JPS62207851A - Rolled aluminum alloy sheet for forming and its production - Google Patents

Abstract

PURPOSE:To provide a rolled Al alloy sheet for forming which is superior in formability, and above all, elongating, bending and flanging properties to the conventional sheet by incorporating respectively prescribed ratios of Si and Mg therein and specifying the max. size of an intermetallic compd. in the matrix to a specific value or below. CONSTITUTION:The melt of the Al alloy contg. by wt%, 0.4%n2.5% Si and 0.1-1.2% Mg is continuously supplied between a pair of rolls cooled from the inside and the sheet solidified to 3-15mm thickness is continuously cast. The solidifying rate in this casting stage is required to be high and the cooling rate thereof is kept at >=100 deg.C/sec. The casting sheet is the subjected to a homogenization treatment at 450-600 deg.C at need, then to cold rolling down to a required thickness. The cold rolled sheet is subjected to a soln. heat treatment and hardening by the conventional method by which the objective rolled Al alloy sheet for forming having <=5mum max. size of the intermetallic compd. in the matrix is obtd.

Description

[Detailed Description of the Invention] Industrial Application Field This invention is applicable to automobile body seats, air cleaners,
High strength and excellent moldability, such as oil tanks, etc.
In particular, the present invention relates to an aluminum composite rolled plate used for molded products that require elongation, stretchability, and bendability, and a method for manufacturing the same.

Conventional technology Conventionally, cold-rolled steel sheets have been widely used as automobile plate materials for forming automobile body sheets, etc., but recently, with the aim of reducing the weight of automobile bodies and improving their fuel efficiency, conventional There is a growing demand for aluminum alloy rolled plates to be used instead of cold rolled steel plates.

Conventionally, aluminum alloy rolled sheets used for such purposes include Al-MCJ-based 5052 alloy 0 material and 51
82 alloy O material or Al-Cu based 2036 alloy T
Al-Mc+-3i based 6009 alloy T alloy material, 6010 alloy T alloy material, etc. are used for alloy material and roughness.

Problems to be Solved by the Invention The conventional rolled aluminum alloy sheets as described above are inferior to cold rolled steel sheets in formability, particularly elongation, bendability, and stretchability.

That is, among the A2 alloys mentioned above, Al-Mq alloys such as 5052 alloy and 5182 alloy have relatively good formability, and also have good corrosion resistance.
The O materials of these Af-MQ alloys have the disadvantage that Lüders marks are generated during molding, which may lead to poor appearance, and the strength decreases after baking. One way to prevent the occurrence of Lüders marks in these Al-MO alloys is to apply slight processing distortion through leveling, etc., but this has the problem of reducing formability. Yes, and the problem of strength reduction after baking painting is not resolved. Ai'-CU-Mg alloys such as Zara 2036 alloy have excellent strength and do not produce Lüders marks during forming, but they have poor formability and insufficient strength after baking the paint. There is also the problem of poor corrosion resistance. On the other hand 6010601
0 Alloy 2-1'V1g-9i series alloy has excellent strength, does not generate Lüders marks during molding, has excellent corrosion resistance, and has sufficient strength after baking painting, but has the only drawback. The reason for this is that the molding processability is slightly inferior.

As described above, among the conventional Al alloys, the 6000 series Al-Mq-3i series has the most excellent properties. Therefore, if the only drawback of Al-MCJ-8i alloy, which is that it has slightly poor formability, especially elongation, bendability, and extrusion properties, could be solved, it would be extremely useful as a material for use in automobile body sheets, etc. Excellent Al
It becomes possible to provide rolled alloy plates.

This invention was made against the background of the above circumstances, and
We have improved the formability of the l-Mg-8i alloy, especially its elongation, bendability, and stretchability, resulting in excellent strength, formability, no Lüders mark, and corrosion-resistant strength after baking. The purpose is to provide an Al alloy rolled plate.

Means for Solving the Problems As a result of repeated experiments and studies on methods for improving the formability, especially the elongation, bendability, and stretchability of Al-V+G-Si alloy rolled sheets, the inventors found that the final rolling The maximum size of intermetallic compounds in boards is increasing to 5 units or less,
It has been found that this is effective in improving bendability and stretchability.

