JP2021154574A - Joint structure and joint method of metal member and resin member - Google Patents

Abstract

To provide a joint structure of a metal member and a resin member which achieves a joint between the resin member and the metal member with a sufficient strength.SOLUTION: There is provided a joint structure of a metal member and a resin member, in which the resin member is joined to a metal member in a melting/solidification region on a surface on the metal member side, and the melting/solidification region has a degree of crystallization (maximum crystallization ratio) of 80% or less.SELECTED DRAWING: None

Description

The present invention relates to a joining structure and a joining method of a metal member and a resin member.

Conventionally, weight reduction has been required in the fields of automobiles, railroad vehicles, aircraft, and the like. For example, in the field of automobiles, thin steel sheets are being used by using high-tensile steel, aluminum alloy materials are being used as substitutes for steel materials, and resin materials are also being used. In such fields, the development of joining technology between metal members and resin members is important not only from the viewpoint of reducing the weight of the vehicle body, but also from the viewpoint of increasing the strength, rigidity, and productivity of the joining members. be. So far, a so-called friction stir welding (FSW) method has been proposed as a method for joining a metal member and a resin member. In the friction stir welding method, as shown in FIG. 10, a metal member 211 and a resin member 212 are overlapped with each other, and while rotating the rotation tool 216, the metal member 211 is pressed to generate frictional heat, and the frictional heat is generated. In this method, the resin member 212 is melted and then solidified to join the metal member 211 and the resin member 212 (for example, Patent Documents 1 to 3).

As a joining method between a metal member and a resin member, heating is performed while pressurizing, such as a friction stir welding method, a resistance heating joining method (electric heating joining method), an induction heating joining method, an ultrasonic heating joining method, etc. A thermal pressure joining method is also known.

In the thermal pressure welding method including the friction stir welding method, solidification may be performed by natural cooling from the viewpoint of manufacturing cost, or by forced cooling from the viewpoint of shortening the manufacturing process.

Japanese Unexamined Patent Publication No. 2016-68465 Japanese Unexamined Patent Publication No. 2016-68467 Japanese Unexamined Patent Publication No. 2016-68471

However, the inventors of the present invention cannot sufficiently obtain the bonding strength when the molten resin is solidified by the conventional cooling method including natural cooling by leaving it at room temperature in the conventional friction stirring bonding method. It was found that this is due to the crystallinity of the resin (the region solidified after melting due to heat input during bonding) located at the bonding interface and facing the metal member.

Even in other thermal pressure welding methods other than the friction stir welding method, sufficient bonding strength could not be obtained when the molten resin was solidified by a conventional cooling method including natural cooling by leaving at room temperature.

An object of the present invention is to provide a joining structure and joining method between a metal member and a resin member, which achieves joining of the resin member and the metal member with sufficient strength.

The present invention
It is a joint structure of a metal member and a resin member.
The resin member is joined to the metal member in the melt-solidified region on the surface on the metal member side.
The melt-solidified region relates to a bonding structure of a metal member and a resin member having a crystallinity of 80% or less (maximum crystallinity ratio).

The present invention is also based on a thermal pressure joining method in which a metal member and a resin member are superposed, heat and pressure are applied by pressing from the metal member side by the pressing member, and the resin member is softened and melted and then solidified. The present invention relates to a joint structure between the above metal member and a resin member.

The present invention further relates to the following method of joining the metal member and the resin member as a method for realizing the joining structure between the metal member and the resin member:
The metal member and the resin member are superposed on each other, heat and pressure are applied by pressing from the metal member side by the pressing member, and the resin member is softened and melted and then solidified. It is a method of joining with
A method for joining a metal member and a resin member, wherein in the solidification step, forced cooling is performed so that the melt-solidified region of the resin member has a crystallization degree (maximum crystallinity ratio) of 80% or less.

According to the joining structure and joining method of the present invention, joining of a resin member and a metal member can be achieved with sufficient strength.

It is a schematic diagram which shows an example of the joint structure of a metal member and a resin member which concerns on this invention. It is a schematic schematic diagram which shows the surface state of a resin member at the time of forcibly peeling off a metal member from an example of the joint structure of a metal member and a resin member which concerns on this invention, and observing the surface of the resin member on the metal member side. It is a schematic diagram which shows a part example of the friction stir welding apparatus suitable for the method of joining a metal member and a resin member which concerns on this invention. It is an enlarged view of the tip part of an example of the rotation tool as a pressing member used in the joining method of this invention. It is the schematic sectional drawing for demonstrating an example of the preheating process of this invention. It is schematic cross-sectional view for demonstrating an example of the indentation stirring process and the stirring maintenance process of this invention. It is the schematic sectional drawing for demonstrating an example of the solidification process of this invention. It is schematic cross-sectional view of an example of the joining structure of a metal member and a resin member joined by the method of this invention. It is the schematic for demonstrating the measuring method of the joint strength in an Example. It is a schematic diagram for demonstrating the method of joining a metal member and a resin member in the prior art.

[Joined structure]
The joining structure according to the present invention is, for example, as shown in FIG. 1, a structure 50 in which a metal member 11 and a resin member 12 are joined to each other. In FIG. 1, since the joining structure 50 is a structure obtained by a friction stir welding method, it has a pressing mark W by a pressing member, but it may not have a pressing mark W depending on the joining method. FIG. 1 is a schematic view showing an example of a joint structure of a metal member and a resin member according to the present invention.

In the joining structure 50 according to the present invention, the joining is a region where the resin member is melted and solidified at least in the region directly under the pressing member (for example, the region directly under the rotating tool) and the outer peripheral region thereof at the joining boundary surface between the metal member 11 and the resin member 12. (That is, the melt solidification region) is achieved. Specifically, when the metal member 11 is forcibly peeled from the joint structure 50, for example, the metal member side surface 120 of the resin member 12 can be observed as shown in FIG. On the metal member side surface 120 of the resin member 12, a melt-solidified region is formed in a region 60 (diagonal line region) directly under the rotary tool and an outer peripheral region 61 (lattice region) thereof, and the bonding is achieved by such a melt-solidified region. ing.

