JP2011056534A - Friction stir welding method and different metal joined body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a friction stir welding method which can relatively easily produce a firmer joined body, and to provide a different metal joined body. <P>SOLUTION: In the friction stir welding method, an aluminum sheet 20 and a copper sheet 30 are superimposed, a rotating probe 10 is press-inserted from the side of the aluminum sheet 20 to the side of the copper sheet 30 so as to join the aluminum sheet 20 and the copper sheet 30. The probe 10 is press-inserted in such a manner that the temperature of the boundary between the aluminum sheet 20 and the copper sheet 30 reaches the recrystallization temperature of aluminum and copper or above and also less than the eutectic temperature of aluminum and copper. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a friction stir welding method and a dissimilar metal joined body.

  Conventionally, a dissimilar metal bonding structure in which a brittle intermetallic compound layer is intermittently formed at a bonding interface has been proposed (see Patent Document 1). According to this dissimilar metal joint structure, since the brittle intermetallic compound layer is intermittently formed, the cracks generated in the intermetallic compound layer are stopped by the base material having high ductility, and the strength is increased. it can.

  Also, when producing this dissimilar metal joint structure, the tips of two kinds of dissimilar metals having a shape such as a round bar are brought into contact with each other and pushed so that pressure is applied to the interface while rotating the member itself. Yes. At this time, the friction pressure, the number of revolutions, and the friction time are appropriate. In particular, the friction time is derived from the relationship between the temperature near the joint interface and the torque.

  Further, a friction stir welding method for producing a lap joint of dissimilar metals has been proposed (see Patent Document 2). In this friction stir welding method, an aluminum joint and a steel plate are overlapped, and a lap joint (that is, a point joined body) is produced by inserting a rotary probe from the aluminum alloy side to the vicinity of the steel plate. According to this method, an amorphous layer containing oxygen is formed at the bonding interface. The bonding interface composed of the amorphous layer prevents the formation of a brittle intermetallic compound at the bonding interface, relaxes stress concentration due to the difference in thermal shrinkage at the bonding interface between different metals, and strengthens the bonding.

JP 2003-48080 A JP 2008-6451 A

  However, in the dissimilar metal bonded structure described in Patent Document 1, the thickness of the intermetallic compound layer is 0.5 to 1.0 μm or 0.8 to 1.5 μm. For this reason, even if the intermetallic compound layer is too thick, mechanical properties (strength) are reduced when the thickness is at this level. That is, it is difficult to say that the dissimilar metal bonded structure described in Patent Document 1 is a strong bonded body.

  Furthermore, since the dissimilar metal joint structure described in Patent Document 1 is a method of rotating the pressed member itself, the applicable member is limited to a shape such as a round bar due to its nature, and can be placed at any place. It becomes difficult to form the joint. In addition, in the method described in Patent Document 2, it is necessary to form an amorphous layer containing oxygen at the bonding interface. However, it is difficult to form an amorphous layer containing oxygen at the bonding interface. Therefore, in the methods described in Patent Document 1 and Patent Document 2, it is difficult to produce a joined body.

  The present invention has been made to solve such conventional problems, and the object of the present invention is to provide a friction stir welding method capable of relatively easily producing a stronger bonded body, and a dissimilar metal bonded body. Is to provide.

  The friction stir welding method of the present invention is a friction stir welding method in which an aluminum plate and a copper plate are overlapped and rotated, and a probe that rotates is pressed from the aluminum plate side to the copper plate side to join the aluminum plate and the copper plate, The probe is inserted under pressure so that the interface temperature between the aluminum plate and the copper plate is equal to or higher than the recrystallization temperature of aluminum and copper and lower than the eutectic temperature of aluminum and copper.

  According to this friction stir welding method, a probe that rotates by superimposing an aluminum plate and a copper plate is pressed and inserted from the aluminum plate side to the copper plate side to join the aluminum plate and the copper plate. It becomes a point and is not limited to the joint location. Furthermore, it is not necessary to rotate the rod-shaped metal, and the joined body can be manufactured without being restricted by the shape of the metal to be joined.

