JP2006219762A - Al-Mg BASED ALLOY SHEET WITH GOOD PRESS FORMABILITY - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Al-Mg based alloy sheet with good press formability, namely, with excellent deep-drawability. <P>SOLUTION: The Al-Mg based alloy sheet has a texture composed of grains with a ratio of the volume fraction in the S orientation to the volume fraction in the CUBE orientation (S/Cube) being 1 or more, and a GOSS orientation of 10% or less, wherein the grain size is in the range of 20 to 100 μm. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an Al-Mg alloy plate having excellent press formability, and particularly relates to an Al-Mg alloy plate having high deep drawability and suitable for materials such as automobile body panels.

  In recent years, from the viewpoint of consideration for the global environment, social demands for weight reduction of vehicles such as automobiles are increasing. In order to respond to such demands, the application of aluminum materials instead of steel materials such as steel plates is being studied as materials for automobile body panels and the like.

  However, even an aluminum material having a strength comparable to that of a steel plate is generally inferior in press formability such as deep drawing and stretch forming, and therefore, improvement in press formability is strongly desired.

  As an aluminum alloy plate excellent in press formability, aluminum alloy materials such as Al-Mg based JIS 5052 alloy and JIS 5182 alloy have been used conventionally, and other Al-Mg based alloy materials disclosed in Patent Document 1 are used. There is. The applicant of the present invention has been diligently engaged in research and development and commercialization. The KS5030 alloy and the KS5032 alloy (both are trade names of Kobe Steel, the contents of which are Patent Document 2, Patent Document 3, Patent Document 4, Patent (Disclosed in Document 5). These alloys give high strength and high ductility by adding a high concentration of Mg, and by adding about 0.5% of Cu, paint bake hardenability and stress corrosion cracking resistance are improved, and Mn, Cr It is characterized in that the crystal grain size was optimized by adding. These aluminum alloy plates are applied to automobile panels and the like.

  However, it cannot be said that these aluminum alloy plates have sufficient formability, and further improvement of formability has been demanded by automobile manufacturers. The reason why moldability is insufficient is that the plastic anisotropy cannot be controlled well. That is, a JIS alloy such as JIS 5182 alloy, an alloy developed by the present applicant such as KS5030 alloy and KS5032, or Al--disclosed in Patent Document 6, Patent Document 7, Patent Document 8, Patent Document 9, Patent Document 10, and the like. The Mg-based alloy only specifies the alloy components, and no consideration is given to the texture governing plastic anisotropy.

  It has long been known that textures dominate formability. For example, in cold-rolled steel sheets, it is known that deep drawability can be improved by strongly developing (111) as the plane orientation. Recently, it has been proposed to improve formability of aluminum alloys by controlling the texture of plate materials. For example, in Patent Document 11, as an aluminum alloy for deep drawing, the (110) orientation integration degree of the plate surface is 10% or more, and the integration degree ratio of the (110) orientation and the (112) orientation is 1.5 or more. There is disclosed an Al—Mg alloy plate having a crystal grain size in the range of 35 to 80 μm. However, the texture shown here is not optimal for deep drawing, and there is a demand for a texture that is more excellent in deep drawability.

  One of the inventors of the present invention invented an Al—Mg alloy excellent in stretch forming with controlled texture (Patent Document 12). However, the texture defined therein is not necessarily optimum for stretch formability, and stretch forming. It is necessary to clarify the relationship between sex and texture. In the present invention, the crystal grain size that largely controls the formability is not taken into consideration.

Looking at academic papers, Ratchev et al. Predict the relationship between texture and formability in Al-Mg alloy plates based on plastic working theory, and report that anisotropy becomes stronger and formability decreases when the Cube orientation etc. develops strongly. (Non-Patent Document 1).
JP 52-141409 A JP 60-125346 A JP 63-89649 A JP-A-2-269937 JP-A-3-315486 JP 52-141409 A JP 60-125346 A JP 63-89649 A JP-A-2-269937 JP-A-3-315486 JP-A-5-295476 JP-A-8-325663 Texture and Microstructures, vol. 22, 1994, P219.

