JP2001254136A - Aluminum alloy sheet for automotive panel inner material, and automotive inner panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet for automotive panel inner material for which the selection range of the raw material is extremely wide, having extremely excellent recycling properties in such a manner that a panel can be produced with the scrap material of a panel as the raw material and excellent in strength and formability at the time of forming a panel, and to provide an automotive inner panel. SOLUTION: This alloy sheet has a composition containing, by mass, 0.7 to 1.5% Mn, 0.7 to 2.0% Mg and 0.2 to 0.6% Si and further containing at least one kind selected from the groups consisting of 0.2 to 0.7% Fe, 0.1 to 0.4% Cu and <=0.3% Cr, and the balance Al with inevitable impurities.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy sheet for an automobile panel inner material and an automobile inner panel used for an inner material of an automobile bonnet, and more particularly to an automobile panel excellent in recyclability (reusability). The present invention relates to an aluminum alloy plate for an inner material and an automobile inner panel.

[0002]

2. Description of the Related Art In recent years, aluminum alloy materials have been employed in structures such as panels constituting automobiles in order to reduce the weight of automobiles in view of improvement of fuel efficiency and the like, and the amount of use thereof has been increasing.

[0003] For example, an automobile bonnet has an outer panel to be baked and a rigid inner panel superposed thereon. FIG. 1 is a front view showing an inner panel 7 used for a hood. In the inner panel 7, a plurality of openings 10 are formed for weight reduction. The runners 8a, 8b, 8c, 9a, 9b are formed between the openings 10.

FIG. 2A is a sectional view showing another inner panel for a bonnet, and FIG. 2B is a front view thereof. In the inner panel 1, a circular recess 4 is formed on the back surface 3.
Are formed. The weight of the inner panel 1 is reduced by providing the recess 4, and there is an advantage that the strength is higher than when the opening 10 is formed as shown in FIG. 1.

[0005] Conventionally, the outer panel is made of Mg during baking.
_{2 In} order to increase strength by precipitation hardening of Si, Al-Si
-Mg-based 6000 series alloy is used (Japanese Patent Laid-Open No.
-31616). Also, since the inner panel needs to be formed into an outer shape of the car while securing rigidity,
From the viewpoint of moldability, an Al-Mg-based 5000-based alloy is used (JP-A-5-271835).

[0006] On the other hand, in addition to reducing the weight of automobiles, recycling of materials is being studied for environmental measures such as energy saving (Japanese Patent Application Laid-Open No. 11-71623). JP 1
In the aluminum alloy plate for an automobile body panel described in 1-71623 and the method of manufacturing the same, a 6000 series panel material manufactured using a scrap material is disclosed.

[0007]

Problems to be Solved by the Invention Japanese Patent Application Laid-Open No. 11-7162
As disclosed in Japanese Unexamined Patent Publication No. 3 (1993), from the viewpoint of recycling, it is also useful to produce a panel using a scrap material. However, this is not enough for recycling. That is, as shown in FIG. 2, when manufacturing a panel or the like, the mold (blank) of the inner panel 7 is used.
After punching out, blemishes come out. After the car is scrapped and dismantled, the panels themselves become scrap material. Therefore, even if these scrap materials are not reused, they cannot be truly recycled.

[0008] However, even if an attempt is made to reuse the scrap material described above, for example, to produce a 5000-series alloy using a 6000-series alloy as a raw material, the 6000-series alloy contains a large amount of Si. Is difficult to use as a raw material. On the other hand, even if an attempt is made to produce a 6000 series alloy using a 5000 series alloy as a raw material, in the 6000 series alloy, the amount of precipitation or the like is controlled by the component or the heat treatment condition in order to obtain necessary properties such as strength. It is extremely difficult to produce a 6000 series alloy using a series alloy as a raw material.