As shown in FIG. 2, the melt-solidified regions 60 (hatched regions) and 61 (lattice regions) are regions formed by melting and solidifying the resin member 12 at the time of joining, and are on the metal member side of the resin member 12. This is a region in which a visually distinguishable step (step of several microns) exists on the outer periphery of the melt-solidified region with respect to the region 122 on the surface 120 where melting has not occurred. The surface of the corresponding region of the metal member is usually transferred to the melt-solidified regions 60 and 61. Alternatively, a coagulation fracture surface is exposed due to a part of the resin material in the melt-solidified region adhering to the surface of the metal material.

The melt-solidified areas 60 and 61 can also be referred to as a "resin melt-solidified layer" because they can be visually distinguished from the original resin base material that does not melt during joining by observing the cross section of the joining member or the like. The thickness of the resin melt-solidified layer is not particularly limited, and is preferably 0.50 mm or less, more preferably 0.10 mm or less, from the viewpoint of suppressing the influence on the physical properties of the resin member main body. The lower limit of the thickness of the resin melt-solidified layer is not particularly limited, and the thickness of the resin melt-solidified layer is usually 0.01 mm or more. The thickness of the resin melt-solidified layer is a circle having a diameter of 1.5 × D1 concentric with the outer circumference of the melt-solidified region (mainly between the melt-solidified regions 60 and 61) (for example, the region directly below the pressing member 60 (diameter D1 (mm))). The average value of the measured values at any five points on the line 62 (broken line) is used.

In the present invention, the melt-solidified region has a crystallinity of 80% or less (maximum crystallinity ratio). If the crystallinity (maximum crystallinity ratio) in the melt-solidified region exceeds 80%, the bonding strength decreases. The crystallinity (maximum crystallinity ratio) is the ratio of the "actual crystallinity analyzed and calculated by DSC (differential scanning calorimetry)" to the "maximum crystallinity". Since the maximum crystallinity differs depending on the type of resin, this index is used in the present invention. Therefore, in the present invention, the melt-solidified region is characterized by having a relatively low crystallinity (maximum crystallinity ratio). By having a relatively low crystallinity (maximum crystallinity ratio) in the melt-solidification region in this way, the bonding strength is sufficiently improved. The details of such a phenomenon are not clear, but it is considered to be based on the following mechanism. For example, the physical properties of the melt-solidified resin in contact with the metal member are lowered due to having a low crystallinity (maximum crystallinity ratio), the adhesion is improved accordingly, the bonding force is improved by the anchor effect, and the residue between the bonding members is improved. Reduced stress, etc.

The crystallinity (maximum crystallinity ratio) in the melt-solidified region is usually 40% or more (particularly 40 to 80%), and is preferably 40 to 76%, more preferably 40, from the viewpoint of further improving the bonding strength. ~ 72%. The crystallinity (maximum crystallinity ratio) may be, for example, 50% or more.

As shown in FIG. 2, the crystallinity (maximum crystallinity ratio) of the melt-solidified region is a circular line 62 (broken line) having a diameter of 1.5 × D1 concentric with the region 60 (diameter D1 (mm)) directly below the pressing member. ) The average value of the values measured at any of the above 5 points is used. Specifically, a resin member of 6 g (excluding the weight of the resin base material, fibers, etc.) collected from the specified position on the resin side fracture surface is used, and analysis is performed by the following method using a DSC (differential scanning calorimetry) device. , Calculate and do.
Equipment used: DSC (Differential scanning calorimetry) Equipment temperature cycle: 23 ° C → freezing point + 70 ° C → 23 ° C
Temperature rise rate: 10 ° C / min Temperature decrease rate: 10 ° C / min
Analytical method: Investigate and calculate the endothermic peak heat and heat generation peak heat when the sample is heated. Calculation method: Calculated using the following methods and formulas based on various peak heats.
Let x be the amount of heat generated by the peak heat generated by crystal formation (at the time of temperature rise).
Let y be the amount of endothermic peak heat associated with crystal melting.
Let z be the 100% crystal melting peak calorific value (resin eigenvalue).
Example of z; PPS: 146.2J / g, PP: 209.0J / g, PA6: 229.7J / g.
In the case of a resin type in which x can be observed (for example, PPS, etc.)-"Actual crystallinity" = (y-x) / z x 100
-"Maximum crystallinity" = y / z x 100
In the case of a resin type in which x cannot be observed (for example, PP, PA, etc.)-"Actual crystallinity" = y (1st cycle) / z x 100
-"Maximum crystallinity" = y (second cycle) / z x 100
Using the "actual crystallinity" and "maximum crystallinity" calculated using the above formula, the crystallinity (maximum crystallinity ratio) used in the present invention is calculated by the following formula.
"Crystallinity (maximum crystallinity ratio)" = "actual crystallinity" / "maximum crystallinity" x 100

The dimensions (for example, diameter) R (mm) of the melt-solidified region (60,61) usually satisfy the following relationship when the dimension of the pressing member (for example, the diameter of the rotating tool) is D1 (mm):
1.2 ≤ R / D 1 ≤ 5;
Preferably 2 ≦ R / D1 ≦ 5;
More preferably, 3 ≦ R / D1 ≦ 5.
If R / D1 is too small, the bonding strength is not sufficient.

The dimension (for example, diameter) R (mm) of the melt-solidified region (60, 61) can be easily measured based on the step on the outer periphery of the melt-solidified region on the metal member side surface 120 of the resin member 12. The dimension R is the maximum dimension of the melt-solidification region (60, 61).

Although the metal member 11 has a substantially flat plate shape as an overall shape in FIG. 1 and the like, the metal member 11 is not limited to this, and only the portion to be overlapped with the resin member 12 for joining has at least a substantially flat plate shape. As long as it has, it may have any shape.

The thickness T (thickness before joining treatment; see FIG. 5) of the substantially flat plate-shaped portion of the metal member 11 to be overlapped with the resin member 12 is usually 0.5 to 4 mm, but is not limited thereto.

