JP4351025B2 - Method for joining heat-treatable aluminum alloy materials - Google Patents

Description

The present invention relates to a bonding how the heat-treatable aluminum alloy material, in particular, the heat treatment mold in the friction stir welding of aluminum alloy material, and effectively prevent the occurrence of fracture at that stir joining portion and the heat-affected zone, excellent ductility, are those concerning the bonding how that can be obtained advantageously and thus bonding material having excellent press formability.

  Conventionally, a wide variety of press products have been manufactured by using a plate material made of a heat-treatable aluminum alloy as a blank material for press molding and subjecting the blank material to press molding. In such a heat-treatable aluminum alloy sheet press, T4 tempering is softer and more ductile than T6 tempered aluminum alloy sheet that provides high strength. The aluminum alloy plate material is suitably employed.

  On the other hand, in recent years, after joining a plurality of aluminum alloy materials for the purpose of improving material yield by omitting cutting and trimming after press processing and simplifying the manufacturing process, press processing is performed on the joint materials. And bending are now being carried out. Specifically, a plurality of aluminum alloy materials are joined to each other by welding and integrated to produce a single press-forming blank material, a so-called tailored blank material, and this press-forming blank material For example, a technique for performing predetermined press molding has been widely employed in the field of manufacturing a press product for an interior panel of an automobile, for example.

  In such press forming technology, in addition to the above-mentioned improvement in material yield and simplification of the manufacturing process, a small metal plate that is difficult to use with general press forming technology is used as a material for forming blanks. As a blank material for press molding, if a blank material formed by integrally joining aluminum alloy materials having different thicknesses is used, a press with a necessary strength provided to a necessary part. Advantages such as being able to easily obtain a product can also be enjoyed.

  By the way, in order to obtain such a blank for press forming, various joining methods such as TIG welding, MIG welding, laser welding, friction stir welding, etc. have been conventionally employed as methods for joining aluminum alloy materials. However, among them, in the friction stir welding method, sufficient joining strength or joint strength can be realized by solid phase joining with less heat input and less softening and distortion than fusion welding. It's getting a lot of attention from where it can. However, even if the T4 tempered material is abutted and joined by such a friction stir welding method, softening in the heat-affected zone in the vicinity of the stir welded portion is unavoidable, and therefore the blank material so joined When the material is pressed without any post-treatment, the stress is locally concentrated in the heat-affected zone where the strength (hardness) is the lowest due to the heat generated during joining. It is often the case that the part is preferentially deformed and breakage occurs, and the breakage at the heat-affected part limits the press shape and its elongation or extension (deformation amount). Is a problem.

  On the other hand, (1) after heat-treatable aluminum alloy material is welded, an age hardening treatment is performed to improve the joint strength of the welded part (see, for example, Patent Documents 1 to 5), or (2) heat-treatable aluminum Many attempts have been made to improve the joint strength of the entire joint including the heat-affected zone by subjecting the alloy material to friction stir welding, followed by age hardening (see, for example, Patent Documents 6 to 8). .

  More specifically, as the above (1), in Patent Document 1, after flash butt welding of an aluminum alloy material, it is molded into a rim shape and heat-treated at 170 ° C. to 200 ° C. Manufactures strong aluminum alloy rims. In Patent Document 2, after welding an Al—Mg—Si alloy disk to an aluminum alloy rim, the welded portion is cooled at a cooling rate of 1 ° C./second or more, and subsequently, a temperature of 100 to 200 ° C. Thus, the strength of the aluminum alloy wheel is increased by performing the heat treatment for 5 to 60 minutes. Furthermore, in patent document 3, the heat softening phenomenon by welding heat is recovered by performing an aging treatment by heating at a temperature of 150 ° C. to 200 ° C. for 30 minutes or more after welding. In Patent Document 4, an Al-Mg-Si-based aluminum alloy extruded profile is welded and quenched, and then aging treatment is performed at 150 ° C to 220 ° C for 3 hours to 24 hours in order to improve the strength. Has been made clear. Furthermore, in Patent Document 5, joint strength and joint elongation are recovered by performing aging treatment for about 10 to 50 minutes at a temperature of 180 ° C. or lower after welding an excessive Si-type 6000 series aluminum alloy for molding. It has been made clear.

On the other hand, as the above (2), in Patent Document 6, the joint immediately after the friction stir welding is forcedly cooled so that the joint is in a quenched state. It has been clarified that a joint joint having a desired strength can be obtained by performing a treatment or a natural age hardening treatment. Further, in Patent Document 7, after the friction stir welding of the aluminum alloy T1 material with the heat-affected zone outside the stirring section heated to 300 ° C. or more within 1 minute, the joining member is heated to 300 ° C. It has been clarified that a joint strength of 95% or more can be secured with respect to the proof stress of the base material by applying an aging treatment at a low temperature for about 10 minutes to 24 hours. In addition, in Patent Document 8, an aluminum base alloy having an average crystal grain size of 100 to 5 × 10 ³ nm is joined by friction stir welding, and then an aging treatment is performed at a temperature of 100 to 200 ° C.

