JP2012149354A - Aluminum alloy sheet, and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum alloy sheet having excellent high temperature formability and its manufacturing method.SOLUTION: The aluminum alloy sheet is composed of an aluminum alloy having a composition consisting of 0.8 to 2.5 mass% Mn and the balance Al with inevitable impurities and is characterized in that a solid-solution Mn content is made to ≤1.0 mass% and (solid-solution Mn content)/(precipitated Mn content)≤2.0 is satisfied, the number density of a Mn based compound of a particle diameter of 0.5-5.0 μm is ≥1,000/mmand ≤10,500/mm, and the average grain size is ≤30 μm. The method for manufacturing the aluminum alloy sheet is characterized as follows: the aluminum alloy is melted and cast at ≥0.1°C/sec and ≤5.0°C/sec cooling rate into an ingot; homogenizing heat treatment, hot rolling and cold rolling are applied to the ingot to form a cold rolled sheet; and the cold rolled sheet is annealed under the conditions of ≥50°C/min temperature-rise rate, 400 to 600°C annealing temperature and ≥50°C/min cooling rate from the annealing temperature to 200°C.

Description

  TECHNICAL FIELD The present invention relates to an aluminum alloy plate used for an automobile panel structure or the like made of an Al—Mn alloy and a method for manufacturing the same, and in particular, an aluminum alloy plate used for a panel structure or the like manufactured by high-temperature molding, and It relates to the manufacturing method.

  In recent years, against the backdrop of increasing awareness of the global environment, for the purpose of improving fuel economy, for transportation equipment such as automobiles, ships, aircraft, or vehicles, machines, electrical products, architecture, structures, optical equipment, components and parts of equipment As a result, demands for weight reduction are increasing. For example, application of an aluminum alloy plate to a body panel material of an automobile in place of a conventional steel material such as a steel plate is being studied.

  In particular, panels such as outer panels (outer plates) and inner panels (inner plates) used in panel structures such as automobile hoods, fenders, doors, roofs, trunk lids, etc. are thin among the aluminum alloy plates. In addition, application of a high-strength aluminum panel plate, for example, an Al—Mg—Si-based alloy plate (such as a JIS-defined 6000-based alloy plate) has been studied.

  As for the inner panel material of automobiles, since the surface quality is not a problem, formability is emphasized among the aluminum alloy plates. Recently, a general-purpose aluminum alloy plate such as a 5000 series alloy plate (5052 alloy specified by JIS) is used. Application of plate, Al-Mg alloy plate) has been studied.

  However, the above-mentioned general-purpose aluminum alloy plate has a limit in improving press formability in a state having recyclability leading to cost reduction, and has not yet reached practical press formability. For this reason, further improvements in press formability have been demanded by automobile manufacturers and the like.

  On the other hand, there are DI cans and bottle cans as application examples of 3000 series alloy plates. As measures for improving productivity and product characteristics, elements such as Si, Mg, Cu and Fe are added, or alloy elements are added. Attempts have been made to control the crystal grain size and the dispersion state of crystal precipitates.

For example, Patent Document 1 describes an aluminum alloy plate for a bottle can in which the strength of a processed part is controlled by controlling the Mn solid solution amount to 0.1 to 0.17% by mass to improve necking property. Has been. Patent Document 2 describes an aluminum alloy plate for a bottle can in which corrosion resistance and formability are improved by controlling an intermetallic compound having a diameter of 0.1 to 1 μm to 10,000 or less per 1 mm ² . In Patent Document 3, by controlling the number of Mg ₂ Si compounds having a diameter of 0.1 to 1 μm to 10000 or less per 1 mm ² , the ear rate is kept low and the strength is improved by solute Mg and Si. An aluminum alloy plate for a DI can body is described. Patent Document 4 describes an aluminum alloy plate for a DI can body, in which the rupture rate during can making is improved by controlling the amount of dissolved Si to 10 to 100 ppm.

  As a measure for improving formability, a method of controlling the structural state of the aluminum alloy plate has been attempted. For example, in Patent Document 5, the average particle diameter of precipitates of 0.01 μm or more is set to 0.2 to 0.5 μm, and the structure is controlled so as to exhibit an exothermic peak at 230 to 300 ° C. in the differential scanning calorimetry curve. Thus, an Al-Mn alloy plate with improved press formability is described.

