Joining method and joining structure

Abstract

A first member 10 is made of a metal material. A second member 20 is made of a thermoplastic resin material. A weld bead 30 is formed on the first member 10. A plurality of recesses 35 are formed on the surface of the weld bead 30. The second member 20 is joined to the first member 10 in a state where a part of the melted second member 20 has penetrated the recesses 35 and the second member 20 is overlaid on the first member 10.

Description

Bonding method and bonding structure

[0001] The present invention relates to a bonding method and a bonding structure.

[0002] In Patent Document 1, there is disclosed a metal resin bonding method in which a heating region is formed in a part of a metal material using an arc heat source, a part of a resin material is heated to raise the temperature to form a bonding part, and thus the metal material and the resin material are directly bonded.

[0003] Japanese Patent No. 6589171

[0004] By the way, in the conventional invention, the resin material is melted in a state where the flat surface of the metal material and the flat surface of the resin material are in close contact with each other, so that the metal material and the resin material are bonded.

[0005] Therefore, for example, when there are variations in the surface state of the metal material such as press oil adhering to the metal material, the adhesion between the metal material and the resin material may deteriorate, and the bonding strength may decrease.

[0006] The aspect of the present disclosure has been made in view of such a point, and its purpose is to ensure the bonding strength between a first member made of a metal material and a second member made of a thermoplastic resin material.

[0007] A first aspect is a bonding method for bonding a first member made of a metal material and a second member made of a thermoplastic resin material in a state where they are overlapped with each other, including a step of welding a weldable filler material to the first member to form a weld bead having a plurality of depressions on the surface, and a step of melting a part of the second member while pressing the second member against the first member and the weld bead, so that a part of the melted second member enters the depressions.

[0008] In the first aspect, a plurality of depressions are formed on the surface of the weld bead, and a part of the melted second member enters the depressions, so that the bonding strength between the first member and the second member can be ensured by the anchor effect.

[0009] The second embodiment is the joining method of the first embodiment, wherein the step of forming the weld bead is performed while supplying shielding gas to the first member, and the flow rate [L / min] of the shielding gas is 1.0 or more and 5.0 or less.

[0010] In the second embodiment, when forming the weld bead, the flow rate of the shielding gas is adjusted to satisfy the above-described conditions, thereby causing the filler material to be in a poorly shielded state, and multiple depressions can be formed on the surface of the weld bead.

[0011] The third aspect is the joining method of the first or second aspect, wherein the length of the shortest part of the outer diameter of the recess of the weld bead is 0.1 mm or more.

[0012] In the third embodiment, by setting the outer diameter of the recess in the weld bead to satisfy the above-described conditions, a portion of the molten second member can be inserted into the recess to obtain an anchoring effect.

[0013] A fourth aspect is a joining method according to the first or second aspect, wherein the step of forming the weld bead includes the steps of: welding the filler material to the first member to form a first weld bead; and welding the filler material so as to be layered on the first weld bead to form a second weld bead.

[0014] In the fourth embodiment, the first weld bead and the second weld bead are stacked, and the overall height of the weld bead is increased, thereby increasing the surface area in close contact between the second member and the weld bead, and improving the shear tensile strength of the second member.

[0015] A fifth aspect is the joining method according to the first or second aspect, wherein the step of inserting a part of the second member into the recess is performed when the surface temperature of the weld bead is equal to or greater than the melting point of the second member.

[0016] In the fifth embodiment, a portion of the second member can be melted by using residual heat generated when the weld bead is formed, or by reheating the weld bead.

[0017] The sixth aspect is a joining method according to the first or second aspect, wherein in the step of forming the weld bead, a short-circuit welding is performed in which a forward feeding operation that feeds the filler material toward the first member and a reverse feeding operation that feeds the filler material toward the first member can be switched.

[0018] In the sixth embodiment, by performing short-circuit welding with switchable forward and reverse feed operations, welding stability can be ensured compared to when a constant feed of filler material is used. As a result, a stable weld bead can be formed even if the filler material is in a poor shielding state.

