JP2823797B2 - Manufacturing method of aluminum alloy sheet for forming - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an aluminum alloy sheet for forming and processing, and in particular, has a high strength and a good press formability, has an excellent surface appearance after forming, and is used for transportation of automobile outer panels. The present invention relates to a method for producing an aluminum alloy sheet for forming work suitable as a material for equipment.

[0002]

2. Description of the Related Art In recent years, transport equipment such as automobiles has been actively reduced in weight from the viewpoint of protection of the global environment. There is an active movement to reduce weight by changing from steel to aluminum, and various aluminum alloys are also being developed for automotive components. As aluminum alloys for automobile outer panels, in Japan, 5000 series Al-Mg-Zn-C
U alloys (JP-A-53-103914, JP-A-58-171547) and Al-Mg-Cu alloys (JP-A-1-219139) have been developed and some of them have been commercialized. Some are.

In the United States and Europe, 6000 series Al-Mg-Si alloys, 6009, 6111, 6016 alloys and the like have been proposed. 6000 series aluminum alloy has a formability of 50
Although it is somewhat inferior to the 00 series aluminum alloy, it has sufficient molding characteristics for automotive outer panels, and high strength can be obtained by heat treatment in the paint baking process, so it can be thinner and lighter than the 5000 series aluminum alloy. Although it can be expected, there is a disadvantage that the surface appearance after the forming process is inferior to that of the 5000 series alloy.

[0004] Typical defects that occur during molding include a stretcher strain mark (hereinafter referred to as an SS mark), an orange peel (hereinafter referred to as a rough skin), and a ridging mark. The SS mark is easily generated in a material having a large yield point elongation at the time of plastic working, and is often a problem particularly in a 5000 series alloy. It is well known that rough skin is likely to occur when the crystal grain size of the material is large. Ridging marks are caused by the fact that even when the crystal grain size is small enough not to cause skin roughness, the deformation behavior at the boundary of the cluster is greatly different if the crystal grains with similar crystallographic orientation are in a cluster. This is the unevenness of the surface that occurs.

For the SS mark and rough skin, measures have been taken to prevent the leveler from being corrected and the crystal grains to be refined, respectively. Since this is only a problem when required, preventive measures have not been sufficiently studied. Even when a 6000 series aluminum alloy plate is formed as an automobile outer plate, the occurrence of ridging marks is often observed and poses a problem.

[0006]

SUMMARY OF THE INVENTION The present invention focuses on a 6000 series aluminum alloy which can be expected to be thinner and lighter than a 5000 series alloy for transportation equipment such as an automobile outer panel. In order to eliminate the points, it was made as a result of detailed examination of the relationship between chemical components and manufacturing conditions and surface defects after molding, especially ridging marks, the purpose of which is
An object of the present invention is to provide a method for producing an aluminum alloy sheet for forming, which has high strength and good formability, and has excellent surface appearance after forming.

[0007]

In order to achieve the above object, a method of manufacturing an aluminum alloy sheet for forming according to the present invention is as follows: Si: 0.4% or more and less than 1.7% by weight;
Mg: an aluminum ingot containing 0.2 to less than 1.2%, the balance being Al and unavoidable impurities, was heated to 500 ° C.
After the solution treatment at a temperature lower than the melting point, the hot rolling is started by cooling from a temperature of 500 ° C. or more to a temperature range of 350 to 450 ° C., and the hot rolling is completed in a temperature range of 200 to 300 ° C. Immediately before the solution treatment, cold rolling is performed at a working ratio of 50% or more, and subsequent to the cold rolling, the material is heated to a temperature range of 500 to 580 ° C. at a heating rate of 2 ° C./s or more and heated for 10 minutes or less. The first feature of the structure is that the quenching treatment is performed by cooling to a temperature of 100 ° C. or less at a cooling rate of 5 ° C./s or more after performing the solution treatment for holding for a time.

