JP2019026897A - Aluminum alloy sheet for structural member, and manufacturing method of aluminum alloy structural member - Google Patents

Abstract

To provide a 6000 series aluminum alloy structural member having strength and crush resistance, and a stock sheet thereof.SOLUTION: Both of strength and crush resistance are achieved by setting average area percentage of a Cube orientation of a structural member surface consisting of a 6000 series aluminum alloy with a specific composition, and average area percentage of the Cube orientation at a 1/4 thickness position of thickness of the structural member at a constant value or more, and making the average area percentage of the Cube orientation at the 1/4 thickness position of thickness of the structural member larger than the average area percentage of the Cube orientation of the structural member surface.SELECTED DRAWING: None

Description

  The present invention relates to an aluminum alloy plate for an aluminum alloy structural member having both high strength and pressure resistance, and a method for producing an aluminum alloy structural member using the aluminum alloy plate as a raw material.

  In response to global environmental problems caused by exhaust gas from automobiles, improvement in fuel consumption of transportation equipment such as automobiles is required. For this reason, in particular, a lighter aluminum alloy material is applied as an automobile structural member in place of a conventionally used steel material. Typical automotive structural members that use aluminum alloy plates include thin panel materials such as hoods, fenders, doors, and roofs, which are made by press forming the material plates. However, it is going to be expanded to an automobile structural member as a structural member requiring a rigidity of 2 mm or more and relatively thick.

  Compared to the above-mentioned automobile panels, automobile structural members for structural members that are relatively thick and require rigidity have higher strength of the material plate and shock absorption at the time of vehicle collision = pressure resistance It is necessary to newly provide a fracture property (also referred to as a crush property or a crush property).

  Among high-strength reinforcing materials among automotive structural members such as bumper reinforcing materials and door beams, extruded shapes produced by hot extrusion of JIS or AA7000 series aluminum alloys are already widely used as raw materials. Yes. On the other hand, large structural members such as frames and pillars may be made of a rolled plate manufactured by a conventional method such as hot rolling after soaking or further cold rolling the ingot. preferable. However, the above-mentioned 7000 series aluminum alloy is difficult to make as a rolled plate because of its high alloy, and has not been practically used so far.

  For this reason, as an alloy for a rolled sheet manufactured by normal rolling (ordinary method), it is an Al—Mg—Si based aluminum alloy that is easy to make because it is a lower alloy than the 7000 series, and JIS to AA6000 series. Aluminum alloys are noted.

This 6000 series aluminum alloy plate is already used as a large body panel (outer panel or inner panel such as a hood, fender, door, roof, trunk lid, etc.) of an automobile.
Therefore, in order to improve characteristics such as press formability including bending workability and hem workability and BH property (bake hardness) including room temperature aging control, which are required for these large body panels of automobiles. Therefore, many metallurgical improvement measures have been proposed, such as defining the composition of the components and the texture such as the Cube orientation in the plate surface and in the plate thickness direction.

As a typical example of the provision of this texture, for example, in Patent Document 1, the BH property is excellent, the room temperature aging after producing the plate is small, and even when left for a long time, there is little decrease in formability due to hardening due to natural aging. In addition, it has excellent forming processability (bending processability, hemming processability), has low bending anisotropy, suppresses ridging marks during forming process, and has excellent intergranular corrosion resistance. There has been proposed a method capable of manufacturing an aluminum alloy plate for industrial use reliably and stably at a low cost on a mass production scale.
Specifically, it is made of a 6000 series aluminum alloy having a specific composition, and is an average value of a cube orientation density at a position 1/10 of the plate thickness from the plate surface and a cube orientation density at a position 1/4 of the plate thickness from the plate surface. However, specific conditions such as homogenization treatment, hot rolling, solution treatment conditions, etc. are specified such that the relationship is higher than the cube orientation density at a position 1/2 the plate thickness (center position in the plate thickness direction) from the plate surface. Control as a range.

  However, the above-described automotive structural members such as frames and pillars, which are the subject of the present invention, are different from the automotive panel structural member uses described in Patent Document 1 and the like, and are further enhanced in strength and shock absorption at the time of a vehicle collision. A new characteristic peculiar to the use of the structural member is required, such as a new property = breakdown resistance.

  As an example of this, in recent years, due to the level-up (strictening) of crash safety standards for automobiles, in Europe and the like, the automobile structural members such as the frames and pillars are standardized by the German Automobile Manufacturers Association (VDA) “VDA238. -100 Plate Bending Test for Metallic Materials (hereinafter referred to as VDA bending test), which is required to satisfy the impact absorption (crush resistance, crushing characteristics) at the time of automobile collision. Yes.

  With respect to such strict safety standards, the 6000 series aluminum alloy plate in which the texture and the texture inside the plate are controlled for the above-described conventional automobile panel, more commonly in the case of an automobile structural member, There is a problem that the pressure-breaking resistance is insufficient after increasing the strength.

On the other hand, in Patent Document 2, Sn is newly added to a 6000 series aluminum alloy plate, and an Sn series compound having an equivalent circle diameter in the range of 0.2 to 10 μm is present at the crystal grain boundary of this plate. It has been proposed to control the average number density of these to 0.4 pieces / μm ³ or less (including 0 pieces / μm ³ ).
The aluminum alloy sheet has 0.2% proof stress of 200 MPa or more as a characteristic (as an automobile structural member) after solution treatment / quenching treatment and artificial aging treatment, and 75 ° or more in a VDA bending test. It is said that it has the crushing characteristic which becomes the bending angle of.

Japanese Patent No. 4602195 Japanese Patent Laid-Open No. 2006-160516

  However, as in Patent Document 2, when a necessary amount of Sn is newly added, there is a problem that it becomes difficult to make a rolled plate, such as a decrease in workability, and it is also necessary to change the manufacturing process and manufacturing conditions. I want to avoid the addition. However, as described above, in the conventional structure control such as a texture of a 6000 series aluminum alloy plate, there is a great limit to the improvement of strength and pressure resistance as an automobile structural member.

  Therefore, there is still room for development in order to increase the strength of a structural member made of a 6000 series aluminum alloy plate (hereinafter also simply referred to as a 6000 series aluminum alloy structural member) and to improve the pressure resistance.

The present invention has been made paying attention to such circumstances, and is a raw material 6000 series aluminum alloy plate for obtaining a 6000 series aluminum alloy structural member having improved strength and pressure resistance (shock absorption). And it aims at providing the manufacturing method of the said structural member using this raw material 6000 series aluminum alloy plate.