[0019] A seventh aspect is a joining structure for joining a first member made of a metal material and a second member made of a thermoplastic resin material in a state where they are overlapping each other, the joining structure comprising a filler material that can be welded to the first member, a weld bead that is welded to the first member and has a plurality of recesses on its surface, and the second member is joined to the first member in a state where a part of the molten second member enters the recesses and is overlapped with the first member.

[0020] In the seventh embodiment, multiple depressions are formed on the surface of the weld bead, and a portion of the molten second member enters these depressions, thereby ensuring the joint strength between the first member and the second member through an anchoring effect.

[0021] According to the embodiments of this disclosure, it is possible to ensure the bonding strength between a first member made of a metal material and a second member made of a thermoplastic resin material.

[0022] Figure 1 is a side cross-sectional view showing the joining structure according to this embodiment 1. Figure 2 is a schematic configuration diagram of an arc welding apparatus. Figure 3 is a side cross-sectional view showing the state in which a weld bead has been formed on the first member. Figure 4 is a plan view showing the state in which a weld bead has been formed on the first member. Figure 5 is a plan view showing an enlarged view of the shape of the recess portion of the weld bead. Figure 6 is a side cross-sectional view showing the state in which the second member is pressed against the first member and the weld bead. Figure 7 is a plan view showing the state in which a weld bead has been formed on the first member in the joining structure according to this embodiment 2. Figure 8 is a side cross-sectional view showing the joining structure according to this embodiment 3. Figure 9 is a side cross-sectional view showing the state in which a first weld bead and a second weld bead have been formed on the first member. Figure 10 is a plan view showing the state in which the first weld bead and a second weld bead have been formed on the first member. Figure 11 is a side cross-sectional view showing the state in which the second member is pressed against the first member and the weld bead.

[0023] Embodiments of the present invention will be described below with reference to the drawings. The following description of preferred embodiments is essentially illustrative and is not intended to limit the present invention, its applications, or its uses.

[0024] <Embodiment 1> Figure 1 shows a joint structure in which a first member 10 made of a metal material and a second member 20 made of a thermoplastic resin material are joined together in a superimposed state.

[0025] The first member 10 is a plate-shaped member made of a metal material. The first member 10 is, for example, mild steel, high-tensile steel plate, aluminum, etc. Mild steel and high-tensile steel plate include galvanized steel plate.

[0026] A weld bead 30 is formed on the first member 10. The weld bead 30 is made of a filler material 2 that can be welded to the first member 10 (see Figure 2). The weld bead 30 is made of the same type of metal material as the first member 10. Multiple depressions 35 are formed on the surface of the weld bead 30.

[0027] Here, "metals of the same type" refers to metals that can be welded to each other, and not only to metals of the same material, but also to metals that have good weldability, such as ferrous metals to ferrous metals, or non-ferrous metals to ferrous metals. In other words, "metals of the same type" refers to materials of the same type that have good compatibility for welding.

[0028] Specifically, the following are examples of combinations of the first member 10 and the filler material 2 during welding. For example, combinations of ferrous metal materials include mild steel and mild steel, mild steel and high-tensile steel, etc. Combinations of non-ferrous metal materials include aluminum and aluminum, aluminum and aluminum alloy, aluminum alloy and aluminum alloy, etc.

[0029] The second member 20 is a plate-shaped member made of a thermoplastic resin material. Examples of the second member 20 include polypropylene (PP), polyethylene (PE), polyurethane (PUR), acrylonitrile butadiene styrene (ABS), polyamide (PA), polybutylene terephthalate (PBT), carbon fiber reinforced thermoplastic resin (CFRTP), etc.

[0030] The second member 20 is pressed against the first member 10 and the weld bead 30. A portion of the molten second member 20 enters the recess 35. As a result, the second member 20 is joined to the first member 10 in a state where it is superimposed on the first member 10.

[0031] In this way, multiple depressions 35 are formed on the surface of the weld bead 30, and a portion of the molten second member 20 enters the depressions 35, thereby ensuring the joint strength between the first member 10 and the second member 20 through an anchoring effect.