As the metal constituting the metal member 11, any metal having a melting point higher than the melting point of the thermoplastic polymer constituting the resin member 12 can be used. Among them, the following metals and alloys used in the field of automobiles are preferably used:
aluminum;
Aluminum alloys such as 5000 series and 6000 series;
steel;
Magnesium and its alloys;
Titanium and its alloys.

As the metal constituting the metal member 11, aluminum or an aluminum alloy is preferably used from the viewpoint of further improving the joint strength.

The resin member 12 contains a thermoplastic polymer, and may further contain reinforcing fibers.

As the thermoplastic polymer constituting the resin member 12, any polymer having thermoplasticity can be used. Of these, thermoplastic polymers used in the field of automobiles are preferably used. Specific examples of such thermoplastic polymers include the following polymers and mixtures thereof:
Polyolefin resins such as polyethylene and polypropylene (PP) and their acid-modified products;
Polyester-based resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), and polylactic acid (PLA);
Polyacrylate-based resins such as polymethyl methacrylate resin (PMMA);
Polyether-based resins such as polyetheretherketone (PEEK) and polyphenylene ether (PPE);
Polyacetal (POM);
Acrylonitrile-butadiene-styrene copolymer resin (ABS);
Polyphenylene sulfide (PPS);
Polyamide-based resins (PA) such as PA6, PA66, PA11, PA12, PA6T, PA9T, MXD6;
Polycarbonate resin (PC);
Polyurethane resin;
Fluorine-based polymer resins; and liquid crystal polymers (LCP).

As the thermoplastic polymer constituting the resin member 12, one or more kinds selected from the group consisting of polyphenylene sulfide resin, polyamide resin and polyolefin resin (particularly polypropylene) from the viewpoint of an inexpensive polymer having excellent mechanical properties. Polymers are preferably used.

In FIGS. 1 and 2, the resin member 12 has a substantially flat plate shape as an overall shape, but the resin member 12 is not limited to this, and when it is superposed on the metal member 11 for joining, the resin member 12 is made of metal. As long as the portion directly below the member 11 has a substantially flat plate shape, it may have any shape.

The thickness t (thickness before joining treatment; see FIG. 5) of the portion of the resin member 12 immediately below the metal member 11 is usually 2 to 10 mm, particularly 2 to 5 mm, but is not limited thereto.

The reinforcing fiber contained in the resin member 12 is a fiber contained in the polymer in order to improve the strength in the field of the polymer-containing composite material, and is generally roughly classified into a continuous fiber and a discontinuous fiber. , In the present invention, the reinforcing fiber may be a continuous fiber or a discontinuous fiber.

The reinforcing fibers are usually contained in the resin member in a randomly oriented form, and the average fiber length is usually 50 mm or less, particularly 0.1 to 50 mm, preferably 1 to 50 mm. The average fiber diameter of the reinforcing fibers is not particularly limited, and is, for example, 2 to 20 μm, preferably 6 to 15 μm.

The type of the reinforcing fiber is not particularly limited, and examples thereof include carbon fiber and glass fiber.

The content of the reinforcing fiber is usually 1% by weight or more, particularly 10 to 50% by weight, preferably 20 to 50% by weight, and more preferably 30 to 50% by weight with respect to the total amount of the resin member.

As the content of the reinforcing fiber, a value based on the amount of each material used at the time of manufacturing the resin member can be used, or a value measured by the following method can be used. First, the resin member is heated in an electric furnace or the like at a temperature equal to or higher than the decomposition temperature of the thermoplastic polymer and lower than the decomposition temperature of the reinforcing fibers to remove the thermoplastic polymer and take out only the reinforcing fibers. By measuring the weight before and after heating, the content of the reinforcing fibers can be calculated as a ratio to the weight before heating. Alternatively, the content can also be measured by measuring the specific gravity.

The resin member 12 may further contain additives other than reinforcing fibers, such as stabilizers, flame retardants, colorants, and foaming agents.

The resin member 12 can be produced by subjecting a mixture containing a thermoplastic polymer and optionally contained reinforcing fibers and additives to a molding method such as an injection molding method or a press molding method.

The freezing point Ts of the resin member 12 varies depending on the type of the resin member 12, and is usually 100 to 300 ° C.
As the freezing point Ts of the resin member 12, the value measured by JIS7121 is used.

[Joining method]
In the joining method of the present invention, the metal member and the resin member are superposed, and heat and pressure are applied by pressing from the metal member side or the resin member side (particularly the metal member side) by the pressing member to soften the resin member and soften the resin member. This is a thermal pressure joining method in which a metal member and a resin member are joined after being melted and then solidified. Heat and pressure are preferably applied topically. The joining method adopted in the joining method of the present invention is not particularly limited as long as it is a method of applying heat and pressure by a pressing member. A heat bonding method, a resistance heat bonding method, an induction heat bonding method, or the like may be used. A method of locally applying heat and pressure from the metal member side by a pressing member is preferable, and a friction stir welding method is more preferably adopted.

As will be described in detail later, the friction stir welding method is to superimpose a metal member and a resin member, rotate a rotating tool as a pressing member, and press the metal member to generate frictional heat, and this friction This is a method in which a resin member is softened and melted by heat and then solidified to join the metal member and the resin member.

In the ultrasonic heat bonding method, a metal member and a resin member are superposed, and while the resin member is pressed by the pressing member, the pressing member and the resin member are caused to ultrasonically vibrate, and the resin member / metal member generated by the vibration is generated. This is a method in which a resin member is softened and melted by the frictional heat of the above, and then solidified to join the metal member and the resin member.

In the laser heat bonding method, heat is generated by irradiating the metal member with a laser in a state where the metal member and the resin member are overlapped and restrained, and the resin member is softened and melted by this heat and then solidified. This is a method of joining a metal member and a resin member. As the laser, a YAG laser, a fiber laser, a semiconductor laser, or the like is used.