  Further, the probe is inserted under pressure so that the interface temperature between the aluminum plate and the copper plate is equal to or higher than the recrystallization temperature of copper and lower than the eutectic temperature of aluminum and copper. Here, since the recrystallization temperature of aluminum is about 200 degrees and the recrystallization temperature of copper is 250 degrees, the interface temperature is set to 250 degrees or more. When the temperature is higher than this temperature, the oxide film formed in advance on the aluminum surface is destroyed, and a substance that causes a decrease in bonding strength when a bonded body is formed is removed. In addition, the eutectic temperature of aluminum and copper is about 548 degrees, and if it is less than this temperature, a large amount of intermetallic compound of aluminum and copper is not generated, and the thickness of the intermetallic compound layer becomes too large. Therefore, it is difficult to cause a decrease in bonding strength. Therefore, a stronger bonded body can be obtained. In particular, the present invention does not have difficulty in production by forming an amorphous layer.

  As described above, a stronger bonded body can be produced relatively easily.

  In the friction stir welding method according to the present invention, it is preferable that the probe is pressure-inserted so that the interface temperature between the aluminum plate and the copper plate is 300 ° C. or higher and lower than the eutectic temperature of aluminum and copper. .

  According to this friction stir welding method, the probe is pressure-inserted so that the interface temperature is 300 ° C. or higher and lower than the eutectic temperature of aluminum and copper. Here, when producing a joined body, it is desirable to complete the production of the joined body as soon as possible. Here, when the interface temperature is near the recrystallization temperature of aluminum and copper, it takes time to destroy the oxide film of aluminum, and if the probe is not kept rotating for the time until the end of the oxide film breakage, it becomes stronger. It becomes impossible to obtain a joined body. However, when the interface temperature is set to 300 ° C. or higher, the fabrication can be completed when the interface temperature reaches the target temperature, leading to a shortening of the fabrication time and a stronger bonded body. Can be obtained.

  Further, the dissimilar metal joined body of the present invention is a dissimilar metal joined body produced by the above friction stir welding method, and the thickness of the intermetallic compound layer at the interface between the aluminum plate and the copper plate is 200 nm or less. It is characterized by.

  According to this joined body, since the thickness of the intermetallic compound layer at the interface between the aluminum plate and the copper plate is 200 nm or less, the shear strength ratio is approximately 100%, and a stronger joined body can be obtained.

  According to the present invention, a stronger bonded body can be produced relatively easily.

It is the schematic which shows the friction stir welding method which concerns on embodiment of this invention, Comprising: (a) shows a 1st process, (b) shows a 2nd process, (c) shows a 3rd process. Show. It is sectional drawing which shows the dissimilar metal joining body obtained by the friction stir welding method which concerns on this embodiment, Comprising: (a) shows the cross section at the time of joining below recrystallization temperature, (b) is from recrystallization temperature. A cross section when bonded at a slightly higher temperature is shown, and (c) shows a cross section when bonded at a temperature slightly lower than the eutectic temperature. It is a figure which shows the measurement interface temperature for every indentation pressure and the remaining thickness ratio of an aluminum plate. It is a figure which shows the correlation with interface temperature and shear strength (joining strength). It is a figure which shows the correlation with the thickness of an intermetallic compound layer, and the ratio of shear strength.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a friction stir welding method according to an embodiment of the present invention, in which (a) shows a first step, (b) shows a second step, and (c) shows a first step. 3 steps are shown.

  As shown in FIGS. 1A to 1C, the friction stir welding method according to the present embodiment softens the member by generating frictional heat by pressing the probe 10 with a strong force while rotating the probe 10. In this method, the members around the probe 10 are plastically flowed by the rotational force of the probe 10 to integrate a plurality of members. The members joined in the present embodiment are the aluminum plate 20 and the copper plate 30.

  Specifically, as shown in FIG. 1A, the aluminum plate 20 and the copper plate 30 are arranged so that the joining portions overlap each other and fixed with a jig or the like. Next, as shown in FIG. 1B, the rotated probe 10 is pressure-inserted from the side of the aluminum plate 20 which is a low melting point material. At this time, the probe 10 is pressed and inserted only into the aluminum plate 20 so as not to penetrate the aluminum plate 20. Conditions for inserting the probe 10 under pressure include the number of rotations of the probe 10, the amount of pushing, the pushing load, the pushing speed, and the holding time. When the probe 10 reaches a preset condition, the probe 10 is pulled out as shown in FIG.

