Axis A2 is approximately orthogonal to axis A1. The reflector 36 is positioned on the optical path O of the laser LB reflected by the reflector 34, and is used to reflect the laser LB toward the optical lens 28.

[0047] The mirror drive device 40, for example a servo motor, rotates the mirror 36 about axis A2 according to instructions from the control device 22. In this way, the mirror drive device 40 changes the orientation of the mirror 36 by rotating it, thereby changing the reflection direction of the laser LB reflected by the mirror 36. Generally, mirrors 34 and 36 are referred to as galvano-mirrors, and mirror drive devices 38 and 40 are referred to as galvano-motors.

[0048] As described above, the laser LB incident from the light-receiving part 26 into the interior of the main body 24 is reflected by the reflectors 34 and 36, then focused by the optical lens 28 and emitted through the emission part 32 to the outside, irradiating the workpiece W1. The control device 22 operates the reflector drive device 38 and the reflector drive device 40 to change the orientation of the reflectors 34 and 36 respectively, thereby moving the irradiation point P of the laser LB irradiating the workpiece W1 relative to the workpiece W1. That is, in this embodiment, the reflectors 34 and 36, as well as the reflector drive device 38 and the reflector drive device 40, constitute the irradiation point moving mechanism 20.

[0049] Next, the method of laser welding workpieces W1 and W2 using laser welding system 10 will be described. For example... Figure 1 and Figure 4 As shown, workpieces W1 and W2 are flat plate-shaped components. They overlap in a manner that allows their surfaces to contact each other and are fixed by a fixture (not shown). In this embodiment, workpieces W1 and W2 are positioned at known locations in coordinate system C1, approximately parallel to the xy plane of coordinate system C1.

[0050] Workpiece W1 has a base material 100 and a covering 102 laminated onto the surface of the base material 100. The base material 100 is a flat plate member made of metal (e.g., iron), having an upper surface 104 and a lower surface 106 opposite to the upper surface 104. In this embodiment, the covering 102 is laminated onto the surface of the base material 100 in such a way that it covers the entire surface of the base material 100. The covering 102 has a first layer 102a covering the upper surface 104 of the base material 100 and a second layer 102b covering the lower surface 106 of the base material 100. The covering 102 is made of a different type of metal than the base material 100 (e.g., zinc).

[0051] Similarly, workpiece W2 has a base material 110 and a covering 112 laminated onto the surface of the base material 110. The base material 110 is a flat plate member made of metal (e.g., iron), having an upper surface 114 and a lower surface 116 opposite to the upper surface 114. In this embodiment, the covering 112 is laminated onto the surface of the base material 110 in such a way that it covers the entire surface of the base material 110. The covering 112 has a first layer 112a covering the upper surface 114 of the base material 110 and a second layer 112b covering the lower surface 116 of the base material 110. The covering 112 is made of a different type of metal than the base material 110 (e.g., zinc).

[0052] Furthermore, in this embodiment, the base material 100 and base material 110 are assumed to be the same type of metal (iron), and the cladding 102 and cladding 112 are the same type of metal (zinc) (for example, workpiece W1 and workpiece W2 are both galvanized steel sheets). The boiling point T1 of the cladding 102 and cladding 112 (approximately 900°C in the case of zinc) is lower than the melting point T2 of the base material 100 and base material 110 (approximately 1500°C in the case of iron).

[0053] Workpieces W1 and W2 are fixed in an overlapping manner, with the second layer 102b of the covering 102 and the first layer 112a of the covering 112 in surface contact with each other. For example... Figure 4 As shown, when workpieces W1 and W2 are fixed, the second layer 102b of the covering 102 and the first layer 112a of the covering 112 are inserted between the base material 100 and the base material 110.

[0054] As part of the preparatory process PP for welding workpieces W1 and W2, the operator sets the operating conditions CD for performing the welding operation on workpieces W1 and W2. These operating conditions CD include data on the welding area WL to be laser welded in the formal welding process WP (described later), and data on the heating area HA to be heated for workpiece W1 in the heating process HP (described later). See below for reference. Figures 5-9 This section explains how to set the welding area WL and the heating zone HA.

[0055] First, the operator sets the welding position WL for workpiece W1 in coordinate system C1. Figure 5 In the example shown, the welding area WL is defined by two teaching points TP1 and TP2 of the first layer 102a of the covering 102 of the workpiece W1 and the welding line LN connecting the teaching points TP1 and TP2. The teaching points TP1 and TP2 are the target positions for locating the irradiation point P of the laser LB in the formal welding process WP described later, and the welding line LN specifies the target path for moving the irradiation point P from the teaching point TP1 to the teaching point TP2.

[0056] For example, while visually confirming the CAD data of workpieces W1 and W2 displayed on the display device 60, the operator operates the input device 58 to specify teaching points TP1 and TP2 on the first layer 102a of workpiece W1. Based on the input data from the operator, the processor 50 sets the teaching points TP1 and TP2, as well as the welding line LN, in the coordinate system C1.

[0057] Next, the operator operates the input device 58 to set the heating zone HA in the first layer 102a in a manner that includes the welding area WL. Figure 5 In the example shown, the heating area HA is defined as a rectangular area that is recessed into the entire area of ​​the welding part WL, with its long side parallel to the x-axis of coordinate system C1 and its short side parallel to the y-axis of coordinate system C1.

[0058] More specifically, the heating region HA has a length x1 along its long side and a width y1 along its short side. As an example, the length x1 of the heating region HA can be set such that the left side SD1 of the heating region HA is positioned a distance x2 (e.g., 1 mm to 2 mm) to the left of the teaching point TP1, while the right side SD2 of the heating region HA is positioned a distance x3 (e.g., 1 mm to 2 mm) to the right of the teaching point TP2. Therefore, in this case, the length x1 of the heating region HA is longer than the length of the welding line LN along the x-axis of coordinate system C1.

[0059] Furthermore, the width y1 of the heating region HA can be set to be at least three times the width of the weld beads formed along the weld line LN when welding the base materials 100 and 110 in the formal welding process WP (described later) in the y-axis direction of coordinate system C1 (or the width of the laser LB irradiation point P during the formal welding process WP or heating process HP). Each vertex and each side of the heating region HA can be represented as the coordinates of coordinate system C1. Thus, the heating region HA is set in the first layer 102a in a manner that includes the welding part WL.

[0060] Next, the operator sets the teaching point TPn and the irradiation point movement path MP for the heating process HP in the heating area HA. ​​The teaching point TPn for the heating process HP is the target position for locating the irradiation point P of the laser LB in the heating process HP, as described later. The irradiation point movement path MP specifies the target path that should move the irradiation point P from the teaching point TPn to the teaching point TPn+1. Figure 6 The example shown is a setting of the teaching point TPn.

[0061] The operator operates the input device 58 to set teaching points TP11, TP12, TP13, TP14, TP15, and TP16 in the heating zone HA. Furthermore, in... Figure 6 For ease of understanding, the welding area WL has been omitted. Figure 6 In the example shown, teaching points TP11, TP12, TP15 and TP16 are respectively located at the vertices of the heating region HA, teaching point TP14 is located at the midpoint of edge SD1 of the heating region HA, and teaching point TP13 is located at the midpoint of edge SD2 of the heating region HA.