  In order to achieve this object, an embodiment of an aluminum alloy plate for a structural member is the aluminum alloy plate for an aluminum alloy structural member, and Mg: 0.3 to 1.5 mass%, Si: 0.3 Containing ~ 1.5 mass%, the balance is made of Al-Mg-Si based aluminum alloy consisting of Al and inevitable impurities, and the plate thickness is 2 mm or more and 5 mm or less, measured by SEM-EBSD method As a texture, the average area ratio of Cube orientation in a rectangular region of 5 mm × 5 mm on the plate surface is 20% or more, and 5 mm × 5 mm of a plane parallel to the plate surface at a ¼ thickness position of the plate thickness The average area ratio of the Cube orientation in the rectangular region is 25% or more, and the Cube orientation at the 1/4 thickness position of the plate thickness is larger than the average area ratio of the Cube orientation on the plate surface. The average area ratio of the azimuth is larger.

  An embodiment of a method for producing an aluminum alloy structural member for achieving the above object is to form a structural member by press forming after adding a pre-strain of 5 to 15% to the aluminum alloy plate, By subjecting this structural member to artificial aging treatment, the average area ratio of the Cube orientation in a rectangular region of 5 mm × 5 mm on the surface of the structural member is 25% or more, and at the 1/4 thickness position of the thickness of the structural member. The average area ratio of the Cube orientation in a rectangular area of 5 mm × 5 mm of the plane parallel to the surface of the structural member is 30% or more, and the thickness of the structural member is larger than the average area ratio of the Cube orientation of the structural member surface. A texture having a larger average area ratio of the Cube orientation at the 1/4 thickness position is 0.2% proof stress of the structural member after the artificial aging treatment is 220 MPa or more. Is that you have a crush properties that make VDA bending than 80 ° of bending angle in the test.

The present inventor examined the texture of a 6000 series aluminum alloy plate as a material for improving the pressure resistance after making the structural member stronger.
As a result, the aluminum alloy plate has a plate thickness direction defined by the aluminum alloy plate for structural members according to the embodiment of the present invention, and a plate defined by the method for manufacturing an aluminum alloy structural member according to the embodiment of the present invention. In the case of having a texture of a specific Cube orientation such as a distribution in the plane direction, when the artificial aging treatment as a structural member is performed after adding more pre-strain, the specific texture is It has been found that the structural member can be further strengthened and the strength of the structural member can be improved and the pressure resistance can be improved.

That is, as the texture of the material 6000 series aluminum alloy plate, particularly when the distribution of the Cube orientation in the plate thickness direction and the plate surface direction is controlled, more pre-strain is added to the material plate. Then, when artificial aging treatment as a structural member is performed, the Cube orientation in the thickness direction of the structural member is further developed, and even in the surface direction of the structural member, there is no portion where the area ratio of the Cube orientation is locally low. It becomes possible to make the area ratio of the Cube orientation uniform.
For this reason, the balance between strength and bendability (breakdown resistance) as a structural member is improved, and the strength can be increased and the breakup resistance (shock absorption) can be improved.

As a result, the Cube orientation was not sufficiently developed so that the texture of the 6000 series aluminum alloy plate as the material could increase the strength of the structural member after the artificial aging treatment and improve the pressure fracture resistance. However, by using such a material 6000 series aluminum alloy plate, it becomes possible to make a structural member having a sufficiently developed Cube orientation capable of increasing the strength and improving the fracture resistance after artificial aging treatment. .
This eliminates the need for special additions and changes in the manufacturing process and manufacturing conditions for sufficiently developing the Cube orientation of the 6000 series aluminum alloy plate, which is the material of the structural member, and greatly reduces the load on plate manufacturing. Is possible.

Hereinafter, embodiments of the present invention will be specifically described for each requirement.
In the present invention, for automobile structural members that require rigidity, forming a plate having a complicated three-dimensional shape such as a cylindrical shape and obtained by press-forming an aluminum alloy plate (rolled plate) as a material Main uses are structural members such as automobile structural members made of body. Therefore, in the following description, among the structural members, this automobile structural member will be described. However, the present invention is not limited to automobile structural members, and may be used for other structural members.

Thickness, plate thickness:
As an embodiment of the 6000 series aluminum alloy plate, the plate thickness is 2 mm or more and 5 mm or less. When the thickness or the plate thickness is less than 2 mm, the strength and rigidity as a structural member are insufficient. Further, when the plate thickness exceeds 5 mm, the plate thickness is too thick, so that it is impossible to press-form the material aluminum alloy plate to the structural member. Moreover, the effect of weight reduction by an aluminum alloy which should be replaced with a steel plate or steel as a structural material is impaired. In the following description, the thickness of the structural member and the thickness of the aluminum alloy plate of the material are collectively referred to as thickness or plate thickness.

Aluminum alloy composition:
The embodiment of the chemical component composition of the 6000 series aluminum alloy sheet will be described below.
The chemical composition of the 6000 series aluminum alloy plate satisfies the composition and strength of the material plate as a structural member such as the automobile structural member or the structural member, including the formability and BH property, from the viewpoint of composition. In addition, it is assumed that the manufacturing conditions of the plate by rolling by a conventional method are not greatly changed. Note that the% display of the content of each element means mass%.
The chemical composition of the aluminum alloy plate for this purpose includes, as an Al—Mg—Si based aluminum alloy, Mg: 0.3 to 1.5 mass%, Si: 0.3 to 1.5 mass%, and the balance Is made of Al and inevitable impurities.
In addition to this composition, Cu: 0.001-0.7 mass%, Mn: 0.05-0.5 mass%, Zr: 0.04-0.20 mass%, Cr: 0.04-0. 20% by mass, Sc: 0.02-0.1% by mass, Ag: 0.01-0.2% by mass, Sn: 0.001-0.1% by mass good.

Si: 0.3 to 1.5% by mass
Si, together with Mg, forms an aging precipitate that contributes to strength improvement during solid solution strengthening and artificial aging treatment such as paint baking treatment, exhibits age-hardening ability, and strength (proof strength) required for automobile structural materials ) Is an essential element for obtaining.
If the Si content is less than 0.3% by mass, the Si content is too small, the amount of dissolved Si before paint baking (before artificial aging) decreases, and the amount of aging precipitates generated is insufficient. The properties are significantly reduced and the strength is insufficient.
On the other hand, if the Si content exceeds 1.5% by mass, a coarse compound is formed during the production of the plate, and ductility is deteriorated. Accordingly, the Si content is in the range of 0.3 to 1.5 mass%, preferably 0.7 to 1.4 mass%.

Mg: 0.3 to 1.5% by mass
Mg, together with Si, forms aging precipitates that contribute to strength improvement with Si during solid solution strengthening and artificial aging treatment such as paint baking treatment, and exhibits age-hardening ability and is necessary as a structural material for automobiles It is an essential element for obtaining proof stress.
If the Mg content is less than 0.3% by mass, the Mg content is too small, the amount of dissolved Si before paint baking treatment (before artificial aging treatment) decreases, and the amount of aging precipitates produced is insufficient. The properties are significantly reduced and the strength is insufficient.
On the other hand, if the Mg content exceeds 1.5% by mass, a shear band is easily formed during cold rolling of the plate, which causes cracking. Therefore, the Mg content is in the range of 0.3 to 1.5 mass%, preferably 0.4 to 1.2 mass%.

