JPH0570907A - Manufacture of aluminum alloy material for forming - Google Patents

Abstract

PURPOSE:To manufacture an aluminum alloy material for forming excellent in formability at the time of press working, shape freezability and curing performance for baking and suitable particularly for transporting equipment including automobile body sheet materials. CONSTITUTION:This cover is a method in which an alloy material contg. 0.4 to 1.5% Si and 0.3 to 1.5% Mg or furthermore contg. one or more kinds among <=1.00% Cu, <=0.40% Mn, <=0.20% Cr and <=0.20% V and the balance Al with inevitable impurities is subjected to semi-continuous casting; the obtd. ingot is subjected to usual rolling, is thereafter subjected to soln. treatment, is hardened and is allowed to stand at a room temp.; and the material is subjected to pre-heat treatment in the temp. range of 50 to 120 deg.C for 2 to 200hr and is thereafter subjected to final heat treatment at 180 to 250 deg.C for 1 to 10min.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a molding process which is particularly suitable for the production of transportation equipment including body sheet materials for automobiles and which is excellent in moldability during press working, shape freezing property and paint bake hardening property. The present invention relates to a method for manufacturing an aluminum alloy material for automobiles.

[0002]

2. Description of the Related Art Conventionally, various aluminum alloy materials have been developed and used as materials for transportation equipment including automobile body sheet materials. In particular, due to the recent strengthening of various laws and regulations as a measure against global warming, there is a very active movement to reduce the weight by converting many parts from steel materials to aluminum alloy materials.

For example, as an automobile body sheet material,
The required performances are 1) moldability, 2) shape fixability (the shape of the press die is accurately produced during press working), 3) high strength, 4) dent resistance, 5) corrosion resistance and the like.

Under these circumstances, in Japan, where the demands of press makers are high, 5000 series Al-Mg-Zn-Cu with good formability is used for automobile body sheet materials and the like.
Alloys (JP-A-53-103914, 58-17154)
7) and Al-Mg-Cu alloy (JP-A-1-21913).
The development of 9) is mainly performed, mass production and practical use.

On the other hand, the strength of 60
00-based Al-Mg-Si alloy 6009, 611
1,6016 alloy has been developed and put into practical use. High strength can be obtained from these alloys by heat treatment at 200 ° C. for about 30 minutes in the paint baking process (paint baking hardening).
By increasing this strength, it is possible to make the wall thickness even thinner than the 5000 series alloy, that is, to reduce the weight. However, in Japan, the baking temperature is as low as 170-180 ° C, so 30 mi
It is not possible to expect a sufficiently high strength in the current alloy and manufacturing process by heating n. Furthermore, this 600
The 0-based alloy is evaluated to have a slight deterioration in formability due to aging hardening at room temperature and a little inferior corrosion resistance, but in Japan where demands for performance are strict, the coating baking process is changed to a higher temperature or longer time than before. Unless it is not used, there is no merit to 5000 series alloys and there are few examples of adoption.

On the other hand, the shape fixability becomes better as the longitudinal elastic modulus becomes larger and the proof stress becomes smaller (reference SAE Paper No. 890719). The longitudinal elastic modulus of aluminum alloy is 7,000 kgf / mm ^2, which is about 1/3 of 21,000 kgf / mm ² of iron and steel. Therefore, unless the proof stress of the aluminum alloy plate during press working is considerably reduced, the shape is frozen. Unable to get the material of nature. However, when it is attempted to obtain a tensile strength of about 30 kgf / mm ² equivalent to that of a steel plate as a structure, the aluminum alloy plate manufactured by the conventional method has a tensile strength of 500.
The yield strength of both 0 series and 6000 series alloys is 14 kgf / mm ²
The strength of this value tends to be inferior to the shape fixability.

Therefore, the proof stress before pressing is 14 kgf.
/ Mm ² as much as possible and the shape fixability is improved,
All of the above problems can be solved if it is hardened in a coating baking process at about 175 ° C. for 30 minutes after the press working, and the proof stress and the tensile strength are remarkably increased and the dent resistance and the structural strength are improved. However, the existing alloy produced by the conventional method could not satisfy both the excellent shape fixability during press working and the dent resistance and structural strength after press working.

[0008]

Therefore, in the present invention, a detailed examination of the chemical composition and the thermomechanical treatment step will result in
In addition to improving moldability by suppressing age hardening at room temperature, by improving paint bake hardenability, we improve shape freeze resistance with low proof stress during pressing, and supply materials for press working with high strength after paint baking. To do.