[0062] Next, the operator operates the input device 58, such as... Figure 7 As shown, the forward path of the illumination point movement path MP is set based on the teaching point TPn. Figure 7 In the example shown, the forward path of the illumination point movement path MP is set to the path of teaching point TP11→TP12→TP13→TP14→TP15.

[0063] Next, the operator operates the input device 58, such as... Figure 8 Set the reverse path of the illumination point movement path MP as shown. Figure 8 In the example shown, the reverse path of the illumination point movement path MP is set to the path TP15→TP16→TP13→TP14→TP11. Thus, as... Figure 9 As shown, the path MP of the irradiation point movement is set in the heating area HA as the teaching point TP11→TP12→TP13→TP14→TP15→TP16→TP13→TP14→TP11.

[0064] The teaching points TP11–TP16 and the irradiation point movement path MP are represented as coordinates in coordinate system C1. The position of the heating region HA in coordinate system C1 can be represented as the coordinates of the teaching points TP11–TP16 and the irradiation point movement path MP. Therefore, the heating region HA can be considered as the region divided by the teaching points TP11–TP16 and the irradiation point movement path MP.

[0065] As described above, the operator sets the welding area WL (teach points TP1 and TP2, welding line LN) and the heating area HA (teach points TP11 to TP16, irradiation point movement path MP) for workpiece W1. In addition, the operator can also set multiple welding areas WL and heating areas HA at various locations on workpiece W1.

[0066] The position data of the welding part WL (specifically, the coordinates of the teaching points TP1 and TP2 in coordinate system C1 and the welding line LN) and the position data of the heating area HA (specifically, the coordinates of the teaching points TP11 to TP16 in coordinate system C1 and the coordinates of the irradiation point movement path MP) are stored in memory 52 as working conditions CD.

[0067] In addition, the operating conditions CD also include the swing speed V1 (first speed) of the irradiation point P in the heating process HP, the laser power LP1 of the laser LB, and the time t for executing the heating process HP. HP The data includes the forward velocity V2 (second velocity) of the irradiation point P in the formal welding process WP, the laser power LP2 of the laser LB, the focal position FP of the laser LB in the heating process HP and the formal welding process WP, and the operating mode OM of the laser oscillator 12 in the heating process HP and the formal welding process WP.

[0068] The operating mode OM of the laser oscillator 12 includes, for example, a first operating mode OM1 for causing the laser oscillator 12 to generate a first type of laser LB1 and a second operating mode OM2 for causing the laser oscillator 12 to generate a second type of laser LB2 different from the first type. For example, the first type of laser LB1 is a pulsed oscillating laser, while the second type of laser LB2 is a continuously oscillating laser.

[0069] In the preparation process PP, the operator operates the input device 58 to set the speeds V1 and V2, the laser power LP1 and LP2, and the time t. HP The coordinates of the focal position FP in coordinate system C1 and the operating mode OM are used as the working conditions CD. Then, the operator uses the set working conditions CD (welding position WL, heating zone HA, speed V1 and speed V2, laser power LP1 and laser power LP2, time t) as the working conditions CD. HP The welding program PG is created using the focus position FP and the running mode OM.

[0070] The welding program PG is used to cause the processor 50 to execute the welding process described later. Figure 10The computer program specifies the parameters of the working conditions CD in the welding program PG. The generated welding program PG is stored in the memory 52 of the control device 22. Thus, the working conditions CD and the welding program PG are set in the preparation process PP.

[0071] Next, refer to Figure 10 To illustrate the welding process of the laser welding system 10. Figure 10 The welding process shown begins when the processor 50 receives a welding start command from an operator, a host controller, or a computer program (e.g., welding program PG). The processor 50 executes the welding program PG pre-stored in memory 52. Figure 10 The welding process is shown.

[0072] In step S1, the processor 50 actuates the irradiation device moving mechanism 18 to position the laser irradiation device 16 relative to workpieces W1 and W2 at the specified welding position P. W The laser irradiation device 16 is positioned at the welding location P. W At that time, the entire area of ​​the heating zone HA set for one welding part WL, which is the welding object, is within the movement range of the irradiation point moving mechanism 20 that moves the irradiation point P on the workpiece W1.

[0073] In step S2, the processor 50 executes the heating process HP. Specifically, the processor 50 first switches the operating mode OM of the laser oscillator 12 to the first operating mode OM1, and sends an instruction to the laser oscillator 12 to generate a first type of laser LB1 with laser power LP1. According to the instruction, the laser oscillator 12 generates the laser LB1 with laser power LP1 by pulse oscillation, and emits the laser LB1 to the laser irradiation device 16 via the light guide member 14.

[0074] At the same time, the processor 50 enables the lens drive device 30 of the laser irradiation device 16 to ( Figure 3 The optical lens 28 is adjusted by an action, thereby controlling the focus of the laser LB1 emitted from the laser irradiation device 16 at the focus position FP1. In this embodiment, the focus position FP1 is set at a position slightly above (or below) the upper surface of the workpiece W1 (that is, the upper surface of the first layer 102a of the covering 102).

[0075] Thus, laser LB1 with laser power LP1 is irradiated onto workpiece W1. At this time, the irradiation point P1 of laser LB1 has an area E1. This area E1 is proportional to the deviation of the focal position FP1 relative to the upper surface of workpiece W1. Furthermore, at this time, the irradiation point P1 can also be positioned at the teaching point TP11 of the heating zone HA.

[0076] Next, the processor 50 actuates the irradiation point moving mechanism 20 to cause the irradiation point P1 of the laser LB1 to oscillate within the heating zone HA at a speed V1. Specifically, the processor 50 actuates the mirror driving device 38 and the mirror driving device 40 to change the orientation of the mirrors 34 and 36 respectively, thereby causing the irradiation point P1 to move relative to the workpiece W1 at a speed V1.

[0077] For example, when the laser irradiation device 16 is positioned at welding position P W At that time, one of the reflectors 34 and 36 can change its orientation to shift the irradiation point P along the x-axis of coordinate system C1 within the heating area HA, and the other of the reflectors 34 and 36 can change its orientation to shift the irradiation point P1 along the y-axis of coordinate system C1 within the heating area HA.

[0078] The processor 50 causes the irradiation point P1 to repeatedly reciprocate along the aforementioned irradiation point movement path MP (the path from teaching point TP11→TP12→TP13→TP14→TP15→TP16→TP13→TP14→TP11) at a speed of V1 by changing the orientation of the reflectors 34 and 36 respectively. This causes the irradiation point P1 to oscillate within the heating area HA. ​​The speed V1 at this time is, for example, set to 200 m / min.

[0079] When the irradiation point P1 is oscillating at high speed within the heating region HA, the entire area of ​​the heating region HA is heated by the laser LB1. The heat generated in the heating region HA is transmitted through the base material 100 to the overlapping surface region SE of the workpieces W1 and W2, which is also heated.

[0080] Furthermore, the overlapping area SE is the area that includes the lower surface of the second layer 102b of the cover 102 and the upper surface of the first layer 112a of the cover 112, which are in surface contact with each other. For example, it can be defined as the area between the lower surface 106 of the base material 100 and the upper surface 114 of the base material 110 (or the occupied area of ​​the second layer 102b and the first layer 112a).