One or more of Cu, Mn, Zr, Cr, Sc, Ag, Sn Cu, Mn, Zr, Cr, Sc, Ag, Sn are commonly effective in increasing the strength of the material plate and the structural member. It can be regarded as a synergistic element in a broad sense, but there are, of course, common parts and different parts in its specific mechanism.

In addition to contributing to strength improvement by solid solution strengthening, Cu also has the effect of promoting age hardening of the structural member and contributing to strength improvement during artificial aging treatment. In order to acquire such an effect of Cu, when containing selectively, it is preferable to contain 0.001 mass% or more. On the other hand, when there is too much content of Cu, there exists a possibility that corrosion resistance may deteriorate, and it is unpreferable. Therefore, the Cu content is preferably 0.7% by mass or less.
In addition, when further increasing the area ratio of the Cube orientation of the surface of the structural member or plate by applying pre-strain to the product and controlling the artificial aging treatment, the Cu content is preferably 0.3% by mass or less, Preferably it is 0.2 mass% or less. If the Cu content exceeds 0.3% by mass, more strictly 0.2% by mass, the concentration of Cu dissolved in the aluminum matrix increases, which causes strain accumulation in the Cube-oriented grains during prestraining. There is a possibility that it works in the direction of increasing and hinders the effects of the growth of the Cube-oriented grains and the increase of the area ratio after the artificial aging treatment.

Mn, Zr, Cr, and Sc refine crystal grains of the ingot and the plate to improve the strength. If each of these contents is less than the lower limit, the effect is insufficient. On the other hand, when these contents are too large and exceed the respective upper limit values, a coarse compound is formed, and the impact absorbability (crush characteristics) is deteriorated.
Therefore, when selectively contained, Mn: 0.05 to 0.5% by mass, Zr: 0.04 to 0.20% by mass, Cr: 0.04 to 0.20% by mass, Sc: 0 The range is 0.02 to 0.1% by mass.

  Ag is selected as needed because it has the effect of closely and finely precipitating aging precipitates that contribute to strength improvement by artificial aging treatment after forming processing (press molding) into a structural material, thereby promoting high strength. To be included. If the Ag content is less than 0.01%, the effect of improving the strength is small. On the other hand, if the Ag content is too large, various properties such as rollability and weldability are deteriorated, and the effect of improving the strength is saturated and only expensive. Accordingly, the Ag content in the case of inclusion is in the range of 0.01 to 0.2% by mass.

  Sn has the effect of suppressing the cluster formation at room temperature and maintaining the excellent formability of the plate after solution treatment and quenching treatment for a long time, and further subjected to artificial aging treatment such as baking coating treatment after that. The strength of the structural member in the case is improved. If the Sn content is less than 0.001%, the effect is small, and if it exceeds 0.1%, the effect is saturated, and on the other hand, hot embrittlement occurs and the hot workability (hot ductility) is remarkably deteriorated. . Therefore, the Sn content in the case of inclusion is in the range of 0.001 to 0.1% by mass.

Other elements:
Other elements such as Ti, B, Fe, Zn, and V other than those described above are unavoidable impurities, and are allowed to be contained within the range specified by the JIS standard as a 6000 series alloy.

Texture:
On the premise of the above thickness and composition, in the present invention, by controlling the distribution of the 6000 series aluminum alloy plate for the structural member, particularly in the Cube orientation, in the plate thickness direction and the surface direction, respectively, the structural member is used. Improves the balance between strength and bendability (crush resistance).

(Cube orientation distribution control in the thickness direction)
For this purpose, first, as the texture measured by the SEM-EBSD method of the material plate, the average area ratio of the Cube orientation in a rectangular area of 5 mm × 5 mm on the surface of the plate is set to 20% or more, and the plate of the material plate The average area ratio of the Cube orientation in a rectangular region of 5 mm × 5 mm of a plane parallel to the plate surface at a 1/4 thickness position is 25% or more, and is more than the average area ratio of the Cube orientation on the plate surface The average area ratio of the Cube orientation at the 1/4 thickness position of the thickness of the material plate is increased. Here, the rectangular area referred to in the present invention means a rectangular area in a plane or a rectangular plane area.

  When a 6000 series aluminum alloy plate is used as the structural member, the texture of the structural member after the artificial aging treatment is a texture in which the Cube orientation has been developed so as to increase the strength and improve the puncture resistance (shock absorption). This is a necessary condition.

  Here, in order to ensure the combination of high strength and pressure proof fracture (impact absorbability) as a structural member, as a texture in which the Cube orientation of the structural member is developed, a Cube in a rectangular region of 5 mm × 5 mm on the surface is used. The average area ratio of orientation is 25% or more, and the average area ratio of Cube orientation in a rectangular region of 5 mm × 5 mm of a plane parallel to the surface of the structural member at a thickness of 1/4 of the thickness of the structural member is 30. % Or more is preferable. In addition to this, it is preferable that the average area ratio of the Cube orientation at the 1/4 thickness position of the thickness of the structural member is larger than the average area ratio of the Cube orientation of the surface of the structural member.

In the case of a structural member in which the Cube orientation is developed, as a result of analyzing the influence of the distribution in the thickness direction of the Cube orientation on the fracture resistance = the VDA bendability, the result is 1 than the Cube orientation grain on the surface of the structural member or the plate. The Cube orientation (1 / 4t part) grains at the / 4 thickness position greatly contribute to the improvement of the pressure resistance.
That is, in order to improve the fracture resistance, the Cube orientation in a rectangular area of 5 mm × 5 mm of a plane parallel to the plate surface at the 1/4 thickness position of the plate thickness (hereinafter, simply referred to as a 1/4 t portion Cube orientation). The area ratio of (say) contributes more than the Cube orientation (hereinafter also simply referred to as the Cube orientation of the surface) in a 5 mm × 5 mm rectangular region on the plate surface.
This is because even if a micro crack is formed on the surface of a structural member that is being used as an automobile structural member due to a load such as a vehicle body collision, the 1/4 direction Cube orientation of this structural member prevents the crack from progressing. It is because it has the effect to do.
This fact indicates that if the required amount of 1/4 direction Cube orientation is present, the fracture resistance is improved even if the surface Cube orientation is not larger than the 1/4 t portion Cube orientation. If the Cube orientation is decreased and insufficient, it means that no matter how much the Cube orientation on the surface is increased, the pressure-breakdown resistance is not improved.

(Development of Cube orientation)
As the texture of the 6000 series aluminum alloy plate, as in the present invention, when the distribution of the Cube orientation, the plate thickness direction, or the plane direction of the plate to be described later is controlled, more prestrain When an artificial aging treatment is applied as a structural member, the Cube orientation in the thickness direction of the structural member is further developed, and the area ratio of the Cube orientation is also locally low in the plane direction of the structural member It is possible to make the area ratio of the Cube orientation uniform by eliminating the portions.

