JP3291252B2 - Aluminum alloy joining method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for joining aluminum alloys, and more particularly, to a method for joining aluminum using friction stir welding.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of protecting the global environment and conserving energy, it has been desired to reduce nitrogen oxides and carbon dioxide emitted from automobiles and to improve fuel efficiency. One of the most effective ways to achieve this is to reduce vehicle weight,
That is, use of a lightweight material is conceivable. Therefore, conversion of a material constituting an automobile body and parts from steel to an aluminum alloy is being studied. Aluminum alloys are not only lightweight, but also can increase rigidity by optimizing the cross-sectional shape, and are suitable as components of transportation equipment.

[0003] However, aluminum alloys are often provided as extruded materials rather than as rolled plates such as steel. Since the extruded material is extruded through a die, the width of the profile is limited. Therefore, when forming a wide profile or a large structure using an aluminum alloy,
The extruded materials are generally joined by arc welding (MIG or TIG).

[0004]

However, when arc welding is performed, the welded portion is deformed, and a smooth surface shape is hindered. For this reason, it is necessary to remove the extra bank formed at the time of welding in a portion where the appearance is important. In addition, when the arc welding is performed, the welding heat affected zone (HAZ) outside the welded portion becomes 500
Since it is slowly heated to a temperature close to ° C., a large precipitate is formed and the strength is reduced. For this reason, it is necessary to previously form a thick portion in the welded portion to compensate for the strength, and the effect of weight reduction cannot be sufficiently exhibited. Further, in arc welding, defects such as specific blowholes and solidification cracks may occur. In this case, the welding portion is removed and re-welding is performed. In this case, a large number of man-hours are required and the appearance of the welded portion becomes dirty.

In recent years, friction stir welding has been considered as a joining method with low heat input and a low degree of softening or distortion (for example, Japanese Patent No. 2712838). In this method, a soft material such as an aluminum alloy is butted and restrained on a hard backing such as steel, and a hard pin-type tool is moved along the butted portion while rotating at a high speed. This method is characterized in that the joint does not melt, and the temperature of the heat-affected zone outside the stirring unit does not rise so much. However, the temperature of the heat-affected zone may considerably increase due to the friction stir welding. In this case, the joint strength of the joining member cannot be sufficiently ensured due to the influence of the precipitation and the like.

Accordingly, the present invention has been made in a method for joining aluminum alloys using friction stir welding, with the object of ensuring sufficient joint strength of joining members.

[0007]

[Effect of the means and Invention The present invention of claim 1, wherein has been made in order to achieve the above object, 600
A joining step of performing friction stir welding of a T1 material of a 0 series, 2000 series, or 7000 series aluminum alloy with the heat-affected zone outside the stirring unit heated to 300 ° C. or more within 1 minute; 3 to the joining member joined by
An aging treatment at a temperature lower than 00 ° C. to secure a joint strength of 95% or more with respect to the proof stress of the base material;
Are successively performed, and a method of joining aluminum alloys is characterized.

[0008] In the present invention, 6000 series, 2000 series, or
Or T1 material of 7000 series aluminum alloy is friction stir welded. Almost no precipitates appear in such an aluminum alloy, and there is only a GP zone. Also, the T1 material is relatively soft and has low stirring resistance,
If the shape and the like of the tool are appropriately set, the time during which the heat-affected zone outside the stirring unit is heated to 300 ° C. or more can be easily set within 1 minute. When the friction stir welding is performed at such a low temperature in a short time, the precipitation does not proceed in the heat-affected zone due to the welding, but the restoration only occurs and the GP zone disappears. In the stirring section, the precipitate is finely broken by stirring. For this reason, so-called work hardening occurs even when the temperature is higher than the heat-affected zone, so that a higher strength can be obtained by the next aging treatment step.

If the aluminum alloy joined by such a joining step is subjected to an aging treatment at a temperature lower than 300 ° C., the same strength specifications as those of the T5 or T6 material are satisfied,
And the joining member which has 95% or more joint strength with respect to the proof stress of a base material is obtained. Furthermore, in the present invention, since the aluminum alloy is joined by using friction stir welding, it is possible to protect the appearance and eliminate the need for post-processing or the like for the welded portion.