The resistance heat joining method is a method of joining by utilizing the heat generated by directly passing an electric current through the metal member in a state where the metal member and the resin member are superposed and restrained.

The induction heating joining method is a method in which an induced current is generated in a metal member by an electromagnetic induction action in a state where a metal member and a resin member are overlapped and restrained, and the heat generated by the current is used for joining.

Hereinafter, the joining method of the present invention adopting the friction stirring joining method will be described in detail with reference to the drawings, as long as the molten solidified resin in contact with the metal member has a specified crystallinity (maximum crystallinity ratio). It is clear that the effect of the present invention can be obtained by using the other bonding method described above. In these figures, common reference numerals shall indicate the same member, site, dimension or region.

[Joining method of metal member and resin member by friction stir welding method]
The joining method (friction stir welding method) of the present invention will be specifically described with reference to FIGS. 3 to 8.

(1) Joining device First, FIG. 3 is a diagram schematically showing a part of a friction stir welding device suitable for carrying out the joining method of the present invention. The friction stir welding device 1 shown in FIG. 3 is configured as a device for friction stir welding of a metal member 11 and a resin member 12, and includes a columnar rotary tool 16 as a pressing member.

As shown in the drawing, the rotation tool 16 is a work 10 in which the metal member 11 is on the top and the resin member 12 is on the bottom. While rotating around the central axis X (see FIG. 4), it moves downward as shown by arrow A2. At this time, the rotation tool 16 applies pressure in the pressing region P (scheduled pressing region) on the surface of the metal member 11. Friction heat is generated by the pressing of the rotating tool 16, and the frictional heat is conducted to the resin member 12 to soften and melt the resin member 12, and then the molten resin solidifies. As a result, the metal member 11 and the resin member 12 are joined.

FIG. 4 is an enlarged view of the tip end portion of the rotation tool 16. In FIG. 4, the right half shows the appearance of the rotation tool 16, and the left half shows the cross section. As shown in FIG. 4, the columnar rotary tool 16 has a pin portion 16a and a shoulder portion 16b at a tip portion (lower end portion in FIG. 4). The shoulder portion 16b is a portion of the tip of the rotation tool 16 including the circular tip surface of the rotation tool 16. The pin portion 16a is a columnar portion having a diameter smaller than that of the shoulder portion 16b, which is projected outward (downward in FIG. 4) from the circular tip surface of the rotation tool 16 on the central axis X of the rotation tool 16. be. That is, the rotation tool 16 has a shoulder portion including the circular tip surface of the rotation tool at the tip portion, and a columnar portion having a diameter smaller than that of the shoulder portion, which is projected outward from the circular tip surface of the rotation tool. It has a pin part of. The pin portion 16a is for positioning the rotating tool 16 when the rotating rotating tool 16 is first brought into contact with the work 10 and pressed.

The material of the rotation tool 16 and the dimensions of each part are mainly set according to the type of metal of the metal member 11 pressed by the rotation tool 16. For example, when the metal member 11 is made of an aluminum alloy, the rotating tool 16 is made of tool steel (for example, SKD61, etc.), the diameter D1 of the shoulder portion 16b is 10 mm, the diameter D2 of the pin portion 16a is 2 mm, and the pin portion 16a protrudes. The length h is set to 0.3 to 0.5 mm. Further, for example, when the metal member 11 is made of steel, the rotating tool 16 is made of silicon nitride, PCBN (cubic boron nitride sintered body), or the like, the diameter D1 of the shoulder portion 16b is 10 mm, and the diameter D2 of the pin portion 16a. Is set to 3 mm, and the protruding length h of the pin portion 16a is set to 0.3 to 0.5 mm. However, it goes without saying that these are merely examples and are not limited to these. For example, the diameter D1 of the shoulder portion 16b is usually 5 to 30 mm, preferably 5 to 15 mm, but is not limited thereto.

Below the rotation tool 16, a columnar receiver 17 having the same diameter as the rotation tool 16 or a larger diameter than the rotation tool 16 is arranged coaxially with the rotation tool 16. The receiver 17 is moved upward with respect to the work 10 by a drive source (not shown) as shown by an arrow A3. The upper end surface of the receiver 17 comes into contact with the lower surface of the work 10 (more specifically, the lower surface of the resin member 12) by the time the rotating tool 16 starts pressing the work 10 at the latest. Then, the receiver 17 sandwiches the work 10 with the rotating tool 16 and supports the work 10 from below against the pressing force during the pressing period by the rotating tool 16, that is, during friction stir welding. The receiver 17 does not necessarily have to be moved in the direction of arrow A3, and a method of moving the rotation tool 16 in the direction of arrow A2 after mounting the work 10 on the receiver 17 can also be adopted.

The friction stir welding device 1 is attached to a drive control device (not shown) including an articulated robot or the like. Then, the coordinate positions of the rotation tool 16 and the receiver 17, the rotation speed (rpm) of the rotation tool 16, the moving speed (mm / min), the pressing force (N), the pressurizing time (seconds), and the like are determined by the drive control device. It is controlled as appropriate. Although not shown in FIG. 3, the friction stir welding device 1 has spacers, clamps, and the like for fixing the work 10 in advance and preventing the metal member 11 from rising when the rotary tool 16 is pressed. Equipped with a jig.

(2) Joining method The joining method of the metal member and the resin member by the friction stir welding method according to the present invention is at least the following steps:
The first step of superimposing the metal member 11 and the resin member 12; and while rotating the rotating tool 16, the metal member 11 was pressed to generate frictional heat, and the frictional heat softened and melted the resin member 12. After that, the second step of solidifying and joining the metal member 11 and the resin member 12:
Is included.

First step:
In the first step, as shown in FIG. 3, the metal member 11 and the resin member 12 are superposed at a desired joining portion.

Second step:
In the present invention, in the second step, the resin member 12 is softened and melted by pressing against the surface of the metal member 11 while rotating the rotation tool 16, and then a predetermined solidification step is performed.