This is because, when a 6000 series aluminum alloy plate as a material is made into a texture in which the Cube orientation defined above is developed, it is subjected to artificial aging treatment as a structural member after adding more pre-strain. This is because the specific texture is further developed.
Although there is no distortion in the material plate after tempering such as solution treatment, a specific strain is newly added to the material plate without this strain by cold working, and artificial aging is further performed under specific conditions. When the treatment is performed, it is possible to further increase the Cube orientation of the surface of the structural member and the Cube orientation of the 1/4 t portion by the grain growth and coarsening of the Cube orientation grains.
When a new strain is applied to a material plate without strain after tempering such as a solution treatment by means of cold working, a Cube orientation grain in which strain is difficult to accumulate and a non-Cube orientation in which strain is likely to accumulate. There is a difference in accumulated strain between the grains. In this state, when the artificial aging treatment is performed, the Cube orientation grains in which strain is not accumulated due to the thermal history at the time of the artificial aging treatment is reduced by the driving force that reduces the strain of the surrounding non-Cube orientation grains having a high accumulated strain amount. The grain boundary movement of the grains is promoted and the area ratio of the Cube orientation can be further increased by the grain growth and coarsening of the Cube orientation grains.

However, even when the Cube orientation is further developed in this way, as described above, the average area ratio of the Cube orientation in a 5 mm × 5 mm rectangular region on the surface of the 6000 series aluminum alloy plate is 20% or more, and the plate of the plate The average area ratio of the Cube orientation in a rectangular region of 5 mm × 5 mm of the plane parallel to the plate surface at the 1/4 thickness position is 25% or more and more than the average area ratio of the Cube orientation on the plate surface It is necessary as a premise that the average area ratio of the Cube orientation at the 1/4 thickness position of the plate thickness is larger.
Thus, if the amount of Cube orientation grains of a certain amount or more does not exist before the prestrain is added (if the Cube orientation is not developed), the effect of increasing the Cube orientation by prestrain + artificial aging treatment does not appear. .

  For example, when the average area ratio of the Cube orientation on the surface of the 6000 series aluminum alloy plate is less than 20% or the average area ratio of the Cube orientation at the 1/4 thickness position of the plate thickness is less than 25%, cold working ( Even if it is further developed from the Cube orientation of the plate (material plate) by a combination of pre-strain) and artificial aging treatment, the average area ratio of the Cube orientation in the thickness direction of the structural member can be satisfied. Most likely not.

  The preferable conditions for the pre-straining by cold working and the artificial aging treatment such as paint baking treatment for developing the Cube orientation as the structural member will be described in detail in the section of the manufacturing method of the structural member.

(Cube orientation distribution control in the plane direction)
Furthermore, in the embodiment for controlling the texture, it is preferable to control the distribution of the surface direction of the Cube orientation of the material plate (the surface or a surface parallel to the surface).
Control of the distribution of the Cube orientation in the plane direction, that is, the distribution control of the Cube orientation on the surface of the material plate or the structural member and the Cub orientation of the 1 / 4t portion in the plane direction, in other words, the control of the local distribution of the Cube orientation in the plane direction. However, it leads to further improvement of the pressure resistance.

The Cube orientation of the material plate or the structural member also varies in the surface direction (width direction or longitudinal direction of the material plate), and even if the area ratio of the Cube orientation as the average value is high, the Cube orientation of the material plate or the structural member is locally If there is a portion with a low area ratio, the microcracks are likely to occur at the portion, which may promote the occurrence of surface cracks and propagation in the thickness direction.
In order to suppress this, it is preferable to eliminate a portion where the area ratio of the Cube orientation is locally low, and to reduce the degree of deterioration (variation) from the average area ratio. It is preferable to maintain a lower limit value of at least a certain value in order to exhibit the effect of further improving the pressure-breakdown resistance.

Specifically, in the case of a material plate, when the aluminum alloy plate further divides the rectangular region into each rectangular region of 1000 μm × 1000 μm, the Cubes on the surface of the plate at all these divided portions The minimum value of the area ratio of the orientation is 15% or more, and the minimum value of the area ratio of the Cube orientation of the plane parallel to the plate surface at the 1/4 thickness position of the plate thickness is 20% or more. Is preferred.
When this is a structural member, the minimum value of the area ratio of the Cube orientation on the surface of the structural member at all of the divided areas when the rectangular area is further divided into rectangular areas of 1000 μm × 1000 μm. Is set to 20% or more, and the minimum value of the area ratio of the Cube orientation at the ¼ thickness position of the thickness of the structural member is preferably set to 25% or more.

  Incidentally, in the conventional structure control, there is no analysis of the influence of the distribution in the thickness direction of the Cube orientation on the pressure breakdown property as in the present invention, and the control from such a viewpoint has not been performed.

(Measuring method of texture)
Each crystal orientation defined above is measured by SEM-EBSD method using a scanning electron microscope (SEM) or a field emission scanning electron microscope (FE-SEM). evaluate.
The sample to be used for the measurement is the surface of the structural member or material plate from an arbitrary position of the structural member or material plate, and the surface of the structural member or material plate at a 1/4 thickness position of the thickness of the structural member or material plate. Five test materials including a measurement region (5 mm × 5 mm rectangular region) are collected from a plane parallel to the surface.
Then, after mechanically polishing and buffing the surface of the test material, electrolytic polishing is performed to prepare a surface to be a measurement surface of the test material.

At this time, in the case of the surface of the structural member, the coating film or oxide film on the surface is removed, and the aluminum matrix at the interface of these films is exposed to form a measurement surface.
Moreover, if it is a test material in the 1/4 thickness position of the thickness of a structural member or a board, a surface parallel to the surface of a structural member or a board will be exposed, and it will be set as a measurement surface.
The measurement results by the SEM-EBSD method of these five specimens are averaged to obtain the average area ratio (%) of the Cube orientation of each part defined in the present invention.
However, only the minimum value of the area ratio of the Cube orientation is not averaged, and the smallest one of the measured values of the individual test materials or the individual measurement sites of the test materials is calculated based on the Cube orientation. The minimum value of the area ratio.

This SEM-EBSD method is widely used as a measurement method of crystal orientation texture, and is applied to a field emission scanning electron microscope (for example, JSM-7000F manufactured by JEOL Ltd.) with a backscattered electron diffraction image (EBSD). Pattern: EBSD) A crystal orientation analysis method equipped with a system.
In the SEM-EBSD method, a sample of an Al alloy plate set in the lens barrel of the FE-SEM is irradiated with an electron beam, and the diffraction pattern of the backscattered electrons is measured by an EBSD apparatus (for example, EBSD measurement manufactured by TSL).・ Analysis system: OIM (Orientation Imaging Macrograph) Data & Analysis) scans the sample surface every 1 μm while analyzing the crystal orientation. Thereby, an EBSP (Electron Back Scatter Diffraction Pattern) at each point is obtained and indexed, and the crystal orientation of the electron beam irradiation site is obtained. The crystal orientation distribution function when the obtained crystal orientation measurement data is rotated by 90 ° around the rolling direction axis and further rotated by 90 ° in the normal direction of the rolling surface and the crystal orientation is measured by EBSD in the entire measurement region. Calculate (ODF) and area ratio. Details of the crystal orientation analysis method in which the EBSD system is mounted on these FE-SEMs are described in detail in Kobe Steel Technical Report / Vol. 52 No. 2 (Sep. 2002) P66-70 and the like.

