JP5406745B2 - Aluminum alloy sheet with excellent ridging marks during molding - Google Patents

Description

  The present invention relates to an aluminum alloy plate excellent in ridging marks during molding (hereinafter, aluminum is also simply referred to as Al), and can suppress surface irregularities (also referred to as ridging marks and roping) that occur during press molding of panels. The present invention relates to an Al—Mg—Si aluminum alloy plate. The aluminum alloy plate referred to in the present invention refers to a plate that has been subjected to tempering such as solution treatment and quenching after rolling and before being formed into a panel by press molding or the like.

  In recent years, with respect to global environmental problems caused by exhaust gas and the like, improvement in fuel efficiency has been pursued by reducing the weight of the body of a transport aircraft such as an automobile. For this reason, in particular, the application of lighter aluminum alloy materials excellent in formability and bake hardenability is increasing in place of steel materials that have been used in the past for automobile bodies.

  Among these, panels such as outer panels (outer plates) and inner panels (inner plates) of panel structures such as automobile hoods, fenders, doors, roofs, and trunk lids are thin and high-strength aluminum alloy plates. The use of Al-Mg-Si-based AA to JIS 6000-based (hereinafter also simply referred to as 6000-based) aluminum alloy plates has been studied.

  The 6000 series aluminum alloy sheet basically contains Si and Mg as essential, and has excellent age-hardening ability. Therefore, in press forming and bending processing, formability is ensured by reducing the yield strength and forming. BH properties (bake hardness, artificial age hardening ability) that can ensure the required strength by age hardening by heating at the time of processing, such as paint baking treatment of the subsequent panel, and heat resistance during treatment. Paint bake hardenability).

  Further, the 6000 series aluminum alloy plate has a relatively small amount of alloy elements as compared with other 5000 series aluminum alloys having a large amount of alloy such as Mg. For this reason, when the scraps of these 6000 series aluminum alloy sheets are reused as the aluminum alloy melting material (melting raw material), the original 6000 series aluminum alloy ingot is easily obtained, and the recyclability is excellent.

  On the other hand, as is well known, an outer panel of an automobile is manufactured by combining an aluminum alloy plate with a forming process such as an extension forming in a press forming or a bending forming. For example, a large outer panel such as a hood or door is formed into a molded product shape as an outer panel by press molding such as overhanging, and then the inner panel and Are joined to form a panel structure.

  At this time, a panel after press molding using a 6000 series aluminum alloy plate as a raw material has a problem that surface rough defects such as ridging marks are likely to occur. The ridging mark is a phenomenon resulting from unevenness on the surface of the plate at the time of deformation such as press molding due to the texture arranged in the shape of stripes on the plate. For this reason, even if the crystal grains of the aluminum alloy plate as a raw material are fine enough not to cause rough skin, the point caused by press molding is troublesome.

  This ridging mark is particularly likely to occur when the press molding conditions become severe due to an increase in the size, complexity, or thickness of the panel structure. In addition, there is a problem that it becomes relatively inconspicuous immediately after press molding and becomes conspicuous after proceeding to the coating process as it is as a panel structure.

  When this ridging mark is generated, a panel structure for an outer plate (outer) or the like, which is required to have a particularly beautiful surface, has a problem in appearance and cannot be used. Conventionally, the ingot is cooled after homogenization heat treatment at a temperature of 500 ° C. or higher, or reheated after cooling to room temperature, and heated at a relatively low temperature of 350 to 450 ° C. It is known to prevent ridging marks on excess Si type 6000 series aluminum alloy plates by starting rolling or controlling the compound (see Patent Documents 1, 2, 3, and 10).

 Various methods for improving the ridging mark by controlling the texture (crystal orientation) of the 6000 series aluminum alloy plate have been proposed. For example, focusing on the crystal orientation component of the {100} plane, it has been proposed to refine the degree of Cube orientation accumulation in the plate surface layer portion to 2 to 5 and the crystal grain size of the plate surface portion to 45 μm or less ( (See Patent Document 4). In addition, it is also proposed to simultaneously define the distribution density of various orientations such as Cube orientation, rotational Cube orientation, Goss orientation, Brass orientation, CR orientation, RW orientation, S orientation, and PP orientation in 6000 series aluminum alloy plates. (See Patent Documents 5, 9, 10, 11, 12, and 13).

  Furthermore, it has also been proposed that the proportion of crystal grain boundaries whose adjacent crystal orientation difference is 15 ° or less is 20% or more (see Patent Document 6). It has also been proposed that the ear rate in a 6000 series aluminum alloy plate is 4% or more and the crystal grain size is 45 μm or less (see Patent Document 7). In addition, an aluminum alloy containing Mg, the area ratio occupied by crystal grains whose crystal plane orientation on the alloy surface is within 10 ° from the (100) plane, and crystal grains within 20 ° from the (100) plane It has also been proposed to make the area ratio occupied by a specific relationship (see Patent Document 8).

Japanese Patent No. 2823797 JP-A-8-232052 JP-A-7-228956 JP 11-189836 A JP-A-11-236639 JP 2003-171726 A Japanese Unexamined Patent Publication No. 2000-96175 JP 2005-146310 A JP 2004-292899 A JP 2005-240113 A JP 2008-45192 A JP 2008-223075 A JP 2007-200018

  The prior art has a certain effect in suppressing ridging marks, including controlling the texture and characteristics of the plates as in Patent Documents 4 to 9. However, when the molding conditions become more severe, such as molding into a deeper or more complicated three-dimensional panel, the effect is still insufficient.

  The present invention has been made by paying attention to such circumstances, and its purpose is to prevent ridging marks during press molding with high reproducibility, which becomes prominent when the molding conditions become more severe. An object of the present invention is to provide an Al—Mg—Si based aluminum alloy plate.

  In order to achieve this object, the gist of the aluminum alloy plate excellent in ridging mark property at the time of forming of the present invention is mass%, Mg: 0.1-3.0%, Si: 0.1-2. In an Al—Mg—Si-based aluminum alloy plate containing 5% and the balance consisting of Al and inevitable impurities, the texture of the region extending over the length of 10 mm in the plate width direction at the center of the plate width in the right-angle cross section of this plate The average area ratio in the sheet width direction of the Cube orientation is 8% or less, the difference between the maximum value and the minimum value of each area ratio in the sheet width direction of the Cube orientation is 8% or less, and the board width in the Goss direction The average area ratio in the direction is 2% or less, the difference between the maximum value and the minimum value of the area ratios in the sheet width direction of the Goss orientation is 3% or less, and further, in the sheet width direction of the rotating Cube orientation Rotational Cube orientation plate width with an average area ratio of 10% or less The difference between the maximum value and the minimum value among the area ratio of the direction is to be 8% or less.

  In the present invention, the ridging mark of the aluminum alloy plate, which until now has only been evaluated visually, was quantified and evaluated. Such quantification of ridging marks is performed by comparing and contrasting a plate (panel) in which a ridging mark is generated on a surface and a plate that is actually formed into a more complicated three-dimensional panel. It is obtained by measuring the shape of the surface of the plate with a tracer (three-dimensional shape measuring instrument).

