JPH07310136A - Aluminum alloy sheet for forming and its production - Google Patents

Abstract

PURPOSE:To improve the strength and formability of an aluminum alloy sheet material used as the forming material of an automotive body sheet, a pressure resistant vessel or the like. CONSTITUTION:An aluminum alloy for forming having a compsn. contg., as essential components, by weight, 4.0 to 10.0% Mg, total 0.01 to 0.5% of one or more kinds among Cr, Zr and Mn, in which the contents of Fe and Si as inevitable impurities are respectively regulated to <=0.2%, the content of other impurity elements is all regulated to <=0.05%, and the balance Al, and furthermore contg. 0.1 to 0.5% Cu and having 10 to 25mum average grain size is subjected to casting and hot rolling, is thereafter subjected to 30 to 80% cold rolling and is subjected to process annealing by holding at 300 to 500 deg.C for >=30min. Next, it is subjected to >=20% cold rolling to form into a prescribed sheet thickness and is subjected to annealing treatment by heating to 450 to 550 deg.C, immediately, or within 60sec, holding and cooling to <=100 deg.C at >=10 deg.C/min rate, by which the average grain size is regulated to 10 to 25mum.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is suitable for molding materials such as automobile body sheets, pressure resistant containers, and packaging containers, and has excellent strength.
The present invention relates to an aluminum alloy sheet having ductility and an excellent appearance after forming, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, cold-rolled steel sheets have been mainly used for automobile outer panels. However, recently, the use of an aluminum alloy plate has been studied due to the demand for weight reduction of automobile bodies. Materials for automobile outer panels are required to have excellent press formability and high strength. Al-Mg alloys such as 5052 alloy and 5182 alloy have been often used as materials satisfying such requirements. The above-described 5000 series alloy has a lower ductility than steel and has a defect that it is easily cracked during molding. In order to modify ductility, various additive elements have been studied and impurities have been reduced, but sufficient ductility improvement effects have not been obtained.

[0003]

In view of the above, the present invention has made a detailed study of the characteristics of the materials particularly required for drawing, and as a result, uses a low-viscosity cleaning oil that is widely used for molding automobile body materials. The aluminum alloy plate having optimum characteristics when the strain rate of the punch shoulder portion for allowing the material to flow into the mold is relatively low, and the manufacturing method thereof have been developed.

[0004]

Means for Solving the Problems The present invention contains 4.0 to 10.0 wt% of Mg as an essential component and 0.01 to 0.5 wt% in total of any one or more of Cr, Zr and Mn,
The amount of inevitable impurities Fe and Si is 0.2 wt.
% Or less, 0.05 wt% for all other impurity elements
An aluminum alloy plate for molding which has the composition consisting of the balance Al and has an average crystal grain size of 10 to 25 μm is set forth below, and Mg is used as an essential component.
4.0-10.0 wt%, Cu 0.1-0.5 wt%
And Cr, Zr, or any one or more of Mn, total 0.0
1 to 0.5 wt%, the amount of unavoidable impurities Fe and Si is 0.2 wt% or less, each of the other impurity elements is 0.05 wt% or less, and the balance is Al, and the average crystal An aluminum alloy plate for molding having a particle size of 10 to 25 μm is defined as claim 2, and Mg of 4.0 to 10.0 wt% as an essential component and C
Total of 0.01 or more of any one of r, Zr, and Mn
0.5 wt%, 0.2 wt% or less of Fe and Si as unavoidable impurities, 0.05 wt% or less of all other impurity elements, and aluminum alloy consisting of the balance Al is cast and homogenized by a conventional method. After chemical treatment and hot rolling, 3
0-80% cold rolling, 300-500 ℃ hold for 30 minutes or more intermediate annealing, then 20% or more cold rolling to a predetermined plate thickness, heated to 450-550 ℃ temperature,
Immediately or holding for 60 seconds or less, an annealing treatment of cooling at a rate of 10 ° C./min or more to 100 ° C. or less is performed to obtain an average crystal grain size of 10 to 25 μm. The manufacturing method is defined as claim 3, and Mg 4.0 to 10.0 wt% and Cu as essential components
0.1 to 0.5 wt% and 0.01 to 0.5 wt% in total of any one or more of Cr, Zr, and Mn, and 0.2 wt% or less of the inevitable impurities Fe and Si, respectively.
All the other impurity elements are made 0.05 wt% or less, and the aluminum alloy consisting of the balance Al is cast by a conventional method.
After homogenizing and hot rolling, 30-80% cold rolling, 300
Intermediate annealing is performed by holding at ~ 500 ° C. for 30 minutes or more, and then cold rolling is performed by 20% or more to a predetermined plate thickness.
By heating to a temperature of 550 ° C. to 550 ° C., holding immediately or within 60 seconds, and cooling to 100 ° C. or less at a rate of 10 ° C./min or more, an average crystal grain size of 10
The method for producing a forming aluminum alloy sheet is characterized in that the thickness is 25 μm.

