JP2008202134A - Aluminum alloy hot rolled sheet having excellent press formability - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-heat refined Al-Mg based aluminum alloy hot rolled sheet capable of press forming as hot-rolled in a state where annealing is not performed after hot rolling. <P>SOLUTION: The structure of an aluminum alloy hot rolled sheet composed of an Al-Mg based aluminum alloy having a specific component composition and being as hot-rolled where annealing is not performed after hot rolling is made into a recrystallized grain structure where the average crystal grain diameter is ≤25 μm, and further, the average volume fraction in the Cube orientation is ≤10%, so as to improve its press formability. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an aluminum alloy hot-rolled sheet suitable for automobile panels and excellent in press formability. The aluminum alloy hot-rolled sheet referred to in the present invention is a hot-rolled sheet or a hot-rolled sheet, and is in a state of being hot-rolled and not annealed after hot rolling (non-tempered). An aluminum alloy plate. Hereinafter, aluminum is also referred to as Al.

  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 meet such demands, the application of aluminum materials in place of steel materials such as steel plates is being studied as materials for automobile panels, particularly large body panels (outer panels, inner panels) such as hoods, doors, and roofs.

  As an aluminum alloy plate excellent in press formability, 5000 series aluminum alloy materials such as Al-Mg series JIS5052 alloy and JIS5182 alloy have been used conventionally. 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.

  On the other hand, it has been proposed to improve the formability of the 5000 series aluminum alloy by examining the component system and optimizing the production conditions. Recently, it has been proposed to improve formability by controlling the texture of a 5000 series aluminum alloy cold-rolled sheet.

  For example, in Patent Document 1, 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 between the (110) orientation and the (112) orientation is 1.5 or more. An Al—Mg alloy plate having a crystal grain size in the range of 35 to 80 μm is disclosed.

  On the other hand, Patent Documents 2 to 4 and the like have also been proposed in order to make the texture of the 5000 series aluminum alloy cold-rolled sheet a texture that is more excellent in deep drawability. These are characterized by having a texture in which the CUBE orientation, S orientation, GOSS orientation, BRASS orientation, etc. are controlled at a certain ratio, and the crystal grain size is also controlled within a certain range such as 20-100 μm.

  Certainly, press formability such as deep drawing and stretch forming is improved by controlling the texture of the 5000 series aluminum alloy cold rolled sheet.

  However, these 5000 series aluminum alloy cold-rolled sheets are usually manufactured by further cold-rolling and thinning hot-rolled sheets obtained by hot rolling a melt-cast slab after homogenization heat treatment.

  However, 5000 series aluminum alloys have a work hardening property. For this reason, in order to improve the press formability of a 5000 series aluminum alloy cold rolled sheet work-hardened by cold rolling, finish annealing (annealing) after cold rolling is performed in order to obtain the softest material strength. Was indispensable. This is the same in any of the above-described conventional techniques even when the metallurgical control of the texture and composition is performed to improve the press formability, and finish annealing (annealing) after cold rolling is essential. Met.

  Further, in order to improve the press formability, when trying to refine the crystal grain size (preventing coarsening) of the 5000 series aluminum alloy cold rolled sheet as described above, the cold rolling rate (working rate) is 75% or more. It needs to be high. For this reason, in order to earn a cold rolling rate, it is necessary to increase the thickness of the hot-rolled sheet, which is a material of the cold rolling rate, and to increase the number of cold rolling passes (the number of rolling). Accordingly, when the crystal grain size of the 5000 series aluminum alloy cold-rolled sheet as described above is refined (preventing coarsening), productivity is lowered. Further, when the cold rolling rate (working rate) is increased, the work hardening described above is also increased, and the finish annealing (annealing) by the continuous annealing furnace or the batch annealing furnace after the cold rolling becomes more indispensable. .

  For this reason, the manufacturing cost of a 5000 series aluminum alloy cold-rolled sheet with improved press formability inevitably increases. In addition, the production efficiency is inevitably lowered.

  On the other hand, if a 5000 series aluminum alloy plate for press forming can be supplied in the state of a hot-rolled plate (hot-rolled plate) instead of the cold-rolled plate as a material plate for an automobile panel, the manufacturing cost will be increased. And manufacturing efficiency can be greatly improved.