Production method:
Next, an embodiment of a manufacturing method of an aluminum alloy plate or a structural member that is an application thereof will be described below.
The 6000 series aluminum alloy plate is a hot-rolled plate that is hot-rolled after soaking the ingot, or a cold-rolled plate that is cold-rolled from the hot-rolled plate, and is further subjected to tempering such as solution treatment. It is manufactured by a conventional method. That is, the process itself is manufactured by a usual method through normal manufacturing processes such as casting, homogenization heat treatment, and hot rolling to obtain an aluminum alloy hot rolled sheet having a thickness of about 2 to 10 mm. Subsequently, it is cold-rolled to obtain a cold-rolled sheet having a thickness of 2 mm or more and 3 mm or less.

  Therefore, the material plate may not be manufactured using a special manufacturing method or a rolling method in which hot rolling is omitted by cold rolling after thin plate continuous casting such as a twin roll method, or warm rolling is performed.

(Dissolution, casting cooling rate)
First, in the melting and casting process, an ordinary molten casting method such as a continuous casting method and a semi-continuous casting method (DC casting method) is appropriately selected for the molten aluminum alloy adjusted to be dissolved within the above-mentioned 6000 series component composition range. Cast.

(Homogenization heat treatment)
Next, the cast aluminum alloy ingot is subjected to a homogenization heat treatment prior to hot rolling. The purpose of this homogenization heat treatment (soaking) is to homogenize the structure, that is, eliminate segregation in crystal grains in the ingot structure. The conditions for this soaking process have no effect on the texture to be defined, including the cooling rate, and may be normal soaking only once, or twice soaking or two-stage soaking. In one soaking, the hot rolling is started by cooling to the hot rolling start temperature or holding at or near the hot rolling start temperature.

  In the second soaking, after the first soaking, the steel sheet is once cooled to a temperature of 200 ° C. or less including room temperature, reheated, and maintained at that temperature for a certain time, and then hot rolling is started. On the other hand, the two-stage soaking means cooling after the first soaking, but it is not cooled to 200 ° C. or lower, and after stopping the cooling at a higher temperature, the temperature is maintained as it is. The hot rolling is started after reheating to a higher temperature.

  The soaking condition for the first soaking in only one time, the first soaking in the second time, or the soaking in the second stage soaking is maintained at 450 ° C. or more and the solidus temperature for 2 hours or more. Select as appropriate from the time range. By setting the soaking temperature to 450 ° C. or higher, the solid solution of the insoluble precipitate in the ingot is promoted, and the strength as the final structural member is increased.

  In the second soaking, after the first soaking, the temperature is once cooled to 200 ° C. or less including room temperature for the second soaking. In the two-stage soaking, after the first stage soaking, the temperature is once cooled to a temperature higher than 200 ° C. The soaking condition for the second or second stage is selected from the range of the holding time of 2 hours or more in the temperature range of the hot rolling start temperature or higher and 500 ° C. or lower. It may be heated and cooled to the hot rolling start temperature, or reheated to the hot rolling start temperature and held in the vicinity thereof. Further, the ingot after soaking at the first stage may be cooled to the hot rolling start temperature and held in the vicinity thereof. The soaking temperature at the second or second stage is preferably lower than the soaking temperature at the first or first stage.

(Hot rolling)
In this hot rolling, in order to obtain a specified texture, the hot rolling start temperature (hot rough rolling start temperature), the total rolling reduction (%) of the rough rolling, and the end of the hot rolling are performed under conditions different from the conventional methods. It is necessary to control the temperature (hot finish rolling end temperature) in combination.

The hot rough rolling start temperature is preferably selected from a range of 350 ° C. to 450 ° C. so as to be lower than the soaking temperature.
The total rolling reduction of the hot rough rolling is preferably 90% or more.
The finishing temperature of hot finish rolling is preferably as low as possible, preferably 150 to 280 ° C.
In this way, by combining the conditions of hot rough rolling start temperature, hot finish rolling end temperature, rough rolling reduction ratio, grain growth after recrystallization during hot rolling is suppressed, and grain coarsening is achieved. Can be suppressed.
In addition, by making the crystal grain structure of the hot-rolled material at the end of hot-rolling a fine fiber structure and minimizing the texture unevenness (texture structure distribution) in the plate width direction as much as possible, the macro variation is suppressed and the final Local variation in the area ratio of the Cube orientation in a simple structural member can be suppressed.
When the hot rolling conditions do not satisfy these conditions, the crystal grain structure (aggregate structure) at the end of hot rolling varies macroscopically, and there is a high possibility that the pressure fracture resistance is lowered.

(Cold rolling)
In cold rolling, the hot-rolled sheet is rolled to produce a cold-rolled sheet (including a coil) having a desired final sheet thickness in the range of 2 to 5 mm for a structural member. The number of cold rolling processes is freely selected according to the relationship between the thickness of the hot rolled sheet and the final thickness of the cold rolled sheet, and the sheet (coil) to the cold rolling mill in this cold rolling process. The number of passes can be freely selected.
Incidentally, the annealing (roughening) of the hot-rolled sheet before cold rolling and the intermediate annealing in the middle of cold rolling do not have to be performed, but may be performed as necessary.

(Solution treatment)
After cold rolling, solution treatment and quenching treatment corresponding to T4 are performed as the tempering of the plate. For this solution treatment, heating and cooling by a normal continuous heat treatment line may be used. However, in order to obtain a sufficient amount of solid solution of each element and refinement of crystal grains, a solidus temperature of 500 ° C. or higher is required. It is desirable to perform the solution treatment at the following temperature at a holding time in the range of 1 second to 30 minutes.
Here, it is preferable that the average temperature increase rate during the solution treatment from 20 ° C. to the solution temperature range of 500 ° C. to the solidus temperature is in the range of 100 to 400 ° C./min. By making this average temperature rising rate within the above range, the surface of the plate or the structural member or the development of the Cube orientation of the 1/4 t portion is promoted.
If this average temperature rise rate is out of this range and is too fast, the area ratio of the desired Cube orientation on the plate or the final structural member cannot be obtained, and local variations in the Cube orientation cannot be suppressed. Sex occurs. In addition, if this average temperature rise rate is out of this range and is too slow, the productivity is extremely reduced, which is industrially difficult.

