JP3498942B2 - Aluminum alloy plate with excellent ridging mark resistance and method for evaluating the occurrence of ridging mark - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al-Mg-Si based aluminum alloy plate which has excellent resistance to ridging marks and is suitable for use as a panel for transportation machines such as automobiles, railway vehicles and aircraft.

[0002]

2. Description of the Related Art A 6000 series (Al-Mg-Si series) aluminum alloy sheet is relatively excellent in corrosion resistance and formability at room temperature, and high strength can be obtained by artificial aging treatment. Suitable for applications that require thinning. Al-Mg-Si alloy plate material is usually
After homogenization treatment, hot rolling, then intermediate annealing if necessary, then cold rolling to a plate material of a predetermined thickness, solution heat treatment and quenching treatment, and then skin pass if necessary. Manufactured by stretching, etc.

However, when an Al--Mg--Si alloy plate material is molded, a ridging mark is formed on the surface of the plate as described in JP-A-7-228956 or JP-A-8-232052. There is a problem that the surface roughness called ". When this ridging mark occurs, it cannot be used as a poor appearance for applications such as automobile outer panel, which requires an extremely beautiful surface, and passenger aircraft fuselage outer panel. When it is performed, it becomes particularly conspicuous. Therefore, the process may proceed to the coating process without being noticed after the molding process, and may be recognized for the first time after coating. In other words, it has the troublesome characteristic that it may appear only after it is made into a product.

The above-mentioned JP-A-7-228956 and JP-A-8-232052 relate to a method for preventing the occurrence of ridging marks in an Al-Mg-Si alloy plate material, the former being 350 to 450 after homogenization treatment. After cooling to a temperature of ℃, hot rolling is started, hot rolling is finished at a temperature of 200 to 300 ° C., intermediate annealing is performed if necessary, and then cold rolling, solution treatment and quenching treatment are performed. That is, the latter starts the hot rolling after cooling to a temperature of 450 ° C. or lower after the homogenization treatment, finishes the hot rolling at a temperature of 200 to 350 ° C., and if necessary, an intermediate temperature of 350 to 420 ° C. After annealing, cold rolling, solution hardening, and final heat treatment are performed.In each case, the hot rolling temperature is set low, and at the same time, the processing conditions of other steps are strictly controlled. , By that It is that you try to prevent the occurrence of ridging marks Te.

[0005]

On the other hand, the present inventors have
First, Japanese Patent Application No. 9-287906 and Japanese Patent Application No. 9-36772.
In No. 3, Si: 0.2 to 1.8%, Mg: 0.2
It was found that the occurrence of ridging marks can be prevented by limiting the size of the macrostructure or the degree of integration of the cube orientation of the Al-Mg-Si-based aluminum alloy plate for forming containing 1 to 1.6% to a predetermined range. It was However, statistically processing the macrostructure morphology or the degree of cube orientation integration and estimating the variation in the characteristics of the entire product (for example, the total coil length) from that is not practical in terms of time and cost in the actual manufacturing line. Not at all.

In that respect, if the characteristics of a large number of samples on an aluminum alloy plate can be measured in a short time and evaluated with high reliability, for example, if it is determined that the product plate is likely to cause ridging marks, the factory Shipments from can be suspended. Further, such a product plate can be diverted to a member which is not subjected to a large tensile deformation at the time of forming and shipped, and the quality and the yield can be improved. And the regulation of the size of the macrostructure or the degree of integration of the cube orientation of the prior application is a necessary condition for preventing the occurrence of ridging marks, but even those satisfying the above regulation can be used for molding and electrodeposition coating. Ridging marks may be found in rare cases later, which may not have been a sufficient condition. Therefore, there is a demand for a more reliable index that can evaluate the occurrence of ridging marks. That is, an object of the present invention is to make it possible to surely evaluate whether or not a ridging mark is generated in an aluminum alloy plate in a short time.

[0007]

The present inventors have found that Al-M
If a g-Si-based aluminum alloy is hot-rolled under specific temperature and strain rate conditions and the microstructure after hot-rolling is set as equiaxed recrystallized grains, it is necessary without or without intermediate annealing. According to the above, cold rolling is performed, and then solution treatment and quenching are performed, and when a microstructure is a product plate having equiaxed recrystallized grains, it is found that ridging marks can be prevented from occurring on the product plate. I applied for a patent earlier. The equiaxed recrystallized grains mean that the average aspect ratio of the recrystallized grains observed is in the range of 1 to 3 in both the plane parallel to the plate surface and the plane perpendicular to the rolling direction. means. Specifically, the following conditions are satisfied. 1 ≦ dL / dLT ≦ 3 1 ≦ dL / dST ≦ 3 dL; particle size measured in the length direction of the plate dLT; particle size measured in the width direction of the plate dST; particle size measured in the plate thickness direction

