JP2001020081A - Reinforcing member for transport excellent in integranular corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the corrosion resistance such as intergranular corrosion resistance and stress corrosion resistance by providing the surface of a reinforcing member made of an aluminum alloy contg. a specified ratio of Cu and having specified proof stress with an aluminum hydrated oxide film of specified film thickness. SOLUTION: The surface of a reinforcing member made of an aluminum alloy contg., by mass, 0.05 to 3.0% Cu and having >=30 kgf/mm2 proof stress (σ0.2) is provided with an aluminum hydrated oxide film of 100 to 8000 Å film thickness. Preferably, the aluminum alloy is composed of an Al-Zn-Mg aluminum alloy contg., by mass, 0.8 to 1.5% Mg and 5 to 7% Zn or an Al-Mg-Si aluminum alloy contg. 0.2 to 1.8% Si and 0.2 to 1.6% Mg. Preferably, the aluminum alloy is the one subjected to overaging treatment, and moreover, the reinforcing member for a transport airplane is the one excellent in intergranular corrosion resistance which is a door beam material or an extruded shape material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reinforcing member made of an aluminum alloy (hereinafter, aluminum is simply referred to as Al) which is used as a member for reinforcing a door of a transportation machine such as an automobile.

[0002]

2. Description of the Related Art In recent years, in order to solve global environmental problems caused by exhaust gas and the like, improvement in fuel efficiency by reducing the weight of an automobile body has been pursued.
The application of Al alloy materials is also increasing. The current vehicle body has a monocoque structure in which a formed steel plate is assembled into a hat shape by resistance spot welding. However, in order to reduce the weight, molding techniques, joining, and welding techniques have been developed to make these sheet materials into Al alloy materials, and extruded materials (such as hollow cross sections such as hollow sections) integrated by extrusion of Al alloys have been developed. However, there has been proposed a space frame structure using a profile which is essentially the same at any position in the length direction.

[0003] Al alloys have a specific gravity of 1 /
3, have excellent energy absorption,
Furthermore, because of its high degree of freedom in cross-sectional shape, door beams and side members as members for reinforcing automobile doors are used to meet safety standards and improve vehicle performance without increasing vehicle weight. It is used for body reinforcement members (vehicle protection members) such as bumpers and bumper stays, and the demand for these is increasing.

[0004] These reinforcing members for transport aircraft are generally required to have a high maximum load and a high load absorbing performance at the time of collision (external force such as impact). For this reason, for example, 150 kgf / mm ² class high-tensile steel has generally been used for conventional door beams and the like. However, from the viewpoint of the weight reduction,
Application of an extruded material made of an Al alloy is being studied.

[0005] Conventionally, in order to enhance the load absorbing performance of a reinforcing member for a transport machine made of an Al alloy in the event of a collision, see Japanese Patent Application Laid-Open No. HEI 5-3113.
No. 09 proposes a door beam material obtained by subjecting an AA to JIS 7000-based Al-Zn-Mg-based Al alloy extruded material to T6 treatment.
Japanese Patent Application Laid-Open No. 5-247575 discloses a recrystallized layer having a thickness of 70 μm or more on the outer surface of an extruded material of an Al-Zn-Mg-based Al alloy or an AA to JIS 6000-based Al-Mg-Si-based Al alloy. Has been proposed.

Further, Japanese Patent Application No. Hei 10-185139 discloses a method for improving the load absorbing performance at the time of collision when a reinforcing member made of an Al alloy is used as a high-strength material having a higher maximum load. A door beam material has been proposed in which a recrystallized layer having a thickness of 50 μm or less is formed on the outer surface of an extruded material of an Al-Zn-Mg-based Al alloy of AA to JIS 7000 series.

[0007] In these conventional techniques, in order to improve the above-mentioned maximum load and the load absorbing performance at the time of collision, which are required for a reinforcing member for a transport machine, the composition and structure of the Al alloy material are adjusted metallurgically. Is what you are doing.

By the way, in addition to these mechanically required characteristics, important required characteristics (durability) are required for a reinforcing member for a transport aircraft.
Corrosion resistance is required. A transport machine is often used in a salt water corrosive environment such as seawater, and moreover, as a reinforcing member thereof, is often used under a certain stress load state or a state where stress is easily concentrated. Therefore, the reinforcing member for a transport machine is in an operating environment in which the Al alloy material is likely to cause intergranular corrosion, stress corrosion, or the like, or further, intergranular corrosion cracking, stress corrosion cracking, or the like. For this reason, it is required that the reinforcing member for a transport machine also has excellent corrosion resistance, irrespective of the use mode of painting or non-painting, in addition to the mechanically required characteristics.

