JPH07331374A - Aluminum alloy sheet for automobile body sheet and its production and method for forming the same - Google Patents

Abstract

PURPOSE:To obtain an Al alloy sheet for automobile body sheet, excellent in formability under low viscosity lubrication, by specifying a composition consisting of Mg, Fe, Mn, Cr, Zr, and Al and regulating crystalline grain size and surface roughness to specific values, respectively. CONSTITUTION:An Al alloy sheet, which consists of, by weight, 2.0-8.0% Mg, one or more kinds among <=1.5% Fe, <=1.0% Mn, <=0.3% Cr, and <=0.3% Zr, and the balance Al with ordinary impurities and has 50-150mum final crystalline grain size and in which surface roughness is regulated so that it satisfies Ra<=0.5mum and also Ra>=0.87mum in the case of 5% stretch addition, is obtained. Further, this Al alloy sheet can be suitably used for forming by using low viscosity oil of <=20cSt viscosity of lubricating oil. At the time of producing this alloy sheet, an Al alloy ingot of the above composition is hot-rolled and cold-rolled. At this time, final cold rolling is done at <=30% rolling rate and <=0.5mum roll roughness Ra. Then, the resulting cold rolled sheet is subjected to final annealing at >=3.0 deg.C/sec temp. rise rate at a holding temp. between 450 and 550 deg.C or between 520 and (melting point -10) deg.C for <=120sec holding time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy plate most suitable for a molding material such as an automobile body sheet, a method for producing the same and a method for forming the same.

Conventionally, cold-rolled steel sheets have been mainly used for automobile outer panels. Recently, the use of an aluminum alloy plate has been studied in order to reduce the weight of automobile bodies. Molding of an automobile body sheet is generally performed by using a low-viscosity lubricating oil because of easy degreasing and cleaning in a post process. It is known that the moldability under low-viscosity lubrication is superior to a shot dull material that forms micropools on the contact surface with the mold due to its rough surface shape.

[0003]

In the case of an aluminum rolled plate, the above-mentioned shot dull material is transferred by lightly pressing it with a roll having shots in the final pass of cold rolling.
As a result, the number of passes is one extra step, and the shot processing of the rolls and frequent roll replacement are disadvantageous in that the cost is high.

As a result of studying the above problems, the present invention
Although not a shotdal material, it is an aluminum alloy sheet that forms micropools on the surface under low-viscosity lubrication to improve the formability, a method for producing the same, and a method for forming the same.

[0005]

Means for Solving the Problems In the present invention, Mg 2.0 to
Including 8.0 wt%, Fe 1.5 wt% or less, M
n 1.0 wt% or less, Cr 0.3 wt% or less, Zr0.
3 wt% or less of any one kind or two or more kinds, the rest is made of normal impurities and Al, and the final crystal grain size is 50 to
Molding using a low-viscosity oil having a lubricating oil viscosity of 20 cSt or less, which is 150 μm, has a surface roughness Ra ≦ 0.5 μm, and Ra ≧ 0.8 μm when a 5% stretch is added. An aluminum alloy plate for a car body sheet, which is suitable for the above, is defined as claim 1, and Mg 2.0 to
8.0 wt%, and the content of one or more of Fe, Mn, Cr, and Zr is 0.1 <Fe ≦ 1.5 wt%,
0.1 <Mn ≦ 1.0 wt%, 0.05 <Cr ≦ 0.3
wt%, 0.05 <Zr ≤ 0.3 wt%, the rest of the alloy ingot consisting of normal impurities and Al is hot-rolled, then subjected to intermediate annealing if necessary, cold-rolled, and finally cold-rolled. Final cold rolling is performed with a roll having a rate of 30% or less and a roll roughness Ra ≦ 0.5 μm, and then a temperature rising rate of 3.0 ° C. /
sec or more, holding temperature 450 to 550 ° C., holding time 12
The final crystal grain is 50 to 150 μm and the surface roughness is Ra ≦ 0, which is characterized by performing a final annealing for 0 sec or less.
R when 0.5 μm and 5% stretch is added
A method for producing an aluminum alloy sheet for an automobile body sheet, which is suitable for molding using a low-viscosity oil having a lubricating oil viscosity of 20 cSt or less, in which a ≧ 0.8 μm, is defined as claim 2, and M
g 2.0 to 8.0 wt% and further Fe, Mn, C
The content of at least one of r and Zr is Fe ≦ 0.1 wt
%, Mn ≦ 0.1 wt%, Cr ≦ 0.05 wt%, Zr
An alloy ingot containing ≦ 0.05 wt% and the remaining normal impurities and Al was hot-rolled, cold-rolled, and finally cold-rolled by a roll having a roll roughness Ra ≦ 0.5 μm. After that, the temperature rising rate is 3.0 ° C./sec or more, and the holding temperature is 52.
The final crystal grains are characterized by being subjected to final annealing at 0 ° C to a melting point of -10 ° C and a holding time of 120 sec or less.
Suitable for molding using low viscosity oil having a lubricating oil viscosity of 20 cSt or less, which has a surface roughness of Ra of 0.5 μm and a Ra of 0.8 μm when a 5% stretch is added. A method for manufacturing an aluminum alloy sheet for a body sheet is defined as claim 3, and Mg 2.0 to 8.0 w
including t%, Fe1.5 wt% or less, Mn1.0
wt% or less, Cr 0.3 wt% or less, Zr 0.3 wt%
It contains any one or more of the following, and the balance is normal impurities and Al, and the final crystal grain size is 50 to 150 μm.
m, a surface roughness Ra ≦ 0.5 μm, and an aluminum alloy plate having Ra ≧ 0.8 μm when a 5% stretch is added, using a low-viscosity oil having a lubricating oil viscosity of 20 cSt or less, A fourth aspect of the present invention is a method for forming an aluminum alloy sheet for an automobile body sheet, which is formed under the condition that the maximum equivalent strain of the sliding portion is 0.06 or more.

