JP4351024B2 - Friction stir welding method for heat-treatable aluminum alloy material - Google Patents

Description

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

  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 the friction stir welding method, softening in the heat affected zone in the vicinity of the stir welded portion is not avoided, and therefore, the blank material manufactured by friction stir welding is used. When press-molding as it is without any post-treatment, stress is concentrated locally on the heat-affected zone with the lowest strength or hardness, and the heat-affected zone is preferentially deformed and fractured. This often occurs, and the breakage at the heat-affected zone limits the press shape and its elongation or elongation (deformation amount).

  On the other hand, using a heat-treatable aluminum alloy material as a member to be joined, and after friction stir welding it, an attempt to improve the joint strength of the entire joint part including the heat affected part by applying age hardening treatment, Many have been made (for example, see Patent Documents 1 to 3). Moreover, in patent document 4, prior to performing TIG welding, MIG welding, laser welding, friction stir welding, etc. for the purpose of ensuring high joint strength, the maximum strength is preliminarily applied to the aluminum alloy material. The adoption of a sub-aging treatment in which the aging treatment is performed at a temperature lower than or shorter than the aging treatment conditions obtained has been clarified. As such sub-aging treatment conditions, it has been clarified in the examples that the heat treatment is performed at a furnace temperature of 160 ° C. to 200 ° C. for 3 hours.

  Thus, although the joint strength is improved by performing age hardening treatment after joining or sub-aging treatment before joining, the press formability and ductility of the joining material have not been studied at all. However, the strength of the heat-affected zone is still lower than that of the joint and the base material, stress concentrates on the heat-affected zone, and breakage easily occurs, and the press shape and elongation (molding amount) are restricted. Is inherent.

  Moreover, in patent document 5, prior to friction stir welding, the front part of the moving direction of the probe is 500 ° C. or less, preferably 100 ° C. to 300 ° C., using an external heat source such as a laser beam, a gas flame, or a heater. A friction stir welding method that heats to a temperature (forward heating) has been proposed, which enables good bonding without causing poor bonding and improves the bonding speed, It has been clarified that the lifetime can be extended. Further, Patent Document 6 and Patent Document 7 describe a welding torch at the front and rear of the joint portion in order to shorten the time until the friction stir welding is started or to prevent cracking of the joint portion including the heat affected zone. There has also been proposed a method of heating in a temperature range of 100 ° C. to 300 ° C. by induction heating. However, these forward heating methods are merely intended to reduce deformation resistance and start time, although heat treatment is performed on the aluminum alloy material prior to friction stir welding. However, there is no purpose of modifying the aluminum alloy material.

JP-A-11-104860 JP 2000-61663 A JP 2002-346770 A JP 2001-321948 A Japanese Patent Laid-Open No. 10-225781 JP 2003-80381 A JP 2003-94175 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, the T4 tempered heat-treatable aluminum alloy material is preliminarily subjected to a restoration process for once eliminating the GP zone (or cluster) in the metal structure, and after the restoration process, a friction stir welding is performed. In this case, the strength or hardness of the base material is effectively reduced to the same level or lower than the strength or hardness of the heat-affected zone, and as a result, stress concentration on the heat-affected zone during press molding Is advantageously prevented, and the stress is effectively dispersed in the base material portion having a large area, which advantageously increases the amount of deformation of the entire joint material, thereby increasing the ductility of the joint material. It has been found that 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, Providing a friction stir welding method for a heat-treatable aluminum alloy material that can advantageously obtain a joint material excellent in ductility and by extension, press formability by preventing breakage in a heat-affected zone, and such heat treatment mold An object of the present invention is to provide a press-molding bonding material with improved press-formability, which is advantageously produced by a friction stir welding method for an aluminum alloy material.

Then, in the present invention, in order to solve the aforementioned problems, a method of friction stir welding a base metal made of heat-treatable aluminum alloy was subjected to T4 tempered in the heat treatment type aluminum alloy Thereafter, the T4 tempered heat-treatable aluminum alloy material is heated to a temperature of 150 ° C. to 350 ° C., and a restoration treatment is performed by performing a heat treatment that is held for 300 seconds or less at the temperature , Then, the heat-treatable aluminum alloy material that has been subjected to the restoration treatment is friction stir welded , and the resulting stir welded portion has a hardness greater than the hardness of the base material and the stirrer from the base material. A friction stir welding method for heat-treatable aluminum alloy material characterized in that the hardness increases toward the joint portion is the first aspect.