  The average cooling (cooling) rate after the solution treatment is preferably set to a range of 200 ° C. to solidus temperature of 40 ° C./second or more in order to prevent formation of coarse compounds at grain boundaries. For this reason, the cooling after the solution treatment is performed by selecting and using forced cooling means such as air cooling such as a fan, water cooling means such as mist, spraying, and immersion, or directly in water or hot water at room temperature to 100 ° C. It is preferable to quench.

(Preliminary aging treatment: reheating treatment)
After such solution treatment, quenching treatment and cooling to room temperature, the cold-rolled plate may be subjected to preliminary aging treatment (reheating treatment) if necessary.

Through the above steps, the average area ratio of the Cube orientation in a rectangular area of 5 mm × 5 mm on the plate surface is 20% or more, and 5 mm of the plane parallel to the plate surface at the 1/4 thickness position of the plate thickness. The average area ratio of the Cube orientation in a rectangular area of 5 mm is 25% or more, and the average of the Cube orientation at the 1/4 thickness position of the plate thickness of the plate than the average area ratio of the Cube orientation on the plate surface A material plate with a larger area ratio is obtained.
However, the control for developing the Cube orientation of these material plates follows the control for developing the Cube orientation in the manufacturing process of the material plates up to the conventional solution treatment.

For this reason, it is not easy to obtain a texture in which the Cube orientation is developed, which satisfies the provisions as the structural member according to the embodiment of the present invention at the stage of the material plate. However, it is not always possible to obtain a texture in which the Cube orientation has been developed that satisfies the above-mentioned definition.
For this reason, as defined in the present invention, the texture of the material plate is set as a texture where the Cube orientation has been developed as much as possible, and in the production of the structural member described later, the strain applied by forming the material into the structural member It is preferable to further develop the Cube orientation by adjusting the amount, the temperature of the artificial aging treatment after the paint baking treatment, or the holding time.
In addition, even if the Cube orientation is not sufficiently developed so that the texture of the material plate can increase the strength of the structural member and improve the puncture resistance, using such a material plate, It is also an advantage of the present invention that it is possible to obtain a structural member having a texture in which the Cube orientation is sufficiently developed so as to increase the strength and improve the pressure resistance.

Manufacturing method of structural members:
The tempered aluminum alloy plate is subjected to press molding and processing including burring processing, hole expansion processing, and the like as a raw material, and is used as a structural member such as an automobile, a bicycle, or a railway vehicle. Furthermore, if necessary, surface treatment such as electrodeposition and coating treatment, and artificial aging treatment (bake hard, BH) such as paint baking treatment, or artificial aging treatment (bake hard, BH) without painting are performed. .
This artificial aging treatment can also be performed at the stage of the aluminum alloy plate before being formed into a member.
In addition, from the viewpoint of securing moldability, after being molded and processed into these structural members, the artificial age hardening treatment may be performed separately to increase the strength as necessary.

  Here, as described above, artificial aging treatment was performed after pre-straining the material plate having the texture, and the average area ratio of the Cube orientation of the surface of the structural member was 25% or more, The average area ratio of the Cube orientation of the 1 / 4t portion is 30% or more, and the average area ratio of the Cube orientation of the 1 / 4t portion is larger than the average area ratio of the Cube orientation of the surface. It becomes important.

  For this reason, cold working such as tension, cold rolling, leveler, stretch, etc. is further added to the material plate without any strain after tempering such as solution treatment in press molding or before and after press molding. Further, after adding a strain in the range of 5 to 15% to the molded structural member, artificial aging treatment is further performed under a specific condition, so that the area ratio of the Cube orientation can be further increased. .

However, when these strains are applied, after the tempering (after manufacture), the aluminum alloy plate is aged at room temperature for at least 6 hours after the tempering, and then by the press molding or cold working. It is preferable to add a strain in the range of 5 to 15%.
These pre-strains are preferably added in the rolling direction of the material plate even in the structural material in order to sufficiently exhibit the effect of further increasing the area ratio of the Cube orientation.
By applying the pre-strain within the above range after the room temperature aging time after the solution treatment, the effect of the pre-strain is maximized. If the room temperature aging time and the amount of pre-strain are small, the accumulated strain difference cannot be obtained, the grain boundary movement of the Cube-oriented grains is also reduced, and the area ratio of the Cube-oriented is further increased by the grain growth and coarsening of the Cube-oriented grains. The increase effect is not sufficiently exhibited.

  In addition, the artificial aging treatment condition is preferably set in a range of 170 to 230 ° C. × 5 to 30 minutes in relation to the above-described prestrain amount. When deviating from the temperature range or the range between holding, there is a possibility that the area ratio of the Cube orientation cannot be further increased in combination with the pre-strain of the specific range.

  Furthermore, in order to increase the average area ratio of the Cube orientation of the structural member more than the average area ratio of the Cube orientation at the material stage, as a precondition, the average of the above-described surface Cube orientation at the stage of the material plate is assumed. The area ratio is set to 20% or more, the average area ratio of the 1 / 4t part Cube orientation is set to 25% or more, and the average area ratio of the 1 / 4t part Cube orientation to the average area ratio of the surface Cube orientation. It is necessary to increase the rate. That is, if the amount of Cube orientation grains of a certain amount or more does not exist before the prestrain is added, the effect of increasing the Cube orientation by the prestrain + artificial aging treatment does not appear.

Next, examples of the present invention will be described. The aluminum alloy plate having the composition shown in Table 1 was subjected to homogenization heat treatment, hot rolling, and cold rolling under the conditions shown in Table 2, and tempered to produce a material plate.
These material plates were simulated for structural members and pre-strained under the conditions shown in Table 2 and then subjected to artificial aging treatment. The 2% proof stress and the fracture resistance by the VDA bending test were measured and evaluated. These results are shown in Table 3, respectively.
In addition, in the display of the content of each element in Table 1, an element whose numerical value is blank indicates that the content is below the detection limit.
Moreover, in Tables 1-3, the numerical value etc. which attached the underline means having removed from the range of embodiment of this invention.

Below, the more concrete manufacturing conditions of an aluminum alloy raw material board are demonstrated. Ingots having respective compositions shown in Table 1 were melted by a DC casting method. Subsequent homogenization heat treatment was performed at the homogenization temperature (attainment temperature) shown in Table 2 for 4 hours in common with each example.
When the soaking pattern is twice soaking, after the first soaking shown in Table 2, in common, once cooled to a temperature of 200 ° C. or less including room temperature, the hot rolling start temperature shown in Table 2 Until reheated. Moreover, in the case of one-time soaking, after soaking shown in Table 2, it was cooled to the hot rolling start temperature, and hot rolling was started at that temperature.
Hot rolling was carried out at the hot rolling (rough rolling) start temperature shown in Table 2, the total rolling reduction of the rough rolling, and the hot rolling (finish rolling) end temperature. And the final board thickness of each hot-rolled board was made into 2.2-10 mm.