[0006]

According to the present invention, the surface of the above Al alloy is roughened by adjusting the final crystal grain size by a special process and generating grain boundary steps in the crystal grains during material deformation, especially during drawing. Even if it is a surface-milled material, the surface becomes shotdal even if it is a mill finish material, and micropools are formed to improve the formability in a low-viscosity lubricating oil.

The reason why the alloy composition is limited as described above in the present invention is as follows. When Mg forms a solid solution, the strength is increased, and at the same time, the work hardenability is increased to increase the ductility and contribute to the improvement of the formability.
The reason why the addition amount is limited to 2.0 to 8.0 wt% is
If less than 2.0 wt%, the effect is small, 3.0 wt%
This is because the hot workability is deteriorated and the manufacturing cost is increased if the value exceeds. Fe, Mn, Cr, Zr, etc. all have the effect of increasing the strength, but Fe1.5 wt%, Mn
If it exceeds 1.0 wt% and Cr 0.3 wt% Zr 0.3 wt%, the ductility decreases. In addition, Cu, S as impurities
Although there are i, Ti, etc., if the Cu content is 0.5 wt% or less, the Si content is 0.2 wt% or less, and the Ti content is 0.2 wt% or less, the effect of the present invention is not impaired.

Next, the manufacturing method and characteristics will be described. There are two manufacturing methods of the present invention. Fe, Mn, C
There is a slight difference between when the content of r and Zr is high and when the content is low. First, casting, solution treatment, hot rolling, and cold rolling are performed by usual methods, and thereafter, Fe, Mn, Cr, and Z of claim 2 are performed.
When the content of r is large, that is, 0.1 <Fe ≦ 1.5
wt%, 0.1 <Mn ≦ 1.0 wt%, 0.05 <Cr
When ≦ 0.3 wt% and 0.05 <Zr ≦ 0.3 wt%, intermediate annealing is performed as necessary during the cold rolling, and the final cold rolling is performed at a rolling rate of 30% or less, and the roll roughness Ra. ≤
Rolling is performed using a normal roll of 0.5 μm or less, and then final annealing is performed at a temperature rising rate of 3.0 ° C./sec or more and a holding temperature of 4
It is carried out at 50 to 550 ° C. and a holding time of 120 sec or less.

In this case, the growth of the crystal grains is suppressed by the formation of the crystallized products due to the above-mentioned components, and the crystal grains become finer, so that they cannot be coarsened only by changing the annealing conditions. For coarsening, it is necessary to reduce the recrystallization driving force due to the low cold rolling rate. If the cold rolling rate exceeds 30%, such an effect cannot be exhibited, so the cold rolling rate before the final annealing is 30%.
% Or less, cold rolling is performed. Then, the final annealing is performed at a temperature rising rate of 3.0 ° C./sec or more and a holding temperature of 450.
The final annealing is performed at ~ 550 ° C for a holding time of 120 sec or less, but this is because the temperature rising rate is fast and the crystal orientation becomes a random orientation. This is because a step is generated. The cooling rate of the final annealing is preferably 3.0 ° C./sec or more from the viewpoint of preventing Luders band generation. The roughness of the final cold rolling roll is set to Ra ≦ 0.5 because the use of a normal roll is one of the merits of the present invention.