Moreover, in the desirable 2nd aspect in the friction stir welding method of the heat processing type aluminum alloy material according to this invention, the temperature increase rate and temperature decrease rate in the said reconstruction process are 2 degree-C / sec or more, respectively .

  Furthermore, in the third aspect of the friction stir welding method for heat-treatable aluminum alloy material 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 tempered by T4. The heat treatment type aluminum alloy material is heated to a temperature of 200 ° C. to 350 ° C., and the heat treatment type aluminum alloy material is carried out by a heat treatment that is held at the 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 is performed at a temperature of 150 ° C. The temperature is raised to a temperature of 300 ° C., and the heat treatment is performed at such a temperature for 300 seconds or less.

  Furthermore, according to the fifth aspect of the friction stir welding method for heat-treatable aluminum alloy material according to the present invention, a 7000 series aluminum alloy material is used as the heat-treatable aluminum alloy material, and the restoration treatment is performed in the T4 mode. The heat-treated aluminum alloy material is heated to a temperature of 150 ° C. to 250 ° C., and the heat treatment is carried out by maintaining the temperature for 300 seconds or less.

  By the way, in the present invention, as a preferable sixth aspect thereof, after the restoration treatment, the heat treatment type aluminum alloy material subjected to the restoration treatment has an increase in tensile strength of 10 MPa due to natural aging. A method is adopted in which the friction stir welding is performed while the temperature does not exceed.

  Moreover, in the seventh aspect of the friction stir welding method for heat-treatable aluminum alloy materials according to the present invention, the restoration treatment is performed by a salt bath, an oil bath, an air furnace, infrared heating or induction heating. A configuration performed by heat treatment is employed.

  Furthermore, in a desirable eighth aspect of the present invention, the restoration process is sequentially performed by using a predetermined heating means along a bonded portion of the heat-treatable aluminum alloy material to be friction stir welded. Then, the friction stir welding is sequentially performed on the joined parts that have been restored.

  Further, the present invention also includes a press-forming bonding material obtained by the friction stir welding method for heat-treatable aluminum alloy material as described above.

  According to the friction stir welding method of the heat treatment type aluminum alloy material according to the present invention as described above, the heat treatment type aluminum alloy material was subjected to the T4 tempering and further subjected to the restoration treatment, so that the T4 tempering was performed. A GP zone (or cluster) made of a fine compound formed in the metal structure of the aluminum alloy material is once extinguished. When the heat-treatable aluminum alloy materials in which the GP zone has disappeared are brought into contact with each other and friction stir welding is performed, the stir welded portion has the same structure as that obtained when the solution treatment is performed. The hardness is higher than that of the base material and the heat affected zone. Further, the heat-affected zone is a restored structure in which age hardening has slightly occurred, and the strength or hardness thereof is equal to or higher than that of the base material and lower than that of the stir joint. On the other hand, the base material which is an unjoined part (parts other than the joined part including the heat affected zone) remains in the restored structure, and the strength or hardness thereof is the lowest. As a result, even if press molding is performed on the part including the joint part, it is advantageously prevented that stress is locally concentrated on the heat-affected zone and breakage occurs at 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. As a result, the elongation at break or ductility of the bonding material is effectively increased, and the press formability is advantageously improved. It is.

  In addition, in the friction stir welding method for heat-treatable aluminum alloy material 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 depend on the type of heat-treatable aluminum alloy material. Therefore, it is possible to more effectively control the strength balance of the stir welded part, the heat-affected part and the base material, and it is more advantageous to use a joint material excellent in ductility and in turn press formability. Can be obtained.

  Further, according to the sixth aspect of the friction stir welding method for heat-treatable aluminum alloy material according to the present invention, the strength or hardness of the base material can be further ensured, and the strength or the strength of the stir welded portion or the heat affected zone can be increased. It can be made lower than the hardness.

  Furthermore, according to the seventh aspect of the friction stir welding method for heat-treatable aluminum alloy material according to the present invention, heat treatment under desired conditions can be advantageously performed.

  In addition, according to the eighth aspect of the friction stir welding method for heat-treatable aluminum alloy material according to the present invention, for the pair of heat-treatable aluminum alloy materials to be joined, the restoration treatment operation and the friction stir welding operation are: Each of the above-mentioned bonding materials having excellent press formability can be continuously produced from the place where they are successively carried out successively on the same line without being carried out separately at different places. It can be manufactured efficiently. Furthermore, since age hardening due to natural aging until the friction stir welding is performed after the restoration treatment does not occur, the strength or hardness of the base material is set to be higher than the strength or hardness of the stir welding portion or the heat affected zone. Thus, it is possible to lower the temperature more reliably.

  Moreover, in the bonding material for press molding according to the present invention, since it is produced by the friction stir welding method of the heat treatment type aluminum alloy material as described above, during the press molding, the fracture at the heat affected zone is prevented, The amount of deformation is advantageously increased, and as a result, press forming with a free press shape and a larger processing amount becomes possible.

  By the way, in the friction stir welding method for heat-treatable aluminum alloy material according to the present invention as described above, the heat-treatable aluminum alloy material is made of heat-treatable aluminum that can be increased in strength by age hardening heat treatment. Alloys, for example, 6000 series (Al-Mg-Si series), 2000 series (Al-Cu-Mg series), 7000 series (Al-Zn-Mg series) aluminum alloys, etc. are used under the alloy number of JIS designation. Will be. 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, in order to impart bake hardness (coating bake hardenability), if necessary, it is preliminarily kept at a temperature of 40 ° C. to 120 ° C. within 24 hours after quenching. Aging can also be performed.

  Thereafter, the T4 tempered heat-treatable Al alloy material is subjected to a restoration process prior to the friction stir welding. Here, the restoration process is a process for once extinguishing GP zones (or clusters) formed by natural aging in the metal structure of the heat-treated Al alloy material tempered by T4. Is such that the heat treatment type Al alloy material that has undergone the T4 tempering process is heated to a temperature of 150 ° C. to 350 ° C., and the elevated temperature is 300 seconds or less, more preferably 60 seconds or less. During this period, the heat treatment is performed. 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 a 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 where an Al alloy material is used, the temperature is preferably 200 ° C. to 350 ° C., more preferably 200 ° C. to 300 ° C., among the ranges described above. Further, in the case of a 2000 series Al alloy material, it is preferably set to 150 ° C. to 300 ° C., more preferably 180 ° C. to 300 ° C., within the range described above. Further, in the case of a 7000 series Al alloy material, 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 heat treatment type Al alloy material is raised to the target heat treatment temperature as described above, or when the temperature is lowered from the heat treatment temperature, the rate of temperature rise or the rate of temperature drop is not particularly limited, In order to effectively realize the restoration described above, the temperature raising rate and the temperature lowering rate are each preferably set to 2 ° C./second or more, more preferably 4 ° C./second to 50 ° C./second. It is desirable that

  Thus, by performing the predetermined heat treatment as described above, the GP zone (or cluster) formed in the metal structure of the heat-treated Al alloy material tempered by T4 once disappears and becomes a restored structure. . As a result, the strength or hardness of the heat-treated Al alloy material that has been subjected to the restoration process and is in a restored state is lowered as a whole.

  In the present invention, the following friction stir welding is performed in a state where the strength or hardness of the heat treatment type Al alloy is reduced by such restoration processing. However, the heat-treated Al alloy material that has been subjected to the restoration treatment has a strength or thoroughness because a GP zone (or cluster) is formed again in the metal structure by natural aging from a restoration state having a low strength or hardness. Increases in hardness. For this reason, in the joining operation by the friction stir welding method, the strength or hardness of the heat-treatable Al alloy material does not increase excessively due to natural aging. In other words, the GP zone is substantially formed again in the restored state. It is desirable to be implemented by the time it is done. Specifically, the amount of increase in the tensile strength of the heat treatment type Al alloy material, that is, the tensile strength of the heat treatment type Al alloy material after the restoration treatment is determined from the tensile strength of the heat treatment type Al alloy material at the time of friction stir welding. It is desirable that the subtracted value be carried out while not exceeding 10 MPa, more preferably not exceeding 5 MPa. This is because when the amount of increase in tensile strength due to age hardening exceeds 10 MPa, the strength or hardness of the base material becomes higher than the strength or hardness of the heat-affected zone after bonding. This is because it becomes impossible to obtain the strength balance. Here, “tensile strength” can be measured according to “Metal Material Tensile Test Method” of JIS-Z-2241.

  For this reason, for example, when the heat-treated Al alloy material after the restoration process is stored at a temperature of 20 ° C., in the case of the 6000 series Al alloy material, within about 60 days after the restoration process, the 2000 series Al alloy material In that case, it is desirable to perform friction stir welding within about 20 days after the restoration process, and further within about 20 days after the restoration process in the case of a 7000 series Al alloy material. In addition, since age hardening progresses faster as the storage temperature increases, for example, when storing a 6000 series Al alloy material at 40 ° C., friction stir welding within one week or two weeks after restoration processing It is desirable to implement. In short, it is important to perform the friction stir welding before the tensile strength is increased so much, in other words, before the effect of the restoration process is lost.

  By the way, when a heat-treatable Al alloy material in a restored state is friction stir welded to form a target joining material, a technique similar to the conventional technique can be employed. For example, first, as shown in FIG. As described above, two heat-treated Al alloy materials (here, plate materials) that have undergone restoration treatment are butted together, and the two heat-treatable Al alloy materials 10a and 10b are butted together. The alloy materials 10a and 10b are constrained according to a conventional method so as not to 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). Further, a heat affected zone 20 (HAZ portion: site affected by heat) is present in the peripheral area adjacent to the stir weld 18.

  Therefore, normally, as shown in the lower part of FIG. 2, the hardness of the heat affected zone 20 is the lowest, but in the present embodiment, the restoration process is performed prior to the friction stir welding. Therefore, after the friction stir welding, the stir welded portion 18 has a structure similar to that in the case where the solution treatment is performed, and the hardness thereof is as shown in the middle part of FIG. It becomes larger than the influence part 20. More specifically, when the stir weld 18 reaches a temperature of 450 ° C. or higher, the alloy components that form clusters such as Si, Mg, and Cu are dissolved, and the hardening rate by natural aging after joining is It is enhanced more effectively than the heat affected zone 20 and the base material 22 and becomes the hardest. In addition, the heat-affected zone 20 is in a state where a slight age hardening has occurred in the restored tissue without softening even when subjected to heat, although its hardness is small compared to the stirring joint 18, It becomes the same as or more than the hardness of the base material 22. Furthermore, the base material 22 which is not affected by the heat caused by the friction stir welding remains in a restored structure, and its hardness is the smallest. 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.

  On the other hand, when the restoration process is not performed, after the friction stir welding, the stir welded portion 18 has the same structure as that obtained when the solution treatment is performed. As shown in the figure, the heat affected zone 20 has the restored metal structure and becomes the softest while being harder than the base material 22 subjected to T4 tempering or slightly smaller than the base material 22. For this reason, when a 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 to cause breakage.

  According to the study by the present inventors, when the heat treatment type Al alloy material having the restoration structure subjected to the restoration treatment as described above is joined by a fusion welding method such as TIG welding or MIG welding, FIG. A trapezoidal hardness distribution as shown in the middle is not obtained, and it is recognized that the hardness is lowest in the heat affected zone. Furthermore, since the joint part and a part of the heat-affected part adjacent to the joint part are once melted, the cast structure is altered and ductility is lowered.

  As described above, in the friction stir welding method for heat-treatable Al alloy material according to the present invention, the friction stir welding is performed on the heat-treated Al alloy material in a restored state. The strength balance of the joint 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 is advantageously 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 distributed 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.

  Thus, in the bonding material obtained as described above, after excellent press moldability 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.

  By the way, the heating method of the restoration process performed prior to the friction stir welding is not particularly limited, and any heat treatment using a conventionally known heating means may be employed. For example, when adopting an offline manufacturing process in which the restoration process and the friction stir welding process are performed discontinuously, a salt bath, an oil bath, an air furnace, infrared heating or induction heating The heat treatment performed using any one of the heating means is preferably employed from the viewpoint of equipment and cost.

  In the present invention, it is also possible to carry out the restoration process and the friction stir welding continuously on the same line. When such an on-line manufacturing process is adopted, for example, FIG. As shown, along the to-be-joined portions (butting portions 16) to be friction stir welded of the heat-treatable Al alloy materials 10a and 10b, the above-described restoration treatment (heat treatment) is performed in the width direction (joining direction) of the to-be-joined materials. In the direction perpendicular to the base material portion, preferably over the entire width direction, while being sequentially performed, the jointed portion (for which such restoration processing has been completed) Friction stir welding is sequentially performed on the butt 16). 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 not limited to the bonded portion (butting portion 16) and the vicinity thereof, but stress applied during processing is effectively dispersed in the base material portion, and a large amount of deformation can be secured. Needless to say, the heat treatment type Al alloy material needs to be applied to a wide range in the width direction.

  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. If the plate thickness is different, both the heat treatment type Al alloy material on the thin side and the heat treatment type Al alloy material on the thick side are subjected to restoration treatment, or the heat treatment type Al on the thin side. The restoration process may be performed only on the alloy material. In short, after joining, the T4 tempering, restoring treatment, friction, etc., as described above, so that the part where the strength or hardness is the lowest becomes the base material of any of the heat treated Al alloy materials to be joined. Stir welding may be performed sequentially.

  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. Then, the resulting ingot is subjected to homogenization treatment, hot rolling, and cold rolling, respectively, to obtain an aluminum alloy sheet having a thickness of 1.0 mm, and further to solution treatment and quenching. And subjected to natural aging for 10 days at room temperature to obtain a T4 tempered material.

  Next, each T4 tempered material is subjected to heat treatment (restoration treatment) under the conditions shown in Table 2 below, and after storing at 20 ° C. for 3 days, two aluminum alloy materials subjected to such restoration treatment are used. In the state where the end surfaces in the width direction were butted against each other, the butted portions were butt-joined by a friction stir welding method (FSW method) to prepare test materials 1 to 10 as bonding materials. In any aluminum alloy material, it was separately confirmed that the amount of increase in tensile strength from the time when the restoration process was performed until the joining was performed was 10 MPa or less. 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.

  And after joining, the obtained test materials 1 to 10 are stored at 20 ° C. for 7 days, and then, for each of the test materials, a Vickers hardness test, a tensile test, and a moldability test are performed as described later. The results obtained 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, first, 10 types of alloys (A to J) having the same chemical composition as those used in the above examples 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 natural aging for 10 days at room temperature, a T4 tempered material was obtained. And about each T4 tempered material, without performing heat treatment (restoration process), two T4 tempered aluminum alloy materials are used as they are, respectively, in a state where they are butted against each other at the end faces in the width direction. These butt portions were butt-joined by the friction stir welding method (FSW method) under the same conditions as in the above-described example, to prepare test materials 11 to 20 as bonding materials. Then, after friction stir welding, the obtained test materials 11 to 20 were stored at 20 ° C. for 7 days, and each of these test materials was subjected to the Vickers hardness test, the tensile test, and the moldability as described above. The test was conducted, and the obtained results are 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 process, the Vickers hardness of the heat affected zone was the highest among the stir welded portion, the heat affected zone and the base material. The value is low, 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, first, 10 types of alloys (A to J) having the same chemical composition as those used in the above examples 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 natural aging for 10 days at room temperature, a T4 tempered material was obtained. And about each T4 tempered material, after heat-treating on the conditions shown in Table 4 below and storing for 3 days at 20 ° C., two aluminum alloy materials subjected to such heat treatment were used in each of the width direction. In a state in which the end surfaces are butted against each other, the butted portions are butt-joined by the friction stir welding method (FSW method) under the same conditions as in the above-described example, and test materials 21 to 50 as bonding materials are produced. . Thus, after friction stir welding, the obtained test materials 21 to 50 were stored at 20 ° C. for 7 days, and each of these test materials was subjected to the Vickers hardness test, the tensile test, and the moldability as described above. The test was conducted, and the obtained results are shown in Table 4 below.

  As is clear from the results in Table 4, the test materials 21, 24, 27, 30, 33, 36, 39, 42, 45, and 48 all have a low heat treatment temperature. Thus, the Vickers hardness of the base material is higher than that of the heat-affected zone, fracture occurs in the heat-affected zone, and the elongation at break and the limit forming height are low. In addition, since all of the test materials 22, 25, 28, 31, 34, 37, 40, 43, 46, and 49 had a high heat treatment temperature, softening due to overaging occurred, and a desired restored structure could not 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. 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, first, 10 types of alloys (A to J) having the same chemical composition as those used in the above examples 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 natural aging for 10 days at room temperature, a T4 tempered material was obtained. And about each T4 tempered material, after performing heat treatment (restoration treatment) under the conditions shown in Table 5 below and storing at 40 ° C. for 30 days, two heat-treated aluminum alloy materials were used, respectively. In a state where the end faces in the width direction are butted against each other, the butted portions are butt-joined by the friction stir welding method (FSW method) under the same conditions as in the above-described example, and the test materials 51 to 51 which are the joining materials 60 was produced. In any aluminum alloy material, the amount of increase in tensile strength after performing the restoration process until the joining was performed exceeded 10 MPa. Thus, after friction stir welding, the obtained test materials 51 to 60 were stored at 20 ° C. for 7 days, and each of these test materials was subjected to the Vickers hardness test, tensile test, and moldability as described above. The test was conducted, and the obtained results are shown in Table 5 below.

  As is clear from the results of Table 5, in all of the test materials 51 to 60, the friction stir welding was performed in the state where age hardening occurred from the restored state. Among the base materials, the Vickers hardness of the heat affected zone 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.

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 Cross-sectional explanatory drawing of the Al alloy material, a graph showing the hardness distribution of the joint material subjected to the friction stir welding after the restoration process, and the friction stir welding performed without the restoration process according to the present invention The graph showing the hardness distribution of the conventional bonding material 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 restoration process operation and a friction stir welding 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 method of friction stir welding a base metal made of heat-treatable aluminum alloy material, was subjected to a T4 heat treated in the heat treatment type aluminum alloy material for heat-treatable aluminum alloy material in which the T4 tempering, 0.99 ° C. A heat treatment type aluminum alloy material that has been heated to a temperature of ˜350 ° C., subjected to a heat treatment that is held for 300 seconds or less at that temperature, and that has been subjected to the heat treatment, in a restored state The friction stir welding is performed so that the hardness of the generated stir welded portion is larger than the hardness of the base material, and the hardness increases from the base material toward the stir welded portion. Friction stir welding method for heat treatment type aluminum alloy material. The method for friction stir welding of a heat-treatable aluminum alloy material according to claim 1, wherein a temperature increase rate and a temperature decrease rate in the restoration process are each 2 ° C / second or more .   The heat treatment type aluminum alloy material is a 6000 series aluminum alloy material, and the restoration treatment is performed by heating the T4 tempered heat treatment type aluminum alloy material to a temperature of 200 ° C. to 350 ° C. for 300 seconds. The heat-treating aluminum alloy material friction stir welding method according to claim 1, wherein the heat-treating heat treatment is maintained for the following time.   The heat-treatable aluminum alloy material is a 2000 series aluminum alloy material, and the restoration treatment raises the temperature of the heat-treatable aluminum alloy material tempered by T4 to a temperature of 150 ° C. to 300 ° C. and takes 300 seconds at the temperature. The heat-treating aluminum alloy material friction stir welding method according to claim 1, wherein the heat-treating heat treatment is maintained for the following time.   The heat treatment type aluminum alloy material is a 7000 series aluminum alloy material, and the restoration treatment is performed by heating the T4 tempered heat treatment type aluminum alloy material to a temperature of 150 ° C. to 250 ° C. for 300 seconds. The heat-treating aluminum alloy material friction stir welding method according to claim 1, wherein the heat-treating heat treatment is maintained for the following time.   2. The friction stir welding of the heat-treatable aluminum alloy material subjected to the restoration treatment after the restoration treatment while the increase in tensile strength due to natural aging does not exceed 10 MPa. The friction stir welding method for heat-treatable aluminum alloy material according to any one of claims 5 to 6.   The heat-treatable aluminum alloy material according to any one of claims 1 to 6, wherein the restoration treatment is performed by a heat treatment using a salt bath, an oil bath, an air furnace, infrared heating or induction heating. Friction stir welding method.   While the restoration process is sequentially performed using a predetermined heating means along the joined part to be friction stir welded of the heat-treatable aluminum alloy material, the restored part is subjected to the restoration process. The friction stir welding method for heat-treatable aluminum alloy material according to any one of claims 1 to 7, wherein the friction stir welding is sequentially performed.

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