Particularly, in order to further increase the maximum load and the bending stiffness described above, the proof stress (σ
_0.2) is 40 kgf / mm ² or more, and yield strength Al-Mg-Si-based Al alloy
If (σ _{0. 2)} was a 32 kgf / mm ² or more high-strength material, which following than the low strength material, the grain boundary corrosion and stress corrosion is likely to occur.

In order to increase the strength, it is necessary to add or increase the content of a strengthening element such as Zn or Cu. This is because the susceptibility of the structure of the alloy material to intergranular corrosion and stress corrosion is significantly increased. The increased sensitivity of the material itself, together with the corrosive environment in the transport aircraft, significantly promotes the occurrence of intergranular corrosion and stress corrosion (intergranular corrosion resistance, stress corrosion resistance, intergranular corrosion cracking resistance). The stress and the resistance to stress corrosion cracking).

[0011]

When the corrosion resistance of a high-strength Al alloy reinforcing member for a transport machine is to be improved, Al
There is a limit to means to improve from the material side such as the chemical composition and structure of the alloy material. As described above, the chemical composition and structure of the Al alloy material of the reinforcing member are determined from the required characteristics such as the maximum load and the load absorption performance at the time of collision, and from the viewpoint of corrosion resistance, it is attempted to control the chemical composition and structure. Then, for example, the Zn and Cu are reduced, and a contradiction arises that the mechanical required characteristics are sacrificed.

Therefore, in order to improve the corrosion resistance of the high-strength reinforcing member, it is necessary to improve the corrosion resistance by, for example, treating the surface of the reinforcing member. But,
Conventionally known surface treatments or surface coatings have various problems in applying to the high-strength reinforcing members targeted by the present invention.

[0013] That is, conventionally known surface treatments or surface films of Al alloy materials include Al oxide film, zinc plating film, so-called dacro film treatment combining zinc and chromium, chromate film, resin film (vinyl sheet). Etc.), films of lithium salt, magnesium salt, cerium salt, calcium salt, etc., and potassium permanganate film.

Among them, the galvanized film and the dacro film formed by electricity or substitution have a sacrificial anticorrosion effect, but are liable to deteriorate when they are washed with a chemical or the like when used as a reinforcing member of a transport machine. The durability itself is poor, and as a result, the corrosion resistance cannot be effectively improved.

[0015] In addition, the Al oxide film, when used in a painted state, has poor adhesion to a resin film, impairs the throwing power of the film, and easily causes blistering of the film. Poor corrosion resistance later. Further, when an Al alloy material provided with an Al oxide film is formed or manufactured into a reinforcing member, the formability and weldability are easily hindered.

Although the resin film has an insulating effect, the coating process is complicated and the cost is high. And
The electrodeposition coating property and the adhesion of the coating film when used after being electrically coated are extremely low, and the coating cannot be performed substantially.

In addition, the cost of the other coating films (coating process, etc.) and the waste liquid treatment process are generally high. In particular, chromate films and the like are actually widely used as coating undercoating treatments, but due to the problem of waste liquid treatment, there is a tendency for socially dechromation treatments.

Therefore, there is no surface treatment means or film that can effectively improve the corrosion resistance of the high-strength reinforcing member without any other or newly occurring problem.

The present invention has been made in view of such circumstances, and its object is to provide a surface treatment having no other or newly generated problems, such as intergranular corrosion resistance and stress corrosion resistance. An object of the present invention is to provide a reinforcing member for a transport machine made of a high-strength Al alloy having improved corrosion resistance.

[0020]

In order to achieve this object, the gist of the high-strength aluminum alloy transporting member of the present invention is as follows.
Cu: 0.05 to 3.0% (mass%, the same applies hereinafter)
_0.2 ) is a reinforcing member for an aluminum alloy transporter of 30 kgf / mm ² or more, which has a hydrated oxide film of aluminum on the surface of the reinforcing member.

In the present invention, a hydrated oxide film of Al is provided on the outer surface of the reinforcing member (Al alloy material) to insulate the surface of the Al alloy from the corrosive environment and to prevent the Al alloy from intergranular corrosion resistance and corrosion resistance. Improves corrosion resistance such as stress corrosion.