Therefore, according to the present invention, the required man-hours can be reduced while protecting the appearance, and the joint strength of the joining member can be sufficiently ensured. In the joining step, the heat affected zone is desirably maintained at 250 ° C. or lower. According to a second aspect of the present invention, in the method for joining aluminum alloys of the first aspect, the T1 material is formed by cooling an extruded material of a 6000 series aluminum alloy at a cooling rate of 10 ° C./min or less at the time of extruding the material. In the aging treatment step,
Aging treatment at 150-250 ° C for 10 minutes to 12 hours
Then, the joint joined through the joining step and the aging treatment step
The joint member is a space frame for cars and undercarriage for cars
It is characterized in that it is a part or a vehicle profile .

In the present invention, since the extruded material of the 6000 series aluminum alloy is cooled at a cooling rate of 10 ° C./min or less at the time of extruding, the T1 material suitable for friction stir welding can be reliably obtained. Moreover, in the subsequent aging step, aging is performed at 150 to 250 ° C. for 10 minutes to 12 hours. For this reason, very good age hardening occurs at the joint, and the joint member has a 9% resistance to the proof stress of the base material.
An extremely good joint strength of 5% or more can be secured.

Accordingly, in the present invention, in addition to the effect of the first aspect, effects arising such a joint strength of the joint member can be better ensured.

[0013]

[0014]

[0015]

[0016]

Further , if the 6000 series aluminum alloy is joined by the method for joining aluminum alloys of the present invention ,
As described above, a joining member having extremely good joint strength is obtained. In this case, there is no need to form a thick joint to compensate for the strength. The present invention is characterized in that the joining member joined in this way is an automobile space frame, an automobile underbody part, or a vehicle profile. Although these members are still formed thick to secure the required strength, in the present invention, it is not necessary to form these members thick, and a very remarkable effect is achieved in reducing the weight of an automobile. . Therefore, the fuel efficiency of the vehicle can be improved satisfactorily.

[0018] Thus, in the present invention, in addition to the effect of the first aspect, to improve the fuel efficiency of automobiles, also resulting effect that can promote protection and energy saving of the global environment.
According to a third aspect of the present invention, in the method for joining aluminum alloys according to the first or second aspect , the joint is locally heated and tempered.

In the present invention, since the joint (the stirring section and the heat-affected zone) is locally heated and tempered, the strength of the joint can be further improved. Therefore, in the present invention, in addition to the effects of the invention described in claim 1 or 2 , the strength of the joint is more preferably ensured, and
This produces an effect that the joint strength of the joining member can be more favorably secured.

The invention according to claim 4 is characterized in that the 6000 series, 20
Two or more T1 materials or T4 materials of aluminum alloys of the 00 series or the 7000 series are joined by friction stir welding in which the heat-affected zone outside the stirrer is heated to 300 ° C. or more within 1 minute in the width direction. A first joining step of joining to produce a wide profile, and aging treatment at a temperature lower than 300 ° C. on the wide profile joined by the first joining process, so that the proof strength of the base material is 95% or more. A method for joining aluminum alloys, comprising sequentially performing an aging treatment step for securing joint strength, and a second joining step for joining the wide sections to produce a structure, wherein an end of the wide sections is formed. It is formed thick in advance,
In the second joining step, the ends are joined by inert gas arc welding, and the thickness of the wide section including the heat-affected zone of the inert gas arc welding is set to 1.25 to 1.25 of the thickness of the base material.
The gist of the present invention is a method of joining aluminum alloys, characterized in that the number is doubled.

According to the present invention, the T1 of the 6000 series, 2000 series, or 7000 series aluminum alloy is obtained by the first joining step and the aging treatment step similar to the joining step and the aging treatment step described in claim 1. Two or more T4 materials are joined in the width direction. For this reason, in the wide profile material manufactured through the first joining step and the aging treatment step of the present invention, claim 1
Similarly to the described invention, the joint strength can be sufficiently ensured.