After that, hot rolling and, if necessary, intermediate annealing are carried out, followed by cold rolling, and then solution treatment and quenching treatment, and an Al-Mg-Si system aluminum alloy having a microstructure as equiaxed recrystallized grains. As a result of various studies on the characteristics of the product plate, it was found that there is a certain relationship between the presence or absence of ridging marks and the ear height generated when this product plate is formed into a cup shape. . The present invention was made based on this finding, and Si: 0.2 to 1.8.
%, Mg: 0.2 to 1.6%, Al-Mg-Si-based aluminum alloy sheet hot-rolled and subsequently annealed if necessary, cold-rolled, and then solution-quenched The microstructure is composed of equiaxed recrystallized grains, and the ratio of the punch having a diameter of 40 mm (shoulder radius 3 mm) and the gap between the punch and the die to the Al alloy plate thickness is 1.3 to 1.
When using a die in the range of 4 to form a cup shape under the conditions of a wrinkle pressing force of 150 kgf, a forming speed of 60 mm / min, and a lubricating oil # 700 used, the cup ear ratio is -4% or more. To do. The equiaxed meaning is the same as that shown above.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The ears generated when an Al-Mg-Si based aluminum alloy plate is formed into a cup shape are 0 °, 90 ° and 18 ° relative to the rolling direction, which is called a minus ear.
The ears that occur in the 0 ° and 270 ° directions and the ears that are called the positive ears are 45 °, 135 °, 225 ° and 315 with respect to the rolling direction.
It is roughly divided into ears that occur in the ° direction. And ear rate (%)
Is generally defined as follows. Ear ratio (%) = {(average value of plus ear height)-(average value of minus ear height)} x 100 / (average ear height)

As shown in the above-mentioned application, ridging in an Al-Mg-Si-based aluminum alloy sheet which has been hot rolled and subsequently subjected to intermediate annealing if necessary, cold rolled, and then solution heat treated and quenched. The presence or absence of the mark is related to the degree of integration of the cube orientation. If the degree of integration of the cube orientation is high, the anisotropy of deformation and the degree of deformation will differ between the accumulation area and the non-integration area of the cube orientation during molding, which will cause ridging marks. By using the ear rate that more directly represents the anisotropy of the deformation that occurs, it may be possible to more accurately evaluate the presence or absence of ridging marks. From this point of view, the present inventors hot-rolled and subsequently subjected to intermediate annealing, followed by cold-rolling, and then solutionizing and quenching the Al-Mg-Si-based aluminum alloy in which the microstructure was equiaxed recrystallized grains. When the plate was formed into a cup shape under a constant processing condition (in the above “”) and examined, the ear rate defined above was −4%.
It was found that ridging marks were reliably prevented from occurring in the above plates. In addition, since the ear rate when forming into a cup shape varies depending on the processing conditions, the processing conditions must be constant.

An Al-Mg-Si-based aluminum alloy sheet having a microstructure with equiaxed recrystallized grains after solution rolling and quenching after hot rolling and subsequent intermediate annealing if necessary and cold rolling is prepared as described above. When processed into a cup shape under the conditions described above and the ear rate at that time is within the above range, the ridging mark resistance of the product plate is guaranteed. However, when the ear rate is outside the above range,
Ridging mark resistance is not completely guaranteed. Therefore,
In this case, measures such as turning the product plate to a molding processing application at a level where ridging marks are not generated or an application where ridging marks may be generated are taken. In any case, ear height measurement is simple and can be performed in a short time, so that prompt measures can be taken. Note that the conditions for forming into a cup shape do not necessarily have to be the same as the above "". However, it is necessary to clarify the relationship between the ear rate and the occurrence of ridging marks when molding is performed under the conditions.