[0081] In this embodiment, the processor 50 causes the irradiation point P1 to cover the heating region HA for a time t. HP Continuous oscillation is used to heat the overlapping area SE', which corresponds to the heating area HA, in the overlapping area SE to a temperature T (T1≤T) above the boiling point T1 of the covering 102 (i.e., the covering 112) and lower than the melting point T2 of the base material 100 (i.e., the base material 110). <T2)。

[0082] The overlapping surface area SE' can be defined, for example, as the area obtained by projecting the heating area HA in the z-axis direction of the coordinate system C1 onto the overlapping surface area SE (in other words, the area in the overlapping surface area SE where the position and area are substantially the same as those of the heating area HA in the x-y plane of the coordinate system C1). In Figure 11 An example of the overlapping surface area SE' is schematically shown as a gray area.

[0083] In Figure 12 an example of a graph showing the temperature distribution in the y-axis direction of the overlapping surface area SE' heated in this step S2 is shown. Figure 12 y-coordinate: y α corresponds to the positions in the y-axis direction of the teaching point TP15 and the teaching point T16 in the coordinate system C1 ( Figure 9 ), y-coordinate: y β corresponds to the positions in the y-axis direction of the teaching point TP13 and the teaching point T14 in the coordinate system C1, y-coordinate: y γ corresponds to the positions in the y-axis direction of the teaching point TP11 and the teaching point T12 in the coordinate system C1.

[0084] By step S2, as Figure 12 shown, the temperature T of the overlapping surface area SE' is controlled to be within the temperature range above the boiling point T1 of the covering member 102 and lower than the melting point T2 of the base material 100 (T1 ≤ T < T2). In the present embodiment, during one reciprocation of the irradiation point P1 along the forward path ( Figure 7 ) and the reverse path ( Figure 8 ) of the irradiation point movement path MP, the irradiation point P1 passes through the path between the teaching point TP13 and the teaching point T14 in the irradiation point movement path MP twice, while passing through the other paths only once.

[0085] In other words, according to the irradiation point movement path MP, in step S2, the irradiation point P1 passes through the central part in the y-axis direction of the heating area HA more. As a result, the temperature of the central part of the heating area HA is the highest. Consequently, as Figure 12 shown, in the overlapping surface area SE', the temperature of the central part (the part where y = y β ) is also the highest.

[0086] When the overlapping surface area SE' is heated to a temperature T above the boiling point T1 and lower than the melting point T2, the second layer 102b of the covering member 102 and the first layer 112a of the covering member 112 existing in the overlapping surface area SE' are vaporized. The expansion pressure of the gas generated due to the vaporization of the covering member 102 and the covering member 112 at this time is very high.

[0087] Therefore, due to the expansion pressure of the covering 102 and 112 generated in the overlapping area SE', the upper surface 114 of the base material 110 is pushed downwards, and the lower surface 106 of the base material 100 is pushed upwards. As a result, the high-temperature base materials 100 and 110 undergo slight elastic deformation. This elastic deformation of the base materials 100 and 110 is reversible, and they return to their original shape when cooled.

[0088] Due to the vaporization of such covering parts 102 and 112, the elastic deformation of the base material 100 and 110 caused by such vaporization, and the thermal expansion of the base material 100 and 110 caused by heating, etc., Figure 13 As shown, this will create a gap G between a pair of workpieces W1 and W2. Furthermore, in Figure 13 For ease of understanding, the gap G is highlighted, but in reality, please understand that the gap G is a micrometer-scale dimension.

[0089] The vapors of the coatings 102 and 112 generated in the overlapping region SE' are radially blown outwards from the overlapping region SE' through the gap G. As a result, the second layer 102b of the coating 102 and the first layer 112a of the coating 112 present in the overlapping region SE' are discharged outwards from the overlapping region SE'.

[0090] Thus, in step S2, by heating the overlapping surface region SE' to a temperature T above the boiling point T1 and below the melting point T2, the base material 100 and base material 110 can be kept in a solid state, and the covering 102 and covering 112 can be discharged from the overlapping surface region SE'. In other words, the operating conditions CD used in step S2 (speed V1, laser power LP1, time t) HP The focus position FP1 and the operating mode OM1 are set to control the temperature T of the overlapping area SE' within a temperature range that is above the boiling point T1 and below the melting point T2.

[0091] The inventors conducted an experiment on galvanized steel sheets, namely workpieces W1 and W2, each with a thickness of 0.7 mm, performing step S2 under the following operating conditions CD.

[0092] [Work Conditions CD]

[0093] Heating area HA: Length x1 = 50 mm × Width y1 = 2 mm

[0094] Speed ​​V1 200 [m / min]

[0095] Laser power LP1 5 [kW]

[0096] Time tHP 400 [msec]

[0097] The focal position FP1 is located 10 mm above the upper surface of workpiece W1.

[0098] Operating mode OM1 pulse oscillation mode

[0099] The results of this experiment determined that the covering parts 102 and 112 were discharged from a rectangular region with a length x≈55[mm]×width y≈3mm that encompasses the entire overlapping surface region SE'. That is, the experimental results demonstrate that by appropriately setting the operating conditions CD, it is possible not only to discharge the covering parts 102 and 112 from the overlapping surface region SE', but also from the region surrounding the overlapping surface region SE'.

[0100] The time t, which is set as the operating condition CD, has elapsed since the moment when the oscillation of the irradiation point P1 begins in step S2. HP At this time, the processor 50 sends a command to the laser oscillator 12 to stop the emission of laser LB1, thus ending the heating process HP in step S2. For example, the processor 50 can also stop the emission of laser LB1 by stopping the laser generation operation performed by the laser oscillator 12. Alternatively, the laser oscillator 12 can also have a shutter that opens and closes the optical path of the emitted laser LB1, and the processor 50 can stop the emission of laser LB1 by closing the shutter.

[0101] Refer again Figure 10 In step S3, the processor 50 determines whether the base material 100 and base material 110 have been cooled to a temperature below a predetermined threshold T3. This threshold T3 may be set, for example, to the melting point of the covering 102 and the covering 112, or it may be set to the ambient temperature.

[0102] As an example, the processor 50 may time the elapsed time t1 from the point in time of the heating process HP ending in step S2, and the processor 50 may time the predetermined time t1 is reached at that elapsed time t1. th When the temperature is below the threshold T3, it is determined that the base material 100 and base material 110 have been cooled (i.e., "yes").

[0103] The time t th Let t be the time sufficient for the base materials 100 and 110 heated in step S2 to cool to a temperature below the threshold T3. th Determined in advance by the operator (e.g., t) th= 20 [msec]) and is stored in the memory 52. When the processor 50 determines "yes", it proceeds to step S4. On the other hand, when it determines "no", it loops step S3.

[0104] In step S4, the processor 50 executes the formal welding process WP. Specifically, the processor 50 first switches the operation mode OM of the laser oscillator 12 to the second operation mode OM2 and sends an instruction to the laser oscillator 12 to generate the second type of laser LB2 having the laser power LP2.

[0105] According to this instruction, the laser oscillator 12 generates the laser LB2 with the laser power LP2 by continuous oscillation and emits the laser LB2 to the laser irradiation device 16 via the light guide member 14. In the present embodiment, the laser power LP2 is set to a value smaller than the laser power LP1 in step S2 (LP2 < LP1).

