JP2008019483A - Aluminum alloy sheet for warm-forming and warm-forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a 6000 series Al alloy sheet improving a warm-formability and a warm-forming method therefor. <P>SOLUTION: Al-Mg-Si based alloy sheet is composed of the range of 0.25-1.25 at% Si and Mg contents corresponding to Mg<SB>2</SB>Si composition and the gap from Mg<SB>2</SB>Si of composition and the gap from the Mg<SB>2</SB>Si of contents of these Si and Mg are respectively in the range of ≤0.5 at% and the balance aluminum with inevitable impurities, and as the characteristic of this sheet, the local extension is ≥20% at 300°C and this local extension to the whole extension is made to ≥60% and the warm formability thereof is improved. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an Al—Mg—Si based alloy plate for warm forming in which a forming process such as press forming is performed warm, and a warm forming method for the Al—Mg—Si based alloy plate. The aluminum alloy plate referred to in the present invention refers to an aluminum alloy produced in a plate shape by rolling, extrusion, forging, casting or the like. Hereinafter, aluminum is also referred to as Al, and an Al—Mg—Si alloy plate is also referred to as 6000 Al alloy plate.

  As is well known, various aluminum alloy plates have conventionally been used for each alloy for transporting machines such as automobiles, ships, airplanes or vehicles, machines, electrical products, architecture, structures, optical instruments, and components and parts of equipment. It is widely used depending on the characteristics.

  In many cases, these aluminum alloy plates are formed by press molding or the like, and are used as members and parts for the above-described applications. For this reason, conventionally, Al-Mg alloy (5000 series Al alloy) plates having relatively good formability have been used.

  On the other hand, the 6000 series Al alloy plate has a relatively small amount of alloy elements as compared to 5000 series and other Al alloys 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. In addition, 6000 series Al alloy plate basically contains Si and Mg as essential and has excellent age-hardening ability, so at the time of press molding and bending, it ensures formability by reducing the yield strength. BH properties (bake hardness, artificial aging) that can improve the proof stress by heating at the time of relatively low-temperature artificial aging (curing) treatment, such as paint baking treatment of molded panels, and improve the yield strength. Curability and paint bake hardenability).

  However, the press formability of the 6000 series Al alloy plate is not as good as that of the 5000 series Al alloy plate. For this reason, until now, in order to improve the properties of the material plate side, the addition of the third and fourth elements other than Mg and Si, or the addition of alloy elements, the crystal grain size, the dispersion state of the crystal precipitates Various methods have been tried for metallurgical improvements to control the microstructure such as grain boundary precipitates.

  On the other hand, a method for improving the formability of an Al alloy sheet has also been proposed from the processing side of press forming. One example is warm forming. This warm forming is, for example, a method of forming a plate by setting the punch portion at room temperature and the die portion warm. This warm forming is at a relatively low temperature as compared with hot forming and blow forming, and there is no fear that the properties of the plate will change at high temperatures, and the formability of the Al alloy plate is greatly improved.

  Various methods for forming an aluminum alloy plate by this warm forming have been proposed. For example, a 5000 series aluminum alloy plate excellent in warm formability has been proposed (see Patent Documents 1 and 2).

  Further, Fe: 0.5 to 2.0 wt%, Mn: 0.01 to 0.6 wt%, and a cast structure refining agent of 0.10 wt% or less, respectively, and a specific composition consisting of the balance Al and inevitable impurities Proposed aluminum alloy sheets with excellent warm formability, with a solid solution amount of Fe and Mn in aluminum alloy sheets below a specified value and a high tensile elongation of 65% or higher at a warm working temperature range of 200 to 300 ° C (See Patent Document 3).

Furthermore, the two Al plates sandwiching the resin are fixed in advance with a solder material containing Al, and the warming of the vibration-damping Al plate that prevents the displacement of the resin by heating as much as possible and prevents the plate displacement. Molding has also been proposed (see Patent Documents 4 and 5).
JP-A-4-72030 (Claims) JP-A-7-310137 (Claims) JP 2002-348625 A (Claims) Japanese Patent Application Laid-Open No. 11-221876 (Claims) JP 2000-317534 A (Claims)

  However, there have been few proposals for warm forming of 6000 series Al alloy sheets. Further, for example, even if the high temperature characteristics such as the tensile elongation in the warm working temperature range of 200 to 300 ° C. of the aluminum alloy plate for warm forming are increased as in Patent Document 1, Al—Mg—Si In the 6000 series Al alloy sheet, the warm formability is not always improved.