The above Al-Mg-Si system aluminum alloy sheet is subjected to homogenizing heat treatment, hot rolling, intermediate annealing if necessary, and then cold rolling, solution treatment and quenching. The preferable conditions of are as follows. In the hot rolling, the hot rolling finish temperature is set to the recrystallization temperature or higher, and the strain rate in the final pass of the hot rolling is 7,000 to 2
0000% / sec, and immediately after the hot rolling is finished, it is rolled up to obtain a hot rolled sheet having a microstructure of equiaxed recrystallized grains.
Here, the strain rate is defined as: strain rate = rolling ratio (%) by the final roll / time (second) that the plate passes through the final roll. More specifically, the rolling start temperature is set to 450
C. or higher and the homogenization treatment temperature (eg, 470 to 540.degree. C.) or lower, and the hot rolling end temperature is the recrystallization temperature or higher, eg, 3
The temperature is set to 00 to 450 ° C. When finishing hot rolling is performed in multiple stages, the minimum strain rate of continuous hot rolling should be 2% or more of the strain rate during the final pass, and recrystallization should be repeated during finishing hot rolling. In this case, the recrystallized grains become finer, and it is more effective for preventing ridging marks on the product plate. The preferred recrystallized grain size at this stage is 45
μm or less. Further, in order to cause recrystallization in the finish hot rolling, it is desirable that the rolling rate of each pass is 40% or more.

The intermediate annealing conditions are as follows: heating rate: up to 400 ° C .: 30 ° C./min to 500 ° C./sec, 400 to 500 ° C .: 10
~ 100 ° C / min, holding condition: 500 to 580 ° C x 10 seconds to 10 minutes, cooling rate: 30 ° C from holding temperature to 50 ° C
/ Min or more When performing the intermediate annealing, the rolling end temperature of the hot rolling can be set lower than the temperature range described in the previous hot rolling, for example, 150 to 300 ° C. Further, the strain rate at the final pass of hot rolling can be set as low as 5000 to 20000% / sec. The cold rolling rate is preferably 50% or more in order to reduce the grain size of equiaxed recrystallized grains of the aluminum alloy plate after the solution treatment to 45 μm or less. This prevents the occurrence of orange peel during molding. When the above-described intermediate annealing is performed, the solid solubility is high, the work hardening degree in cold rolling is high, and the recrystallized grains in the solution treatment are likely to be refined. Therefore, a cold rolling rate of 30% or more is sufficient. The preferable solution treatment conditions are that the heating rate up to 400 ° C. is 30 ° C./min or more, and 400 to 530 ° C. is 10
C./minute or more, 530 to 580.degree. C., 10 seconds to 10 minutes. For heating, in order to increase the heating rate, it is possible to use a glass nitrate furnace, a continuous annealing furnace, an induction heating furnace, or the like. Quenching is performed from the holding temperature to a temperature of 70 to 140 ° C. or lower for 30
℃ / min or more cooling rate or from the holding temperature 70 ~ 1
It may be carried out at a temperature of 40 ° C. at a cooling rate of 30 ° C./min or more, and may be kept as it is at a temperature of 70 to 140 ° C. for 0.5 to 48 hours.

In terms of component composition, the present invention provides S
i: 0.2 to 1.8%, Mg: 0.2 to 1.6%, an aluminum alloy containing the balance Al and unavoidable impurities, and (1) Zn: 0. 005
.About.1.0%, Cu: 0.005 to 1.0%, Ti: 0.
Any one kind or two kinds or more of 001 to 0.1%, (2)
B: 1 to 300 ppm, Be: 0.1 to 100 ppm, one or two, (3) Mn: 1.0% or less, Cr: 0.
0.01% to 1.5% in total of 3% or less, Zr: 0.15% or less, V: 0.15% or less, or one or more types.
%, The aluminum alloy containing any of the above (1) to (3) or a combination thereof, Si: 0.2 to
Al-M containing 1.8% and Mg: 0.2 to 1.6%
It can be applied to all g-Si based aluminum alloys. Al-
The reason for defining the composition of the Mg-Si alloy as described above is as follows.

Mg: Mg is an element that imparts strength together with Si, but if it is less than 0.2%, sufficient strength cannot be obtained by artificial aging, while if it exceeds 1.6%, the formability deteriorates. Therefore, the Mg content is in the range of 0.2 to 1.6%. Si: Si is an element that gives strength together with Mg, but if it is less than 0.2%, sufficient strength cannot be obtained by artificial aging, while if it exceeds 1.8%, the elongation becomes low and the formability deteriorates. To do. Therefore, the Si content is set to the range of 0.2 to 1.8%. In order to obtain high strength by artificial aging, M
It is desirable that the content ratio of g and Si be Si / Mg ≧ 0.65.

