JP2012025976A - METHOD OF MANUFACTURING Al-Mg-Si BASED ALUMINUM ALLOY PLATE EXCELLENT IN COAT BAKING HARDENABILITY AND FORMABILITY, AND HAVING AGING SUPPRESSION EFFECT AT ROOM TEMPERATURE - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an Al-Mg-Si based aluminum alloy plate which is excellent in coat baking hardenability and formability, and has aging suppression effect at room temperature.SOLUTION: The Al-Mg-Si based aluminum alloy plate has a composition containing, by mass%, 0.5-2.0% of Si, 0.2-1.5% of Mg, and further containing one or more kinds selected from Cu, Zn, Fe, Mn, Cr, V, Zr, Ti, and B and the balance Al with unavoidable impurities. The method for manufacturing the Al-Mg-Si based aluminum alloy plate includes: (1) a quenching step of performing solution treatment at a temperature of 480°C or more and 580°C or less, and cooling the alloy plate to a quenching temperature of 50°C or less at a cooling speed of 2°C/second or more; (2) a first step preliminary aging step of heating the alloy plate to the first step preliminary aging temperature of 50°C or more and 100°C or less at a temperature raising speed of 2°C/second or more after holding it at the quenching temperature for one hour or less, and holding it at the first step preliminary aging temperature for one minute or more and 10 hours or less; (3) a second step preliminary aging step of heating the alloy plate to the second preliminary aging temperature being the temperature 10°C higher than the first step preliminary aging temperature or more and 140°C or less at the temperature raising speed of 1°C/hour or more, and holding it at the second step preliminary aging temperature for one minute or more and 10 hours or less.

Description

  The present invention relates to a method for producing an Al—Mg—Si-based aluminum alloy plate that is excellent in paint bake hardenability and formability, has an effect of suppressing aging at room temperature, and is particularly suitable for an automobile outer plate.

  In recent years, as a measure against global warming caused by exhaust gas or the like, a reduction in weight of the vehicle body has been demanded in order to improve the fuel efficiency of automobiles. For this reason, the application of aluminum alloy plates is increasing instead of steel plates that have been used conventionally as materials for automobile bodies, particularly automobile outer plates.

  Al-Mg-based aluminum alloys and Al-Mg-Si-based aluminum alloys are used as aluminum alloy materials for automobile outer plates, and among these, Al-Mg-Si-based aluminum alloys that are heat-treatable alloys are suitable. It has excellent characteristics as compared with an Al-Mg-based aluminum alloy for automobile outer panels in that it exhibits paint bake hardenability by producing under conditions.

  However, Al-Mg-Si-based aluminum alloys, on the other hand, exhibit room temperature age-hardening properties that are not found in Al-Mg-based aluminum alloys, which are non-heat-treatable alloys. In order to apply Al-Mg-Si based aluminum alloy as a material for automotive outer panels, the conflicting properties of paint bake hardening and room temperature aging suppression are difficult to crack during processing (bending). There is a problem that they must be compatible.

  In Al-Mg-Si-based aluminum alloys, attempts to achieve both contradictory properties of paint bake hardening and room temperature aging suppression have been studied so far, and devices such as solution treatment conditions and preliminary aging conditions have been studied. However, these methods are not sufficient to make both characteristics completely compatible, and further improvements are required.

JP-A-8-74014 JP 2007-239005 A JP 2002-206152 A

  In the case of applying the Al-Mg-Si-based alloy as an automotive outer plate, the present invention eliminates the problem that cracking is likely to occur during press molding or hem processing (bending processing). It was made as a result of repeated testing and examination on the relationship between solution treatment conditions, preliminary aging conditions and formability, and its purpose is Al with excellent bake hardenability and formability and having an effect of suppressing room temperature aging The object is to provide a method for producing a Mg—Si based aluminum alloy plate.

