阅读说明：本技术 铝合金构件 (Aluminum alloy member ) 是由 杉野弘树 吉田正敏 于 2020-02-25 设计创作，主要内容包括：本发明的铝合金构件,对于在腹板或/和中肋上具有焊合部的铝合金挤压型材进行弯曲加工后,抑制因所述腹板或中肋中发生的拉伸残余应力而导致在所述焊合部发生应力腐蚀开裂。对于铝合金挤压型材(21)进行弯曲加工后在中肋(26)发生的拉伸残余应力的峰位(p)存在于所述焊合部的附近之外的位置。由于所述峰位(p)距焊合部(27e)只离开间隔(D),所以焊合部(27e)的拉伸残余应力被降低,能够抑制应力腐蚀开裂的发生。(The aluminum alloy member of the present invention is an aluminum alloy extruded material having a welded portion in a web or/and a center rib, and is capable of suppressing the occurrence of stress corrosion cracking in the welded portion due to tensile residual stress occurring in the web or the center rib after bending. The peak position (p) of tensile residual stress generated in the middle rib (26) after the aluminum alloy extruded profile (21) is bent is located at a position other than the vicinity of the welded portion. Since the peak position (p) is separated from the welded part (27e) by the distance (D), the tensile residual stress of the welded part (27e) is reduced, and the occurrence of stress corrosion cracking can be suppressed.)

1. An aluminum alloy member comprising an extruded aluminum alloy material having a pair of flanges and a pair of webs connecting the flanges, the webs having a welded portion, and the extruded aluminum alloy material being formed by bending the extruded aluminum alloy material with a bending axis perpendicular to a longitudinal direction and parallel to the pair of flanges, wherein a peak of tensile residual stress existing in the webs is present at a position other than a vicinity of the welded portion.

2. An aluminum alloy member comprising an aluminum alloy extruded profile including a pair of flanges, a pair of webs connecting the pair of flanges, and one or more center ribs located between the pair of webs and connecting the pair of flanges, wherein at least one of the pair of webs and the center ribs has a welded portion, and the aluminum alloy extruded profile is bent with a direction perpendicular to a longitudinal direction and parallel to the pair of flanges as a bending axis, and wherein a peak position of tensile residual stress existing in the pair of webs and the center ribs is located at a position other than a vicinity of the welded portion.

3. An aluminium alloy component according to claim 1 or 2, characterized in that the bending work is a stretch bending work.

4. The aluminum alloy member according to claim 1 or 2, wherein a position other than the vicinity of the welded portion is a region satisfying D.gtoreq.H/10,

wherein, H: height of aluminum alloy member, D: the interval from the welded portion to the peak position, and the unit of H is the same as that of D.

Technical Field

The present invention relates to an aluminum alloy member, and more particularly to an aluminum alloy member such as a bumper reinforcement and a door impact beam, which is produced by bending an aluminum alloy extruded material having a hollow cross section.

Background

Aluminum alloy extruded sections having a hollow cross section are lightweight and have excellent energy absorption properties, and therefore are widely used as materials for automobile members (bumper reinforcement, door impact beam, frame member) and the like which require lightweight and energy absorption properties.

When an automobile member is produced from an aluminum alloy extruded material, the aluminum alloy extruded material is subjected to bending processing from the viewpoint of vehicle body design. This bending work is usually performed with a relatively large curvature, and in pure bending, the forming may be difficult due to springback occurring in an elastically deformed region. In this case, stretch bending is applied to suppress springback.

When an aluminum alloy extruded material is subjected to bending (including stretch bending), residual stress occurs in the cross section of the extruded material due to springback. Tensile residual stresses occur substantially outside the bend relative to the neutral axis of the bend. Then, at the time of stretch-bending, the tensile stress in the axial direction of the extruded material increases, and therefore the position of the neutral axis shifts to the inside of bending, and the peak position of the tensile residual stress approaches the position of the neutral axis at the initial stage (before bending). When the tensile stress is particularly large, the peak position moves to the inside of the bend beyond the position of the initial neutral axis.

Tensile residual stress generated in the aluminum alloy extruded material by the stretch-bending process causes stress corrosion cracking in a corrosive environment. Further, aluminum alloys generally have higher strength and are more susceptible to stress corrosion cracking.

As an aluminum alloy extruded profile having a hollow cross section, a structure including a pair of flanges and a pair of webs connecting the pair of flanges, and a structure having 1 or more center ribs in addition to the pair of flanges and the webs are known. The center rib is located between the pair of webs, connecting the pair of flanges. Such aluminum alloy extrusions are typically produced by split-flow extrusion.

As is well known, this flow dividing extrusion is performed by using a flow dividing die assembly in which a die core body having a plurality of flow dividing holes and a die body are combined. After the aluminum billet pressed into the shunting combined die is divided by the shunting holes, the aluminum billet surrounds the die core and is welded together again to be integrated, the inner surface of the die core is formed, and the outer surface of the die body is formed, so that the extruded section with a hollow section is formed.

In patent documents 1 to 6, with respect to an aluminum alloy extruded material having a hollow cross section, the position of a welded portion in a cross section perpendicular to the extrusion direction is disclosed. According to patent documents 1 to 6, in an aluminum alloy extruded material composed of a pair of flanges and a pair of webs, welded portions are formed at 4 corners (patent documents 1, 2, 4, and 5), or formed on the pair of flanges or/and the pair of webs (patent documents 1, 3, and 6). Further, according to patent document 1, in an aluminum alloy extruded profile having 1 center rib in addition to a pair of flanges and a pair of webs, a weld is formed at 4 corners and the center rib, or at a pair of flanges and a pair of webs and the center rib.

It is known that the aluminum alloy extruded material has different structures and different mechanical properties in the welded portion and other portions than the welded portion (normal portion) (see patent document 2). Specifically, the welded portion has a lower fracture limit than a normal portion, and therefore, there is a problem that the strength of the structural member as the aluminum extruded profile is reduced. Further, the grain size of the aluminum alloy is coarsened in the welded portion as compared with the normal portion, and stress corrosion cracking is likely to occur, which is also a problem (see patent document 7).

[ Prior Art document ]

[ patent document ]

[ patent document 1 ] Japanese patent application laid-open No. 7-227618

[ patent document 2 ] Japanese patent application laid-open No. 8-170139

[ patent document 3 ] Japanese patent application laid-open No. H10-306338

[ patent document 4 ] Japanese patent laid-open No. 2001-71025

[ patent document 5 ] Japanese patent laid-open No. 2016-112603

[ patent document 6 ] Japanese patent No. 6322329

[ patent document 7 ] Japanese patent laid-open No. 2004-149907

The aluminum alloy extruded profile 1 shown in fig. 4 is composed of a pair of flanges 2, 3 and a pair of webs 4, 5, and a center rib 6. When the aluminum alloy extruded material 1 is bent with the direction perpendicular to the longitudinal direction (extrusion direction) and parallel to the flanges 2 and 3 as a bending axis, residual stress occurs in the web plates 4 and 5 and the center rib 6 of the aluminum alloy extruded material 1 after the bending, and the distribution of the residual stress is, for example, in the form shown in the diagram of fig. 4. The position where the tensile residual stress is the maximum (peak position p of the tensile residual stress) is located somewhere in a region between the neutral axis n of bending and the outer end of bending (a range indicated by two arrows in fig. 4), and the position thereof changes depending on the degree of bending (curvature of bending).

When the bending of the aluminum alloy extruded material 1 is a stretch bending (bending with stretching in the longitudinal direction), the peak position p moves inward in the bending, and the residual stress distribution thereof is, for example, in the form shown in the graph of fig. 5. In the stretch bending process, the peak position p of the tensile residual stress is located somewhere in the entire region between the bent inside end portion and the bent outside end portion (the range indicated by the double arrow in fig. 5), and the position thereof varies depending on the degree of bending and the magnitude of the tension applied to the aluminum alloy extruded profile 1.

When the webs 4 and 5 and/or the center rib 6 of the aluminum alloy extruded material 1 are formed with the welded portions, the peak position p may overlap the welded portions in the aluminum alloy extruded material 1 after the bending process depending on the degree of bending and the magnitude of the applied tension. If a high tensile residual stress is generated in the welded portion of the aluminum alloy extruded material 1 after bending, the risk of stress corrosion cracking occurring therein becomes large.

As a measure for suppressing the occurrence of stress corrosion cracking, it is industrially carried out to reduce the residual tensile stress by heat-treating an aluminum alloy extruded material after bending. As another measure for suppressing the occurrence of stress corrosion cracking, an aluminum alloy extruded material having a specific alloy composition and a specific crystal structure has been proposed (see patent document 7).

On the other hand, it has not been considered until now that the occurrence of stress corrosion cracking is suppressed by improving the structural surface of the welded portion including the aluminum alloy extruded material.

Disclosure of Invention

The present invention relates to an aluminum alloy member obtained by bending an aluminum alloy extruded material having a hollow cross section, which is suppressed from stress corrosion cracking that is likely to occur in a welded portion after bending from a viewpoint different from the conventional viewpoint (improvement of a structural surface including the welded portion).

The present invention is an aluminum alloy member comprising an aluminum alloy extruded profile which comprises a pair of flanges and a pair of webs connecting the pair of flanges, has a welded portion in the webs, and is formed by bending the aluminum alloy extruded profile in a direction perpendicular to a longitudinal direction and parallel to the pair of flanges as a bending axis, wherein a peak position of tensile residual stress existing in the webs is present at a position other than a vicinity of the welded portion. In addition, the present invention is characterized in that the aluminum alloy extruded material further includes a center rib in addition to the pair of flanges and the pair of webs, and when a welded portion is provided in at least one of the pair of webs and the center rib, a peak position of tensile residual stress existing in the pair of webs and the center rib exists at a position other than a vicinity of the welded portion.

The weld joint on the web or/and the center rib of the aluminum alloy structural member of the present invention is formed at a position away from the peak of the tensile residual stress. Therefore, the tensile residual stress of the welded portion is lower than the peak value (maximum value), and stress corrosion cracking occurring at the welded portion of the web or/and the center rib can be suppressed.

Drawings

Fig. 1 is a diagram illustrating a relationship between a weld portion on a web and a peak position of tensile residual stress existing in the web in an aluminum alloy member (an aluminum alloy extruded material after bending) according to the present invention.

Fig. 2 is a diagram illustrating a relationship between a weld portion on a center rib and a peak position of tensile residual stress existing in the center rib in the aluminum alloy member (aluminum alloy extruded material after bending) of the present invention.

Fig. 3 is another example of a cross-sectional view of an aluminum alloy extruded profile.

Fig. 4 is a graph illustrating the distribution of residual stress generated in the aluminum alloy extruded profile after unloading in the pure bending process.

Fig. 5 is a graph illustrating the distribution of residual stress occurring in the aluminum alloy extruded profile after unloading of the stretch-bending process.

Description of the symbols

11. 21 aluminum alloy extruded section bar

12. 22 Flange (bending outer side)

13. 23 Flange (bending inner side)

14. 15, 24, 25 webs

17a to 17d, 27a to 27e welded portions

26 middle rib

peak position of p tensile residual stress

D peak position p and interval of welding part

Height of H aluminum alloy extruded section

Detailed Description

The aluminum alloy member of the present invention will be specifically described below with reference to fig. 1 to 3.

The aluminum alloy extruded profile 11 shown in fig. 1 is composed of a pair of flanges 12 and 13 and a pair of webs 14 and 15 connecting the flanges 12 and 13, and welded portions 17a to 17d are formed on the flanges 12 and 13 and the webs 14 and 15. The flanges 12, 13 are parallel to each other and the webs 14, 15 are perpendicular with respect to the flanges 12, 13.

After the aluminum alloy extruded material 1 is subjected to bending processing with the direction perpendicular to the longitudinal direction (extrusion direction) and parallel to the flanges 12 and 13 as the bending axis, residual stress in the longitudinal direction (extrusion direction) is generated in each of the webs 14 and 15 in the aluminum alloy extruded material 11 (aluminum alloy member) after unloading. When the bending is a pure bending in which no tension is applied in the longitudinal direction, the peak position p of the tensile residual stress is located somewhere in the region between the neutral axis n of the bending and the outer end of the bending as shown in fig. 4, and the position thereof changes depending on the degree of the bending. In addition, when the bending process is a stretch bending process in which tension is applied in the longitudinal direction, as shown in fig. 5, the peak position p moves inward in the bending process with respect to the case of pure bending, and the position thereof changes depending on the degree of bending and the tension. The measurement of the distribution of residual stress generated in the web plates 14 and 15 after the bending process can be performed by a known measurement method such as an X-ray diffraction method or a strain gauge method.

In the aluminum alloy extruded material 11 (the aluminum alloy member of the present invention) after bending, the peak position p of the tensile stress in the web plates 14, 15 is present at a position other than the vicinity of the welded portions 17c, 17 d. In the present invention, the vicinity of the welded portions 17c and 17D means a region that substantially satisfies D < H/10, where H is the height (distance from the outer end to the inner end of the bend) of the aluminum alloy member and D is the distance from the welded portions 17c and 17D to the peak position p, as shown in fig. 1. In this region, the positions themselves of the bonding portions 17c and 17D are also included (D is 0). The positions other than the vicinity of the welded portions 17c and 17D mean regions that substantially satisfy D.gtoreq.H/10. Wherein H and D have the same unit.

In the bending process of the aluminum alloy extruded profile 11, if the degree of bending and the tension are determined, which position on the webs 14 and 15 the peak position p reaches can be predicted by an experiment. In the extrusion of the aluminum alloy extrudate 11, the positions where the weld portions 17c and 17d are formed are determined by the structure of the split die. Therefore, if the degree of bending and the tension are determined, by performing appropriate die design, the welded portions 17c and 17D can be formed in the region satisfying D.gtoreq.H/10, so that the peak position p of the tensile residual stress occurring in the aluminum alloy member (the aluminum alloy extruded profile 11 after bending) can be avoided from the welded portions 17c and 17D, and the aluminum alloy member can be separated from the welded portions 17c and 17D by the distance D (. gtoreq.H/10). This reduces the tensile residual stress in the welded portions 17c and 17d of the aluminum alloy member, and can suppress the occurrence of stress corrosion cracking.

An aluminum alloy extruded profile 21 shown in fig. 2 includes a pair of flanges 22 and 23 and a pair of webs 24 and 25, and 1 center rib 26 between the pair of webs 24 and 25, and welded portions 27a to 27e are formed at 4 corners and the center rib 26. The flanges 22, 23 are parallel to each other and the webs 24, 25 and the central rib 26 are perpendicular with respect to the flanges 22, 23.

After the aluminum alloy extruded material 21 is subjected to bending processing with the direction perpendicular to the longitudinal direction (extrusion direction) and parallel to the flanges 22 and 23 as the bending axis, residual stress in the longitudinal direction occurs in the webs 24 and 25 and the center rib 26 in the unloaded aluminum alloy extruded material 21 (aluminum alloy member). When the bending process is a pure bending, the peak position p of the tensile residual stress is located somewhere in the region between the neutral axis n of the bending and the outer end of the bending, as shown in fig. 4, and the position thereof changes depending on the degree of the bending. When the bending process is stretch bending, as shown in fig. 5, the peak position p moves inward in bending with respect to the case of pure bending, and the position thereof changes depending on the degree of bending and the tension. The measurement of the residual stress occurring in the center rib 26 after the bending process can be performed by a well-known measurement method such as an X-ray diffraction method or a strain gauge method, as described above.

In the aluminum alloy extruded material 21 (the aluminum alloy member of the present invention) after the bending, the peak position p of the tensile residual stress in the middle rib 26 is present at a position other than the vicinity of the welded portion 27 e. In the present invention, the vicinity of the welded portion 27e means a region that substantially satisfies D < H/10, where H is the height (distance from the outer end to the inner end of the bend) of the aluminum alloy member and D is the distance from the welded portion 27e to the peak p, as shown in FIG. 2. In this region, the position itself of the bonding portion 27e is also included (D ═ 0). The position other than the vicinity of the welded portion 27e means a region substantially satisfying D.gtoreq.H/10.

In the bending process of the aluminum alloy extruded material 21, if the degree of bending and the tension are determined, which position on the center rib 26 the peak position p reaches can be predicted by an experiment. In the extrusion of the aluminum alloy extruded material 21, the position where the weld portion 27e is formed is determined by the structure of the split die. Therefore, if the degree of bending and the tension are determined, the weld portion 27e can be formed at a position satisfying D ≧ H/10 by performing appropriate die design, so that the peak position p of the tensile residual stress occurring in the aluminum alloy member (aluminum alloy extruded profile 21 after bending) is avoided from the weld portion 27e and is separated from the weld portion 27e by only the interval D (≧ H/10). This reduces the tensile residual stress in the welded portion 27e of the aluminum alloy member, and can suppress the occurrence of stress corrosion cracking.

Fig. 3 shows another example of the cross-sectional shape of the aluminum alloy extruded material as the material of the aluminum alloy member of the present invention.

The aluminum alloy extruded material 31 shown in fig. 3A is composed of a pair of flanges 32 and 33 and a pair of webs 34 and 35, and each of the flanges 32 and 33 has a protruding flange (a portion protruding outward of the webs 34 and 35) on the left and right.

An aluminum alloy extruded profile 41, shown in fig. 3B, has a pair of flanges 42, 43 and a pair of webs 44, 45, and 2 center ribs 46, 47.

An aluminum alloy extruded profile 51 shown in FIG. 3C has a pair of flanges 52, 53 and a pair of webs 54, 55, and 3 center ribs 56-58.

In the case where the aluminum alloy extruded shapes 31, 41, 51 are also bent with the direction perpendicular to the longitudinal direction and parallel to the flange as the bending axis, the occurrence of stress corrosion cracking can be suppressed by forming the welded portions of the web and/or the center rib at positions satisfying D.gtoreq.H/10 in advance.

The aluminum alloy extruded material as a material of the aluminum alloy member of the present invention is not particularly limited, but a 7000-series aluminum alloy extruded material having high strength, in which the problem of stress corrosion cracking is likely to occur, can be preferably used. As the composition of the 7000-series aluminum alloy, the composition specified in JIS or AA standard can be applied. Preferred compositions include the following: contains Zn: 3-8 mass%, Mg: 0.4 to 2.5 mass%, Cu: 0.05 to 2.0 mass%, Ti: 0.005 to 0.2 mass%, further containing Mn: 0.01 to 0.5 mass%, Cr: 0.01 to 0.3 mass%, Zr: 0.01 to 0.3 mass% or more, and the balance of Al and impurities.