The hot-rolled sheet after hot rolling was cold-rolled to obtain a cold-rolled sheet having a thickness of 2 mm in common.
This cold-rolled sheet is subjected to a solution treatment under the conditions of the average rate of temperature increase (° C./min) and the holding temperature (solution temperature) shown in Table 2, and the range from 200 ° C. to the solidus temperature is 40 ° C. / The plate was cooled to room temperature at a cooling rate of at least 2 seconds, and then subjected to a pre-aging treatment at 100 ° C. for 8 hours to obtain a tempered T4 blank.

  The material plate of this tempered T4 is aged in room temperature for each time (time) shown in Table 2 after the tempering in common with each example, and after simulating the structural members, Under each condition shown, after prestraining (tensile) was applied in the rolling direction of the plate, artificial aging treatment was performed under each condition shown in Table 2.

  Here, in the case of the invention example, in order to confirm the effect of increasing the area ratio of the Cube orientation of this pre-strain, the artificial aging treatment was performed under each condition shown in Table 2 without applying the pre-strain by the tensile tester. The example which performed only after the same time as room temperature aging time until provision of pre-strain passed was implemented as a reference example. Invention examples 1, 3, 5, 7, 9, and 11 in Tables 2 and 3 correspond to this reference example.

(mechanical nature)
The tensile test of the artificially aged plate was processed into a JIS No. 5 test piece so that the tensile direction was perpendicular to the rolling direction, and a constant speed until the test piece broke at a tensile rate of 5 mm / min with a distance between ratings of 50 mm. I went there. 0.2% yield strength (MPa) was measured. The tensile test piece used for measuring the mechanical properties was a JIS2201 No. 13A test piece (20 mm × 80 mmGL × plate thickness 1 mm) so that the tensile direction from the test plate was parallel to and perpendicular to the rolling direction. . In addition, the number of measurements of these tensile tests was set to 2 times, and 0.2% yield strength was calculated | required by the average value. These results are listed in Table 3.

(Gathering organization)
As the texture measured by the SEM-EBSD method, the average area ratio of the Cube orientation in the 5 mm × 5 mm rectangular region of the surface of the tempered T4 material plate and the artificially aged plate simulating a structural member ( %), An average area ratio (%) of Cube orientation in a rectangular area of 5 mm × 5 mm of a plane parallel to the plate surface at a thickness position of ¼ thickness, and the rectangular area is further divided for each rectangular area of 1000 μm × 1000 μm. The minimum value (%) of the area ratio of the Cube orientation on the surface of the plate at all of the divided locations when divided, and the minimum value (%) of the area ratio of the Cube orientation at the 1/4 thickness position of the thickness of the plate ) Were measured by the measurement methods described above.
The measurement conditions were a visual field area of 800 μm × 800 μm and a distance (step size) between crystal orientation measurement points of 3 μm. After measurement, crystal orientation analysis was performed using OSL version 5 manufactured by TSL as orientation analysis software. These results are listed in Table 3.

The bending test for evaluating the impact absorbability was carried out as a VDA bending test in accordance with “VDA238-100 Plate Bending Test for Metallic Materials” in the standards of the German Automobile Manufacturers Association (VDA).
The test method consists of a plate-like test piece collected from the plate after artificial aging treatment simulating a structural member, its rolling direction, and the extending direction of a plate-like pushing and bending jig arranged vertically upright. However, they are placed horizontally on the two rolls arranged in parallel with each other so that the central portion thereof is positioned in the center of the roll gap so as to be parallel to each other.
Then, the pressing and bending jig is pressed against the center of the plate-shaped test piece from above to apply a load, and the plate-shaped test piece is bent toward the narrow roll gap (bending) to bend and deform. The center part of the plate-shaped test piece is pushed into the narrow roll gap. At this time, when the load F from the push bending jig from above is maximized, the angle of the outer side of the center of the plate-shaped test piece is measured as the bending angle (°), and the bending angle is large. Now evaluate the shock absorption.
The larger the bending angle, the more the plate-like test piece is not crushed in the middle, the bending deformation is continued, and the shock absorption (crushing property) is higher. These results are listed in Table 3.
Here, the plate-shaped test piece has a square shape of width: 60 mm × length: 60 mm, the two roll diameters D are each 30 mm, and the roll gap is 4 mm, which is 2.0 times the plate-shaped test piece plate thickness. . In addition, the plate-like pushing / bending jig had a tapered shape in which the lower end side pressed against the central portion of the plate-like test piece was pointed so that the radius of the tip (lower end) was 0.2 mmφ.

As shown in Tables 1 to 3, the material plate (of the tempered T4) of each invention example is manufactured within the composition range of the present invention and within the preferable range of each manufacturing condition.
For this reason, as shown in Table 3, the material plate of each invention example has a texture before the artificial aging treatment defined in the present invention, the average area ratio of the Cube orientation of the surface is 20% or more, and 1 The average area ratio of the Cube orientation of the / 4t portion is 25% or more, and the average area ratio of the Cube orientation of the 1/4 t portion is larger than the average area ratio of the Cube orientation of the surface.
As a result, the invention example generally has a 0.2% proof stress of 220 MPa or more when artificial aging treatment is performed by simulating a structural material used as a material, and a bending angle of 80 ° or more in the VDA bending test. It has the crushing characteristics, and has both strength and crushing resistance.

Inventive examples 3, 4, 5, 6, 9, 10, 11, and 12 in Table 3 are divided when the rectangular area is divided into rectangular areas of 1000 μm × 1000 μm. The minimum value of the area ratio of the Cube orientation on the surface of the plate at all locations is 15% or more, and the minimum value of the area ratio of the Cube orientation at the 1/4 thickness position of the thickness of the plate is 20% or more.
For this reason, Invention Example 1 in which the minimum value of the area ratio of the Cube orientation on the plate surface is less than 15% or the minimum value of the area ratio of the Cube orientation in the 1/4 thickness position of the thickness of the plate is less than 20%. Compared to 2, 7, and 8, the 0.2% proof stress and the crushing property in the VDA bending test are relatively excellent when the artificial aging treatment is performed.

Furthermore, the invention members 2, 4, 6, 8, 10, 12 in Tables 2 and 3 in which the structural members were simulated and these material plates were subjected to artificial aging treatment after pre-straining in a preferable range The average area ratio of the Cube orientation is 25% or more, the average area ratio of the Cube orientation of the 1 / 4t part is 30% or more, and the average area ratio of the Cube orientation of the surface is more than that of the 1 / 4t part. The average area ratio of the Cube orientation is larger.
Of these invention examples, Invention Examples 4, 6, 8, 10, and 12 in Tables 2 and 3 are all divided when the rectangular area is divided into rectangular areas of 1000 μm × 1000 μm. The minimum value of the area ratio of the Cube orientation on the surface of the plate at the location is 25% or more, and the minimum value of the area ratio of the Cube orientation at the 1/4 thickness position of the thickness of the plate is 25% or more.