  The method for producing an Al—Mg—Si based aluminum alloy plate having excellent paint bake hardenability and formability according to claim 1 for achieving the above object and having an effect of suppressing room temperature aging is expressed by mass%, and Si: 0.00. 5 to 2.0%, Mg: 0.2 to 1.5%, Cu: 1.0% or less, Zn: 0.5% or less, Fe: 0.5% or less, Mn: 0.00%. 1% or less of 3% or less, Cr: 0.3% or less, V: 0.2% or less, Zr: 0.15% or less, Ti: 0.1% or less, B: 0.005% or less (1) Solution treatment at a temperature of 480 ° C. or higher and 580 ° C. or lower is performed on a plate material of an Al—Mg—Si based aluminum alloy having a composition comprising the balance Al and inevitable impurities. A quenching step of cooling to a quenching temperature of less than 50 ° C. at a cooling rate of (2) the quenching temperature And then heated to a first stage pre-aging temperature of 50 ° C. or more and 100 ° C. or less at a temperature rising rate of 2 ° C./min or more, and at the first stage pre-aging temperature for 1 minute or more and 10 hours. The first stage pre-aging process for holding the time within the following range, and (3) the second stage pre-aging process at a temperature rising rate of 1 ° C./hour or more and a temperature higher by 10 ° C. than the first stage pre-aging temperature and not more than 140 ° C. Heating to a temperature, the second stage pre-aging temperature is maintained at the second stage pre-aging temperature for 1 minute to 10 hours, and the treatment is performed. In the following description, all alloy components are indicated by mass%.

  The method for producing an Al—Mg—Si based aluminum alloy sheet having excellent paint bake hardenability and formability according to claim 2 and having an effect of suppressing aging at room temperature is the first stage pre-aging step of (2) in claim 1. After that, it is cooled to a temperature not lower than 50 ° C. and lower than the first stage pre-aging temperature, and the second stage pre-aging step (3) is performed.

  The method for producing an Al—Mg—Si based aluminum alloy plate having excellent paint bake hardenability and formability according to claim 3 and having an effect of suppressing aging at room temperature is the first-stage preliminary aging step of (2) in claim 1. Thereafter, the second preliminary aging step (3) is performed without cooling.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the Al-Mg-Si type aluminum alloy plate which is excellent in paint bake hardenability and a moldability, has a room temperature aging suppression effect, and is especially suitable for motor vehicle outer plates is provided.

The significance and reasons for limitation of the alloy components in the present invention will be described.
Si:
Si is an alloy component necessary for obtaining paint bake hardenability, and functions to increase the strength by forming an Mg—Si compound. The preferable content of Si is in the range of 0.5 to 2.0%, and if it is less than 0.5%, the paint baking and curing is sufficient with the paint baking process (heat treatment held at 150 to 200 ° C. for 20 minutes). If it exceeds 2.0%, aging at room temperature proceeds remarkably, and press formability and bending workability deteriorate. A more preferable content of Si is in the range of 0.8 to 1.2%.

Mg:
Similar to Si, Mg is an alloy component necessary for obtaining paint bake hardenability, and functions to increase the strength by forming an Mg-Si compound. The preferred Mg content is in the range of 0.2 to 1.5%, and if it is less than 0.2%, the paint baking and curing is sufficient with a paint baking process (heat treatment held at 150 to 200 ° C. for 20 minutes). If it exceeds 1.5%, aging at room temperature proceeds remarkably, and press formability and bending workability deteriorate. A more preferable content of Mg is in the range of 0.3 to 0.7%.

Cu:
Cu functions to increase strength and improve formability. The preferred Cu content is in the range of 1.0% or less, and if it exceeds 1.0%, aging at room temperature proceeds remarkably, press formability and bending workability deteriorate, and corrosion resistance also deteriorates.

Zn:
Zn functions to improve the zinc phosphate processability during the surface treatment. The preferable content of Zn is in the range of 0.5% or less, and if it exceeds 0.5%, the corrosion resistance deteriorates.

Fe, Mn, Cr, V, Zr:
The above elements function to increase the strength and refine the crystal grains to prevent rough skin during molding. The preferred contents are Fe 0.5% or less, Mn 0.3% or less, Cr 0.3% or less, V 0.2% or less, and Zr 0.15% or less. As a result, press formability and bending workability deteriorate.

Ti, B:
Ti and B function to refine the cast structure and improve formability. Preferable contents are in the range of Ti 0.1% or less and B 0.005% or less. When the upper limit is exceeded, a coarse intermetallic compound is generated, and press formability and bending workability deteriorate.