[0005]

In the present invention, the reason why the alloy composition is limited is as follows. When Mg forms a solid solution, it increases the strength and, at the same time, increases the work hardenability to increase the ductility and contributes to the improvement of the formability. In particular, it has a function of remarkably increasing the strength in low-speed molding by increasing the fixing action with dislocations at a low strain rate. The amount added was limited to 4.0 to 10.0 wt% because it was 4.0 wt.
This is because if it is less than 1.0%, the effect is small, and if it exceeds 10.0% by weight, the SSC resistance is deteriorated and the hot workability is deteriorated, and the manufacturing becomes difficult.

[0006] Cr, Zr and Mn are precipitated as fine dispersed particles during soaking, hot rolling and intermediate annealing to make the crystal grains finer and contribute to the improvement of strength at a low strain rate as described later. The total amount of these added is set to 0.01 to 0.5 wt% because if the amount is less than 0.01 wt%, the grain refining effect is not sufficient, and if it exceeds 0.5 wt%, the ductility is remarkably reduced. is there.

Cu is used in the GP zone, θ ', and
Since S phase is precipitated to improve the strength, it is added when it is desired to secure the strength after baking coating. The addition amount was set to 0.
The reason for limiting the content to 1 to 0.5 wt% is that if the content is less than 0.1 wt%, the improvement in strength is small, and if it exceeds 0.5 wt%, the corrosion resistance decreases.

Fe and Si are usually contained as impurities of Al. However, Fe easily forms a compound with Si, and the compound becomes a starting point of a crack at the time of molding, thus reducing ductility. Therefore, if either of the two exceeds 0.2 wt%, the ductility decreases. Therefore, the content of both is limited to 0.2% or less. Ti, N
Since other impurity elements such as i and Zn reduce ductility, the content is limited to 0.05% or less.

Next, the reason why the average grain size is limited in the present invention will be described. In the 5000 series alloy, when the crystal grains are fine, the binding force between the crystal grains is large and the strength is large, but a strong shear band is generated and a constriction occurs, resulting in a decrease in elongation. There is. This effect becomes remarkable in the low strain rate region where the fixing action with Mg atoms is large and in the uniaxial tension where the slip surface is limited. Therefore, since the elongation is remarkably reduced in a normal tensile test, it has been often the case that the crystal grains are used so large that they do not cause rough skin. On the other hand, in the molding of actual parts such as automobile body panels, it has been found that the strength for allowing the material to flow into the mold is more important than the elongation because a low-viscosity cleaning oil is usually used. Furthermore, the elongation in forming with a real mold is often formed in the biaxial region where shear bands are less likely to occur, and the uniformity of strain due to sliding on the punch surface is important, and it is not always possible to use normal tensile force. It was found that it did not correspond to the elongation of the test.