In order to reduce the maximum size of intermetallic compounds in the final rolled sheet to 5 νm or less, it is effective to directly and continuously cast the molten alloy into a sheet with a thickness of 3 to 15 m at the casting stage. They discovered this and came up with this invention.

Specifically, the aluminum alloy rolled plate of the first invention of the present application contains 0.4 to 2.5% of 3i, 1 to 1.2% of Mgo, and the balance consists of Al and inevitable impurities,
Moreover, the maximum size of intermetallic compounds in the matrix is 5
It is characterized by being less than or equal to νm.

Further, the aluminum alloy rolled plate of the second invention has Si0.4
~2.5%, M (Jo, containing 1-1.2%, ka')
Cu 1.5% or less, Zn 2.5% or less, Cr 0.3%
The matrix contains one or more selected from 0.6% or less of Mn and 0.3% or less of Zr, and the remainder consists of Al and unavoidable impurities, and the maximum size of the intermetallic compound in the matrix is It is characterized by a thickness of 5 μm or less.

The method for producing rolled aluminum alloy plate according to the third invention is as follows:
A molten aluminum alloy containing 0.4 to 2.5% of 3i and 10.1 to 1.2% of MC, with the balance consisting of Al and inevitable impurities, is continuously cast into a plate with a thickness of 3 to 15 seconds, and then It is characterized by cold rolling, followed by solution treatment and quenching.

Further, the method for manufacturing an aluminum alloy rolled plate according to the fourth invention includes:
Contains 0.4-2.5% of 3i, 1-1.2% of MCJo, and 1.5% or less of Cu, 2.5% or less of Zn, Or
A molten aluminum alloy containing one or more selected from O, 3% or less, Mno, 6% or less, and Zr 0.3% or less, with the remainder consisting of Aj2 and inevitable impurities, is It is characterized by continuous casting into plates of 3 to 15 shoes, followed by cold rolling, followed by solution treatment and quenching.

Function First, the reason for limiting the basic alloy components in this invention will be explained.

Mq: MCI is an essential alloy component in the aluminum alloy of the present invention, and is an element that necessarily contributes to strength and formability. If the MCI is less than 0.1%, the strength will be insufficient and it will be unsuitable for use as automobile body sheets, etc.
If g exceeds 1.2%, ductility and formability will decrease, so it is limited to a range of 0.1 to 1.2%.

Si: Si is also an essential alloy component in the aluminum alloy of the present invention, and is an element that contributes to improving strength and formability. If 3i is less than 0.4%, the strength will be insufficient, while if it exceeds 2.5%, the fluidity of the molten metal will decrease, making continuous casting difficult. Therefore, 3i was limited to a range of 0.4 to 2.5%.

Furthermore, in the second invention of the present application, Cu, Zn, Mn,
It is assumed that one or more of Cr and Zr is added. The reasons for these additions and limitations are as follows.

Cu17n: By adding these, the strength can be further improved. When Cu exceeds 1.5% and zn exceeds 2.5%, corrosion resistance decreases and continuous casting becomes difficult, and especially when CU exceeds 1.5%, formability decreases. Therefore, the upper limit of CU is 1.5%,
The upper limit of zn was set to 2.5%. Note that the lower limit of CLJSzn is not particularly specified, but Cu is less than 0.05% and zn is 0.
．． If it is less than 1%, the effect of adding Cu1zn cannot be sufficiently obtained, so it is preferable to add Cu in an amount of 0.05% or more and zn in an amount of 0.1% or more.

Cr, Mn, zr: These elements all contribute to making the recrystallized grains finer, making the structure more uniform, and improving the strength. M
If n exceeds 0.6%, formability decreases, and Cr, z
If r exceeds 0.3%, coarse intermetallic compounds will be formed. Therefore, the upper limit of Mn is 0.6%, Cr
The upper limit of 1Zr was set at 0.3%. Furthermore, Mn,
The lower limits of Cr and Zr are not particularly specified, but Mn is 0.0
If the content of Or and zr is less than 5%, and if each of Or and zr is less than 0.03%, the effects of these additions cannot be obtained sufficiently, so Mn is 0.0.
It is preferable to add 5% or more, and each of Cr and zr to add 0.03% or more.

In addition to the above-mentioned elements, ordinary aluminum alloys contain Fe as an inevitable impurity.