  The production process of the Al—Mg—Si alloy having the above composition will be described. The Al—Mg—Si based aluminum alloy having the above composition is melted and cast, and the resulting ingot is homogenized according to a conventional method. It cold-rolls to predetermined thickness, performing a process, hot rolling, and intermediate annealing as needed.

Solution treatment, quenching process:
The cold-rolled Al—Mg—Si aluminum alloy sheet is first subjected to solution treatment and quenching (T4 treatment) in order to obtain paint bake hardenability. The solution treatment is performed in a temperature range of 480 ° C. or higher and 580 ° C. or lower. If it is less than 480 degreeC, the solid solution of Si and Mg will become inadequate, and paint bake hardenability will fall. If the temperature exceeds 580 ° C., the solid solution of Si and Mg is sufficient, but there is a risk of local melting, and a stable plate material cannot be produced.

  The quenching after the solution treatment is performed by rapidly cooling from the solution treatment temperature to a quenching temperature of less than 50 ° C. at a cooling rate of 2 ° C./second or more, preferably 10 ° C./second or more. When the cooling rate is less than 2 ° C./second, press formability and bending workability are deteriorated due to the precipitation of Si or Mg—Si compounds at the grain boundaries during cooling. Moreover, the solid solution of Si and Mg becomes insufficient, and the paint bake hardenability is lowered. When the temperature during quenching is 50 ° C. or higher, insufficient quenching occurs, and sufficient paint bake hardenability cannot be obtained.

First stage preliminary aging process:
The first-stage preliminary aging step is the first-stage preliminary aging at 50 ° C. or higher and 100 ° C. or lower at a temperature rising rate of 2 ° C./min or higher after holding at the quenching temperature for a time within 1 hour, preferably within 15 minutes. It is a processing step of heating to an aging temperature and holding the first stage pre-aging temperature for a period of 1 minute to 10 hours.

  The holding time at the quenching temperature needs to be within 1 hour. If it exceeds 1 hour, age hardening proceeds and sufficient paint bake hardenability cannot be obtained. The first stage pre-aging is heated from the quenching temperature to the first stage pre-aging temperature of 50 ° C. or more and 100 ° C. or less at a temperature increase rate of 2 ° C./min or more, preferably 10 ° C./min or more, and this temperature is 1 minute. This is carried out by holding the time within 10 hours. If the first stage pre-aging temperature is less than 50 ° C., the pre-aging effect cannot be obtained, and sufficient paint bake hardening cannot be achieved. When the first stage pre-aging temperature exceeds 100 ° C., a sufficient pre-aging effect is obtained, but even if the second stage pre-aging described below is performed, the room temperature aging suppressing effect cannot be obtained.

  When the rate of temperature increase from the quenching temperature to the first stage pre-aging temperature is less than 2 ° C./min, age hardening proceeds and sufficient paint bake hardenability cannot be obtained. If the holding time at the first stage pre-aging temperature is less than 1 minute, the preliminary aging effect in the second stage pre-aging is sufficiently obtained, but the room temperature aging suppressing effect cannot be obtained. On the other hand, if the holding time exceeds 10 hours, age hardening proceeds and the proof stress value becomes too high, so that press formability and bending workability are deteriorated.

  After the first stage pre-aging process, the second stage pre-aging is performed by raising the temperature directly from the first stage pre-aging temperature to the second stage pre-aging temperature and holding it at the second stage pre-aging temperature without cooling. It is also possible to perform second stage pre-aging after cooling. When cooling from the first stage pre-aging temperature, it is necessary to cool from the first stage pre-aging temperature to a temperature not lower than 50 ° C. and lower than the first stage pre-aging temperature. When cooled to a temperature of less than 50 ° C., age hardening proceeds during cooling and sufficient paint bake hardenability cannot be obtained.

Second stage preliminary aging process:
The second stage pre-aging step is at a temperature increase rate of 1 ° C./hour or more, preferably 10 ° C./hour or more, and a temperature higher by 10 ° C. than the first stage pre-aging temperature but not more than 140 ° C. The second stage pre-aging temperature is maintained and the second stage pre-aging temperature is maintained for 1 minute to 10 hours.

  If the second stage pre-aging temperature is less than 10 ° C higher than the first stage pre-aging temperature, sufficient second stage pre-aging effect cannot be obtained, and excellent paint bake hardenability and room temperature aging suppression effect are obtained. It can no longer be obtained. That is, the difference between the case where the second stage preliminary aging is performed and the case where the second stage preliminary aging is not performed is not observed in the bake hardenability and the room temperature aging suppressing effect. On the other hand, if the second stage preliminary aging temperature exceeds 140 ° C., age hardening proceeds and the proof stress value becomes too high, so that press formability and bending workability deteriorate.

  When the rate of temperature increase from the first stage pre-aging temperature to the second stage pre-aging temperature is less than 1 ° C./hour, a sufficient second stage pre-aging effect cannot be obtained, and excellent paint bake hardenability and room temperature. Aging suppression effect cannot be obtained. If the holding time at the second stage pre-aging temperature is less than 1 minute, sufficient second stage pre-aging effect cannot be obtained, and excellent paint bake hardenability and room temperature aging inhibiting effect cannot be obtained. On the other hand, if the holding time exceeds 10 hours, age hardening proceeds and the proof stress value becomes too high, so that press formability and bending workability are deteriorated.

  Assuming actual production in the factory, the solution treatment, the quenching process, the first stage and the second stage pre-aging process are usually preferably performed using a continuous annealing furnace. When the preliminary aging time exceeds 1 hour, it is preferable to perform preliminary aging by winding the plate material as a coil. In this case, the plate material after the first stage pre-aging is wound as a coil, and when this coil is cooled to a temperature of 50 ° C. or more and lower than the first stage pre-aging temperature before the second stage pre-aging process, 30 ° C. / It is necessary to cool at a cooling rate of less than an hour. When the coil is cooled at a cooling rate exceeding 30 ° C./hour, it is difficult to cool the entire coil uniformly, the pre-aging state in the coil is not uniform, and stable paint bake hardenability. This is because the room temperature aging suppression effect cannot be obtained.

  In the present invention, the Al—Mg—Si based aluminum alloy material having the above alloy composition is performed as necessary after the solution treatment, quenching step, first stage pre-aging step, and first stage pre-aging step. To produce an Al—Mg—Si-based aluminum alloy sheet that is excellent in paint bake hardenability and formability and has an effect of suppressing aging at room temperature by processing in a series of steps consisting of a cooling step and a second stage pre-aging step. Can do.

  Examples of the present invention will be described below in comparison with comparative examples to demonstrate the effects. In addition, these Examples show one embodiment of this invention, and this invention is not limited to these.

Example 1 and Comparative Example 1
An aluminum alloy having the composition shown in Table 1 (invention materials: A to J, comparative materials: KT) was ingoted by DC casting, and the resulting ingot was homogenized at 550 ° C. for 24 hours, It was cooled to room temperature, then reheated to 400 ° C. to start hot rolling, and rolled to a thickness of 2.0 mm. The end temperature of hot rolling was 250 ° C. Subsequently, cold rolling was performed to 1.0 mm. In Table 1, those outside the conditions of the present invention are underlined.

  The obtained cold-rolled material was subjected to a solution treatment at 550 ° C. for 60 seconds, and rapidly cooled to a quenching temperature of 20 ° C. at a cooling rate of 20 ° C./second. After maintaining at 20 ° C. for 10 minutes, the first stage pre-aging was performed by heating to a first stage pre-aging temperature of 80 ° C. at a rate of temperature increase of 20 ° C./min and holding at 80 ° C. for 1 hour. Then, without cooling, the second stage pre-aging temperature is maintained at 120 ° C. for 5 minutes by heating from 80 ° C. to 120 ° C. at a temperature increase rate of 20 ° C./hour, and up to 40 ° C. After cooling and holding at 40 ° C. for 3 and 30 days, room temperature aging characteristics, paint bake hardenability and moldability were evaluated by the following methods. The results are shown in Table 2.