Further, the hydrated oxide film of Al, like the oxide film of Al, also has the property that it is non-reactive with chemicals such as chemical conversion treatment and the film itself has excellent corrosion resistance. For this reason, there is also an advantage that it can be used basically as a reinforcing material without painting. Further, when used as a reinforcing member of a transport machine, unlike a galvanized film, it does not deteriorate even when washed with a chemical or the like, and has durability, so that a long-term anticorrosion effect can be expected.

Moreover, even when coated as a reinforcing member, adhesion to a resin coating, such as an Al oxide coating,
There is no problem such as throwing power of the coating film or blistering of the coating film, and there is no inferior coating performance and corrosion resistance after coating, guaranteeing good coating adhesion and corrosion resistance of the coating film. It is possible. Also, there is no hindrance to the formability and weldability of the Al oxide film.

Further, the hydrated oxide film of Al has excellent film properties, and can be easily and inexpensively formed by a method of directly contacting high-temperature water or steam as described later. It has no problems and is industrially superior to other coatings. For example, a chromate film, a resin film, a film of a lithium salt, a magnesium salt, a cerium salt, a calcium salt, and the like, a potassium permanganate film, and the other films described above, when provided on the surface of the Al alloy material, the adhesion of the film, or It is inferior to hydrated oxides of Al in terms of formability and weldability. In addition, as described above, the cost of the film treatment (chemical solution or the like) and the waste liquid treatment are generally higher than the hydrated oxide of Al.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Hydrated oxide film of Al)
Therefore, the hydrated oxide film of Al provided on the surface of the Al alloy material is
General formula, Al _TwoO_Three・ XH_TwoHydration reaction of Al oxide represented by O
Refers to a film of a hydrated oxide of Al generated by the above method. And
The hydrated oxide of Al in the present invention refers to the degree of hydration (X
Value, etc.), morphology, crystal structure,
There is no particular limitation on crystallinity and the like. Just Al
Among the hydrated oxides, the pseudo-base in which the value of X is about 1.5 to 1.9.
-Mite is generally called boehmite film.
ing.

The film structure of these hydrated oxides of Al can be identified by infrared spectroscopy (FT-IR) in addition to the morphological observation by the scanning electron microscope. That is, by FT-IR, AlO found in the vicinity 3000~3700cm ^-1 ← → absorption spectrum due to stretching vibration of H, and 1000~1050cm are found in the vicinity of ^-1 Al ← → absorption spectrum due to stretching vibrations of OH, further 800 Absorption spectrum due to stretching vibration of OAl ← → O observed around ~ 600 cm ^-1
Any one or more are recognized, the Al of the present invention
The presence of a hydrated oxide film is confirmed. The thickness of the hydrated oxide film of Al is determined by observing a fracture surface of an Al alloy material (for example, a fracture surface of an Al alloy extruded material by bending at 180 °) by a scanning electron microscope at a magnification of 20,000 or more. be able to.

The hydrated oxide film of Al in the present invention means not only a film composed of pure Al hydrated oxide of Al ₂ O ₃ .XH ₂ O but also a hydrated oxide of Al. As long as it is mainly composed of a material film, it may be a mixture, that is, a material containing an impurity element which may possibly be mixed in or form an Al hydrated oxide film.

For example, a hydrated oxide of Al, Fe, Ni, Co,
A composite film with one or more metal compounds selected from Zn (metal salts of these metals, for example, sulfates, carbonates,
Oxides and hydroxides are contained in the composite film in an amount of at least 1.0 at% in terms of the metal element in terms of the metal element).
Alternatively, a composite or mixed film containing a metal compound such as Si or Mn, which is a metal compound that is lower in potential than the natural potential of Al, in a total amount and an average content in the film of 1 at% or more (these metal materials). Metal salts such as sulfates, carbonates, oxides, and hydroxides are contained in the composite coating in an amount of 1.0 at% or more in terms of the metal element in terms of the metal element). In these cases, the water resistance, the thread rust resistance, and the corrosion resistance such as overall corrosion are more excellent than the case of a film of a hydrated oxide of Al alone. However, the permissible amounts of these metal compounds or impurity elements are within a range that does not impair the properties such as corrosion resistance and adhesion of the hydrated oxide film of Al.