[0106] At the same time, the processor 50 operates the lens drive device 30 of the laser irradiation device 16 to adjust the position of the optical lens 28, thereby controlling the focus of the laser LB2 emitted from the laser irradiation device 16 at the focus position FP2. In the present embodiment, this focus position FP2 is set at a position closer to the upper surface of the workpiece W1 (that is, the upper surface of the first layer 102a of the covering member 102) than the above-mentioned focus position FP1 (for example, the position of the upper surface of the first layer 102a).

[0107] In this way, the laser LB2 with the laser power LP2 is irradiated onto the workpiece W1. The irradiation point P2 of the laser LB2 at this time has an area E2 (< E1) corresponding to the focus position FP2. In addition, at this time point, the irradiation point P2 may also be arranged at the teaching point TP1 of the welding part WL.

[0108] Next, the processor 50 operates the irradiation point moving mechanism 20 to move the irradiation point P2 of the laser LB2 irradiated onto the welding part WL. Specifically, the processor 50 changes the orientations of the reflecting mirror 34 and the reflecting mirror 36 by operating the reflecting mirror drive device 38 and the reflecting mirror drive device 40, thereby moving the irradiation point P2 from the teaching point TP1 to the teaching point TP2 along the welding line LN to the right at a speed V2. This speed V2 can be set to, for example, 3 [m / min] (that is, V2 << V1).

[0109] Furthermore, in step S4, the processor 50 can also cause the irradiation point P2 to swing and move to the right along the welding line LN. Specifically, the processor 50 causes the irradiation point P2 to swing in the y-axis direction of coordinate system C1 and move to the right by changing the orientation of the reflectors 34 and 36. According to this structure, sputtering can be suppressed when the base material 100 and base material 110 are melted using the laser LB2.

[0110] When the irradiation point P2 reaches the teaching point TP2, the processor 50 sends a command to the laser oscillator 12 to stop the emission of laser LB2, thus ending the formal welding process WP in step S4. Through the formal welding process WP in step S4, the base material 100 and base material 110 are melted along the welding line LN by laser LB2, thereby welding the base material 100 and base material 110 together at the welding position WL.

[0111] In step S5, the processor 50 determines whether welding for all welded parts WL is complete. For example, the processor 50 can determine whether welding for all welded parts WL is complete by analyzing the welding program PG. If the determination is "yes", the processor 50 terminates the process. Figure 10 The process is shown. On the other hand, if the processor 50 determines "no", it returns to step S1 and performs steps S1 to S5 for the next welding part WL.

[0112] As described above, in this embodiment, in step S2, the processor 50 heats the overlapping surface region SE' to a temperature T that is above the boiling point T1 of the covering 102 and the covering 112 and lower than the melting point T2 of the base material 100 and the base material 110 by oscillating the irradiation point P1 of the laser LB1 within the heating region HA. The covering 102 and the covering 112 are then discharged to the outside of the overlapping surface region SE' via the gap G formed between the workpiece W1 and the workpiece W2.

[0113] Then, in step S4, the processor 50 irradiates the welding area WL with laser LB2 to melt the base material 100 and base material 110 at the welding area WL, thereby welding the base material 100 and base material 110 together. According to this embodiment, the second layer 102b of the covering 102 and the first layer 112a of the covering 112 can be removed from the area where the base material 100 and base material 110 were melted in step S4 by step S2. Therefore, it is possible to prevent bubbles generated by the vapor of the covering 102 and the covering 112 from being mixed into the interior of the base material 100 and base material 110 when the base material 100 and base material 110 are melted at the welding area WL in step S4.

[0114] Furthermore, in this embodiment, a gap G is formed in the overlapping area SE' due to the vaporization of the covering elements 102 and 112. The vapor from the covering elements 102 and 112 is discharged to the outside of the overlapping area SE' through this gap G. Therefore, it is not necessary to form through holes in the base material 100 or 110 to release the vapor from the second layer 102b and the first layer 112a generated in step S4, as is done conventionally. This simplifies the welding process.

[0115] Furthermore, in this embodiment, the irradiation point P1 is made to oscillate within the heating region HA by changing the orientation of reflectors 34 and 36. With this structure, the irradiation point P1 can oscillate relative to the workpiece W1 at a high speed (velocity V1) (that is, the velocity V1 can be set to a large value). With this structure, the entire overlapping surface region SE' can be heated more uniformly in step S2.

[0116] Furthermore, in this embodiment, the speed V2 of the working condition CD in step S4 is set to be much lower than the speed V1 of the working condition CD in step S2 (V2 << V1). According to this structure, the entire area of ​​the overlapping surface region SE' can be heated more uniformly in step S2, and on the other hand, the base material 100 and the base material 110 can be reliably melted in step S4.

[0117] Furthermore, in this embodiment, the area E1 of the irradiation point P1 in step S2 is greater than the area E2 of the irradiation point P2 in step S4 (E1>E2). According to this structure, since the heating area of ​​the laser LB1 in step S2 is increased, the expansion pressure of the covering parts 102 and 112 generated in the overlapping surface region SE' can be increased, thereby improving the effect of discharging the covering parts 102 and 112. On the other hand, the laser power per unit area of ​​the irradiation point P2 can be increased in step S4, thus enabling reliable melting of the base material 100 and base material 110.

[0118] Furthermore, in this embodiment, the laser power LP1 of the working condition CD in step S2 is greater than the laser power LP2 of the working condition CD in step S4 (LP1>LP2). According to this structure, the overlapping surface region SE' can be rapidly heated to a temperature T in step S2 that is above the boiling point T1 of the covering 102 and the covering 112 and lower than the melting point T2 of the base material 100 and the base material 110.

[0119] Furthermore, in this embodiment, in step S2, a first type of laser LB1 (pulsed oscillating laser) is irradiated onto the heating area HA, while in step S4, a second type of laser LB2 (continuous oscillating laser) is irradiated onto the welding area WL. According to this structure, excessive temperature rise of the upper surface of the workpiece W1 can be prevented in step S2, and the overlapping surface area SE' can be heated efficiently, and the base material 100 and base material 110 can be efficiently melted in step S4.

[0120] Furthermore, in this embodiment, in step S2, the irradiation point P1 is oscillated within the heating region HA such that the temperature T' at the center of the heating region HA is highest. By creating a temperature gradient in the temperature distribution of the heating region HA in this way, a temperature gradient can also be formed in the temperature distribution of the overlapping surface region SE'. Figure 12 The temperature gradient shown enhances the effect of blowing the vapors of the covering 102 and the covering 112 radially outwards towards the outer side of the overlapping surface region SE' in step S2.

[0121] In addition, in order to form Figure 12 The temperature gradient shown could also be achieved by the processor 50 controlling the laser power LP1 to a specific value during step S2, while the irradiation point P1 moves through the path between the teaching point TP13 and the teaching point T14 in the irradiation point movement path MP. _1 On the other hand, during the period when passing through other paths, the laser power LP1 is controlled to be the laser power LP1. _2 ( <LP1 _1 By increasing the laser power LP1 during the path between teaching point TP13 and teaching point T14 while irradiation point P1 is passing through, a temperature gradient can be effectively formed in which the temperature of the central part of the heating region HA (i.e., the overlapping surface region SE') increases.