Although Fe is not a particularly important element in this invention,
If Fe is contained in an amount exceeding 0.5%, the amount of crystallized substances will increase and the moldability will be deteriorated, so it is preferable that Fe is contained in an amount of 0.5% or less.

In addition to the above-mentioned elements, T1 or Ti and B may be added to refine the ingot crystal grains. However, in order to prevent the crystallization of primary TiAl3 particles, Ti should be 0.
．． It is desirable that it be 15% or less, and T i B2
In order to prevent the generation of particles, it is preferable that B be at most 0.0% or less.゛It is important that the rolled aluminum alloy sheets of the first and second inventions of the present application not only have the above-mentioned composition, but also that the maximum size of intermetallic compounds on the rolled surface of the final rolled sheet is 5 μm or less. It is. By regulating the maximum size of intermetallic compounds to 5 μm or less, it is possible to improve formability, especially bendability, elongation,
The overhang property can be improved.

If the maximum size of the intermetallic compound exceeds 5 units, the effects described in (a) above cannot be obtained. In order to reduce the size of intermetallic compounds in the final rolled sheet, as described below, the sheet thickness is 3 to 30% by continuous casting at the casting stage.
It is preferred to cast directly into a 15 m plate to increase the solidification rate.

Next, a method for manufacturing an aluminum alloy rolled plate as described above,
That is, the third invention and the fourth invention of the present application will be explained.

In this manufacturing method, first of all, in order to cast a molten aluminum alloy having the above-mentioned composition,
It is important to continuously cast plates with a thickness of 3 to 15 m.

The specific method is to continuously feed the molten alloy between a pair of rolls that are cooled from the inside, and then continuously rotate the rolls to continuously draw out the solidified plate to a thickness of 3 to 15 m. It is preferable to apply A high solidification rate can be obtained by direct continuous casting into thin plates in this manner.

As already mentioned, in order to keep the maximum size of the intermetallic compound formed on the rolled surface of the final rolled sheet to 5 μm or less, it is necessary to have a high solidification rate during casting. It has been found through experiments by the present inventors that it is necessary to have a dendrite arm spacing of 10 μm or less on average during casting, and a plate thickness of 3 to 1
It is possible to satisfy these conditions by directly continuous casting on the 5-piece plate. Here, the thickness of the cast plate is 3IrI! If it is less than ri, casting itself becomes difficult,
On the other hand, if the length exceeds 15 m, it becomes difficult to keep the dendrite arm spacing to 10 νm or less on average, and it becomes difficult to suppress the maximum size of intermetallic compounds in the final rolled sheet to 5 μm or less, making it difficult to achieve the desired formability, especially It becomes impossible to obtain proper elongation, bendability, and stretchability.

The plate continuously cast as described above is subjected to homogenization treatment at 450 to 600° C. if necessary, and then cold rolled to a required thickness. The rolling rate for this cold rolling may be determined depending on the thickness of the cast plate and the thickness of the product plate, but it is usually preferably about 20% or more.

After cold rolling, solution treatment and quenching are performed.

This solution treatment and quenching may be carried out according to conventional methods. In other words, solution treatment can be carried out by heating to the usual solution treatment temperature for Al-VIQ-81 alloys (about 470 to 600°C), and quenching can be performed at a cooling rate of about 5°C/Sec or more. , forced air cooling, mist quenching, water quenching, etc. may be used. In addition, rapid heating is effective in heating to the solution treatment temperature for grain refinement, and therefore it is preferable to use a continuous heating quenching furnace or a salt bath furnace.

Since the alloy of the present invention is a heat-treated aluminum alloy, the strength gradually increases by being left at a very high temperature after quenching, and the strength is saturated after 3 to 7 days.

Examples Alloys shown in alloy numbers 1 to 6 in Table 1 were continuously cast into plates with a thickness of 6 m by a continuous casting method in which molten alloy was continuously supplied between a pair of cooled rotating rolls. The obtained continuous cast plate was cold rolled to one cocoon.

Similarly, the alloys shown in alloy numbers 1 to 6 in Table 1 were cast into 400 m thick slabs by the DC casting method as a comparative method, and after being homogenized at 530 to 560°C for 10 hours, After starting hot rolling at 500℃ 6
A hot rolled sheet of #EIll was used. The hot-rolled sheet was cold-rolled to obtain an IS sheet.

Each of the cold-rolled sheets of Alloy Nos. 1 to 6 obtained as described above was subjected to solution treatment and quenching under the conditions shown in Table 2. Regarding alloys having the same composition, both cold-rolled sheets subjected to continuous casting (present invention material) and cold-rolled sheets applied DC casting (comparison material) were subjected to solution treatment and quenching under the same conditions.

Table 3 shows the results of investigating the maximum size of intermetallic compounds on the rolled surface of the plates of the present invention material (continuous casting), f3, and comparative material (DC casting) after the heat treatment as described above. Shown below.

In addition, after the heat treatment, each plate was further left for at least one week to age at room temperature, and the mechanical strength (tensile strength, 0.2% proof stress), elongation, Erichsen value, and 180°
Table 3 also shows the results of examining the minimum bending radius in bending and the yield strength after heating at 200'CX for 30 minutes, assuming a paint baking process after aging at room temperature.

Table 1 Table 2: Solution treatment/quenching conditions No. 3
As is clear from Table 3, in the case of the present invention materials obtained by direct casting into 6 m plates by continuous casting, the maximum size of intermetallic compounds in the final plate was 5 μm or less; In this case, the formability was improved compared to a comparative material (maximum intermetallic compound size in the final plate of 12 to 16 μm) obtained by casting a 400 mm thick slab using the DC casting method.

In both cases, 200'CX stipulates paint baking.
The yield strength was improved by heating for 30 minutes, which indicates that it has bake hardening ability. In addition, no Lüders mark was observed during the molding process in any case. Therefore, the advantage of the conventional At1-Mg-5i alloy is that it does not generate the Luders marks,
It can be seen that the properties of bake hardening ability are not lost even in the case of the material of the present invention.

Effects of the Invention As is clear from the above examples, the Al-M of this invention
9-s type aluminum alloy rolled plate for forming process is made of conventional Al-MCl-81 type alloy such as 6010 alloy (
6000 series alloy) has excellent formability, especially elongation, bendability, and extensibility, compared to rolled sheets.

In other words, the aluminum alloy plate according to the present invention has the advantages of conventional No. 6000 series alloys, such as excellent strength and corrosion resistance, no Lüders marks, and a high temperature after baking coating. This alloy solves the only drawback of the alloys, which is that the formability is slightly inferior, and combines the above-mentioned various advantages with excellent formability, especially elongation, bendability, and extensibility.

Therefore, the aluminum alloy rolled sheet of the present invention can be suitably used for automobile body sheets which require the above-mentioned characteristics, and can also be used for other formed products, such as wheels and oil. It goes without saying that it can exhibit excellent performance when used in automobile parts such as tanks and air cleaners, various caps and blinds, aluminium, household appliances, instrument covers, chassis of electrical equipment, etc.

Claims (4)

[Claims] (1) Si0.4-2.5% (weight%, same below), M
An aluminum alloy rolled sheet for forming processing, characterized in that the aluminum alloy contains 0.1 to 1.2% of g, the remainder consists of Al and unavoidable impurities, and the maximum size of intermetallic compounds in the matrix is 5 μm or less. . (2) Contains 0.4-2.5% Si, 0.1-1.2% Mg, and 1.5% or less Cu, 2.5% or less Zn, C
Contains one or more selected from r0.3% or less, Mn0.6% or less, and Zr0.3% or less, with the remainder consisting of Al and inevitable impurities, and furthermore, an intermetallic compound in the matrix. An aluminum alloy rolled sheet for forming processing, characterized in that the maximum size of the aluminum alloy is 5 μm or less. (3) Continuous casting of molten aluminum alloy containing 0.4 to 2.5% Si and 0.1 to 1.2% Mg, with the balance consisting of Al and unavoidable impurities, into a plate with a thickness of 3 to 15 mm. A method for manufacturing an aluminum alloy rolled sheet, which comprises cold rolling, followed by solution treatment and quenching. (4) Contains 0.4-2.5% Si, 0.1-1.2% Mg, and 1.5% or less Cu, 2.5% or less Zn, C
A molten aluminum alloy containing one or more selected from r0.3% or less, Mn0.6% or less, and Zr0.3% or less, with the balance consisting of Al and unavoidable impurities, is A method for producing a rolled aluminum alloy plate, which comprises continuous casting into a plate of 3 to 15 mm, followed by cold rolling, followed by solution treatment and quenching.