  As described above, by performing age hardening after melt welding or after friction stir welding, the joint strength is certainly improved, but the press formability and ductility of the bonding material have not been studied at all. Still, the strength of the heat-affected zone is the lowest, stress concentrates on the heat-affected zone and breaks easily, and there is a problem that the press shape and elongation (molding amount) are restricted.

JP-A-5-117826 JP-A-8-246116 JP-A-9-177974 Japanese Patent Laid-Open No. 11-199994 JP 2002-294281 A JP-A-11-104860 JP 2000-61663 A JP 2002-346770 A

  Here, in view of the circumstances as described above, the present inventors have intensively studied to eliminate problems such as press formability in the friction stir welding material of the heat-treatable aluminum alloy material. In addition, by controlling the strength balance of the base material, specifically, by setting the hardness of the stir welded portion and the heat affected zone to be equal to or higher than the hardness of the base material, the stir welded portion and the heat affected zone at the time of press molding. It was found that it was possible to avoid stress concentration on the surface.

  Further, the present inventors further controlled the strength balance between the stir welded portion, the heat affected zone and the base metal from the metallurgical viewpoint, after the friction stir weld, the heat affected zone and the base material. As a result of repeated research on each metal structure of the part, in the heat affected zone having the lowest hardness that occurs in the vicinity of the stir weld, the metal structure is restored (restored structure) I found out. Then, after the T4 tempered heat-treatable aluminum alloy material is friction stir welded, the obtained bonding material is subjected to a restoration process for once extinguishing the GP zone (or cluster), and the metal structure of the base material portion. Thus, the strength or hardness of the base material is effectively reduced to less than or equal to the strength or hardness of the heat-affected zone, and as a result, the stress on the heat-affected zone during press molding is reduced. Breaking due to concentration is effectively prevented, and the stress is effectively dispersed in the base material portion having a large area, so that the deformation amount of the entire joining material is advantageously increased. It has been found that the ductility or the elongation at break can be effectively increased, and the press formability can be advantageously improved.

Therefore, the present invention has been completed based on such knowledge, and the problem to be solved is that by controlling the strength balance of the stir welded portion, the heat affected zone and the base material, to prevent breakage in the heat affected zone, ductility, in the child provides a method of joining heat-treatable aluminum alloy material and thus the bonding material having excellent press formability advantageously obtained it is possible.

  In the present invention, in order to solve the above-described problems, the present invention is a method of friction stir welding a heat-treatable aluminum alloy material, (a) a step of T4 tempering the heat-treatable aluminum alloy material, and (b ) A step of friction stir welding the T4 tempered heat-treatable aluminum alloy material to obtain a joint material; and (c) before the GP zone is formed in the stir joint portion of the joint material, A first method is a joining method of heat-treatable aluminum alloy materials characterized by including a step of performing a restoration treatment on the surface.

  Moreover, in the desirable 2nd aspect in the joining method of the heat processing type aluminum alloy material according to this invention, the said restoration process heats up the said joining material to the temperature of 150 to 350 degreeC, and 300 degreeC is required at this temperature. It will be carried out by heat treatment that is held for a time of less than a second.

  Furthermore, in the third aspect of the method for joining heat-treatable aluminum alloy materials according to the present invention, a 6000 series aluminum alloy material is used as the heat-treatable aluminum alloy material, and the restoration treatment is performed at 200 ° C. The temperature is raised to ˜350 ° C., and the heat treatment is performed at such a temperature for 300 seconds or less.

  In addition, in the fourth aspect of the present invention, a 2000 series aluminum alloy material is used as the heat treatment type aluminum alloy material, and the restoration treatment raises the temperature of the bonding material to a temperature of 150 ° C. to 300 ° C. However, the temperature is maintained for 300 seconds or less at such temperature.

  Furthermore, according to the fifth aspect of the method for joining heat-treatable aluminum alloy materials according to the present invention, a 7000 series aluminum alloy material is used as the heat-treatable aluminum alloy material, and the restoration treatment comprises the steps of: The temperature is raised to a temperature of 150 ° C. to 250 ° C., and the heat treatment is performed at such a temperature for 300 seconds or less.

  By the way, in the present invention, as a preferred sixth aspect, there is adopted a method in which the restoration process is performed while the natural aging after the friction stir welding does not exceed 24 hours.