Further, as in the case of manufacturing an AA5182 alloy using a scrap material of the AA5182 alloy as a raw material,
If the raw materials and the materials produced based on the raw materials are of exactly the same kind, 100% recycling is possible. However, even if the alloy system (6000 series or 5000 series, etc.) is the same, the alloy type (AA5023 or AA518)
2), the permissible amounts of elements such as Fe or Si are different, so that it is difficult to recycle using materials of different types as raw materials. In addition, in order to use the same alloy type for the raw material and the product, it is very difficult to confirm the kind of the alloy and separate it for use as a raw material in order to perform industrial production. Therefore, at present, even if scrap materials for panels are produced, there is no use except for using them as raw materials for aluminum or aluminum alloy castings, which are in low demand, and there is a problem in recycling.

The present invention has been made in view of the above problems, and has a very wide range of choices of raw materials, and has extremely excellent recyclability, such as being able to produce panels using scrap materials of panels as raw materials. It is an object of the present invention to provide an aluminum alloy plate for an automobile panel inner material and an automobile inner panel having excellent strength and moldability when molding a panel.

[0011]

According to the present invention, an aluminum alloy plate for an automobile panel inner material according to the present invention comprises Mn: 0.7 to 1.5% by mass, Mg: 0.7 to 2.0% by mass and S
i: 0.2 to 0.6% by mass, and Fe: 0.
2 to 0.7 mass%, Cu: 0.1 to 0.4 mass%, and Cr: at least one selected from the group consisting of 0.3 mass% or less, with the balance being Al and inevitable impurities. Characterized by having a composition consisting of

In this case, the yield strength after baking is 10
The pressure is preferably 0 to 140 MPa.

The automobile inner panel according to the present invention has an M
n: 0.7 to 1.5% by mass, Mg: 0.7 to 2.0
% By mass and Si: 0.2 to 0.6% by mass, Fe: 0.2 to 0.7% by mass, Cu: 0.1 to 0.4% by mass, and Cr: 0.3% by mass. A plurality of cup-shaped recesses are formed by overhanging an aluminum alloy plate containing at least one selected from the group consisting of the following and having a balance of Al and inevitable impurities. Features.

Another automobile inner panel according to the present invention comprises Mn: 0.7 to 1.5% by mass, Mg: 0.7 to 2.0% by mass, and Si: 0.2 to 0.6% by mass. Fe: 0.2 to 0.7% by mass, Cu: 0.1
To 0.4% by mass and Cr: 0.3% by mass or less, and a plurality of aluminum alloy plates having a balance of Al and inevitable impurities formed by stretch forming on the aluminum alloy plate. Cup-shaped recesses are formed, yield strength is 100 to 140MP
It is characterized by having been baked as a.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present application conducted various experimental studies to develop an aluminum alloy for an automobile panel inner material having excellent recyclability, which can be manufactured using a 6000 series or 5000 series scrap material. As a result,
It has been found that an aluminum alloy material having excellent properties as an inner panel material can be obtained by appropriately defining the composition based on the 3000 series aluminum alloy composition.

The inventors of the present application have conducted intensive studies and found that 30
By properly defining the composition of the 00-based aluminum alloy, it has been found that the strength can be improved to satisfy the requirements as an inner material of an automobile structural material, and that the recyclability is excellent.

In the present invention, as a material that can be used as a raw material, a scrap material in the city and a panel generated by dismantling an automobile can be cited. Also, 60
When manufacturing a panel made of a 00-based alloy or a 5000-based alloy and the panel, scraps generated can also be used as a raw material. Further, when a panel made of the alloy according to the present invention and the panel are manufactured, chips generated and the like can be used again as raw materials. Furthermore,
The entire panel is made of, for example, an outer material of 6000 series alloy and 5
In the case of an aluminum alloy material combined with an inner material of a 000 series alloy, it can be used as a raw material without dismantling the panel itself.

Further, using the aluminum alloy plate for an automobile panel inner material of the present invention, an automobile inner panel in which a plurality of cup-shaped recesses are formed on the entire surface by overhang molding can be manufactured.