(Film thickness of hydrated oxide film of Al) The film thickness of the hydrated oxide film of Al is determined by the lower limit of the film thickness necessary for exhibiting the insulating effect on intergranular corrosion resistance and the Al alloy material And the upper limit of the film thickness which does not hinder the adhesion to the coating film.
When the thickness of the hydrated oxide film of Al is less than 100 mm, the resistance of the Al alloy material to the synergistic effect of the salt water corrosion environment and the increase in intergranular corrosion susceptibility of the Al alloy material due to the inclusion of Cu. The effect of improving intergranular corrosion cannot be expected. On the other hand, when the thickness of the hydrated oxide film of Al exceeds 8000 mm, other properties such as formability and weldability are hindered, and when painted, the film may not react with the Al alloy material or the paint film. Adhesion decreases,
Peeling of the film or the coating film occurs, and as a result, the intergranular corrosion resistance of the Al alloy material cannot be improved. Therefore, the thickness of the hydrated oxide film of Al is set in the range of 100 to 8000Å (angstrom).

The hydrated oxide film of Al is formed by forming a composite material of a steel material and an Al alloy material into a member for a transport machine, for example.
It may be performed after welding or welding, or after grinding the whole or part of the Al alloy material, or may be performed prior to these processes. Before the formation of the hydrated oxide film of Al, an appropriate pretreatment for degrease or washing the surface of the Al alloy material or the Al alloy of the molding material with an organic solvent, an alkaline solution or an acidic solution is performed. Among these pretreatments, when pretreatment with an aqueous nitric acid solution, the effect of improving the denseness of the hydrated oxide film of Al formed in a later step, suppressing the penetration of moisture, and further improving the water resistance. Have.

The hydrated oxide film of Al has no reactivity or low reactivity with the phosphating bath. Therefore, the above effects can be achieved. The hydrated oxide film of Al itself refers to a film provided in advance before the phosphate treatment, and may be provided immediately before the phosphate treatment or during the phosphate treatment step, or may be an Al alloy material. It may be provided after manufacturing itself and before forming into a product.

After this pretreatment, the surface of the Al alloy material is brought into direct contact with high-temperature water or steam,
After providing an Al oxide layer on the alloy material surface, by hydration reaction
A method of converting to a hydrated oxide film of Al, further, a method of adjusting the hydration amount by heating after providing these hydrated oxide films of Al, or as described in JP-A-05-70969 The method of contacting with a high-temperature neutral or weak alkaline bath (pure water, tap water, an aqueous solution of triethanolamine or ammonia) or the like is appropriately selected, and the two-layer method of the present invention is used.
Create a hydrated oxide film of Al. In the case of an extruded material, particularly, immediately after the hot extrusion of the Al alloy, it is water-cooled by a shower, a spray, or the like online, and is kept for a certain period of time in the presence of high-temperature steam or moisture to oxidize the generated Al. It is also possible to include a substantial amount of hydrated oxide of Al in the coating so as to have the same function as the layer of only hydrated oxide of Al.

As described above, these Al alloy reinforcing members provided with the hydrated oxide film of Al can be used basically without any painting. However, even in the case of painting and using it in relation to other members, etc., according to the painting line of the current automobile etc., after applying a coating base treatment such as phosphate treatment together with steel materials, cationic electrodeposition coating and It is possible to perform a finish coating of a top coat and a top coat, and even in this case, it has the above-mentioned good coating film adhesion.

Next, the Al alloy to which the present invention is applied can be used as a reinforcing member for a transport machine such as a door beam if it satisfies high maximum load and bending stiffness and a load absorbing performance at the time of collision. Al alloys of JIS 3000 series, 5000 series, 6000 series, and 7000 series component standards can be appropriately used. However, taking into account higher strength and other properties such as workability as a reinforcing member and welding, the strength (σ _0.2 ) of Al with a proof stress (σ _0.2 ) of 40 kgf / mm ² or more is considered.
-Zn-Mg based Al alloys and Al with a proof stress (σ _0.2 ) of 32 kgf / mm ² or more
-Mg-Si-based Al alloy is preferred. And Al other than the above standard
All the alloys satisfying the required characteristics of the reinforcing member of the present invention are also applicable to the present invention. For example, it is permissible to appropriately change the component composition in order to further improve the characteristics or add other characteristics. In this regard, according to changes in the component ranges of the above-mentioned elements, and more specifically, non-standard elements such as Ni, V, Zr, Sc, and Ag, and impurities such as H, as appropriate, in accordance with more specific applications and required characteristics. Is acceptable.