  The present invention has been made in view of such circumstances, and its purpose is to control the ratio of individual crystal orientations for the texture governing plastic anisotropy, and further optimize the crystal grain size, It is another object of the present invention to provide an optimum Al-Mg alloy plate excellent in press formability by limiting the kind and amount of additive elements to a specific range. More specifically, among the press moldability, (i) stretch moldability, (ii) deep drawability, and (iii) improvement of the three cracking limits in the tensile region to the plane strain region, An object of the present invention is to provide an Al-Mg alloy plate having excellent characteristics.

  Among the Al-Mg alloy plates having excellent press formability according to the present invention, the Al-Mg alloy plate having excellent stretch formability has a volume fraction of 5-20% in CUBE orientation and a volume in GOSS orientation as a texture. The gist is that the fraction is 1 to 5%, the volume fraction of BRASS orientation, S orientation, and COPPER orientation is 1 to 10%, respectively, and the crystal grain size is in the range of 20 to 70 μm. Preferably, the volume fraction of the CUBE azimuth is 5 to 15%, the volume fraction of the GOSS azimuth is 1 to 3%, and the volume fraction of the BRASS azimuth, S azimuth, and COPPER azimuth is 1 to 5% each. Furthermore, the crystal grain size is preferably 30 to 60 μm.

  The Al—Mg-based alloy plate having excellent deep drawability has, as a texture, a ratio of the volume fraction of the CUBE orientation to the volume fraction of the S orientation (S / Cube) of 1 or more and a GOSS orientation of 10%. The gist is that the crystal grain size is in the range of 20 to 100 μm. Preferably, the ratio (S / Cube) of the volume fraction of the CUBE orientation to the volume fraction of the S orientation is 2 or more, and the GOSS orientation is 5% or less. The crystal grain size is preferably 40 to 80 μm.

  An Al—Mg alloy plate having a high forming crack limit from the tensile region to the plane strain region has a volume fraction of CUBE orientation of 30 to 50% and a volume fraction of BRASS orientation of 10 to 20% as a texture. And the crystal grain size is in the range of 50 to 100 μm. Preferably, the volume fraction of the CUBE orientation is 40 to 50% and the volume fraction of the BRASS orientation is 15 to 20%. The particle size is more preferably 60 to 90 μm.

  Furthermore, these Al-Mg alloy plates all contain 2 to 6 wt% Mg, and a total of at least one selected from Fe, Mn, Cr, Zr and Cu is 0.03 wt% or more ( When Cu is selected, it is preferable that the Cu content be 0.2 wt% or more), with the balance being Al.

  In the Al—Mg-based alloy plate, press formability can be improved by appropriately controlling the texture, crystal grain size, and additive elements as described above. Specifically, it is possible to obtain an aluminum alloy plate suitable for an automobile body panel or the like, which is excellent in stretch formability or deep drawability, or has a high forming crack limit from a tensile region to a plane strain region.

  The texture of a normal aluminum alloy plate is mainly composed of a CUBE orientation, a GOSS orientation, a BRASS orientation, an S orientation, and a COPPER orientation. When these volume fractions change, the plastic anisotropy changes. Here, how the texture is formed varies depending on the processing method even in the case of the same crystal system, and in the case of a plate material by rolling, it is necessary to express it by a rolling surface and a rolling direction. The rolling surface is represented by (◯◯◯), and the rolling direction is represented by <ΔΔΔ> (◯ and Δ are integers). Based on such a representation method, the CUBE direction, the GOSS direction, the BRASS direction, the S direction, and the COPPER direction are expressed as follows.

CUBE bearing (100) <001>
GOSS orientation (110) <001>
BRASS orientation (110) <1-12>
S direction (123) <63-4>
COPPER bearing (112) <11-1>

  In this specification, it is defined that deviations in orientation within ± 10 degrees from these orientations belong to the same orientation factor. When expressing the direction, the numerical value in the negative direction is generally displayed with a bar on the numerical value. However, in this specification, for the sake of convenience, a “-” sign is added before the numerical value. Display this. Further, directions other than these direction factors are defined as random directions.