  Thereby, the aluminum plate 20 and the copper plate 30 are integrated, and the joined body of a dissimilar metal will be formed. In particular, according to this joining method, the insertion location of the probe 10 becomes a joining point, and the joining location is not limited. Furthermore, it is not necessary to rotate the rod-shaped metal, and the joined body can be manufactured without being restricted by the shape of the metal to be joined. In addition, according to the method of this embodiment, since the probe 10 is press-inserted into the aluminum plate 20 of the joined body, an insertion mark (concave mark) 20 a is formed on the aluminum plate 20.

  In the friction stir welding method according to this embodiment, the interface temperature between the aluminum plate 20 and the copper plate 30 is set to satisfy the following temperature condition. That is, in this embodiment, the interface temperature between the aluminum plate 20 and the copper plate 30 is set to be equal to or higher than the recrystallization temperature of aluminum and copper. Here, the recrystallization temperature of aluminum is about 200 degrees, and the recrystallization temperature of copper is 250 degrees. For this reason, the interface temperature is substantially 250 degrees or more. If the temperature is higher than this temperature, the oxide film formed in advance on the aluminum surface is destroyed. Here, the oxide film is a substance that causes a decrease in bonding strength when a dissimilar metal bonded body is formed. For this reason, by setting the interface temperature to 250 ° C. or higher, the oxide film is removed, and a bonded body with higher bonding strength can be obtained.

  Furthermore, in the friction stir welding method according to the present embodiment, the interface temperature is set to be lower than the eutectic temperature of aluminum and copper. Here, the eutectic temperature of aluminum and copper is about 548 degrees. When the interface temperature is equal to or higher than the eutectic temperature, a large amount of intermetallic compounds tend to be generated. In particular, it is known that intermetallic compounds are brittle, and when a large amount of intermetallic compound is produced and the intermetallic compound layer becomes thick, the bonding strength is reduced. For this reason, when the interface temperature is lower than the eutectic temperature, the intermetallic compound layer does not become too thick, and a bonded body with higher bonding strength can be obtained.

  Furthermore, in this embodiment, it is desirable that the interface temperature is set to be 300 ° C. or higher. When producing a joined body, it is desirable to complete the production of the joined body as soon as possible. Here, when the interface temperature is in the vicinity of the recrystallization temperature between aluminum and copper, it takes time to destroy the oxide film of aluminum. If the probe 10 is not rotated for the time until the destruction of the oxide film, it is stronger. It becomes impossible to obtain a proper joined body. However, when the interface temperature is set to 300 ° C. or higher, the fabrication can be completed when the interface temperature reaches the target temperature, leading to a shortening of the fabrication time and a stronger bonded body. Can be obtained.

  FIG. 2 is a cross-sectional view showing a dissimilar metal joined body obtained by the friction stir welding method according to the present embodiment, wherein (a) shows a cross section when joined at a temperature lower than the recrystallization temperature, and (b) shows The cross section when bonded at a temperature slightly higher than the recrystallization temperature is shown, and (c) shows the cross section when bonded at a temperature slightly lower than the eutectic temperature.

  When bonding is performed so that the interface temperature is lower than the recrystallization temperature, the aluminum oxide film is difficult to be removed. For this reason, as shown in FIG. 2A, the oxide film 40 is interposed between the aluminum plate 20 and the copper plate 30 and the bonding strength is reduced.

  Further, when the bonding is performed so that the interface temperature is slightly higher than the recrystallization temperature, the aluminum oxide film 40 is suitably destroyed. Therefore, as shown in FIG. 2B, the oxide film 40 is not interposed between the aluminum plate 20 and the copper plate 30, the contact area between the aluminum plate 20 and the copper plate 30 is increased, and the bonding strength is improved. Will be.

  The same applies to the case where bonding is performed so that the interface temperature is slightly lower than the eutectic temperature. That is, as shown in FIG. 2C, the oxide film 40 is not interposed between the aluminum plate 20 and the copper plate 30, the contact area between the aluminum plate 20 and the copper plate 30 is increased, and the bonding strength is improved. It will be.