In the present invention, the wide section is joined by inert gas arc welding in the subsequent second joining step. For this reason, it is possible to easily join even a portion where friction stir welding is difficult. In addition, the thickness of the wide section including the heat-affected zone of the inert gas arc welding is set to 1.2 times the thickness of the base material.
Since it is 5 to 2 times, the strength of the joint can be sufficiently ensured. Therefore, in the present invention, a large structure or a structure having a complicated shape can be easily manufactured,
In addition, there is an effect that the strength of the joint portion of the aluminum alloy constituting the structure can be sufficiently ensured.

[0023]

Next, an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, as schematically shown in FIG. 1, aluminum alloys 10 and 20 are butted and restrained on a hard backing (not shown) made of steel or the like, and hard alloy is formed along the butted portion. The pin type tool 28 was moved while rotating at a high speed.

FIG. 2 is a side view showing the configuration of the pin type tool 28. As shown in FIG. As shown in FIG. 2, the pin-type tool 28 includes a large-diameter shoulder 28a and a small-diameter column 28b protruding from a lower end of the shoulder 28a, and a driving force is transmitted from a driving system (not shown). As a result, the column rotates around the central axis of the column 28b and moves along the butted portions of the aluminum alloys 10 and 20. Then, as shown in FIG. 1, a stirrer 30 is formed at the butted portion where the metal forming the aluminum alloy 10 and the metal forming the aluminum alloy 20 are stirred and joined by the columns 28 b. In addition, the aluminum alloy 1 outside the stirring unit 30
Heat affected zones 10a and 20a affected by the heat generated by the stirring are formed at 0 and 20, respectively.

Thus, the aluminum alloy 10,
In the joining member 50 obtained by joining the two, the stirring unit 30
The strength of the entire joint 40 including the heat affected zones 10a and 20a is a major factor that determines the joint strength of the joint member 50. Therefore, the applicant of the present application has diligently studied to improve the joint strength. As a result, the friction stir welding is performed in a state where the aluminum alloys 10 and 20 are in the T1 material (joining step), and the heat affected zones 10a and 20a are joined during the joining.
By performing the aging treatment at a temperature lower than 300 ° C. after the joining while setting the heating time of the joint member to 300 ° C. or more within 1 minute (aging treatment step), the joint strength of the joining member 50 can be significantly improved. discovered.

[0026]

EXAMPLES Specific experimental results will be described below with reference to examples. Note that the T1 materials of various aluminum alloys described below are obtained by extruding an extruded material formed by extrusion and then cooling it at an air rate at a rate of 10 ° C./min or less.

Embodiment 1: As shown in FIG. 3, bus bars 13, 23 made of T1 material of aluminum alloy 6N01.
(Thickness 4 mm x width 150 mm x length 5000 mm) were arranged side by side in the width direction and restrained. The diameter D of the shoulder 28a is 15 mm,
The pin-shaped tool 28 having a diameter d of 4 mm and a length H of the column 28b of 3.8 mm is rotated at 2000 rpm and at a moving speed of 80 mm.
The friction stir welding was performed by driving at 0 mm / min. Stirrer 33
Thermocouples are embedded in the heat affected zones 13a and 23a outside the
When the heat generated during bonding was measured, it was 250 ° C. × 10 seconds. After joining, aging treatment was performed at 175 ° C. × 8 hours to obtain a joining member 53. After the joining and after the aging treatment, almost no distortion occurred in the joining member 53. As a result of measuring the joint tensile strength (corresponding to the joint strength) of the joining member 53, the joint tensile strength after the aging treatment was 270 MPa, and the tensile strength of the T5 material aged with the same base material as before the joining was 260 M
Pa was exceeded.