[0122] In this embodiment, after step S2, when the base material 100 of workpiece W1 is cooled to a temperature below the threshold T3 (i.e., determined to be "yes" in step S3), step S4 is executed. By cooling the base material 100 and base material 110 after heating them in this way, the material structure of the base material 100 and base material 110 can be refined, thereby improving the strength of the base material 100 and base material 110. However, the processor 50 may also omit step S3 and execute step S4 immediately after step S2.

[0123] Furthermore, in the above embodiments, the memory 52 may also pre-store parameters such as the material MT (or thermal conductivity) of workpieces W1 and W2, the thickness f of workpieces W1 and W2, and the working conditions CD (welding area WL, heating zone HA, speed V1 and speed V2, laser power LP1 and laser power LP2, time t). HP The data table DT1 is linked and stored with the focus position FP and the operating mode OM.

[0124] As an example, data sheet DT1 can also be made to display the material MT of base material 100 and base material 110. A (or thermal conductivity), the material MT of the covering 102 and the covering 112 B (or thermal conductivity) and the thickness f of workpieces W1 and W2 (or the thickness of the base material and the thickness of the cladding) and the parameters of the operating conditions CD used in step S2 (heating process HP) (e.g., the length of the welding line LN, the length x1 and width y1 of the heating zone HA, the speed V1, the laser power LP1, the time t) HP The focus position FP1 and the operating mode OM1 are associated and stored together.

[0125] Furthermore, the processor 50 can also display the data table DT1 on the display device 60. In this case, the operator can refer to the data table DT1 and select materials MT from the data table DT1 based on the base material 100 of the workpiece W1 and the base material 110 of the workpiece W2. A The material MT of the covering 102 and the covering 112 B And the thickness f of workpieces W1 and W2, retrieve the optimal operating conditions CD to be used in step S2.

[0126] Alternatively, processor 50 can also generate input material MT. A Material MT B The input screen for thickness f is displayed on the display device 60. The operator can then visually confirm the input screen displayed on the display device 60 while operating the input device 58 to input the material MT. A Material MT B And information about the thickness f.

[0127] Then, the processor 50 can also retrieve the material MT input from the data table DT1. A and MT B The operating condition CD corresponding to the thickness f is automatically set to the operating condition CD used in step S2. Based on this structure, the setting of the operating condition CD can be automated, thus simplifying the preparation of the PP process.

[0128] In addition, data sheet DT1 can also be made to store material MT. A and material MT B The thickness f is linked to the parameters of the operating conditions CD used in step S4 (formal welding process WP) (e.g., the length of the weld line LN, the length x1 and width y1 of the heated zone HA, the speed V2, the laser power LP2, the focal position FP2, and the operating mode OM2). Data sheet DT1 can be created by collecting data using experimental methods or simulations.

[0129] Next, refer to Figure 14 and Figure 15 To illustrate another embodiment of the laser welding system 70, we will now describe the laser welding system 70. The laser welding system 70 differs from the laser welding system 10 described above in that it also includes a temperature sensor 72. The temperature sensor 72 may be, for example, a thermocouple, a platinum resistance thermometer, or an infrared detection type temperature measuring device (thermal imaging camera, etc.). This temperature sensor 72 measures the temperature T' of the heated area HA on the workpiece W1 in a contact or non-contact manner.

[0130] Next, refer to Figure 16 This describes the welding process of the laser processing system 70. The welding process in this embodiment is similar to... Figure 10 The difference in the process shown lies in step S2' (heating process HP). See below for reference. Figure 17 Let's explain step S2'.

[0131] After step S2 begins, in step S11, processor 50 begins generating laser LB1. Specifically, similar to step S2 above, processor 50 switches the operating mode OM of laser oscillator 12 to the first operating mode OM1, so that laser oscillator 12 generates a first type of laser LB1 (pulsed oscillating laser) with laser power LP1. At the same time, processor 50 actuates lens drive device 30 to adjust the position of optical lens 28, so as to control the focus of laser LB1 at focal position FP1.

[0132] In step S12, the processor 50 initiates the action of oscillating the irradiation point P1 of the laser LB1 within the heating region HA. Specifically, similar to step S2 above, the processor 50 initiates the action of activating the irradiation point moving mechanism 20 to oscillate the irradiation point P1 of the laser LB1 along the irradiation point moving path MP within the heating region HA at a speed V1.

[0133] In step S13, the processor 50 estimates the temperature T of the overlapping surface area SE'. Specifically, the processor 50 obtains the temperature T' of the heating area HA measured by the temperature sensor 72 at this time point, and estimates the temperature T of the overlapping surface area SE' based on this temperature T'. As an example, the memory 52 pre-stores a data table DT2 that stores the temperature T' of the heating area HA and the temperature T of the overlapping surface area SE' in an associated manner.

[0134] This data table DT2 can be created by experimental methods or thermodynamic simulations, etc. The processor 50 retrieves the temperature T corresponding to the obtained temperature T' from the data table DT2. In this way, the processor 50 can estimate the temperature T of the overlapping surface area SE' at this time based on the temperature T' of the heating area HA measured by the temperature sensor 72. As another example, the temperature T of the overlapping surface area SE' can also be estimated by applying the temperature T' of the heating area HA measured by the temperature sensor 72 to a known thermodynamic equation.

[0135] In addition, the temperature sensor 72 can also be configured to measure the temperature T' of the central part of the heating area HA. In this case, the temperature sensor 72 measures the highest temperature T' of the heating area HA, and the processor 50 estimates the temperature T (highest temperature) of the central part of the overlapping surface area SE' based on this highest temperature T' in this step S13. As an alternative, the temperature sensor 72 can also be configured to measure the temperature T' at any position within the heating area HA (for example, any position among the teaching points TP11 to TP16).

[0136] In step S14, the processor 50 determines whether the temperature T estimated in the most recent step S13 is lower than a predetermined threshold T th1 (T < T th1 ). This threshold T th1 is predetermined by the operator and stored in the memory 52. For example, the threshold T th1 can be set to the boiling point T1 of the cladding 102 and the cladding 112 (or a temperature below this boiling point T1), or can also be set to a temperature higher than the boiling point T1 and lower than the melting point T2 of the base materials 100 and 110 (T1 < T th1 < T2). The processor 50 determines "yes" when T < T th1 and proceeds to step S17. On the other hand, when T ≥ T th1 , it determines "no" and proceeds to step S15.

[0137] In step S15, the processor 50 determines whether the temperature T estimated in the most recent step S13 is higher than a predetermined threshold T th2 (T > T th2 ). This threshold Tth2 Set to a value higher than the above-mentioned threshold T th1 The threshold T th2 Is pre-determined by the operator and stored in the memory 52.

[0138] For example, the threshold T th2 Can be set to the melting point T2 of the base materials 100 and 110 (or a temperature above the melting point T2), or can be set to a temperature higher than the boiling point T1 of the cladding parts 102 and 112 and lower than the melting point T2 (for example, T1 < T th1 < T th2 < T2). The processor 50 determines "yes" when T > T th2 And enters step S17. On the other hand, when T ≤ T th2 It determines "no" and enters step S16.