  Here, in the example shown in FIG. 2B and FIG. 2C, the thickness (amount) of the intermetallic compound layer 50 is different. This is because the one closer to the eutectic temperature (example in FIG. 2C) tends to produce more intermetallic compounds. In the example shown in FIG. 2C, more intermetallic compounds are produced than in the example shown in FIG. 2B, but the interface temperature is lower than the eutectic temperature, so the interface temperature is equal to or higher than the eutectic temperature. It can be said that the amount of the intermetallic compound is remarkably small as compared with the case.

  Next, examples will be described. An aluminum plate 20 having a thickness of 1.5 mm and a copper plate 30 having a thickness of 1.0 mm were superposed, and a 6 mm diameter probe 10 was pressure-inserted from the aluminum plate 20 side under the conditions shown in FIG. Further, after the pressure insertion, the probe 10 was pulled out from the aluminum plate 20 without being held when the remaining thickness ratio shown in FIG. 3 was reached (that is, the holding time was set to “0”).

  FIG. 3 is a diagram showing the measured interface temperature for each indentation pressure and the remaining thickness ratio of the aluminum plate 20.

  First, when the probe 10 is press-inserted so that the remaining thickness ratio of the aluminum plate 20 is 0.33 (that is, when the probe 10 is pushed into the aluminum plate 20 by 1.0 mm), the interface temperature is The indentation pressure was about 372 degrees at 106 MPa, the indentation pressure was about 360 degrees at 124 MPa, and the indentation pressure was 142 MPa at about 316 degrees.

  Similarly, when the probe 10 is pressure-inserted so that the remaining thickness ratio of the aluminum plate 20 is 0.47 (that is, when the probe 10 is pushed into the aluminum plate 20 by 0.8 mm), the interface temperature Was about 345 degrees at an indentation pressure of 88 MPa, about 361 degrees at an indentation pressure of 106 MPa, about 337 degrees at an indentation pressure of 124 MPa, and about 301 degrees at an indentation pressure of 142 MPa.

  When the probe 10 is pressure-inserted so that the remaining thickness ratio of the aluminum plate 20 is 0.60 (that is, when the probe 10 is pushed by 0.6 mm into the aluminum plate 20), the interface temperature is The indentation pressure was about 338 degrees at 88 MPa, the indentation pressure was about 329 degrees at 106 MPa, the indentation pressure was about 320 degrees at 124 MPa, and the indentation pressure was 142 MPa at about 290 degrees.

  When the probe 10 is pressure-inserted so that the remaining thickness ratio of the aluminum plate 20 is 0.73 (that is, when the probe 10 is pushed into the aluminum plate 20 by 0.4 mm), the interface temperature is The indentation pressure was about 296 degrees at 88 MPa, the indentation pressure was about 288 degrees at 106 MPa, the indentation pressure was about 257 degrees at 124 MPa, and the indentation pressure was 142 MPa at about 225 degrees.

  Further, when the probe 10 is pressure-inserted so that the remaining thickness ratio of the aluminum plate 20 is 0.87 (that is, when the probe 10 is pushed into the aluminum plate 20 by 0.2 mm), the interface temperature is The pressure was about 244 degrees at an indentation pressure of 88 MPa, about 237 degrees at an indentation pressure of 106 MPa, about 202 degrees at an indentation pressure of 124 MPa, and about 187 degrees at an indentation pressure of 142 MPa.

  FIG. 4 is a diagram showing the correlation between the interface temperature and the shear strength (bonding strength). The correlation shown in FIG. 4 is measured with the retention time set to “0” as shown in FIG. As shown in FIG. 4, the shear strength is approximately 0 N when the interface temperature is about 200 degrees. This is because the interface temperature is lower than the recrystallization temperature, the oxide film is not destroyed, and the contact area between the metals of aluminum and copper is small.

  The shear strength is 155 N when the interface temperature is 260 degrees. That is, since the interface temperature exceeds the recrystallization temperature, the oxide film is destroyed and the contact area between the metals of aluminum and copper increases. In the embodiment shown in FIG. 3, the holding time is “0”. For this reason, the oxide film is not sufficiently broken and the shear strength is not sufficiently increased.