Example 2: As shown in FIG. 4, an extruded material 15, 25 (thickness 3 mm × width 350 mm × length 5000 m) made of T1 aluminum alloy 2014 and having a ring at an end portion.
m) were aligned in the width direction and constrained. A pin-type tool 28 having a shoulder D having a diameter D of 15 mm, a column d having a diameter d of 5 mm and a column H having a length H of 6 mm is driven at a rotational speed of 3000 rpm and a moving speed of 150 mm / min to perform friction stir welding. went.
When thermocouples were embedded in the heat-affected sections 15a and 25a outside the stirring section 35 and the heat generated at the time of joining was measured, the temperature was 250 ° C. ×
250 seconds. After joining, aging treatment was performed at 180 ° C. for 2 hours to obtain a joining member 55. After the joining and after the aging treatment, almost no distortion occurred in the joining member 55. As a result of measuring the joint tensile strength of the joining member 55,
The joint tensile strength after aging treatment is 390 MPa, and the tensile strength of T6 material aged with the same base metal as before joining is 380 MPa.
Exceeded.

Example 3 T of aluminum alloy 7075
One extruded profile (2.5 mm thick x 30 mm wide x 25 mm high x 2,000 mm long) was constrained in the width direction.
The diameter D of the shoulder 28a is 12 mm, and the diameter d of the pillar 28b is 3 m.
m, the pin-shaped tool 28 with the length H of the column 28b being 3 mm,
The friction stir welding was performed by driving at a rotation speed of 2000 rpm and a moving speed of 50 mm / min. A thermocouple was embedded in the heat-affected zone outside the stirrer, and the heat generated during joining was measured.
X 45 seconds. After joining, aging treatment was performed at 150 ° C. for 2 hours to obtain a joined member. After the joining and after the aging treatment, almost no distortion occurred in the joined member. As a result of measuring the joint tensile strength of this joined member, the joint tensile strength after aging treatment was 450 MPa, which exceeded the tensile strength of 430 MPa of the T6 material aged with the same base metal as before joining.

In the same manner, an extruded material made of T1 material of another aluminum alloy (6063, 6061, 219, or 7N01) was similarly subjected to friction stir welding and subjected to aging treatment (Examples 4 to 7: described later). See Table 1). At this time, by appropriately adjusting the size, the number of revolutions, the moving speed, etc. of the pin type tool 28, the heat generated at the time of joining is reduced to 250 ° C. × 10 seconds, 25 ° C.
0 ° C x 25 seconds, 250 ° C x 20 seconds, or 250 ° C x 5
0 seconds. The aging treatment is performed at 175 ° C. for 8 hours, 1 hour.
75 ° C x 8 hours, 180 ° C x 2 hours, or 150 ° C x
Performed in 2 hours. And the joint tensile strength of these Examples was compared with Comparative Examples 1 to 5 in which joining by MIG welding was performed. Here, for example, in Comparative Example 1, the extruded materials were joined as follows.

Comparative Example 1: T of aluminum alloy 6N01
Busbar made of one material (4mm thick x 150mm wide x 5mm long
000 mm) were arranged in the width direction and restrained. After performing MIG welding using aluminum alloy 5356 as a filler, 17
The aging treatment was performed at 5 ° C for 8 hours. In this case, about 4 mm of angular deformation occurred in the width direction after joining. As a result of measuring the joint tensile strength of this joined member, the joint tensile strength after aging treatment was 180 MPa, and T5 was aged with the same base metal as before joining.
The tensile strength of the material was significantly lower than 260 MPa.

Other aluminum alloys (2014, 707)
5,6063,2219) was also subjected to the same MIG welding and compared with the above embodiment. Table 1 shows the results.

[0033]

[Table 1]

As shown in Table 1, in each of the above Examples, sufficient joint tensile strength was obtained, whereas in each of the above Comparative Examples, the joint tensile strength was significantly reduced. This is considered to be due to the following reasons. That is, in Comparative Examples 1 to 5, the heat generated at the time of joining was 350
° C, and the time during which the heat-affected zone is heated to 300 ° C or more is considered to be more than 1 minute. Therefore, it is considered that a large precipitate was formed in the aluminum alloy and the strength was reduced.