[0139] In step S16, the processor 50 determines whether the time t determined by the processing condition CD has elapsed since the start time point of step S12 HP . Specifically, the processor 50 measures the elapsed time t2 since the start time point of step S12 and determines whether the elapsed time t2 reaches the time t HP . The processor 50 determines "yes" when the elapsed time t2 reaches the time t HP And ends step S2' and enters the step S3 in Figure 16 . On the other hand, when the elapsed time t2 does not reach the time t HP It determines "no" and returns to step S13.

[0140] On the other hand, when it is determined "yes" in step S14 or step S15, in step S17, the processor 50 changes the operation condition CD. Specifically, in step S17 after it is determined "yes" in step S14, the processor 50 changes the operation condition CD, for example, by reducing the speed V1, increasing the laser power LP1, increasing the time t HP Or making the focal position FP1 approach the upper surface of the workpiece W1.

[0141] Here, the reduction of the speed V1, the increase of the laser power LP1, the increase of the time t HP And the approach of the focal position FP1 to the upper surface of the workpiece W1 are all related to increasing the temperature of the heating area HA (that is, the overlapping surface area SE'). Therefore, by changing the operation condition CD in this way, the temperature T of the overlapping surface area SE' can be increased to be above the threshold T th1 In the above way.

[0142] On the other hand, in step S17 after determining "yes" in step S15, the processor 50, for example, increases the speed V1, decreases the laser power LP1, and decreases the time t. HP Alternatively, the operating conditions CD can be changed by moving the focus position FP1 away from the upper surface of the workpiece W1.

[0143] Here, the increase in velocity V1, the decrease in laser power LP1, and the time t HP The reduction in temperature and the fact that the focal point FP1 is farther away from the upper surface of the workpiece W1 both contribute to the decrease in temperature of the heated region HA (i.e., the overlapping region SE'). Therefore, by changing the operating conditions CD in this way, the temperature T of the overlapping region SE' can be made to reach the threshold T. th2 The process proceeds as follows. After executing step S17, the processor 50 continues step S2' according to the modified job conditions CD and proceeds to step S16.

[0144] As described above, in this embodiment, the processor 50 estimates the temperature T of the overlapping surface region SE' based on the temperature T' of the heating region HA measured by the temperature sensor 72, and changes the operating conditions CD according to this temperature T. According to this structure, the temperature T of the overlapping surface region SE' can be finely controlled during the execution of step S2', thus improving the effect of expelling the covering 102 and covering 112 present in the overlapping surface region SE' to the outside. Furthermore, the operating conditions CD (e.g., the time t for executing the heating process HP) can be adjusted. HP Optimization.

[0145] Furthermore, the laser irradiation device 16 and the irradiation point moving mechanism 20 are not limited to... Figure 3 As shown. For example, it can also be from... Figure 3 The irradiation point moving mechanism 20 shown omits one of the reflectors 34 and 36. In this case, the irradiation point moving mechanism 20 can also be configured to cause the irradiation point P on the workpiece W1 to reciprocate relative to the workpiece W along the x-axis of coordinate system C1 within a length x1 by means of the other of the reflectors 34 and 36.

[0146] On the other hand, the irradiation point moving mechanism 20 may also have a worktable for fixing workpieces W1 and W2; and a table drive device (e.g., piezoelectric element, ultrasonic transducer or ultrasonic motor) that causes the worktable to reciprocate within a width y1 along the y-axis of coordinate system C1 (none are shown).

[0147] In this configuration, the irradiation point moving mechanism 20 causes workpieces W1 and W2 to swing along the y-axis of coordinate system C1 via a stage drive, and causes the irradiation point P to swing relative to workpiece W1 along the x-axis of coordinate system C1 via the other of reflectors 34 and 36, thereby heating the entire heating area HA. ​​The heating area HA is approximately rectangular in length x1 × width y1, defined by the relative movement path of the irradiation point P relative to workpiece W1.

[0148] In addition, the laser irradiation device 16 is not limited to Figure 3 The laser scanner shown could also be, for example, a laser processing head having a reflector that reflects the received laser light and an optical lens that converges the laser light reflected by the reflector. In this case, the irradiation point moving mechanism 20 could also have a rotating lens that is rotatably disposed inside the laser processing head.

[0149] The rotating lens is supported in a manner that allows it to rotate about an axis parallel to the optical path of the laser reflected by the mirror of the laser processing head. The rotating lens has a laser incident surface that is inclined relative to the optical path. The irradiation point moving mechanism 20 can shift the irradiation point P on the workpiece W1 by rotating the rotating lens.

[0150] Furthermore, in the above-described embodiment, it is described that in the preparation process PP, after the operator sets the heating zone HA for the workpiece W1, the teaching points TP11 to TP16 and the irradiation point movement path MP are set. Figures 5-9 However, it is possible to omit the setting of the heating zone HA from the preparation process PP.

[0151] For example, after the operator sets the welding area WL for workpiece W1, they can set teaching points TP11 to TP16 to surround the welding area WL. Next, the irradiation point movement path MP can be set based on the teaching points TP11 to TP16. In this case, for example... Figure 9 As shown, the heating area HA is uniquely determined by the set teaching points TP11~TP16 and the irradiation point movement path MP.

[0152] Alternatively, in the preparation process PP, after the operator sets the welding position WL, the processor 50 automatically sets the heating zone HA based on the position data of the welding position WL, in a manner that includes the welding position WL. In this case, the operator can also pre-input the data via the input device 58. Figure 5 The processor 50 automatically sets the heating zone HA based on the input data from the operator, which includes information such as length x1, width y1, distance x2, and distance x3.

[0153] also, Figure 5 At least one of the distances x2 and x3 shown can be zero. In this case, the teaching point TP1 is positioned on the left side SD1 of the heating region HA, or the teaching point TP2 is positioned on the right side SD2 of the heating region HA. Alternatively, the teaching point TP1 can also be positioned to the left of the left side SD1 of the heating region HA.

[0154] Alternatively, the teaching point TP2 can be positioned to the right of the left side SD2 of the heating region HA. In this case, most of the weld portion WL is included within the heating region HA, while both ends of the weld portion WL are located outside the heating region HA. Here, as described above, the inventors' experiments have yielded the following insights: through the heating process HP, not only can the covering part 102 and the covering part 112 be discharged from the overlapping surface region SE', but also from the region surrounding the overlapping surface region SE'. Therefore, even if a portion of the weld portion WL is located outside the heating region HA, the covering part 102 and the covering part 112 can be discharged from the region where the weld portion WL is located.

[0155] also, Figure 9 The illustrated irradiation point movement path MP is one example; various other irradiation point movement paths are considered. Figure 18 Another example of the irradiation point movement path MP is shown. Figure 18 In the example shown, four teaching points TP11, TP12, TP15, and TP16 are set at each vertex of the heating region HA. The irradiation point movement path MP is set, for example, as the path TP11→TP12→TP15→TP16→TP11. Alternatively, the irradiation point movement path MP can also be set to a path that causes the temperature T of the overlapping surface region SE' to rise uniformly, without forming a temperature difference during the execution of the heating process HP. Figure 12 The temperature gradient shown is as shown.