  From the change in plastic anisotropy corresponding to the change in texture, the present inventors have determined the optimum structure for the three properties of stretch-formability, deep-drawn formability, and forming crack limit in the tensile region to the plane strain region. Revealed. Hereinafter, each molding characteristic will be described.

(1) Relationship between stretch formability and texture The excellent stretch formability means that the crack limit under biaxial stress is high. There are three dominating factors for this purpose: low plastic anisotropy, high work hardening ability, and high strain rate sensitivity index. It has been known in the past that a material with a weak texture is excellent in stretch formability, but when producing a sheet by rolling, it is possible to obtain a completely isotropic material (in other words, a texture is weak). Impossible, some orientation becomes stronger.

  As a result of examining the relationship between the volume fraction of each orientation and the overhang property based on many experimental results, the volume fraction of the CUBE orientation is 5% or more and 20% or less, preferably 15% or less. Plasticity when the volume fraction is 1% or more and 5% or less, preferably 3% or less, and the volume fraction of BRASS, S, and COPPER orientations is 1% or more and 10% or less, preferably 5% or less. It turned out that it becomes a structure | tissue with weak anisotropy, ie, a structure | tissue which is most excellent in the overhang property.

  Regarding the quantitative evaluation method of the texture, the orientation of each grain is obtained for 100 crystal grains on the plate surface by the electronic channeling pattern method, and which of the above five orientations is determined. The volume fraction of each direction was calculated on the assumption that all the particles had the same size. Hereinafter, the texture evaluation method in this specification is the same.

(2) Relationship between deep-drawing formability and texture The excellent deep-drawing formability means that it is easy to squeeze the plate at the flange portion and it is difficult to break at the punch side or the punch bottom. For this purpose, plastic deformation is easy when pulled in one direction (a state where compressive stress is applied in a direction perpendicular to the tensile direction), and when pulled from two directions (tensile stress is applied in two directions). It is necessary for the strength to be high).

  As a result of intensive studies on the relationship between texture and LDR (limit drawing ratio), which is an index of deep drawability, the present inventors have found that (i) Cube orientation and Goss orientation reduce LDR, and (ii) S orientation. Clarified that it improves LDR and (iii) the influence of other orientations can be ignored. Of the findings of (i) to (iii), only the view of (ii) has been known so far (a dissertation by one of the inventors), but the relationship between volume fraction of other orientations and deep drawability Is newly found by the present inventors based on experimental results.

  Based on the findings of (i) to (iii), the texture of the Al—Mg alloy has a ratio of the volume fraction of the CUBE orientation to the volume fraction of the S orientation (S / Cube) of 1 or more, preferably 2 or more. When the GOSS orientation is 10% or less, preferably 5% or less, the LDR is increased and the deep drawability is excellent. Note that the deep-drawable forming aluminum alloy described in Patent Document 11 (Japanese Patent Laid-Open No. 5-295476) has an accumulation degree of (110) orientation corresponding to GOSS or BRASS orientation of 10% or more, and (110) The (112) orientation integration ratio corresponding to the azimuth and the COPPER azimuth is 1.5 or more and the S azimuth ratio is not defined, the ratio of the volume fraction of the CUBE azimuth and the volume fraction of the S azimuth ( The point which does not pay attention to (S / Cube) is different from the present invention.

(3) Relationship between forming crack limit and texture from tensile region to plane strain region As a result of the intensive studies by the present inventors, the forming crack limit from tensile region to plane strain region is not affected by plastic anisotropy, and work hardening It was clarified that the characteristics and strain rate sensitivity are dominant, especially the work hardening characteristics are affected by the texture, and the stronger the texture anisotropy, the better the work hardening characteristics.

  The texture having a high forming crack limit from the tensile region to the plane strain region has a volume fraction of CUBE orientation of 30% or more, preferably 40%, 50% or less, and a volume fraction of BRASS orientation of 10% or more. Preferably, it is 15% or more and 20% or less.

(4) Relationship between press moldability and crystal grain size (a) Stretch moldability The smaller the crystal grain size, the more uniformly the deformation occurs, the higher the strain rate sensitivity index, and the better the stretch moldability.

  As a result of intensive studies, the present inventors have found that it is optimal that the crystal grain size is in the range of 20 μm or more, preferably 30 μm or more, 70 μm or less, preferably 60 μm or less. If it is less than 20 μm, a stretcher strain mark is generated at the time of molding, which is not preferable, and if it exceeds 70 μm, grain boundary breakage tends to occur, which is not preferable.

  In the measurement of the crystal grain size, the average slice length was determined by the cross-cut method based on an optical micrograph having a magnification of 100, and this was used as the average crystal grain size. The same applies hereinafter.

(B) Deep-drawing formability If the crystal grain size is in the range of 20 μm or more, preferably 40 μm or more and 100 μm or less, preferably 60 μm or less, the deep-drawing formability is good. If it is less than 20 μm, a stretcher strain mark is generated at the bottom of the squeezed product and the appearance of the product is impaired. If it exceeds 100 μm, an orange peel (rough skin) is generated on the surface of the product and the appearance of the product is impaired. It is.

(C) Forming crack limit from tensile region to plane strain region The forming crack limit from tensile region to plane strain region is not affected by plastic anisotropy, and work hardening characteristics and strain rate sensitivity are dominant, especially work hardening. Characteristics are known to be affected by texture. And it turned out that work hardening characteristic improves, so that a crystal grain size is large. However, if the crystal grain size becomes too large, an orange peel (skin) occurs during molding and the appearance of the product is significantly impaired.

  Accordingly, when the crystal grain size is in the range of 50 μm or more, preferably 60 μm or more, 100 μm or less, preferably 90 μm or less, the forming crack limit from the tensile region to the plane strain region becomes high.

(5) Chemical Composition The chemical composition of the aluminum alloy of the present invention contains 2 wt% ≦ 2 wt% ≦ Mg ≦ 6 wt% of Mg for the following reasons, and includes Fe, Mn, Cr, Zr, and Cu. At least one selected from the group consisting of 0.03 wt% or more (when Cu is selected, Cu is 0.2 wt% or more), and the upper limit of the content of each element is Fe ≦ 0.2 wt%, Mn ≦ It is preferable that 0.6 wt%, Cr ≦ 0.3 wt%, Zr ≦ 0.3 wt%, and Cu ≦ 1.0%. These additive elements have a great influence on the texture formation and change the plastic anisotropy. Therefore, the texture can be optimized by optimizing the amount of added elements and the corresponding process conditions.

・ 2wt% ≦ Mg ≦ 6wt%
Mg is an important element that improves work hardening ability and uniformly plastically deforms the material and improves the fracture crack limit. If the Mg content is less than 2 wt%, the Mg content is not sufficiently cured, and if it exceeds 6 wt%, production becomes difficult, and moreover, grain boundary breakage is likely to occur during molding. It is desirable to be.

-One or more selected from Fe, Mn, Cr, Zr, and Cu in a total of 0.03 wt% or more (when Cu is selected, 0.2 wt% or more as Cu), and the inclusion of individual elements The upper limit of the rate is Fe ≦ 0.2 wt%, Mn ≦ 0.6 wt%, Cr ≦ 0.3 wt%, Zr ≦ 0.3 wt%, Cu ≦ 1.0 wt%
The addition of Fe, Mn, Cr, and Zr is effective for refining crystal grains and plays an important role in texture control. Grain boundary fracture is likely to occur when the crystal grain size is large, and the smaller the crystal grain size, the better. Therefore, it is preferable to add Fe, Mn, Cr, and Zr, which are effective elements for crystal grain refinement. These elements also improve the strain rate sensitivity index and improve the molding limit. A positive value of the strain rate sensitivity index means that the strain until the start of constriction during molding increases. However, if the total content of Fe, Mn, Cr, and Zr is less than 0.03 wt%, there is no effect of addition, while the upper limit ratio of each element (that is, the Fe content is 0.2 wt% and the Mn content is If the content exceeds 0.6 wt%, Cr content is 0.3 wt%, and Zr content is 0.3 wt%, a coarse compound is formed, and the formability is deteriorated because it becomes a starting point of fracture. .

  Cu is an element that improves work hardening ability, improves paint bake hardening characteristics, further improves stress corrosion cracking resistance, and has the effect of changing the texture. However, if it is less than 0.2 wt%, there is no effect of addition, and if it exceeds 1.0 wt%, a coarse compound is formed and becomes the starting point of fracture, so that the moldability deteriorates.

