JP5865582B2 - Aluminum alloy plate for forming process excellent in bending workability and manufacturing method thereof - Google Patents

Description

  This invention is a molding process used as a raw material for various automobiles such as automobile body seats and body panels, ships, aircraft, etc., parts, building materials, structural materials, other various machinery and appliances, home appliances and parts thereof, etc. In particular, the present invention relates to an aluminum alloy plate for use in forming, and particularly to an aluminum alloy plate for forming having excellent bending workability.

  Conventionally, cold rolled steel sheets were often used for automobile body seats, but recently there has been a growing demand for lighter automobiles to improve fuel economy in order to reduce global warming and reduce energy costs. Therefore, instead of the conventional cold-rolled steel sheet, there is an increasing tendency to use an aluminum alloy plate having substantially the same strength as the cold-rolled steel sheet and a specific gravity of about 1/3 for the body sheet of an automobile. Recently, aluminum alloy plates are often used for molded parts such as panels and chassis of electronic / electrical devices other than automobiles.

  One of the characteristics required for an aluminum alloy for forming is bending workability. For example, in car body seats, hemming is often used to integrate the outer panel and inner panel, but hemming is a 180 degree bend with an extremely small bend radius. Therefore, it can be said that the bending process is extremely severe. Therefore, in these applications, it is strongly required to have excellent bending workability among moldability. Hem processing is often performed over almost the entire periphery of the edge of the panel, so it is desirable that the variation in bendability is small in all directions within the plate surface, that is, the bending anisotropy is small. It is.

  By the way, it is known that the bending workability is generally greatly influenced by the texture. Therefore, as a conventional technique, a technique for improving the bending workability by controlling a specific crystal orientation in the texture. In particular, there are techniques disclosed in Patent Documents 1 and 2 in which bending workability is improved by increasing the density of the orientation in which the {001} plane is parallel to the plate surface.

JP 2003-226927 A JP 2003-277870 A

  In the conventional technology in which the specific crystal orientation in the texture as described above is controlled, there is a certain effect in improving the bending workability. However, it is still not enough to perform a severe bending process of 180 ° bending of 1 mm or less, and there is a strong demand for the development of a technique that can improve bending workability more reliably and stably.

  The present invention has been made against the background of the above circumstances, such as automobile body sheets, ships, aircraft, and other members, parts, building materials, structural materials, other various machinery and equipment, home appliances, and parts thereof. As an aluminum alloy for forming process that is used after being subjected to forming process including bending process, an aluminum alloy sheet for forming process that is particularly excellent in bending processability, and an aluminum alloy sheet for forming process that has a small bending anisotropy, It is another object of the present invention to provide a manufacturing method thereof.

  As a result of various experiments and examinations by the present inventors to solve the above-described problems, the texture of the specific region near the plate surface on the side corresponding to the outside of the bend is defined as each of the conventional techniques. It has been newly found that an aluminum alloy sheet for forming excellent in bending workability can be obtained by regulating in different modes.

  To explain the findings, conventionally, as texture control for improving bending workability, attention has been focused solely on increasing the density of the orientation in which the {001} plane is parallel to the plate surface. The researchers reexamined the relationship between the texture and bending workability, and found that the bending workability was the value of the Taylor factor in the region up to a specific depth near the outer surface of the bend (assuming that the bending work was plane strain deformation). It was found that the bending workability was better as the average Taylor factor in the region was smaller.

  That is, the value of the average Taylor factor when the bending process is considered to be plane strain deformation in the region from the plate surface (particularly the plate surface corresponding to the outside of the bend) to the depth of 1/4 of the total plate thickness is specified. The mean Taylor factor in the above-mentioned region for any direction in the plane perpendicular to the plate thickness direction (in the plane parallel to the plate surface of the original plate before bending) By controlling the texture so that the value is within the above specific range, it has been found that an aluminum alloy plate having excellent bending workability can be obtained reliably and stably, and the present invention has been made. is there.

Here, the Taylor factor is a factor related to the macroscopic yielding behavior of the metal polycrystal, and corresponds to the reciprocal of the Schmid factor, and is one of the indexes representing the ease of plastic working. More specifically, when the polycrystalline body yields macroscopically, τ _y is an average decomposition shear stress (macroscopic stress) necessary for causing multiple slips, and uniaxial yield stress due to tensile deformation is σ _y. Then, the following general formula τ _y = σ _y / M
The factor of M is called the Taylor factor. Since the value of this Taylor factor is affected by the texture of the material, it can be an index that represents the state of the texture. On the other hand, it has recently become possible to calculate the value of the Taylor factor relatively easily using analysis software from the measurement result of texture orientation information by an electron diffractometer or the like. Until now, sufficient research has not been done on the relationship with the Taylor factor. However, the present inventors can control the bending workability more effectively and reliably than the density of a specific crystal orientation that has been used to represent the control state of the texture in the past by using the value of the Taylor factor. I found out.