[0156] exist Figure 19 This shows another example of the movement path MP of the irradiation point. Figure 19 In the example shown, two teaching points TP21 and TP22 are set in the heating area HA, and the irradiation point movement path MP is set as a reciprocating path between teaching points TP21 and TP22. Teaching points TP21 and TP22, like teaching points TP1 and TP2, can be set at positions along the y-axis of coordinate system C1. Even within this irradiation point movement path MP, the entire area of ​​the heating area HA and the overlapping surface area SE' can be heated by appropriately setting the operating conditions CD.

[0157] Furthermore, in step S2 above, it is also possible that, as the irradiation point P1 moves along the irradiation point movement path MP from a teaching point TP... α Move to the teaching point TP α The next teaching point TP γ This causes the laser power LP1 to change along with the velocity V1. See below for reference. Figure 20 To illustrate this kind of control.

[0158] exist Figure 20 In the middle, the horizontal axis shows two consecutive teaching points TP in the path MP of the illumination point movement. α and teaching point TP γ and the teaching point TP α With teaching point TP γ The point between (e.g., the midpoint) TP β The vertical axis shows the velocity V1 and laser power LP1. Additionally, Figure 20 In the graph, the solid line represents the laser power LP1, while the dashed line represents the velocity V1.

[0159] exist Figure 20 In the example shown, in step S2, the illumination point P1 is moved from the teaching point TP. α Move to teaching point TP γ At that time, the illumination point P1 is moved from the teaching point TP. α TP at the appointed time β Gradually accelerate, thus increasing the speed V1; on the other hand, make the irradiation point P1 pass through the point TP. β Then arrived at teaching point TP γ The speed gradually decreases until the velocity V1 decreases.

[0160] When configured such that the illumination point P1 is from the teaching point TP α Move to teaching point TP γ When the laser power LP1 is kept constant while the velocity V1 varies during the heating region HA, the teaching point TP has a low velocity V1. α and teaching point TP γ Temperatures in the vicinity of point TP may be excessively higher than point TP. β The temperature in the vicinity of the heating zone. In this case, the temperature T at the edge of the heating zone HA (e.g., edge SD1 and edge SD2) may be excessively higher than that in the center.

[0161] Therefore, as Figure 20 As shown, in step S2, as the irradiation point P1 moves from the teaching point TP... α To point TP β As the processor 50 moves, it increases the laser power LP1 along with the velocity V1. On the other hand, as the irradiation point P1 moves from point TP... β To the teaching point TPγ The processor 50 moves and reduces the laser power LP1 along with the speed V1. By changing the laser power LP1 and the speed V1 together, the entire area of ​​the heating region HA (i.e., the overlapping surface region SE) can be heated more uniformly.

[0162] In addition, Figure 9 In the manner shown, Figure 20 The teaching point TP is shown. α To the teaching point TP γ The path MP for the irradiation point movement up to this point can be, for example, the path from TP11 to TP12, the path from TP13 to TP14, or the path from TP15 to TP16. In this case, the processor 50 can also control the value (maximum, minimum, or average) of the laser power LP1 in the path from TP13 to TP14 to LP1. _1 On the other hand, during the period when the laser power LP1 is traversed through paths other than its own, the value of LP1 is controlled to LP1. _2 ( <LP1 _1 ).

[0163] On the other hand, the processor 50 can also control the laser power LP1 to be fixed during the path TP12→TP13, TP14→TP15, TP16→TP13, and TP14→TP11 when the irradiation point P1 is traversed. That is, in this case, at the two teaching points TP α With teaching point TP γ When the path MP between illumination points is relatively long, the processor 50 changes the laser power LP1. On the other hand, at the teaching point TP... α With teaching point TP γ When the path MP between the irradiation points is relatively short, the processor 50 controls the laser power LP1 to be fixed.

[0164] In addition, Figure 18 In the manner shown, Figure 20 The teaching point TP is shown. α To the teaching point TP γ The path MP for the irradiation point movement up to this point can be a path from TP11 to TP12, a path from TP12 to TP15, a path from TP15 to TP16, or a path from TP16 to TP11. Additionally, in Figure 19 In the manner shown, Figure 20 The teaching point TP is shown. α To the teaching point TP γ The path MP for the irradiation point can be either TP11→TP12 or TP12→TP11.

[0165] Furthermore, in the aforementioned operating conditions CD, the focusing density ρ1 of the laser LB1 irradiating the heated area HA in step S2 can be determined instead of the laser power LP1 and the focal position FP1 (or the focusing density ρ1 can be determined in addition to the laser power LP1 and the focal position FP1). The focusing density ρ1 can be defined, for example, as the laser power LP1 per unit area of ​​the irradiation point P1 on the workpiece W1 (i.e., ρ1 = LP1 / E1).

[0166] Furthermore, in the aforementioned operating conditions CD, the focusing density ρ2 of the laser LB2 irradiating the welding area WL in step S4 can be determined instead of the laser power LP2 and the focal position FP2 (or the focusing density ρ2 can be determined in addition to the laser power LP2 and the focal position FP2). The focusing density ρ2 can be defined, for example, as the laser power LP2 per unit area of ​​the irradiation point P2 on the workpiece W1 (i.e., ρ2 = LP2 / E2). Here, as described above, the area E of the irradiation point P on the workpiece W1 depends on the focal position FP of the laser LB. Therefore, the focusing density ρ can be controlled by appropriately selecting the laser power LP of the laser LB and the focal position FP of the laser LB.

[0167] Here, in the operating conditions CD, the focusing density ρ1 of laser LB1 in step S2 can also be set to a value smaller than the focusing density ρ2 of laser LB2 in step S4 (ρ1 < ρ2). For example, in step S2, the processor 50 controls the laser power LP1 to 5 [kW] and the focal position FP1 to be 10 [mm] above the upper surface of the workpiece W1. In this case, the diameter of the irradiation point P1 is approximately 0.9 [mm], and the area E1 is approximately 0.64 [mm²]. 2 Therefore, in this case, the concentration density ρ1 can be controlled to ρ1≈8 [kW / mm]. 2 ].

[0168] On the other hand, in step S4, the processor 50 controls the laser power LP2 to 2 [kW] and the focal position FP2 to the position of the upper surface of the workpiece W1. In this case, the diameter of the irradiation point P2 is approximately 0.4 [mm], therefore, the area E2 is approximately 0.13 [mm²]. 2 Therefore, in this case, the concentration density ρ2 can be controlled to ρ2≈15.4 [kW / mm]. 2 ]>ρ1.

[0169] Furthermore, the memory 52 may also pre-store a data table DT3 that associates the focused light density ρ with the laser power LP and the focal position FP. Then, when executing step S2 or S4, the processor 50 may retrieve the laser power LP and focal position FP corresponding to the focused light density ρ set in the working conditions CD from the data table DT3, and irradiate the workpiece W1 with the laser LB based on the retrieved laser power LP and focal position FP, thereby controlling the focused light density ρ.

[0170] Furthermore, in the aforementioned operating conditions CD, the time t required for the irradiation point P1 to complete one reciprocating motion along the irradiation point movement path MP when the irradiation point moving mechanism 20 swings the irradiation point P1 in the heating process HP can also be determined. MP To replace velocity V1 (or, in addition to velocity V1, to determine the time t) MP Alternatively, the same operating mode OM (OM1 or OM2) can be used in both the heating process HP (step S2 or S2') and the formal welding process WP (S4). In this case, the same type of laser LB (LB1 or LB2) is used to irradiate the workpiece W1 in both the heating process HP and the formal welding process WP.