Room temperature aging characteristics:
For a plate material (test material) held at 40 ° C. for 3 days and 30 days, a JIS No. 5 tensile test piece was taken in a direction parallel to the rolling direction, and then a tensile test was performed. The difference between the yield strength after 30 d) and the yield strength of the test material held for 3 days (the yield strength after 3 d) was evaluated, and a difference of 10 MPa or less was accepted and less than 10 MPa was rejected (x).

Paint bake curability:
For a plate material (test material) held at 40 ° C. for 30 days, a JIS No. 5 tensile test piece was taken in a direction parallel to the rolling direction, subjected to 2% tensile deformation, and then heat treated at 170 ° C. for 30 minutes. After performing, the tensile test was done at normal temperature, yield strength 200MPa or more was passed, and less than 200MPa was made disqualified (x).

Formability:
About the board | plate material (test material) hold | maintained at 40 degreeC for 30 days, the fracture limit strain amount of a plane strain and the presence or absence of a bending crack at the time of a bending test were investigated and evaluated.
The fracture limit amount of plane strain was measured by the following procedure. A test piece having a width of 50 mm and a length of 100 mm was taken in a direction parallel to the rolling direction, a scribed circle having a diameter of 5 mm was transferred to the test piece, and then an overhang test using a ball-head punch having a diameter of 50 mm was performed. . The molding conditions during the overhang test were wrinkle holding force: 50 kN, molding speed: 120 mm / min, and lubricating oil: high viscosity oil (kinematic viscosity 1000 mm ² / s). After measuring the scribed circle diameter (dimension A) in the principal strain direction in the vicinity of the fractured portion using the panel after the overhang test, the fracture limit strain amount of plane strain is calculated by the following formula, 0.20 or more Was passed and less than 0.20 was rejected (x).
(Fracture limit strain amount of plane strain) = ((dimension A) −5 mm) / 5 mm

  The presence or absence of bending cracks during the bending test was evaluated by the following procedure. A test piece having a width of 25 mm and a length of 200 mm was taken in a direction parallel to the rolling direction, subjected to 10% tensile deformation, and then subjected to a 180 ° bending test with an inner bending radius of 0.5 mm. Evaluation of bending workability was performed by visually observing the appearance of the bent portion, and the case where no crack was generated was accepted (◯), and the case where crack was generated was regarded as unacceptable (x).

  As shown in Table 2, all of the test materials 1 to 10 according to the present invention were excellent in paint bake hardenability and moldability and had a sufficient room temperature aging inhibitory effect.

  On the other hand, since the test material 11 and the test material 13 had a small amount of Si and Mg, respectively, the proof stress after paint baking was low and the paint bake curability was poor. Since the test material 12, the test material 14, and the test material 15 have a large amount of Si, Mg, and Cu, respectively, the difference between the proof strength after 3d and the proof strength after 30d is large, and the room temperature aging suppression effect is insufficient. It was. Moreover, the fracture limit amount of plane strain was low, bending cracks occurred, and the formability was poor.

  Since each of the test material 16 and the test material 17 had a large amount of Fe and Mn, both had low proof stress after paint baking and were inferior in paint bake curability. Moreover, the fracture limit strain amount of plane strain was low, bending cracks were generated, and the moldability was poor. Since each of the test material 18, the test material 19, and the test material 20 had a large amount of Cr, V, and Zr, all of them had a low plane strain breaking limit strain, a bending crack was generated, and the formability was poor.

Example 2 and Comparative Example 2
The ingot of aluminum alloy A shown in Table 1 is homogenized at 540 ° C. for 12 hours, then cooled to room temperature, and then reheated to 420 ° C. to start hot rolling, and to a thickness of 3.0 mm Rolled. The end temperature of hot rolling was 250 ° C. Subsequently, cold rolling was performed to 1.0 mm.

  About the obtained cold-rolled material, as shown in Table 3, the solution treatment of 470-590 degreeC is performed for 30 second, and it is 5-55 degreeC with the cooling rate of 0.2 degreeC / second and 2 degreeC / second. After cooling to the quenching temperature and holding at the quenching temperature for 3 to 70 minutes, heating to the first stage pre-aging temperature of 40 to 110 ° C. at a temperature rising rate of 0.2 ° C./min and 2 ° C./min, The first stage pre-aging was carried out at the first stage pre-aging temperature for 30 seconds to 11 hours. In Table 3, those outside the conditions of the present invention are underlined.