Next, according to claim 3, Fe, Mn, Cr, Zr,
Fe content is small, Fe ≦ 0.1 wt%, Mn ≦ 0.1
wt%, Cr ≦ 0.05 wt%, Zr ≦ 0.05 wt%
In the case of, cold rolling is performed in the usual way, and then
The final annealing is performed at a heating rate of 3.0 ° C./sec or more and a holding temperature of 5
It is carried out at 20 ° C to a melting point of -10 ° C and a holding time of 120 sec or less. This is because if the holding temperature is lower than 520 ° C., coarsening of crystal grains is unlikely to occur, and if the temperature is higher than the melting point −10 ° C., melting may occur. Further, the cooling rate is preferably 3.0 ° C./sec or more from the viewpoint of preventing the Luders band from being generated.

The plate material thus obtained has a final crystal grain size of 50 to 150 μm and a surface roughness of Ra ≦ 0.
5 and Ra ≧ 0 when adding 5% stretch.
8, a plate material suitable for molding using a low viscosity of lubricating oil viscosity of 20 cSt or less can be obtained, but the size of the final crystal grain is specified in the above range because the grain boundary step is less than 50 μm when the material is deformed. It does not easily occur, and when it exceeds 150 μm,
Although the effect of generation is large, rough skin occurs and there is a problem in appearance after molding. Therefore, a more desirable range is 50 to 10.
It is 0 μm.

Further, the plate material of the present invention is a mill finish material, and the center line average roughness Ra is Ra ≦ 0.5 μm in order to distinguish its surface state from the shotdal material. Further, Ra ≧ 0.8 μm when a 5% stretch is added in order to regulate the degree of occurrence of a grain boundary step due to deformation.
The condition was that 5% stretch has considerable strain:
<Ε> = elongation strain: e <ε> = √ (3/2) I
It can be represented by n (1 + e), and the equivalent strain: <ε> =
Corresponds to 0.06. This value is the strain normally applied to the sliding part of the actual molded article of the automobile body sheet. When this amount of deformation is added, the roughened state on the surface is Ra <0.8.
If it is μm, the effect of improving the formability is not sufficient. Furthermore, the reason why the low-viscosity oil having a lubricating oil viscosity of 20 cSt or less is defined is that since a sufficient oil film is formed when the lubricating oil viscosity exceeds 20 cSt, the smaller the roughness is, the better the moldability is. Is.

When the aluminum alloy sheet material of the present invention is used for forming, the maximum value of the equivalent strain of the sliding portion is 0.
The reason why the molding is performed under the molding condition of not less than 06 is that if the sliding part of the molded product is deformed by less than 0.06 by the equivalent strain, the grain boundary step is not sufficiently generated and the moldability is improved. This is because it does not exert the effect.

[0014]

EXAMPLES Examples of the present invention will be described below.
An Al alloy having the composition shown in Table 1 was hot rolled by a conventional method, and then cold rolled (Ra = 0.4 μ in the final cold rolling roll).
m was used) and the final annealing was performed under the manufacturing conditions shown in Tables 2 and 3 to obtain a plate material having a thickness of 1 mm. With respect to this plate material, Ra of the base plate was measured in a direction perpendicular to the rolling direction, and Ra after 5% stretch was added in the rolling direction was measured by the same method as the base plate Ra. Also, as a forming test, punch diameter φ33m
m, cylindrical drawing with a drawing ratio of 1.94, wrinkle holding force of 100
It was carried out under the conditions of 0 kgf and low viscosity rust preventive oil coating oil having a lubricating oil viscosity of 5 cSt. Furthermore, the appearance after molding is ⊚: good, ∘: no problem, Δ: acceptable range, Luders or rough skin: N
It was evaluated as G. The results are shown in Tables 2 and 3.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

As is clear from Tables 1, 2 and 3, the condition No. corresponding to claim 2 is satisfied. 1.2.3.5.6.
7.8. And the condition No. corresponding to claim 3. 4 and No. 9.10.11. Has excellent moldability,
The appearance after molding is also good. On the other hand, when compared with the same composition, No. 12, 13, 15, 17, 1
Since the final cold rolling rate of 8, 19, 20 is larger than 30%,
The final crystal grain size is small, Ra after 5% stretching is also small, and moldability is poor. No. No. 14 has a final working ratio of more than 30%, and the final annealing condition is out of the range of the present invention, so that the final crystal grain size is small, Ra after 5% stretching is also small, and the formability is poor. No. In No. 16, since the final annealing conditions were out of the range of the present invention, the final crystal grains were large and rough skin was generated. N
o. No. 21, since the final annealing condition is outside the scope of the present invention,
Ra after 5% stretching is small and moldability is poor. Furthermore, No. In No. 22.23, since the final annealing condition is out of the range of the present invention, the final crystal grain size is also out of the range of the present invention, rough skin occurs, and moldability is deteriorated. The aluminum alloy plate according to the present invention has a conventional shotal material No. Two
It can be seen that the moldability is equivalent to that of Nos. 4 to 26.