Here, the textures of these Invention Examples 2, 4, 6, 8, 10, 12 and Invention Examples 1, 3, 5, 7, 9, and 11 of Tables 2 and 3 that are not pre-strained, Next to each other, 1 and 2, 3 and 4, 5 and 6, 7 and 8, 9 and 10, and 11 and 12 are compared.
Then, Invention Examples 2, 4, 6, 8, 10, and 12 were subjected to an artificial aging treatment with a pre-strain, and the average surface area ratio of the plate surface and the 1/4 t part Cube orientation, and the plate surface and 1 / The minimum value of the area ratio of the Cube orientation of the 4t part is increased from those of Invention Examples 1, 3, 5, 7, 9, and 11 that are not pre-strained, and in 0.2% proof stress and VDA bending test. The crushing property is relatively excellent.
Therefore, as an effect of applying the artificial aging treatment after prestraining in the preferred range, the Cube orientation in the thickness direction of the structural member is further developed, and the Cube orientation is also locally localized in the plane direction of the structural member. This eliminates the area where the area ratio is low and supports the effect of making the area ratio of the Cube orientation uniform.

In contrast, in Comparative Examples 13 to 19, as shown in Tables 1 to 3, the material plate is manufactured within the composition range of the present invention, but the manufacturing conditions are out of the preferable range.
For this reason, as shown in Table 3, in the material plates of these comparative examples, the average area ratio of the Cube orientation of the 1/4 t part is smaller than the average area ratio of the Cube orientation of the surface, or the Cube orientation of the surface The average area ratio is less than 20%, or the average area ratio in the Cube orientation of the 1/4 t portion is less than 25%, which is out of the texture defined in the present invention.
In addition, when an artificial aging treatment is performed after pre-straining a material plate of tempered T4 by simulating a structural member, the average area ratio of the Cub azimuth of the ¼ t portion is the Cube azimuth of the surface The average area ratio of the Cube orientation of the surface is less than 25%, or the average area ratio of the Cube orientation of the 1 / 4t part is less than 30%, which is outside the texture defined by the present invention. ing.
As a result, the 0.2% proof stress is less than 220 MPa or less than 80 ° in the VDA bending test when simulating the structural material used for the material plate and artificial aging treatment, and it has both strength and pressure resistance. Not done.

In Comparative Example 13, the homogenization temperature is too low.
In Comparative Example 14, the hot rolling start temperature (rough rolling) is too high.
In Comparative Examples 14 and 15, the artificial aging treatment temperature is too high.
In Comparative Examples 15 and 16, the hot rolling end temperature (finish rolling) is too high.
In Comparative Example 17, the total rolling reduction of rough rolling is too low, and the elapsed time until pre-strain is applied is too short.
In Comparative Examples 18 and 19, the average temperature increase rate during the solution treatment is too fast, and the solution temperature is too low.

  In Comparative Examples 20 and 21, as shown in Table 1, the Mg and Si contents of Alloy Nos. 7 and 8 are too small, and the production conditions are in a preferable range. In spite of having a structure, the 0.2% proof stress is less than 220 MPa when artificial aging treatment is performed by simulating a structural material, and it does not have both strength and pressure resistance.

  From the above results, the significance of the composition and texture defined in the present invention for combining strength and pressure resistance, and the significance of preferred production conditions for obtaining these are supported.

  According to the present invention, it is possible to improve the strength and puncture resistance (impact absorbability) of a plate manufactured by rolling and a structural member made of this plate as a molding material by systematic innovation of a 6000 series aluminum alloy. It becomes possible. As a result, the application of a 6000 series aluminum alloy plate can be expanded as a structural member for automobiles and the like.

Claims (5)

Al—Mg containing Mg: 0.3 to 1.5 mass%, Si: 0.3 to 1.5 mass%, the balance being made of Al and inevitable impurities, and having a plate thickness of 2 mm or more and 5 mm or less -Si-based aluminum alloy plate,
As the texture measured by the SEM-EBSD method, the average area ratio of the Cube orientation in a rectangular area of 5 mm × 5 mm on the plate surface is 20% or more, and the plate surface at the 1/4 thickness position of the plate thickness The average area ratio of Cube orientation in a rectangular area of 5 mm × 5 mm on a parallel surface is 25% or more, and the Cube orientation at the 1/4 thickness position of the plate thickness is larger than the average area ratio of Cube orientation on the plate surface. An aluminum alloy plate for a structural member, characterized in that the average area ratio of orientation is greater.   When the aluminum alloy plate divides the rectangular area into rectangular areas each having a size of 1000 μm × 1000 μm, the minimum value of the area ratio of the surface Cube orientation at each of the divided areas is 15% or more. The aluminum alloy plate for a structural member according to claim 1, having a texture in which the minimum value of the area ratio of the Cube orientation of a plane parallel to the plate surface at a 1/4 thickness position of the plate thickness is 20% or more.   In addition, Cu: 0.001 to 0.7 mass%, Mn: 0.05 to 0.5 mass%, Zr: 0.04 to 0.20 mass%, Cr: 0.04 to 0.20 mass% Or Sc: 0.02 to 0.1% by mass, Ag: 0.01 to 0.2% by mass, Sn: 0.001 to 0.1% by mass, or one or two or more thereof. 2. The aluminum alloy plate for structural members according to 2.   The texture after adding a pre-strain of 5 to 15% and being subjected to artificial aging treatment at 170 to 230 ° C. × 5 to 30 minutes is the average of the Cube orientation in a rectangular region of 5 mm × 5 mm on the plate surface The area ratio is 25% or more, the average area ratio of the Cube orientation in a rectangular area of 5 mm × 5 mm of the plane parallel to the plate surface at the 1/4 thickness position of the plate thickness is 30% or more, and It has a texture in which the average area ratio of the Cube orientation at the 1/4 thickness position of the plate thickness of the plate surface is larger than the average area ratio of the Cube orientation on the plate surface, and 0.2% proof stress of 220 MPa or more The aluminum alloy plate for a structural member according to any one of claims 1 to 3, wherein the aluminum alloy plate has a crushing characteristic that gives a bending angle of 80 ° or more in a VDA bending test.   The aluminum alloy plate according to any one of claims 1 to 4, wherein a pre-strain of 5 to 15% is added to the aluminum alloy plate, press forming to form a structural member, and the structural member is subjected to artificial aging treatment, thereby the structural member An average area ratio of Cube orientation in a rectangular area of 5 mm × 5 mm on the surface is 25% or more, and a 5 mm × 5 mm rectangle parallel to the surface of the structural member at a quarter thickness position of the structural member The average area ratio of the Cube orientation in the region is 30% or more, and the average area ratio of the Cube orientation at the 1/4 thickness position of the thickness of the structural member is larger than the average area ratio of the Cube orientation on the surface of the structural member. A larger texture, the structural member after the artificial aging treatment has a 0.2% proof stress of 220 MPa or more, and a crushing characteristic that gives a bending angle of 80 ° or more in the VDA bending test. A method for producing an aluminum alloy structural member, comprising: