JPH10314947A - Frame structure, welding frame and its welding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding frame, which is capable of improving welding workability and obtaining superior penetration in corners, as well as its welding method and a frame structure thereby. SOLUTION: Square tubular formed materials 1, 2 having a thickness of 2 to 4 mm are extruded. The formed materials 1, 2 are formed with chamfering on the outer and inner face of the corner part 3. The thickness of the corner part 3 is the same 2-4 mm as that of the side wall part 4, the thickness of the entire formed material being uniform. In addition, the chamfering on the inner face of the corner part 3 is so provided that its radius is in excess of its thickness. Further, the formed materials 1, 2 are each formed with an end face perpendicular in the longitudinal direction at least on one end. Then, with such end faces abutted on each other in the manner that their corner parts are matched, the formed materials 1, 2 are welded together by turning a welding torch around the abutted face 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a frame structure for forming a body frame of an automobile such as a truck by welding a rectangular tube-shaped member made of aluminum or an aluminum alloy (hereinafter, collectively referred to as aluminum). , A welding joint frame used for the same, and a welding method for manufacturing the frame structure.

[0002]

2. Description of the Related Art Conventionally, in a car body such as a truck and a car body such as a transport machine, formed steel sheet ends are overlapped, and the portions are joined by resistance spot welding. The monocoque structure assembled in this manner is a general vehicle body structure such as a truck.

[0003] However, this method has the advantage of being easy to assemble easily, but has many overlapping parts, has a lot of useless parts in structure formation, is not slim, and has a complicated shape of a molded member. However, there is a disadvantage that the weight increases.

[0004] On the other hand, if the vehicle body is assembled by butt-welding the frames by arc welding or beam welding, etc., the structure becomes slim, but the butt accuracy of the frame before welding greatly affects the welding quality. I do. For example, if a gap is generated between frames, welding quality is significantly reduced. For this reason, a jig for restraining the frame and holding it in an assembled state is required, and the frame itself requires high-precision machining. Therefore, it is difficult to automate the assembly.

Recently, attempts have been made to manufacture a vehicle body from aluminum in order to reduce the weight of the vehicle body. In this case, aluminum has low spot weldability, and in a monocoque structure, it is necessary to perform welding at thousands of points. In this case, however, there is a problem in that the electrode is greatly consumed. Also, there is a disadvantage that the formability of the plate material is worse than aluminum than steel.

Therefore, a space frame structure has been proposed in which a hollow pipe-shaped frame is applied to a car such as a truck and a vehicle such as a transport machine. FIG. 8 is a schematic diagram showing a space frame structure proposed as used for a general truck. As shown in FIG. 8, the rectangular cylindrical aluminum members 51 are assembled in the shape of a truck cabin, and the rectangular cylindrical members 51 are joined to each other by welding to fix the rectangular members 51 together. As a result, a so-called space frame structure is formed, and a structural plate is attached so as to cover the space frame 50, thereby completing the automobile body.

[0007] As a method of joining the frames by extrusion molding made of aluminum for manufacturing this space frame, an arc welding method, an arc welding method, and the like required in consideration of the characteristics of the joining method and the characteristics required for the joint portion. A resistance spot welding method or a mechanical joining method has been implemented. Especially,
Arc welding methods proven in the field of transport equipment and the like, for example, AC / TIG (hereinafter, TIG)
) Method or the DCEP-MIG (hereinafter, referred to as MIG) method.

[0008] When performing arc welding on aluminum, it is necessary to rapidly apply a larger amount of heat than when welding steel or the like due to the high thermal conductivity of aluminum.
Further, there is a disadvantage that welding defects such as blowholes, poor penetration, and welding cracks are likely to occur at the welding start and end portions. For this reason, welding of aluminum is difficult.

As the frame made of aluminum, a rectangular cylindrical member whose corner is mainly a right angle and whose cross section is a mouth or a rice pad, or a rectangular cylindrical member whose corner is extremely chamfered is used. Have been. As the dimensions of the rectangular tubular material, a material having a thickness of about 3 mm and a length of one side of about 50 mm is used.

FIG. 5 is a perspective view showing the butting of the openings of the conventional frame. FIG. 6A is a cross-sectional view of a butt surface of FIG. 5 illustrating an example of a conventional method of welding a butt portion, and FIG. 6B is a diagram illustrating another example of a conventional method of welding a butt portion. It is sectional drawing of the butting surface of No. 5. As an example of a conventional welding joining method, first, as shown in FIG.
The arc starts at one corner 65 of the side 61 or in the vicinity thereof, and is welded to the other corner 66 of the side 61 or in the vicinity thereof by a back step method or the like in the circumferential direction indicated by the arrow 101, and subjected to crater processing or the like. End the welding. And
The sides 62 to 64 are welded along the arrows 102 to 104 in the same manner. Next, an arc is started on the weld bead formed on the side 64 near the corner 65, the welding current is reduced from the viewpoint of welding work, and the corner 65 is turned along the arrow 105 and welded. Then, the welding is completed on the welding bead formed on the side 61. Further, by similarly welding the corners 66 to 68 along the arrows 106 to 108, the sections 81 and 82 are welded.

FIG. 6 shows another welding method.
As shown in (b), first, an arc is started at or near one corner 65 of the side 61, the side 61 is welded along the arrow 111, and the welding current is reduced at the corner 66 to reduce the corner 66. Turning welding is performed, and the welding is completed at the side 62 near the corner 66. Next, an arc is started at or near one corner 68 of the side 63, the side 63 is welded along the arrow 112, the welding current is reduced at the corner 67, and the corner 67 is turned and welded. The welding ends at the nearby side 62. Then, welding is started on the weld bead formed on the side 62 near the corner 66, and the welding is performed along the arrow 113 up to the weld bead formed near the corner 67. Further, welding is started with a low current on the welding bead formed on the side 63 near the corner 68, and after turning welding of the corner 68 is completed, the main welding current is applied along the side 114 along the arrow 114 after the completion of turning welding.
Weld up to near the center. And the corner 65 is also the corner 6
By turning and welding under the same conditions as in 8, and by welding to the weld bead formed on the side 64 along the arrow 115,
The sections 81 and 82 are welded.

In order to reduce the number of welding start and end portions at which welding defects are likely to occur, the latter welding method is preferable.

[0013]

However, although the thickness of the corner is thicker than that of the side, the corner is welded at a reduced welding current from the viewpoint of welding work.
FIG. 7 is a sectional view showing the DD plane of FIGS. 6 (a) and 6 (b). As described above, since the welding is performed with the welding current reduced, the overlap 71 occurs in any of the above-described prior arts, and a weld bead having extremely small penetration is formed. Such welding defects, along with welding cracks among the welding defects, particularly cause a reduction in the joint strength of the strength member, and thus need to be avoided.

Further, in MIG welding, the welding speed is extremely high, about 4 to 6 times that of TIG welding, and the welding current is equivalent to the wire feed speed. , The small movement is restricted, and it is difficult to cope with a rapid change in the welding direction. Further, the amount of penetration is smaller than that of TIG welding. For this reason, MIG welding is not suitable for turning welding at corners.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and a welded joint frame capable of improving welding workability and obtaining good penetration at a corner, a method of welding the same, and a welding method therefor. It is an object of the present invention to provide a frame structure constituted by:

[0016]

A frame structure according to the present invention is a rectangular cylindrical frame made of aluminum or an aluminum alloy, has a thickness of 2 to 4 mm, and has at least one end portion in the longitudinal direction. In a frame structure formed by welding and joining a frame having an end surface perpendicular to the outer surface and the inner surface of each corner of the frame, a chamfer is provided, and the thickness of each corner is the thickness of the side wall. And the radius of the chamfer of the inner surface of each corner exceeds the wall thickness. The radius of the chamfer is desirably 10 mm or less.

In the frame structure according to the present invention,
Since the frame structure is configured using a welded joint frame with an appropriate chamfer at the corner, it is possible to weld and assemble with a constant welding current, and to determine the welding direction at the corner. Since the change can be mitigated, the workability of welding is improved.

According to the method for welding a welding joint frame according to the present invention, a rectangular tube made of aluminum or an aluminum alloy has a thickness of 2 to 4 mm, and at least one end has an end surface perpendicular to the longitudinal direction. A frame, at least one of which is provided with a chamfer on an outer surface and an inner surface of each corner thereof, a thickness of the corner is equal to a thickness of a side wall portion, and a radius of the chamfer of an inner surface of the corner is provided. Is characterized in that the butt ends are butt-joined and the butt ends are welded without stopping welding at the corners.

Another method of welding a welding joint frame according to the present invention is to provide a method for welding aluminum or aluminum alloy on a side wall of a first welding joint frame having a rectangular cylindrical shape made of aluminum or aluminum alloy and having a thickness of 2 to 4 mm. A rectangular cylindrical shape having a thickness of 2 to 4 mm, at least one end of which has an end surface perpendicular to a longitudinal direction thereof, an outer surface and an inner surface of each corner are provided with chamfers, The end face of the second welded joint frame, the thickness of which is equal to the thickness of the side wall part and the radius of the chamfer of the inner surface of the corner exceeds the wall thickness, An end face and the side wall of the first welded joint frame are welded at the corner without stopping welding to form a T-shaped joint.

Still another method of welding a welding joint frame according to the present invention is a rectangular tube made of aluminum or an aluminum alloy, having a thickness of 2 to 4 mm, and chamfering the outer and inner surfaces of each corner. Aluminum or aluminum is provided on the side wall of the first welding joint frame, wherein the thickness of the corner is equal to the thickness of the side wall, and the radius of the chamfer of the inner surface of the corner exceeds the thickness and is 8 mm or less. A rectangular cylindrical shape made of an alloy, having a thickness of 2 to 4 mm, at least one end of which has an end surface perpendicular to the longitudinal direction thereof, an outer surface and an inner surface of each corner are provided with chamfers, The thickness of the corner is equal to the thickness of the side wall, and the radius of the chamfer of the inner surface of the corner exceeds the thickness and is 8 mm or less. The end face of the weld joint frame and the first weld joint frame; And said side wall of the over-time, and forming a T-shaped joint by MIG welding without stopping the welding the corners.

According to another welding method for a welding joint frame according to the present invention, a rectangular tube made of aluminum or an aluminum alloy is formed and has a thickness of 2 to 4 mm, and chamfers are provided on the outer and inner surfaces of each corner. The thickness of the corner portion is equal to the thickness of the side wall portion, and the radius of the chamfer of the inner surface of the corner portion exceeds the thickness and is 10 mm or less. And has a thickness of 2 to 4 mm, at least one end of which has an end face perpendicular to the longitudinal direction, and an outer surface and an inner surface of each corner are provided with chamfers, The end face of the second welded joint frame, wherein the thickness of the portion is equal to the thickness of the side wall portion and the radius of the chamfer of the inner surface of the corner exceeds the thickness and is 10 mm or less, The end face of the joint frame and the first weld joint frame; And said side wall of the over-time, and forming a T-shaped joint with TIG welding without stopping the welding the corners.

In the method of the present invention, since the welding is performed by using the welding frame having an appropriate chamfer at the corner, the welding can be performed with a constant welding current. In the welding direction can be reduced. Therefore, turning welding can be performed continuously at the corners without re-targeting the welding torch, and welding workability is improved. Furthermore, since turning welding at the corners becomes extremely easy, it is possible to avoid the treatment of the welding start and end portions at the corners and the vicinity thereof, and to obtain good penetration. Also,
When a pair of welded joint frames provided with an appropriate chamfer is welded to each other, welding can always be performed with the torch aimed at the center of the groove, so that welding workability is further improved.

The welded joint frame according to the present invention has a rectangular cylindrical shape made of aluminum or an aluminum alloy, has a thickness of 2 to 4 mm, and has at least one end having an end surface perpendicular to the longitudinal direction. , The outer and inner surfaces of each corner are provided with chamfers, the thickness of each corner is equal to the thickness of the side wall, and the radius of the chamfer of the inner surface of each corner exceeds the wall thickness It is characterized by the following. In addition,
The radius of the chamfer is desirably 10 mm or less.

[0024]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 (a)
(C) is a diagram showing a welding method according to the first embodiment of the present invention, (a) is a perspective view, (b) is a front view, (c).
FIG. 4 is a cross-sectional view showing the AA plane after welding of FIG. In this embodiment, first, an aluminum shaped member 1 and a shaped member 2 each having a rectangular cylindrical shape having a thickness of 2 to 4 mm are extruded.
Chamfers are formed on the outer surface and the inner surface of the corner 3 in the profile 1 and the profile 2. The thickness of the corner 3 is equal to that of the side wall 4 and is 2 to 4 mm, and the thickness of the entire profile is uniform. In addition, the chamfer of the inner surface of the corner 3 is provided so as to exceed the radius of the chamfer. Further, at least one end of each of the profile 1 and the profile 2 has an end surface perpendicular to the longitudinal direction. Next, the end faces of the profile 1 and the profile 2 perpendicular to the longitudinal direction are butted so that the corners are aligned with each other, and the welding torch makes a round along the butting surface 5 to make the profile 1
And the profile 2 are welded.

The reason for limiting the numerical values of the welded joint frame will be described.

Thickness: 2 to 4 mm If the thickness is less than 2 mm, sufficient strength as a welded structural material cannot be obtained. On the other hand, if the thickness exceeds 4 mm, it is necessary to provide a groove angle on the welding side to secure sufficient penetration, and welding is required, thus increasing the number of steps. Therefore, the thickness is set to 2 to 4 mm.

Inner chamfer radius: If the inner chamfer radius exceeding the wall thickness is less than the wall thickness, it is necessary to rapidly change the welding direction at the time of welding at the corner, and the welding workability deteriorates. I do. Therefore, the radius of the chamfer on the inner surface exceeds the wall thickness.

In the present embodiment, since the profiles having the appropriate chamfers at the corners 3 are welded to each other, it is not necessary to adjust the welding current when welding the corners. The change in direction is reduced. In addition, since turning welding at the corner 3 becomes extremely easy, processing of the welding start and end portions at or near the corner 3 can be avoided. For this reason, as shown in FIG. 1C, no overlap occurs, and a good penetration 6 can be obtained.

The surfaces to be abutted are not limited to the end surfaces having the openings. 4 (a) and 4 (b) are views showing an example in which the side walls are butted, FIG. 4 (a) is a cross-sectional view showing a case where both profiles are chamfered, and FIG. FIG. 4 is a cross-sectional view showing a case where only a shape member is chamfered. As shown in FIGS. 4A and 4B, good penetration 36 is also formed when the side walls are butt-welded.

FIGS. 2A to 2C are views showing a welding method according to a second embodiment of the present invention, wherein FIG.
(B) is a side view, and (c) is a cross-sectional view showing the BB plane after welding of (b). In the present embodiment, first, the first aluminum shaped member 1 having a rectangular cylindrical shape having a thickness of 2 to 4 mm is used.
Extrusion molding of 1 and the 2nd aluminum shape | mold 12 is carried out. The outer shape and the inner shape of the first section 11 are square in cross section. On the other hand, the second section 12 is the section 1 and the section 2
It has the same shape as. Next, the end face of the second section 12 perpendicular to the longitudinal direction thereof is brought into contact with the side wall of the first section 11 and T
The first joints 11 and the second joints 12 are welded to each other by disposing the mold joint and making the welding torch make a round along the butt surface 15.

In the present embodiment, the T-shaped joint is formed by welding the second section 12 having an appropriate chamfer at each corner to the side wall of the first section 11 and welding. So Figure 2
As shown in (c), a good penetration 16 can be obtained in the flare portion as in the first embodiment.

FIGS. 3A to 3C are views showing a welding method according to a third embodiment of the present invention, wherein FIG.
(B) is a side view, and (c) is a cross-sectional view showing the CC plane after welding of (b). In the present embodiment, first, the first tubular member 2 made of aluminum and having a rectangular cylindrical shape having a thickness of 2 to 4 mm.
Extrusion molding of 1 and aluminum 2nd shape material 22 is carried out. The thicknesses of the first section 21 and the second section 22 are the sections 1 and 2
The radius of the chamfer of the inner surface of each corner is set to 8 mm or less, exceeding the wall thickness. next,
The end face of the second section 22 perpendicular to the longitudinal direction is brought into contact with the side wall of the first section 21 to form a T-shaped joint, and the welding torch makes a round along the butting surface 25 to form the first section 21 and the second section. The member 22 is welded.

When both the profiles used in the T-shaped joint are chamfered, the radius of the chamfer on the inner surface is larger than the wall thickness and not more than 10 mm. If the radius of the chamfer on the inner surface is smaller than the wall thickness, it is necessary to change the welding direction abruptly at the time of welding at the corner, and the welding workability is reduced. On the other hand, if the radius of the chamfer of the inner surface exceeds 10 mm, the gap becomes large and it becomes difficult to form a weld bead. Therefore, when both the profiles used in the T-shaped joint are chamfered, the radius of the chamfer on the inner surface is set to be larger than the wall thickness and 10 mm or less.

In this embodiment, the first section 21 and the second section 22 each having an appropriate chamfer at each corner are used to connect the second section 22 to the side wall of the first section 21. Abut on T
Since the mold joint is formed and welded, as shown in FIG. 3C, a good penetration 26 can be obtained in the gap as in the second embodiment.

By assembling the frame structure by welding the above-described welded frames together, welding workability is improved, and a frame structure having a good penetration is obtained.

[0036]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples that fall outside the scope of the claims.

First, using A6N01S-T5 material as a test material, the side wall thickness was 3 mm, the inner surface had a chamfer radius Ro shown in Table 1, and the length of one side in the cross section was 50 m.
m extruded square-shaped members were prepared.

[0038]

[Table 1]

First Embodiment In this embodiment, in the extruded rectangular cylindrical member shown in Table 1 above, the openings are butted together as shown in FIG. 3.2mm in diameter
A5356BY and A5356 with a linear diameter of 1.2 mm
Using WY, manual TIG welding or semi-automatic MIG
Welded. At this time, in TIG welding, the welding current is set to 120 to 150 A, and the welding speed is set to 10 to 3.
0 cm / min. In MIG welding, the welding current is set to 140 to 160 A, and the welding voltage is set to 20 to 2.
2 V and the welding speed was 50 to 80 cm / min.

[0040]

[Table 2]

Then, the welding workability was evaluated. Table 3 shows the results. In Table 3, ◎ indicates particularly good, ○ indicates good, and × indicates bad.

[0042]

[Table 3]

As shown in Table 3 above, Examples 1 to 12
In the above, since the welding is performed using a profile provided with a chamfer within the range specified in the present invention, it is possible to rotate and weld without reducing the welding current, and the welding workability is excellent. . In particular, in TIG welding, when a shape member having Ro of 4 mm or more is used, in MIG welding, R
When o is 6 mm or more, the effect of improvement is extremely high.

On the other hand, in Comparative Example 33, the welding workability was inferior because welding was performed using a profile material that was not chamfered.

Second Embodiment In this embodiment, in the rectangular extruded section shown in Table 1, Ro0 is used as the first section and the extruded section shown in Table 4 is used as the second section. As shown in FIG.
Forming a joint, A5 with 3.2mm diameter as filler material
Manual TIG welding or semi-automatic MIG welding was performed using 356BY and A5356WY having a wire diameter of 1.2 mm. At this time, in TIG welding, the welding current is set to 1
60 to 190 A, and the welding speed is 10 to 30 cm /
Minutes. In MIG welding, the welding current is set to 1
The welding voltage was 20 to 22 V, and the welding speed was 50 to 80 cm / min.

[0046]

[Table 4]

Then, the welding workability was evaluated. Table 5 shows the results. In Table 5, ◎ indicates particularly good, ○ indicates good, and × indicates bad.

[0048]

[Table 5]

As shown in Table 5 above, Examples 13 to 1
In 8, since the section provided with the chamfer within the range specified in the present invention is used as the second section and welded,
Excellent welding workability. As in the first embodiment,
In TIG welding, when a profile having Ro of 4 mm or more is used, and in MIG welding, when a profile having Ro of 6 mm or more is used, the improvement effect is extremely high.

On the other hand, in Comparative Example 34, the welding workability was inferior because welding was performed using a section material without chamfering as the second section material.

Third Embodiment In the present embodiment, a T-shaped joint was formed from the extruded square tubular members shown in Table 1 by combinations shown in Table 6 below as shown in FIG. A5356BY with 3.2 mm diameter and A5356WY with 1.2 mm wire diameter
Was used to perform manual TIG welding. At this time, the welding current was set to 160 to 190 A, and the welding speed was set to 10 to 30 cm / min.

[0052]

[Table 6]

Then, the welding workability was evaluated. Table 7 shows the results. In Table 7, ◎ indicates particularly good, ○ indicates good, and × indicates bad.

[0054]

[Table 7]

As shown in Table 7 above, Examples 19 to 2
In No. 6, the welding workability is excellent because the sections provided with the chamfers within the range specified in the present invention are used as the first section and the second section and are welded. In particular, Ro is 4
In the case where a shape member having a size of 8 mm to 8 mm is used, the improvement effect is extremely high.

On the other hand, in Comparative Example 35, the welding workability was inferior because the welding was performed using the chamfered shaped material which further deviated from the scope of the present invention.

In Comparative Example 36, welding was performed using a profile material that was not chamfered, so that welding workability was poor.

Fourth Embodiment In the present embodiment, a T-shaped joint was formed from the extruded square tubular members shown in Table 1 by combinations shown in Table 8 below as shown in FIG. A5356BY with 3.2 mm diameter and A5356WY with 1.2 mm wire diameter
Was used to perform semi-automatic MIG welding. At this time,
The welding current was 140 to 190 A, the welding voltage was 20 to 22 V, and the welding speed was 50 to 80 cm / min.

[0059]

[Table 8]

Then, the welding workability was evaluated. Table 9 shows the results. In Table 9, ◎ indicates particularly good, ○ indicates good, and × indicates bad.

[0061]

[Table 9]

As shown in Table 9 above, Examples 27 to 3
In No. 2, welding workability is excellent since the sections provided with the chamfers within the range specified in the present invention are used as the first section and the second section and are welded. Especially when Ro is 5
The effect of improvement is extremely high when a profile of mm to 7 mm or less is used.

On the other hand, in Comparative Example 37, the welding workability was inferior because welding was performed using a chamfered profile material which was out of the range of the present invention.

In Comparative Example 38, welding was performed using a profile material that had not been chamfered, so that welding workability was poor.

[0065]

As described above, according to the present invention,
Welding is performed using a rectangular tubular member with an appropriate chamfered corner, so that welding can be performed with a constant welding current even at the corner, and the change in welding direction can be reduced. Since it is eased, welding workability is improved. Furthermore, since turning welding at the corners becomes extremely easy, it is possible to avoid the treatment of the welding start and end portions at the corners and the vicinity thereof, and to obtain good penetration.

[Brief description of the drawings]

FIG. 1 is a view showing a welding method according to a first embodiment of the present invention, wherein (a) is a perspective view, (b) is a front view, and (c) is an AA after welding of (b). It is sectional drawing which shows a surface.

FIGS. 2A and 2B are views showing a welding method according to a second embodiment of the present invention, wherein FIG. 2A is a perspective view, FIG. 2B is a side view, and FIG. It is sectional drawing which shows a surface.

3A and 3B are views showing a welding method according to a third embodiment of the present invention, wherein FIG. 3A is a perspective view, FIG. 3B is a side view, and FIG. It is sectional drawing which shows a surface.

FIG. 4 is a view showing an example in which side walls are joined to each other, and FIG.
FIG. 4 is a cross-sectional view showing a case where both sections are chamfered, and FIG. 4 (b) is a cross-sectional view showing a case where only one section is chamfered.

FIG. 5 is a perspective view showing abutment between openings of a conventional frame.

FIG. 6 is a view showing a conventional method of welding a butt portion;
(A) is a cross-sectional view of the butting surface of FIG. 5 showing one example, and (b) of FIG. 5 is a cross-sectional view of the butting surface of FIG. 8 showing another example.

FIG. 7 is a sectional view showing a DD plane in FIGS. 6 (a) and 6 (b).

FIG. 8 is a schematic diagram showing a space frame structure proposed as used for a general truck.

[Explanation of symbols]

1, 2, 11, 12, 21, 22, 51, 81, 82;
Shapes 3, 65, 66, 67, 68; Corners 4; Side walls 5, 15, 25; Butt faces 6, 16, 26, 36; Penetration 50; Space frames 61, 62, 63, 64; ;Overlap

Claims (8)

[Claims] 1. A rectangular cylindrical frame made of aluminum or an aluminum alloy, having a thickness of 2 to 4 mm, and at least one end of which is welded to a frame having an end surface perpendicular to its longitudinal direction. In the frame structure, the outer surface and the inner surface of each corner of the frame are provided with chamfers, the thickness of each corner is equal to the thickness of the side wall, and the radius of the chamfer of the inner surface of each corner is provided. A frame structure characterized by having a thickness exceeding the wall thickness. 2. The frame structure according to claim 1, wherein a radius of the chamfer is 10 mm or less. 3. A frame having a rectangular cylindrical shape made of aluminum or an aluminum alloy, having a thickness of 2 to 4 mm, at least one end of which has an end surface perpendicular to the longitudinal direction, at least one of which is a frame. The outer and inner surfaces of each corner are provided with chamfers, the corners having a thickness equal to the thickness of the side walls, and the corners having inner chamfer radii exceeding the wall thickness are joined. And welding the butt end without stopping welding at the corner. 4. A rectangular tube made of aluminum or an aluminum alloy and having a thickness of 2 to 4 mm on a side wall of a first welding joint frame having a rectangular tube made of aluminum or an aluminum alloy and having a thickness of 2 to 4 mm. Wherein at least one end has an end surface perpendicular to the longitudinal direction, the outer surface and the inner surface of each corner are provided with chamfers, and the thickness of the corner is equal to the thickness of the side wall, The edge of the inner surface of the corner is chamfered, and the end surface of the second welded joint frame, which exceeds the wall thickness, is brought into contact with the end surface of the second welded joint frame and the side wall of the first welded joint frame. By welding without stopping welding at the corners to form a T-shaped joint. 5. A rectangular tube made of aluminum or an aluminum alloy, having a thickness of 2 to 4 mm, chamfering the outer surface and inner surface of each corner, and the thickness of the corner being the side wall. The side wall of the first welded joint frame is equal to the wall thickness and the chamfer radius of the inner surface of the corner exceeds the wall thickness and is 8 mm or less. 4 mm, at least one of which
The end has an end surface perpendicular to its longitudinal direction, and the outer and inner surfaces of each corner are provided with chamfers, the thickness of the corner is equal to the thickness of the side wall, and the inner surface of the corner is The radius of the chamfer exceeds the wall thickness and is 8 mm or less. The end face of the second weld joint frame is brought into contact with the end face of the second weld joint frame and the side wall of the first weld joint frame. A welding method for a welded joint frame, wherein a T-shaped joint is formed by MIG welding without stopping welding at a corner. 6. A rectangular tube made of aluminum or an aluminum alloy, having a thickness of 2 to 4 mm, chamfering the outer surface and inner surface of each corner, and the thickness of the corner being the side wall. The wall thickness of the first welded joint frame is equal to the wall thickness and the chamfer radius of the inner surface of the corner exceeds the wall thickness and is 10 mm or less. 4 mm, at least one end of which has an end surface perpendicular to the longitudinal direction, the outer surface and the inner surface of each corner are provided with chamfers, and the thickness of the corner is equal to the thickness of the side wall. The radius of the chamfer of the inner surface of the corner portion exceeds the wall thickness and is equal to or less than 10 mm. The end surface of the second welded joint frame is brought into contact with the end surface of the second welded joint frame and the first welded joint frame. Stop welding at the corner with the side wall A method for welding a welded joint frame, wherein a T-shaped joint is formed by TIG welding without forming the joint. 7. A welded joint frame having a rectangular cylindrical shape made of aluminum or an aluminum alloy, having a thickness of 2 to 4 mm, at least one end of which has an end surface perpendicular to a longitudinal direction thereof. The outer surface and the inner surface are provided with chamfers, the thickness of each corner is equal to the thickness of the side wall portion, and the radius of the chamfer of the inner surface of each corner exceeds the thickness. flame. 8. The welded joint frame according to claim 6, wherein a radius of the chamfer is 10 mm or less.