That is, for the molding of such an actual part, a high-strength material which has a small elongation in a tensile test but is advantageous in the uniformity of strain due to material inflow and sliding on the punch surface is preferred. Was found to exhibit good moldability. Therefore, in order to increase the strength, the crystal grain size is 10 to 25 μm.
Limited to If it is less than 10 μm, the effect of reducing the ductility due to the shear band is greater than the effect of improving the strength, and the formability deteriorates. On the other hand, if it exceeds 25 μm, the effect of improving the moldability due to the improvement in strength cannot be sufficiently obtained. The aluminum alloy plate having such characteristics has a remarkable effect of improving the formability especially when the lubricating oil viscosity is 100 cSt or less, and the viscosity is 100 cS.
If it exceeds t, the conventional crystal grains may be large and a material with excellent ductility may exhibit better formability.
Application to molding using low viscosity oil below t is desirable.

Next, the manufacturing method of the present invention will be described.
First, an aluminum alloy having the above composition is cast, homogenized, and hot-rolled by a conventional method. In homogenization, a compound such as Mg, Fe, or Si formed during casting is dissolved in the matrix to form a solid solution. It has the effect of precipitating precipitates such as Cr, Zr, Mn, etc. to make the final crystal grains finer, but the former requires high temperature and long time, and the latter is finer at relatively low temperature and short time. It is desirable because it precipitates. In the method of the present invention, since sufficient precipitation can be obtained by the intermediate annealing described later, it is not necessary to intentionally precipitate finely during the homogenization treatment, and the conditions are not particularly limited, but homogenization at 480 ° C. or higher is necessary for ensuring ductility. Treatment is desirable. Since hot rolling can obtain sufficient precipitation by the intermediate annealing described later, the conditions are not particularly limited.

[0012] Then, cold rolled 30-80%, 300-5
Intermediate annealing is carried out at 00 ° C. for 30 minutes or more. This is to uniformly and finely precipitate Cr, Zr, and Mn-based precipitates. If the reduction ratio before annealing is less than 30%, the uniformity of precipitation is Cannot be secured. When the annealing temperature is less than 300 ° C,
A sufficient amount of precipitation cannot be expected, and if it exceeds 500 ° C., the precipitate becomes coarse and the grain refining effect is reduced. Furthermore, if the holding time is less than 30 minutes, a sufficient amount of precipitation cannot be obtained, and the grain refinement effect becomes insufficient. Cold rolling rate is 80
If it exceeds%, a macroscopic shear band is likely to occur during the cold rolling process, resulting in a defect in appearance. Therefore, it is necessary to carry out cold rolling for 30 to 80% and hold at 300 to 500 ° C. for 30 minutes or more.

Next, 20% or more of cold rolling is performed to a predetermined plate thickness, heating to a temperature of 450 to 550 ° C., holding immediately or within 60 seconds, and 10% at a rate of 10 ° C./min or more.
Although an annealing treatment for cooling to 0 ° C. or less is performed, when the cold rolling rate before annealing is less than 20%, nucleation of recrystallization is small, and a crystal grain system of 25 μm or less can be obtained even in the presence of fine precipitates. Can not. The reason why the annealing temperature is 450 to 550 ° C. is that
This is because there is a sufficient solutionizing effect and the crystal grains do not become coarse. When the temperature is lower than 450 ° C, the crystal grain size is less than 10 µm and the ductility is excessively lowered, and when it exceeds 550 ° C, a sufficient fine precipitation amount is obtained. This is also because the strength decreases when the crystal grains exceed 25 μm. The holding time is set within 60 seconds because the crystal grains become coarse when the holding time exceeds 60 seconds.

Next, at a cooling rate of 10 ° C./min.
The cooling to 0 ° C. or lower is for preventing the precipitation of the solid solution element. If the condition is deviated from this condition, the amount of the solid solution element decreases due to the precipitation, the ductility decreases, and the dislocations are fixed by Mg atoms. Stretcher strain marks are more likely to occur. After the annealing, if necessary, forced treatment by a tension leveler, skin pass, etc., surface cleaning, etching, rust preventive oil coating, etc. may be performed.