In this regard, conventionally, as a 5000 series aluminum alloy plate, in Patent Document 5, as an aluminum alloy hot rolled plate for a press structure part having a bent portion, 0.2% proof stress is 110 to 135 MPa, and tensile strength is 220 to 220. It has been proposed to be in the range of 250 MPa. Moreover, in patent document 6, it is proposed to use the crystal grain extended in the rolling direction with 0.2% yield strength as an aluminum alloy plate for structural members having a plate thickness of 2.5 mm or more.
JP-A-5-295476 JP 2000-80431 A JP 2006-219762 A JP 2006-219663 A JP 2002-20830 A JP 2003-34852 A

  However, in patent document 5, in order to improve the bendability as a press structure part, the recrystallization annealing (final annealing) of 5000 series aluminum alloy hot-rolled sheet is performed after hot rolling like cold rolling, The material is softened within the range of 0.2% proof stress and tensile strength.

  This is the same in Patent Document 6, and the hot-rolled sheet is softened by performing O refining treatment (350 ° C. × 2 hour annealing treatment). Thus, even for hot-rolled sheets, it has been common knowledge for those skilled in the art to resoften and soften after hot rolling in order to improve press formability. However, as with cold-rolled sheets, when recrystallization annealing is performed on these hot-rolled sheets, the cost reduction and efficiency improvement are achieved even though the process of cold-rolling and annealing is omitted as a hot-rolled sheet. The effect of is greatly impaired.

  In view of such problems, the object of the present invention is to improve press formability, a non-tempered 5000 series aluminum alloy hot-rolled sheet that is in a state of being hot-rolled and not annealed after hot rolling, In other words, it is to provide a non-tempered 5000 series aluminum alloy hot-rolled sheet that can be press-formed without being annealed after hot rolling.

  In order to achieve this object, the gist of the aluminum alloy hot-rolled sheet excellent in press formability of the present invention includes Mg: 2.0 to 6.0% by mass, and further includes Fe, Mn, Cr, Zr and Cu. Aluminum containing 0.03 to 2.5% by mass in total of one or more selected from the group consisting of Al and unavoidable impurities, and being in an as-rolled state that has not been annealed after hot rolling The alloy hot-rolled plate has an average crystal grain size of 25 μm or less and a recrystallized grain structure having an average volume fraction of Cube orientation of 10% or less.

  Here, the aluminum alloy hot-rolled plate is a heat obtained by homogenizing and heat-treating the melt-cast slab at 450 to 550 ° C., setting the rolling rate in the final roll to 30% or more and setting the winding temperature to 300 ° C. or more. It is preferable that the material is hot rolled. Moreover, it is preferable that the plate | board thickness of the said aluminum alloy hot-rolled sheet is 1.6-2.5 mm. Furthermore, it is preferable that the use of the aluminum alloy hot-rolled sheet is for an automobile panel.

  In the present invention, a hot rolled sheet of a 5000 series aluminum alloy having a specific composition is not subjected to a tempering treatment including recrystallization annealing after hot rolling, and is a (non-tempered) aluminum alloy in a state of being hot-rolled. As a hot rolled sheet structure, press formability is improved.

  Therefore, in the present invention, the structure of the hot-rolled aluminum alloy hot rolled sheet is recrystallized with an average crystal grain size of 25 μm or less and an average volume fraction of Cube orientation of 10% or less. Grain structure.

  In an aluminum alloy hot-rolled sheet that has not been subjected to a tempering treatment including recrystallization annealing after hot rolling as in the present invention, the hot-rolled sheet softened by recrystallization annealing. The behavior with respect to the formability is completely different from the plate. Moreover, the behavior with respect to the formability is completely different from the cold-rolled sheet that has been developed by texture recrystallization as described in Patent Documents 2 to 4 and softened by recrystallization annealing.

  In this regard, in the present invention, the recrystallized grain structure in which the recrystallization annealing is not performed and the as-rolled aluminum alloy hot rolled sheet has no anisotropy and the texture does not develop is more constricted. It has been made by knowing that press formability such as property, burring workability, and stretchability is improved.