[0008] The composition of the aluminum alloy ingot is S
i: 0.4% or more and less than 1.7%, Mg: 0.2% or more and less than 1.2%, Cu: 1.0% or less, Z
n: 1.0% or less, Mn: 0.5% or less, Cr: 0.2
% Or less, Zr: 0.2% or less, V: 0.2% or less, and a second feature of the structure is that the balance is composed of Al and inevitable impurities.

Further, by weight%, Si: 0.8 to 1.3.
%, Mg: an aluminum alloy containing 0.3 to 0.8% with the balance being Al and unavoidable impurities, or Si: 0.8%
1.3%, Mg: 0.3-0.8%, and further C
u: 1.0% or less, Zn: 1.0% or less, Mn: 0.5
% Or less, Cr: 0.2% or less, Zr: 0.2% or less,
V: one or more kinds of 0.2% or less, the balance A
l and an aluminum alloy ingot consisting of unavoidable impurities,
After homogenizing at a temperature of 500 ° C. or higher but lower than the melting point, 50
The hot rolling is started by cooling from a temperature of 0 ° C. or more to a temperature range of 350 to 400 ° C.
Finished in the temperature range of ℃, 80% workability just before solution treatment
After performing the cold rolling described above, and subsequent to the cold rolling, the solution is heated to a temperature range of 500 to 580 ° C. at a heating rate of 2 ° C./s or more and held for a time of 1 minute or less. ° C /
The third and fourth structural features are that the quenching process is performed by cooling to a temperature of 100 ° C. or less at a cooling rate of s or more.

According to the present invention, in order to suppress the occurrence of ridging marks in a 6000 series aluminum alloy without deteriorating formability, the alloy composition is specified, homogenization conditions, hot rolling conditions, cold working, It is based on the knowledge that it is necessary to strictly control the temperature and final solution treatment conditions, and the essential component Si in the alloy composition is 0.4% or more and less than 1.7%. ,
Mg is contained in a range of 0.2% or more and less than 1.2%.
Si and Mg coexist to form Mg ₂ Si and increase the strength of the alloy. If the content of Si is less than 0.4%, sufficient strength cannot be obtained, and if the content is 1.7% or more, when the alloy is pressed, the yield strength during processing is high and the formability is poor. Also, the corrosion resistance deteriorates. If Mg is less than 0.2%, sufficient strength cannot be obtained,
If it is 1.2% or more, the proof stress is high, and the moldability and the characteristic that the shape of the press die can accurately appear at the time of press working, that is, the so-called shape freezing property deteriorates. In order to impart more excellent dent resistance and shape freezing after forming to the aluminum alloy sheet of the present invention, Si, which is an essential component, is contained in an amount of 0.8 to 1.
It is preferable to limit 3% and Mg to a range of 0.3 to 0.8%.

[0011] In addition to the above essential alloy components, the strength can be further improved by adding 1.0% or less of Cu as a selective component. If the Cu content exceeds 1.0%, the corrosion resistance is lowered and the rust resistance is poor. The addition of Zn also helps to increase the strength, but if it exceeds 1.0%, the corrosion resistance is reduced and the aging at room temperature is increased. Addition of Mn: 0.5% or less, Cr: 0.2% or less, Zr: 0.2% or less, and V: 0.2% or less further improves the strength of the alloy and refines the crystal grains to form the alloy. Effective in preventing rough skin during processing. If these components are added in excess of the upper limits, the formation of coarse intermetallic compounds increases and the formability deteriorates.

In the present invention, in addition to the above-mentioned elements, Ti: 0.05% or less, or Ti: 0.05% or less and B: 100 ppm or less are added to refine the crystal grains of the ingot. Is also good. If the addition amounts of Ti and B exceed the respective upper limits, coarse intermetallic compounds increase and formability decreases.
Fe as an unavoidable impurity is allowed up to 0.3%. If it exceeds 0.3%, the moldability, particularly the bending workability, tends to decrease.