On the other hand, in each of the above embodiments, friction stir welding was performed with the time during which the heat-affected zone was heated to 300 ° C. or higher within one minute, and the joined members were joined together by three times.
Since the aging treatment is performed at a temperature lower than 00 ° C., the joint strength of the joining member can be sufficiently ensured. this is,
It is considered as follows.

That is, in each of the above embodiments, the aluminum alloy T1 material is friction stir welded. Almost no precipitates appear in such an aluminum alloy, and there is only a GP zone. In addition, since the T1 material is relatively soft and has low resistance to stirring, if the shape of the tool is appropriately set as described above, the time during which the heat-affected zone is heated to 300 ° C. or more can be set within 1 minute. Easy. When friction stir welding is performed at such a low temperature and in a short time, precipitation in the heat-affected zone does not progress due to the welding,
Restoration only occurs and the GP zone disappears. Also,
In the stirring section, the precipitate is finely broken by stirring. For this reason, so-called work hardening occurs even when the temperature is higher than the heat-affected zone, so that a higher strength can be obtained by the next aging treatment step.

In each of the above embodiments, the aluminum alloy is joined by such a joining step and an aging treatment step, so that the joint strength of the joining member can be secured extremely well. Further, in each of the above embodiments, since the aluminum alloy is joined by using friction stir welding, it is possible to protect the appearance and to eliminate the need for post-processing on the welded portion. Therefore, man-hours can be reduced and manufacturing costs can be reduced.

Further, as in Examples 1, 4, and 5,
When a 6000 series aluminum alloy is joined by the above method, a joining member having extremely good joint strength is obtained as described above. In addition, in this case, it is not necessary to form a thick joint to compensate for the strength. For this reason, when the joining member joined in this way is used for an automobile space frame, an automobile underbody part, or a vehicle profile, the following effects are further produced. In other words, these members are still formed thick to ensure the necessary strength,
It is not necessary to form these members thick, and the weight reduction of the automobile can be promoted very well. For this reason, the fuel efficiency of the vehicle can be improved satisfactorily, and furthermore, protection of the global environment and energy saving can be promoted.

In the method of joining aluminum alloys in each of the above embodiments, the joint may be locally heated and tempered. In this case, the strength of the joint can be more preferably secured, and furthermore, the joint strength of the joint member can be more favorably secured. For example, aluminum alloy 6N0
Using the T1 material as a base material, butting and welding were performed at 250 ° C. for 30 seconds and friction stir welding was performed under conditions that allowed welding (2 minutes).
A heater was applied to the bead within a range of 40 mm in width around the joint line, and heated at 220 ° C. for 30 minutes. Then, when the hardness of the cross section was measured, the hardness of the joint was 95% or more of the base material no matter where it was measured, and the joint and the heat-affected zone were age-hardened sufficiently and were equivalent to the base material. It was confirmed that the material had mechanical properties.

Furthermore, after joining two or more aluminum alloy T1 materials (which may be T4 materials) in the width direction through the same steps as in the above embodiment, a predetermined aging treatment is applied to wide-width shaped materials. May be manufactured, and the structure may be manufactured by joining the wide sections with inert gas arc welding. In this case, the end of the wide section to be joined by the inert gas arc welding is previously formed thick, and the thickness of the wide section including the heat affected zone of the inert gas arc welding is determined by the thickness of the base material. It is good to make it 1.25 to 2 times. This makes it possible to easily join the portions where the friction stir welding is difficult by the inert gas arc welding, and also to sufficiently secure the strength of the joined portions. Therefore, in this case,
A large structure or a structure having a complicated shape can be easily manufactured, and the strength of the joint portion of the aluminum alloy constituting the structure can be sufficiently ensured.

For example, a vehicle floor or the like may be moved in the vehicle cross-sectional direction by 2 mm.
The divided members are produced by friction stir welding of T1 material of aluminum alloy 6N01 and subsequent aging treatment, and the joints of the center and side panels are joined by MIG welding. M
Only the IG welded part is thicker than the base material (base material 2.5 mmt, M
If the IG part is 4 mmt), the overall strength is secured. The friction stir welding part can be made thinner, and the effect of weight reduction is great, as compared with the conventional method in which all are performed by MIG.