Specifically, the aluminum alloy sheet for forming according to the invention of claim 1 is an aluminum alloy sheet for forming that is used after being bent, and is formed from the surface of at least one of the plate surfaces to the entire plate. The value of the average Taylor factor when the bending process is regarded as plane strain deformation in the region up to a depth of 1/4 of the thickness is 0 ° to 180 ° in the plane perpendicular to the plate thickness direction . der 3.50 in each direction as measured in each direction of 5 ° increments in the range is, moreover absolute value of the difference between the maximum value and the minimum value in the in-plane each direction value of the average Taylor factor It is characterized by being 0.30 or less .

Furthermore, the aluminum alloy sheet for forming according to the invention of claim 2 is characterized in that in the aluminum alloy for forming process described in claim 1, the ASTM crystal grain size is 4 or more.

Furthermore, the invention of claim 3 is the aluminum alloy sheet for forming according to claim 1, wherein the aluminum alloy includes an Al—Mg—Si alloy, an Al—Mg—Si—Cu alloy, an Al—Mg alloy, One type selected from an Al—Zn—Mg based alloy, an Al—Cu based alloy, and an Al—Mn based alloy is used.

  On the other hand, in the method for producing an aluminum alloy sheet for forming according to the invention of claim 4, the aluminum alloy sheet for forming according to claim 1 is manufactured by homogenizing the ingot of the raw material aluminum alloy, Two or more passes of cross rolling for cold rolling and then rolling in a direction different from the rolling direction of hot rolling, and a normal rolling pass for rolling in the same direction as the hot rolling direction. And the final pass is the normal rolling pass, followed by recrystallization heat treatment.

According to this invention, as an aluminum alloy plate for forming processing that is used after being subjected to severe bending processing represented by hem processing, within the region from the plate surface to a position at a depth of 1/4 of the total plate thickness. When the bending process is regarded as plane strain deformation, the average Taylor factor value is measured in each direction in increments of 5 ° within the range of 0 ° to 180 ° in the plane perpendicular to the plate thickness direction . By controlling to be 3.50 or less in each direction, excellent bending workability can be ensured reliably and stably, and the value of the average Taylor factor in the region is orthogonal to the plate thickness direction. by the absolute value and 0.30 of the difference between the maximum value and the minimum value in the in-plane each direction, the bending of the anisotropy, could be reduced reliably and stably.

FIG. 1 is a schematic diagram of an aluminum alloy plate at the time of bending for conceptually explaining that the deformation at the time of bending the aluminum alloy plate is regarded as plane strain deformation as a premise of the present invention. FIG. FIG. 2 is a schematic diagram of an aluminum alloy plate at the time of bending for explaining a region from the plate surface corresponding to the outside of the bending to a position at a depth of 1/4 of the total plate thickness, as defined in the present invention. FIG. FIG. 3 shows an aluminum alloy at the time of bending for explaining the bending direction Q taken in the plane perpendicular to the thickness direction of the aluminum alloy plate in this invention with respect to the final pass direction L of the cold rolling of the plate. It is a typical perspective view of a board. FIG. 4 is a sample of bending workability evaluation used in the examples of the present invention.

  The type of aluminum alloy used in the aluminum alloy sheet for forming according to the present invention is not particularly limited, and Al-Mg-Si alloy or Al-Mg, which is widely used as a body sheet or panel of an automobile body. -Si-Cu alloys (so-called 6000 series alloys, such as AA6061 alloy), Al-Mg alloys (so-called 5000 series alloys, such as AA5083 alloy), Al-Cu alloys (so-called 2000 series alloys, For example, AA2017 alloy), Al-Zn-Mg alloy (so-called 7000 series alloy, such as AA7075 alloy), Al-Mn alloy (so-called 3000 series alloy, such as AA3004 alloy), and other various aluminum alloys. Can be used.

  Further, the specific component composition of each alloy type is not particularly limited. For example, as an Al-Mg-Si alloy or an Al-Mg-Si-Cu alloy, Mg 0.2 to 1.5% (mass%, the same applies hereinafter) ), Si 0.3-2.0%, Mn 0.03-0.6%, Cr 0.01-0.4%, Zr 0.01-0.4%, V 0.01-0.4% Fe, 0.03 to 1.0%, Ti 0.005 to 0.3%, Zn, 0.03 to 2.5%, one or more selected from Cu, 1.5% Cu The following are typical, and the balance is made of Al and inevitable impurities.

  In addition, the Al-Mg alloy contains 2.0 to 6.5% of Mg, and the balance contains Al and inevitable impurities, or contains 0.05 to 1.8% of Cu in addition to the above Mg. In addition to the above alloy or Mg or Mg and Cu, Mn 0.03 to 1.0%, Cr 0.03 to 0.3%, Zr 0.03 to 0.3% and V 0.03 to 0.3% Of these, those containing one or more of them are typical.

  Moreover, as an Al-Cu type-alloy, it contains Cu1.5-7.0%, Mg1.8% or less, Mn1.2% or less, Fe1.5% or less, Cr0.4% or less, Zr0.3% In the following, typically, one containing two or more selected from Zn 0.5% or less and Ti 0.3% or less, with the balance consisting of Al and inevitable impurities is typical.

  Further, the Al-Zn-Mg alloy contains Zn 0.8 to 7.0%, Mg 0.5 to 3.0%, and Cu 3.0% or less, Mn 1.0% or less, Cr 0.4% or less. Zr 0.3% or less, Ti 0.3% or less is typically contained, one or more selected from the group consisting of Al and inevitable impurities.

  The Al-Mn alloy contains 0.3 to 1.5% of Mn, 1.5% or less of Mg, 0.5% or less of Cu, 0.3% or less of Cr, 0.3% or less of Zr, and 0.4% of Zn. In the following, typically, one containing two or more selected from 0.3% or less of Ti and the balance consisting of Al and inevitable impurities is representative.

In order to improve the bending workability in the aluminum alloy sheet for forming, it is important to control the texture. However, in the case of this invention, it is not the idea to improve the bending workability by accumulating a specific crystal orientation or crystal face in a certain direction or a face as in the prior art, but the bending work is subjected to plane strain deformation. This is based on a novel idea to improve the bending workability surely and stably by controlling the value of the Taylor factor when considered as within a specific condition range. That is, as a result of intensive studies by the present inventors, the value of the average Taylor factor in the region from the plate surface corresponding to the outside of the bending in the bending process to a position at a depth of 1/4 of the total plate thickness is appropriately set. By controlling at a proper level and within an appropriate range , excellent bending workability could be realized.

That is , the value of the average Taylor factor in the region from the plate surface to the position at a depth of 1/4 of the total plate thickness when the bending process is regarded as plane strain deformation is in the plane orthogonal to the plate thickness direction. By satisfying the condition that it is 3.50 or less in any direction, it is possible to ensure excellent bending workability.

Such Taylor factor conditions will now be described in more detail.
First, in order to measure and calculate the Taylor factor in bending, it is necessary to regard the bending as plane distortion deformation. That is, as schematically shown in FIG. 1, when bending the aluminum alloy plate 1, its bending direction Q (however, the bending direction Q in this case is the state of the base plate before bending). In the plane including the plate surface 1A on the outer side of the bend) and the plane including the plate thickness direction (plate cross section in the thickness direction), tensile-compressive stress acts, tensile strain, compression Distortion occurs. If the x-axis and y-axis of the three-dimensional orthogonal coordinate system are taken in this plane and the plane is taken as the xy plane, almost no stress acts in the z-axis direction orthogonal to the z-axis direction. Therefore, it is not displaced in the z-axis direction, and distortion in the z-axis direction can be ignored. In this way, assuming that distortion occurs only in the xy plane (a plane parallel to the plate thickness direction) means that “bending is regarded as plane distortion deformation”. In the present invention, the value of the Taylor factor is obtained as a value indicating the Taylor factor in a strain state similar to bending, that is, the superiority or inferiority of the bending workability, by considering it as plane strain deformation as described above.

  In addition, if “the mean value of the Taylor factor in the region from the plate surface to the position at a depth of ¼ of the total plate thickness” is described, this is as shown in FIG. When the aluminum alloy plate 1 is subjected to bending, the region 11 when the region 11 from the surface 1A which is the outside of the bending to the position of 1/4 of the plate thickness t in the depth direction is taken. Means the average Taylor factor value. When actually obtaining the value of the average Taylor factor in the region 11, for example, with respect to a cross section parallel to the plate thickness direction of the plate, all the regions in the region 11 from the plate surface to a depth of ¼ of the total plate thickness. The texture is measured and the orientation information in the entire area is obtained, the orientation information is converted into orientation information in a plane perpendicular to the thickness direction by calculation, and bending processing is performed from the orientation information. What is necessary is just to obtain | require the value of the average Taylor factor in the surface orthogonal to the plate | board thickness direction when it is regarded as plane distortion deformation. Here, the measurement of the texture of the cross section of the plate is performed for the entire region from the plate surface to a position at a depth of 1/4 of the total plate thickness, so that it is orthogonal to the plate thickness direction finally obtained by calculation. The value of the average Taylor factor in the plane to be used is the average value of the Taylor factor in the region.

  Here, the reason why the region from the plate surface to the position of 1/4 of the plate thickness is defined is as follows. That is, as is well known, in bending, tension is applied to the outside of the bend and compression is applied to the inside of the bend. In most of the deformation processes of the bending process, the first starting point of breakage is a portion near the outer surface of the bending where the tension acts. Therefore, the bending workability of the plate is mainly affected by the structure of the region near the outer surface of the bend, particularly in the region from the bending surface to 1/4 of the plate thickness, and from the outer surface of the bend to 1/4 of the plate thickness. This is because the tissue state of the region inside the bend from the position of can be ignored. From the experiments by the present inventors, it has been confirmed that the value of the Taylor factor on the inner side of the bending than the position of ¼ of the plate thickness actually has little influence on the bending workability. Here, as is clear from the above description, the texture of the region in the vicinity of the surface on the plate surface side corresponding to the outer side of the bending of the two plate surfaces of the plate is defined by the present invention. If regulated by the conditions, excellent bending workability can be secured, and there is no need to regulate the area near the surface on the opposite side, that is, the side of the plate corresponding to the inside of the bend, but the actual aluminum alloy plate In this manufacturing process, the structure near the surface on the side of one plate surface of the plate and the structure near the surface on the side of the other plate surface are substantially equivalent if the depth from the surface is equal. Usually, when the product plate provided by the rolling manufacturer is bent on the user side, it is often uncertain which plate surface is outside the bending process. Then, we will regulate the average Taylor value It is not particularly specified whether the “area up to a depth of ¼ of the total thickness” is on the side of the outer or inner side of the bending at the time of bending, and the side of at least one side It was decided that the above condition should be satisfied. Of course, theoretically, it is sufficient if the condition of the average Taylor value is satisfied for the region near the outside of the bend, but it is uncertain which surface will be bent outside the bend at the user stage. In this case, it is desirable to satisfy the average Taylor factor condition for the regions on both sides of the plate.

Furthermore, “3.50 or less in an arbitrary direction in a plane perpendicular to the plate thickness direction” has the following meaning. That is, in the body sheet of an automobile, hem bending is often performed over the entire circumference of the outer edge portion, and in that case, bending is not limited to a specific direction with respect to the rolling direction of the base plate, It will be applied in all directions of 360 °. Even in the case of other general bending processes, it is extremely rare that the direction of the bending process is determined in advance when the aluminum alloy sheet product is supplied to the user. Therefore, in order to always prevent the user from breaking due to severe bending, it is desirable that the bending workability is excellent in all directions (any direction) in the plate surface of the base plate. From this point of view, it is necessary that the value of the average Taylor factor is within a predetermined range in an arbitrary direction within the plate surface of the base plate. For example, the cold rolling final pass direction of the plate (Note: As will be described later, the optimum method for producing the aluminum alloy plate of the present invention is as the cold rolling after hot rolling. It is preferable to combine a cross rolling pass crossing at a predetermined angle with respect to the direction and a normal rolling pass in the same direction as the hot rolling method, but the final pass of the cold rolling in that case is the hot rolling direction. If the bending direction Q is orthogonal to the L direction (see FIG. 3A), the bending direction Q is parallel to the L direction. In any case (see (B) of FIG. 3) and when the bending direction Q is various angles θ other than 0 ° and 90 ° with respect to the L direction (see (C) of FIG. 3) The mean value of the Taylor factor in each case also needs to be 3.50 or less.
In addition, as described above, the value of the average Taylor factor is originally desired to be 3.50 or less in an arbitrary direction in a plane orthogonal to the plate thickness direction, but in practice, any direction in the plane ( It is not possible to measure in all directions that are infinite. Therefore, in the present invention, if the value of the Taylor factor measured in each direction of minute angle increments of 5 ° satisfies the above condition, it is considered that the above condition is satisfied in substantially any direction. The condition of the value of the Taylor factor in each direction when measured in each direction of ° is defined in claim 1.

Even in the above range, in order to have a higher level of bending workability, an arbitrary direction in a plane orthogonal to the plate thickness direction (range of 0 ° to 180 ° in the plane orthogonal to the plate thickness direction). The average value of the Taylor factor in each direction when measured in 5 ° increments is preferably 3.20 or less, and more preferably 3.05 or less.

Furthermore, in addition to the condition for the upper limit of the average Taylor factor as described above, when bending is considered as plane strain deformation in the region from the plate surface to a position at a depth of 1/4 of the total plate thickness . In-plane directions perpendicular to the thickness direction of the average Taylor factor (each direction measured in 5 ° increments within the range of 0 ° to 180 ° in the plane perpendicular to the thickness direction) By satisfying the condition that the absolute value of the difference between the maximum value and the minimum value is not more than 0.30, it is possible to obtain an aluminum alloy sheet having not only excellent bending workability but also low bending anisotropy. it can. Here, the absolute value of the difference between the maximum value and the minimum value in each of the in-plane directions orthogonal to the plate thickness direction is 0.30 or less. In any bending direction, the variation of the average Taylor factor is always within 0.30. This means that there is little variation in the average Taylor factor depending on the bending direction, because it has excellent bendability in any bending direction, that is, there is little anisotropy of bending workability. This is particularly advantageous in the case where hemming is performed over the entire periphery of the edge of the plate.

  As described above, the absolute value of the difference between the maximum value and the minimum value depending on the bending direction of the mean Taylor factor is preferably within 0.2, more preferably within 0.05 in order to further reduce the bending anisotropy. Is desirable.

  Furthermore, not only the value of the Taylor factor as described above but also the size of the crystal grains of the plate, that is, the crystal grain size, affects the bending workability. That is, if the crystal grains become excessively coarse, bending workability may be reduced, and as a result of repeated experiments and examinations by the present inventors, the value of the average Taylor factor is only regulated as described above. In addition, it was found that the decrease in bending workability can be prevented more reliably by setting the crystal grain size to 4 or more in terms of ASTM crystal grain size, and the condition is defined in claim 3.

  Next, a method for measuring the value of the average Taylor factor in each bending direction as described above will be described.

  First, the texture in the region from the plate surface to a position at a depth of ¼ of the total plate thickness was measured with a backscattered electron diffraction measurement device (SEM-EBSD) attached to the scanning electron microscope. Specifically, after mechanical polishing and buffing were performed on the surface orthogonal to the plate width direction of the specimen for tissue observation, the processed layer was removed by electrolytic polishing. Orientation information is obtained by performing SEM-EBSD measurement over a sufficiently wide range containing 2000 or more crystal grains from the surface of the polished surface to a depth of 1/4 of the total thickness. did. The measured STEP size may be about 1/10 of the crystal grain size. Moreover, when the angle difference with the adjacent orientation was 5 ° or more, the boundary line between the adjacent orientations was regarded as the crystal grain boundary. In addition, if more than 2000 crystal grains cannot be measured in one field of view, use EBSD analysis software described later after measuring in multiple fields so that the total number of crystal grains in each field of view is 2000 or more. Then, the azimuth information of each visual field is combined into one data.

From the obtained orientation information, the Taylor factor is obtained by using EBSD analysis software. As the analysis software, for example, “OIM Analysis” manufactured by TSL may be used. Specifically, first, the azimuth information obtained by the above-described method is converted into azimuth information viewed from the thickness direction. Next, the bending process is regarded as plane strain deformation, and the Taylor factor in the plane orthogonal to the plate thickness direction is calculated, so that in the region from the plate surface to the position of the depth of 1/4 of the total plate thickness. The mean Taylor factor value was calculated. In the plane perpendicular to the plate thickness direction, each direction rotated in 5 ° increments up to 180 ° in the same plane, with the direction parallel to the plate longitudinal direction (rolling direction of the final pass of cold rolling) being 0 ° In the direction, the calculation of the average Taylor factor in the region from the plate surface to the position at a depth of 1/4 of the total plate thickness was performed. In this calculation, the active main slip system is assumed to be {111} <110>.

  Next, the ASTM crystal grain size was also calculated from the orientation information obtained by the above method. Specifically, using EBSD analysis software, after drawing the grain map when the boundary line where the angle difference with the adjacent orientation is 5 ° or more is regarded as the grain boundary, the ASTM grain size is cut by the cutting method. Was calculated.

  Next, a method for producing the aluminum alloy sheet for forming according to the present invention will be described.

  Basically, the production method is not particularly limited, and in short, an average Taylor factor in the region from the plate surface corresponding to the outside of the bending process to a position at a depth of 1/4 of the total plate thickness, Furthermore, the structure defined by the crystal grain size may be controlled so as to satisfy the above-described conditions, and various methods such as rolling, forging, extrusion, drawing, and pressing are conceivable. In addition, in hot rolling-cold rolling, and in cold rolling after hot rolling, as a cold rolling pass, a direction different from the hot rolling direction (usually 90 ° from the hot rolling direction). In order to obtain a plate that satisfies the above conditions, it is best to perform a combination of a cross rolling pass that is rolled in a direction that is rotated at an angle close to or at an angle close to that and a hot rolling direction in the same direction. is there. The manufacturing method in that case will be described below.

  For example, an aluminum alloy is first melted in accordance with a conventional method, and a normal casting method such as a continuous casting method or a semi-continuous casting method (DC casting method) is appropriately selected and cast.

  The obtained ingot is homogenized according to a conventional method, and then hot rolled according to a conventional general method. Although the homogenization treatment conditions are not particularly limited, it is usually preferably 450 ° C. or higher and 600 ° C. or lower, and preferably 0.5 hours or longer and 24 hours or shorter. However, it goes without saying that the most preferable conditions for the homogenization treatment conditions are slightly different depending on the target alloy type. In hot rolling after homogenization, after cooling to near normal temperature after homogenization, it may be heated again to the hot rolling start temperature, or cooled to the hot rolling start temperature in the cooling process after homogenization. The hot rolling may be started at that temperature, and which one is applied may be appropriately selected. The hot rolling conditions are not particularly limited, but usually, the hot rolling start temperature is preferably 250 ° C. or higher and 550 ° C. or lower, and the hot rolling end temperature is preferably 150 ° C. or higher and 450 ° C. or lower. However, it goes without saying that the most preferable conditions of the hot rolling conditions are slightly different depending on the target alloy type.

  Following hot rolling, if necessary, intermediate annealing is performed, and then cold rolling is performed to obtain a predetermined product sheet thickness. Here, the intermediate annealing conditions in the case of performing the intermediate annealing is not particularly limited, but in the case of batch annealing according to the target alloy type, the material arrival temperature is 300 ° C. or more, 450 ° C. or less, The holding time at the material reaching temperature is preferably 0.5 to 5 hours, and in the case of continuous annealing, it is preferably set to 350 to 580 ° C. within 5 minutes.

  As described above, as cold rolling, it is desirable to perform rolling combining a cross rolling pass for rolling in a direction different from the hot rolling direction and a pass in the same direction as the hot rolling direction. Specifically, as cold rolling by a plurality of passes, two or more passes of cross rolling that rolls in a direction different from the rolling direction of hot rolling, and a normal rolling pass that rolls in the same direction as the hot rolling direction, In order to obtain an aluminum alloy sheet that satisfies the Taylor factor as described above, it is optimal to perform rolling in which the final pass is a normal rolling pass. That is, by performing cold rolling including such a cross-rolling pass, it is 1/4 of the plate surface in any direction in the plane as defined in claim 1 and claim 2. It is possible to easily obtain a plate that satisfies the condition of the value of the average Taylor factor for the region up to the depth.

  Here, the rolling direction of the cross rolling pass may be a direction different from the hot rolling direction, but is usually preferably a direction rotated by 35 ° to 90 ° with respect to the hot rolling direction. In addition, from the viewpoint of ease of handling during rolling, the direction rotated by 90 ° is preferable. In the cold rolling including such a cross rolling pass, the number of cross rolling passes is preferably 2 passes or more, more preferably 3 passes or more. Further, it is preferable that the cross rolling pass and the normal rolling pass are alternately repeated. Here, two or more passes of cross rolling may be defined as one unit, and the cross rolling of one unit and the normal rolling pass may be alternately repeated. However, as a whole of the cold rolling, it is preferable that the final pass is not a cross rolling pass but a normal rolling pass in the same direction as the hot rolling direction. Here, the rolling reduction in each pass of the cross rolling is preferably about 3 to 30%, and the rolling reduction of each pass of the normal rolling is preferably about 3 to 30%. The total rolling rate of the cold rolling is not particularly limited, but is usually about 30% or more.

  As described above, in the state finished to the final sheet thickness by cold rolling including a cross-rolling pass, depending on the conditions, it may be possible to satisfy the provisions such as the above-mentioned Taylor factor even with the cold rolled material, Usually, it is preferable to subject the aluminum alloy sheet having a predetermined thickness after cold rolling to a recrystallization heat treatment or, depending on the alloy type, a recrystallization heat treatment that also serves as a solution treatment. It is possible to reliably and easily obtain an organization that satisfies the above conditions. That is, by recrystallizing the cold strain introduced by cold rolling including cross rolling as a recrystallization driving force, the condition of the average Taylor factor described above is satisfied in the region from the plate surface to a depth of 1/4. Thus, it becomes possible to easily obtain an aluminum alloy sheet for forming that is excellent in bending workability.

  Here, the recrystallization heat treatment is not particularly limited as long as it is a condition that causes complete recrystallization, but in the case of batch annealing, the material arrival temperature is set to 300 ° C. or more and 450 ° C. or less, and the material arrival The holding time at the temperature is preferably 0.5 to 5 hours, and in the case of continuous annealing, it is preferably within 5 minutes at 350 to 580 ° C. The most preferable conditions differ slightly depending on the alloy type of the target, but when the recrystallization heat treatment is excessively low temperature and short time, the recrystallization does not proceed sufficiently and a plate satisfying the Taylor factor condition as described above is obtained. On the other hand, in the case of excessive heat treatment at a high temperature for a long time, abnormal grain growth may be induced, and the Taylor factor condition as described above or the provision of the ASTM crystal grain size should be specified. Since there is a possibility that eutectic melting may occur as well as there is a possibility of not being satisfied, it is desirable to apply optimum conditions depending on the alloy type.

  In heat-treatable alloys, there may be a case where a recrystallization treatment is performed which also serves as a solution treatment. In this case, the material arrival temperature is 450 ° C. or more and 580 ° C. or less in continuous annealing, and the holding time at the material arrival temperature is Is preferably within 5 minutes. Depending on the target alloy type, if the material arrival temperature is less than 450 ° C, the effect of solution treatment cannot be obtained sufficiently. Therefore, the bake hardenability, which is one of the characteristics of heat-treatable alloys, is insufficient and paint baking. If the recrystallization temperature, which also serves as a solution treatment, is excessively high, resulting in later strength reduction, eutectic melting or recrystallization grain coarsening may occur. In addition, as an alloy type that performs heat treatment only for recrystallization without serving as a solution treatment, there are, for example, pure aluminum, Al-Mg alloy, and the like. On the other hand, recrystallization is also performed as a solution treatment. Examples of alloy types that are often treated include an Al—Zn—Mg alloy and an Al—Mg—Si alloy.

  For alloy types with high room temperature aging, such as Al-Zn-Mg and Al-Mg-Si-Cu, the material strength increases as the room temperature holding period from recrystallization heat treatment, which also serves as a solution treatment, to processing is longer. There is a possibility that the moldability is lowered. In order to alleviate such a change in properties due to room temperature aging, as a stabilization treatment after recrystallization heat treatment, continuous annealing within 50 minutes at 50 to 300 ° C. or batch annealing for 0.5 to 24 hours at 50 to 200 ° C. It is effective to do. If it is a stabilization treatment under these conditions, the texture is not particularly affected. Therefore, the texture obtained by the recrystallization treatment, that is, the texture satisfying the average Taylor factor condition defined in the present invention, It is maintained as it is after the stabilization process. Therefore, in the production method of the present invention, whether or not to perform the stabilization treatment after the recrystallization treatment is not an essential matter.

  Examples of the present invention will be described below together with comparative examples. The following examples are for explaining the effects of the present invention, and the processes and conditions described in the examples do not limit the technical scope of the present invention.

  Aluminum alloys having respective component compositions shown in alloy codes A to E in Table 1 were melted in accordance with a conventional method, and cast into a slab having a thickness of 70 mm by a DC casting method.

  Among the obtained slabs, slabs of alloy codes A and E were subjected to homogenization under conditions of 470 ° C. and 24 hours, and slabs of alloy codes B to D were subjected to 530 ° C. and 24 hours. Once allowed to cool to near room temperature. Next, after reheating at 450 ° C. for 2 hours, hot-rolled to the prescribed plate thicknesses listed in Table 2 and allowed to cool to near room temperature, then using a nitrite furnace at 450 ° C. for 5 minutes. Intermediate annealing was performed. Subsequent to the intermediate annealing, cold rolling, recrystallization heat treatment, and cooling to around room temperature were performed under the conditions described in Table 2. The cold rolling is performed in a plurality of passes, and at least as an embodiment of the present invention, a cross rolling pass in a direction rotated by 90 ° with respect to the hot rolling direction and a normal rolling in the same direction as the hot rolling direction are performed. Rolling combined with a pass was performed.

  Here, the description in Table 2 will be supplemented. First, the notation of “-” in the column labeled “Number of cross rolling passes” indicates that the cross rolling pass is not performed. Next, the numbers in the columns and the notation of arrows describing “regularity of cross rolling and normal rolling” indicate a combination method of the cross rolling pass and the normal rolling pass. For example, “1 → 1” means that the cross rolling pass and the normal rolling pass are alternately performed as “cross rolling 1 pass → normal rolling 1 pass → cross rolling 1 pass → normal rolling 1 pass →... "2 → 1" means "cross rolling pass and normal rolling pass like" cross rolling 2 pass-> normal rolling 1 pass-> cross rolling 2 pass-> normal rolling 1 pass-> ... " Means that In this embodiment, the cold rolling uses the combination described above as the basic unit of rolling, and does not end the rolling in the middle of the basic unit. For example, in “2 → 1”, the basic unit is a total of three passes of “cross rolling 2 passes → normal rolling 1 pass”. Was always one pass of normal rolling.

  Each plate material obtained as described above was subjected to SEM-EBSD measurement by the method described above, and the texture in the region from the plate surface to a position at a depth of 1/4 of the total plate thickness was measured. From the obtained orientation information, the average Taylor factor and ASTM grain size were calculated by the method described above. Table 3 shows the maximum value, the minimum value, the difference between the maximum value and the minimum value, and the ASTM crystal grain size in each direction obtained by calculation. It was. Here, in claim 1 of the present invention, since an upper limit value of the average Taylor factor value in a specific region in the plate thickness direction is defined for an arbitrary bending direction, measurement is performed as described above. If the maximum value of the calculated average Taylor value is 3.50 or less as defined in claim 1, it can be regarded that it is 3.50 or less in any direction.

  Bending test specimens were collected in the direction where the average value of the Taylor factor was maximum or minimum, and the 180 ° bending test was performed with a middle plate with a thickness of 1 mm (bending radius: 0.5 mm). Was compared with the bending workability evaluation sample shown in FIG. 4, and the bending workability in each direction was given a score (score). Specifically, the bending test and scoring were performed four or more times for each direction, and the average was used as the bending score. The results are shown in Table 3. The bending score indicates that the higher the value, the better the bending workability.

  Furthermore, JIS No. 5 test piece was cut out in the direction parallel to the rolling direction for each plate material obtained as described above, and the yield strength (YS) was evaluated by a tensile test. The results are also shown in Table 3.

Examples of manufacturing process numbers 1, 2, 5, 6, 9, 10, 13-15, 19, and 20 in Table 3 are all regions from the plate surface to a position at a depth of 1/4 of the total plate thickness. In which the Taylor factor of any bending direction satisfies the condition of 3.50 or less, but in the direction where the Taylor factor is the maximum, that is, the direction with the least bending workability compared to those not satisfying the condition. It was confirmed that the bending workability when compared was excellent.

In addition, each of the manufacturing process numbers 1, 2, 5, 6 satisfying the condition that the Taylor factor in an arbitrary bending direction in the region from the plate surface to a position at a depth of 1/4 of the total plate thickness satisfies 3.50 or less , 9, 10, 13 to 15, 19 , and 20 , in particular, the absolute value of the difference between the maximum value and the minimum value of the mean Taylor factor is 0.30 or less, production process numbers 2, 5, 6, 9, 10, and 14 15, 19, 20, the difference in the bending score is smaller than that in which the absolute value of the difference exceeds 0.30 (for example, manufacturing process numbers 1 and 13 as comparative examples) , that is, the bending anisotropy is small. It became. In the manufacturing process number 16, although the absolute value of the difference of the average Taylor factor in each direction does not satisfy the regulation, the difference in the bending score is small. This is thought to be due to poor processability.

  On the other hand, in the examples of production process numbers 3, 4, 7, 8, 11, 12, 16-18, 21, and 22, which are comparative examples, the bending workability in the direction in which the bending workability is most inferior, It was inferior to the example of the present invention. That is, in the example of production process numbers 11, 16, 17, and 21 in which only the normal cold rolling pass in the same direction as the hot rolling direction is performed without performing the cross rolling pass, the maximum value of the Taylor factor is 3.50. The bending workability has deteriorated from the example of the present invention.

  In addition, examples of manufacturing process numbers 4, 7, 8, and 12 in which only the cross rolling pass was performed as cold rolling, and manufacturing process numbers 3, 4, 8, 18, and 22 in which only one pass was cross-rolled were performed. Even in the example, the maximum value of the Taylor factor exceeded 3.50, and the bending workability deteriorated from the example of the present invention.

  Further, in the examples of production process numbers 4, 16, 18, and 22 in which the ASTM crystal grain size is less than 4, there is a case where the bending workability is lowered. For example, in the example of the manufacturing process number 16, the bending score in the direction of the minimum average Taylor factor is 4.0, which is the same as the example of the manufacturing process number 13 (the average Taylor factor is the minimum). It can be seen that the bending workability is greatly inferior to the bending score 7.0) in the direction of

DESCRIPTION OF SYMBOLS 1 Aluminum alloy plate 1A The plate surface 11 equivalent to the outer side of a bending 11 The area | region L from the plate surface equivalent to the outer side of a bending to the position of the depth of 1/4 of the total thickness in the plate thickness direction Q Bending direction in the plane parallel to the original plate surface
t Thickness

Claims (4)

A forming aluminum alloy sheet that is used after being bent;
The value of the average Taylor factor when the bending process is regarded as plane strain deformation in the region from the plate surface on the side of at least one plate surface to a position at a depth of 1/4 of the total plate thickness is the plate thickness. It is 3.50 or less in each direction when measured in each direction of 5 ° within a range of 0 ° to 180 ° in the plane orthogonal to the direction, and the value of the average Taylor factor in each direction in the plane the absolute value of the difference between the maximum value and the minimum value you wherein a is 0.30 or less, molding an aluminum alloy plate which is excellent in bending workability. In the aluminum alloy for forming process according to claim 1 ,
Furthermore, the aluminum grain plate for forming which is excellent in bending workability, wherein the ASTM crystal grain size is 4 or more. In the aluminum alloy plate for forming according to claim 1,
Among aluminum alloys, Al-Mg-Si alloy, Al-Mg-Si-Cu alloy, Al-Mg alloy, Al-Zn-Mg alloy, Al-Cu alloy, Al-Mn alloy An aluminum alloy plate for forming having excellent bending workability, wherein one selected type is used. In manufacturing the aluminum alloy plate for forming according to claim 1,
After homogenizing the ingot of the raw material aluminum alloy, it is hot-rolled, and then, as cold rolling by a plurality of passes, two or more passes of cross rolling that is rolled in a direction different from the rolling direction of hot rolling, and The rolling is a combination of a normal rolling pass that rolls in the same direction as the hot rolling direction, and the final pass is rolled as the normal rolling pass, and then subjected to a recrystallization heat treatment, A method for producing an aluminum alloy sheet for forming with excellent bending workability.