The conditions for producing the aluminum alloy of the present invention will be described. An ingot of an aluminum alloy having the above-mentioned alloy composition is produced by semi-continuous casting, and the ingot is heated to 500 ° C.
As described above, the homogenization treatment is performed in a temperature range lower than the melting point of the alloy.
If the homogenization treatment temperature is lower than 500 ° C., the ingot segregation is not sufficiently removed, the homogenization of the alloy structure is not sufficient, and the solid solution of the Mg ₂ Si component contributing to the strength is insufficient, and the formability may be poor. is there. After the homogenization treatment, hot rolling is started at a temperature of 350 to 450 ° C, more preferably 350 to 400 ° C, without cooling to room temperature. When the ingot is cooled to room temperature and heated to the hot rolling temperature after the homogenization treatment, coarse precipitates of Mg ₂ Si are generated during heating, so that solid solution in the solution treatment becomes difficult and the formability is reduced. Become. When cooled to room temperature after the homogenization treatment, it is heated again to a temperature of 500 ° C. or higher, and then 350 to 450 ° C., more preferably 350 to 450 ° C.
It is necessary to cool to a temperature in the range of 00 ° C. and start hot rolling.

[0014] The hot rolling is started in a temperature range of 350 to 450 ° C, more preferably 350 to 400 ° C, and 200 to 3 ° C.
The process ends at a temperature of 00 ° C, more preferably 200 to 250 ° C. If the starting temperature is lower than 350 ° C., the deformation resistance of the material is large, and if it exceeds 450 ° C., the structure at the time of hot rolling grows greatly, and the crystallographic orientation is close to that of the alloy plate after cold rolling and solution treatment. Since the objects are likely to form a group, ridging marks are likely to be formed on the surface of the plate material after the press working. When the hot rolling is completed at a temperature of 300 ° C. or higher, secondary recrystallization is likely to occur after rolling, and the structure becomes coarse, which causes ridging marks. When the end temperature is lower than 200 ° C., the stainless steel of the water-soluble rolling oil is apt to remain, thereby deteriorating the surface quality of the sheet material.

After completion of the hot rolling, if necessary, intermediate annealing,
After performing cold rolling to a predetermined thickness, cold rolling is performed immediately before the solution treatment to a working ratio of 50% or more, more preferably 80% or more, and the solution treatment is performed subsequent to the cold rolling.
If the working ratio of the cold rolling immediately before the solution treatment is less than 50%,
The crystal grains after the solution treatment are likely to become coarse and the skin may be rough. In addition, the decomposition of the hot-rolled structure is not sufficiently performed, and ridging marks are easily generated, which causes a reduction in formability.

The solution treatment is performed at a heating rate of 2 ° C./s or more for 5 hours.
Heat to a temperature range of 00-580 ° C. Heating rate is 2 ℃
If it is less than / s, the crystal grains become coarse and the surface becomes rough during press molding. When the heating temperature is lower than 500 ° C., the solid solution of the precipitate is insufficient, and the predetermined strength and moldability cannot be obtained. Even if predetermined strength and moldability can be obtained, an extremely long heat treatment is required, which is not industrially preferable. 58
When heated to a temperature higher than 0 ° C., local eutectic melting is likely to occur and the formability is deteriorated. The holding time is preferably 10 minutes or less, and if the holding time exceeds 10 minutes, the productivity is lowered and is not industrially preferable. More preferably, it is 1 minute or less. After heating, it is cooled to a temperature of 100 ° C. or less at a cooling rate of 5 ° C./s or more, and quenching is performed. If the cooling rate is less than 5 ° C./s, coarse compounds are precipitated at the crystal grain boundaries to reduce ductility and strength,
Decreases moldability.

[0017]

In the present invention, by selecting a material composition for having excellent strength and formability, and combining ingot homogenization processing, hot rolling, cold rolling and solution treatment under specific conditions, The surface state after the forming process is made excellent by reducing the formability, setting the fine crystal grain size that does not cause skin roughness, and randomizing the crystallographic orientation.

[0018]

Hereinafter, examples of the present invention will be described in comparison with comparative examples. Example 1 Si: 1.2 wt%, Mg: 0.6 wt%, Mn: 0.1 wt%, Fe: 0.2 wt%, Al
An aluminum alloy ingot consisting of the remaining portion was manufactured by semi-continuous casting, and the obtained ingot was subjected to surface cutting and then processed according to the manufacturing conditions shown in Table 1 to obtain a 1 mm thick plate. Tensile tests were performed on these plate materials, and ridging marks, rough surfaces, and SS
The occurrence of marks was visually observed, and an intergranular corrosion test was performed. The proof stress (after-BH proof stress) after heat treatment at 200 ° C. for 30 minutes was also measured assuming a paint baking treatment when applied to an automobile outer panel or the like. Table 2 shows the test and observation results. As can be seen from Table 2, all of the test materials manufactured according to the present invention have excellent strength properties of not less than 100 MPa in proof stress and not less than 28% in elongation, and have excellent proof stress after BH. The surface appearance after that was also good, and in the intergranular corrosion test, excellent corrosion resistance was exhibited at a corrosion depth of 0.1 mm or less.

[0019]

[Table 1]

[0020]

[Table 2]

Comparative Example 1 An ingot of an aluminum alloy having the same composition as in Example 1 was produced by semi-continuous casting. The obtained ingot was processed according to the manufacturing conditions shown in Table 3 to obtain a plate having a thickness of 1 mm. The same test as in Example 1 was performed on these plate materials. Table 4 shows the results. In addition, those which deviate from the conditions of the present invention are underlined.

[0022]

[Table 3] 《Table Note》 540 × 8-RT is heated at 540 ° C for 8h, then cooled to room temperature and heated from room temperature to 380 ° C again

[0023]

[Table 4]

As shown in Table 4, the manufacturing conditions No. 1 and N
In o.2, the hot rolling start temperature was too high, and in Condition No. 3, the hot rolling end temperature was too high, so that all of the test materials manufactured according to these conditions had ridging marks after forming. In condition No. 8, the degree of cold rolling was small and the hot rolled structure of the test material was not sufficiently decomposed, so that ridging marks were formed after the forming process, and coarsening was caused by coarsening of crystal grains. In condition No. 9, the rate of temperature rise during the solution treatment was too slow, so that the crystal grains became coarse and the surface was roughened by press molding. Condition No.1
Sample No. 0 was cooled to room temperature and reheated to the hot rolling temperature after the homogenization treatment, so that the test material did not have sufficient penetration of alloying elements in the solution treatment, and the elongation was low and the formability was poor. In condition No. 11, since the solution treatment temperature was too low, the solid solution of the precipitate was insufficient and both the strength and the elongation were inferior.

Example 2 An aluminum alloy ingot having the composition shown in Table 5 was produced by semi-continuous casting, and the obtained ingot was subjected to surface cutting and then processed according to production condition No. 1 in Table 1 to obtain a 1 mm-thick ingot. Plate material was used. The same test as in Example 1 was performed on these plate materials. Table 6 shows the test results. As can be seen from Table 6, the test materials A to G manufactured according to the present invention all had a proof stress of 100M.
It had a high strength of Pa or more and an elongation of 28% or more, and was excellent in moldability and surface appearance after molding.
The intergranular corrosion test also showed excellent corrosion resistance at a corrosion depth of 0.1 mm or less.