(6) Texture and production conditions The aluminum alloy plate material of the present invention is produced through normal casting, homogenization heat treatment, hot rolling, cold rolling, and final annealing processes. The resulting texture varies depending on the setting conditions.

  First, when a transition metal such as Mn, Cr, Fe, or Zr is contained, it is important to control the precipitate to a desired form. This is because these precipitates act as preferential nucleation sites for recrystallization orientation and dominate the texture formed. Moreover, these precipitates also control the crystal grain size and greatly influence the limit of forming cracks. Accordingly, the optimum conditions in the homogenization heat treatment process cannot be uniquely determined because they change as the type and amount of transition metals such as Mn, Cr, Fe, and Zr change.

  The optimum conditions for the hot rolling process and the cold rolling process performed after the homogenization heat treatment process vary depending on the form of precipitates formed by the homogenization heat treatment. There are combinations of hot rolling, cold rolling, cold rolling under high pressure, cold rolling under low pressure, etc., but this combination is not uniquely determined. Further, after the hot rolling, after the roughing, the cold rolling may be performed, the intermediate annealing may be performed in the middle of the cold rolling, and when the roughening is performed after the hot rolling. The optimum rolling conditions differ depending on whether intermediate annealing is performed during cold rolling or not.

  A final heat treatment (solution treatment) is performed after cold rolling. The texture also changes depending on the solution treatment conditions.

  That is, in order to obtain the preferred texture shown in the claims, it is necessary to adjust the rolling conditions, rough conditions, solution treatment conditions, and the like each time the alloy components and the homogenization heat treatment conditions change. That is, even with the same alloy composition. This is because by optimally controlling the homogenization heat treatment conditions, rolling conditions, roughening conditions, solution treatment conditions, etc., an optimal texture can be formed, and the press formability can be greatly improved. . Therefore, although these manufacturing conditions may overlap with the conventional manufacturing conditions individually, as a series of manufacturing processes, a texture suitable for the formability required by performing a special combination is obtained. Can do.

  However, as a tendency, when the final cold rolling rate is low, it is easy to obtain a texture with excellent deep drawability, and when the final cold rolling rate is around 50%, a texture with excellent stretch forming property is obtained. In addition, when the final cold rolling rate is high, it can be said that the forming crack limit from the tensile region to the plane strain region tends to increase. Here, the final cold rolling rate refers to the rolling rate performed after annealing when annealing is performed in the middle of cold rolling, and the cold rolling rate is the final cold rolling rate when annealing is not performed in the middle. It becomes.

  Hereinafter, the present invention will be described based on specific examples.

  In the following examples, the crystal grain size of the obtained structure was measured by a line cutting method on a plane perpendicular to the rolling surface and perpendicular to the rolling direction. For the measurement of the crystal grain size, an average section length was obtained by a cross-cut method for a photomicrograph having a magnification of 100 times, and this was used as the average crystal grain size.

  As for the texture, the orientation of each crystal grain was determined for 100 crystal grains by the electronic channeling pattern method, which one of the above five orientations was determined, and the volume fraction of each orientation was calculated (1 It was assumed that the size of one grain was the same.)

Example 1
The Al-5% Mg-0.1% Fe alloy was ingoted by ordinary DC casting (semi-continuous casting) to obtain an ingot having a width of 400 mm, a thickness of 150 mm, and a length of 3000 mm. A two-stage homogenization heat treatment was performed, which was held at 480 ° C. for 48 hours and then held at 440 ° C. for 4 hours, and was hot rolled to form a 5 mm thick plate. The start temperature of hot rolling was 440 ° C., which is the temperature of the homogenization heat treatment performed immediately before, and the end temperature of hot rolling was 320 ° C. After hot rolling, a 1 mm-thick plate material was obtained by cold rolling, but the final cold rolling rate was adjusted in the range of 17% to 80% by appropriately performing intermediate annealing during the cold rolling. When intermediate annealing is not performed, cold rolling is performed at a time from 5 mm to 1 mm, and the final cold rolling rate is 80%.