It should be noted that the present invention is not limited to the above-described embodiment at all, and can be implemented in various forms without departing from the gist of the present invention. For example, as a tool for performing friction stir welding, as shown in FIG. 5, a large-diameter shoulder 68a and a column 68b protruding from the lower end of the shoulder 68a are provided, and the lower end of the column 68b is further provided. A so-called bobbin-type tool 68 having a large diameter portion 68c may be used. Further, as the type of the aluminum alloy and the shape of the extruded material, various forms other than the above can be considered.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a form of friction stir welding to which the present invention is applied.

FIG. 2 is a side view showing a pin-type tool used for the friction stir welding.

FIG. 3 is an explanatory view schematically showing a joining member obtained in Example 1.

FIG. 4 is an explanatory view schematically showing a joining member obtained in Example 2.

FIG. 5 is a side view showing another embodiment of a tool used for friction stir welding.

[Explanation of symbols]

10, 20 ... aluminum alloy 10a, 13a, 15a, 20a, 23a, 25a ... heat affected zone 13, 23 ... bus bar 15, 25 ... extruded material
28: Pin type tool 30, 33, 35 ... Stirrer 50, 53, 5
5. Joining members

Continuation of the front page (72) Inventor Hideo Yoshi ▼ 5-11-3 Shimbashi, Minato-ku, Tokyo Sumitomo Light Metal Industries Co., Ltd. (56) References JP-A 10-35235 (JP, A) JP Hei 10-52771 (JP, A) JP 9-309164 (JP, A) Ake Andersson, Anders Norlin, "Fiction on Stir Welding of Aluminum Exchange Promotion, Potential Promotional Accounts: Potential Promotional Accounts logs & Processes, IBEC (International Body Engineering Conference &), September 30, 1997, p. 105-110, IBEC '97 Ole T. Midling, "FR ICCTION STIR WELDING-A VALUBLE PRO CESSING ROUTE", Proceedings of the Aluminum 97 Conference, International Exchange Day, September 9, 1997, International Exchange Day, 1997. 1-6 (58) Field surveyed (Int. Cl. ⁷ , DB name) B23K 20/12

Claims (4)

(57) [Claims] 1. A 6000 series, 2000 series, or 700 series
A joining process of performing friction stir welding by setting the time of heating the heat-affected zone outside the stirring unit to 300 ° C. or higher within 1 minute, and joining the T1 material of the 0 series aluminum alloy to the joining member joined by the joining process Aging treatment at a temperature lower than 300 ° C, 95% of the proof stress of the base material
And an aging treatment step for securing the joint strength as described above. 2. The T1 material is obtained by cooling an extruded material of a 6000 series aluminum alloy at a cooling rate of 10 ° C./min or less at the time of extruding, and in the aging treatment step, at 150 to 250 ° C. for 10 minutes to 1
And facilities aging for 2 hours, junctions joined through the joining step and the aging step
Material is automotive space frame, automotive underbody
2. The article according to claim 1, wherein the article is a shaped article for a vehicle.
The method for joining aluminum alloys according to the above. The joining method of 3. A process according to claim 1 or 2, wherein the aluminum alloy, the joint locally heated, baked joining method of an aluminum alloy, characterized in that the back. 4. A 6000 series, 2000 series, or 700 series
Two or more T1 materials or T4 materials of the 0 series aluminum alloy are joined in a width direction by friction stir welding in which the heat-affected zone outside the stirring unit is heated to 300 ° C. or more within 1 minute. A first joining step of manufacturing a shape member; and 300 ° C. on the wide shape member joined by the first joining step.
Aging treatment at lower temperature, 95% against base material proof stress
%, And a second joining step of joining the wide sections to produce a structure by sequentially performing the following steps: a. The end is formed thick in advance, and the second
In the joining step, the ends are joined by inert gas arc welding, and the thickness of the wide section including the heat affected zone of the inert gas arc welding is set to 1.25 to 2 times the thickness of the base material. A method for joining aluminum alloys, comprising: