JP4164453B2 - Forming method of aluminum alloy material - Google Patents

Description

  The present invention relates to a method for forming an aluminum alloy material (hereinafter, aluminum is also simply referred to as Al), which recovers the formability of a 6000 series aluminum alloy material that has been age-hardened at room temperature and has reduced formability.

  Conventionally, Al alloy materials with excellent formability and bake hardenability have been used for transportation equipment such as automobiles, ships, aircraft or vehicles, machinery, electrical products, architecture, structures, optical equipment, and components and parts of equipment. Has been.

  In particular, in the field of the body of a transport device such as an automobile, in recent years, improvement in fuel consumption has been pursued by reducing the weight in response to global environmental problems caused by exhaust gas. For this reason, the application of lighter Al alloy materials such as rolled plates and extruded shapes instead of steel materials conventionally used for automobile bodies is increasing.

  Of these, panels such as outer panels (outer panels) and inner panels (inner panels) of panel structures such as automobile hoods, fenders, doors, roofs, and trunk lids are made of Al-Mg-Si AA to JIS. The use of 6000 series (hereinafter simply referred to as 6000 series) Al alloy sheets is being studied.

  6000 series Al alloy material basically contains Si and Mg as essential, and has excellent age-hardening ability, so it secures formability by reducing the yield strength during press molding and bending, and molding BH properties (bake hardness, artificial age hardening ability) that can ensure the required strength by age hardening by heating at the time of processing, such as paint baking treatment of the subsequent panel, and heat resistance during treatment. Paint bake hardenability).

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

  On the other hand, in the application field of the automotive panel structure, an Al alloy plate is formed into a panel by press forming such as overhanging, drawing or trimming. In recent years, with the adoption of Al alloy plates for automobile panels, the application to panels with more complex shapes and difficult to form has increased. For example, the panel shape to be stretch-formed tends to be complicated, such as the height and the area of the stretch are increased, and the shape has a curved portion that stretches and undergoes flange deformation. For this reason, molding defects such as cracking and rough skin during molding are more likely to occur.

  Of the automotive panels, the outer panel (outer panel) is joined to the inner panel (inner panel) after the press molding to form a panel structure, which is called 180 ° called flat hem processing, which has severe processing conditions. A severe bending process such as bending is applied in combination. This flat hem processing is a severe bending process called a hem (alternative name for hemming) process in which the edge of the outer panel is bent (folded 180 degrees) and joined to the edge of the inner panel.

  On the other hand, the 6000 series Al alloy material, due to its excellent age-hardening ability, after the production of the Al alloy material itself, before being used for each of the above applications, room temperature (room temperature) age hardening is likely to occur, There was a big problem of lacking room temperature stability. When such room temperature aging occurs, immediately after manufacturing, even if the 6000 series Al alloy material satisfies the required characteristics of each application, it is required when used for actual applications after a certain period of time. If it is a panel material without satisfying the characteristics, the press formability and hem workability, and further, the BH property (artificial age hardening) will be remarkably lowered.

  In particular, in flat hem processing of the above-mentioned Al alloy outer panel, when room temperature age hardening occurs, the edge of the formed flat hem (hem part, bent part) is likely to have defects such as relatively large cracks. Become.

  For the problem of room temperature aging control of these 6000 series Al alloy materials, Mg-- formed at room temperature after tempering treatment such as solution treatment and quenching treatment of 6000 series Al alloy materials on the material production side Metallurgical improvements such as controlling the structure of Si clusters have been made. However, the metallurgical suppression of room temperature aging also leads to a decrease in the BH property, and this is also limited.

  For this reason, a technique for forming a 6000 series Al alloy material while heating has been proposed on the forming side. In the field of aluminum alloy plates, in order to form difficult-to-process panels, the aluminum alloy plates are heated to produce high elongation characteristics in a high temperature region of 460 to 550 ° C. Various high-temperature forming methods such as high-speed superplastic forming and hot pressing have been studied. For example, a 6000 series aluminum alloy sheet that has not been subjected to a solution treatment or the like is blow-molded at a temperature required for a solution treatment of about 500 ° C., and then the tempered product is subjected to a tempering process to obtain a high pressure of 200 MPa or more. It has also been proposed to obtain proof stress (see Patent Document 1).

In addition, regarding bending of a plate, it has also been proposed to improve the hemmability by heating and quenching the hemming portion of the plate at 250 to 500 ° C. (see Patent Document 2). Furthermore, it has also been proposed to improve the hem workability by providing a heating means such as an electric heater on the work receiver or hemming edge of the hem machining die and heating it to around 200 ° C. (see Patent Document 3). Furthermore, even in bending of plates, shapes, pipes, etc., during bending of Al alloy material, using a high-frequency heating coil etc., the bending portion of 6000 series Al alloy material is heated and annealed, warm or It is disclosed that bending is performed hot (see Patent Document 4).
Japanese Patent Laid-Open No. 2001-58221 (claims, FIG. 1, pages 1 to 3) Japanese Patent No. 3343924 (Claims, Fig. 2, pages 1 to 4) Japanese Patent No. 3390479 (Claims, Fig. 1, pages 1 to 3) JP-A-6-277764 (Claim 3, FIG. 1, pages 1 to 3)

  However, with these technologies that heat or heat mold these 6000 series Al alloy materials, it is possible to improve the elongation of the processed portion of Al alloy materials or anneal them at least 200 times. Heated to a temperature of ℃ or higher. In addition, it was a metallurgical common sense that in order to improve the elongation of the processed part of the 6000 series Al alloy material or to anneal it, it is necessary to heat it to a temperature of 200 ° C. or more at least.