  Then, without cooling, the second stage pre-aging temperature of 120 ° C. was heated at a rate of temperature increase of 20 ° C./hour and held for 10 minutes to cool to 40 ° C. Then, after maintaining at a temperature of 40 ° C. for 3 days and 30 days, room temperature aging characteristics, paint bake hardenability, and moldability were evaluated in the same manner as in Example 1. The results are shown in Table 3.

  As shown in Table 3, all of the test materials 21 to 28 in accordance with the conditions of the present invention were excellent in paint bake hardenability and moldability and had a sufficient room temperature aging suppression effect.

  On the other hand, since the test material 29 has a low solution treatment temperature, the test material 31 has a low cooling rate after the solution treatment, and the test material 32 has a high quenching temperature. Since the aging time is long, the test material 34 has a low first stage pre-aging temperature, and the test material 36 has a low rate of temperature rise to the first stage pre-aging temperature. It was inferior in paint bake curability. Since the test material 30 had a high solution treatment temperature and local melting occurred during the solution treatment, each evaluation test could not be performed.

  Since the test material 35 has a high first stage pre-aging temperature, and the test material 37 has a short first stage pre-aging time, both have a yield strength after 30 days (strength after 30 d) and a yield strength after 3 days ( The difference from the yield strength after 3d) was large, and the room temperature aging suppression effect was insufficient. Moreover, the fracture limit strain amount of plane strain was low, bending cracking occurred, and the formability was poor.

  The test material 38 had a small difference between the proof strength after 30 days (proof strength after 30 d) and the proof strength after 3 days (proof strength after 3 d), and the proof strength after baking was high. Since the time was long, the proof stress after 30 days retention (proof strength after 30 d) was high, the fracture limit strain of plane strain was low, bending cracks were generated, and the formability was poor.

Example 3 and Comparative Example 3
The ingot of aluminum alloy A shown in Table 1 was homogenized at 560 ° C. for 16 hours, then cooled to room temperature, then reheated to 380 ° C. and started hot rolling until the thickness reached 2.5 mm. Rolled. The end temperature of hot rolling was 250 ° C. Subsequently, cold rolling was performed to 1.0 mm.

  The obtained cold-rolled material was subjected to a solution treatment at 550 ° C. for 45 seconds, cooled to a quenching temperature of 30 ° C. at a cooling rate of 10 ° C./second, held at the quenching temperature for 5 minutes, and then 10 ° C. The first stage pre-aging was carried out by heating to the first stage pre-aging temperature of 90 ° C. at a rate of temperature rise / minute and holding at the first stage pre-aging temperature for 2 hours.

  Then, without cooling, as shown in Table 4, it was heated to the second stage pre-aging temperature of 90 to 150 ° C. at a rate of temperature increase of 0.1 ° C./hour and 1 ° C./hour, for 30 seconds to 11 The second stage pre-aging was carried out for a period of time and cooled to 40 ° C. Then, after maintaining at a temperature of 40 ° C. for 3 days and 30 days, room temperature aging characteristics, paint bake hardenability, and moldability were evaluated in the same manner as in Example 1. The results are shown in Table 4. In Table 4, those outside the conditions of the present invention are underlined.

  As shown in Table 3, all of the test materials 39 to 43 according to the conditions of the present invention were excellent in paint bake hardenability and moldability and had a sufficient room temperature aging suppression effect.

  In contrast, the test material 44 has a low second stage pre-aging temperature, and the difference between the first stage pre-aging temperature and the second stage pre-aging temperature is small. Since the temperature rate is low, the test material 47 has a short second stage pre-aging time, and therefore, the difference between the yield strength after 30 days (strength after 30 d) and the yield strength after 3 days (strength after 3 d). The room temperature aging inhibitory effect was insufficient. Moreover, the fracture limit strain amount of plane strain was low, bending cracking occurred, and the formability was poor.

  Since the test material 45 has a high second stage pre-aging temperature, and the test material 48 has a long second stage pre-aging time, both have a high yield strength after 30 days (30d yield strength) and fracture of plane strain. The limit strain was low, bending cracks occurred, and the formability was poor.