The overhang forming is a method of forming a plate material into a curved surface or the like while reducing the plate thickness by pulling in two orthogonal directions in the plate surface. Unlike the drawing process, the stretch forming does not cause the material to flow in the drawing direction at the time of forming. Further, when it is desired to improve the strength of the inner material of the panel, it is sufficient to form many concave portions. However, in the drawing process, since the material flows, the molding becomes difficult.
In the overhang forming, even if the number of concave portions increases, no material flows in when forming the concave portions. Therefore, by forming the recesses by overhanging, more recesses can be formed than by drawing, which is preferable from the viewpoint of improving the strength of the panel. Also, by making the recessed part a cup shape,
The load applied to the panel is dispersed and the load does not concentrate. Therefore, strength and rigidity are improved, which is preferable. The automobile inner panel is laminated on the outer panel and formed into a panel, and the outer panel is baked and painted.
At this time, baking is simultaneously performed on the inner panel. Therefore, considering the strength as the panel material and the panel formability, the yield strength of the inner panel after baking is 1
The pressure is preferably set to 00 to 140 MPa.

Hereinafter, the reasons for limiting the numerical values of the aluminum alloy sheet for an inner panel material of an automobile according to the present invention will be described.

Mn: 0.7 to 1.5% by mass Mn affects strength and formability (crystal grain refinement). M
If the content of n is less than 0.7% by mass, the strength and moldability are not sufficiently improved. On the other hand, the content of Mn is 1.5% by mass.
When the ratio exceeds, both the amount and the size of the Al-Fe-Mn-based compound increase, and the moldability deteriorates. For this reason, in the case of forming an inner panel having an opening, drilling performance is deteriorated. Therefore, the content of Mn is set to 0.7 to 1.5% by mass.

Mg: 0.7 to 2.0% by mass Mg affects strength and formability (crystal grain refinement) similarly to Mn. If the Mg content is less than 0.7% by mass, the strength and moldability are not sufficiently improved. On the other hand, when the content of Mg exceeds 2.0% by mass, the effect of improving the strength and the moldability is saturated. In addition, the cost for adding Mg increases. Therefore, the content of Mg is set to 0.7 to 2.0% by mass.

Si: 0.2 to 0.6% by mass Si affects recyclability and moldability. If the Si content is less than 0.2% by mass, the recyclability and moldability are not sufficiently improved. On the other hand, the content of Si is 0.6% by mass.
If it exceeds 100%, the recyclability is improved, but Al-F
It promotes the phase transformation of the e-Mn-based compound, causes a significant increase in the number and size of the compound referred to as the α-phase, and increases the reduction in deep drawability and drilling property. Therefore, the content of Si is 0.2 to 0.6% by mass.

Fe: 0.2 to 0.7 mass%, Cu:
0.1 to 0.4 mass% and Cr: 0.3 mass% or less
At least one type of Fe selected from the group affects recyclability and press formability. Fe
Is less than 0.2% by mass, the effect of improving recyclability and press moldability is not sufficient. On the other hand, Fe
When the content exceeds 0.7% by mass, although the recyclability is improved, the phase transformation of the Al—Fe—Mn-based compound is promoted, and the number and the size of the compound referred to as α phase are significantly increased. , Deep drawability and piercing properties are reduced.

Cu affects strength, recyclability, corrosion resistance and press formability. When the content of Cu is less than 0.1% by mass, both the 5000-type and 6000-type aluminum alloy materials contain Cu, and it becomes difficult to manufacture from these aluminum alloy materials, so that the recyclability is insufficient. It is. On the other hand, when the content of Cu exceeds 0.4% by mass, corrosion resistance is reduced, and press formability is reduced.

Cr affects the recyclability, and the higher the content, the better the recyclability. Cr content of 0.3
If the content is more than mass%, an Al-Mn-Cr-based compound is formed, so that press formability is reduced.