  In the seventh aspect of the method for joining heat-treatable aluminum alloy materials according to the present invention, the restoration treatment is performed by any heating means such as a salt bath, an oil bath, an air furnace, an iron, infrared heating or induction heating. A configuration performed by heat treatment is employed.

  Furthermore, in a desirable eighth aspect of the present invention, the friction stir welding is sequentially performed along the welded portion of the heat treated aluminum alloy material to be friction stir welded, and formed by the friction stir welding. The restoration process is sequentially performed on the bonding material including at least the stir bonding portion using a predetermined heating unit.

  According to the joining method of the heat treatment type aluminum alloy material according to the present invention as described above, after the T4 tempered heat treatment type aluminum alloy material is friction stir welded to obtain a joining material, a restoration treatment is performed on the joining material. The base material portion of the bonding material that has been T4 tempered is restored, that is, GP made of a fine compound formed in the metal structure of the base material portion (T4 tempered material). The zone (or cluster) is once extinguished, whereby the strength or hardness of the base material is effectively reduced. On the other hand, the stir welded portion having the same metal structure as that obtained when the solution treatment is performed by the friction stir welding maintains the same state even after the restoration treatment, and the strength or hardness is influenced by the base material and the heat effect. Higher than the part. In addition, the heat-affected zone that has been restored by friction stir welding becomes a restored structure in which age hardening is slightly induced by the subsequent restoration process, and the strength is the same as or higher than that of the restored base material. And lower than the stir joint. As a result, even if press molding is performed on the part including the joint part, it is advantageous that stress is locally concentrated in the heat-affected zone and fracture occurs in the heat-affected zone as in the past. As a result, stress is dispersed in the base material and the amount of deformation is increased, so that the elongation at break or ductility of the joining material can be effectively increased, and the press formability is advantageously improved. It becomes.

  In the method for joining heat-treatable aluminum alloy materials according to the present invention, in particular, if the third to fifth aspects described above are employed, the heat treatment conditions for the restoration treatment are dense according to the type of heat-treatable aluminum alloy material. Therefore, it is possible to more effectively control the strength balance of the stir welded portion, the heat affected zone, and the base material, and further advantageously obtain a joint material excellent in ductility and by extension, press formability. It can be done.

  Further, according to the sixth aspect of the method for joining heat-treatable aluminum alloy materials according to the present invention, the strength or hardness of the base material is more reliably determined than the strength or hardness of the stir welded portion or the heat-affected zone. Can also be lowered.

  Furthermore, according to the seventh aspect of the method for joining heat-treatable aluminum alloy materials according to the present invention, it is possible to advantageously carry out heat treatment under desired conditions.

  In addition, according to the eighth aspect of the method for joining heat-treatable aluminum alloy materials according to the present invention, for the pair of heat-treatable aluminum alloy materials to be joined, the friction stir welding operation and the restoring treatment operation are respectively Because it is designed to be performed successively on the same line without being performed separately at different locations, it is possible to continuously and efficiently produce a bonding material with excellent press formability as described above. Can be manufactured. In addition, after friction stir welding, age hardening due to natural aging until the restoration process is performed does not occur, so the strength or hardness of the base material is higher than the strength or hardness of the stir welded portion or heat affected zone. Thus, it is possible to lower the temperature more reliably.

  In addition, the press-forming bonding material according to the present invention is manufactured by the heat-treatable aluminum alloy material bonding method as described above. Is advantageously increased, and as a result, press forming with a free press shape and a larger processing amount can be realized.

  By the way, in the joining method of the heat treatment type aluminum alloy material according to the present invention as described above, as a material of the heat treatment type aluminum alloy material, conventionally known heat treatment type aluminum alloy capable of increasing the strength by age hardening heat treatment, For example, a JIS series alloy number of 6000 series (Al-Mg-Si series), 2000 series (Al-Cu-Mg series), 7000 series (Al-Zn-Mg series), etc. should be used. It becomes. More specifically, the 6000 series alloy may be one having a low Si content such as JIS A6061 alloy or JIS A6063 alloy, or one having a high Si content such as AA6016 alloy or AA6111 alloy. Examples of 2000 series alloys include JIS A2014 alloy, JIS A2017 alloy, JIS A2024 alloy and the like, while examples of 7000 series alloys include JIS A7075 alloy and JIS A7N01 alloy.

  In addition, as the shape of such a heat-treatable aluminum alloy material, if it has a shape capable of abutting the end of the joined part to be joined to the end of the joined part of the other party, Any of heat-treatable aluminum alloy materials (heat-treatable Al alloy materials) of various shapes, such as plate-like, tubular, rod-like, manufactured by known methods such as rolling, extrusion, forging, etc. In general, however, plate materials and extruded shapes are advantageously used.