A plate material having a thickness of 1 mm obtained by cold rolling was subjected to a solution treatment performed at the temperature and holding time shown in Table 1, and No. 1 having a crystal grain size and a texture as shown in Table 1. 1 to 15 plate materials were obtained. Here, the heating to the solution treatment temperature was performed by two types of rapid heating (60000 ° C./h) and gradual heating (300 ° C./h).

  No. obtained The following bulge overhang tests were performed on 1 to 15 plate materials. That is, the periphery of a 100 mm diameter plate material test piece is fixed to a 50 mm diameter mold, and the test piece is lowered by applying hydrostatic pressure to one surface of the test piece. Asked. The amount of strain was measured by pressing a 3 mm square grid-like stamp on the surface of the plate specimen and measuring the change in dimensions. The results are shown in Table 1 together with the production method (final cold rolling rate, solution treatment temperature and holding time, heating rate), crystal grain size and texture.

  From Table 1, all the examples exceeded the strain amount of 0.40 mm, but the comparative example produced an ss mark even when it was less than 0.38 mm or exceeding 0.38 mm (No. 14). It can be seen that the film has better stretch formability than the comparative example.

Example 2: A preferred embodiment of the invention according to claim 1 An Al-5% Mg-0.1% Fe alloy was agglomerated by ordinary DC casting (semi-continuous casting), width 400 mm, thickness 150 mm, length A 3000 mm ingot was obtained. A two-step soaking process was performed, which was held at 520 ° C. for 48 hours and then held at 460 ° C. for 4 hours, and was hot rolled to form a 5 mm thick plate. The hot rolling start temperature was 460 ° C. and the end temperature was 330 ° C. After hot rolling, a 1 mm-thick plate material was obtained by cold rolling, but the final cold rolling rate was adjusted in the range of 17% to 80% by appropriately performing intermediate annealing during the cold rolling. When intermediate annealing is not performed, cold rolling is performed at a time from 5 mm to 1 mm, and the final cold rolling rate is 80%.

  A plate material having a thickness of 1 mm obtained by cold rolling was subjected to solution treatment for holding at a temperature and holding time shown in Table 2, and No. 1 having a crystal grain size and a texture as shown in Table 2. 21 to 28 plate materials were obtained. Here, the heating to the solution treatment temperature was performed by two types of rapid heating (60000 ° C./h) and gradual heating (300 ° C./h).

  The obtained plate material test piece No. For 21-28, the limiting drawing ratio (LDR) was measured. The limit drawing ratio (LDR) is measured by preparing disk specimens of various diameters, deep drawing with punches of the following dimensions, and limiting the ratio of the specimen diameter to the punch diameter when deep drawing is not possible. The aperture ratio was used. It shows that the deeper the drawability, the better the limit drawing ratio. The oil used in the measurement test was a solid lubricant KS-3 (Kobe Steel Development).

Measurement conditions for LDR test Mold material SKD11
Punch diameter 50mm (flat head)
Die holder 52.8mm in diameter
Die shoulder R6.0mm
BHF 0.5t
Punch speed 850mm / min

  Table 2 shows the limit drawing ratio (LDR), final cold rolling rate, heating rate, solution treatment temperature and holding time, crystal grain size, and texture (volume fraction of CUBE orientation and volume fraction of S orientation). (S / Cube) and volume fraction of GOSS orientation).

  From Table 2, it can be seen that the plate material of the present invention has a higher LDR than the comparative example and is excellent in deep drawability.

Example 3
The Al-5% Mg-0.1% Fe alloy was ingoted by ordinary DC casting (semi-continuous casting) to obtain an ingot having a width of 400 mm, a thickness of 150 mm, and a length of 3000 mm. A soaking treatment was performed at 480 ° C. for 48 hours, and a hot-rolled plate was formed to a thickness of 5 mm. The hot rolling start temperature was 480 ° C. and the end temperature was 340 ° C. After hot rolling, a 1 mm-thick plate material was obtained by cold rolling, but the final cold rolling rate was adjusted in the range of 17% to 80% by appropriately performing intermediate annealing during the cold rolling. When intermediate annealing is not performed, cold rolling is performed at a time from 5 mm to 1 mm, and the final cold rolling rate is 80%.