  In the present invention, a 5000 series aluminum alloy plate for press forming is not in the state of the cold-rolled plate as a material plate for an automobile panel, and is not subjected to a tempering treatment including recrystallization annealing after hot rolling. It is possible to supply in a state where heat is still rising. As a result, the manufacturing cost and manufacturing efficiency of the automobile panel material plate can be greatly improved.

  Hereinafter, embodiments of the present invention will be specifically described for each requirement.

(Chemical composition)
The chemical component composition of the aluminum alloy hot-rolled sheet of the present invention is basically an aluminum alloy corresponding to JIS 5000, which is an Al—Mg alloy. In addition,% display of content of each element means the mass% altogether.

  The hot-rolled sheet of the present invention needs to satisfy various properties such as press formability, strength, weldability, and corrosion resistance as a non-heat treated automotive panel material sheet. Therefore, the hot-rolled sheet of the present invention contains Mg: 2.0 to 6.0% by mass among the 5000 series aluminum alloys, and further, one or two kinds selected from Fe, Mn, Cr, Zr and Cu. A total of 0.03 to 2.5% by mass of the above, with the balance being a chemical composition composed of Al and inevitable impurities.

(impurities)
Elements other than these described elements are basically impurities. However, from the viewpoint of recycling Al alloy plates, not only high-purity Al bullion but also 5000 series alloys, other Al alloy scrap materials, and low-purity Al bullion are used as melting materials. These elements are mixed. Then, reducing these elements to, for example, below the detection limit itself increases the cost, and it is necessary to allow a certain amount of inclusion. Therefore, in this invention, inclusion of elements other than the description element in the range which does not inhibit the objective and effect of this invention is permitted. For example, Si: 0.5% or less, V: 0.3% or less, Ti: 0.5% or less, B: 0.05% or less, and Zn: 0.5% or less are allowed. In addition, other elements are allowed to be contained as the above-mentioned inevitable impurities as long as they do not impair the warm formability and necessary characteristics of the Al-Mg alloy plate of the present invention.

Mg: 2.0-6.0 mass%
Mg enhances work hardening ability and secures necessary strength and durability as a material plate for automobile panels of hot-rolled sheets. In addition, the material is uniformly plastically deformed to improve the fracture crack limit and improve the formability. If the content of Mg is less than 2.0%, these effects of containing Mg are insufficient. On the other hand, if the Mg content exceeds 6.0%, it becomes difficult to produce a plate, and intergranular fracture is likely to occur during press molding, which significantly reduces press moldability. Therefore, the Mg content is in the range of 2.0 to 6.0 mass%.

0.03 to 2.5% by mass in total of one or more selected from Fe, Mn, Cr, Zr and Cu
Fe, Mn, Cr, Zr, and Cu are effective for refining crystal grains when contained in small amounts. Intergranular fracture during press forming tends to occur when the crystal grain size is large, such as when the average crystal grain size of the hot-rolled sheet exceeds 25 μm, and the smaller the crystal grain size of the hot-rolled sheet, the better. In addition, these elements improve the formability limit when contained in a small amount. Furthermore, as the crystal grain size of the hot-rolled sheet is smaller, the surface roughness of the molded product is suppressed.

  If the total content of Fe, Mn, Cr, Zr and Cu is less than 0.03%, there is no content effect. On the other hand, if the total content of these elements exceeds 2.5%, The coarse crystallized substance and precipitate resulting from an element increase, and these are easy to become a starting point of destruction, and on the contrary, press formability falls. Therefore, the content of one or more selected from Fe, Mn, Cr, Zr and Cu is in the range of 0.03 to 2.5% by mass in total.

  The total of the respective contents of each element does not exceed the upper limit, and the upper limit of each element is as follows: the Fe content is 0.4%, the Mn content is 0.6%, and the Cr content is 0.3. %, Zr content is 0.2%, and Cu content is 1.0%.

(Hot rolled sheet structure)
On the premise of the above chemical composition, in the present invention, the structure of an unheated aluminum alloy hot-rolled sheet in the state of being hot-rolled has an average volume fraction of Cube orientation with an average crystal grain size of 25 μm or less. A recrystallized grain structure having a rate of 10% or less is used.

(Average crystal grain size)
The smaller the average crystal grain size of the non-heat treated hot rolled sheet, the better the press formability. When the average grain size of the hot-rolled sheet exceeds 25 μm, even if the structure of the hot-rolled aluminum alloy sheet is a recrystallized grain structure, the drawability, burring workability, and overhang The press formability such as the property is lowered. Also, molding defects such as orange peel (rough skin) are likely to occur on the surface of the molded product, and the appearance is impaired. Therefore, in order to improve the press formability such as drawability, burring workability, and stretchability, in the present invention, in the present invention, the average crystal grain size of the recrystallized grain structure of the aluminum alloy hot-rolled sheet in the state of hot-rolling Is 25 μm or less.

  The crystal grain size referred to here is the maximum diameter of crystal grains in the rolling direction in a longitudinal section in the rolling direction. The average crystal grain size is determined by measuring the maximum diameter of each crystal grain observed in a predetermined measurement region using SEM-EBSP described later and its measurement conditions, and calculating the average value of the obtained results. Ask.

(Cube orientation)
In the present invention, the recrystallized grain structure of the aluminum alloy hot-rolled sheet in the state of being hot-rolled is refined to the average crystal grain size, and the structure without anisotropy and texture is not developed. . In the present invention, the average volume fraction of the Cube orientation (average integration rate of the Cube orientation) is defined as the index, and the average volume fraction of the Cube orientation (hereinafter also referred to as CUBE orientation) is regulated to 10% or less.

  As described in Patent Documents 2 to 4, the textures such as the Cube orientation, Goss orientation, Brass orientation, S orientation, and Copper orientation are certainly different in behavior for formability, and these are controlled to a certain ratio. With such a texture, even with a 5000 series aluminum alloy cold-rolled sheet, press formability such as deep drawing and stretch forming is improved. However, the improvement of formability by these textures is premised on softening by recrystallization annealing (final annealing) as described above.

  On the other hand, in the case of an unheated aluminum alloy hot-rolled sheet in the state of hot-rolling that has not been subjected to tempering treatment including recrystallization annealing after hot rolling, the recrystallization annealing is performed. The behavior of the hot-rolled sheet softened by performing the process on formability is completely different. Moreover, the behavior with respect to the formability is completely different from the cold-rolled sheet that has been developed by texture recrystallization as described in Patent Documents 2 to 4 and softened by recrystallization annealing.

  That is, in the non-tempered hot-rolled sheet of the present invention, the recrystallized grain structure having no anisotropy and no texture development is more suitable for pressability, burring workability, stretchability, etc. Formability is improved.

  When a texture is developed in a normal aluminum alloy plate, it is mainly composed of a Cube orientation, a Goss orientation, a Brass orientation, an S orientation, and a Copper orientation. In contrast, the hot-rolled sheet of the present invention has a recrystallized grain structure that has no anisotropy and does not develop a texture as described above.

  Whether or not it is such a hot-rolled sheet structure of the present invention is specified and quantified by the fact that, among the above crystal orientations, in particular, the average volume fraction of the Cube orientation (the average integration rate of the Cube orientation) is small. Can be Of the above crystal orientations, the Cube orientation in particular reduces press formability such as drawability, burring workability, and stretchability. Therefore, by regulating the Cube orientation, the textures in the other orientations are also regulated, resulting in a recrystallized grain structure in which the texture does not develop, and press formability is improved.

  As described above, in the present invention, the average volume fraction of the Cube orientation (average integration rate of the Cube orientation) is regulated to 10% or less as an index that does not have anisotropy and does not develop a texture. When the average volume fraction of the Cube orientation exceeds 10%, the Cube orientation itself or the texture of the other orientations develops, so that presses such as drawability, burring workability, and stretchability Formability is significantly reduced.

(Measurement of average volume fraction of Cube orientation)
The measurement of the average volume fraction of the Cube orientation, which is the crystal orientation component of the crystal grain, is performed by measuring the plane orientation in the recrystallized grain structure of the hot rolled aluminum alloy sheet in the hot-rolled state as SEM (scanning electron microscope) − It is measured and analyzed by EBSD (Electron Diffraction) “Electron Back Scattering Pattern” and EBSD “Electron Back Scattering Diffraction”. These crystal analyzes use a crystal analysis method based on an electronic channeling pattern method (ECP method).

  Here, for example, the orientation of each crystal grain is determined for 100 crystal grains in the recrystallized grain structure of the hot-rolled sheet. Then, it is determined which of the five orientations belongs (whether it belongs to the Cube orientation), and the average volume fraction of the Cube orientation is calculated. At that time, it is assumed that the size of each crystal grain is the same, and the deviation of the orientation within ± 10 degrees from these orientations is measured as belonging to the same orientation factor.

  The hot-rolled sheet is measured at a right-angle cross section in the sheet thickness direction, measured at the surface of an arbitrary position on the sheet and at a depth part in the sheet thickness direction 1/4, and the measurement results are averaged. At this time, mechanically polish the sample surface of the cross-section of the plate sampled multiple times from each of the above parts, scrape about 0.25 mm from the sample surface by mechanical polishing, and prepare a sample whose surface has been adjusted by buffing and electrolytic polishing. To do. The measurement site is the sample polishing surface, the measurement area of the sample is 1000 μm × 1000 μm, and the measurement step interval is 3 μm, for example.

  For example, SEM (JEOLJSM5410) manufactured by JEOL Ltd. is used as the SEM apparatus, and for example, EBSP: manufactured by TSL (OIM) is used as the EBSP measurement / analysis system.

(Production method)
The 5000 series (Al-Mg series) hot-rolled sheet of the present invention is a production method according to the production process of ordinary Al-Mg series alloys for forming, such as 5052, 5154, and 5083, until the hot rolling (hot rolling) process. It can be manufactured. That is, an aluminum alloy hot rolled sheet having a thickness of 1.6 to 2.5 mm is manufactured through normal manufacturing processes such as casting, casting, homogenization heat treatment, and hot rolling.

  A plate having a thickness of less than 1.6 mm is difficult to produce by hot rolling, and press forming itself is difficult if the thickness exceeds 2.5 mm. Accordingly, the thickness of the aluminum alloy hot-rolled sheet is preferably in the range of 1.6 to 2.5 mm.

  At this time, as described above, the hot-rolled sheet of the present invention is a non-tempered aluminum alloy hot-rolled sheet that has not been subjected to a tempering process including recrystallization annealing after hot-rolling, and remains in the state of hot-rolling . However, the scope of the present invention includes subjecting the hot-rolled sheet of the present invention to surface treatment such as improvement of corrosion resistance and lubricity before being press-formed on the user side. The tempering treatment that is not applied to the hot-rolled sheet of the present invention is a symbol according to quality, which is O (annealing: completely recrystallized material), H1n (hard material such as H14), H2n (hard material such as H24), H3n. Refining treatment such as (hard material such as H34).

  Here, the hot rolled sheet structure of the present invention is a recrystallized grain structure having a recrystallization annealing (final annealing) average crystal grain size of 25 μm or less and an average volume fraction of Cube orientation of 10% or less. Preferred production conditions are described below.

  In order to make the aluminum alloy hot-rolled sheet into such a structure, after the homogenized heat treatment of the melt-cast slab at 450 to 550 ° C., the rolling rate in the final roll is set to 30% or more, and the winding temperature is set to 300. It is preferable to perform hot rolling at a temperature not lower than ° C.

(Homogenization heat treatment)
When the slab melt-cast in the hot-rolled sheet component composition of the present invention is subjected to a homogenization heat treatment, the homogenization heat treatment temperature is set to a range of 450 to 550 ° C. If the homogenization heat treatment temperature is less than 450 ° C., it is not possible to ensure a coiling temperature of 300 ° C. or higher in the subsequent hot rolling, and the hot rolled sheet structure cannot be a recrystallized grain structure in the range of the above component composition. Or it becomes a mixed grain structure with the recrystallized grain structure in which the processed structure remains. For this reason, the structure of the hot-rolled sheet cannot be an average crystal grain size of 25 μm or less and an average volume fraction of Cube orientation of 10% or less. As a result, the press formability is significantly reduced as an aluminum alloy hot-rolled sheet that has not been subjected to a tempering treatment including recrystallization annealing after hot-rolling and remains hot-rolled. On the other hand, the homogenization heat treatment temperature does not need to be higher than 550 ° C., and on the contrary, burning is likely to occur, and there is a high possibility that hot rolling cannot be performed.

(Hot rolling)
The coiling temperature of the plate after hot rolling is 300 ° C. or higher. When the coiling temperature of the sheet after hot rolling is less than 300 ° C., as described above, the hot-rolled sheet structure cannot be made into a recrystallized grain structure, and is mixed with the processed structure or the recrystallized grain structure where the processed structure remains. It becomes a grain structure. For this reason, the hot-rolled sheet structure cannot be made to have an average crystal grain size of 25 μm or less and an average volume fraction of Cube orientation of 10% or less within the above component composition range.

  The rolling rate in the final roll (final stand pass) during hot rolling is set to 30% or more. That is, when the hot rolling process and the hot rolling finish rolling process are performed by a tandem finish rolling mill composed of a plurality of rolling mill rows arranged in series, the final roll rolling rate is set to 30% or more. . Moreover, even when performing by multiple passes in a reverse rolling mill or the like, the rolling rate in the final pass (final roll) is set to 30% or more. If the rolling rate in these final rolls is less than 30%, the hot-rolled sheet structure cannot be a recrystallized grain structure, and is a processed structure or a mixed grain structure with a recrystallized grain structure in which the processed structure remains. For this reason, the hot-rolled sheet structure cannot have an average crystal grain size of 25 μm or less and an average volume fraction of Cube orientation of 10% or less.

  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. Manufactured Al-Mg based alloy hot-rolled sheets of compositions A to E (invention examples), F, and G (comparative examples) shown in Table 1, and measured and evaluated the structure, mechanical properties, and formability, respectively. did.

  The method for producing a hot-rolled plate is to perform a homogenization heat treatment of a 400 mm-thick ingot cast by DC casting at each temperature shown in Table 2 in common for 8 hours, and then at a temperature near the homogenization heat treatment temperature. Hot rolling was started. This hot rolling was performed by a reverse type rough rolling mill and a tandem type finishing rolling mill, and the rolling rate in the final roll (final stand) in the finishing rolling mill was changed as shown in Table 2. Further, the hot rolling coiling temperature was also changed as shown in Table 2 mainly due to the difference in the homogenization heat treatment temperature (hot rolling start temperature).

  In common with each example, the thickness of the manufactured Al-Mg alloy hot-rolled sheet is 1.5 mm, and after the hot rolling, no refining treatment including recrystallization annealing is performed, and the hot-rolled state remains as it is. A non-heat treated hot rolled sheet was used. From these hot-rolled plates, test pieces or 500 mm square test plates (blanks) were cut out and subjected to various tests and evaluations.

(Organization)
Using the SEM-EBSP and EBSD described above, the average volume fraction of the Cube orientation at a total of 10 locations (total 5 locations in the outermost surface portion and the thickness center portion) in any part of the plate of each test plate ( %) Were measured and averaged under the conditions described above. At the same time, the crystal grain sizes at these measurement locations were also measured and averaged.

(Mechanical properties)
Tensile tests were performed on each of the test plates, and tensile strength (MPa), 0.2% proof stress (MPa), and elongation (%) were measured. These results are shown in Table 2. As test conditions, No. 5 test piece (25 mm × 50 mmGL × sheet thickness) of JISZ2201 perpendicular to the rolling direction was sampled from the hot-rolled sheet, and a tensile test was performed. The tensile test was conducted at room temperature of 20 ° C. based on JISZ2241 (1980) (metal material tensile test method). The crosshead speed was 5 mm / min, and the test was performed at a constant speed until the test piece broke.

(Hole expansion rate)
In the hole expansion test for evaluation of stretch flangeability, a hole having a diameter of 10 mm was first punched into a square plate having a side of 70 mm. Then, using a 60 ° conical punch with a diameter of 33 mm, with a burr on the upper surface (die surface) side, a hole expansion test was performed at a wrinkle holding force of 3 tons and a punch speed of 10 mm / min. At this stage, the punch was stopped, and the hole expansion rate (λ) was obtained from the following formula from the hole inner diameter (ds) after fracture and the initial hole diameter (d0) before the molding test.
λ = (ds−d0) / d0 × 100 (%)

  In the hole expansion test, the hole inner diameter after fracture was measured in the rolling direction of the plate and in the direction perpendicular to the rolling direction, and after obtaining the hole expansion ratio, taking the average, The hole expansion rate was used. Further, three hole expansion tests were performed on each test plate, and the average value was finally set as the hole expansion ratio (λ%).

(Square tube drawing test)
The test plate was subjected to a deep-drawing molding test into a square tube shape of 40 mmW × 40 mmL using a press. BHF (wrinkle pressing force) was about 40 kN. At this time, the molding was performed five times, and the molding was performed to reach the bottom dead center in all five times to form the rectangular tube shape. And the maximum height mm which could be shape | molded without defects, such as a crack, in the bottom corner | angular part of a square tube, etc. was measured. These results are also shown in Table 2.

  As shown in Table 2, Invention Examples 1 to 8 have respective compositions within the scope of the present invention, and the homogenization heat treatment, the rolling rate in the hot-rolled final roll, and the winding temperature are manufactured within the preferable range of conditions. For this reason, in the non-heat treated aluminum alloy hot-rolled sheet that has not been annealed after hot rolling, the average crystal grain size is 25 μm or less, and the average volume fraction of the Cube orientation is 10%. It has the following recrystallized grain structure. As a result, it is confirmed that Invention Examples 1 to 8 are excellent in stretch flangeability and square tube drawing formability, and are excellent in press formability.

  On the other hand, although Comparative Examples 9-12 have each composition (C) within the scope of the present invention, the conditions such as the homogenization heat treatment, the rolling rate in the hot-rolled final roll, the coiling temperature deviate from the preferred condition range. It is manufactured. Comparative Example 9 has an unrecrystallized structure because the homogenization heat treatment temperature and the coiling temperature are too low, and the rolling rate in the hot-rolled final roll is too low. Comparative Example 10 has an unrecrystallized structure because the rolling rate of the hot-rolled final roll is too low. In Comparative Example 11, since the homogenization heat treatment temperature was too high, cracking occurred during hot rolling, and it was impossible to produce a plate.

  In Comparative Example 13, the homogenization heat treatment, the rolling rate in the hot-rolled final roll, and the winding temperature are manufactured within the preferable condition range. However, since the Mg content is too small, the average grain size exceeds 25 μm Keiga. At the same time, stretch flangeability and rectangular tube drawing formability are inferior, and press formability is inferior. Moreover, since the comparative example 14 had too much Mg content, it cracked during hot rolling and the manufacture of the plate was impossible.

  The above examples support the critical significance of each requirement or preferred condition of the present invention.

  As described above, according to the present invention, an unheated Al—Mg-based (5000-based) aluminum alloy hot-rolled plate that can be press-formed while being hot-rolled and not annealed after hot-rolling is provided. it can. As a result, the application of the Al—Mg-based aluminum alloy plate to many uses such as the automobile described above, which is used by press-molding the plate, is expanded.

Claims (4)

  Mg: 2.0 to 6.0% by mass, further including one or more selected from Fe, Mn, Cr, Zr and Cu in a total of 0.03 to 2.5% by mass, the balance Is an aluminum alloy hot-rolled sheet made of Al and unavoidable impurities, which has not been annealed after hot rolling and is in a hot-rolled state, and has a recrystallization annealing (final annealing) average grain size of 25 μm or less. An aluminum alloy hot-rolled sheet excellent in press formability, characterized by having a recrystallized grain structure having an average volume fraction of Cube orientation of 10% or less.   The aluminum alloy hot-rolled sheet is hot rolled at a rolling rate of 30% or higher and a winding temperature of 300 ° C. or higher after the homogenized heat treatment at 450 to 550 ° C. for the melt-cast slab. The aluminum alloy hot-rolled sheet according to claim 1, wherein   The aluminum alloy hot-rolled sheet according to claim 1 or 2, wherein the aluminum alloy hot-rolled sheet has a thickness of 1.6 to 2.5 mm.   The aluminum alloy hot-rolled sheet according to any one of claims 1 to 3, wherein the aluminum alloy hot-rolled sheet is for automobile panels.