  And among those shapes, a plate-shaped rolling material will be formed as follows, for example. That is, first, an aluminum alloy having a predetermined chemical composition is ingoted by a normal semi-continuous casting method, and then the obtained ingot is homogenized and then hot rolled. Is performed to produce a hot-rolled sheet. Also, an aluminum alloy melt adjusted to a predetermined chemical composition is directly produced as a continuous cast plate by a continuous casting method (molten rolling method). And these hot-rolled plates or continuous cast plates are cold-rolled to obtain flat plate-shaped plate materials having a predetermined thickness. In addition, before this cold rolling and in the middle of cold rolling, an intermediate annealing process may be implemented as needed.

  Next, friction stir welding is performed using a plurality of heat-treatable Al alloy materials such as the above-described plate materials and extruded shapes, but in the present invention, first, for heat-treatable Al alloy materials, T4 tempering is performed. That is, the heat-treatable Al alloy material is subjected to a solution treatment, quenched, and naturally aged to obtain a T4 tempered material. In particular, in the case of using a 6000 series alloy material, pre-aging within 24 hours at a temperature of 40 ° C. to 120 ° C. after quenching is performed as necessary in order to impart bake hardness (coating bake hardenability). Can be done.

  Thereafter, the heat-treated Al alloy material tempered by T4 is subjected to friction stir welding according to a conventional method, whereby a bonding material is obtained. For example, as shown in FIG. 1, first, two T4 tempered heat-treatable Al alloy materials (here, plate materials) are butted together and the two heat-treatable Al alloy materials 10a and 10b are butted together. Thus, the two heat-treatable Al alloy materials 10a and 10b are restrained according to a conventional method so that they do not move relatively in the longitudinal direction (joining direction) and the width direction. Then, the rotary tool 12 is rotated at high speed integrally with the pin 14 around the axis, and the pin 14 of the rotary tool 12 is inserted into the abutting portion 16 of the heat-treated Al alloy materials 10a and 10b that are abutted together. And the pin 14 are moved relatively along the butting portion 16, that is, in a direction perpendicular to the paper surface of FIG. 1, so that the two heat-treatable Al alloy materials 10 a and 10 b are moved at the butting portion 16. Friction stir welding is performed. At that time, the rotary tool 12 and the pin 14 are moved along the abutting portion, or the restrained heat treatment type Al alloy materials 10a and 10b are moved.

  As described above, when the friction stir welding is performed, the two heat-treatable Al alloy materials 10a and 10b are placed in the butt portions 16 of the two heat-treatable Al alloy materials 10a and 10b as shown in the upper part of FIG. The stir-joining part 18 straddling is formed so as to continuously extend in the longitudinal direction (the direction perpendicular to the paper surface in FIG. 2). This stir weld 18 reaches a temperature of 450 ° C. or higher by friction stir welding, so that a compound that contributes to the strength, such as Si, Mg, Cu, Zn, or an alloy component that forms a GP zone (or cluster) is solidified. As in the case of melting and solution treatment, the structure has a GP zone (or cluster) disappeared, that is, a so-called welded structure, and its hardness is temporarily lowest. Further, in the peripheral area adjacent to the stirring joint 18, there is a heat affected part 20 (HAZ part: a part affected by heat) that has been restored due to the influence of heat. The hardness of the part 20 is lower than that of the base material. On the other hand, the base material 22 that is not affected by heat caused by friction stir welding maintains the state of being T4 tempered and has the highest hardness.

  In the present invention, the metal structure immediately after the friction stir welding (that is, the stir welding part 18: the welded structure, the heat-affected part 20: the restored structure, the base material 22: the T4 tempered state) is substantial. The next restoration process is performed in a state maintained in the above. Here, the restoration process is a process for once extinguishing the GP zone (or cluster) formed by natural aging in the metal structure of the heat-treated Al alloy tempered by T4. In such a restoration treatment, the heat treatment type Al alloy bonding material is heated to a temperature of 150 ° C. to 350 ° C., and the temperature is raised for 300 seconds or less, more preferably 60 seconds or less. It is carried out by the heat treatment to be held. Further, the lower limit of the holding time is not particularly limited, and the temperature may be lowered immediately after the temperature is raised to the target temperature.

  In the above restoration process, when the heat treatment temperature (restoration process temperature) is less than 150 ° C. and is low, the GP zone (or cluster) does not disappear sufficiently, that is, the restoration is not sufficiently performed, and the mother While it becomes impossible to effectively reduce the strength or hardness of the material, when the heat treatment temperature exceeds 350 ° C., it becomes over-aged, and the precipitate formed in the metal structure becomes coarse and restored. The organization cannot be obtained. In addition, if the holding time at the heat treatment temperature is too long, it is restored, but age hardening or softening due to overaging occurs after restoration, and the desired restored structure cannot be obtained.