[0026]

[Table 5]

[0027]

[Table 6]

Comparative Example 2 An aluminum alloy ingot having a composition shown in Table 7 was produced by semi-continuous casting, and the obtained ingot was subjected to surface cutting and then processed according to production conditions No. 1 in Table 1 to obtain a 1 mm-thick ingot. Plate material was used. Table 8 shows the results of the same test as in Example 1 performed on these plate materials. As can be seen from Table 8, the test material of the alloy H 2 had low strength due to low contents of Si and Mg, and had large crystal grains, resulting in rough surface during molding. Alloy I has a low Mg content and thus has insufficient strength, and a large amount of Cu has a large corrosion depth in the intergranular corrosion test and poor corrosion resistance. Alloy J had a high Si content, so that the strength increased and the elongation decreased, and sufficient formability could not be obtained. Alloy K is A5
SS marks were formed in the forming process with 182 alloy, and the surface appearance was impaired. In Table 7, those outside the conditions of the present invention are underlined.

[0029]

[Table 7]

[0030]

[Table 8]

[0031]

As described above, according to the present invention, excellent strength and moldability, particularly excellent press moldability, good surface appearance after molding, and the manufacture of transportation equipment members such as outer panels for automobiles. A method for manufacturing a suitable aluminum alloy sheet for forming is provided.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C22F 1/04-1/057 C22C 21/00-21/18

Claims (4)

(57) [Claims] 1. Si: 0.4% or more and 1.7% by weight%
, Mg: 0.2% or more and less than 1.2%, with the balance being A
l and an aluminum alloy ingot consisting of unavoidable impurities,
After homogenizing at a temperature of 500 ° C. or higher but lower than the melting point, 50
It is cooled from a temperature of 0 ° C. or more to a temperature range of 350 to 450 ° C. to start hot rolling.
Finished in a temperature range of ℃, and worked 50% immediately before solution treatment
The above cold rolling is performed, and subsequently to the cold rolling, 2 ° C /
After performing a solution treatment of heating to a temperature range of 500 to 580 ° C. at a temperature rising rate of s or more and holding for a time of 10 minutes or less,
A method for producing an aluminum alloy sheet for forming, characterized by quenching by cooling to a temperature of 100 ° C or lower at a cooling rate of 5 ° C / s or higher. 2. The method according to claim 1, wherein the aluminum alloy comprises Si:
0.4% or more and less than 1.7%, Mg: 0.2% or more and 1.2
%, Cu: 1.0% or less, Zn: 1.0% or less, Mn: 0.5% or less, Cr: 0.2% or less, Zr:
The aluminum according to claim 1, characterized in that it contains one or more of 0.2% or less and V: 0.2% or less, and has a composition consisting of the balance of Al and inevitable impurities. Manufacturing method of alloy sheet. 3. Si by weight: 0.8-1.3%, M
g: An aluminum alloy ingot containing 0.3 to 0.8%, the balance being Al and unavoidable impurities, is homogenized at a temperature of 500 ° C. or more and less than the melting point, and then 350 to 400 ° C. from a temperature of 500 ° C. or more. C. to a temperature range of 200 ° C. to start hot rolling, finish the hot rolling in a temperature range of 200 to 250 ° C., and perform cold rolling at a working ratio of 80% or more immediately before solution treatment. Subsequent to the cold rolling, a solution treatment is performed by heating to a temperature range of 500 to 580 ° C. at a heating rate of 2 ° C./s or more and holding for a time of 1 minute or less, and then at a cooling rate of 5 ° C./s or more. A method for manufacturing an aluminum alloy sheet for forming, characterized by quenching by cooling to a temperature of 100 ° C. or lower. 4. The method according to claim 1, wherein the aluminum alloy comprises Si:
0.8-1.3%, Mg: 0.3-0.8%, C
u: 1.0% or less, Zn: 1.0% or less, Mn: 0.5
% Or less, Cr: 0.2% or less, Zr: 0.2% or less, and V: 0.2% or less, having a composition comprising the balance of Al and inevitable impurities. The method for producing an aluminum alloy sheet for forming according to claim 3, characterized in that: