JPS61201749A - Rolled aluminum alloy sheet for forming and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a rolled Al alloy sheet excelling in strength and formability, causing no deterioration in strength after baking finish, and suitable for use in automobile body seats by subjecting an Al alloy ingot having a specific composition to homogenizing treatment, to rolling to prescribed thickness, and to heat treatment under specific conditions. CONSTITUTION:The Al alloy ingot containing, by weight, 1.2-1.5% Si, 0.25-0.85% Mg, 0.05-0.4% Fe, 0.3-1.5% Cu, and further 1 or >=2 kinds among 0.05-0.6% Mn, 0.05-0.3% Cr, and 0.05-0.15% Zr is cast. The ingot is heated at 450-580 deg.C for 1-48hr to be homogenized and is then subjected to hot rolling or further to cold rolling to be rolled into a sheet with prescribed thickness. The sheet is maintained in a temp. range of 500-580 deg.C for >=20sec, cooled rapidly at >=1,000 deg.C/min cooling rate and then subjected to ageing by an ordinary method.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a rolled aluminum alloy plate for forming processing and a method for manufacturing the same, and particularly for applications that require high strength and are used with baking coating, such as automobile bodies. The present invention relates to an aluminum alloy rolled plate suitable for forming and a method for manufacturing the same.

BACKGROUND OF THE INVENTION Conventionally, cold-rolled steel sheets have been mainly used for body sheets of automobile bodies, but recently, due to the demand for lighter vehicle bodies, consideration has been given to using rolled aluminum alloy sheets. Since body sheets for automobile bodies are used after being press-formed, they are required to have excellent moldability, especially excellent elongation and extrusion properties, and no Lüders mark during molding. Moreover, it is also essential to have strength, and in particular, since baking coating is applied, high strength after baking coating is required.

By the way, there have been various types of aluminum alloy plates used for forming products that require strength, but the main ones can be divided into alloys as follows, depending on their composition.

(a) To non-heat treatment type 〇 -5052 alloy which is MO type alloy (Ml 2.2~2.8%, Or 0.15~0.3
0 material or the same <5182 alloy (MnO620-0,50%, yg
i, o~5.0%, balance ^g and unavoidable impurities).

(b) To heat treatment type - 2036 alloy which is a Cu-based alloy (Cu 2.2-3.0%, Mn 0.1-0.4%, M
l0.3-0.6%, balance ^Q and unavoidable impurities)
T4 treated material.

(c) T4-treated material of heat-treated ^fl-Ml-Zn-Cu-based alloy. Examples of this type of aluminum alloy include the alloy of JP-A-52-141409, the alloy of JP-A-53-141409,
Alloy No. 103914 or JP-A-57-9864
There are No. 8 alloys.

(d) 6009 alloy (MOo, 4-0.8%, Si0.6-1
．． 0%, CII 0.15-0.6%, Mn0.2-0
．． 8%, the remainder containing Q and unavoidable impurities) and the same <6010 alloy (Mg0.6-1.0%, Si0
．． 8-1.2%, Cu 0.15-0.6%, Mn 0.
2-0.8%, balance M and unavoidable impurities) T4 treated material.

However, with these conventional aluminum alloys, it has been difficult to fully satisfy all of the above-mentioned characteristics required for body sheets of automobile bodies.

That is, the alloy (a) has insufficient strength, has the problem of easily generating Lüders marks during molding, and further has the problem of reduced strength due to the paint baking process. In addition, the alloy described above has poor formability and also has the problem of reduced strength due to the paint baking process. Furthermore, the alloy (c) has a problem in that the formability, especially the bendability, is not sufficient, and the strength decreases during the paint baking process. In addition, for the alloy of the (2) system, for example, 6009
In the case of alloys, the strength is insufficient, while 60106010
The alloy had insufficient bendability.

Problems to be Solved by the Invention As mentioned above, conventional aluminum alloys have the characteristics required for automobile body sheets, that is, excellent formability, especially excellent elongation and stretch formability, and the Lüders mark. It has been difficult to fully satisfy the following requirements: no occurrence of blemishes, and high strength, especially after paint baking.

This invention was made against the background of the above-mentioned circumstances, and has excellent moldability, especially elongation and stretchability, no Lüders marks during molding, and high strength, especially after molding. To provide an aluminum alloy rolled sheet and a method for producing the same, in which a molded product having high strength is obtained by not reducing strength in a paint baking process, but rather increasing the strength in a paint baking process after forming. The purpose is to

Means for Solving the Problems The aluminum alloy rolled plate for forming processing of the first invention is made of Si
More than 1.2% (!Amount%, same below) and less than 1.5%,
Mll 0.25% or more and 0.85% or less, Fe o, o
Contains s% or more and 0.4% or less, Cu 0.3% or more and 1.5% or less, roughly un o, os% or more and 0.6% or less, Or 0.05% or more and 0.3% or less, z"0.05%
It is characterized by containing one or more selected from the above 0.15% or less, with the remainder consisting of 8g and unavoidable impurities, and such a specific component system and - By doing so, it was possible to realize an aluminum alloy rolled sheet for forming, which has excellent strength and formability, and is suitable for forming automobile body sheets, etc., which has particularly high strength after baking painting.

The method of the second invention is a method for manufacturing an aluminum alloy rolled plate for forming processing having the excellent properties as described above, and the method is a method for manufacturing an aluminum base ingot containing the same components as described above. Homogenized at a temperature of 580°C for 1 to 48 hours, then rolled to the required thickness, 500°C
It is characterized by being maintained at a temperature within the range of ~580°C for 20 seconds or more, followed by rapid cooling and aging in a room.

Function First, the reason for limiting the components in the aluminum alloy rolled plate of the present invention will be explained.

Si: Si is effective in coexisting with Mll to form -1129i and imparting strength through precipitation hardening, and at the same time is effective in improving formability, particularly elongation. The lower limit of Sl is determined from the viewpoint of strength, but in the case of this invention, 0.3% or more of Cu, which is effective in improving strength, is added, so if Si exceeds 1.2%, the required strength can be obtained. On the other hand, if the Si content exceeds 1.5%, no further improvement in strength can be expected, so the Si content is set to be in the range of more than 1.2% and less than 1□5%.

As already mentioned, νg=10 is kJI12 due to coexistence with Si.
si is generated to impart strength. If M9 is less than 0.25%, the strength will be insufficient, while if it exceeds 0.85%, elongation will decrease, so it is set within the range of 0.25 to 0.85%.

Fe: "e contributes to improving strength through refinement of crystal grains, but
If it is less than 0.05%, the crystal grains will become coarse, while if it exceeds 0.4%, the formability will deteriorate, so it was set within the range of 0.05 to 0.4%.

Cu: Cu improves strength and formability, especially bendability, but 0.
If it is less than 3%, the strength improvement effect is not sufficient;
If it exceeds 0.3%, the strength will improve but the moldability will decrease, so it was set within the range of 0.3 to 1.5%.

Mn, Or, 2r: All elements of cholera make recrystallized grains finer, stabilize the structure, and improve formability. un is 0
．． 0.05%, Or is less than 0.05%, 2" is 0.OS
%, the above effect cannot be obtained, while un is 0.6%.
If the value exceeds 0.003%, the moldability decreases, and if the value of C exceeds 0.03%, k becomes 0.003%.
If it exceeds 15%, giant intermetallic compounds are formed and the elongation decreases, so Mn is 0.05-0.6% and Or is 0.05%.
05 to 0.3%, and Zr was within the range of 0.05 to 0.15%.

The remainder of each of the above components may be ^Q and unavoidable impurities. Note that in ordinary aluminum alloys, small amounts of Ti, hair, and B are sometimes added to refine the ingot crystal grains, and the rolled aluminum alloy plate of the present invention also contains a small amount of Ti, or Ti and B. It may contain. However, when adding Ti, if it is less than 0.01%, the effect cannot be obtained, and if it is more than 0.15%, the primary crystal Ti
Since AN 3 crystallizes and impairs formability, Ti should be 0.
It is preferably within the range of 0.01 to 0.15%. Furthermore, when adding 8 along with Ti, 11) l) there is no effect if it is less than 1 m, and if it exceeds 5 o ppm, Tr
Since coarse particles of 82 are mixed in and impair the moldability, B is 1.
It is preferably within the range of ~500 ppIl.

The aluminum alloy rolled sheet having the above-mentioned composition has excellent formability such as elongation, stretchability, bendability, etc., and does not generate Luders marks during forming, and has excellent strength, as shown in the examples below. is also sufficient. In particular, not only is there no decrease in strength in the baking step after molding, but the strength is increased in the baking step, and as a result, it is possible to obtain baked-coated molded products with high strength.

Next, the second invention of the present application, a method for manufacturing a rolled aluminum alloy plate, will be explained along with the reasons for limiting each process condition.

First, an aluminum alloy ingot having the above-mentioned composition is prepared by a continuous casting method, a semi-continuous casting method, or an ingot forming method according to a conventional method.

Next, the ingot is subjected to a homogenization treatment to improve formability and to make the crystal grains fine and uniform. If the heating temperature for this homogenization treatment is less than 450°C, the effect will not be sufficiently obtained, while if it exceeds 580°C, there is a risk of eutectic melting. Furthermore, if the heating time for homogenization treatment is less than one hour, there is no effect, and on the other hand, heating for more than 48 hours will not further increase the effect of homogenization treatment and will only lead to an unnecessary increase in costs. . Therefore, the homogenization process is 450
The test was carried out in a humidity range of ~580°C for 1 to 48 hours.

The ingot after the homogenization treatment is rolled according to a conventional method to obtain the required thickness. This rolling may be performed only by hot rolling, or may be a combination of hot rolling and cold rolling.

After rolling, the plate is subjected to solution treatment and rapidly cooled (quenched). If the solution treatment temperature is less than 500℃, the solution treatment will be insufficient and sufficient strength will not be obtained;
If the temperature exceeds this temperature, there is a risk of eutectic melting, so the solution treatment temperature was set at 500 to 580°C. Further, if the holding time at the solution treatment temperature is less than 20 seconds, the solution treatment may not be completed, so it is necessary to hold the temperature for 20 seconds or more, but preferably for 1 minute or more. Rapid cooling (quenching) after solution treatment temperature maintenance is sufficient if the cooling rate is higher than forced air cooling, specifically 100
A cooling rate of 0°C/lllllg is suitable. Although water quenching is appropriate from the standpoint of cooling rate alone, forced air cooling allows quenching without distortion. Note that the rate of heating to the solution treatment temperature is not particularly limited, but in order to make the crystal grains finer, rapid heating is preferable, and therefore a rapid continuous heat treatment furnace can be used.

After performing the solution treatment and quenching as described above, conventional aging may be performed according to a conventional method.

When actually using the aluminum alloy rolled sheet obtained in this way, it is usual to perform forming processes such as press working, but as already mentioned, the formability is good and the Lüders mark does not occur. Therefore, there is extremely little risk of producing defective products during molding, resulting in high yield and good productivity. In addition, when baking paint is applied after molding, the paint is usually baked at a temperature of 150 to 250°C, although this varies depending on the paint.As mentioned above, this paint baking process further increases the strength of the final product. It is possible to obtain high-strength baking-painted molded products.

Examples [Example 1] The alloys of the present invention with alloy numbers 1 to 5 and comparative alloys with alloy numbers 6 to 10 having the compositions shown in Table 1 were clarified and continuously cast according to a conventional method. The obtained ingots were subjected to the homogenization treatment shown in Table 2. Then, it was hot rolled to a thickness of 4mm, then cold rolled to a thickness of 1.0mm, subjected to solution treatment or final annealing as shown in the column of final heat treatment in Table 2, and then left at room temperature for two weeks. It was aged at room temperature. Table 3 shows the results of examining the mechanical properties and moldability after aging at room temperature.

In addition, in order to investigate the change in strength due to the TL baking process after the room temperature aging, we applied 5% cold working or 10% cold working corresponding to the forming process, which roughly corresponds to paint baking. 175'C x 1 hour heat treatment,
The strength was examined at each stage for those that had not been cold worked (0% cold worked material), 5% cold worked material, and 10% cold worked material. The results are shown in Table 4.

As is clear from Table 3, all of the alloys 1 to 7 of the present invention have excellent stretchability and bendability, and also have no Lüders marks, indicating that they have excellent moldability. Furthermore, from Table 4, it is clear that the strength of the alloy of the present invention is improved in the paint baking step after forming, and finally baked painted molded products having a high tensile strength of 35 kQ/- or more can be obtained.

[Example 2] Inventive alloys 1 to 5 in Table 1 were subjected to continuous casting, homogenization treatment, hot rolling, and cold rolling in the same manner as in Example 1 to obtain cold rolled sheets with a thickness of 1.0 mm. Ta. For the cold-rolled plate,
Solution treatment - as quenching, rapidly heated to 540 °C for 6
After holding for 0 seconds, forced air cooling was performed at a cooling rate of 1200° C./h. Table 5 shows the results of examining the mechanical properties and moldability after being kept at room temperature for two weeks and aging at room temperature.

From Table 5, it is clear that in the case of the alloy of the present invention, excellent mechanical properties and formability can be obtained even when the solution treatment is performed by forced air cooling.

Effects of the Invention As is clear from the actual droplet examples, the rolled aluminum alloy plate for forming of the present invention has excellent formability, such as excellent stretchability and bendability, and no Lüders marks. Moreover, it has sufficient strength, and especially when baking paint is applied after molding, the strength increases in the paint baking process, and it is possible to finally obtain a baking-painted molded product with extremely high strength.Therefore, it is especially suitable for automobile bodies. It is ideal for use in high-strength molded products such as sheets that are baked and used. The aluminum alloy rolled plate of this invention contains Si, MQ, and a trace amount of C, which are most widely used in ordinary rolled plates, extruded materials, castings, etc., as main elements.
Since it only contains u, it is easy to use scraps of other alloys, and conversely, it is also easy to use scraps of the rolled plate of this invention for other alloys and other uses. It has good scrap disposal properties and is economically advantageous.

The aluminum alloy rolled sheet of the present invention is used as a J1 body sheet for automobile bodies as described above.
Other uses of molded products that require strength, such as automobile parts such as wheels, oil tanks, and air cleaners, various caps and blinds, aluminization, household appliances, instrument covers, chassis of electrical equipment, etc. Of course, it is possible to exhibit inferior performance even if the

Table 2: Heat treatment conditions

Claims (2)

[Claims] (1) Si exceeding 1.2% (weight%, same hereinafter) and 1.5
% or less, Mg 0.25% or more and 0.85% or less, Fe0.
Contains 0.05% or more and 0.4% or less, Cu 0.3% or more and 1.5% or less, and Mn 0.05% or more and 0.6% or less,
It is characterized by containing one or more selected from 0.05% to 0.3% of Cr and 0.05% to 0.15% of Zr, with the remainder consisting of Al and inevitable impurities. Aluminum alloy rolled plate for forming processing. (2) Si exceeding 1.2% (weight%, same hereinafter) and 1.5
% or less, Mg 0.25% or more and 0.85% or less, Fe0.
Contains 0.05% or more and 0.4% or less, Cu 0.3% or more and 1.5% or less, and Mn 0.05% or more and 0.6% or less,
Aluminum alloy ingot containing one or more selected from 0.05% to 0.3% of Cr, 0.05% to 0.15% of Zr, and the balance consisting of Al and inevitable impurities. The material is subjected to homogenization treatment at a temperature of 450 to 580°C for 1 to 48 hours, then rolled to the required thickness, held at a temperature in the range of 500 to 580°C for 20 seconds or more, and then rapidly cooled. A method for producing an aluminum alloy rolled sheet, which comprises aging at room temperature.