[0171] Furthermore, the focal point FP can be the same in both the heating process HP and the formal welding process WP. In this case, the area E1 of the irradiation point P1 in the heating process HP is approximately the same as the area E2 of the irradiation point P2 in the formal welding process WP. Additionally, the laser power LP can also be the same in both the heating process HP and the formal welding process WP (LP1 = LP2).

[0172] In addition, the laser welding system 10 may also have multiple control devices 22, which independently control the laser oscillator 12, the laser irradiation device 16, the irradiation device moving mechanism 18, and the irradiation point moving mechanism 20. Furthermore, the heating zone HA (teaching point TPn, irradiation point moving path MP) is not limited to the first layer 102a of the covering 102, but can also be set for the base material 100.

[0173] Alternatively, the heating zone HA can be set on workpiece W1 (the first layer 102a of the covering 102), while the welding area WL can be set on workpiece W2 (the second layer 112b of the covering 112). In this case, the processor 50 can also irradiate workpiece W1 from above with laser LB1 during the heating process HP, and irradiate workpiece W2 from below with laser LB2 during the formal welding process WP.

[0174] In this case, the laser welding systems 10 and 70 may also include a second laser irradiation device 18B capable of irradiating the workpiece W2 from below with laser LB2, and a second irradiation point moving mechanism 20B for moving the irradiation point P2 on the workpiece W2. When the heating zone HA is set on the workpiece W1 and the welding portion WL is set on the workpiece W2, the heating zone HA and the welding portion WL are separated in the z-axis direction of coordinate system C1, but as... Figure 5 As shown when viewed from the z-axis direction, the welded part WL can be considered to be included within the heating zone HA.

[0175] Alternatively, either workpiece W1 or workpiece W2 may not have a covering member 102 or 112. For example, if workpiece W1 does not have a covering member 102, workpiece W1 is made of a base material 100, and workpiece W1 and workpiece W2 overlap in such a way that the lower surface 106 of the base material 100 is in surface contact with the upper surface of workpiece W2 (the upper surface of the first layer 112a of the covering member 112). In this case, the first layer 112a of the covering member 112 is inserted between the base material 100 and the base material 110.

[0176] Furthermore, the base material 100 and base material 110 can be made of different types of metal. Similarly, the cladding 102 and cladding 112 can also be made of different types of metal. In this case, during the heating process HP, the overlapping area SE' can be heated to a temperature above the boiling point of the cladding 102 and cladding 112 but lower than the melting point of the base material 100 (and base material 110). Additionally, the cladding 102 and cladding 112 can also be made of materials other than metals (e.g., resin).

[0177] The present disclosure has been described above through embodiments, but the above embodiments do not limit the invention covered by the claims.

[0178] Explanation of reference numerals in the attached figures

[0179] 10, 70: Laser welding system; 12: Laser oscillator; 14: Light guide component; 16: Laser irradiation device; 18: Irradiation device moving mechanism; 20: Irradiation point moving mechanism; 22: Control device; 50: Processor; 72: Temperature sensor.

Claims

1. A method for laser welding workpieces, used for laser welding a first workpiece and a second workpiece, wherein, The first workpiece and the second workpiece overlap in a manner that allows their surfaces to contact each other. The first workpiece and the second workpiece each have a base material, and at least one of the first workpiece and the second workpiece has a covering inserted between the base material of the first workpiece and the base material of the second workpiece. In the method, A laser beam is generated by a laser oscillator and then irradiated onto the first workpiece. By oscillating the laser irradiation point within a rectangular heating region, causing it to repeatedly reciprocate along forward and reverse paths determined for that heating region, the overlapping areas of the first and second workpieces corresponding to the heating region are heated to a temperature above the boiling point of the covering material and lower than the melting point of the base material of the first workpiece. The heating region is defined on the first workpiece in such a manner that it includes the welding area where the laser welding is to be performed. By heating the covering material in the overlapping area to vaporize it, a gap is formed between the first and second workpieces, through which the covering material is discharged to the outside of the overlapping area. After the covering is discharged to the outside of the overlapping area, the laser is irradiated onto the welding site to melt the base material of the first workpiece and the base material of the second workpiece at the welding site to weld the first workpiece and the second workpiece together.

2. The method according to claim 1, wherein, The laser is used to illuminate the first workpiece by reflecting the laser beam through a mirror positioned in the optical path of the laser generated by the laser oscillator. By changing the orientation of the reflector, the irradiation point can be made to oscillate within the heating area.

3. The method according to claim 2, wherein, The reflector has: A first reflecting mirror, disposed in the optical path, enables the irradiation point to be shifted along a first axis within the heating area; as well as The second reflector, which is disposed in the optical path of the laser reflected by the first reflector, enables the irradiation point to be shifted along a second axis orthogonal to the first axis within the heating region.

4. The method according to any one of claims 1 to 3, wherein, When heating the overlapping surface region, the irradiation point is made to oscillate within the heating region at a first velocity. When the base material of the first workpiece and the base material of the second workpiece are melted, the irradiation point of the laser irradiating the welding area is made to advance along the welding area at a second speed lower than the first speed.

5. The method according to any one of claims 1 to 3, wherein, The area of ​​the laser irradiation point that irradiates the heated area when heating the overlapping surface region is greater than the area of ​​the laser irradiation point that irradiates the welded area when melting the base material of the first workpiece and the base material of the second workpiece.

6. The method according to any one of claims 1 to 3, wherein, The laser power of the laser irradiating the heated area when heating the overlapping surface area is greater than the laser power of the laser irradiating the welding area when melting the base material of the first workpiece and the base material of the second workpiece.

7. The method according to any one of claims 1 to 3, wherein, The focused light density of the laser irradiating the heated area when heating the overlapping surface region is less than the focused light density of the laser irradiating the welding area when melting the base material of the first workpiece and the base material of the second workpiece.

8. The method according to any one of claims 1 to 3, wherein, When heating the overlapping surface region, the laser power of the laser irradiating the heated region is varied together with the speed at which the irradiation point oscillates within the heated region.

9. The method according to any one of claims 1 to 3, wherein, When the base material of the first workpiece and the base material of the second workpiece are melted, the irradiation point of the laser irradiating the welding area is oscillating and advancing along the welding area.

10. The method according to any one of claims 1 to 3, wherein, When heating the overlapping surface region, the first type of laser is irradiated into the heated region. When the base material of the first workpiece and the base material of the second workpiece are melted, the welding area is irradiated with a second type of laser, which is different from the first type.

11. The method according to claim 10, wherein, The first type of laser is a pulsed oscillating laser, while the second type of laser is a continuously oscillating laser.

12. The method according to any one of claims 1 to 3, wherein, When heating the overlapping area, the irradiation point is oscillated within the heating area in such a way that the temperature of the central part of the heating area is the highest.

13. The method according to any one of claims 1 to 3, wherein, After the covering is discharged to the outside of the overlapping area, while the base material of the first workpiece is cooled to a temperature below a predetermined threshold, the laser is irradiated onto the welding area to melt the base material of the first workpiece and the base material of the second workpiece.

14. The method according to claim 13, wherein, The threshold is the melting point of the coating.

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