JPS61201748A - 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, 1.5-2.5% Si, 0.25-0.85% Mg, 0.05-0.4% Fe, 0.1-1.5% 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 450-560 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 500-570 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 a strength of 8. In particular, since baking coating is applied, the strength after baking coating is required to be high.

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

(a) 5052, which is a non-heat treated AQ-Mll alloy
Alloy (MO12~2.8%, Qj 0.15~0°35
%, the remainder Q and unavoidable impurities) of O material or the same <5182 alloy (un 0.20-0.50%, Ml
ll, 0 to 5.0%, balance to g and unavoidable impurity O material.

(b) Heat treatment type At! -2036 alloy which is a Cu-based alloy (Cu 2.2-3.0%) 4110.1-0.4
%, 190.3-0.6%, balance AQ and unavoidable impurities) T4 treated material.

(c) Heat treatment type A! ! -Mll -T4 treated material of Zn-Cu based alloy. As this type of aluminum alloy,
For example, the alloy of JP-A-52-141409, JP-A-53
-103914 alloy or JP-A-57-986
There are alloys such as No. 48.

(d) Heat treatment type ^Q -kA (1-Si alloy 6
009 alloy (M20.4~0.8%, 9i 0.6~1
．． 0%, Ca Qj5-0.6%, Mn0.2-0.8
%, remainder Δg and unavoidable impurities) of T4 treated material and the same <60'IO alloy (&J90.6~1.0%,
Si0.8-1.2%, CII 0915-0.6%,
T4 treated material with Mn 0.2-0.8%, remainder (e and unavoidable impurities).

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) does not have sufficient formability, especially bendability, and there is also the problem that the strength decreases during the paint baking process. In addition, for the alloy of the (2) system, for example, 600
9 alloy had insufficient strength, while 6010 alloy had insufficient elongation and bendability.

Problems to be Solved by the Invention As mentioned above, conventional aluminum alloys have the characteristics required for automobile body sheets, namely immersion 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 of the first invention is 9i
More than 1.5% (weight %, same below) and less than 2.5%,
Mll 0.25% or more and 0.85% or less, Fe 0.0
Contains 5% or more and 0.4% or less, CuO 01% or more and 1.5% or less, roughly Mn 0.05% or more and 0.6% or less, Q
j Contains one or more selected from 0.05% to 0.3%, l, 0.05% to 0.15%, and the remainder consists of Al and inevitable impurities. By using such a specific component system, it has excellent strength and moldability, and especially has high strength after baking painting. 11! We were able to realize a rolled aluminum alloy plate suitable for forming into car body seats and the like.

The method of the second invention is a method for producing an aluminum alloy rolled plate for forming work having the excellent properties as described above, and the method is a method for manufacturing an aluminum alloy ingot containing the same components as described above. After homogenizing at a temperature of 1 to 48 hours and then rolling to the required thickness, 500
Hold the temperature within the range ~570°C for more than 20 seconds, followed by rapid cooling! It is characterized by being aged at high temperatures.

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 MO to produce Mt12Si and imparting strength through precipitation hardening, and at the same time is effective in improving formability, particularly elongation. If Si is less than 1.5%, sufficient strength cannot be obtained, and the formability is lower than that of S.
When i exceeds 145%, the improvement increases as the Si content exceeds the stoichiometric ratio of IJ92Si, but when Si exceeds 2.5%, the effect of improving formability becomes saturated, and on the contrary tends to decrease. show. Therefore, the Si content was set within a range of more than 1.5% and less than 2.5%.

■: As already mentioned, MO coexists with Si! jl12
si is generated to impart strength. If the MO content is less than 0.25%, the strength will be insufficient, while if it exceeds 0.85%, the elongation will decrease, so the MO content is set within the range of 0.25 to 0.85%.

Fe: Fe tends to improve strength through refinement of crystal grains, but
If it is less than 0.05%, the crystal grains become coarse, and if it exceeds -1,000G and 4%, the formability decreases, 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 1%, the effect will not be sufficiently obtained, and -1.5%
If it exceeds this, the strength will improve but the moldability will decrease, so it was set within the range of 0.1 to 1.5%.

Mn, Cr, Zr: All of these elements make recrystallized grains finer, stabilize the structure, and improve formability. Mll is less than 0.05%, Cr is less than 0.05%, h is 0.05
%, the above effect cannot be obtained, while un is 0.6%.
If the value exceeds 0.3%, the moldability will decrease, and if the
．． If it exceeds 15%, giant intermetallic compounds are formed and the elongation decreases, so Ml+ is 0.05 to 0.6%, Cr is 0.05 to 0.3%, and Zr is 0.05 to 0.15%. It was set within the range of %.