In the present invention, at least one of these elements may be contained. Therefore, Fe: 0.2
To 0.7 mass%, Cu: 0.1 to 0.4 mass%, and Cr: at least one selected from the group consisting of 0.3 mass% or less.

Inevitable impurities In addition to the above components, unavoidable impurities are those contained in ordinary aluminum alloy production steps, such that Ti is less than 0.1% by mass and B is 1000% by mass.
And Zn less than 0.25% by mass.

Yield stress after baking: 100 to 14
After molding into a 0 MPa panel, the outer panel is baked and painted, and at the time of baking, the inner panel is also baked to improve the strength. When the yield stress after baking of the inner panel is less than 100 MPa, the strength of the panel inner material is slightly insufficient. On the other hand, basically, the higher the yield stress, the better, but the yield stress after baking is 140M.
When it exceeds Pa, the yield stress before baking becomes too high, and the moldability when molding the inner panel material is reduced. Therefore, the yield stress after baking is 100 to 14
It is preferably 0 MPa.

[0030]

EXAMPLES Examples of aluminum alloy sheets for automobile panel inner materials which fall within the scope of the present invention will be specifically described below in comparison with comparative examples.

An ingot of an aluminum alloy having the composition shown in Table 1 is subjected to a homogenizing heat treatment at a temperature of 500 to 600 ° C., and subsequently hot-rolled and cold-rolled to a thickness of 1.5 mm.
Was manufactured. Intermediate annealing was performed at a temperature of 350 ° C. during the cold rolling. The remarks column of Table 1 shows alloys corresponding to the examples and the comparative examples. Further, Zn in Table 1 is contained as an impurity.

Table 2 shows the blending ratio (recycling ratio) of the aluminum alloy plates of Examples and Comparative Examples in which a typical aluminum alloy material (outer representative material) used as an outer material is compounded.

The mixing ratio is defined as each element (Si,
(Cu, Mg, Mn, etc.) when the inner material is manufactured. In other words, it indicates the limit usage of scrap material when an aluminum alloy plate is manufactured using the scrap material.

When the composition of the scrap material used as a raw material and the aluminum alloy to be manufactured are compared with each other, the restricted element (hereinafter referred to as the “constrained element”) is more than the aluminum alloy to be manufactured. Is also an element with a large content. That is, since the mixing ratio is calculated by focusing on one element of the aluminum alloy plate whose concentration needs to be reduced by the new metal, the limiting element differs for each scrap material. Therefore, for example, in Example N
The sum of the mixing ratios in the column of o.1 does not add up to 100%. Therefore, the sum of each column is unnecessary. In addition, the shortage of the element can be compensated by newly adding it together with the metal, so that there is no problem. Note that the elements in parentheses shown in each column in Table 2 indicate restriction elements. When there is no element indicated by (), it indicates that there is no restrictive element.

Next, a specific calculation method of the mixing ratio will be described. First, Example N using AA6022 alloy
The case of manufacturing o.1 will be described. In this case, comparing the compositions of the respective alloys, the AA6022 alloy contained more Si than in Example No. 1, and Si was used as a limiting element.
The content of Si in the AA6022 alloy was 1.1% by mass, and the content of Si in Example No. 1 was 0.35% by mass. The ratio of Si of the AA6022 alloy to Example No. 1 was determined to be 0.35 / 1.1, and this ratio was 32%. That is, this ratio becomes the blending ratio. About other deficient other elements (Mn, Mg, Fe, Cu, etc.), 100% can be added to a desired amount by newly adding together with the metal.

Next, a comparative example using AA6022 alloy was used.
The case of manufacturing No. 5 will be described. Comparative Example No. 5 had the same composition as the AA6022 alloy, so the compounding ratio was 1
00%. That is, the AA6022 alloy is
Since it returns to the alloy, it can basically be blended at 100%.

Next, a comparative example using AA6022 alloy
The case of manufacturing No. 7 will be described. In this case, comparing the compositions of the respective alloys, the AA6022 alloy had a higher Mn content than Comparative Example No. 7, and Mn was used as a limiting element. The Mn content of the AA6022 alloy was 0.1% by mass, and Mn was not added in Comparative Example No. 7, and the Mn content was 0% by mass. AA6 for Comparative Example No. 7
The Mn ratio of the 022 alloy is determined as 0 / 0.1, and the blending ratio is 0%. For this reason, even if metal is added, the Mn content cannot be reduced to 0% by mass. Note that Comparative Example No.
No. 7 uses bullion with a purity of 99.9%.

The strength (base sheet strength) of the aluminum alloy sheet having the composition shown in Table 1, the yield strength after processing and baking of the aluminum alloy sheet, press formability, and hole expandability (inner performance) were examined. In addition, about the press formability and the hole expandability, it implemented about the original plate.

The yield strength after working baking is the yield strength measured after pressing each aluminum alloy plate to give a strain of about 2% and performing baking at 170 ° C. for 20 minutes.

The press formability was evaluated by measuring the limit wrinkle pressing force with a large press using a door mold. The evaluation is ◎ when the limit wrinkle holding force is 60 tons or more and ◎ to ○ when the limit wrinkle holding force is 40 tons or more and less than 60 tons, and when the limit wrinkle holding force is 20 to 40 tons or less. Δ, those having a limit wrinkle holding force of less than 20 tons were evaluated as ×.

Regarding the hole expandability, the diameter is D
A disc having holes formed of ₀ to overhang deformed by the punch, when the diameter when crack occurs in the edge of the hole was D _b, burring represented by _{(D b -D 0) / D} 0 The evaluation was made based on the rate (critical hole expansion rate). The evaluation was ◎ when the burring rate was 60% or more, and ◎ to を when the burring rate was 50% or more and less than 60%.
A sample having a burring ratio of less than 40% was evaluated as x and a sample having a burring ratio of less than 40% was evaluated as x. Table 3 shows the results.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

[Table 3]

As shown in Table 3 above, Examples Nos. 1 to 3 had high compounding ratios of the respective outer representative materials, had excellent recyclability, and had good strength, press formability and hole expandability. Was.

On the other hand, in Comparative Example No. 4, since the Si content exceeded the upper limit of the present invention, press formability and hole expandability were poor.

In Comparative Example No. 5, although the compounding ratio of materials having the same alloy composition can be increased, the content of Si exceeds the upper limit of the present invention, and Fe, Cu, Mn and Mg
Is less than the lower limit of the present invention, the proportion of other outer representative materials was low, and the recyclability was poor.

In Comparative Example No. 6, although the compounding ratio of materials having the same alloy composition can be increased, Si and C
Since the content of u exceeded the upper limit of the present invention and the content of Mn and Mg was less than the lower limit of the present invention, the proportion of other outer representative materials was low and the recyclability was poor.

In Comparative Example No. 7, although the blending ratio of materials having the same alloy composition can be increased, the content of Mg exceeds the upper limit of the present invention, and the content of Si and Fe exceeds the upper limit of the present invention. , The mixing ratio of other outer representative materials was low, and the recyclability was poor.

Comparative Example No. 8 shows that although the blending ratio of materials having the same alloy composition can be increased, the content of Mg exceeds the upper limit of the present invention, and the content of Si, Cu and Mn is reduced. Since it is less than the lower limit of the present invention, the compounding ratio of other outer representative materials was low, and the recyclability was poor.

In Comparative Example No. 9, since the Mn content exceeded the upper limit of the present invention, press formability and hole expandability were poor.

In Comparative Example No. 10, since the Mn content was less than the lower limit of the present invention, the yield stress of the base plate was low and the strength was poor. Also, the yield strength after processing baking was low.

In Comparative Example No. 11, since the content of Mg exceeded the upper limit of the present invention, press formability and hole expandability were slightly poor.

In Comparative Example No. 12, since the Mg content was less than the lower limit of the present invention, the yield stress of the base plate was low and the strength was poor. Also, the yield strength after processing baking was low. Furthermore, the blending ratio of the 5000 type outer representative material was low, and the recyclability was poor.

In Comparative Example No. 13, since the Si content was less than the lower limit of the present invention, the press formability was slightly poor.
The yield strength after processing baking was also low. Also, 600
The blending ratio of Type 0 outer representative material was low, and the recyclability was poor.

In Comparative Example No. 14, since the Fe content exceeded the upper limit of the present invention, press formability and hole expandability were poor.

In Comparative Example No. 15, since the Fe content was less than the lower limit of the present invention, the press formability was slightly poor.

In Comparative Example No. 16, since the Cu content exceeded the upper limit of the present invention, press formability and hole expandability were poor.

In Comparative Example No. 17, since the Cu content was less than the lower limit of the present invention, the yield stress of the base plate was low and the strength was poor. Also, the yield strength after processing baking was low. Furthermore, the compounding ratio of the outer representative material was low, and the recyclability was poor.

In Comparative Example No. 18, since the content of Cr exceeded the upper limit of the present invention, press formability and hole expandability were poor.

As described above, when only the performance of the inner member is evaluated, Comparative Examples Nos. 5 and 7 are stable and have excellent performance. However, depending on the car manufacturer and model,
Recycling is difficult in practice because of the different alloy compositions. Therefore, in consideration of future recycling and cost reduction, it is best to apply Examples Nos. 1 to 3 to the inner material. That is, the present invention can improve the recyclability while satisfying the performance as the inner material.

[0062]

As described above in detail, according to the present invention, by appropriately defining the composition of the aluminum alloy sheet,
Since the range of selection of raw materials can be extremely widened while satisfying the performance as a panel such as an inner material, the efficiency of recycling can be improved. As a result, costs can be reduced and a great contribution is made to addressing global environmental issues. In addition, the aluminum alloy plate of the present invention promotes aluminization of automobiles and contributes to solving environmental problems at an early stage.

[Brief description of the drawings]

FIG. 1 is a front view showing an inner panel used for a hood.

FIG. 2A is a sectional view showing another inner panel for a bonnet, and FIG. 2B is a front view thereof.

[Explanation of symbols]

 1, 7; inner panel 2, 2a, 5; front surface 3; back surface 4: concave portion 6; gap 8a, 8b, 8c, 9a, 9b; runner 10;

Claims (4)

[Claims] 1. Mn: 0.7 to 1.5% by mass, Mg:
0.7 to 2.0% by mass and Si: 0.2 to 0.6% by mass, Fe: 0.2 to 0.7% by mass, C
u: at least one selected from the group consisting of 0.1 to 0.4% by mass and Cr: 0.3% by mass or less, with the balance having a composition comprising Al and unavoidable impurities. Aluminum alloy plate for automobile panel inner material. 2. The yield strength after baking is 100 to 1
The aluminum alloy plate for an inner panel material of an automobile according to claim 1, wherein the pressure is 40 MPa. 3. Mn: 0.7 to 1.5 mass%, Mg:
0.7 to 2.0% by mass and Si: 0.2 to 0.6% by mass, Fe: 0.2 to 0.7% by mass, C
an aluminum alloy plate containing at least one selected from the group consisting of u: 0.1 to 0.4% by mass and Cr: 0.3% by mass or less, with the balance being Al and unavoidable impurities An inner panel for an automobile, wherein a plurality of cup-shaped recessed portions are formed by overhanging the base plate. 4. Mn: 0.7 to 1.5% by mass, Mg:
0.7 to 2.0% by mass and Si: 0.2 to 0.6% by mass, Fe: 0.2 to 0.7% by mass, C
an aluminum alloy plate containing at least one selected from the group consisting of u: 0.1 to 0.4% by mass and Cr: 0.3% by mass or less, with the balance being Al and unavoidable impurities A plurality of cup-shaped recesses are formed by overhang forming on the inner panel, and the baking is performed so that the yield strength becomes 100 to 140 MPa.