The Al alloy material according to the present invention is manufactured as a sheet material or an extruded material by rolling, extruding, or the like according to a conventional method. That is, the molten aluminum alloy melt-adjusted within the component standard range is cast by appropriately selecting a normal melting casting method such as a continuous casting rolling method and a semi-continuous casting method (DC casting method). Next, the ingot is subjected to a homogenizing heat treatment, and hot rolling-cold rolling-tempering treatment (solution treatment and quenching treatment and age hardening treatment), extrusion processing-tempering treatment, hot forging-
By tempering treatment or a combination of these,
An Al alloy material having a desired cross-sectional shape such as a shaped material or a forged material is used.

[0036]

Next, embodiments of the present invention will be described. The usual method
By the (extrusion method), an Al alloy extruded material (profile) having a composition of A to E shown in Table 1 and having a rectangular cross section as a door beam material was produced. Table 3 shows the surface of these extruded materials.
Under the conditions shown in (1), a hydrated oxide film of Al was formed. The hydrated oxide film of Al is formed by immersing each extruded material in 30% nitric acid at 40 ° C for 2 minutes, washing with water, and then adding 0.5% triethanolamine (T
EA) The hydrated oxide film of Al was formed by immersion in an aqueous solution for 30 to 180 seconds, and the thickness of the hydrated oxide film of Al was controlled by changing the temperature and immersion time of the TEA aqueous solution.

As for Invention Example No. 5 in Table 2, each test piece was immersed in 30% nitric acid at 40 ° C. for 2 minutes, washed with water, and then treated with a 90 ° C. aqueous solution containing 4 g / l of nickel acetate for 30 minutes. Then, a composite film with a hydrated oxide of Al containing 5.7 at% of nickel was provided on the surface of the Al alloy. Further, for Invention Example No. 6 in Table 1, each test piece was immersed in 30% nitric acid at 40 ° C. for 2 minutes, washed with water, treated with a 90 ° C. aqueous solution containing 7 g / l of lithium carbonate for 20 minutes, A composite film with a hydrated oxide of Al containing 11 at% of lithium was provided on the surface of the alloy.

[0038] (Identification of hydrated oxide film of Al) just in case, these extruded material, as a result of the hydrated oxide film of Al was identified by FT-IR method, is observed in the vicinity of 3000～3700Cm ^-1 Al
O ← → H absorption spectrum due to stretching vibration, and 1000
Absorption spectra due to the expansion and contraction vibration of Al ← → OH found in the vicinity ~1050cm ^-1, it is found further in the vicinity of 800 ~600cm ^-1
The presence of at least one hydrated oxide film of Al was confirmed by the observation of at least one or more absorption spectra due to stretching vibration of OAl ← → O 2.

For comparison, as shown in Table 3,
In Comparative Example No. 7, an Al alloy extruded material having the same shape and provided with a zinc plating film on its surface by zinc displacement plating was prepared.
No. 8 has the same shape with a natural oxide film of Al.
An Al alloy extruded material was prepared. Further, for No. 9, an Al alloy extruded material from which an oxide film was removed by alkali etching immediately before the zinc phosphate treatment was prepared.

(Grain Intergranular Corrosion Test) Specimens were sampled from the extruded materials of these invention examples and comparative examples, and subjected to a grain boundary corrosion test. The intergranular corrosion test was performed according to the method described in Section 4.4.3 of the JIS W 1103 method, and the intergranular corrosion cracking was evaluated. First, the intergranular corrosion test conditions were as follows: 93 ° C etching solution (70% concentrated nitric acid 50m
l, 48% hydrofluoric acid 5 ml, distilled water 945 ml)
After immersion for minutes, wash the test pieces with distilled water and dry
In a state where it is bent and fixed in a letter shape and stress is applied, a 30 ° C corrosion promoting solution (57 g of NaCl, 10 ml of 30% hydrogen peroxide solution in 1 l of distilled water)
) For 6 hours. Then, the cross-section test piece (cross-section of the test piece) was placed in an etching solution (2.5%
l, concentrated hydrochloric acid 1.5 ml, 48% hydrofluoric acid 1.0 ml, distilled water 9
(5.0 ml composition) for 10 seconds, washed with distilled water, dried, and observed for the corrosion state of the tissue with a 200 × metal microscope.

In the observation of grain boundary corrosion, the corrosion progresses in the thickness direction along the grain boundaries and in a mesh-like or estuary-like manner from the surface in the visual field of the microscope, in distinction from other pitting corrosion or general corrosion. The number of corrosion points, which are typically determined to be intergranular corrosion, and the maximum depth (μm) of intergranular corrosion were determined, averaged in a microscope visual field, and the intergranular corrosion was evaluated. Table 2 also shows these results.

(Stress Corrosion Cracking Test) Similarly, plate-like test pieces were sampled from painted and unpainted Al alloy materials of the invention examples and comparative examples, and subjected to a stress corrosion cracking test. The stress corrosion cracking test conditions were as follows: each specimen was cold-rolled at a processing rate of 30%, and then subjected to a sensitization treatment of heat treatment at 120 ° C for 7 days.
The sensitized test piece was bent into a U-shape with R of 14t and attached to a jig.
The test piece was energized at 0.062 mA / mm ² and immersed in the test solution. The test solution was a 3.5% NaCl aqueous solution at 30 ° C. The presence or absence of occurrence of stress corrosion cracking of the test piece was checked at regular intervals, and the stress corrosion cracking was evaluated based on the time (minutes) until the occurrence. Table 2 also shows these results.

Inventive Examples Nos. 1 to 6 in which an Al hydrated oxide film was provided on the surface of the Al alloy material of the present invention,
Although normal pitting corrosion and the like had occurred, it is clear from the results in Table 2 that no intergranular corrosion had occurred, indicating excellent intergranular corrosion resistance. The stress corrosion cracking generation time is also 1000 minutes or more, which indicates that the Al alloy material of the present invention has excellent stress corrosion resistance.

On the other hand, Comparative Example No. 7 which had been subjected to zinc substitution plating and Comparative Example No. 8 which was a normal Al alloy material having a natural oxide film, and alkali etching was performed immediately before zinc phosphate treatment. In Comparative Example No. 9 which is an example of the Al alloy material from which the oxide film was removed, a large amount of intergranular corrosion occurred, the depth was deep, and it was found that the corrosion progressed in the thickness direction of the extruded material. Further, the stress corrosion cracking generation time is 330 minutes or less, which is significantly shorter than that of the present invention. Therefore, when the comparative example is used as a reinforcing member in a stress-loaded state and in the corrosive environment, based on intergranular corrosion and stress corrosion,
This indicates that intergranular corrosion cracking and stress corrosion cracking may occur.

Therefore, the above facts support the critical significance and the preferred conditions of the present invention.

[0046]

[Table 1]

[0047]

[Table 2]

[0048]

According to the present invention, even if the steel is treated with phosphate in the same line with the steel,
Even if it is phosphated as a composite material with an alloy material,
It is possible to provide a phosphate treatment method for a composite material or a steel material that can suppress elution of Al ions from the surface of the Al alloy material and improve the corrosion resistance after painting of the Al alloy material together with the phosphatability of the steel material. it can. Therefore, the use of the Al alloy material for transportation equipment such as automobiles, vehicles, ships, and the like can be expanded, and thus has a great industrial value.

Claims (7)

[Claims] Claims: 1. A reinforcing member for an aluminum alloy transporting machine containing Cu: 0.05 to 3.0% (mass%, the same applies hereinafter) and having a proof stress (σ _0.2 ) of 30 kgf / mm ² or more, A reinforcing member for transport equipment having excellent intergranular corrosion resistance, comprising a hydrated oxide film of aluminum having a thickness of 100 to 8000 mm (angstrom). 2. The method according to claim 1, wherein the aluminum alloy has a Mg content of 0.8 to 1.5.
The reinforcing member for transport equipment excellent in intergranular corrosion resistance according to claim 1, which is an Al-Zn-Mg-based aluminum alloy containing 4% to 7% of Zn. 3. The method according to claim 1, wherein the aluminum alloy comprises Si: 0.2 to 1.8.
The reinforcing member for a transport machine excellent in intergranular corrosion resistance according to claim 1, which is an Al-Mg-Si-based aluminum alloy containing 0.2% to 1.6% of Mg. 4. The aluminum alloy material according to claim 1, wherein the aluminum alloy has been overaged. 5. The transporting member according to claim 1, wherein the transporting member is a door beam material. 6. The reinforcing member for a transport machine according to claim 1, wherein the reinforcing member for a transport machine is an extruded member. 7. The reinforcing member for a transporting machine according to claim 1, wherein the transporting machine is for an automobile.