  Further, as a measure for improving formability, it is attempted to use a high temperature forming method represented by, for example, a local heating blank method, a warm forming method, and a high temperature blow forming method, which is excellent in formability as compared with a room temperature forming method. An aluminum alloy plate made of a material suitable for the high temperature forming method has been studied.

For example, Patent Document 6, ² per 1,000 0.1mm the number of particle size 1~5μm of Al-Mn intermetallic compound particles (10000 / mm ²⁾ or more, further, the average crystal grain size 50μm or less The aluminum alloy plate which has improved the warm formability in the warm forming in the range of 150 to 350 ° C. and the stress corrosion cracking resistance after the warm forming is described. In Patent Document 7, the Fe solid solution amount is controlled to 10 ppm or less, the Mn solid solution amount is controlled to 500 ppm or less, and the tensile elongation at 200 to 300 ° C. is controlled to 65% or more. An improved aluminum alloy plate is described.

JP 2006-77310 A JP 2006-152359 A JP 2000-1730 A Japanese Patent Laid-Open No. 10-121177 Japanese Patent Laid-Open No. 2002-275566 JP-A-7-310137 JP 2002-348625 A

  However, the aluminum alloy sheets of Patent Documents 1 to 5 are intended to improve the production efficiency at the time of forming at room temperature and the properties of the molded product, and the local elongation during high temperature forming cannot be controlled, resulting in poor high temperature formability. There was a problem. In addition, in the aluminum alloy plates of Patent Documents 6 and 7, it cannot be said that high-temperature formability that satisfies the demands of automobile manufacturers and the like, which have been increasingly severe in recent years, has been achieved. It has been demanded.

  Accordingly, the present invention has been made to solve such problems, and an object thereof is to provide an aluminum alloy plate having good high-temperature formability and a method for producing the same.

In order to solve the above-mentioned problems, an aluminum alloy plate according to the present invention contains Mn: 0.8 to 2.5% by mass, and the balance is made of an aluminum alloy composed of Al and inevitable impurities. Is 1.0 mass% or less, and the Mn solid solution amount / Mn precipitation amount is 2.0 or less, and the number density of Mn-based compounds having a particle diameter of 0.5 to 5.0 μm is 1000 / mm ^2. More than 10500 pieces / mm ² and the average crystal grain size is 30 μm or less.

  According to the said structure, by reducing the amount of Mn solid solution below a predetermined value, strain rate sensitivity increases and local elongation at high temperature increases. Also, by increasing the Mn solid solution amount / Mn precipitation amount to a predetermined value or less, that is, by increasing the Mn precipitation amount, accumulation of strain around the Mn-based compound during molding is promoted, and dynamic recovery is facilitated. , Local elongation increases. In addition, by increasing the number density of Mn-based compounds having a predetermined diameter or more to a predetermined value or more, accumulation of strain around the Mn-based compound during molding is promoted, and dynamic recovery is facilitated, whereby local elongation is increased. It will increase even more. Furthermore, by reducing the average crystal grain size to a predetermined value or less, the crystal grains are refined and the local elongation is further increased.

  In the aluminum alloy plate according to the present invention, the aluminum alloy further includes Fe: 1.5 mass% or less, Mg: 2.0 mass% or less, Si: 1.5 mass% or less, Cu: 1.0 mass%. Hereinafter, Cr: 0.5% by mass or less, Zr: 0.5% by mass or less, V: 0.3% by mass or less, Ti: 0.2% by mass or less, and Zn: 1.5% by mass or less It is characterized by including 1 type.

  According to the above configuration, the aluminum alloy contains a predetermined amount of at least one of Fe, Mg, Si, Cu, Cr, Zr, V, Ti, and Zn, so that the crystal grains are refined and the local elongation is increased. It will increase even more.

  The method for producing an aluminum alloy plate according to the present invention comprises Mn: 0.8 to 2.5% by mass, with the balance being aluminum and inevitable impurities dissolved, and a cooling rate of 0.1 ° C./sec. A casting process for producing an ingot by casting at a temperature of 5.0 ° C./second or less, a homogenization heat treatment process for subjecting the ingot to a homogenization heat treatment, and hot rolling the ingot subjected to the homogenization heat treatment A hot rolling step for producing a hot-rolled sheet, a cold-rolling step for producing a cold-rolled plate by cold-rolling the hot-rolled plate, and a heating rate of 50 ° C./min or more on the cold-rolled plate And an annealing step of producing an aluminum alloy sheet by annealing at an annealing temperature of 400 to 600 ° C. and annealing at a cooling rate of 50 ° C./min or more from the annealing temperature to 200 ° C.

  According to the above procedure, by controlling the cooling rate during casting, the heating rate during annealing, the annealing temperature, and the cooling rate within a predetermined range, the microstructure state of the aluminum alloy sheet, that is, the Mn solid solution amount, Mn The amount of solid solution / Mn precipitation, the number density of Mn-based compounds, and the average crystal grain size are appropriate.

  In the method for producing an aluminum alloy plate according to the present invention, the aluminum alloy further includes Fe: 1.5 mass% or less, Mg: 2.0 mass% or less, Si: 1.5 mass% or less, Cu: 1. 0 mass% or less, Cr: 0.5 mass% or less, Zr: 0.5 mass% or less, V: 0.3 mass% or less, Ti: 0.2 mass% or less, and Zn: 1.5 mass% or less It contains at least one of them.

  According to the above procedure, the aluminum alloy contains a predetermined amount of at least one of Fe, Mg, Si, Cu, Cr, Zr, V, Ti and Zn, so that the crystal grains are refined and the local elongation is reduced. It will increase even more.

  The aluminum alloy plate according to the present invention has good high temperature formability by controlling the Mn solid solution amount and the Mn solid solution amount / Mn precipitation amount of the aluminum alloy plate. In addition, the high temperature formability is further improved by controlling the number density and average crystal grain size of the Mn-based compound of the aluminum alloy plate. Furthermore, when the aluminum alloy further contains a predetermined element, the high temperature formability is further improved.

  In addition, since the aluminum alloy plate according to the present invention has good high-temperature formability, particularly for plate materials for automobiles, airplanes, ships, home appliances, etc., particularly for automobile plate materials and structural members, It can be effectively used in a wide range of fields that require molding into complex shapes to improve design.

  According to the method for producing an aluminum alloy sheet according to the present invention, by controlling the cooling rate during casting, the heating rate during annealing, the annealing temperature, and the cooling rate within a predetermined range, it has good high temperature formability. Aluminum alloy plates can be manufactured. Moreover, when the aluminum alloy further contains a predetermined element, an aluminum alloy plate having even better high-temperature formability can be produced.

It is explanatory drawing which showed warm forming typically.

An embodiment of an aluminum alloy plate according to the present invention will be described in detail.
The aluminum alloy plate contains a predetermined amount of Mn, and the balance is made of an aluminum alloy (Al-Mn alloy) composed of Al and inevitable impurities. The Mn solid solution amount, the Mn solid solution amount / Mn is less than a predetermined value. It has a precipitation amount.

  That is, in the aluminum alloy plate, the alloy structure is controlled in the direction in which the Mn solid solution amount decreases and in the direction in which a large amount of Mn precipitates are dispersed finely (the direction in which the Mn solid solution amount / Mn precipitation amount decreases). . Decreasing the amount of Mn solid solution increases the strain rate sensitivity, increases the local elongation at high temperatures, and improves the high temperature formability. On the other hand, the increase in Mn precipitates promotes the accumulation of strain around the Mn-based compound during molding, facilitates dynamic recovery, increases local elongation at high temperatures, and improves high-temperature moldability. In addition, in this invention, high temperature means the temperature range about 150-400 degreeC.

<Mn amount: 0.8 to 2.5 mass%>
When the amount of Mn in the aluminum alloy is less than 0.8% by mass, the amount of Mn solid solution / the amount of precipitated Mn increases, the formation of Al—Mn compounds decreases, and the number density also decreases. As a result, the minimum high-temperature formability required for an aluminum alloy plate cannot be obtained. On the other hand, if the amount of Mn exceeds 2.5% by mass, the amount of Mn solid solution increases, and a coarse Mn-based compound is formed, which acts as a starting point for fracture, so that high-temperature formability is reduced. Therefore, the amount of Mn is 0.8 to 2.5% by mass, preferably 1.0 to 2.3% by mass, and more preferably 1.2 to 2.0% by mass.

<Inevitable impurities>
The content of inevitable impurities is preferably in a range that does not affect the characteristics of the aluminum alloy sheet according to the present invention.

<Mn solid solution amount: 1.0 mass% or less>
When the Mn solid solution amount of the aluminum alloy plate exceeds 1.0% by mass, the strain rate sensitivity becomes too small, the dynamic recovery becomes difficult to occur, the local elongation at high temperature is lowered, and the high temperature formability is lowered. Therefore, the Mn solid solution amount is 1.0 mass% or less, preferably 0.5 mass% or less. The amount of Mn solid solution is controlled by the amount of Mn of the aluminum alloy and the annealing temperature in the manufacturing process of the aluminum alloy sheet described later.

<Mn solid solution amount / Mn precipitation amount: 2.0 or less>
When the Mn solid solution amount / Mn precipitation amount of the aluminum alloy plate exceeds 2.0, dynamic recovery is difficult to occur, local elongation at high temperature is reduced, and high temperature formability is lowered. Therefore, the Mn solid solution amount / Mn precipitation amount is 2.0 or less, preferably 1.5 or less, more preferably 1.0 or less. Control of the Mn solid solution amount / Mn precipitation amount is performed by the Mn amount of the aluminum alloy, the cooling rate at the time of casting in the production process of the aluminum alloy sheet, the heating rate at the time of annealing, the annealing temperature, and the cooling rate at the time of annealing.

  The aluminum alloy plate according to the present invention preferably has an average crystal grain size in which the number density of Mn-based compounds having a predetermined diameter or more is not less than a predetermined value and not more than a predetermined value.

<Number density of Mn-based compounds having a particle diameter of 0.5 to 5.0 μm: 1000 / mm ² or more>
When the number density of the Mn-based compound (particle diameter (maximum diameter) 0.5 to 5.0 μm) of the aluminum alloy plate is less than 1000 / mm ² , dynamic recovery is less likely to occur, and local elongation at high temperatures is reduced. The high temperature formability tends to decrease. Therefore, the number density of the Mn-based compound is set to 1000 / mm ² or more. On the other hand, if the number density is too large, the particle spacing becomes too short and cracks are likely to propagate, so that high temperature formability is likely to be reduced. Therefore, the number density is preferably 1,000 to 10,000 pieces / mm ^2, more preferably from 1,500 to 8,000 pieces / mm ^2, and optimally 2000 to 6000 pieces / mm ^2. The number density of the Mn-based compound is controlled by the amount of Mn of the aluminum alloy and the cooling rate during casting in the production process of the aluminum alloy sheet.

  The reason why the particle size of the Mn-based compound to be measured is 0.5 μm or more is that it is difficult to detect particles smaller than 0.5 μm due to the resolution of the measuring apparatus. The reason why the particle diameter is 5.0 μm or less is that when the particle diameter exceeds 5.0 μm, the particle diameter becomes too large, and the particles tend to be the starting point of breakage, and the high-temperature formability tends to be lowered. In addition, the influence which the Mn type compound with a particle diameter of less than 0.5 micrometer has on the high temperature moldability is very small.

<Average crystal grain size: 30 μm or less>
When the average crystal grain size of the aluminum alloy plate is larger than 30 μm, the local elongation at high temperature is lowered, and the high temperature formability tends to be lowered. Therefore, the average crystal grain size is 30 μm or less. The average crystal grain size is controlled by the heating rate, annealing temperature, and cooling rate during annealing of the aluminum alloy plate.

The aluminum alloy plate according to the present invention preferably contains a predetermined amount of at least one of Fe, Mg, Si, Cu, Cr, Zr, V, Ti and Zn in addition to the Mn.
<Fe, Mg, Si, Cu, Cr, Zr, V, Ti and Zn amount>
Fe, Mg, Si, Cu, Cr, Zr, V, Ti, and Zn are useful for refining crystal grains, and can improve high-temperature formability. However, when the content is too large, a coarse compound is formed, which acts as a starting point of destruction, and thus high temperature moldability is lowered. When the above elements are contained, the content is preferably as follows.

(Fe content)
In ordinary aluminum ingots, it is unavoidably contained in an amount of about 0.05% by mass, but may be a content very close to 0% by mass unless it becomes 0% by mass, Mass% is preferred.
(Mg amount)
As long as it does not become 0 mass%, the content may be very close to 0 mass%, but 0.01 to 2.0 mass% is preferable.
(Si amount)
In ordinary aluminum ingots, it is unavoidably contained in an amount of about 0.05% by mass, but may be a content very close to 0% by mass unless it becomes 0% by mass, Mass% is preferred.
(Cu amount)
As long as it does not become 0 mass%, the content may be very close to 0 mass%, but 0.01 to 1.0 mass% is preferable.
(Cr content)
As long as it does not become 0 mass%, the content may be very close to 0 mass%, but 0.01 to 0.5 mass% is preferable.
(Zr amount)
As long as it does not become 0 mass%, the content may be very close to 0 mass%, but 0.01 to 0.5 mass% is preferable.
(V amount)
As long as it does not become 0 mass%, the content may be very close to 0 mass%, but 0.01 to 0.3 mass% is preferable.
(Ti amount)
As long as it does not become 0 mass%, the content may be very close to 0 mass%, but 0.005 to 0.2 mass% is preferable.
(Zn content)
As long as it does not become 0 mass%, the content may be very close to 0 mass%, but 0.1 to 1.5 mass% is preferable.

Next, the manufacturing method of the aluminum alloy plate which concerns on this invention is demonstrated.
Ordinary aluminum alloy sheets are often manufactured through each process of a casting process, a homogenizing heat treatment process, a hot rolling process, and a cold rolling process. The point of the manufacturing method of this invention exists in the place which anneals (final annealing) after a cold rolling process. That is, it is manufactured through each process of a casting process, a homogenization heat treatment process, a hot rolling process, a cold rolling process, and an annealing process. Further, rough annealing may be performed after the hot rolling step, or cold rolling may be performed a plurality of times in the cold rolling step, and intermediate annealing may be performed during the cold rolling.

  In addition, a casting process, a homogenization heat treatment process, a hot rolling process, a cold rolling process, and an annealing process are performed by a conventionally well-known method. Depending on the composition of the aluminum alloy used and the setting conditions of each process, the physical properties and structure obtained will vary, so the conditions should be selected and determined comprehensively as a series of manufacturing processes. It is not always appropriate to set strict. However, as a manufacturing method using an aluminum alloy having the above-described component composition, the present inventors have studied, and if the following conditions are employed, the structure state of the aluminum alloy plate described above, that is, the Mn solid solution amount, It becomes possible to realize the Mn solid solution amount / Mn precipitation amount, the number density of the Mn-based compound, and the average crystal grain size, and the aluminum alloy plate having good high-temperature formability intended in the present invention can be obtained with certainty.

(1) In the casting process, the cooling rate until solidification, that is, the average cooling rate from the casting temperature before cooling to 200 ° C. is set to 0.1 ° C./second or more. When the cooling rate is less than 0.1 ° C./second, coarse crystal precipitates are formed during cooling, so that the Mn solid solution amount / Mn precipitation amount increases and the number density of the Mn-based compound decreases. . As a result, local elongation at high temperatures is reduced, and high temperature formability is reduced. A more preferable cooling rate is 1 ° C./second or more. The casting may be either semi-continuous casting (DC casting) or thin plate continuous casting.

(2) In the annealing step, the rate of temperature rise is set to 50 ° C./min or more. This annealing aims at recrystallization and Mn precipitation treatment. If the temperature increase rate of annealing is less than 50 ° C./min, coarse recrystallized grains are generated during the temperature increase, the Mn solid solution amount / Mn precipitation amount increases, and the average crystal grain size increases. As a result, local elongation at high temperatures is reduced, and high temperature formability is reduced.

(3) An annealing temperature shall be 400-600 degreeC in an annealing process. When the annealing temperature is less than 400 ° C., the workability remains, and thus the warm formability is lowered. On the other hand, when it exceeds 600 ° C., burning occurs and pores are formed. In addition, the average crystal grain size increases. As a result, local elongation at high temperatures is reduced, and high temperature formability is reduced.

(4) In the annealing step, the cooling rate after annealing, that is, the average cooling rate from the annealing temperature to 200 ° C. is set to 50 ° C./min or more. When the cooling rate of annealing is less than 50 ° C./min, the amount of Mn solid solution / the amount of precipitated Mn increases, coarse recrystallized grains are generated during cooling, and the average crystal grain size increases. As a result, local elongation at high temperatures is reduced, and high temperature formability is reduced.

  Moreover, the manufacturing method of the aluminum alloy plate which concerns on this invention WHEREIN: You may perform the 2nd annealing after the 1st annealing for the above-mentioned recrystallization and Mn precipitation process in an annealing process. The purpose of the second annealing is to reduce the amount of Mn solid solution by promoting Mn precipitation. The second annealing temperature is preferably 150 to 500 ° C. If the second annealing temperature is less than 150 ° C., Mn precipitation cannot be promoted, and the amount of Mn solid solution / Mn precipitation increases. On the other hand, when the annealing temperature for the second time exceeds 500 ° C., coarse recrystallized grains are generated, the amount of Mn solid solution / the amount of precipitated Mn increases, and the average crystal grain size increases. As a result, local elongation at high temperatures is reduced, and high temperature formability is reduced.

Next, the aluminum alloy plate according to the present invention will be specifically described with reference to examples. In addition, let the thing of annealing twice be a reference example.
Aluminum alloys having the composition shown in Table 1 were cast by DC casting (Examples 1 to 10, 12, Reference Examples 1 and 2 and Comparative Examples 1 to 9) to obtain ingots having a thickness of 50 mm. Alternatively, casting was performed by thin plate continuous casting (Example 11, Reference Example 3) to obtain an ingot having a thickness of 10 mm. The obtained ingot is subjected to homogenization heat treatment at 500 ° C. and then hot-rolled. About the obtained hot-rolled sheet having a thickness of 3 mm, cold rolling is performed to produce a cold-rolled sheet having a thickness of 1 mm, and final annealing is performed under the conditions shown in Table 2, and Examples 1 to 12 and Reference Examples 1 to 1 are performed. 3. The aluminum alloy plate (test plate) of Comparative Examples 1 to 9 was obtained.

  About the obtained test plate, the Mn solid solution amount, the Mn solid solution amount / Mn precipitation amount, the number density of the Mn-based compound, and the average crystal grain size were measured by the following methods. The results are shown in Table 2.

(Mn solid solution amount, Mn solid solution amount / Mn precipitation amount)
Only the matrix of the test plate was dissolved, and oxides, crystallized substances and precipitates in the aluminum alloy were extracted and separated with a mesh having an opening of 0.1 μm. The amount of Mn precipitated in the filtrate without being extracted and separated at that time was defined as the Mn solid solution amount. Further, the amount of Mn contained in the extraction residue extracted and separated was defined as the Mn precipitation amount. Then, the Mn solid solution amount / Mn precipitation amount was determined by dividing the Mn solid solution amount by the Mn precipitation amount. Here, the amount of Mn in the precipitate and the residue was determined by ICP emission spectroscopy.

(Mn-based compound number density)
The number density of the Mn compound was measured as follows. First, the test plate was scraped off by mechanical polishing from the rolled surface to a depth of 0.25 mm, and the polished surface was measured by EPMA (JXA-8000 series, manufactured by JEOL Ltd., measurement conditions were acceleration voltage 20 kV). The measurement area was about 0.1 to 0.2 mm ² and the magnification at the time of measurement was 600 times. The object to be measured was particles having a maximum diameter of 0.5 to 5.0 μm.

  Of all particles detected by measurement, Mn-based compounds were extracted as follows. First, the constituent elements (5 elements of Fe, Mn, Mg, Si, and Cu) contained in each particle are analyzed with an EPMA apparatus (at%). Since the quantitative value obtained here has a problem in analysis accuracy depending on the size and beam diameter of each particle, the Mn-based compound was discriminated based on the ratio of the main contained elements. A specific analysis method is shown below.

  The total amount (TOTAL) of Fe (at%) + Mn (at%) + Mg (at%) + Si (at%) + Cu (at%) is determined by the EPMA apparatus. Next, Fe / TOTAL, Mn / TOTAL, Mg / TOTAL, Si / TOTAL, and Cu / TOTAL are included in the five contained elements (relative to the total amount of the five contained elements) per particle. Each content ratio of Mg, Si, and Cu is obtained. Among these, those having Mn / TOTAL of 0.3 or more were designated as Mn compounds. The number density of Mn-based compounds was obtained by dividing the number of particles discriminated as Mn-based compounds in the above analysis by the measurement area.