The remainder of each of the above components may be Δg and unavoidable impurities. Note that in ordinary aluminum alloys, TiN or Ti and B are sometimes added in small amounts to refine the ingot crystal grains, and the rolled aluminum alloy sheet of the present invention also contains trace amounts of Ti, Ti, and B. It may contain. However, when adding Ti, it is 0.01
If it is less than 0.15%, the effect cannot be obtained, and if it is more than 0.15%, primary Ti AQ 3 will crystallize and impair the formability.
is preferably within the range of 0.01 to 0.15%. In addition, when adding B together with Ti, if it is less than 11)I), there is no effect, and if it exceeds 500 ppm, Ti
8 is 1 because the coarse particles of B2 are mixed in and impairs the moldability.
It is preferably within the range of ~500 Ill) Im.

As shown in the examples below, the aluminum alloy rolled sheet with the above-mentioned composition has excellent formability such as elongation, stretchability, and bendability, does not generate Luders marks during forming, and has excellent strength. 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, that is, the 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 cast using a continuous casting method or semi-I! according to a conventional method. Produced by continuous casting method or ingot forming 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 560°C, there is a risk of eutectic melting. Further, if the heating time for homogenization treatment is less than 1 hour, there is no effect, while if heating for a long time exceeding 48 hours, the effect of homogenization treatment will not be increased any further, and the cost will only increase unnecessarily. Therefore, the homogenization process is 450
It was decided to carry out the test in a temperature range of -560°C for 1 to 48 hours.

After the homogenization treatment, the i-border 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'C, the solution treatment will be insufficient and sufficient strength will not be obtained;
If the temperature exceeds .degree. C., there is a risk of eutectic melting, so the solution treatment temperature was set at 500 to 570.degree. 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 10
A cooling rate of 00° C./min or higher is appropriate. Although water quenching is excessive from the standpoint of cooling rate alone, forced air cooling allows quenching without distortion. Note that the degree of turbidity during heating up 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] Inventive alloys with alloy numbers 1 to 7 and comparative alloys with alloy numbers 8 to 12 having the compositions shown in Table 1 were melted and continuously cast according to a conventional method. The obtained ingots were subjected to the homogenization treatment shown in Table 2. Then 41m1! l
The bond was hot-rolled to a thickness of 1.0Ill, cold-rolled to a thickness of 1.0Ill, subjected to solution treatment or final annealing as shown in the column of final heat treatment in Table 2, and left in a room for two weeks. 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 examine the change in strength due to the paint baking process after the room-temperature aging, the plate was subjected to 5% cold working or 10% cold working corresponding to the forming process, and was further subjected to the paint baking process. 175"CX1 hour heat treatment,
The strength at each stage was examined 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 there is no Lüders mark, indicating that the moldability is maintained. 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 ka/- or more can be obtained.

[Execution V142] Continuation as in Example 1 for the present invention alloys 1 to 7 in Table 1! I3i! [, Homogenization treatment, hot rolling and cold rolling were performed to obtain a cold rolled plate having a thickness of 1.0Illl. The cold-rolled sheet is subjected to rapid heating for solution treatment and quenching.
After holding at 40°C for 60 seconds, forced air cooling was performed at a cooling rate of 1200°C/'-. Table 5 shows the results of examining the mechanical properties and moldability after the lft was kept at room temperature for two weeks and aged at room temperature.

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

Effects of the Invention As is clear from the above examples, the aluminum alloy rolled sheet for forming of the present invention has excellent formability, such as excellent stretchability and bendability, and no Lüders marks. In addition, the strength is sufficient, and especially when baking is performed after molding, the strength increases in the baking process, making it possible to obtain baked-coated molded products with extremely high strength in terms of I & Hiiragi. It is ideal for use in high-strength molded products that are baked and painted, such as Auto II car body sheets. The aluminum alloy rolled plate of the present invention contains only S;, &Jg, which are most widely used in ordinary rolled plates, extruded materials, castings, etc., and a trace amount of Cu as main elements, so it does not contain other elements. It is easy to use scraps of alloys, and conversely, it is also easy to use scraps of rolled plates of this invention for other alloys and materials, and scrap processing is good and economical. It's advantageous.

The aluminum alloy rolled sheet of the present invention is ideal for body sheets of automobile bodies as mentioned above, but it can also be used for other applications where strength is required, such as wheels, oil tanks, air cleaners, etc. Auto parts,
It goes without saying that it can also exhibit excellent performance when used in various caps, blinds, aluminum cans, household utensils, instrument covers, chassis of electric appliances, and the like.

Table 2: Heat treatment conditions

Claims (2)

[Claims] (1) Si exceeding 1.5% (weight%, same hereinafter) and 2.5
% or less, Mg 0.25% or more and 0.85% or less, Fe0.
Contains 0.05% or more and 0.4% or less, Cu 0.1% 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 1.5% (weight%, same hereinafter) and 2.5
% or less, Mg 0.25% or more and 0.85% or less, Fe0.
Contains 0.05% or more and 0.4% or less, Cu 0.1% 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 homogenized at a temperature of 450 to 560°C for 1 to 48 hours, then rolled to the required thickness, held at a temperature in the range of 500 to 570°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.