[0032] <Arc Welding Apparatus> As shown in Figure 2, the arc welding apparatus 1 generates an arc 3 between the filler material 2, which is a welding wire and is a consumable electrode, and the first member 10 made of metal, thereby arc welding the first member 10. The filler material 2 is wound onto a wire reel 4.

[0033] The arc welding apparatus 1 comprises a welding torch 40, a welding power supply 43, a wire feeding unit 44, a robot 45, a control unit 46, and a gas supply unit 47.

[0034] The welding torch 40 holds the filler material 2, which has been fed from the wire feeding unit 44, so that it and the first member 10 face each other. The welding torch 40 supplies welding current to the filler material 2 to generate an arc 3 between it and the first member 10.

[0035] Specifically, the tip of the welding torch 40 is provided with a nozzle 41 and a tip 42. The nozzle 41 supplies shielding gas to the welding area of ​​the first member 10.

[0036] The welding power supply 43 is electrically connected to the filler material 2 via the tip 42. The welding power supply 43 is electrically connected to the first member 10. The welding power supply 43 applies a welding voltage between the filler material 2 and the first member 10, thereby causing a welding current to flow between the filler material 2 and the first member 10.

[0037] The wire feeding unit 44 feeds the filler material 2 at a predetermined wire feeding speed based on a signal from the control unit 46. The wire feeding unit 44 can switch between a forward feeding operation, which feeds the filler material 2 in the direction of the first member 10, and a reverse feeding operation, which feeds it in the opposite direction to the forward feeding operation, based on a signal from the control unit 46.

[0038] The robot 45 has multiple joints. A welding torch 40 is attached to the tip of the robot 45. The robot 45 changes the position of the welding torch 40 relative to the first member 10.

[0039] The control unit 46 controls the wire feeding speed of the filler material 2 according to the preset welding current. Here, the wire feeding speed and the welding current are correlated with each other. More specifically, the average wire welding speed as a moving average (also called the wire feeding amount) and the average welding current as a moving average (also called the set current) are correlated with each other.

[0040] The control unit 46 constitutes a robot controller that controls the operation of the robot 45. The control unit 46 moves the welding torch 40 along the welding direction of the first member 10 by giving control commands to the motors (not shown) of each axis of the robot 45.

[0041] In the present embodiment, the function of controlling the robot 45 and the function of controlling the operation of the wire feeding unit 44 are described as being performed by a single control unit 46, but the present invention is not limited to this form. For example, a robot controller having a function of controlling the operation of the robot 45 may be provided separately.

[0042] The gas supply unit 47 is connected to the welding torch 40 via a gas pipe 48. The gas supply unit 47 supplies shielding gas to the welding torch 40 via the gas pipe 48. The shielding gas supplied to the welding torch 40 is blown out from the nozzle 41.

[0043] The shielding gas is, for example, a mixed gas of argon (Ar) and carbon dioxide. The ratio of argon contained in the shielding gas is, for example, 80% or more.

[0044] <Joining method> Hereinafter, a joining method for joining the first member 10 and the second member 20 in a state where they are overlapped with each other will be described. As shown in FIGS. 3 and 4, the arc welding apparatus 1 welds the filler metal 2 that can be welded to the first member 10 to the first member 10 to form a weld bead 30.

[0045] Specifically, the arc welding apparatus 1 performs short-circuit arc welding that repeats a short-circuit state in which the filler metal 2 and the first member 10 are short-circuited and an arc state in which an arc is generated between the filler metal 2 and the first member 10.

[0046] The arc welding apparatus 1 supplies a welding current while feeding the filler metal 2 as a welding electrode to the first member 10, thereby releasing the short circuit between the filler metal 2 and the first member 10 and generating an arc 3 between the filler metal 2 and the first member 10.

[0047] In this way, droplets are generated at the tip of the filler metal 2 by the arc 3 generated in the arc state. On the other hand, in the short-circuit state, the droplets generated at the tip of the filler metal 2 are brought into contact with the first member 10 and transferred.

[0048] The weld bead 30 is formed by melting and bonding the filler metal 2 melted by arc welding to the first member 10.

[0049] In the process of forming the weld bead 30, a plurality of depressions 35 are formed on the surface of the weld bead 30. Specifically, the process of forming the weld bead 30 is carried out while supplying shielding gas to the first member 10.

[0050] Normally, to prevent the filler material 2 from becoming a shielding failure, the flow rate of the shielding gas [L / min] is set to, for example, 10.0 or more and 25.0 or less.

[0051] In contrast, in this embodiment, the operation of the gas supply unit 47 is controlled to adjust the flow rate [L / min] of the shielding gas to be between 1.0 and 5.0.

[0052] Thus, when forming the weld bead 30, if the flow rate of the shielding gas is adjusted to satisfy the above-mentioned conditions, the filler material 2 will be in a state of poor shielding. If arc welding is continued in this state of poor shielding, air around the weld bead 30 will be drawn in, and multiple depressions 35 will be formed on the surface of the weld bead 30 (see Figure 5).

[0053] Furthermore, in the process of forming the weld bead 30, it is preferable to perform short-circuit welding that can switch between a forward feeding operation, which feeds the filler material 2 toward the first member 10, and a reverse feeding operation, which feeds the filler material 2 toward the first member 10.

[0054] In this way, by performing short-circuit welding with switchable forward and reverse feed operations, welding stability can be ensured compared to when the filler material 2 is fed at a constant rate. As a result, even if the filler material 2 is in a shielding state, the weld bead 30 can be formed stably.

[0055] As shown in Figure 6, after forming the weld bead 30, the second member 20 is pressed against the first member 10 and the weld bead 30. This step is performed when the surface temperature of the weld bead 30 is above the melting point of the second member 20.

[0056] For example, the residual heat generated when forming the weld bead 30 can be used to melt a portion of the second member 20. Alternatively, even if the weld bead 30 cools down after it has been formed, the weld bead 30 can be reheated and the second member 20 can be pressed against the weld bead 30 to melt a portion of the second member 20.

[0057] Alternatively, for example, a so-called ultrasonic welder may be used, in which ultrasonic vibrations are applied to the second member 20 while pressing the second member 20 against the weld bead 30, thereby heating the interface between the second member 20 and the weld bead 30 and melting a portion of the second member 20.

[0058] Then, while pressing the second member 20 against the first member 10 and the weld bead 30, a portion of the second member 20 is melted, and the molten portion of the second member 20 is made to enter the recess 35.

[0059] In this way, by forming multiple depressions 35 on the surface of the weld bead 30 and allowing a portion of the molten second member 20 to enter the depressions 35, the joint strength between the first member 10 and the second member 20 can be ensured by the anchoring effect.

[0060] Furthermore, it is preferable that the length of the shortest part of the outer diameter of the recess 35 of the weld bead 30 be 0.1 mm or more. It is also preferable that the depth of the recess 35 of the weld bead 30 be 0.1 mm or more. This allows a portion of the molten second member 20 to enter the recess 35, thereby achieving an anchoring effect.

[0061] <Embodiment 2> Hereinafter, the same reference numerals will be used for parts that are the same as in Embodiment 1, and only the differences will be described.

[0062] As shown in Figure 7, in the process of forming the weld bead 30, by moving the welding torch 40 in a predetermined welding direction, an oval-shaped weld bead 30 extending in the welding direction can be formed. Multiple depressions 35 are formed on the surface of the weld bead 30.

[0063] This increases the surface area in close contact between the second member 20 and the weld bead 30, and also increases the number of recesses 35, thereby improving the shear tensile strength of the second member 20.

[0064] Furthermore, the shape of the weld bead 30 can be various shapes, such as an L-shape or a concave shape, in addition to an oval shape extending in the welding direction, taking into consideration the stress applied to the second member 20.

[0065] <Embodiment 3> As shown in Figure 8, a weld bead 30 is formed on the first member 10. The weld bead 30 includes a first weld bead 31 and a second weld bead 32.

[0066] The first weld bead 31 is formed on the surface of the first member 10. The second weld bead 32 is laminated on the first weld bead 31. Multiple recesses 35 are formed on the surfaces of the first weld bead 31 and the second weld bead 32.

[0067] The second member 20 is pressed against the first member 10, the first weld bead 31, and the second weld bead 32. A portion of the molten second member 20 enters the recess 35. As a result, the second member 20 is joined to the first member 10 in a state where it is superimposed on the first member 10.

[0068] As shown in Figure 9, the arc welding apparatus 1 welds a filler material 2 that can be welded to the first member 10 to form a weld bead 30.

[0069] The process of forming a weld bead 30 includes the steps of welding the filler material 2 to the first member 10 to form a first weld bead 31, and welding the filler material 2 so as to be layered on the first weld bead 31 to form a second weld bead 32.

[0070] In the process of forming the first weld bead 31, a plurality of depressions 35 are formed on the surface of the weld bead 30. Specifically, the process of forming the weld bead 30 is carried out while supplying shielding gas to the first member 10. At this time, the flow rate of the shielding gas is adjusted to cause the filler material 2 to be in a state of poor shielding, thereby forming a plurality of depressions 35 on the surface of the first weld bead 31.

[0071] In the process of forming the second weld bead 32, the filler material 2 is arc-welded onto the surface of the first weld bead 31, thereby layering the filler material 2 onto the first weld bead 31 and forming the second weld bead 32. At this time, the flow rate of the shielding gas is adjusted to cause the filler material 2 to be in a state of poor shielding, thereby forming a plurality of depressions 35 on the surface of the second weld bead 32.

[0072] As shown in Figure 11, after forming the first weld bead 31 and the second weld bead 32, the second member 20 is pressed against the first member 10, the first weld bead 31, and the second weld bead 32. This step is performed when the surface temperature of the first weld bead 31 and the second weld bead 32 is equal to or above the melting point of the second member 20.

[0073] Then, while pressing the second member 20 against the first member 10, the first weld bead 31, and the second weld bead 32, a portion of the second member 20 is melted, and the molten portion of the second member 20 is made to enter the recess 35.

[0074] In this way, by stacking the first weld bead 31 and the second weld bead 32 and increasing the overall height of the weld bead 30, the surface area in close contact between the second member 20 and the weld bead 30 can be increased, thereby improving the shear tensile strength of the second member 20.

[0075] As described above, the present invention is extremely useful and has high industrial applicability because it provides a highly practical effect of ensuring the bonding strength between a first member made of a metal material and a second member made of a thermoplastic resin material.

[0076] 1 Arc welding apparatus 2 Filler material 10 First member 20 Second member 30 Weld bead 31 First weld bead 32 Second weld bead 35 Recess

Claims

1. A joining method for joining a first member made of a metal material and a second member made of a thermoplastic resin material in an overlapping state, comprising the steps of: welding a filler material that can be welded to the first member to form a weld bead having a plurality of recesses on its surface; and pressing the second member against the first member and the weld bead, while melting a part of the second member, thereby causing the molten part of the second member to enter the recesses.

2. The joining method according to claim 1, wherein the step of forming the weld bead is performed while supplying shielding gas to the first member, and the flow rate [L / min] of the shielding gas is 1.0 or more and 5.0 or less.

3. A joining method according to claim 1 or 2, wherein the length of the shortest part of the outer diameter of the recess of the weld bead is 0.1 mm or more.

4. A joining method according to claim 1 or 2, wherein the step of forming a weld bead includes the steps of: welding the filler material to the first member to form a first weld bead; and welding the filler material so as to be laminated on the first weld bead to form a second weld bead.

5. The joining method according to claim 1 or 2, wherein the step of inserting a part of the second member into the recess is performed when the surface temperature of the weld bead is equal to or greater than the melting point of the second member.

6. A joining method according to claim 1 or 2, wherein the step of forming the weld bead involves performing a short-circuit welding in which a forward feeding operation is possible, in which the filler material is fed toward the first member, and a reverse feeding operation is possible, in which the filler material is fed toward the first member.

7. A joining structure for joining a first member made of a metal material and a second member made of a thermoplastic resin material in a state where they are overlapped, wherein the weld bead is made of a filler material that can be welded to the first member and is welded to the first member and has a plurality of recesses on its surface, and the second member is joined to the first member in a state where a part of the molten second member enters the recesses and is overlapped with the first member.

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