  As a result of frequency analysis of the above three-dimensional shape data on the surface of the obtained plate (panel) by analysis software, when the molding conditions become more severe, the occurrence becomes significant. The generated ridging marks (surface irregularities) have a relatively large period in which the length in the plate width direction is about 2 to 3 mm.

  In other words, the ridging marks that become prominent when the molding conditions become more severe have a relatively large period of about 2 to 3 mm in the plate width direction. These facts are proved by Japanese Patent Application No. 2008-11766 prior to the present application.

  On the other hand, in the texture control technology of the plate in the above-mentioned conventional patent document, when analyzing and evaluating the ridging mark, the length in the plate width direction is about 3 mm at the maximum in an arbitrary perpendicular section of the plate. Can only be evaluated in a narrow area (length). Particularly, in the 6000 series aluminum alloy plate, the distribution density of various orientations such as Cube orientation, rotational Cube orientation, Goss orientation, Brass orientation, CR orientation, RW orientation, S orientation, PP orientation, etc. are simultaneously defined. , 9, 10, 11, 12, and 13 correspond to this.

  For example, in patent document 9, in the Example, in the area | region of 3 mm of board widths, the texture in the right-angled cross section of each board at the time of dividing | segmenting between this board width every 500 micrometers is measured. However, this means that the ridging mark having the large period can be evaluated only for one period at most. That is, in the texture control technology of the plate in the above-described conventional patent document, when the press molding conditions become more severe, the occurrence becomes remarkable, and the length in the plate width direction is about 2 to 3 mm. A ridging mark having a large period cannot be taken into account, including variations in surface irregularities. This is common not only to Patent Document 9 but also to the other patent documents. And this, coupled with the fact that the evaluation of the ridging marks was limited to visual qualitative evaluation, was one factor that the effect of suppressing the ridging marks was still insufficient even by the texture control of the conventional plate. It is assumed that

  In the present invention as well, the mechanism of ridging mark generation, in which the introduction strain amount (crystalline deformation amount) of adjacent crystal grains differs depending on the crystal orientation of the plate, and ridging marks that are uneven surface irregularities are likely to occur. In addition, the perception of this mechanism is the same as in the above-mentioned patent document that defines the crystal orientation.

  However, in the present invention, in consideration of the period of the ridging mark and the magnitude of the fluctuation, the state of the texture in the relatively wide area exceeding the period of the ridging mark in the Al-Mg-Si based aluminum alloy plate is specified. And the point which improves a moldability differs greatly first. In the present invention, the state of the texture in an arbitrary region extending over the entire plate thickness and the length in the plate width direction of 10 mm in an arbitrary perpendicular cross section of the plate is defined to improve the formability.

  In the present invention, among the textures in such a relatively wide area in the plate width direction, in particular, the Goss orientation, the Cube orientation, and the rotational Cube orientation are selected as control targets. That is, not only can these three orientations be regulated by the respective average area ratios in a relatively wide area in the plate width direction in the cross section of the plate at a right angle, but also a relatively wide area in the plate width direction. Minimize fluctuations in these directions in the region.

  As a result, in the present invention, the generation of ridging marks having a relatively large period becomes prominent when the molding conditions become more severe, such as being formed into a deeper or more complex three-dimensional panel. Can be prevented.

  Hereinafter, embodiments of the aluminum alloy sheet of the present invention will be specifically described in the order of texture, component composition, and production method.

(Gathering organization)
The Goss orientation, the Cube orientation, and the rotational Cube orientation have very large in-plane anisotropy of r value (Rankford value) compared to other orientations, and in the Goss orientation, when the plate is pulled in the width direction, There is almost no reduction in plate thickness. When the Goss orientation having such characteristics is present in the structure in a substantial amount, when the plate is press-molded, the elongation deformation ability differs depending on the portion of the plate, particularly the portion in the width direction of the plate, and extends in the width direction of the plate. Elongation deformation capacity is reduced.

  On the other hand, the Cube orientation is the main orientation of the recrystallized texture of aluminum, as is generally known, and is one of the main crystal orientations in Al-Mg-Si alloys. The Cube orientation and the rotated Cube orientation in which the Cube orientation is rotated are different from the behavior of the Goss orientation, and when the plate is pulled in the 45 ° direction with respect to the rolling direction, the plate thickness is remarkably reduced.

  In this way, when there are many Goss orientations, Cube orientations and rotational Cube orientations in which the thickness reduction behavior is completely different (largely) in the texture at the same time, when the product plate is press-molded, naturally, The state of occurrence of unevenness on the surface of the plate varies greatly over the region, particularly in the width direction of the plate.

  According to the recognition of the present inventors, the distribution state of each of these Goss azimuth direction, Cube azimuth direction, and rotating Cube azimuth direction in a relatively wide area in the plate width direction described above is when the molding conditions become more severe. This is the main cause of ridging marks (large irregularities on the plate surface). For this reason, in the present invention, in order to suppress this ridging mark, the size of each of these Goss azimuth, Cube azimuth, and rotational Cube azimuth is limited by the area ratio in a relatively wide area of the plate. In addition, the deviation (variation) of each of these directions existing in the relatively wide area is minimized.

  Specifically, in an Al—Mg—Si-based aluminum alloy plate, an average area in the plate width direction of the Cube orientation as a texture of a region extending in a plate width direction of 10 mm in an arbitrary perpendicular section of the plate. When the rate is 8% or less, the difference between the maximum value and the minimum value of each area rate in the plate width direction of the Cube orientation is 8% or less, and the average area rate in the plate width direction of the Goss orientation is 2% or less. The difference between the maximum value and the minimum value of the area ratios in the sheet width direction of the Goss orientation is 3% or less, and the average area ratio in the sheet width direction of the rotational Cube orientation is 10% or less. The difference between the maximum value and the minimum value of the area ratios in the plate width direction of the rotating Cube orientation is 8% or less.

  As described above, the ridging marks (surface irregularities) generated on the Al—Mg—Si based aluminum alloy plate have a relatively large period in which the length in the plate width direction is about 2 to 3 mm. For this reason, the average value of the respective area ratios in the plate width direction of the Goss orientation, the Cube orientation, and the rotational Cube orientation in a cross section at a right angle in a relatively large (wide) measurement range over a length of 10 mm or more at the minimum. It is necessary to suppress the fluctuations below the upper limit values described above.

  This reduces the Goss orientation and the Cube orientation in the texture that causes ridging marks and the texture that causes ridging marks in the width direction of the Al—Mg—Si-based aluminum alloy plate. The fluctuation of the is also sufficiently small. As a result, the main factor of ridging marks has been eliminated, and even when the molding conditions for deeper or more complex three-dimensional panels such as overhang molding of large automobile panels such as hoods and doors have become more severe. The surface quality of the plate is greatly improved.

  As described above, the ridging marks that become prominent when the molding conditions become more severe have a relatively large period of about 2 to 3 mm in length in the plate width direction. When analyzing the texture in a right-angle cross section of the plate when such a ridging mark is generated on the plate, first, the Goss orientation, the Cube orientation, and the rotational Cube orientation are too developed, and the average area ratio is the present invention. Exceeding the upper limit, each is too large.

  On the other hand, when the side of the ridging mark having a relatively large period is analyzed, first, the change in the plate width direction of the unevenness of the plate surface is relatively large, and the length of the unevenness of the ridging mark in the plate width direction is first. The length (change) has a relatively large period of about 2 to 3 mm. Corresponding to the length (change) of the unevenness of the ridging mark in the plate width direction, the respective area ratios of the Goss orientation and the Cube orientation also change in the plate width direction in the right-angle cross section of the plate.

  This is in contrast to the fact that changes in the area ratio of other orientations such as the Brass orientation, S orientation, and Cu orientation are relatively small. In other words, the other crystal orientations other than the Goss orientation, the Cube orientation, and the rotational Cube orientation, such as the Brass orientation, the S orientation, and the Cu orientation, generate ridging marks having a relatively large period of about 2 to 3 mm. Does not affect much. Therefore, crystal orientations other than the Goss orientation, the Cube orientation, and the rotational Cube orientation need not be regulated for the ridging marks having a relatively large period, and the Goss orientation, the Cube orientation, and the rotational Cube orientation A substantial amount may also be present in the measurement region in the plate width direction in the right-angle cross section of the plate.

  In the present invention, the value of the length of 10 mm in the plate width direction in the right-angle cross section of the plate, which is the texture measurement range, is about 2 to 3 mm of the unevenness length (change) of the ridging mark in the plate width direction. It is defined as the minimum necessary measurement condition that can cope with a relatively large period and can reliably suppress ridging marks.

(Measurement of texture of aluminum alloy sheet)
The formation of the texture differs depending on the processing method even if the crystal system is the same. That is, as shown below, the rolling surface is represented by {xxx} and the rolling direction is represented by <ΔΔΔ>. In addition, (circle) and (triangle | delta) have shown the integer.

Based on such an expression method, each direction is expressed as follows. The expression of each orientation is described in “Cross Texture” written by Shinichi Nagashima (published by Maruzen Co., Ltd.), “Light Metal” Explanation Vol.43 (1993) P.285-293, etc.
Cube orientation: {001} <100>
Rotating Cube orientation: {001} <310> to {001} <110>
Goss orientation: {011} <100>
Brass orientation: {011} <211>
S orientation: {123} <634>
Cu orientation: {112} <111>
(Or D orientation: {4411} <11118>)
SB orientation: {681} <112>

(Measurement of crystal orientation component abundance)
For the area ratio (existence ratio) of each crystal orientation component of these crystal grains, a backscattered electron diffraction image EBSP (Electron Backscatter Diffraction Pattern) obtained by scanning electron microscope SEM (Scanning Electron Microscope) was used for the above-described plate cross section. Measured by crystal orientation analysis method (SEM / EBSP method).

  In the crystal orientation analysis method using the EBSP, the surface of the sample set in the SEM column is irradiated with an electron beam to project the EBSP on the screen. This is taken with a high-sensitivity camera and captured as an image on a computer. In the computer, the orientation of the crystal is determined by analyzing this image and comparing it with a pattern obtained by simulation using a known crystal system.

  The crystal orientation analysis method using the EBSP is not a measurement for each crystal grain, but is performed by scanning a specified sample region at an arbitrary fixed interval, and the above process is automatically performed for all measurement points. Therefore, tens of thousands to hundreds of thousands of crystal orientation data are obtained at the end of measurement. For this reason, there is an advantage that the observation field is wide and the average crystal grain size, the standard deviation of the average crystal grain size, or the information of the orientation analysis can be obtained within a few hours for a large number of crystal grains. Therefore, it is optimal when the above-mentioned wide-area texture in the plate width direction is specified or measured as in the present invention.

  On the other hand, in X-ray diffraction (X-ray diffraction intensity, etc.) generally used for texture measurement, a relatively micro area for each crystal grain as compared with the crystal orientation analysis method using EBSP. This means that the organization (texture) is measured. For this reason, the wide-area structure (texture structure) in the plate width direction that affects the ridging mark cannot be measured as accurately and efficiently as the crystal orientation analysis method using the EBSP.

In the crystal orientation analysis method using the EBSP, a specimen for observing a structure is taken from each cross section of the plate, subjected to mechanical polishing and buffing, and then subjected to electrolytic polishing to adjust the surface. For the test piece thus obtained, as an SEM device, for example, SEM (JEOLJSM5410) manufactured by JEOL Ltd., for example, EBSP measurement / analysis system manufactured by TSL: OIM (Orientation Imaging Macrograph, analysis software name “OIMA Analysis”) is used. Then, it is determined whether each crystal grain has a target orientation (within 15 ° from the ideal orientation), and an area ratio for each orientation in the measurement visual field is obtained. The measurement area of the test piece is an area where the length in the plate width direction of the plate width central portion (center portion in the plate width direction) in the right-angle cross section of the plate extends over 10 mm over the entire plate thickness. The average area ratio of the azimuth and the difference between the maximum value and the minimum value of each area ratio are averaged. The measurement step interval is, for example, 10 μm or less. As a method of evaluating the difference between the maximum value and the minimum value of each area ratio, an area over 10 mm in the plate width direction is divided into lengths (for example, every 250 μm) in the plate width direction, and each area within the divided areas is divided. The area ratio of each azimuth is calculated, the maximum value and the minimum value are extracted for each azimuth in the obtained group of area ratios for each azimuth, and the difference is taken for each azimuth. The region where the length in the plate width direction of the central portion of the plate width extends over 10 mm is a region having a length of 10 mm in the plate width direction that sandwiches or includes the central portion of the plate width, and includes or includes the central portion of the plate width. As long as it is present, the central portion of the plate width does not necessarily have to be in the central portion of the region (not necessarily symmetrical with respect to the central portion of the plate width).
Several places (for example, three places) provided with an appropriate distance in the rolling direction of the test piece are measured for the difference between the maximum value and the minimum value of the average area ratio for each direction and the area ratio for each direction. To average.

  At this time, the Kikuchi pattern is obtained from the reflected electrons of the electron beam incident on the sample surface for the measurement region of the material to be measured. At this time, if the electron beam is scanned two-dimensionally on the sample surface and the crystal orientation is measured at every predetermined pitch, the orientation distribution on the sample surface can be measured. Next, the obtained Kikuchi pattern is analyzed to know the crystal orientation at the electron beam incident position. That is, the obtained Kikuchi pattern is compared with data of a known crystal structure, and the crystal orientation at the measurement point is obtained. Similarly, the crystal orientation of the measurement point adjacent to the measurement point is obtained, and those whose crystal orientation difference is within ± 5 ° belong to the same crystal grain (deemed). In addition, when the orientation difference between both crystals exceeds ± 5 °, the interval is defined as a grain boundary. In this way, the distribution of crystal grains on the sample surface is obtained.

(Chemical composition)
The chemical component composition of the present invention 6000 series aluminum alloy sheet will be described. The 6000 series aluminum alloy plate for the body of a transport machine such as an automobile targeted by the present invention is a bending process including excellent formability, BH property and hemming property as a plate for an outer panel of an automobile described above. Properties such as property, strength, weldability and corrosion resistance are required.

  In order to satisfy such a requirement, the composition of the aluminum alloy plate is, by mass%, Mg: 0.1-3.0%, Si: 0.1-2.5%, the balance being Al and unavoidable It shall consist of mechanical impurities. In addition,% display of content of each element means the mass% altogether.

  The 6000 series aluminum alloy plate of the present invention is an excess Si type 6000 series aluminum alloy plate having a ridging mark that is easily generated but having a better BH property and a Si / Mg mass ratio of Si / Mg of 1 or more. Applied and preferred. The 6000 series aluminum alloy sheet secures formability by reducing the yield strength during press molding and bending, and is age-hardened by heating during relatively low temperature artificial aging treatment such as paint baking treatment of the panel after molding. Yield strength is improved, and it has excellent age-hardening ability (BH property) that can secure the required strength. Among these, the excess Si type 6000 series aluminum alloy plate is more excellent in this BH property than the 6000 series aluminum alloy plate having a mass ratio Si / Mg of less than 1.

  Other elements other than Mg and Si are basically impurities, and the content (allowable amount) of each impurity level in accordance with AA to JIS standards. However, from the viewpoint of recycling, not only high-purity Al bullion but also 6000 series alloys and other aluminum alloy scrap materials, low-purity Al bullion, etc. Other elements may be mixed as impurities. Then, reducing these impurity elements to, for example, below the detection limit itself increases the cost, and a certain amount of allowance is required. Moreover, even if contained in a substantial amount, there is a content range that does not hinder the object and effect of the present invention, and in this range, there is an effect of improving the strength and refinement of crystal grains depending on elements such as Fe, Mn, Cu, Ti.

  Therefore, these impurity elements are allowed to be contained within the ranges specified below. Specifically, the aluminum alloy plate is in mass%, Fe: 1.0% or less, Mn: 1.0% or less, Cr: 0.3% or less, Zr: 0.3% or less, V : 0.3% or less, Ti: 0.1% or less, Cu: 1.0% or less, Ag: 0.2% or less, Zn: 1.0% or less are allowed to be included. Here, all the definitions of these elements do not include 0%.

  The preferable content range and significance of each element in the 6000 series aluminum alloy, or the allowable amount will be described below.

Si: 0.1-2.5%
Si, together with Mg, forms aging precipitates that contribute to strength improvement during solid tempering and artificial aging treatment at low temperatures such as paint baking treatment, and exhibits age-hardening ability, which is necessary as an outer panel for automobiles. For example, it is an essential element for obtaining the required strength (proof strength) of 180 MPa or more. Therefore, in the excess Si type 6000 series aluminum alloy plate of the present invention, it is the most important element for combining various properties of bending workability such as press formability and hemming.

  In addition, in order to demonstrate the excellent low-temperature age-hardening ability of 180 MPa or more after the low-temperature paint baking treatment after molding on the panel (at the time of low-temperature aging treatment at 170 ° C. × 20 minutes after applying 2% stretch) It is preferable to have an excess Si type 6000 series aluminum alloy composition in which Si / Mg is 1.0 or more by mass and Si is excessively contained with respect to Mg.

  When the Si content is less than 0.1%, the age-hardening ability and further various properties such as press formability and bending workability required for each application cannot be obtained. Furthermore, recrystallization is promoted by soaking and hot rolling, and the Goss orientation and the Cube orientation are easily developed, and the Goss orientation and the Cube orientation cannot be suppressed and controlled within the scope of the present invention. On the other hand, when Si exceeds 2.5%, press formability including bending workability and ridging mark property is remarkably inhibited. Furthermore, weldability is also significantly impaired. Therefore, Si is in the range of 0.1 to 2.5%, preferably in the range of 0.6 to 1.2%.

Mg: 0.1-3.0%
Mg forms an aging precipitate that contributes to strength improvement together with Si during the above-mentioned artificial aging treatment such as solid solution strengthening and paint baking treatment, and exhibits age-hardening ability. As a panel, for example, a required proof stress of 180 MPa or more It is an essential element for obtaining.

  If the Mg content is less than 0.1%, the absolute amount is insufficient, so that the compound phase cannot be formed during the artificial aging treatment, and the age hardening ability cannot be exhibited. For this reason, the required proof stress of 180 MPa or more necessary for the panel cannot be obtained. Furthermore, recrystallization is promoted by soaking and hot rolling, and the Goss orientation and the Cube orientation are easily developed, and the Goss orientation and the Cube orientation cannot be suppressed and controlled within the scope of the present invention.

  On the other hand, when Mg exceeds 3.0%, the formability such as press formability and bending workability including ridging mark property is significantly inhibited. Therefore, the Mg content is in the range of 0.1 to 3.0%, preferably such that Si / Mg is 1.0 or more by mass ratio. When the Si content is in the range of 0.6 to 1.2%, the Mg content is preferably in the range of 0.2 to 0.7%.

(Production method)
Next, a method for producing the aluminum alloy plate of the present invention will be described below. The aluminum alloy sheet of the present invention is a conventional process or a known process, and the aluminum alloy ingot having the above-mentioned 6000 series component composition is subjected to homogenization heat treatment after casting, and then subjected to hot rolling and cold rolling to obtain a predetermined process. It is manufactured by being subjected to a tempering treatment such as solution hardening and quenching. However, among these, in order to control the texture (Goss orientation, Cube orientation and rotational Cube orientation) within the scope of the present invention in order to improve the ridging mark property, the following homogenization heat treatment conditions and subsequent hot rolling conditions are used. It is necessary to appropriately control the annealing conditions.
In this regard, in particular, in the present invention, the aluminum alloy sheet of the present invention can be obtained in the following two types of steps (steps A and B).
Step A: Twice soaking (average cooling rate after first soaking is 40 ° C./over), hot rolling, (roughening), cold rolling, intermediate annealing, cold rolling, solution treatment The point of this A step is heat By developing the processed structure as much as possible in the rolling process (reducing the coiling temperature for hot rolling finishing) and recrystallizing by intermediate annealing, the development of the Cube orientation, Goss orientation, and rotating Cube orientation is suppressed. In view of strength, intermediate annealing is a rapid heating and rapid cooling process. When the intermediate annealing step is omitted in the step A, it is also inferior to the intermediate annealing step, although increasing the coiling temperature of the hot rolling and promoting the recrystallization therefor additionally contributes to ridging.
Process B: Twice soaking (two-stage cooling after the first soaking), hot rolling, (rough), cold rolling, solution treatment The point of this B process is to suppress fine precipitation during soaking. , By promoting repeated fine recrystallization in hot rolling (especially rough rolling process), it suppresses the development of Cube orientation, Goss orientation, and rotational Cube orientation (in Step A, there are many fine precipitates, so recrystallization It is suppressed, and repeated recrystallization effects cannot be obtained by rough rolling). As a result, even if the intermediate annealing step is omitted, the same ridging suppression effect as that in the step having the intermediate annealing step A can be obtained. Since the intermediate annealing step can be omitted, it is not particularly necessary to lower the coiling temperature for hot rolling finish. Rather, it is possible to further improve the ridging effect by increasing the finish coiling temperature to promote recrystallization. Even in the B step, it is possible to obtain good ridging characteristics by further providing an intermediate annealing step.

(Melting, casting)
First, in the melting and casting process, both the A process and the B process are usually performed by using a molten aluminum alloy adjusted to be dissolved within the above-mentioned 6000 series component composition range, such as a continuous casting method and a semi-continuous casting method (DC casting method). The melt casting method is appropriately selected for casting.

(Homogenization heat treatment)
Next, the cast aluminum alloy ingot is subjected to homogenization heat treatment (soaking). In both the A and B steps, the homogenization heat treatment temperature itself is appropriately selected as a homogenization temperature of 500 ° C. or higher and lower than the melting point as usual. As a result, alloy elements and coarse compounds are sufficiently dissolved. In addition, the structure is homogenized to eliminate segregation in crystal grains in the ingot structure. If this soaking temperature is low, alloy elements and coarse compounds cannot be sufficiently dissolved, and segregation in crystal grains acting as a starting point of fracture cannot be sufficiently eliminated. It is not possible to satisfy various properties such as formability, bending workability, BH property, and strength required as.

  This soaking is preferably carried out by two soakings in which soaking is performed twice instead of the usual one soaking. That is, after the first homogenization heat treatment, the aluminum alloy ingot is once cooled to room temperature or near room temperature, and then re-heated at a soaking temperature lower than that of the first soaking treatment. Do heat. Then, after this second soaking, hot rolling is performed by cooling or heating to the hot rolling start temperature. This double soaking suppresses the formation of coarse recrystallized grains (hot fibers) during hot rolling even with an excess Si type 6000 series aluminum alloy plate, and makes the structure uniform during recrystallization. The ridging mark property at the time of molding can be improved.

Among these, in particular, with respect to the step A, the cooling after the first homogenization heat treatment is forcibly air-cooling the ingot with a fan in the soaking furnace or outside the furnace, regardless of the size of the ingot. The average cooling rate after the homogenization heat treatment is preferably 40 ° C./hr or more. By setting such a cooling rate, it is possible to control the compound such as Mg ₂ Si in the ingot to an appropriate size and distribution. Even with an excess Si type 6000 aluminum alloy plate, a coarse re- The formation of crystal grains (hot fiber) can be suppressed, the structure can be homogenized during recrystallization, and the ridging mark property can be improved. When the cooling rate after the homogenization heat treatment is low, precipitates such as MgSi are coarsened and are likely to become formation sites for Goss orientation, Cube orientation, and rotational Cube orientation. For this reason, even when soaking is performed twice, Goss orientation, Cube orientation, and rotational Cube orientation are likely to develop in the texture of the product plate. In addition, strength, bake hard performance, bending workability and the like may be reduced.

On the other hand, with respect to the B process, the ingot cooling process after the first homogenization heat treatment is performed by changing the cooling rate to two stages. This makes it easier to obtain the texture of the present invention in which fluctuations in the Goss orientation, Cube orientation, and rotational Cube orientation existing in a relatively wide area in the plate width direction are minimized. Specifically, the cooling from the homogenization heat treatment temperature to a temperature of 400 to 500 ° C. is a slow cooling with a relatively slow average cooling rate of 1 to 20 ° C./hr, and from the temperature of 400 to 500 ° C. The cooling is performed in two stages with a relatively fast average cooling rate of 30 to 60 ° C./hr. In this case, in particular, the gradual cooling in the previous stage precipitates in the ingot during the cooling process and suppresses fine precipitates that are an impediment to recrystallization, thereby promoting recrystallization in the hot rolling process. In particular, in the rough rolling process, the structure is finely recrystallized by repeated recrystallization effects. As a result, the Goss orientation, Cube orientation, and rotational Cube orientation fluctuations present in a relatively wide area in the plate width direction in the processed texture during production are reduced, as the final product cold rolled sheet, These orientation fluctuations are also reduced. In other words, as a result of these azimuth fluctuations being reduced in the upper process, these azimuth fluctuations carried over to the lower process (final product cold-rolled sheet) are also reduced. However, if the ingot after the first homogenization heat treatment is continuously cooled to room temperature by the slow cooling, the precipitates become too coarse, and on the contrary, the properties such as strength, formability and bending workability are deteriorated. Let Moreover, since it takes a lot of time for cooling, productivity is also lowered, which is not preferable as a mass production process. Incidentally, the slow cooling of the preceding stage is controlled by an operation such as furnace cooling in the furnace, and the relatively fast cooling of the latter stage is controlled by an operation such as leaving outside the furnace.
Even if it is an excess Si type 6000 series aluminum alloy sheet, the generation of coarse recrystallized grains (hot fiber) during hot rolling is suppressed by the two-step soaking process under the above conditions. It is possible to homogenize the structure and improve the ridging mark property during molding. In addition, since the alloy element is sufficiently dissolved, various characteristics such as formability, bending workability, BH property, and strength required for an automobile panel can be satisfied.

(Hot rolling)
In the hot rolling, both the A process and the B process are performed by roughly rolling a ingot (slab) according to the sheet thickness to be rolled and a sheet having a sheet thickness of approximately 40 mm or less after the rough rolling by approximately 4 mm or less. And a finish rolling process for rolling to a plate thickness. In these rough rolling process and finish rolling process, a reverse type or a tandem type rolling mill is used as appropriate, and rolling consisting of a plurality of passes is performed.

  Here, in both the A process and the B process, the hot rolling reduction ratio (working rate) may be normal in order not to develop the texture structure of Goss orientation, Cube orientation and rotational Cube orientation in the texture of the product plate. However, in the step of performing the annealing after the end of hot rolling, it is preferable to hot-roll at a low temperature and accumulate strain for uniform fine recrystallization at the time of the annealing (annealing) after the hot rolling. For this reason, it is preferable that the hot rolling start temperature is 300 to 400 ° C., and the hot rolling end temperature is 280 ° C. or lower.

  When the hot rolling start temperature exceeds 400 ° C., recrystallization occurs, coarse recrystallized grains are generated during hot rolling, and the texture of Goss orientation, Cube orientation and rotational Cube orientation causes ridging marks. However, it becomes easy to form the same orientation grain group. Moreover, if the hot rolling start temperature is less than 300 ° C., the hot rolling itself becomes difficult. Further, when the end temperature of hot rolling exceeds 280 ° C., the excessive Si type 6000 series aluminum alloy sheet is particularly likely to be recrystallized, and uniform fine recrystallization at the time of roughening (annealing) after hot rolling. Is inhibited.

  As described above, in the present invention, the ingot after the homogenization heat treatment is cooled to start hot rolling at a lower temperature, and in the case of a roughening process, the ingot is heated at a lower temperature below the recrystallization temperature. The hot rolling is finished and the hot rolled sheet is made into a texture mainly composed of a processed structure that does not recrystallize. For this reason, it is possible to suppress the formation of coarse recrystallized grains that cause ridging marks during hot rolling.

(Roughing of hot-rolled sheet)
When the hot rolled sheet is not subjected to roughening (annealing) before cold rolling, both the process A and the process B can improve the efficiency of sheet manufacture and reduce the manufacturing cost. At the same time, however, the coarse precipitates generated during hot rolling cannot be re-dissolved even under the low temperature hot rolling conditions. For this reason, coarse precipitates that form formation sites of Goss orientation, Cube orientation, and rotational Cube orientation remain in the hot-rolled sheet, and the texture of the product plate (Goss orientation, Cube orientation, and rotational Cube orientation) is within the scope of the present invention. ) Is more likely to be uncontrollable. In order to re-dissolve the coarse precipitate, the rough temperature is 350 ° C. or higher and the melting point or lower.

  However, this roughening needs to be performed by rapid heating and holding at high temperature for a short time, and it is necessary to perform it in a continuous annealing furnace instead of a batch type. This is common in the solution treatment described later, but even when using a batch annealing furnace or a continuous annealing furnace, the rate of temperature rise to the heat treatment temperature for re-solution of coarse precipitates, When the cooling rate from the heat treatment temperature is low, the Mg—Si compound or simple substance Si precipitates coarsely and remains until after the heat treatment. This is because the Goss orientation, the Cube orientation, and the rotational Cube orientation are easily developed. This is the same even when the high temperature holding time at this heat treatment temperature is too long. For this reason, it is preferable that the average temperature increase rate to roughening shall be 100 degree-C / min or more. Further, the holding time at the rough temperature is preferably as short as 0 to several minutes of the continuous annealing furnace. Furthermore, it is preferable that the cooling treatment after the roughening is performed by selecting and using water cooling means and conditions such as air cooling such as a fan, mist, spray, and immersion, respectively, and rapid cooling with an average cooling rate of 10 ° C./second or more.

  Here, in both the A process and the B process, this roughening may be omitted and cold rolling may be performed. However, in the case of the A process, the intermediate annealing of the cold-rolled sheet in the middle of the cold rolling described later is essential at least once. In the case of the B process, the intermediate annealing of the cold rolled sheet during the cold rolling is not necessary due to the effect of promoting recrystallization at the time of hot rolling by suppressing the fine precipitation in the soaking process. Further, in the case where the roughening is omitted, in order to promote recrystallization at the end of hot rolling in both step A and step B, the end temperature may be higher than 300 ° C. (preferably 340 ° C. As described above, the effect of suppressing the formation of coarse recrystallized grains that cause ridging marks is reduced, and the effect of improving ridging marks is reduced, when compared with conditions where the hot rolling end temperature is 280 ° C. or lower and roughening is performed. .

(Cold rolling)
In both the A process and the B process, in the cold rolling, the hot-rolled sheet is rolled to produce a cold-rolled sheet (including a coil) having a desired final product sheet thickness.

(Intermediate annealing)
However, in the process A, the intermediate annealing of the cold-rolled sheet is essential at least once during the cold rolling. When this intermediate annealing is not performed, it is possible to increase the efficiency of plate manufacture and reduce the manufacturing cost. However, at the same time, Goss orientation, Cube orientation, and rotation Cube orientation formation and development during cold rolling, especially the formation and development of rotation Cube orientation cannot be canceled and suppressed by annealing. For this reason, at a normal cold rolling rate, the Goss orientation, the Cube orientation, and particularly the rotational Cube orientation develop during cold rolling, and it is highly possible that the texture of the product plate cannot be controlled within the scope of the present invention.

  For this reason, intermediate annealing is performed once or more in the temperature range of 350 to 570 ° C. during the cold rolling. When the intermediate annealing temperature is less than 350 ° C., the effect of canceling and suppressing the Goss orientation, the Cube orientation, and the rotating Cube orientation formed or developed during cold rolling is weak. On the other hand, if the intermediate annealing temperature exceeds 570 ° C., burning tends to occur and the formability deteriorates.

  However, this intermediate annealing also needs to be carried out under rapid heating and high temperature short time keeping under the same conditions as the above-mentioned roughening and for the same reason as the above-mentioned roughening, not a batch type but a continuous type. It is necessary to carry out in an annealing furnace. In addition, in the said B process, as above-mentioned, the intermediate annealing of the cold rolled sheet in the middle of cold rolling is unnecessary.

(Solution and quenching)
In both the A step and the B step, in the final solution treatment and quenching treatment, in order to suppress the ridging marks on the product plate and to suppress the Goss orientation and the Cube orientation, the average temperature increase rate of the final solution treatment is set. It is preferable to set it as 100 degree-C / min or more. The solution treatment temperature of the solution treatment is preferably 500 ° C. or higher in order to sufficiently precipitate aging precipitates that contribute to strength improvement by artificial aging treatment such as paint baking hardening after press molding of the plate, Perform in the following temperature range.

  Also, in the quenching treatment from the solution treatment temperature, if the cooling rate is slow, Si, Mg2 Si, etc. are likely to precipitate on the grain boundary, which tends to be the starting point of cracks during press molding and bending, and these formability descend. In order to ensure this cooling rate, the quenching treatment is performed by selecting and using water cooling means and conditions such as air cooling such as a fan, mist, spray, and immersion, respectively, and an average cooling rate of 10 ° C./second or more. Is preferred.

  In the present invention, in order to further enhance the age-hardening property in the artificial age-hardening treatment such as the paint baking process of the molded panel, a pre-aging treatment is performed after the quenching treatment in order to promote the precipitation of the age-related precipitates that contribute to strength improvement. You may do it. This preliminary aging treatment is preferably held in a temperature range of 60 to 150 ° C., preferably 70 to 120 ° C. for a required time of 1 to 24 hours. As the preliminary aging treatment, the cooling end temperature of the quenching treatment is increased to 60 to 150 ° C., and then immediately reheated or held as it is. Alternatively, after the solution treatment, after the quenching treatment to room temperature, it is immediately reheated to 60 to 150 ° C. within 5 minutes.

  Furthermore, in order to suppress aging at room temperature, heat treatment (artificial aging treatment) at a relatively low temperature may be performed after the preliminary aging treatment without time delay. When the time delay is present, room temperature aging (natural aging) occurs with time even after the preliminary aging treatment, and after the room temperature aging occurs, the effect of the heat treatment at the relatively low temperature is exhibited. It becomes difficult.

  In the case of continuous solution quenching, the quenching process is completed within the preliminary aging temperature range and wound around a coil. In addition, you may reheat before winding up to a coil, and you may heat-retain after winding. Moreover, after the quenching process to room temperature, it may be reheated to the above temperature range and wound at a high temperature.

  In addition to this, it is of course possible to further increase the strength by performing aging treatment or stabilization treatment at a higher temperature according to the application or required characteristics.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.

  Next, examples of the present invention will be described. First, regarding the A process, as Example 1, a 6000 series aluminum alloy plate having the composition shown in Table 1 was soaked and hot-rolled under each production condition shown in Table 2, and further subjected to roughening and intermediate treatment. Sandwiched cold rolling, solution treatment and quenching treatment were performed. In addition, in the display of the content of each element in Table 1, the display of “−” indicates that it is below the detection limit.

  More specific production conditions for the aluminum alloy plate are as follows. Ingots having a composition of 1 to 12 shown in Table 1 having a thickness of 100 mm, a width of 400 mm, and a length of 1 m were commonly melted by a DC casting method.

  When the soaking process is performed twice during the soaking process of the ingot, the average heating rate of 40 ° C./hr and the ultimate temperature of 560 ° C. are common to each example as the first soaking conditions. Then, a soaking process was performed in which the cooling time was once cooled to room temperature at a holding time of 6 hours and an average cooling rate of 60 ° C./hr. Thereafter, a second soaking condition was performed by reheating and holding at the treatment temperature (° C.) and the holding time (hr) shown in Table 2.

  Immediately after this soaking process, in common with each example, it is cooled or reheated to the hot rolling start temperature (° C.) shown in Table 2, and hot rolling is started at this temperature. gave. However, Invention Examples 9 to 11 and Comparative Example 17 do not perform the second soaking condition, and are cooled to the hot rolling start temperature (° C.) shown in Table 2 after the first soaking process or left as it is. Hot rolling was started (one soaking). Table 2 also shows the end temperature of hot rolling (finish rolling) in each example. These hot rolling conditions were carried out under the preferred temperature conditions described above in common with each example.

  Then, these hot-rolled sheets were subjected to an average heating rate (° C./min), a processing temperature (° C.), an average cooling rate (° C./second) shown in Table 2 in a stone furnace or an atmospheric furnace before cold rolling. In addition, the holding time was set to 4 to 5 seconds in common in each example, and the annealing was selectively performed in a continuous heat treatment furnace. And the cooling after hold | maintaining to a rough temperature was immediately performed by water cooling or the mist spray of water, and it cooled to room temperature with the said cooling rate. For comparison, the comparative example was also carried out when this roughening was omitted.

  These hot-rolled sheets were commonly cold-rolled at a cold rolling rate of 80% in common with each example to obtain a cold-rolled sheet having a thickness of 1.0 mm. Cold rolling is performed with 4 passes, and in both cases, the average heating rate (° C./min) and processing temperature (° C.) shown in Table 2 are used in the same continuous heat treatment furnace as the above-mentioned rough after 2 passes. The intermediate cooling was performed once with an average cooling rate (° C./second) and a holding time of 1 to 3 seconds in common with each example. Cooling after maintaining the intermediate annealing temperature was immediately performed by water cooling or water mist spraying, and cooled to room temperature at the cooling rate. In addition, in the comparative example, the example which abbreviate | omitted this intermediate annealing was also implemented for the comparison.

  The cold-rolled sheet after cold rolling is held in the same heat treatment furnace as the intermediate annealing at the average heating rate (° C./min), processing temperature (° C.), and average cooling rate (° C./second) shown in Table 2. The solution treatment was performed for 1 to 3 seconds in common with each example. Cooling after maintaining the solution treatment temperature was immediately performed by water cooling or water mist spraying, and cooled to room temperature at the average cooling rate and quenched. Further, a preliminary aging (reheating) treatment was performed within 5 minutes after quenching (immediately) at a temperature of 100 ° C. for 2 hours. After this preliminary aging treatment, it was gradually cooled at 0.6 ° C./hr to obtain a T4 tempered material.

  A test plate (blank) was cut out from each final product plate after the tempering treatment, and the structure and characteristics of each test plate after room temperature aging (room temperature standing) on the 15th day after the tempering treatment were measured and evaluated. . These results are shown in Table 3.

(Test plate structure)
The texture of the test plate after room temperature aging for 15 days after the tempering treatment was measured and analyzed using the SEM-EBSP. This test plate was simulated for severe press forming of an automobile body panel, and 15% stretch (tensile deformation) was applied in the plate width direction (perpendicular to the rolling), and the plate was perpendicular to the plate after this pre-strain was applied. The cross section (the cross section in the direction perpendicular to the rolling direction of the plate and in the plate width direction) was taken as the EBSP measurement surface. The EBSP measurement surface divides the plate width in the plate width direction in the plate width direction every 250 μm in the plate width direction with the length in the plate width direction (left and right direction of the plate) sandwiching the center portion of the plate width in the middle. It was set as the area. In other words, the area ratio obtained by averaging the average values of the area ratios of the Goss orientation, the Cube orientation, and the rotating Cube orientation in each section of the plate at the divided portions was defined as the average area ratio of each orientation. Further, the difference between the maximum value and the minimum value among the area ratios of the Goss orientation, the Cube orientation, and the rotational Cube orientation was measured and used as an index of variation for each orientation component. The measurement was performed at three locations with appropriate intervals in the rolling direction, and the respective area ratios were averaged.

(Test plate characteristics)
Further, as the characteristics of the test plate, ridging mark property, 0.2% yield strength (As yield strength: MPa), and elongation (%) were measured.

Ridging mark properties:
The ridging mark property simulates the coating of an automobile body panel on the plate after applying the pre-strain, and after the zinc phosphate treatment, the cationic electrodeposition coating is performed, and further the paint bake hardening treatment is simulated. Evaluation was carried out by visual observation of the plate surface after the annealing treatment. Specifically, the pre-strained plate is sequentially subjected to a titanium phosphate colloid dispersion treatment and a zinc phosphate treatment in which the plate is immersed in a zinc phosphate bath containing a low concentration (50 ppm) of fluorine. A zinc film was formed on the plate surface, and after further cationic electrodeposition coating, annealing was performed at 170 ° C. for 20 minutes.

  A ridging mark was not generated on the painted surface of the plate after the pre-straining was imparted, and a product evaluated as having excellent press formability was evaluated as ◎. Moreover, although a ridging mark was generated, a relatively mild one was evaluated as ◯ as being capable of press molding depending on molding conditions. Furthermore, a large ridging mark was generated, and a case where the press formability (ridging mark property) was judged to be poor even when the molding conditions were changed was evaluated as x.

Mechanical properties of the test plate:
A tensile test for measuring 0.2% proof stress (As proof stress: MPa) and elongation (%) of the test plate was performed in the same tester as the tensile tester for applying the pre-strain. That is, JISZ2201 No. 5 test piece (25 mm × 50 mmGL × plate thickness) was collected from an aluminum alloy plate after room temperature aging for 15 days after the tempering treatment, and was subjected to room temperature tension. The tensile direction of the test piece at this time was the direction perpendicular to the rolling direction. The tensile speed was 5 mm / min up to 0.2% proof stress and 20 mm / min after proof stress. The N number was 5, and the 0.2% proof stress and elongation were average values thereof.

  As shown in Tables 1 and 2, each of the inventive examples is produced within the composition range of the present invention and in a preferable condition range. For this reason, as shown in Table 3, it has a texture defined in the present invention. That is, in order to suppress the ridging marks, not only the Goss orientation, the Cube orientation, and the rotational Cube orientation in the relatively wide area of the above-mentioned plate are restricted, but Goss existing in this relatively wide area. Deviations between the azimuth, the Cube azimuth, and the rotational Cube azimuth are also reduced as much as possible.

  As a result, each of the inventive examples is excellent in ridging mark properties even in the example of a 6000 series aluminum alloy plate having an excess Si type composition that has been aged at room temperature after the tempering treatment and has reduced formability. It also has excellent mechanical properties such as strength and elongation. However, as shown in Table 2, Invention Examples 10 to 12 (one or two soaking treatments) that are not commonly subjected to roughening are Invention Examples 1 to 8 (one or two soaking) that are commonly subject to roughening ( The ridging mark property is slightly inferior as a whole as compared with Invention Example 9 (one soaking).

  On the other hand, Comparative Examples 17-21 use the same alloy example as the said invention example. However, as shown in Table 2, these comparative examples are out of the preferable range of manufacturing conditions. In Comparative Example 17, only one-time soaking is performed, the hot rolling start and end temperatures are too high, and the rate of temperature increase during roughening is too small. Although the comparative examples 18 and 19 are also soaking twice, the hot rolling start or end temperature required in the case of soaking twice is too high. The comparative example 20 is a two-step soaking process, and although the hot rolling end temperature is low, the necessary roughening is not performed in this case. Comparative Example 21 is not subjected to intermediate annealing during cold rolling. As a result, these comparative examples have inferior ridging marks as compared with the above-described invention examples.

  Moreover, Comparative Examples 13-16 remove | exclude contents, such as Mg and Si, from the scope of the present invention. For this reason, as shown in Table 2, these comparative examples have production conditions within a preferable range and satisfy the provisions of the texture of the present invention, but are inferior in mechanical properties such as strength and elongation than the above invention examples. Yes.

  Therefore, the results of the above examples support the critical significance or effect for combining the ridging mark properties, mechanical properties, etc., of the requirements of the components and structures in the present invention, or preferred production conditions.

  Next, regarding the B process, as Example 2, a 6000 series aluminum alloy plate having the composition of No. 1 in Table 1 was subjected to soaking and hot rolling under each production condition shown in Table 4, cold rolling, It was manufactured by chemical treatment and quenching treatment. In addition, all the intermediate annealing processes in the middle of cold rolling were made into nothing. Cooling after maintaining the rough temperature was immediately performed by water mist spraying as in Example 1 and cooled to room temperature.

  The concrete production conditions of the aluminum alloy plate are the same as the ingot melting conditions in Example 1, and in the two soaking processes of the ingot, the same soaking conditions are used in each example. As an average heating rate of 40 ° C./hr, an ultimate temperature of 560 ° C., and a holding time of 6 hr, a soaking treatment was performed to cool to room temperature. However, in common with each invention example, as shown in Table 4, after the first soaking, cooling from the soaking temperature to a temperature of 400 to 500 ° C. is performed at an average cooling rate of 1 to 20 ° C./hr. The cooling from the temperature of 400 to 500 ° C. to 200 ° C. was performed in two stages with an average cooling rate of 30 to 60 ° C./hr. The gradual cooling of the former stage was controlled by the furnace cooling in the furnace, and the relatively fast cooling of the latter stage was controlled by leaving it outside the furnace. Thereafter, the second soaking process shown in Table 4 was performed again at a processing temperature of 400 ° C. and a holding time of 6 hours.

  Immediately after this soaking process, in common with each example, cooling or reheating to each hot rolling start temperature (° C.) shown in Table 2, or starting hot rolling at the same temperature, up to a thickness of 5.0 mm Hot rolled. In common with each example, these hot-rolled sheets were cold-rolled at a cold rolling rate of 80% in the same manner as in Example 1 to obtain a cold-rolled sheet having a thickness of 1.0 mm. Cold rolling was performed with 4 passes.

  This cold-rolled sheet was subjected to the same continuous heat treatment furnace as the intermediate annealing, with the average heating rate (° C./min), processing temperature (° C.), average cooling rate (° C./second) shown in Table 2, and the holding time was In each example, the solution treatment was performed for 1 to 3 seconds. Cooling after maintaining the solution treatment temperature was immediately performed by water mist spraying, and cooling and quenching to room temperature at the average cooling rate. Further, a preliminary aging (reheating) treatment was performed within 5 minutes after quenching (immediately) at a temperature of 100 ° C. for 2 hours. After this preliminary aging treatment, it was gradually cooled at 0.6 ° C./hr to obtain a T4 tempered material.

  The test plate (blank) was cut out from each final product plate after the tempering treatment, and the structure and characteristics of each test plate after room temperature aging (room temperature standing) on the 15th day after the tempering treatment were described in Example 1. In the same manner as above, measurement and evaluation were performed in the same manner. These results are shown in Table 5.

  As shown in Table 4, Invention Examples 22 to 26 are produced within the composition range of the present invention and in a preferable condition range. The ingot after the first homogenization heat treatment is cooled in two stages under the preferable conditions. For this reason, as shown in Table 5, the texture defined in the present invention is obtained even under conditions in which intermediate annealing is not performed. That is, in order to suppress ridging marks, fluctuations in Goss orientation, Cube orientation, and rotational Cube orientation that exist in a relatively wide area in the plate width direction are reduced. Further, the invention example 27 subjected to the roughening also has a texture defined by the present invention.

  As a result, these inventive examples 22 to 26 are excellent in ridging mark properties, strength and elongation even in the case of a 6000 series aluminum alloy plate having an excess Si type composition that has been aged at room temperature after the tempering treatment and has reduced formability. Excellent mechanical properties. In addition, Invention Example 27 subjected to roughening has excellent ridging mark properties and excellent mechanical properties such as strength and elongation even when the hot rolling end temperature is less than 300 ° C.

  In contrast, in Comparative Examples 28 and 29 in Table 4, the cooling of the ingot after the first homogenization heat treatment is performed only in one stage of slow cooling or rapid cooling. As a result, as shown in Table 5, these comparative examples do not satisfy the provisions of the texture of the present invention under conditions without roughening or intermediate annealing, and exist in a relatively wide area in the plate width direction. The Goss orientation, Cube orientation, and rotational Cube orientation vary greatly, and the ridging mark property is inferior.

  These results support the significance of cooling the ingot after the first homogenization heat treatment in two stages under the preferred conditions. As described above, in this two-stage cooling, in particular, the gradual cooling in the first stage suppresses fine precipitates that inhibit recrystallization and precipitate in the ingot during the cooling process. Crystals are promoted. As a result, the variation of each orientation existing in a relatively wide area in the plate width direction in the processed texture during manufacture is reduced, and these orientation variations as a final product cold-rolled plate are also reduced. It can be said that

  According to the present invention, it is possible to provide a 6000 series aluminum alloy plate that can prevent ridging marks during press molding, which are prominent when the molding conditions become more severe, and is excellent in mechanical properties. As a result, the application of the 6000 series aluminum alloy plate can be expanded for transporting devices such as automobiles, ships or vehicles, home appliances, buildings, structural members and parts, and particularly for transporting devices such as automobiles. .

Claims (1)

  In an Al—Mg—Si-based aluminum alloy plate containing, by mass%, Mg: 0.1 to 3.0%, Si: 0.1 to 2.5%, the balance being Al and inevitable impurities, As the texture of the region over the length of 10 mm in the plate width direction at the center of the plate width in the right-angle cross section, the average area ratio in the plate width direction of the Cube orientation is 8% or less, and each area ratio in the plate width direction of the Cube orientation The difference between the maximum value and the minimum value is 8% or less, the average area ratio in the plate width direction of Goss orientation is 2% or less, and the maximum value among the area ratios in the plate width direction of Goss orientation is The difference from the minimum value is 3% or less, and the average area ratio in the plate width direction of the rotating Cube orientation is 10% or less. The ridging mark at the time of molding, characterized in that the difference from the value is 8% or less Excellent aluminum alloy plate.