  However, when the interface temperature exceeds 300 ° C. and is in the range of about 310 ° C. to about 450 ° C., the shear strength is 800 N to 1000 N, which increases dramatically. This is because, as described above, the oxide film is sufficiently broken even without the holding time, and the contact area between the metals of aluminum and copper is sufficiently increased.

  When the interface temperature is 540 degrees, which is slightly lower than the eutectic temperature, the shear strength is about 720N. This is because a relatively large amount of brittle intermetallic compound was generated although the oxide film was sufficiently destroyed.

  Furthermore, when the interface temperature is 670 ° C. exceeding the eutectic temperature, the shear strength is about 540 N, indicating a decrease. This is because the interfacial temperature is equal to or higher than the eutectic temperature, so that an intermetallic compound is produced in such a large amount as to affect the mechanical strength.

  Thus, the interface temperature is preferably higher than the recrystallization temperature of aluminum and copper and lower than the eutectic temperature, more preferably 300 degrees or higher and lower than the eutectic temperature.

  FIG. 3 will be referred to again. In FIG. 3, the case where the shear strength is about 690 N or more is “strength OK”, and the case where the shear strength is less than about 690 is “strength NG”. Moreover, if the aluminum plate 20 and the copper plate 30 are joined to some extent, the conductivity between the aluminum plate 20 and the copper plate 30 can be ensured, and a dissimilar metal joined body can be used as the conductive member. In FIG. 3, the case where it can be used as a conductive member is referred to as “conductive OK”, and the case where it cannot be used as a conductive member is referred to as “conductive NG”.

  As is apparent from FIG. 3, when the interface temperature is higher than the recrystallization temperature of aluminum and copper and lower than the eutectic temperature, a dissimilar metal joined body can be used as the conductive member although there is a slight problem in strength. (Ie “conductive OK”). Furthermore, when the interface temperature is set to 300 ° C. or higher, it is possible to provide a dissimilar metal joined body that is excellent in strength and can be used as a conductive member (that is, “strength OK”). In the example shown in FIG. 3, since the holding time is “0”, the “strength NG” is in the range of the recrystallization temperature of aluminum and copper to less than 300 ° C., but the holding time is sufficiently secured. For example, even in this temperature range, “strength OK” is obtained.

  Next, the intermetallic compound of the dissimilar metal joined body produced by the friction stir welding method according to the present embodiment will be described. In the following description, the holding time is “0” as described above.

  First, when the 6 mm diameter probe 10 was used and the interface temperature was 320 ° C., the thickness of the intermetallic compound layer was about 20 nm to 30 nm. When the 6 mm diameter probe 10 was used and the interface temperature was 340 ° C., the thickness of the intermetallic compound layer was about 80 nm.

  Similarly, when the probe 10 having a diameter of 10 mm was used and the interface temperature was 420 ° C., the thickness of the intermetallic compound layer was about 60 nm to 130 nm. When the probe 10 having a diameter of 10 mm was used and the interface temperature was 490 ° C., the thickness of the intermetallic compound layer was about 200 nm.

  Thus, the dissimilar metal joined body produced by the friction stir welding method according to the present embodiment has an intermetallic compound layer thickness of 200 nm or less.

  On the other hand, when the 10 mm diameter probe 10 was used and the interface temperature was set to 570 ° C. which is equal to or higher than the eutectic temperature, the thickness of the intermetallic compound layer was about 50000 nm to 60000 nm. Thus, when the interface temperature is equal to or higher than the eutectic temperature, a large amount of intermetallic compounds are generated, and the intermetallic compound layer becomes thick. Thereby, joining strength will fall.

  FIG. 5 is a diagram showing a correlation between the thickness of the intermetallic compound layer and the ratio of the shear strength. As shown in FIG. 5, the shear strength ratio approaches 100% as the thickness of the intermetallic compound layer approaches “0”. In particular, in the dissimilar metal joined body according to this embodiment, the thickness of the intermetallic compound layer is 200 nm or less, and the shear strength ratio is approximately 100%.