Zn: Zn is MgZn during artificial aging
₂ is finely and densely deposited to realize high strength.
However, if less than 0.005%, sufficient strength cannot be obtained,
On the other hand, if it exceeds 1.0%, the corrosion resistance is significantly reduced.
The content is in the range of 0.005 to 1.0%. Cu: Cu precipitates Mg ₂ Si finely and at high density during artificial aging, and realizes high strength. However, 0.0
If it is less than 05%, it has no effect, while if it exceeds 1.0%, the corrosion resistance and weldability are remarkably reduced, so the content is less than 0.1%.
The range is 005 to 1.0%. Ti: Ti is an element added for refining the crystal grains of the ingot and improving the formability, but if it is less than 0.001%, it has no effect, while if it exceeds 0.1%, it is added. Coarse crystallized products are formed and the formability is reduced. For this reason,
The Ti content is in the range of 0.001 to 0.1%.

B: B is an alloy added in order to refine the crystal grains of the ingot and improve the formability like Ti, but if it is added in an amount of less than 1 ppm, B has no effect, and 300 ppm is added.
If it is contained in an amount exceeding the above range, a coarse crystallized substance is formed and the formability is deteriorated. Therefore, the B content is in the range of 1 to 300 ppm. Be: Be is contained in an amount of 0.1 ppm or more, if necessary, in order to prevent reoxidation of the molten aluminum in the air. However, when the content exceeds 100 ppm, the material hardness increases and the formability decreases, so the Be content is 0.1 to 100.
The range is ppm.

Mn, Cr, Zr, V: These components are Al ₂₀ Cu ₂ during homogenizing heat treatment and subsequent hot rolling.
Mn ₃ , Al ₁₂ Mg ₂ Cr, Al ₃ Zr, Al ₂ Mg
₃ Dispersed particles such as Zn ₃ are generated. Since these dispersed particles have an effect of preventing grain boundary movement after recrystallization, fine crystal grains can be obtained. However, excessive addition easily forms a coarse insoluble intermetallic compound during melting and casting, which becomes a starting point of fracture during molding and causes deterioration of moldability. Further, excessive addition of Zr tends to make the microstructure needle-like, and deteriorates fracture toughness and fatigue characteristics in a specific direction, and further formability. Therefore, the addition amounts of Mn, Cr, Zr, and V are 1.0%, 0.30%, 0.15%,
0.15% or less, and 1.5% or less in total.

Fe: Fe contained as an impurity is Al
₇ Cu ₂ Fe, Al ₁₂ (Fe, Mn) ₃ Cu ₂ , (F
e, Mn) Al _{6 and} other crystallized products are formed. These crystallized substances are harmful to the fracture toughness, fatigue properties and forming workability, and when the Fe content exceeds 0.5%, the fracture toughness, fatigue properties and formability are markedly reduced. The amount is 0.5% or less. Note that, as the crystallized substance, there are soluble substances such as Al ₂ Cu ₂ Mg, Al ₂ Cu ₂ , and Mg ₂ Si other than Fe-based substances, and these are sufficiently re-formed in the Al matrix by solution treatment and quenching. It is desirable to form a solid solution. Other impurities: Ni is limited to 0.05% or less.

[0020]

EXAMPLES Examples of the present invention will be described below. (Example 1) Mg: 0.5%, Si: 1.2%, Mn:
0.05%, Fe: 0.15%, Cr: 0.01%, N
i: 0.001%, Zn: 0.03%, Cu: 0.03
%, Ti: 0.06%, Bi: 10 ppm, Be: 30
An aluminum alloy containing ppm and the balance Al and impurities is melt cast to form a 480 mm thick ingot, and then 5
After performing homogenizing heat treatment at 40 ° C. × 8 hr, rough hot rolling (reverse) and finish continuous hot rolling (4 tandem)
A 3.5 mm-thick plate was wound around a coil, and with or without intermediate annealing, a 1.2 mm-thick plate was cold-rolled, followed by solution treatment and quenching. Solution annealing and quenching are continuous annealing up to 400 ° C with an average heating rate of 300 ° C
After heating at 550 ° C./minute, it was further heated to 550 ° C. for about 1 minute, and then cooled to 30 ° C. by forced air cooling at an average cooling rate of 40 ° C./minute. The processing conditions of each step are shown in Table 1.

[0021]

[Table 1]

Samples were sampled from this plate, and the characteristics of each material were measured as follows. Micro-crystal grains; recrystallized grain size is the sampled plate material, L-direction crystal grain size (dL) and LT-direction crystal grain size (dLT) are on the L-LT surface (surface layer portion is polished by 0.1 mm). , The crystal grain size (dST) in the ST direction was mechanically polished on the L-ST surface and then electrolytically etched (tetrafluoroboric acid: water = 15: 400, voltage 30V, solution temperature 20 to 3).
The etching was performed at 0 ° C. for 60 to 90 seconds, and evaluated by a line intercept method (according to JIS H0501) using an optical microscope (using a polarizing plate, magnification 50 times). Tensile properties: JIS aged after quenching the quenched plate at room temperature for 3 months
In accordance with -Z2241, a JIS No. 5 test piece was used in a room temperature atmosphere at a tensile speed of 5 mm / min in the LT direction (90 ° direction with respect to the rolling direction).