(Average crystal grain size)
The average crystal grain size was measured as follows. First, a sample was prepared by mechanically polishing the test material from the rolled surface to a depth of 0.25 mm, adjusting the surface by electrolytic polishing following buff polishing. The sample was subjected to crystal orientation measurement and crystal grain size measurement by EBSP (Electron Back Scattering (Scattered) Pattern) using SEM (JEOL JSM 5410) manufactured by JEOL Ltd. The measurement area was an area of 1500 μm × 1500 μm, and the measurement step interval was 2 μm. As the EBSP measurement / analysis system, EBSP: manufactured by TSL (OIM) was used.

In the measurement, the deviation of the orientation within ± 15 ° was defined as belonging to the same crystal grain, and the boundary between crystal grains where the orientation difference between adjacent crystal grains was 5 ° or more was defined as the crystal grain boundary. Then, the average crystal grain size was calculated by the following formula (1).
Average crystal grain size = (Σx) / n (1)
Where n is the number of crystal grains measured and x is the crystal grain diameter of each.

  Next, with respect to the test plate, the molding height and local elongation were measured by the following methods, and the high temperature moldability was evaluated from the measured values. The results are shown in Table 2.

(Molding height)
A test piece of 120 mm × 120 mm was prepared from the test plate by cutting. As shown in FIG. 1, a test piece is set between the punch 5 (50 mmφ, shoulder R4.5 mm) of the press machine 10 and the dies 6 and 7 (54.5-56.0 mmφ, shoulder R8-10 mm). Using a lubricant (manufactured by Nippon Tool Oil Co., Ltd., CF853), warm forming (deep drawing test) was performed under the conditions of a wrinkle holding load of 1.2 kg / cm ² and a punch speed of 80 mm / min, and the forming height was measured. . The molding height was the punch depth when a part of the test piece was broken. The molding height was less than 25 mm, the high-temperature moldability was poor (x), 25 mm or more and less than 30 mm was good (○), and 30 mm or more was excellent in high-temperature molding (◎).

  Here, as a temperature condition of the warm forming, heating was performed using the heater 8 so that the temperature of the flange portion 2 of the test piece 1 was 260 ° C. In addition, by cooling the bottom of the punch 5 with the cooling pipe 9 in which cooling water has flowed, the corner portion 3 of the sample piece 1 that contacts the corner portion of the punch 5 and the bottom of the sample piece 1 that contacts the bottom portion of the punch 5. The temperature of the portion 4 was set to a relatively low temperature of 100 ° C. or lower. These temperatures were measured with a contact thermometer. And the temperature of the flange part 2, the corner part 3, and the bottom part 4 was controlled using the average temperature in the measurement in multiple times within predetermined measurement time.

(Local growth)
From the test plate, a tensile test piece (JIS No. 5 test piece) whose longitudinal direction is 90 ° with respect to the rolling direction was cut out. After performing a tensile test using this test piece and obtaining its stress-strain curve, the local elongation defined in JISG0202 was determined. The atmospheric temperature at the time of the tensile test was 250 ° C. The tensile test piece was attached after reaching the atmospheric temperature in advance, and held for about 10 minutes after the attachment, and then the tensile test was performed. Furthermore, the test was performed 3 times for each test plate, and the average value was adopted. When the local elongation was less than 50%, the high-temperature formability was poor (x), and when 50% or more, the high-temperature formability was good (◯).

  From the results shown in Table 2, Examples 1 to 12 show component compositions (Mn content, Mg content, Si content, Fe content, Cr content, Zr content, V content, Ti content, Cu content, Zn content as defined in the claims. ), Mn solid solution amount, Mn solid solution amount / Mn precipitation amount, the number density of Mn-based compounds, and the average crystal grain size, the high temperature formability was good or excellent. In addition, Reference Examples 1 to 3 were also excellent in high temperature formability.

  In Comparative Example 1, since the Mn amount was less than the lower limit value, the Mn solid solution amount / Mn precipitation amount exceeded the upper limit value, and the number density of the Mn-based compound became less than the lower limit value. As a result, the high temperature formability was poor.

  In Comparative Example 2, since the Mn amount exceeded the upper limit value, the Mn solid solution amount exceeded the upper limit value. As a result, the high temperature formability was poor.

  In Comparative Example 3, the component composition satisfies the claims, but the cooling rate during casting is low, so the Mn solid solution amount / Mn precipitation amount exceeds the upper limit value, and the number density of the Mn-based compound is less than the lower limit value. became. As a result, the high temperature formability was poor.

  In Comparative Example 4, the component composition satisfies the claimed range, but because the rate of temperature increase during the first annealing is low, the Mn solid solution amount / Mn precipitation amount exceeds the upper limit value, and the average crystal grain size is the upper limit value. Exceeded. As a result, the high temperature formability was poor.

  In Comparative Example 5, the component composition satisfied the claimed range, but the annealing temperature at the first time was low, so that the Mn solid solution amount / Mn precipitation amount exceeded the upper limit value, and the processed structure remained. As a result, the high temperature formability was poor.

  In Comparative Example 6, the component composition satisfies the claimed range, but because the first annealing temperature is high, the Mn solid solution amount, the Mn solid solution amount / Mn precipitation amount exceeds the upper limit, and the average crystal grain size is the upper limit. The value was exceeded. As a result, the high temperature formability was poor. Moreover, burning occurred and pores were formed.

  In Comparative Example 7, the component composition satisfies the claimed range, but because the cooling rate during the first annealing is low, the Mn solid solution amount / Mn precipitation amount exceeds the upper limit value, and the average crystal grain size exceeds the upper limit value. Beyond. As a result, the high temperature formability was poor.

  In Comparative Example 8, the component composition satisfied the claimed range, but the second annealing temperature was low, so the Mn solid solution amount / Mn precipitation amount exceeded the upper limit. As a result, the high temperature formability was poor.

  In Comparative Example 9, although the component composition satisfied the claimed range, the second annealing temperature was high, so the Mn solid solution amount / Mn precipitation amount exceeded the upper limit value, and the average crystal grain size exceeded the upper limit value. As a result, the high temperature formability was poor.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to above-described embodiment, You may change suitably in the range which does not deviate from the claim of this invention.

DESCRIPTION OF SYMBOLS 1 Test piece 2 Flange part 3 Corner part 4 Bottom part 5 Punch 6, 7 Dies 8 Heater 9 Cooling tube 10 Press machine

Claims (4)

Mn: 0.8 to 2.5% by mass, the balance is made of an aluminum alloy composed of Al and inevitable impurities, the Mn solid solution amount is 1.0% by mass or less, and the Mn solid solution amount / Mn precipitation In an aluminum alloy plate whose amount is 2.0 or less,
The number density of the Mn-based compound having a particle diameter of 0.5 to 5.0 μm is 1000 / mm ² or more and 10500 / mm ² or less, and
An aluminum alloy plate having an average crystal grain size of 30 μm or less.   The aluminum alloy is further Fe: 1.5 mass% or less, Mg: 2.0 mass% or less, Si: 1.5 mass% or less, Cu: 1.0 mass% or less, Cr: 0.5 mass% In the following, at least one of Zr: 0.5% by mass or less, V: 0.3% by mass or less, Ti: 0.2% by mass or less, and Zn: 1.5% by mass or less is included. The aluminum alloy plate according to claim 1. Mn: containing 0.8 to 2.5% by mass, with the balance being an aluminum alloy consisting of Al and inevitable impurities, and casting at a cooling rate of 0.1 ° C / second to 5.0 ° C / second A casting process for producing an ingot;
A homogenization heat treatment step for subjecting the ingot to a homogenization heat treatment;
A hot rolling step for producing a hot-rolled sheet by hot rolling the ingot subjected to the homogenization heat treatment;
A cold rolling step of cold rolling the hot rolled sheet to produce a cold rolled sheet;
An annealing process for producing an aluminum alloy sheet by subjecting the cold-rolled sheet to an annealing rate of 50 ° C./min or more, an annealing temperature of 400 to 600 ° C., and a cooling rate of 50 ° C./min or more from the annealing temperature to 200 ° C. The manufacturing method of the aluminum alloy board characterized by including these.   The aluminum alloy is further Fe: 1.5 mass% or less, Mg: 2.0 mass% or less, Si: 1.5 mass% or less, Cu: 1.0 mass% or less, Cr: 0.5 mass% In the following, at least one of Zr: 0.5% by mass or less, V: 0.3% by mass or less, Ti: 0.2% by mass or less, and Zn: 1.5% by mass or less is included. The manufacturing method of the aluminum alloy plate of Claim 3.

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