  On the other hand, when the interface temperature is equal to or higher than the eutectic temperature and the thickness of the intermetallic compound layer is about 50000 nm to 60000 nm, the shear strength ratio is about 55%. Thus, it can be said that the dissimilar metal joined body produced by the friction stir welding method according to the present embodiment has a high shear strength ratio and is excellent in joining strength.

  Thus, according to the friction stir welding method according to this embodiment, the aluminum plate 20 and the copper plate 30 are overlapped and rotated, and the probe 10 that rotates is pressed and inserted from the aluminum plate 20 side to the copper plate 30 side. Since 20 and the copper plate 30 are joined, the insertion location of the probe 10 becomes a joining point, and the joining location is not limited. Furthermore, it is not necessary to rotate the rod-shaped metal, and the joined body can be manufactured without being restricted by the shape of the metal to be joined.

  Further, the probe 10 is inserted under pressure so that the interface temperature between the aluminum plate 20 and the copper plate 30 is equal to or higher than the recrystallization temperature of copper and lower than the eutectic temperature of aluminum and copper. Here, since the recrystallization temperature of aluminum is about 200 degrees and the recrystallization temperature of copper is 250 degrees, the interface temperature is set to 250 degrees or more. When the temperature is higher than this temperature, the oxide film formed in advance on the aluminum surface is destroyed, and a substance that causes a decrease in bonding strength when a bonded body is formed is removed. In addition, the eutectic temperature of aluminum and copper is about 548 degrees, and if it is less than this temperature, a large amount of intermetallic compound of aluminum and copper is not generated, and the thickness of the intermetallic compound layer becomes too large. Therefore, it is difficult to cause a decrease in bonding strength. Therefore, a stronger bonded body can be obtained. In particular, the present invention does not have difficulty in production by forming an amorphous layer.

  As described above, a stronger bonded body can be produced relatively easily.

  Further, the probe 10 is inserted under pressure so that the interface temperature is 300 ° C. or higher and lower than the eutectic temperature of aluminum and copper. Here, when producing a joined body, it is desirable to complete the production of the joined body as soon as possible. Here, when the interface temperature is in the vicinity of the recrystallization temperature of aluminum and copper, it takes time to destroy the oxide film of aluminum, and if the probe 10 is not rotated for the time until the destruction of the oxide film, it is stronger. It becomes impossible to obtain a joined body. However, when the interface temperature is set to 300 ° C. or higher, the fabrication can be completed when the interface temperature reaches the target temperature, leading to a shortening of the fabrication time and a stronger bonded body. Can be obtained.

  Furthermore, according to the dissimilar metal joined body according to the present embodiment, since the thickness of the intermetallic compound layer at the interface between the aluminum plate 20 and the copper plate 30 is 200 nm or less, the shear strength ratio is approximately 100%, which is stronger. It can be set as a simple joined body.

  As described above, the present invention has been described based on the embodiment, but the present invention is not limited to the above embodiment, and may be modified without departing from the gist of the present invention. For example, in the friction stir welding method according to this embodiment, the holding time, the remaining thickness ratio of the aluminum plate, the pressing pressure of the rotary tool, and the like can be changed as appropriate. The material of the probe 10 can be selected as appropriate.

10 ... Probe 20 ... Aluminum plate 30 ... Copper plate

Claims (3)

A friction stir welding method for joining an aluminum plate and a copper plate by pressing and inserting a probe that rotates by overlapping an aluminum plate and a copper plate from the aluminum plate side to the copper plate side,
Friction stir welding method, wherein the probe is inserted under pressure so that the interface temperature between the aluminum plate and the copper plate is equal to or higher than the recrystallization temperature of aluminum and copper and lower than the eutectic temperature of aluminum and copper. . 2. The friction stir welding according to claim 1, wherein the probe is inserted under pressure so that an interface temperature between the aluminum plate and the copper plate is 300 ° C. or higher and lower than a eutectic temperature of aluminum and copper. Method. A dissimilar metal joined body produced by the friction stir welding method according to claim 1 or 2,
The thickness of the intermetallic compound layer in the interface of an aluminum plate and a copper plate is 200 nm or less.

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