[0019]

As described above, according to the present invention, it is possible to supply a material having the same high moldability as that of the conventional shot dull material, an excellent appearance after molding, and a low cost. Therefore, a remarkable industrial effect can be expected.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Kakio 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. (72) Inventor Yoichiro Toguji 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Inventor Shintaku Yasunaga 1-4-1 Chuo, Wako-shi, Saitama Inside Honda R & D Co., Ltd. (72) Inventor Noboru 1-4-1 Chuo, Wako, Saitama No. Stock Company Honda Technical Research Institute

Claims (4)

[Claims] 1. An element containing 2.0 to 8.0 wt% of Mg, further containing 1.5 wt% or less of Fe, 1.0 wt% or less of Mn, and Cr.
Either 0.3 wt% or less, Zr 0.3 wt% or less 1
Or 2 or more, and the balance is normal impurities and Al, the final crystal grain size is 50 to 150 μm, the surface roughness is Ra ≦ 0.5 μm, and Ra ≧ 5% stretch is added. An aluminum alloy sheet for a vehicle body sheet, which is suitable for molding using a low-viscosity oil having a lubricating oil viscosity of 20 cSt or less, which has a thickness of 0.8 μm. 2. Mg 2.0-8.0 wt%, and the content of at least one of Fe, Mn, Cr, and Zr is 0.1 <Fe ≦ 1.5 wt%, 0.1 <Mn ≦ 1.0w
t%, 0.05 <Cr ≦ 0.3 wt%, 0.05 <Zr
After the alloy ingot containing ≦ 0.3 wt% and the rest ordinary impurities and Al is hot-rolled, intermediate annealing is performed if necessary, and cold rolling is performed, and the final cold rolling rate is 30% or less, and the roll roughening is performed. Final cold rolling is performed with a roll having a degree Ra of 0.5 μm, and then a temperature rising rate of 3.0 ° C./sec or more and a holding temperature of 4
The final crystal grain is 50 to 150 μm, which is characterized by performing a final annealing at 50 to 550 ° C. and a holding time of 120 sec or less.
m, surface roughness Ra ≦ 0.5 μm, and Ra ≧ 0.8 μm when 5% stretch is added, suitable for molding using low viscosity oil with lubricating oil viscosity of 20 sec or less A method for manufacturing an aluminum alloy sheet for a sheet. 3. Mg of 2.0 to 8.0 wt% is contained, and the content of at least one of Fe, Mn, Cr and Zr is F.
e ≦ 0.1 wt%, Mn ≦ 0.1 wt%, Cr ≦ 0.0
An alloy ingot containing 5 wt% and Zr ≦ 0.05 wt%, the balance of which is normal impurities and Al is hot-rolled, cold-rolled, and finally cold-rolled. Roll having a roll roughness Ra ≦ 0.5 μm After that, the temperature rising rate is 3.0 ° C./sec or more,
Holding temperature 520 ° C-melting point-10 ° C, holding time 120s
ec or less final annealing is performed, the final crystal grains are 50 to 150 μm, and the surface roughness is Ra ≦ 0.5 μm.
m and Ra ≥ 0. 5 when a 5% stretch is added.
A method for producing an aluminum alloy plate for an automobile body sheet, which is suitable for molding using a low-viscosity oil having a lubricating oil viscosity of 20 cSt or less, which is 8 μm. 4. An element containing 2.0 to 8.0 wt% of Mg, further containing 1.5 wt% or less of Fe, 1.0 wt% or less of Mn, and Cr.
Either 0.3 wt% or less, Zr 0.3 wt% or less 1
Or 2 or more, and the balance is normal impurities and Al, the final crystal grain size is 50 to 150 μm, the surface roughness is Ra ≦ 0.5 μm, and Ra ≧ 5% stretch is added. An aluminum alloy plate having a thickness of 0.8 μm is used with a low-viscosity oil having a lubricating oil viscosity of 20 cSt or less,
A method for forming an aluminum alloy sheet for an automobile body sheet, which is formed under the condition that the maximum equivalent strain of the sliding portion is 0.06 or more.