Example 4 and Comparative Example 4
The ingot of aluminum alloy A shown in Table 1 was homogenized at 560 ° C. for 24 hours, then cooled to room temperature, and then reheated to 410 ° C. to start hot rolling, to a thickness of 4.0 mm Rolled. The end temperature of hot rolling was 250 ° C. Subsequently, cold rolling was performed to 1.0 mm.

  The obtained cold-rolled material was subjected to a solution treatment at 560 ° C. for 45 seconds, cooled to a quenching temperature of 40 ° C. at a cooling rate of 50 ° C./second, held at the quenching temperature for 1 minute, and then 15 ° C. The first stage pre-aging was performed by heating to 90 ° C. at the first stage pre-aging temperature at a rate of temperature rise / min and holding at the first stage pre-aging temperature for 1.5 hours.

  Then, as shown in Table 5, after cooling to a temperature of 45 ° C. and 55 ° C. at a cooling rate of 20 ° C./hour, the second stage pre-aging temperature of 95 to 145 ° C. is reached at a heating rate of 1 ° C./hour. The second stage pre-aging was performed by heating and holding for 1 minute to 10 hours, and cooled to 40 ° C. Then, after maintaining at a temperature of 40 ° C. for 3 days and 30 days, room temperature aging characteristics, paint bake hardenability, and moldability were evaluated in the same manner as in Example 1. The results are shown in Table 5. In Table 5, those outside the conditions of the present invention are underlined.

  As shown in Table 5, all of the test materials 49 to 53 according to the conditions of the present invention were excellent in paint bake hardenability and moldability and had a sufficient room temperature aging inhibitory effect.

  On the other hand, the test material 54 had a low cooling temperature of 45 ° C. after the first stage pre-aging, and the second stage pre-aging temperature was slightly low, so the paint bake curability was inferior. Further, the test material 55 had a low cooling temperature of 45 ° C. after the first stage pre-aging, and the second stage pre-aging temperature was slightly high, so the paint bake curability was inferior.

Claims (3)

In mass%, Si: 0.5 to 2.0%, Mg: 0.2 to 1.5%, Cu: 1.0% or less, Zn: 0.5% or less, Fe: 0.00%. 5% or less, Mn: 0.3% or less, Cr: 0.3% or less, V: 0.2% or less, Zr: 0.15% or less, Ti: 0.1% or less, B: 0.005% Treating a plate of Al—Mg—Si based aluminum alloy containing one or more of the following and having the balance of Al and inevitable impurities in the following steps (1) to (3) A method for producing an Al—Mg—Si-based aluminum alloy plate that is excellent in paint bake hardenability and formability and has an effect of suppressing aging at room temperature.
(1) A quenching process in which a solution treatment is performed at a temperature of 480 ° C. or more and 580 ° C. or less, and the solution is cooled to a quenching temperature of less than 50 ° C. at a cooling rate of 2 ° C./second or more
(2) After holding at the quenching temperature for less than 1 hour, the first stage pre-aging temperature is heated to a first stage pre-aging temperature of 50 ° C. or more and 100 ° C. or less at a temperature rising rate of 2 ° C./min or more. And the first stage pre-aging process for holding at least 1 minute and within 10 hours, and
(3) Heat at a temperature rising rate of 1 ° C./hour or more to a second stage pre-aging temperature of 10 ° C. to 140 ° C. higher than the first stage pre-aging temperature, and the second stage pre-aging temperature is 1 Second stage pre-aging process for holding for 10 minutes or more. The second-stage preliminary aging process of (3) is performed after the first-stage preliminary aging process of (2) is cooled to a temperature not lower than 50 ° C and lower than the first-stage preliminary aging temperature. The manufacturing method of the Al-Mg-Si type aluminum alloy plate which is excellent in paint bake hardenability and formability of 1 and has a room temperature aging suppression effect. The paint bake hardenability and formability according to claim 1, wherein the second stage pre-aging step (3) is performed after the first stage pre-aging step (2) without cooling. A method for producing an Al—Mg—Si-based aluminum alloy plate having an excellent room temperature aging suppression effect.