[0015]

EXAMPLES An example of the present invention will be described below.
After melting and casting an Al alloy having the composition shown in Table 1 by a conventional method,
A plate material having a thickness of 1 mm was manufactured under the manufacturing conditions shown in Table 2.
A tensile test is performed on this plate material to determine the tensile strength, proof stress, and elongation, and as a forming test, blank drawing is performed with cylindrical blanking with a blank diameter of 86 mm and a drawing ratio of 2.15, a wrinkle suppression force of 3000 kgf, and a low-viscosity (10 cSt) lubricating condition. Went under. It should be noted that the breaking height obtained under these molding test conditions must be 21 mm or more. The results are shown in Table 3.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

As is clear from Tables 1 to 3, all of the compositions A, B, C and D according to the present invention have a crystal grain size of 15.
.About.22 .mu.m, the tensile strength and proof strength are excellent, and the breaking height in the molding test is 21 mm or more, indicating that the moldability is good. On the other hand, in Comparative Example E, Cr + Mn + Zr = 0.5
6 and a large amount of F and a small amount of F and Mg with no addition of Cr, Mn, and Zr have extremely small or excessive crystal grain sizes, and poor tensile strength, proof stress, and breaking height. Further, in Comparative Example B, the composition is within the range of the present invention, but the production conditions are outside the range of the present invention, and thus the above characteristics are poor.

[0020]

As described above, excellent strength and moldability are exhibited, and particularly when a low viscosity lubricating oil is used, high moldability is exhibited, and rust preventive oil and cleaning oil which are often used in actual operation are used. It is suitable for molding and has a remarkable industrial effect.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoichiro Totsugu 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Minoru Hayashi 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Ryo Tokaibayashi 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (4)

[Claims] 1. Mg4.0-10.0w as an essential component
t% and 0.01 to 0.5 wt% in total of any one or more of Cr, Zr, and Mn, and inevitable impurity Fe,
Molding characterized in that the amount of Si is 0.2 wt% or less, each of the other impurity elements is 0.05 wt% or less, the composition is composed of the balance Al, and the average crystal grain size is 10 to 25 μm. Aluminum alloy plate for use. 2. Mg4.0-10.0w as an essential component
t%, Cu 0.1 to 0.5 wt% and Cr, Zr, Mn
0.01 wt% to 0.5 wt% in total, and the inevitable impurities Fe and Si are each 0.2 w.
t% or less, 0.05 wt% for all other impurity elements
% Or less, having a composition of the balance Al, and having an average crystal grain size of 10 to 25 μm. 3. Mg4.0-10.0w as an essential component
t% and 0.01 to 0.5 wt% in total of any one or more of Cr, Zr, and Mn, and inevitable impurity Fe,
After the amount of Si is 0.2 wt% or less and each of other impurity elements is 0.05 wt% or less, an aluminum alloy composed of the balance Al is cast, homogenized, and hot rolled by a conventional method, and then 30 to 80%. Cold rolled, 30 at 300-500 ° C
Perform intermediate annealing that holds for more than 10 minutes, then perform cold rolling of 20% or more to a predetermined plate thickness, heat to a temperature of 450 to 550 ° C, hold immediately or within 60 seconds, and hold at 10 ° C / mi
A method of manufacturing an aluminum alloy sheet for forming, which comprises subjecting an average grain size to 10 to 25 μm by performing an annealing treatment for cooling to 100 ° C. or less at a rate of n or more. 4. Mg4.0-10.0w as an essential component
t%, Cu 0.1 to 0.5 wt% and Cr, Zr, Mn
0.01 wt% to 0.5 wt% in total, and the inevitable impurities Fe and Si are each 0.2 w.
t% or less, 0.05 wt% for all other impurity elements
% Or less, and cast an Al alloy consisting of the balance Al by a conventional method.
After homogenizing and hot rolling, 30-80% cold rolling, 300
Intermediate annealing is performed by holding at ~ 500 ° C. for 30 minutes or more, and then cold rolling is performed by 20% or more to a predetermined plate thickness.
The average crystal grain size is reduced to 1 by heating to a temperature of up to 550 ° C., holding it immediately or within 60 seconds, and then cooling it to a temperature of 10 ° C./min or more and cooling it to 100 ° C. or less.
The manufacturing method of the aluminum alloy plate for shaping | molding characterized by making it 0-25 micrometers.