[0009]

The present invention provides Si: 0.4.
.About.1.5%, Mg: 0.3 to 1.5%, or further Cu: 1.00 or less, Mn: 0.40% or less,
An alloy material containing Cr: 0.20% or less and V: 0.20% or less, and consisting of residual Al and unavoidable impurities is semi-continuously cast, and the obtained ingot is subjected to normal rolling and then a solution. After heat treatment, quenching, and pre-heat treatment of the material left to stand at room temperature for 2 to 200 hours in the temperature range of 50 to 120 ° C, the final heat treatment is performed within 60 minutes at room temperature and at 1 to 10 minutes at 180 to 250 ° C. A method for manufacturing an aluminum alloy material for forming, which is characterized by performing heat treatment.

The reasons for limiting each of the above constituent elements are as follows. Si: Necessary to obtain high strength, and Mg ₂ Si can be formed to obtain high strength. If it is less than 0.4%, the strength is low and sufficient strength cannot be obtained even if the coating is heated by baking. On the other hand, if it exceeds 1.5%, the yield strength after the completion of the final heat treatment is high, and the formability and shape fixability are poor.

Like Mg: Si, it is necessary to obtain high strength. If it is less than 0.3%, the strength is low and sufficient strength cannot be obtained by heating during baking of the coating. On the other hand, if it exceeds 1.5%, the yield strength after completion of the final heat treatment is high and the formability and shape fixability are poor.

Cu: The strength can be further increased by adding Cu. However, if added over 1.00%, the yield strength after completion of the final heat treatment is high, the formability and shape fixability are poor, and the corrosion resistance is poor.

Mn: By adding Mn, the strength can be further increased, and the crystal grains can be made finer.
Moldability is improved. However, if added in excess of 0.40%, the yield strength after completion of the final heat treatment is high and the formability and shape fixability are inferior, and the coarse intermetallic compound increases, so the formability decreases.

Cr: By adding Cr, the strength can be further increased, the crystal grains can be made finer, and the formability can be improved. However, if added in excess of 0.20%, the yield strength after completion of the final heat treatment is high and the formability and shape fixability are poor, and the coarse intermetallic compound increases, so the formability decreases.

V: By adding, the strength can be further increased, the anisotropy of mechanical properties can be reduced, the crystal grains can be made finer, and the moldability can be improved. However, if added over 0.20%, the yield strength after completion of the final heat treatment is high and the formability and shape fixability are poor.

Pre-heat treatment after standing at room temperature: 50 after standing at room temperature
By holding at a temperature of 120 ° C for 2 to 200 hours, nuclei for precipitation during coating baking are generated. This nucleation suppresses room temperature aging after the final heat treatment to maintain good formability, and facilitates hardening in a short time when heated to about 175 ° C. for coating baking. About 50 ℃
If the temperature is less than 120 ° C, there is no sufficient effect on the subsequent heat treatment and
If it exceeds, the yield strength increases and the formability decreases. If the pre-heat treatment time is shorter than 2 hours, the effect of the final heat treatment becomes small, and the paint bake hardenability is poor. Even if the pre-heat treatment time is more than 200 hours, the effect is the same, so there is little industrial effect or after the final heat treatment. The yield strength begins to increase and the formability deteriorates.

Final heat treatment after preheat treatment: 1 after preheat treatment
By performing a restoration process for 1 to 10 minutes at 80 ° C. or higher and 250 ° C. or lower, the G.I. Only the P zone is decomposed and the nuclei formed in the pretreatment are retained. This makes it easy to cure in a short time when heated to about 175 ° C. for nuclear coating baking.

Regarding the temperature, if it is less than 180 ° C., the bake hardenability is lowered, and if it exceeds 250 ° C., the yield strength is increased and the formability is poor and the bake hardenability is also lowered. There is no time limit at room temperature from the pre-heat treatment to the final heat treatment, and a good material can be obtained under any condition.

[0019]

[Examples] After semi-continuous casting of the alloys shown in Table 1, the surface of the casting surface was cut. Fe and Ti are impurities. Then 5
After the homogenization treatment at 40 ° C. for 24 hours, the temperature was lowered to 500 ° C., hot rolling was started at that temperature, and rolling was performed to a thickness of 6 mm.
Next, intermediate annealing was performed in a batch furnace at 350 ° C. for 1 hour. After cold rolling, a plate having a thickness of 1 mm was obtained. Furthermore, in a continuous annealing furnace, a solution heat treatment of 540 ° C. × 20 s was performed at a temperature rising rate of 500 ° C./min, and the solution was heated to 100 ° C.
After cooling at 00 ° C./min and leaving at room temperature for 48 hours, Table 2
The pre-heat treatment-final heat treatment under the conditions shown in FIG. The mechanical properties of these materials were evaluated after aging for 1 month at room temperature after the final heat treatment. In addition, the material is aged at room temperature for 1 month, and further subjected to a paint bake hardening treatment at 175 ° C.-30
After performing the heat treatment for min, the yield strength was examined.

[0020]

[Table 1]

[0021]

[Table 2]

Table 3 shows the evaluation results of the test materials. The judgment is
A product having a yield strength after 1 month room temperature aging of 13.5 kgf / mm ² or less is considered to have excellent shape fixability, and a product having an elongation of 28% or more and an Erichsen value of 9.5 mm or more is considered to have good moldability, 30 m at 175 ° C even after aging for 1 month at room temperature
A material with an increase in yield strength after heating of 5 kgf / mm ² or more is considered to have good paint bake hardenability, and a material with a yield strength after paint bake hardening of 13.5 kgf / mm ² or more is considered to be good dent material. Passed. Further, regarding the crystal grain size, 100 μm or less was determined to be acceptable in the observation of the plate surface.

[0023]

[Table 3] E _V: Erichsen value

All of Examples 1 to 12 of the present invention are within the scope of the claims, and excellent performances are obtained.

Since Comparative Example 13 has a smaller amount of Si and Comparative Example 14 has a smaller amount of Mg than the lower limit of the claimed range, the yield strength was low even in the 175 ° C.-30 min heat treatment after the final heat treatment.

Comparative Example 15 is the amount of Si, Comparative Example 16 is the amount of Mg and Cu, Comparative Example 17 is the amount of Mn and V, Comparative Example 1
In No. 8, the Cr content was larger than the upper limit of the claimed range and the proof stress exceeded 13.5 kgf / mm ^2. Therefore, the shape fixability was poor and the moldability was poor. In Comparative Example 19, the pre-heat treatment was shorter than the lower limit of the claimed range, and in Comparative Example 20, the pretreatment temperature feeling was lower than the lower limit of the claimed range, and thus the coating bake hardenability was poor. Comparative example 2
In No. 1, the pre-heat treatment time was longer than the upper limit of the claim range, and in Comparative Example 22, the pre-heat treatment temperature was higher than the upper limit of the claim range. Therefore, the proof stress was increased, the shape fixability was poor, and the moldability was low. It was In Comparative Example 23, the final bake hardenability was poor because the final heat treatment temperature was lower than the lower limit of the claimed range. In Comparative Example 24, the final heat treatment temperature was higher than the upper limit of the claimed range. Since the length was longer than the upper limit of the claimed range, the yield strength was increased, the shape fixability was poor, and the moldability was poor. In Comparative Example 26, the final heat treatment time was shorter than the lower limit of the claimed range, and thus the coating bake hardenability was low.

[0027]

EFFECTS OF THE INVENTION By using the present invention, various kinds of thin plate molding materials can be manufactured using conventional equipment, and further weight reduction can be promoted. Further, the present invention is
Although an example of a plate material has been mainly described, the principle of alloy material production is the same as in the case of other production methods such as extruded material, and therefore, it is applicable. Further, even if the coating baking temperature is lowered to 150 ° C. or lower in the near future, curing as high as 175 ° C. cannot be expected, but the production according to the present invention can obviously provide better performance than the conventional method. ..

Claims (2)

[Claims] 1. An alloy material containing Si: 0.4 to 1.5% (weight%, the same applies hereinafter), Mg: 0.3 to 1.5%, and a balance of Al and unavoidable impurities. Then, the obtained ingot is subjected to normal rolling, solution treatment, quenching, and pre-heat treatment of the material left at room temperature for 2 to 200 hours in a temperature range of 50 to 120 ° C., and then 180 to 250 ° C. 1 to 10
A method for producing an aluminum alloy material for forming, which comprises performing a final heat treatment for minutes. 2. Si: 0.4 to 1.5%, Mg: 0.3
.About.1.5%, further Cu: 1.00% or less, M
n: 0.40% or less, Cr: 0.20% or less, V: 0.
An alloy material containing 20% or less of one or more and semi-continuously casting an alloy material consisting of residual Al and unavoidable impurities, and subjecting the obtained ingot to normal solution rolling, solution treatment, quenching, and leaving at room temperature, A method for producing an aluminum alloy material for forming, which comprises performing a preheat treatment at a temperature range of 50 to 120 ° C. for 2 to 200 hours and then performing a final heat treatment at 180 to 250 ° C. for 1 to 10 minutes.