(Solidification process)
In the solidification step, forced cooling is performed so that the melt-solidified region of the resin member has a predetermined crystallinity (maximum crystallinity ratio). For example, in the solidification step, the rotating tool 16 is separated from the metal member 11, and the pressing region 111 of the metal member 11 pressed by the rotating tool 16 or the pressing region and its peripheral region is formed by the melt solidification region of the resin member. It is forcibly cooled so as to have a predetermined crystallinity (maximum crystallinity ratio). The forced cooling means that after the rotating tool 16 is separated from the metal member 11, at least the pressing region 111 is forcibly cooled at an extremely high cooling rate as compared with the case where the pressing region 111 is left as it is at room temperature (for example, 25 ° C.) for cooling. Means to do. In the second step, by forcibly cooling at an extremely high cooling rate, the molten resin component is rapidly cooled, and a melt-solidified region having a predetermined crystallinity (maximum crystallinity ratio) can be generated. Therefore, in the present invention, the solidification step can be referred to as a "forced cooling step" or a "crystallinity (maximum crystallinity ratio) control step".

In the forced cooling, when the freezing point of the resin member 12 is Ts (° C.), the resin temperature at the interface between the metal member 11 and the resin member 12 immediately below the pressing region (pushing surface) 111 (≈ the melting region of the resin member 12). Temperature) is performed from the time of Ts + 50 ° C. to Ts-50 ° C. This is because the crystallinity of the melt-solidified region largely depends on the cooling rate at and near the freezing point when the resin temperature drops. The higher the cooling rate at or near the freezing point when the resin temperature drops, the lower the crystallinity of the melt-solidified region. By performing intensity cooling that achieves an extremely high cooling rate within the above temperature range, a melt-solidification region having a predetermined crystallinity (maximum crystallinity ratio) can be obtained. Forced cooling may be performed at least in the above temperature range.

The cooling rate during forced cooling is usually 50 ° C./sec or more (particularly 50 to 500 ° C./sec), which is preferable from the viewpoint of further improving the bonding strength based on the reduction of crystallinity (maximum crystallinity ratio). Is 150 ° C./sec or more (particularly 150 to 500 ° C./sec), more preferably more than 300 ° C./sec (particularly more than 300 ° C./sec and 500 ° C./sec or less). The higher the cooling rate, the lower the crystallinity (maximum crystallinity ratio) in the melt-solidified region.

The method for controlling the crystallinity (maximum crystallinity ratio) of the melt-solidified region is not particularly limited as long as the cooling rate is achieved, and for example, a pressing region of a metal member or the pressing region and its peripheral region. Examples include a method of blowing a gas flow into the metal member 11 and a method of controlling the cooling rate by utilizing heat absorption by a fixing jig such as a clamp around the joint to prevent the metal member 11 from floating. From the viewpoint of more easily obtaining an extremely high cooling rate, it is more preferable to adopt a method of spraying a gas flow on the pressing region of the metal member or the pressing region and its peripheral region.

In the method of blowing the gas flow, as shown in FIG. 7, the gas flow is blown from the nozzle 115 to the pressing region or the pressing region and its peripheral region. As a result, heat dissipation from the pressing region 111 or the pressing region and its peripheral region is promoted, whereby forced cooling of the interface between the metal member 11 and the resin member 12 is achieved. The gas flow may be any type such as an air flow, a nitrogen gas flow, a carbon dioxide gas flow, and an argon gas flow, but an air flow is preferable from the viewpoint of safety and cost.

The temperature of the gas stream is not particularly limited as long as the cooling rate is achieved, and may be, for example, 0 to 60 ° C. From the viewpoint of achieving both high cooling rate and cost, the temperature of the gas flow is preferably 0 to 30 ° C, particularly preferably 10 to 20 ° C.

The flow rate of the gas flow is not particularly limited as long as the above cooling rate is achieved, and depends on the size of the cooling range in which the gas flow is blown. For example, the area of the cooling range is 100 to 2500 mm. ^{When it is 2} , it is usually 100 to 1000 L / min.

The cooling rate also depends on the inner diameter and position of the nozzle that supplies the gas flow.
For example, when the gas flow rate and temperature are the same, the smaller the nozzle inner diameter, the larger the gas flow rate blown per unit area, and the higher the cooling rate at the center of the gas flow blowing range. The inner diameter of the nozzle may be, for example, 1 to 10 mm, and is preferably 1 to 5 mm from the viewpoint of achieving the above cooling rate.
Further, for example, when the gas flow rate and temperature are the same, the closer the nozzle position is to the pressing region (particularly the center thereof) as the cooling target, the higher the cooling rate. The distance between the tip of the nozzle and the pressing region (particularly the center thereof) as a cooling target may be, for example, 0.1 to 100 mm independently of each other in both the horizontal direction and the height direction. From the viewpoint of achieving a cooling rate and facilitating nozzle setting during joining, the thickness is preferably 10 to 50 mm.

The timing of starting and ending the blowing of the gas stream is not particularly limited as long as the above-mentioned extremely high cooling rate is achieved within the above-mentioned temperature range. For example, the blowing of the gas flow may be started at the same time as the rotary tool 16 is separated from the metal member 11, or may be started some time after the separation. From the viewpoint of shortening the spraying time for performing the desired forced cooling and from the viewpoint of ease of control in the production process, the spraying of the gas flow is performed after separating the rotary tool 16 from the metal member 11 and then at the bonding interface. It is preferable to start after, for example, 1 to 5 seconds have passed until the molten resin reaches the freezing point Ts + 50 ° C.

The gas flow blowing time (control time) is the extremely high cooling rate described above within the temperature range described above, in addition to the requirements such as the gas flow temperature, gas flow rate, nozzle diameter, and nozzle position described above. As long as it is achieved, it is not particularly limited. The blowing time of the gas stream is usually 0.1 seconds or more (particularly 0.1 to 10 seconds).

After performing the solidification step, it is usually cooled to room temperature. The cooling method is not particularly limited, and examples thereof include a neglected cooling method and an air flow cooling method.

In the second step, prior to the solidification step, at least a push-in stirring step C2 in which the rotary tool 16 is pushed into the metal member 11 to a depth that does not reach the joint boundary surface 13 between the metal member 11 and the resin member 12 is performed. It is preferable to do so.

In the second step, it is preferable to perform the preheating step C1 for rotating the rotary tool 16 in a state where only the tip portion of the rotary tool 16 is in contact with the surface portion of the metal member 11 before the push-in stirring step. , You don't have to do it.
After the indentation stirring step and before the solidification step, a stirring maintenance step C3 for continuing the rotational operation of the rotary tool 16 is performed at a position where the rotary tool 16 is inserted to a depth that does not reach the joining boundary surface. However, the step does not necessarily have to be performed.

Each step in the present embodiment may be performed by a pressure control method for controlling the pressing force (pressurizing force) and pressing time of the rotating tool, or after the insertion amount of the rotating tool in the pressing direction (after contacting the metal member). It may be formed by a position control method that controls the movement time (joining time) determined by the insertion amount) and the insertion speed of the metal member, or a combination thereof.

Hereinafter, these steps will be described in detail.

(Preheating step C1)
In the preheating step C1, by bringing the rotary tool 16 and the receiver 17 close to each other, as shown in FIG. 5, only the tip portion of the rotary tool 16 is placed on the surface portion (upper surface portion in the figure) of the metal member 11. This is a step of rotating the rotation tool 16 in contact with the rotation tool 16. Specifically, the rotation tool is rotated with only the pin portion at the tip of the rotation tool or only the surface of the pin portion and the shoulder portion in contact with the surface portion of the metal member.

Specifically, in the preheating step C1, frictional heat is generated on the surface portion (upper surface portion in the figure) of the metal member 11 by pressing the rotating tool 16. The frictional heat is transmitted to the inside of the metal member 11, and the range of the pressing region 111 (pressing region by the rotating tool 16) of the metal member 11 and the region near the pressing region 111 are preheated. At the same time, the axis center of the rotation tool is positioned. This makes it easier to push the rotary tool 16 into the metal member 11 in the next pushing and stirring step C2.

When this step is performed by the position control method, the tool insertion amount and insertion speed or insertion time in the preheating step C1 are rotated with only the tip portion of the rotation tool 16 in contact with the surface portion of the metal member 11. The tool 16 is not particularly limited as long as it can be rotated.

When this step is performed by the pressure control method, the pressurization (that is, the first pressurization) and the pressurization time (that is, the first pressurization time) of the preheating step C1 are the pressing of the rotary tool 16 as described above. It is set from the viewpoint of ease and productivity, and its value changes depending on, for example, the number of rotations of the rotation tool 16, the thickness of the metal member 11, the type of material, and the like. For example, when the aluminum alloy metal member 11 having a thickness of 1 mm or more and 2 mm or less is used, the first pressing force in the preheating step C1 is preferably a value of 500 N or more and less than 1000 N. The first pressurization time is preferably a value of 0.1 seconds or more and less than 3.0 seconds. The rotation speed of the rotation tool is preferably a value of 2000 rpm or more and 4000 rpm or less.

(Pushing stirring step C2)
In the push-in stirring step C2, the rotary tool 16 and the receiver 17 are brought close to each other to push the rotary tool 16 into the metal member 11 as shown in FIG. When the pressing and stirring step C2 is performed after the preheating step C1, the rotating tool 16 and the receiver 17 are brought closer to each other to push the rotating tool 16 into the metal member 11 as shown in FIG. As a result, the rotary tool 16 is advanced to a depth that does not reach the joint boundary surface 13 between the metal member 11 and the resin member 12. At this time, it is preferable that the rotation tool direct lower portion 110 of the metal member 11 is projected and deformed toward the resin member 12 as shown in FIG. As a result, it is possible to promote the melting of the molten resin 121 on the surface of the resin member that is melted in the region directly below the rotary tool and the flow from the region directly below the molten resin 121 to the outer peripheral region (in the direction of the arrow in FIG. 6). As a result, the contact area between the molten resin and the metal member 11 is expanded, and in the obtained bonding structure, the molten solidification region (bonding region) in which the molten resin is solidified by cooling is also expanded, so that the resin member and the metal Bonding with the member can be achieved with sufficient strength.

The insertion amount of the rotation tool 16 may be in the vicinity of T when the thickness of the metal member 11 is T (mm), and is preferably T-0.5 (mm) or more from the viewpoint of further improving the joint strength. ~ T (mm) or less). In the present specification, the insertion amount of the rotation tool 16 is the insertion amount in the thickness direction from the surface of the metal member on the outer peripheral portion of the pin portion 16a of the rotation tool 16. The insertion amount of the rotation tool 16 can be controlled more precisely by using the position (insertion amount) control device of the rotation tool.

When this step is performed by the position control method, the tool insertion amount and the insertion speed, or the insertion time in the indentation stirring step C2 may be controlled so as to achieve the above insertion amount.

When this step is performed by the pressure control method, in the indentation stirring step C2, the rotation tool 16 is rotated at a predetermined rotation speed by the second pressurizing time for the second pressurizing time. The second pressing force and the second pressurizing time in the indentation stirring step C2 may be controlled so that the above-mentioned insertion amount is achieved also in this method. The second pressurizing pressure and the second pressurizing time are set, for example, from the viewpoint of allowing the rotating tool 16 to enter the interface 13 between the metal member 11 and the resin member 12, and in the indentation stirring step C2, the rotating tool 16 is set. A second pressurization (for example, 1500 N) that is larger than the first pressurization and a predetermined number of revolutions (for example, 3000 rpm) for a second pressurization time (for example, 0.25 seconds) that is shorter than the first pressurization time. ) To rotate. For example, when the aluminum alloy metal member 11 having a thickness of 1 mm or more and 2 mm or less is used, the second pressing force in the indentation stirring step C2 is preferably a value of 1200 N or more and less than 1800 N. The second pressurization time is preferably a value of 0.1 seconds or more and less than 3 seconds. The rotation speed of the rotation tool is preferably a value of 2000 rpm or more and 4000 rpm or less.

(Stirring maintenance step C3)
In the stirring maintenance step C3, by stopping the mutual proximity of the rotating tool 16 and the receiver 17, as shown in FIG. This is a step of continuing the rotation operation of the rotation tool 16 at (referred to as "position"). Further frictional heat is generated in this step, and most of the generated frictional heat is transferred to the resin member 12. Therefore, at least the molten resin 121 in the region directly under the rotary tool in the resin member 12 flows further beyond the region directly under the resin member 12 to the outer peripheral region thereof (in the direction of the arrow in FIG. 6). The molten resin spreads in a substantially circular shape centered on the region directly below the rotating tool.

When this step is performed by the position control method, the tool insertion amount, the insertion speed, or the insertion time in the stirring maintenance step C3 is not particularly limited as long as the rotation operation is continued at the above position.

When this step is performed by the pressure control method, in the stirring maintenance step C3, the rotation tool 16 is subjected to a third pressing force (for example, 500N) smaller than the first pressing force, which is longer than the first pressurizing time. It is rotated at a predetermined rotation speed (for example, 3000 rpm) for a third pressurizing time (for example, 6.75 seconds). The third pressurizing pressure and the third pressurizing time are set from the viewpoint of sufficient softening / melting and productivity in a wide range of the resin member 12, and the values thereof are, for example, the rotation speed of the rotating tool 16 and the metal member. It varies depending on the thickness of 11 and the type of material. For example, when the aluminum alloy metal member 11 having a thickness of 1 mm or more and 2 mm or less is used, the third pressing force in the stirring maintenance step C3 is preferably a value of 100 N or more and less than 700 N. The third pressurization time is preferably a value of 3.0 seconds or more and 10 seconds or less. The rotation speed of the rotation tool is preferably a value of 2000 rpm or more and 4000 rpm or less.

The case where the metal member and the resin member are joined in a dot shape (point joining) without moving the rotation tool on the contact surface of the metal member in the surface direction has been described above. Even when the metal member and the resin member are linearly bonded while being moved (linear bonding or continuous bonding), the melt-solidified resin at the bonding interface has a specified crystallinity (maximum crystallinity ratio). As long as it is clear, the effect of the present invention can be obtained.

[Example 1]
(Resin member)
A resin member 12 having a size of 100 mm in length × 30 mm in width × 3 mm in thickness was produced by an injection molding method using polyphenylene sulfide pellets (PPS-CF 40%; manufactured by Daicel Polymer Co., Ltd.) containing 40% by weight of carbon fibers. The freezing point Ts of polyphenylene sulfide in the resin member was about 250 ° C.

(Metal member)
As the metal member, a flat plate-shaped member (thickness 1.2 mm) made of a 5000 series aluminum alloy was used.
(Rotation tool)
As the rotating tool, a tool made of tool steel having dimensions of D1 = 10 mm, D2 = 2 mm, and h = 0.35 mm was used.

(Joining method)
A joint structure of the metal member 11 and the resin member 12 was manufactured by the following method using the position control method.
First step:
The end portion of the metal member 11 and the end portion of the resin member 12 were overlapped as shown in FIG.

Second step:
As shown in FIG. 6, the rotary tool 16 was pushed into the metal member 11 without performing the preheating step C1 to enter the metal member 11 and the resin member 12 to a depth not reaching the joint boundary surface 13. At this time, the molten resin 121 on the surface of the resin member melted in the region directly below the rotating tool flowed from the region directly below the pressing member toward the outside (in the direction of the arrow in FIG. 6). Push-in stirring step C2: Insertion amount 1.0 mm, insertion speed 6 mm / min, tool rotation speed 3000 rpm.

Next, as shown in FIG. 7, the rotary tool 16 was separated from the metal member 11, and the pressing region 111 of the metal member 11 pressed by the rotating tool 16 and the peripheral region thereof were forcibly cooled (solidification step). ). Specifically, when the time when the rotating tool 16 is separated from the metal member 11 is set to zero (seconds), 15 from the nozzle 115 to the pressing region 111 at a predetermined flow rate of 400 L / min from the predetermined cooling start time to the cooling end time. The pressing region 111 was forcibly cooled by blowing an air flow at ° C. to obtain the bonded structure shown in FIG. As shown in FIG. 7, the nozzle (inner diameter of 3 mm) has the tip of the nozzle at a position where the horizontal distance x from the joint center (that is, the center of the pressing region) is 15 mm and the height y from the joint center is 15 mm. The nozzles were arranged so that the nozzles were oriented toward the center of the joint.

(Joint strength)
As shown in FIG. 9, the joint structure of the metal member 11 and the resin member 12 is arranged in the jig 100. The jig 100 is configured so that a downward force acts on the upper end portion of the resin member 12 by pulling the jig 100 downward. By fixing the jig 100 and pulling the metal member 11 upward, a downward force acts on the upper end portion of the resin member 12, and the shear strength of the joint portion is not affected by the strength of the base material of the resin member 12. S was measured.
◎ ◎; 6.50 ≦ S (best);
⊚; 6.00 ≦ S <6.50 (excellent);
◯; 5.00 ≦ S <6.00 (good);
X; S <5.00 (defective).

(Temperature measurement)
At the cooling start time and the cooling end time, the interface temperature between the metal member 11 and the resin member 12 (7.5 mm from the center of the joint) in the pressing region 111 was measured by a K-type thermocouple.

(Cooling rate)
In the above temperature measurement, the interface temperature between the metal member 11 and the resin member 12 in the pressing region 111 was measured not only at the cooling start time and the cooling end time but also at the time between them. From the time _{T ts + 50} and Ts-50 ° C. and the time _{T ts-50} consisting of the ts + 50 ° C., to obtain an average cooling rate.