  For this reason, there is a problem in that the mechanical properties change partly, such as the strength of the heated portion of the 6000 series Al alloy material is lowered, and the reliability when used as a strength member is lacking.

  Also, in high temperature forming such as the above-mentioned high-speed superplastic forming, especially in the case of 6000 series Al alloy material, it exhibits different properties from the normal formability at normal temperature, and a new forming problem arises. There are problems such as lowering.

  These problems occur in the same manner or more significantly in a 6000 series aluminum alloy material that has been age-hardened at room temperature. For this reason, there has never been an effective and practical molding method for 6000 series aluminum alloy materials age-hardened at room temperature. Molding conditions have been sacrificed at the expense of design changes such as molding shape and efficiency in process and time. The fact is that measures such as mitigation were adopted.

  The present invention has been made paying attention to such a situation, and the purpose thereof is an aluminum alloy material capable of recovering the formability of a 6000 series aluminum alloy material whose formability is reduced by age hardening at room temperature. It is intended to provide a molding method.

  In order to achieve this object, the gist of the aluminum alloy material forming method of the present invention is that aging is performed by applying a processing strain of 1% or more to a 6000 series aluminum alloy material in advance and then heating it to a temperature of 50 to 150 ° C. It is to perform the curing recovery process and mold.

  The aluminum alloy material referred to in the present invention includes a rolled plate, a panel obtained by press-forming this plate, an extruded shape member, a tube material, and the like.

  In the present invention, a 6000 series Al alloy material which has been age-hardened at room temperature and deteriorated in formability compared to a material immediately after production is subjected to a processing strain of 1% or more in advance and heated to a temperature of 50 to 150 ° C. It was found that the formability of the 6000 series Al alloy material is recovered by performing age hardening recovery treatment.

  Normally, the mechanical properties of the 6000 series Al alloy material that has been age-hardened at room temperature, even if it is simply heated to the above-mentioned temperature of 50 to 150 ° C. without applying processing strain in advance, especially the formability is It does not change. However, when the processing strain is applied in advance and heating to such a low temperature, a phenomenon occurs in which the formability of the 6000 series Al alloy material age-hardened at room temperature is restored.

  The recovery treatment of the present invention is unique in that the recovery of formability does not appear unless processing strain is given in advance, and the above-mentioned 6000 series Al alloy material is heated to a temperature of at least 200 ° C. and molded. This also shows that the basic metallurgical mechanism differs from warm or hot forming technology.

  Details of the metallurgical mechanism of such a unique phenomenon are unknown, but by adding the above processing strain in advance, work hardening was added to the 6000 series Al alloy material, and the Al alloy structure once precipitated and hardened by room temperature aging It is assumed that the softening or the increase in elongation occurs, and the moldability is significantly recovered.

  Moreover, even when heated to a temperature of 50 to 150 ° C., there is no significant decrease in other tensile strength, proof stress, etc. of the 6000 series Al alloy material. In addition, the necessary strength such as dent resistance can be secured by artificial age hardening treatment such as paint baking treatment of the molded panel or molded member without the effect of lowering the BH property.

  For this reason, without sacrificing other necessary properties as a 6000 series Al alloy material, press forming such as drawing and overhanging of the plate, bending processing such as HAT bending and 90 degree bending of the plate, after pressing the plate Formability using mainly a mold can be greatly improved, such as bending processing such as hem processing of the panel, bending processing of extruded shape members, pipe materials, and the like.

  Moreover, the processing strain of 1% or more given in advance is a relatively light processing, and the heating temperature of 50 to 150 ° C. is also a relatively low temperature. There is also an advantage that it can be carried out without significant equipment remodeling or process change in the molding process.

Hereinafter, embodiments of the Al alloy plate of the present invention will be specifically described.
(Processing distortion)
In the age hardening recovery treatment of the present invention (hereinafter also simply referred to as recovery treatment), first, a work strain of 1% or more is imparted to a 6000 series Al alloy material that has been age hardened at room temperature. If the processing strain is less than 1%, the 6000 series Al alloy that has been age-hardened at room temperature even when heated to a temperature of 50 to 150 ° C. is not different from ordinary heat treatment without adding processing strain in advance as described above. The formability of the material does not recover. For this reason, it is necessary that the processing strain given in advance be at least 1%.

  However, it is not necessary to give a very large processing strain. On the other hand, if a large processing strain is applied too much, various disadvantages such as deformation of the 6000 series Al alloy material, reduction in thickness, or the need for new equipment for that purpose arise. The upper limit of preferred work strain depends on the degree of age-hardening at room temperature, the shape of the 6000 series Al alloy material, and the processing history (plates, panels, profiles, age hardening), but about 20% for plates, panels, etc. In the case of shape materials, it is about 50%. Accordingly, the preferred processing strain is in the range of 3 to 20% for plates and panels and in the range of 3 to 50% for profiles.

(heating)
In the age hardening recovery treatment of the present invention, the above-mentioned 6000 series Al alloy material imparted with a work strain of 1% or more is heated to a temperature of 50 to 150 ° C, preferably 80 to 130 ° C. When the heating temperature is less than 50 ° C., the formability of the 6000 series Al alloy material age-hardened at room temperature does not recover even when a large processing strain is applied. In addition, when the heating temperature is less than 80 ° C., the formability of the 6000 series Al alloy material age-hardened at room temperature may not be recovered when a small processing strain is applied.

  On the other hand, even when the heating temperature exceeds 150 ° C., the formability of the room temperature age-hardened 6000 series Al alloy material does not recover regardless of the amount of processing strain in advance. Even when the heating temperature is higher than 130 ° C., the formability of the room temperature age-hardened 6000 series Al alloy material may not be recovered depending on the amount of processing strain. The optimum heating temperature for 6000 series Al alloy material is selected in relation to the shape of 6000 series Al alloy material, processing history (plate, panel, profile, age hardening), amount of processing strain applied in advance, etc. To do.

  Although the heating time also depends on the thickness of the 6000 series Al alloy material, etc., if the actual temperature of the 6000 series Al alloy material that has been age-hardened at room temperature is within the above heating temperature range, at least 30 seconds to see safety A very short holding time of about 1 minute is sufficient. Therefore, in the recovery process of the present invention, it is not necessary to take a long heating time.

  The recovery treatment of the present invention is also unique in that the heating temperature is relatively low, and the above-described 6000 series Al alloy material is heated to a temperature of 200 ° C. or more at least to form by warm or hot forming technology. It is clear from this that the basic metallurgical mechanism is different. In addition, the recovery treatment of the present invention is also unique in that the formability recovery effect occurs in the short time described above.

  As long as the recovery process of the present invention is performed by a series of recovery processes in which processing distortion is applied and heating is performed, the moldability is recovered and the effect is maintained even after cooling once after the heating. Even if the 6000-series Al alloy material is aged again at room temperature due to long-term storage or the like after the recovery process of the present invention, the recovery process of the present invention may be performed again. Therefore, various molding described below can be performed at room temperature. That is, it is not necessary to perform the molding process at a high temperature except for heating for the recovery process of the present invention described later.

(Recovery method)
The case of a plate will be described as a method for recovering the 6000 series Al alloy material.
First, in the field of application such as the above-mentioned automobile panel, a process of forming an aluminum alloy plate by press forming such as overhanging, drawing or trimming, and further, as an outer plate (outer panel), further hem processing such as flat hem A bending process like the following is assumed. In this case, there are a case where the forming at the time of press forming for forming the panel into a panel is recovered and a case where the bending workability such as hem processing is recovered.

(Recovery of press formability)
When recovering formability when press forming the above plate into a panel, the material plate may be fully recovered, or the panel shape may be more complicated, curved to cause deformation of the stretch flange A recovery process may be performed by selecting a part that is difficult to form, such as a part.

  Specifically, using a straightening machine such as a roll or tension (tension leveler) or a mold, etc., to the plate before being installed in the press mold, the tension is applied and the processing strain is applied in advance. Also good. Further, the processing strain may be applied to a plate installed in the press mold by applying tension to the plate by a press mold or by another means. For these, a rational method and equipment are appropriately selected according to the current equipment situation.

  Then, the subsequent heating may be performed on the entire plate or only on the forming portion. In addition, the plate before being placed in the press molding die may be heated to the low temperature by a heating means or a furnace, and the press molding die is heated to the low temperature before pressing or pressing. During molding, the plate may be heated to the low temperature. At this time, the mold used for press molding may be provided with a heating means for the recovery process, but a means for heating to a high temperature of 200 ° C. or higher as in the prior art is unnecessary, and the recovery process is performed instead. The effect is impaired.

  By such a recovery treatment of the present invention, room temperature age-hardened 6000 series Al alloy plate recovers (improves), for example, stretch formability, draw formability, stretch flange deformability, and cracks during press molding, Molding defects such as rough skin are less likely to occur.

(Recovery of bending workability)
When restoring the bending workability of the plate or panel, such as HAT bending, 90 ° bending, and hem, or when bending the shape material, these bending materials may be fully recovered. Alternatively, select a bent portion of the bending material or a portion that is difficult to be bent. For example, if it is a bent portion of a plate, the bending outer peripheral shape is linear or not linear, but an arc shape, etc. A portion that is more difficult to be bent may be selected and recovered.

  Specifically, the bending material before being installed in the bending mold is given a tension using a straightening machine such as a roll or tension (tension leveler) or a mold, and the processing distortion is applied. Also good. Further, the bending distortion may be applied to the bending material installed in the bending die by applying tension or the like by a bending die or by another means. For these, a rational method and equipment are appropriately selected according to the current equipment situation.

  And the subsequent heating may also be performed on the entire bent material or only the bent portion. Specifically, the bending material before being installed in the bending mold may be heated to the low temperature by a heating means or a furnace, and the bending mold is selectively heated to the low temperature. Then, the bending material before or during molding may be heated to the low temperature. At this time, the bending die may be provided with a heating means for the recovery process, but the means for heating to a high temperature of 200 ° C. or higher as in the prior art is not necessary, and the effect of the recovery process is rather reversed. To lose.

(Recover heme workability)
Among these bending processes, the case where flat hem workability is restored will be described below. Figures 1 (a) to 1 (c) show the general flat hem processing of panels (plates) after press molding. As shown in the figure, the flat hem processing is performed by using the die by the flat flange process of FIG. 1 (c) through the down flange process of FIG. 1 (a) and the pre-hem process of FIG. 1 (b). Done.

  First, FIG. 1 (a) shows the outer panel 1 after press forming, which is fixed by a die 101 and a plate presser 102. Then, a force is applied to the outer edge 1a indicated by the dotted line of the outer panel 1 in the direction orthogonal to the outer panel 1 (upward in the figure) as indicated by the arrow in the figure by the punch 100. Then, the outer edge portion 1a is bent to an angle close to a right angle (90 °) to form a bent portion 1b.

  Next, FIG. 1 (b) similarly shows the outer panel 1 after the down flange process, which is fixed by a die 104 and a plate presser 102. In this pre-hem step, a bent portion 1b is formed by bending the outer edge portion 1a indicated by the dotted line of the outer panel 1 further to the inside of the panel to about 135 ° by the punch 103. At this time, the punch 103 causes the outer edge 1a indicated by a dotted line bent at a right angle to be perpendicular to the outer panel 1 (as shown in the figure) as indicated by the two arrows in the figure by the punch 103. Forces are applied in two directions: (downward) and parallel to the outer panel 1 (lateral direction in the figure).

  Further, in the flat hem process of FIG. 1 (c), the outer edge portion 2a of the inner panel 2 after the molding process such as the drawing process and the trim process is inserted (accommodated) into the bent portion 1b of the outer panel 1 after the pre-hem process. To do. Then, the outer panel 1 and the inner panel 2 are fixed by a plate presser (not shown) and a die 102, and the outer edge 1a of the outer panel 1 is further bent inside the panel by a punch 105 to an angle of 180 ° to be flat. Form a hem. In this way, the outer edge portion 2a of the inner panel 2 and the flat hem portion (180-degree bent portion) of the outer panel 1 come into contact with each other and are bonded together at the end portions.

  In the case of roped hem processing, the steps of FIGS. 1 (a) and (b) are the same as the flat hem processing, except that the bent portion 1b is not a flat hem. A bent shape that bulges outward in a circular arc shape (in a rope shape). For this reason, compared with a flat hem, it is not a sharp hem shape and its appearance is not good. In addition, there is a problem that the contact area between the outer panel and the inner panel is small and the bonding property and adhesion are lacking. For this reason, in particular, in automotive parts and the like that place importance on the appearance and aesthetics, the final process of hem processing is usually performed by the flat hem process of FIG. 1 (c), which is a severe bending process.

In the case of such flat hem processing, the method of imparting the processing strain is preferable without requiring an extra step as long as the processing strain necessary for the recovery process is applied at the time of press forming as the previous step. In order to supplement the processing distortion at the time of press molding or to newly add processing distortion, the processing distortion may be applied in advance to the hem processing portion of the panel before being installed in the hem processing mold.
However, this method is effective only for recovering formability in the down flange process, which is the first process, when bending is performed over a plurality of stages such as hem processing. In a multi-stage process such as hem processing, the processing conditions in the subsequent pre-hem process and flat hem process become more severe, and cracks are likely to occur.

  Therefore, it is important to further recover the formability of the subsequent pre-hem process and flat hem process, and in this case, the processing strain applied in the bending process of the previous down-flange process is recovered by the present invention. Used as processing distortion required for processing. And after the down flange process and before the pre-hem process, or during the bending process of the pre-hem process and the flat hem process, the heating necessary for the recovery process is performed, and the pre-hem process and the flat hem process, which are subsequent stages, are performed. It is preferable to selectively recover the formability of the bending process. In this method, the panel processed in the down-flange process mold is often reset to the pre-hem and flat-hem process molds. It is also preferable in that it can be performed.

  As a method for imparting processing distortion, tension may be applied using a straightening machine such as a roll or tension (tension leveler). In addition, in order to give processing distortion by the above-mentioned down flange process itself, for example, by cooperation of the die 101, the plate presser 102, the punch 100, etc. in FIG. The processing distortion is given. However, in these cases, a rational method and equipment are appropriately selected according to the current equipment situation.

  Then, the subsequent heating may be performed on the entire panel or only on the hemming portion. Specifically, the panel before being installed in the hem processing mold may be heated to the low temperature by a heating means or a furnace, and the mold in each of the hem processing steps is selectively set to the low temperature. The plate before hemming or during hemming may be heated to the low temperature. At this time, a low-temperature heating means for the above-described recovery treatment may be selectively provided in the mold in each hem processing step.

  Such recovery treatment of the present invention recovers (improves) the bending workability such as flat hem of the 6000 series Al alloy material that has been age-hardened at room temperature, and cracks and rough skin that are likely to occur in the bent portion and hem portion of the plate, Alternatively, molding defects such as cracks and wrinkles that are likely to occur in the bent portion of the mold material are less likely to occur.

(Chemical composition)
Next, the chemical component composition of the 6000 series Al alloy material targeted by the present invention will be described. The 6000 series Al alloy material targeted by the present invention is required to have excellent properties such as formability, BH property, strength, weldability, and corrosion resistance as the above-mentioned automobile material. In order to satisfy such requirements, the basic composition of the Al alloy material is preferably an aluminum alloy material containing Mg: 0.2 to 2.0% and Si: 0.3 to 2.0% by mass%. In the present invention, “%” for the chemical component composition means “% by mass”, including “%” in claims.

  Further, the 6000 series Al alloy material targeted by the present invention has a problem of age-hardening at room temperature due to its excellent BH property, and requires the recovery treatment of the present invention. In this respect, among the 6000 series Al alloys, the recovery treatment of the present invention has a better BH property, so that age hardening at room temperature becomes more problematic, so-called Si-rich 6000 having a Si / Mg mass ratio of 1 or more. It is preferable to be applied to a system Al alloy material. As such a 6000 series Al alloy material, for example, there is a plate for an outer panel as an automobile material, and the composition is Mg: 0.2 to 2.0%, Si: 0.3 to 2.0%, Mn: 0.01 to 0.65%, It is preferable to contain Cu: 0.001 to 1.0%, Si / Mg is 1 or more by mass, and the balance is Al and inevitable impurities.

  For other elements, the content (allowable amount) of each impurity level in accordance with AA or JIS standards. Specifically, the other alloy elements include Fe: 1.0% or less, Mn: 1.0% or less, Cr: 0.3% or less, Zr: 0.3% or less, V: 0.3% or less, Ti:% or less. One type or two or more types may be selectively included. In addition to or instead of these, one or more of Ag: 0.2% or less and Zn: 1.0% or less may be selectively contained.

  Other alloy elements and gas components other than the above alloy elements are impurities. However, from the viewpoint of recycling, not only high-purity Al ingots but also 6000 series alloys and other Al alloy scrap materials, low-purity Al ingots, etc. are used as melting raw materials as melting materials. In the case of melting, these other alloy elements are necessarily included. Accordingly, the present invention allows these impurity elements to be contained within a range that does not impair the intended effect of the present invention.

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

Si: 0.2-2.0%
Si forms a compound phase (β ") together with Mg during solid-solution strengthening and artificial aging treatment at relatively low temperatures, such as paint baking after molding, and exhibits age-hardening ability. Therefore, it is an indispensable element for obtaining the necessary strength as an element, and is therefore the most important element for combining the necessary properties as a panel, such as press formability. Furthermore, it cannot combine various properties required for each application, such as press formability, etc. On the other hand, if Si exceeds 2.0%, press formability and bending workability are significantly hindered. In addition, the weldability is significantly hindered, so Si should be in the range of 0.2 to 2.0%.

Mg: 0.2-2.0%
Mg is an indispensable element for forming the compound phase together with Si during the artificial aging treatment such as solid solution strengthening and paint baking treatment, to exhibit age hardening ability and to obtain the required strength as the panel . If the Mg content is less than 0.2%, the absolute amount is insufficient, so that the compound phase cannot be formed during the artificial aging treatment, and the age hardening ability cannot be exhibited. For this reason, the said required intensity | strength required as a board cannot be obtained. On the other hand, if the Mg content exceeds 2.0%, the formability such as press formability and bending workability is significantly inhibited. Therefore, the Mg content is in the range of 0.2 to 2.0%.

Cu: 0.001 to 1.0%
Cu is useful for improving the age hardening rate in 6000 series Al alloys. That is, it has the effect of promoting the precipitation of a compound phase such as a GP zone into the crystal grains of the Al alloy material structure under the conditions of artificial aging (hardening) treatment such as a paint baking process. Moreover, Cu dissolved in the artificial aging treatment state also has an effect of improving formability. If the Cu content is less than 0.001%, these effects are insufficient. However, if the Cu content exceeds 1.0% and is too large, there is a high possibility that a coarse compound is formed and the moldability is deteriorated. In addition, there is a high possibility that the corrosion resistance such as yarn rust resistance required for an automobile outer panel will deteriorate. Therefore, the upper limit of the Cu content is preferably 1.0% or less.

Mn: 0.01 to 0.65%
Mn is useful for refining crystal grains and can improve moldability. Mn generates dispersed particles (dispersed phase) during the homogenization heat treatment, and these dispersed particles have an effect of hindering grain boundary movement after recrystallization. However, if each content is too large, a coarse compound is formed, which becomes a starting point of destruction, and the moldability deteriorates instead. Therefore, it is preferable to contain Mn in the range of 0.01 to 0.65%.

(Average crystal grain size)
In defining these structures, it is preferable to refine the average grain size of the Al alloy plate to 50 μm or less. By making the crystal grain size fine or small within this range, bending workability and press formability can be ensured or improved. When the crystal grain size becomes larger than 50 μm, the press formability such as bending workability and overhang is remarkably deteriorated, and defects such as cracking and rough skin are easily generated.

  The crystal grain size referred to here is the maximum diameter of crystal grains in the longitudinal (L) direction of the plate. The crystal grain size is measured by a line intercept method in the L direction by observing the surface of the Al alloy plate that has been mechanically polished by 0.05 to 0.1 mm and then electrolytically etched using an optical microscope. 1 The measurement line length is 0.95mm, and the total measurement line length is 0.95 x 15mm by observing a total of 5 fields with 3 lines per field.

(Production method)
The production of the Al alloy material is possible by a conventional method according to the shape. In the melting and casting process of Al alloy, select a normal melting and casting method such as continuous casting and rolling, semi-continuous casting (DC casting), etc. And cast. Then, after subjecting this Al alloy ingot to homogenization heat treatment by a conventional method, it is hot-rolled and hot-extruded to obtain a product material such as a coil shape, a plate shape, a shape material, a pipe material, If necessary, intermediate annealing is performed, cold rolling is performed, and the product is rolled into a product cold-rolled sheet such as a coil or plate. These processed Al alloy materials are tempered by solution treatment and quenching as a tempering treatment, and are used as product plates. Of course, it is possible to add a tempering treatment such as an aging treatment or a stabilization treatment at a higher temperature according to the use and required characteristics.

  Next, examples of the present invention will be described. After the Al alloy plate aged at room temperature was subjected to the recovery treatment of the present invention, the press formability and hem workability were evaluated.

  That is, the 6000 series Al alloy plate having an excess Si type composition of A shown in Table 1 was allowed to stand at room temperature for 4 months and aged at room temperature. The tensile test characteristics of this Al alloy sheet aged at room temperature are 0.2% after aging compared to the As0.2% proof stress of 128MPa and As elongation of 30% for the Al alloy sheet after tempering treatment (immediately after production). The yield strength increased by 163 MPa and 35 MPa with the Δ yield strength, and the elongation after aging decreased by 25% and the Δ elongation by 5%. The average grain size of the Al alloy plate after aging at room temperature was 30 μm according to the grain size measurement method.

This tensile test characteristic was measured by using the yield strength (σ _0.2 ) parallel to the rolling direction of the Al alloy sheet (σ _0.2 ) as the As yield strength (MPa). The tensile test was performed according to JIS Z 2201 and the shape of the test piece was a JIS No. 5 test piece. The crosshead speed was 5 mm / min, and the test piece was run at a constant speed until the test piece broke.

  In addition, the manufacturing conditions of the Al alloy plate of the test material are as follows. 400 mm thick ingots having the respective compositions shown in Table 1 were melted by the DC casting method, subjected to homogenization heat treatment at 550 ° C., and hot rolled to a thickness of 5 mm at an end temperature of 300 ° C. This hot-rolled sheet was subjected to intermediate annealing at 400 ° C. for 4 hours in a batch-type heat treatment facility, and then cold-rolled at a cold rolling rate of 80% to obtain a cold-rolled sheet having a thickness of 1.0 mm. The cold-rolled sheet was subjected to a solution treatment at 510 ° C. in a continuous heat treatment facility, and then quenched to room temperature, and within 30 minutes after the quenching, a pre-aging treatment at 70 ° C. × 1 hour was performed.

  The same plate aged at room temperature was subjected to recovery treatment under various conditions shown in Table 2 and then simulated to be press-molded and hem-processed as automobile panel materials. Evaluated. These results are also shown in Table 2.

  In this case, the recovery process is performed in common for the Al alloy plate of the test material in advance before the press molding test and the hem processing test, and after this recovery process, after cooling (cooling) to room temperature. Each molding test was performed on the plate. Moreover, the test material for the press molding test and the hem processing test under each recovery treatment condition was performed so that the same recovery treatment condition was obtained. Specifically, an Al alloy plate as a test material was subjected to tension by a tension leveler straightening machine to give processing strain. Then, the Al alloy plate imparted with the processing strain was heated to each predetermined temperature in a heating furnace and held at that temperature for 1 minute. The heated plate was allowed to cool to room temperature and molded.

The press formability is evaluated by the plane strain overhang height (LDH ₀ ) test, and the test conditions are 100 mm wide × 180 mm long sampled specimens, and the longitudinal direction of the specimen coincides with the direction perpendicular to the rolling direction. It produced as follows. Then, at room temperature, using a punch (ball head, 100mmφ) and a die (with beads), it was performed 3 times under the conditions of wrinkle holding force 200kN, lubricating oil R-303, molding speed 20mm / min. The protruding height was defined as LDH ₀ value (mm). During the test, the LDH ₀ value was not obtained for the test material that was broken even once.

  Hem workability was evaluated by performing a bending test after 10% stretching of the test material at room temperature, simulating the flat hem processing after the press molding. The test specimen conditions were No. 3 test specimen (width 30 mm × length 200 mm) defined in JIS Z 2204, and the specimen was prepared so that the longitudinal direction of the specimen coincided with the rolling direction. The bending test was performed by simulating flat hem processing using the V-block method specified in JIS Z 2248, bending it to 60 degrees with a clamp with a tip radius of 0.3 mm and a bending angle of 60 degrees, and then bending to 180 degrees. It was. At this time, for example, in the hem processing of the outer panel, the inner panel is sandwiched in the bent portion, but in order to make the conditions strict, it was bent at 180 degrees without sandwiching such an Al alloy plate. Observe the occurrence of cracks in the bent part (curved part) after the test, ○ if there is no crack or rough skin on the bent part surface, △ if there is no crack but rough skin, Things were rated as x.

  First, as shown in Table 2, Comparative Example 1 is a 6000 series Al alloy plate having an excess Si type composition that has been aged at room temperature and has reduced formability. This corresponds to the conventional example showing the case. In this case, as a matter of course, breakage occurs even in press molding, and cracks occur in the bent portion even in hem processing, which indicates that molding is difficult in this state aged at room temperature.

  In contrast, Invention Examples 8 to 14, which were subjected to a recovery treatment within the range of the present invention, were 6000 series Al alloy plates with an excess Si type composition that had been aged at room temperature and had a reduced formability. The press formability and hemmability are improved or recovered. Therefore, the moldability improvement or recovery effect by the recovery process of the present invention is supported.

  In addition, both Comparative Example 2 that was heated but not preliminarily applied with processing strain, and Comparative Example 3 that was preliminarily applied with processing strain and not heated were also broken in press molding and bent in hem processing. There is a crack in the part. Therefore, the significance of the combination of processing strain application and heating in the recovery process of the present invention is supported.

  Furthermore, the processing strain amount of the recovery treatment is 0.8%, which is out of the lower limit 1.0% of the processing strain amount of the recovery processing of the present invention, and the heating temperature of the recovery processing is 45 ° C. In Comparative Example 5 that deviates from the lower limit of 50 ° C., press moldability and hemmability are inferior to those of the inventive examples. Among invention examples, Invention Example 8 in which the amount of processing strain in the recovery process is close to the lower limit, Invention Example 13 in which the heating temperature in the recovery process is close to the lower limit, Invention Example 14 in which the heating temperature in the recovery process is close to the upper limit Compared to Invention Examples 9 to 12, press formability and hemmability are relatively low. Therefore, from these results, the critical significance of the processing strain amount condition and the heating temperature condition in the recovery process of the present invention can be understood.

  Next, as an automotive outer panel, the same Al alloy plate as in Example 1 was evaluated by simulating that the panel was left to age at room temperature after press molding and then hemmed. These results are shown in Table 3.

  In press molding, a square test plate (blank) with a side of 500 mm is cut out from an Al alloy plate that has not been aged at room temperature immediately after production, and a square tube shape with a side of 300 mm and a height of 30 mm. A hat-shaped panel having a protruding portion and a flat flange portion (width 30 mm) around the four portions of the protruding portion was stretch-formed by a mechanical press using a die with a bead. The wrinkle holding force was 49 kN, the lubricating oil was general rust preventive oil, and the molding speed was 20 mm / min under the same conditions.

  The molded hat panel was left for 4 months and allowed to age at room temperature. The tensile test characteristics of this molded panel aged at room temperature are 0.2% after aging compared to the As 0.2% proof stress of 128MPa and As elongation of 30% for the Al alloy sheet after tempering treatment (immediately after production). % Proof stress was 169MPa and Δ proof stress was increased by 41MPa, and elongation after aging was 22% and DELTA elongation was 8% lower. The conditions for measuring the tensile test characteristics are the same as in Example 1.

  And the flat hem processing test was carried out on the flat flange part in this forming hat type panel. The flat hem processing allowance (distance from the end folded to the end of the panel after hem processing to the end of the bent portion) is set to 12 mm, the down flange process is simulated, and the edge of the Al alloy panel is set at an angle of 90 degrees. Bent until. At this time, the 90 ° bend radius of the Al alloy panel was set to 0.8. Next, the pre-hem process was simulated, and the edge of the Al alloy panel was further bent inward to an angle of 135 °.

  After that, simulating severe flat hem process conditions, flat hem processing was performed in which the inner panel was not inserted into the bent part of the Al alloy panel, but the bent part was bent inward by 180 degrees and adhered to the panel surface. The flat hem processing direction was made to coincide with the rolling direction of the original Al alloy sheet.

  Then, the surface state of the flat hem, such as rough skin, minute cracks, and large cracks, was visually observed. Evaluation was made by observing the occurrence of cracks in the bent part (curved part) after the test, ◯ if there was no more cracks or rough skin on the surface of the bent part, △ if there was no crack but rough skin occurred, The thing with a crack was evaluated as x.

  Note that the age hardening recovery process at the time of hem processing is performed by first performing the above-described down flange process on the flat flange portion of the molded hat panel, and the 10.0% processing strain of the present invention recovery process. Was given in advance.

  And while setting the panel which gave this down flange process to a prehem and a flat hem process metal mold again, a flange part is heated with a heater intermediately, and heat processing of this invention recovery processing is performed. It was. Then, the panel which performed these recovery processes was set to the prehem and flat hem process metal mold | die, and the prehem process and the flat hem process were performed in order.

  At this time, as shown in Table 3, in Invention Example 19, the intermediate heating was performed at 80 ° C., and the subsequent pre-hem step and flat-hem step were not heated, and were molded at room temperature. In Invention Example 20, the intermediate heating was performed at 80 ° C., and molding was performed while heating to 80 ° C. in the subsequent prehem step and flat hem step. In Invention Example 21, the intermediate heating was performed at 100 ° C., and the subsequent pre-hem step and flat-hem step were not heated but molded at room temperature.

  For comparison, each of the comparative examples not subjected to intermediate heating in the recovery treatment of the present invention was also tested for flat hem processing. Comparative Example 15 was molded at room temperature without heating even in the subsequent pre-hem step and flat-hem step. In Comparative Example 16, in the subsequent pre-hem step and flat-hem step, molding was performed by heating to 200 ° C. outside the scope of the present invention. In Comparative Example 17, the intermediate heating was heated to 200 ° C. outside the range of the present invention, and the subsequent prehem step and flathem step were molded at room temperature without heating. In Comparative Example 18, the intermediate heating was heated to 200 ° C. outside the range of the present invention, and the subsequent pre-hem step and flat hem step were also heated to 200 ° C. for molding.

  As shown in Table 3, Comparative Example 15 is a molded hat-type panel composed of a 6000 series Al alloy having an excess Si type composition that has been aged at room temperature and has reduced formability. This corresponds to a conventional example showing the case of processing. In this case, as a matter of course, the bent portion is cracked by the hem processing, which indicates that molding is difficult in the state of the panel aged at room temperature.

  In contrast, Invention Examples 19 to 21, which were subjected to a recovery treatment within the scope of the present invention, were formed hat-type panels made of an excess Si-type composition 6000 series Al alloy that had been aged at room temperature and had reduced formability. Despite being, heme workability is improved or recovered. Therefore, the moldability improvement or recovery effect by the recovery process of the present invention is supported.

  On the other hand, in Comparative Examples 16, 17, and 18 in which the recovery treatment was not performed within the range of the present invention, the bent portion was cracked by the hem processing.

  Therefore, the significance of the combination and conditions of applying the processing strain and heating for the hem processing of the molded panel in the recovery processing of the present invention is supported.

  Next, after subjecting the Al alloy extruded hollow profile aged at room temperature to the recovery treatment of the present invention, the bending workability was evaluated.

  Specifically, aluminum alloy billets of each 6000 series component composition of B shown in Table 1 are melted by DC casting, homogenized heat treatment at 480 ° C. × 4 hr, and extrusion processing is performed at an extrusion temperature of 480 ° C. Immediately after extrusion, each was directly quenched by water cooling online. Subsequently, these extruded materials were commonly subjected to aging treatment at 190 ° C. × 3 hours. The extrusion rate was 5 m / min, the extrusion ratio was 61, and the cooling rate during direct quenching was 350 ° C./second.

  This extruded hollow section had a uniform rectangular (mouth shape) cross section in the longitudinal direction. The long side of the rectangular cross section was 100 mm, the short side was 70 mm, and the wall thickness was 1.5 mm.

  The extruded hollow profile was left to age for 4 months at room temperature. The tensile test characteristics of this extruded hollow profile aged at room temperature are as follows: As 0.2% proof stress of 206 MPa and As elongation of Al alloy extruded hollow profile after aging treatment (immediately after production) The 0.2% proof stress after aging increased by 230MPa and ΔMP by 24MPa, and the post-aging elongation decreased by 14.0% and by Δ% by 2.1%. The tensile test characteristic measurement conditions are the same as in Example 1. The average crystal grain size of the Al alloy extruded shape after the room temperature aging was 40 μm according to the crystal grain size measuring method.

  The same extruded hollow shape material aged at room temperature was subjected to recovery treatment under various conditions shown in Table 4, and then bent as a member of an automobile frame or a bumper reinforcement member. Processability was evaluated. These results are also shown in Table 4.

  In this case, the recovery treatment was performed by using the draw bender shown in Table 4 for the bent portion of the extruded hollow profile after installing it on a general-purpose draw bender that used the extruded hollow profile of the test material for bending. Strain was applied in advance. Then, the bent portion of the extruded hollow profile imparted with the processing strain was heated from the vicinity of the draw bender to each predetermined temperature with a heater and held at that temperature for 1 minute. And after this holding | maintenance, bending was continuously performed with the drawbender.

  In the bending test, a specimen with a length of 2000 mm was used, and a bending test using a draw bender that was widely used for bending was performed. The bending inner radius R was 300 mm. The mechanical clearance during bending was set to 0.1 mm.

  Visual observation evaluated the generation | occurrence | production state of the crack of the profile surface used as the bending outer side of the sample after a bending process, and the wrinkle of the profile surface surface used as a bending inner side. Bending samples with no cracks or wrinkles are considered to be excellent in bending workability, △ are those with minute cracks or wrinkles, and those with opening cracks are inferior in bending workability As x, each was evaluated.

  First, as shown in Table 4, Comparative Example 22 is a 6000 series Al alloy extruded material with an excess Si type composition that was aged at room temperature and reduced formability, and was subjected to bending without performing the recovery treatment of the present invention. This corresponds to the conventional example showing the case. In this case, as a matter of course, cracks and wrinkles are generated even in the bending process, which indicates that the bending process is difficult in this state aged at room temperature.

  On the other hand, Invention Examples 29 to 35 which were subjected to the recovery treatment within the range of the present invention were 6000 series Al alloy extruded shapes having an excess Si type composition that had been aged at room temperature and had reduced bending workability. Nevertheless, the bending workability is improved or recovered. Therefore, the improvement of bending workability or the recovery effect by the recovery process of the present invention is supported.

  In addition, both Comparative Example 23, which was heated but not given processing strain in advance, and Comparative Example 24, which was provided with processing strain in advance but not heated, were cracked or wrinkled by bending. Therefore, the significance of the combination of processing strain application and heating in the recovery processing of the present invention is also supported in the extruded profile.

  Furthermore, the amount of processing strain in the recovery process is 0.8%, a comparative example 25 that deviates from the lower limit 1.0% of the amount of processing strain in the recovery process of the present invention, and the heating temperature of the recovery process is 45 ° C. Comparative Example 26, which deviates from the lower limit of 50 ° C., is also inferior in bending workability to the inventive examples. Among invention examples, invention example 29 in which the amount of processing distortion in the recovery process is close to the lower limit, invention example 34 in which the heating temperature in the recovery process is close to the lower limit, invention example 35 in which the heating temperature in the recovery process is close to the upper limit, Compared to Invention Examples 30 to 33, the bending workability is relatively low. Therefore, from these results, the critical significance of the processing strain amount condition and the heating temperature condition of the recovery treatment of the present invention in the extruded shape is also understood.

  ADVANTAGE OF THE INVENTION According to this invention, the shaping | molding method of the aluminum alloy material which can recover the moldability of the 6000 series aluminum alloy material in which formability fell by age-hardening at room temperature can be provided. As a result, for transportation equipment such as automobiles, ships, aircraft or vehicles, machinery, electrical products, architecture, structures, optical equipment, equipment parts and parts, and in particular, for transportation equipment parts such as automobiles, Al The application of alloy materials can be expanded.

It is explanatory drawing which shows hem processing of an Al alloy plate.

Claims (10)

  A method for forming an aluminum alloy material, comprising subjecting a 6000 series aluminum alloy material to an age hardening recovery treatment in which a processing strain of 1% or more is preliminarily applied and then heated to a temperature of 50 to 150 ° C.   The method for forming an aluminum alloy material according to claim 1, wherein the forming is press forming.   The method for forming an aluminum alloy material according to claim 1, wherein the forming is bending.   The method for forming an aluminum alloy material according to claim 3, wherein the bending process includes a plurality of steps, and the age hardening recovery process is selectively performed in the plurality of steps.   The method for forming an aluminum alloy material according to claim 3 or 4, wherein the aluminum alloy material is an aluminum alloy plate or a panel after the aluminum alloy plate is press formed.   The method for forming an aluminum alloy material according to claim 3, wherein the bending process is a hemming process.   The method for forming an aluminum alloy material according to claim 6, wherein the hemming is performed on a panel after press-molding an aluminum alloy plate.   The method for forming an aluminum alloy material according to claim 7, wherein the panel is for an automobile outer panel.   The method for forming an aluminum alloy material according to any one of claims 1 to 8, wherein a heating means for the age hardening recovery treatment is provided in a mold used for the forming. The 6000 series aluminum alloy material contains, by mass%, Mg: 0.2 to 2.0%, Si: 0.3 to 2.0%, Mn: 0.01 to 0.65%, Cu: 0.001 to 1.0%, and Si / Mg is a mass ratio. The method for forming an aluminum alloy material according to any one of claims 1 to 9, comprising at least 1 and comprising the balance Al and inevitable impurities.