  Further, it is more desirable that the heat treatment temperature (restoration treatment temperature) as described above is set more finely according to the type of the heat treatment type Al alloy to be bonded, for example, as a heat treatment type Al alloy, 6000 series In the case of using an Al alloy, the temperature is preferably 200 ° C. to 350 ° C., more preferably 200 ° C. to 300 ° C., among the ranges described above. Moreover, in the case of 2000 series Al alloy, it is desirable to set it as 150 to 300 degreeC among the range mentioned above, More preferably, it is set as 180 to 300 degreeC. Further, in the case of a 7000 series Al alloy, it is desirable that the temperature is preferably 150 ° C. to 250 ° C., more preferably 170 ° C. to 250 ° C., within the range described above.

  Furthermore, when the temperature of the bonding material is raised to the target heat treatment temperature as described above, or when the temperature is lowered from the heat treatment temperature, the temperature rise rate or the temperature drop rate is not particularly limited, but the above-described restoration is performed. In order to effectively realize the above, the rate of temperature rise and the rate of temperature drop are each preferably set to 2 ° C./second or more, more preferably 4 ° C./second to 50 ° C./second. Is desirable.

  Here, the restoration process as described above may be performed after the friction stir welding operation, but the bonding material joined in the friction stir welding is formed into a metal structure over time due to natural aging. Changes occur and the strength or hardness changes. For this reason, the restoration process is performed in a state where the GP zone (or cluster) is present in the metal structure in the stir-joint portion 18 that is a welded structure having a large natural aging rate before the metal structure changes significantly. It is desirable to do this before it is formed. Specifically, after completion of the friction stir welding operation, the restoration process described above may be performed while the time for holding at room temperature does not exceed 24 hours, and more preferably does not exceed 6 hours. It is desirable. This is because if the time from the start of the friction stir welding operation to the start of the restoration process becomes too long, natural aging causes GP zones (or clusters) in the metal structure of the stir weld 18 and the heat affected zone 20 due to natural aging. Therefore, even if the joint material having such a metal structure is subjected to a restoration process, a trapezoidal hardness distribution described later cannot be realized, and the stir joint 18 and the heat affected zone 20 are not realized. This is because the strength or hardness of the steel is approximately the same as or slightly smaller than that of the base material, and breakage is likely to occur at the stir weld 18 and the heat affected zone 20 (particularly the heat affected zone 20).

  In addition, the heating method of such heat treatment (restoration treatment) is not particularly limited, and any heat treatment using a conventionally known heating means can be employed. For example, when an offline manufacturing process in which the restoration process and the friction stir welding process are performed discontinuously is adopted, a salt bath, an oil bath, an air furnace, an iron, infrared heating or induction heating is used. Of these, the heat treatment performed using any one of the heating means is preferably employed from the viewpoint of equipment and cost.

  Furthermore, in the present invention, it is possible to continuously perform the friction stir welding operation and the restoration processing operation on the same line, and when adopting such an online manufacturing process, for example, As shown in FIG. 3, the friction stir welding described above is sequentially performed along the welded portions (butting portions 16) to be friction stir welded of the heat treatment type Al alloy materials 10a and 10b. In the width direction (direction perpendicular to the joining direction) of the joining material including the part to be joined (stirring joining part 18) that has undergone stirring joining, with a sufficient length from the stirring joining part to the heat affected zone and the base material part Preferably, the restoration process is sequentially performed over the entire width direction. When such an on-line manufacturing process is employed, infrared heating, induction heating, laser heating, gas flame heating, or the like is suitably employed as the heating means. Even in this case, the restoration process (heat treatment) is performed not only in the stirring joint 18 and the vicinity thereof, but also in such a way that the stress applied during processing is effectively dispersed in the base material portion and a large amount of deformation can be secured. Needless to say, it needs to be applied to a wide range in the width direction of the material.

  Thus, by performing the predetermined heat treatment (restoration process) as described above, the GP 22 (or cluster) formed in the metal structure of the base material 22 once disappears and becomes a restored structure, thereby Strength or hardness is advantageously reduced. On the other hand, in the stir weld 18, a welded structure without a GP zone (or cluster) is maintained, and in the heat affected zone 20, the heat-affected zone 20 has a slight age hardening in the restored structure. This is the state in which this occurs. When the joining material having such a metallographic state is naturally aged at room temperature, the stir-joined portion 18 has the fastest age hardening rate and becomes the hardest. In addition, the heat affected zone 20 is the same as or higher than the base material 22 although its hardness is smaller than that of the stir weld 18. Further, the hardness of the base material 22 is smaller than that of the stirring joint 18 and the heat affected zone 20. As a result, the hardness distribution in the direction perpendicular to the joining direction in the joining material of the present embodiment is directed from the left and right base materials 22 to the stir joining portion 18 (butting portion 16) as shown in the middle part of FIG. It becomes a trapezoidal shape that becomes larger.

  As described above, in the joining method of the heat treatment type Al alloy material according to the present invention, the heat treatment type Al alloy material tempered by T4 is friction stir welded to obtain the joining material, and then restored to the joining material. Since the processing is performed, the strength balance of the stir weld 18, the heat affected zone 20, and the base material 22 is controlled, and a joint material in which the hardness of the base material 22 is minimized can be effectively obtained. . As a result, even if stress is applied to the bonding material, the stress concentration in the heat affected zone 20 is effectively prevented, and the stress is dispersed throughout the base material 22. As a result, the deformation amount of the entire bonding material can be advantageously increased, and thus press forming with a free press shape and a larger processing amount becomes possible. In other words, the press formability of the bonding material can be improved extremely effectively.

  And in the bonding material obtained as described above, since excellent press formability is imparted, it is advantageously used as a blank material for press molding, etc., and after being subjected to press molding It is advantageously used for shells and floors of ships, vehicles, airplanes, building materials, heat exchangers, antennas, automobile parts, bridges, and the like.

  Incidentally, when the restoration process as described above is not carried out, the stirring joint 18 has the same structure as that obtained when the solution treatment is carried out, and its hardness after natural aging is shown in the lower part of FIG. As shown, the same degree as the T4 tempered base material 22 is slightly smaller in hardness, while the heat affected zone 20 becomes a restored metal structure and becomes the softest. For this reason, when stress is applied to such a bonding material, the stress concentrates on the heat-affected zone 20 having the smallest hardness, and the heat-affected zone 20 is preferentially deformed, and breakage is likely to occur. Furthermore, according to the study by the present inventors, even if the restoration treatment as described above is performed on the joining material of the T4 tempered material joined by a fusion welding method such as TIG welding or MIG welding, Since a part of the heat-affected zone adjacent to the joint is once melted, the cast structure is altered and the ductility is lowered, and the trapezoidal hardness distribution as shown in the middle of FIG. It is recognized that the hardness is lowest in the heat-affected zone.

  The exemplary embodiments of the present invention have been described in detail above. However, the embodiments are merely examples, and the present invention is limited in any way by specific descriptions according to such embodiments. It should be understood that it is not interpreted.

  For example, in the above embodiment, an example is shown in which the plate thickness is the same and the plate-like heat treatment type Al alloy materials 10a and 10b made of the same heat treatment type Al alloy are used to join them. Heat-treatable Al alloy materials having different thicknesses may be joined, or heat-treatable Al alloy materials having different materials may be joined.

  In addition, although not listed one by one, the present invention can be implemented in a mode with various changes, modifications, improvements, and the like based on the knowledge of those skilled in the art. It goes without saying that all are included in the scope of the present invention without departing from the spirit of the invention.

  Hereinafter, representative examples of the present invention will be shown to clarify the present invention more specifically, but the present invention is not limited by the description of such examples. It goes without saying.

  First, 10 types of aluminum alloys (A to J) having chemical composition as shown in Table 1 below were ingoted by a DC casting method according to a conventional method. Each of the obtained ingots is subjected to homogenization treatment, hot rolling, and cold rolling to obtain an aluminum alloy sheet having a thickness of 1.0 mm, and further subjected to solution treatment and quenching. After undergoing natural aging for 7 days at room temperature, a T4 tempered material was obtained.

  Then, two T4 tempered materials are used, and the butt portions are butt-joined by a friction stir welding method (FSW method) in a state where the two end faces in the width direction are butt-matched to each other. The material was obtained. In addition, in the friction stir welding, a steel rotating tool was used, and a condition was adopted in which the tool was horizontally moved at a rotation speed of 1000 rpm and a welding speed of 400 mm / min. Further, eight grooves having a depth of 1 mm were provided at the end of the rotary tool for the purpose of cutting.

  Next, within 1 hour after the completion of the friction stir welding operation as described above, each joint material obtained above was subjected to a heat treatment (restoration process) under the conditions shown in Table 2 below.

  And after heat processing (after a restoration process), after storing the obtained test materials 1-10 for 7 days at 20 degreeC, as mentioned later about each of these test materials, a Vickers hardness test and a tensile test are carried out. The moldability test was performed, and the obtained results are shown in Table 2 below.

-Vickers hardness test-
A test piece was cut out in a direction perpendicular to the joining direction of the test materials. And after filling and polishing the cross section in the direction perpendicular to the joining direction of the test piece, using a Vickers hardness tester, according to JIS-Z-2244, with a load of 1 kgf, a stir welded portion, heat The hardness of the affected part and the base material part was measured.

-Tensile test-
A JIS-5 type tensile test piece was cut out so that the joining direction of the test material was perpendicular to the tensile direction in the tensile test, and the joint was positioned in the center. And using this test piece, the tensile test was done at room temperature according to JIS-Z-2241, and while measuring the tensile strength, the yield strength, and breaking elongation, the breaking position was confirmed.

-Molding test-
A disc-shaped test piece having a diameter of 120.0 mm was cut out so that the joint portion of the test material was located at the center. And after apply | coating a low-viscosity lubricating oil to the surface of this test piece, it used the Erichsen test machine and performed the extension process, and measured the limit shaping | molding height until a fracture | rupture. In order to prevent the material from flowing in, the overhanging process was carried out under the condition of a molding speed of 2 mm / s using a ball-head punch having a diameter of 50 mm, constraining the test piece with a die with a lock bead.

  As is clear from the results in Table 2, all of the test materials 1 to 10 have the lowest hardness of the base material among the stir welded portion, the heat affected zone, and the base material. In addition, from the results of the tensile test, the base material was not ruptured at the heat-affected zone, and the elongation at break was 16% or more. However, the limit molding height is a large value of 15.0 mm or more. From these results, it can be seen that the test materials 1 to 10 subjected to the restoration treatment according to the present invention have excellent press formability that can be sufficiently deformed during press forming.

<Comparative Example 1>
For comparison, 10 types of alloys (A to J) having the same chemical composition as those used in the above examples were processed under the same conditions as in the examples, and the thickness was 1. After making it a 0 mm aluminum alloy sheet, it was further subjected to solution treatment and quenching, and subjected to natural aging for 7 days at room temperature to obtain a T4 tempered material. Then, each aluminum alloy material that has been subjected to T4 tempering is used two by two, and in the state where the end surfaces in the width direction are butted against each other, the butted portions are subjected to friction stirring under the same conditions as in the above embodiment. Test materials 11 to 20 as bonding materials were produced by butt bonding by a bonding method (FSW method). After the friction stir welding, the obtained test materials 11 to 20 are stored as they are at 20 ° C. for 7 days without performing a heat treatment (restoration process), and then each of the test materials is described above. The Vickers hardness test, the tensile test, and the moldability test were performed, and the obtained results are also shown in Table 3 below.

  As is clear from the results in Table 3, since the test materials 11 to 20 were not subjected to the restoration treatment after the friction stir welding, all of the heat affected zone among the stir welded portion, the heat affected zone and the base material. The Vickers hardness is the lowest value, and the heat-affected zone is broken. In addition, it can be seen that each test material has a smaller elongation and a limit forming height of less than 15.0 mm compared to the test materials 1 to 10 made of the same aluminum alloy material.

<Comparative example 2>
For comparison, 10 types of alloys (A to J) having the same chemical composition as those used in the above examples were processed under the same conditions as in the examples, and the thickness was 1. After making it a 0 mm aluminum alloy sheet, it was further subjected to solution treatment and quenching, and subjected to natural aging for 7 days at room temperature to obtain a T4 tempered material. Then, each aluminum alloy material that has been subjected to T4 tempering is used two by two, and in the state where the end surfaces in the width direction are butted against each other, the butted portions are subjected to friction stirring under the same conditions as in the above embodiment. Butt bonding was performed by a bonding method (FSW method) to obtain a bonding material. And after completion | finish of friction stir welding operation, within 1 hour, with respect to each joining material obtained above, it heat-processes on the conditions shown in following Table 4, and obtained test materials 21-50 are 20 After storage at 7 ° C. for 7 days, each of these test materials was subjected to a Vickers hardness test, a tensile test, and a formability test as described above, and the results obtained are shown in Table 4 below. It was.

  As is apparent from the results of Table 4, since the test materials 21, 24, 27, 30, 33, 36, 39, 42, 45, and 48 all have a heat treatment temperature lower than the restoration treatment temperature, the base material portion The metal structure of the base material is not restored, the Vickers hardness of the base material is higher than that of the heat-affected zone, and the fracture occurs in the heat-affected zone with the smallest hardness. The elongation at break and the limit forming height are 16%, respectively. And less than 15.0 mm. Moreover, since all of the test materials 22, 25, 28, 31, 34, 37, 40, 43, 46, and 49 have a heat treatment temperature higher than the restoration treatment temperature, softening due to overaging occurs, and a desired restoration structure is obtained. However, although the base material fractured in the tensile test, the elongation at break and the limit molding height were low. Furthermore, since all of the test materials 23, 26, 29, 32, 35, 38, 41, 44, 47, and 50 are too heat-treated, softening due to overaging occurs, and a desired restored structure cannot be obtained. As a result, although the base material was ruptured in the tensile test, the elongation at break and the limit forming height were low.

<Comparative Example 3>
For comparison, 10 types of alloys (A to J) having the same chemical composition as those used in the above examples were processed under the same conditions as in the examples, and the thickness was 1. After making it a 0 mm aluminum alloy sheet, it was further subjected to solution treatment and quenching, and subjected to natural aging for 7 days at room temperature to obtain a T4 tempered material. Then, each aluminum alloy material that has been subjected to T4 tempering is used two by two, and in the state where the end surfaces in the width direction are butted against each other, the butted portions are friction-stirred under the same conditions as in the above embodiment. Butt bonding was performed by a bonding method (FSW method) to obtain a bonding material. And after completion | finish of friction stir welding operation, after storing at room temperature for 72 hours, with respect to each joining material obtained above, it heat-processes on the conditions shown in following Table 5, and obtained test materials 51-60 Was stored at 20 ° C. for 7 days, and each of the test materials was subjected to a Vickers hardness test, a tensile test, and a moldability test as described above, and the results obtained are shown in Table 5 below. It was shown together.

  As is clear from the results of Table 5, in all of the test materials 51 to 60, after the friction stir welding, the friction stir welding was performed on the age-hardened plate material. Since the Vickers hardness of the affected part and the base material is substantially the same and the Vickers hardness of the heat affected part is a slightly small value, the heat affected part is broken. It can also be seen that all the test materials have a small elongation at break of less than 16% and a limit molding height of less than 15.0 mm.

It is sectional explanatory drawing which shows an example of the process of carrying out friction stir welding of the heat treatment type Al alloy material, Comprising: The state (state before joining) which heat-treated type Al alloy material was faced | matched is shown. It is explanatory drawing for demonstrating the relationship between the stir welding part of the joining material obtained by friction stir welding, a heat affected zone, and a base material, and its hardness, Comprising: The flat plate-shaped heat processing type | mold to which friction stir welding was given A cross-sectional explanatory diagram of an Al alloy material, a graph showing the hardness distribution of a joint material that has been subjected to a restoration process after friction stir welding in accordance with the present invention, and a hardness of a conventional joint material that has been subjected only to friction stir welding A graph indicating the height distribution is arranged in association with the cross-sectional position of the bonding material. It is explanatory drawing which shows an example of the process of implementing a friction stir welding operation and a restoration process operation continuously on the same line according to this invention.

Explanation of symbols

10a, b Heat-treatable aluminum alloy material 12 Rotary tool 14 Pin 16 Butt portion 18 Stir weld 20 Heat-affected zone 22 Base material

Claims (8)

A step of T4 tempering the heat-treatable aluminum alloy material;
A step of friction stir welding the T4 tempered heat-treatable aluminum alloy material to obtain a bonding material;
A step of performing a restoration process on the bonding material before the GP zone is formed in the stirring bonded portion of the bonding material;
A heat-treatable aluminum alloy material joining method comprising:   The heat treatment type aluminum alloy according to claim 1, wherein the restoration treatment is performed by a heat treatment in which the bonding material is heated to a temperature of 150 ° C to 350 ° C and held at the temperature for a time of 300 seconds or less. Material joining method.   The heat treatment type aluminum alloy material is a 6000 series aluminum alloy material, and the restoration treatment heats the bonding material to a temperature of 200 ° C. to 350 ° C. and holds the bonding material at the temperature for 300 seconds or less. The method for joining heat-treatable aluminum alloy materials according to claim 1.   The heat treatment type aluminum alloy material is a 2000 series aluminum alloy material, and the restoration treatment heats the bonding material to a temperature of 150 ° C. to 300 ° C. and holds the bonding material at such a temperature for 300 seconds or less. The method for joining heat-treatable aluminum alloy materials according to claim 1.   The heat treatment type aluminum alloy material is a 7000 series aluminum alloy material, and the restoration treatment heats the bonding material to a temperature of 150 ° C. to 250 ° C. and holds the bonding material at such a temperature for 300 seconds or less. The method for joining heat-treatable aluminum alloy materials according to claim 1.   The method for joining heat-treatable aluminum alloy materials according to any one of claims 1 to 5, wherein the restoration treatment is performed while the natural aging after the friction stir welding does not exceed 24 hours.   The heat-treatable aluminum according to any one of claims 1 to 6, wherein the restoration treatment is performed by heat treatment using a salt bath, oil bath, air furnace, iron, infrared heating or induction heating. Alloy material joining method.   While the friction stir welding is sequentially performed along the welded portion of the heat-treatable aluminum alloy material to be friction stir welded, the joining material including at least the stir joint formed by the friction stir welding The method for joining heat-treatable aluminum alloy materials according to any one of claims 1 to 7, wherein the restoration process is sequentially performed using a predetermined heating means.

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