(Resin crystallinity (maximum crystallinity ratio))
The metal member 11 was forcibly peeled off from the obtained joint structure. The surface 120 on the metal member side of the resin member 12 is observed, and as shown in FIG. 2, on a circular line 62 (broken line) having a diameter of 1.5 × D1 concentric with the region 60 (diameter D1 (mm)) directly under the rotation tool. The sample was scraped off at any five points, and the crystallinity (maximum crystallinity ratio) was measured and calculated by a DSC (differential scanning calorimetry) device according to the above method.

[Comparative Example 1]
After the indentation stirring step, the joint structure of the resin member and the metal member is manufactured and evaluated by the same method as in Example 1 except that the resin member and the metal member are left to cool at room temperature (20 ° C.) without performing the solidification step. Was done.

[Examples 2 to 5 and Comparative Example 2]
A joint structure of a resin member and a metal member was manufactured and evaluated by the same method as in Example 1 except that the solidification process conditions were changed as described in the table.

The joining structure and joining method according to the present invention are useful for joining a metal member and a resin member in the fields of automobiles, railroad vehicles, aircraft, home appliances and the like.

1: Friction stir welding device 10: Work 11: Metal member 12: Resin member 13: Joint interface between metal member and resin member 16: Rotating tool 17: Jig 50: Joint structure 100: For measuring joint strength Jig 110: Immediately below the rotation tool for metal members P: Pressing area (planned pressing area)
111: Pressing area (after pressing)
121: Molten resin melted in the area directly below the rotating tool

Claims (21)

It is a joint structure of a metal member and a resin member.
The resin member is joined to the metal member in the melt-solidified region on the surface on the metal member side.
The melt-solidified region has a crystallinity of 80% or less (maximum crystallinity ratio), and is a bonded structure of a metal member and a resin member. The bonded structure between the metal member and the resin member according to claim 1, wherein the resin member contains one or more polymers selected from the group consisting of polyphenylene sulfide-based resin, polyamide-based resin, and polyolefin-based resin. The joint structure between a metal member and a resin member according to claim 1 or 2, wherein the metal member is made of aluminum or an aluminum alloy. The joint structure between a metal member and a resin member according to any one of claims 1 to 3, wherein the crystallinity (maximum crystallinity ratio) of the melt-solidified region is 40 to 80%. The joint structure between a metal member and a resin member according to any one of claims 1 to 3, wherein the crystallinity (maximum crystallinity ratio) of the melt-solidified region is 40 to 76%. The joint structure between a metal member and a resin member according to any one of claims 1 to 3, wherein the crystallinity (maximum crystallinity ratio) of the melt-solidified region is 40 to 72%. The joint structure between the metal member and the resin member according to any one of claims 1 to 6, wherein the melt-solidified region has a thickness of 0.50 mm or less on the surface of the resin member on the metal member side. Claimed by a thermal pressure joining method in which the metal member and the resin member are superposed, heat and pressure are applied by pressing from the metal member side by the pressing member, and the resin member is softened and melted and then solidified. Item 5. The joint structure between the metal member and the resin member according to any one of Items 1 to 7. The metal member and the resin member are superposed on each other, heat and pressure are applied by pressing from the metal member side by the pressing member, and the resin member is softened and melted and then solidified. It is a method of joining with
A method for joining a metal member and a resin member, wherein in the solidification step, forced cooling is performed so that the melt-solidified region of the resin member has a crystallization degree (maximum crystallinity ratio) of 80% or less. The method for joining a metal member and a resin member according to claim 9, wherein the forced cooling is performed at a cooling rate of 50 ° C./sec or more at a temperature in the melt-solidification region. The metal member and the resin member according to claim 9, wherein in the solidification step, the forced cooling is performed so that the melt-solidified region of the resin member has a crystallinity of 40 to 76% (maximum crystallinity ratio). How to join. The method for joining a metal member and a resin member according to claim 11, wherein the forced cooling is performed at a cooling rate of 150 ° C./sec or more at a temperature in the melt-solidification region. The metal member and the resin member according to claim 9, wherein in the solidification step, the forced cooling is performed so that the melt-solidified region of the resin member has a crystallinity of 40 to 72% (maximum crystallinity ratio). How to join. The method for joining a metal member and a resin member according to claim 13, wherein the forced cooling is performed at a cooling rate of more than 300 ° C./sec at a temperature in the melt-solidification region. A claim that the forced cooling is performed by separating the pressing member from the metal member and then blowing a gas flow onto the pressing region of the metal member pressed by the pressing member or the pressing region and its peripheral region. The method for joining a metal member and a resin member according to any one of 9 to 14. When the freezing point of the resin member is Ts (° C.), the resin temperature at the interface between the metal member in the pressing region and the resin member is changed from Ts + 50 (° C.) to Ts-50 (° C.) by the forced cooling. The method for joining a metal member and a resin member according to any one of claims 9 to 15. The thermal bonding method
The first step of superimposing the metal member and the resin member; and while rotating the rotating tool as the pressing member, the metal member is pressed to generate frictional heat, and the frictional heat softens and melts the resin member, and then the resin member is softened and melted. The method for joining a metal member and a resin member according to any one of claims 9 to 16, which is a friction stir welding method including a second step of solidifying and joining the metal member and the resin member. The second step comprises a push-in stirring step of pushing the rotating tool into the metal member to a depth that does not reach the joint interface between the metal member and the resin member before the solidification step. 17. The method for joining a metal member and a resin member according to 17. 18. The second step further comprises a preheating step of rotating the rotary tool with only the tip of the rotary tool in contact with the surface of the metal member prior to the push-in stirring step. The method for joining a metal member and a resin member according to the description. The second step is after the indentation stirring step, and before the solidification step, at a position where the rotating tool is inserted to a depth that does not reach the joining interface, stirring that continues the rotating operation of the rotating tool. The method for joining a metal member and a resin member according to claim 18 or 19, further comprising a maintenance step. The method for joining a metal member and a resin member according to any one of claims 9 to 20, wherein a joining structure between the metal member and the resin member according to any one of claims 1 to 8 is obtained.

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