  A plate material having a thickness of 1 mm obtained by cold rolling was subjected to a solution treatment for holding at a temperature and holding time shown in Table 3, and No. 1 having a crystal grain size and a texture as shown in Table 3. 31 to 37 plate materials were obtained. Here, the heating to the solution treatment temperature was performed by two types of rapid heating (60000 ° C./h) and gradual heating (300 ° C./h).

  No. A test piece having the shape shown in FIGS. 1 and 2 is cut out from the plate materials 31 to 37, a biaxial tensile test is performed using the test piece shown in FIG. 1, and a uniaxial tension is used using the test piece shown in FIG. A test was conducted. In all cases, the amount of strain when the test piece broke was measured, and the strain ratio relative to the start of the test was determined. In the test using the test piece shown in FIG. 1, the amount of strain at the breaking limit in the plane strain region is found, and in the test using the test piece shown in FIG. 2, the amount of strain at the breaking limit in the uniaxial tensile region is found. . In any case, the larger the value, the higher the breaking limit.

  The measurement results are shown in Table 3 together with the production method (final cold rolling rate, solution treatment temperature and holding time, heating rate), crystal grain size and texture.

  As is clear from Table 3, it can be seen that the plate strain of the present invention is higher than the comparative example in both plane strain and uniaxial tension, and the forming crack limit in the plane strain region is higher from the tensile region.

Example 4
The alloys having the compositions shown in Table 4 and Table 5 were ingoted by ordinary DC casting (semi-continuous casting) to obtain an ingot having a width of 400 mm, a thickness of 150 mm, and a length of 3000 mm. The homogenized heat treatment shown in Table 4 and Table 5 was performed, and a 5 mm thick plate was obtained by hot rolling. The starting temperature of hot rolling was the homogenizing heat treatment temperature (the temperature of the second stage in the case of two-stage soaking), and the end temperature of hot rolling was about 150 ° C. lower than the starting temperature. After that, it was made into a plate material having a thickness of 5 mm to 1 mm by cold rolling. Under the present circumstances, the final cold rolling reduction was adjusted to 50% and 17% by performing intermediate annealing in the middle. Thereafter, solution treatment was performed at 530 ° C., and No. 1 having crystal grain sizes and textures as shown in Tables 4 and 5 were obtained. 41 to 73 plate materials were obtained. Here, the heating to the solution treatment temperature was performed by rapid heating (60000 ° C./h).

  No. obtained About the board | plate materials of 41-73, it carried out similarly to Example 1, and performed the bulge extension test. The measurement results are shown in Tables 4 and 5 together with the production method (final cold rolling rate, solution treatment temperature and holding time, heating rate), crystal grain size and texture. Table 4 is an example and Table 5 is a comparative example.

  In addition, the display of A: B in the homogenization heat treatment conditions in the table indicates that the material was held at A ° C. for B time, and further, it was processed in two stages from “upper” to “lower”. The same applies hereinafter.

  Table 5 (corresponding to the comparative example) has a basil test crack strain value of 0.37 or less, whereas Table 4 (corresponding to the example) has a basil test crack strain value of 0. Excellent at 38 or more.

Example 5: Preferred embodiment of the invention according to claim 2 The alloys shown in Tables 6 and 7 are ingot formed by ordinary DC casting (semi-continuous casting), and are 400 mm wide, 150 mm thick and 3000 mm long. Got. The homogenized heat treatment shown in Table 6 and Table 7 was performed, and the plate was 5 mm thick by hot rolling. The starting temperature of hot rolling was the homogenizing heat treatment temperature (the temperature of the second stage in the case of two-stage soaking), and the end temperature of hot rolling was about 150 ° C. lower than that. After that, it was made into a plate material having a thickness of 5 mm to 1 mm by cold rolling. At this time, the final cold rolling rate was set to 17%, 50%, and 80% by intermediate annealing or not. When intermediate annealing is not performed, the final cold rolling reduction is 80%.

Thereafter, solution treatment by holding at 400 ° C. or 530 ° C. was carried out, and No. having crystal grain sizes and textures as shown in Tables 4 and 5 81 to 113 plate materials were obtained. Here, the heating to the solution treatment temperature was performed by two types of rapid heating (60000 ° C./h) or slow heating (300 ° C./h).

  No. obtained For the plate materials 81 to 113, the limit drawing ratio (LDR) measurement test was performed in the same manner as in Example 2. The measurement results are shown in Tables 6 and 7 together with the composition, production method (final cold rolling rate, homogenization heat treatment condition, solution treatment condition), crystal grain size and texture. Table 6 corresponds to an example, and Table 7 corresponds to a comparative example.

  In the case corresponding to the embodiment of the present invention (Table 6), the LDR was as high as 2.08 or more, whereas in the comparative example (Table 7), the LDR was as low as 2.01 or less, or 2.02 or more. Even if LDR was obtained, an orange peel was generated, a stretcher strain mark (ss mark) was generated, and the product was defective.

Example 6
The alloys shown in Table 8 and Table 9 were ingoted by ordinary DC casting (semi-continuous casting) to obtain an ingot having a width of 400 mm, a thickness of 150 mm, and a length of 3000 mm. The homogenized heat treatment shown in Table 8 and Table 9 was performed, and a 5 mm thick plate was obtained by hot rolling. The starting temperature of hot rolling was the homogenizing heat treatment temperature (the temperature of the second stage of the two-stage soaking), and the end temperature of hot rolling was about 150 ° C. lower than that. After that, it was made into a plate material having a thickness of 5 mm to 1 mm by cold rolling. At this time, the final cold rolling reduction was adjusted to 17%, 50%, and 80% (when intermediate annealing was not performed) by performing intermediate annealing in the middle or not performing intermediate annealing. Thereafter, solution treatment was performed at 530 ° C., and No. 1 having crystal grain sizes and textures as shown in Tables 8 and 9 were obtained. 121-153 plate materials were obtained. Here, the heating to the solution treatment temperature was performed by two types of rapid heating (60000 ° C./h) or slow heating (300 ° C./h).

  No. obtained About the board | plate material of 121-153, it carried out similarly to Example 3, and the tension test using a special-shaped test piece was done. The results are shown in Tables 8 and 9 together with the composition, production method (final rolling rate, homogenization heat treatment condition, heating rate), particle size and structure. Table 8 shows a case corresponding to an embodiment of the present invention, and Table 9 shows a case corresponding to a comparative example of the present invention.

  In the examples (Table 8), the fracture limit during uniaxial tension was 0.35 or more, and the fracture limit of plane strain was 0.30 or more. On the other hand, in the comparative example (Table 9), the rupture limit during uniaxial tension is less than 0.35, the rupture limit of plane strain is less than 0.30, and some orange peels are observed. It was.

  In the Al—Mg alloy plate of the present invention, the texture, crystal grain size, and additive elements are appropriately controlled so as to be excellent in press formability, specifically deep drawability. Therefore, the Al—Mg alloy plate of the present invention is suitable as an aluminum alloy plate used for automobile body panels and the like.

It is a top view which shows the shape of the test piece (wide width tensile test piece) used for the tensile test in a plane strain area | region. It is a top view which shows the shape of the test piece used for the tension test in a uniaxial tension area | region.

Claims (2)

  An Al-Mg alloy plate having a texture with a ratio of the volume fraction of the CUBE orientation to the volume fraction of the S orientation (S / Cube) of 1 or more and a GOSS orientation of 10% or less. An Al-Mg alloy plate excellent in press formability characterized by having a diameter in a range of 20 to 100 µm.   2. The Al—Mg alloy plate according to claim 1, comprising 2 wt% ≦ Mg ≦ 6 wt% of Mg, and summing at least one selected from Fe, Mn, Cr, Zr, and Cu. 0.03 wt% or more (when Cu is selected, 0.2 wt% or more as Cu), and the upper limit of the content of each element is Fe ≦ 0.2 wt%, Mn ≦ 0.6 wt%, Cr ≦ An Al—Mg-based alloy plate excellent in press formability with 0.3 wt%, Zr ≦ 0.3 wt%, and Cu ≦ 1.0%.

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