Evaluation of ridging mark: JIS from product plate
A No. 5 test piece (longitudinal direction was perpendicular to the rolling direction, parallel part length 60 mm) was prepared, and the parallel part was buffed to a mirror surface. 15% tensile deformation (cage length 50mm,
After the deformation speed was 5 mm / min), the degree of unevenness on the plate surface at the parallel portion was visually observed, and when the ridging mark was generated, it was evaluated as x, and when the ridging mark was difficult to determine, it was evaluated as ◯.

As can be seen from Table 1, the sample No. with the ear rate of -4% or more was obtained. No ridging marks were generated in 1 to 3 and 6. Furthermore, the size of recrystallized grains is 45
No. No orange peel was generated in 1 to 3. On the other hand, in the case of No.
Ridging marks were generated in Nos. 4 and 5.

[0025]

EFFECTS OF THE INVENTION According to the present invention, Al is hot rolled and subsequently subjected to intermediate annealing if necessary, cold rolled, and then solution heat treated and quenched to obtain Al having an equiaxed recrystallized microstructure. −
By defining the ear rate that occurs when the Mg-Si-based aluminum alloy plate is formed into a cup shape, the ridging mark resistance of the product plate can be guaranteed.
Further, since it is possible to reliably evaluate the presence or absence of ridging marks on the product plate in a short time, the evaluation result is immediately reflected in the manufacturing process, and a situation in which a large amount of aluminum alloy plates with poor ridging mark resistance are manufactured is prevented. It becomes possible.

─────────────────────────────────────────────────── --Continued front page (56) References JP-A-5-9674 (JP, A) JP-A-56-105461 (JP, A) JP-A-63-109146 (JP, A) JP 2003-518192 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C22C 21/00-21/18 C22F 1/04-1/057

Claims (5)

(57) [Claims] 1. Si: 0.2 to 1.8% (mass%,
The same shall apply hereinafter), Mg: 0.2-1.6%, Al-Mg-Si hot-rolled and subsequently subjected to intermediate annealing if necessary, then cold-rolled, and then solution-treated and quenched. -Based aluminum alloy plate with a microstructure consisting of equiaxed recrystallized grains, and a punch with a diameter of 40 mm (shoulder radius 3
mm) and the ratio of the gap between the punch and the die to the thickness of the Al alloy plate is 1.3 to 1.4, and the wrinkle holding force is 15
0 kgf, molding speed 60 mm / min, lubricating oil # 70 used
An aluminum alloy plate having excellent ridging mark resistance, which has a cup selvage of -4% or more when formed into a cup shape under the condition of "0". 2. The grain size of equiaxed recrystallized grains is 45 μm or less.
The aluminum alloy plate having excellent resistance to ridging marks according to claim 1, wherein 3. An Al-Mg-Si based aluminum alloy further comprises (1) Zn: 0.005-1.0%, Cu:
0.005 to 1.0%, Ti: 0.001 to 0.1%, one or more, (2) B: 1 to 300 ppm, B
e: 0.1 to 100 ppm, one or two, (3) M
n: 1.0% or less, Cr: 0.3% or less, Zr: 0.1
5% or less, V: 0.15% or less, and a total of 0.01 to 1.5% or more (1) to (3).
Any of the above or a combination thereof is contained, and an aluminum alloy plate from which a plate material for forming having excellent ridging mark resistance according to claim 1 is obtained. 4. An aluminum alloy plate for use in automobile panels, which is capable of obtaining a plate material for forming having excellent resistance to ridging marks according to any one of claims 1 to 3. 5. Si: 0.2 to 1.8%, Mg: 0.2
Al-Mg-Si-based aluminum alloy plate containing ~ 1.6%, hot-rolled and subsequently subjected to intermediate annealing if necessary, cold-rolled, and then solution-treated and quenched.
Ear ratio when drawn into a cup shape under specified processing conditions
Clarify in advance the relationship between the occurrence of ridging marks and
The Al-Mg-Si based aluminum alloy plate
Under processing conditions, draw forming into a cup shape and measure its ear rate,
The Al-Mg-Si-based aluminum based on the above relationship
Evaluate the occurrence of ridging marks for aluminum alloy plates
Al-Mg-Si-based aluminum alloy
Evaluation method for the occurrence of ridging marks on the gold plate .