  That is, if the alloy system is different, the mechanism for improving the warm formability is different, and naturally the means for improving the warm formability is also different. In other words, the means for improving the warm formability of the 6000 series Al alloy sheet has not always been clear so far.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a 6000 series Al alloy plate with improved warm formability.

In order to achieve this object, the gist of the aluminum alloy sheet for warm forming of the present invention is that the Al-Mg-Si alloy sheet contains 0.25 to 1.25 in terms of the content of Si and Mg corresponding to the Mg ₂ Si composition. The deviation of the content of Si and Mg from the Mg ₂ Si balance is in the range of ± 0.5 at% or less, each consisting of the remaining aluminum and unavoidable impurities. The local elongation at 200 to 300 ° C. is 20% or more, and the ratio of the local elongation to the total elongation is 60% or more.

  In the aluminum alloy plate for warm forming according to the present invention, in order to ensure improvement in warm formability, the aluminum alloy plate contains Si: 0.30 to 1.8%, Mg: 0.45 to 2.6% by mass, Fe: 1.0% or less, Ti: 0.05% or less, Mn: 1.0% or less, Cr: 0.3% or less, Zr: 0.3% or less, V: 0.3% or less, Cu: 1.0% or less, Zn = 1.0% It is preferable that the following contents are allowed, and the remaining aluminum and unavoidable impurities are included.

  Furthermore, in the warm forming method of the present invention, when the aluminum alloy plate of the above-described gist or the preferred embodiment described later is warm formed, the flange portion of the aluminum alloy plate is heated to a relatively high temperature of 150 to 400 ° C. The punched portion of the alloy plate is pressed at a relatively low temperature of 100 ° C. or lower.

  In warm forming, the punch (bottom) portion is formed at a relatively low temperature and the die portion is formed at a relatively high temperature. In terms of the material of the aluminum alloy plate, the flange portion of the plate (the plate portion sandwiched between the peripheral edge portion of the die and the plate pressing portion) is relatively hot, while the punched portion of the plate is relatively cold. Become.

  In warm forming, the reason for making the punched portion of the plate relatively low is that the punched portion of the plate is a load-bearing portion (particularly the abutting portion with the punch bottom) of the punch and has a high breaking strength. This is because it is better.

  On the other hand, the reason why the flange portion (die portion) of the plate is set to a relatively high temperature is because the plate deforms and the material flows into the die at the flange portion of the plate. This is because it is necessary to lower the deformation resistance and the maximum value of the material flow resistance.

  Therefore, the punched portion of the aluminum alloy plate is first heated as a flange portion of the plate to lower the deformation resistance, and after the maximum value of the material flow resistance is lowered, the punched portion of the plate is punched. As a contact portion with the bottom portion, it is cooled and the breaking strength is increased.

  Therefore, in terms of material, the punched portion of the aluminum alloy plate has a low flow stress when heated as a flange portion of the plate, and has a breaking strength when cooled as a contact portion with the punch bottom. Higher is better. That is, the moldability is better when the difference between the breaking strength when cooled and the flow stress when heated is larger.

In the present invention, this property is achieved by the balance between the contents of Si and Mg. That is, Si and Mg contained are in the range of 0.25 to 1.25 at% in terms of the content equivalent to the Mg ₂ Si composition, and the deviation of the Si and Mg content from the Mg ₂ Si balance is ± 0.5 at% respectively. The following range. As a result, the local elongation at 200 to 300 ° C. can be 20% or more and the ratio of the local elongation to the total elongation can be 60% or more as a characteristic of the plate, thereby improving warm formability. .

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

(Aluminum alloy plate warm characteristics)
In order to improve the warm formability, the aluminum alloy plate for warm forming of the present invention must have a certain degree of elongation and ductility as a premise. This is because in actual warm forming, it becomes difficult for the material to flow in due to frictional resistance or the like, and a deformed portion that requires an overhanging element occurs. For this reason, in order to have good warm formability, “a certain degree” of elongation, ductility, and strength are required.

  Therefore, in the present invention, as the characteristics of the Al-Mg-Si alloy plate, the local elongation at 200 to 300 ° C. is 20% or more, and the ratio of the local elongation to the total elongation is 60% or more. To do. If the local elongation is less than 20%, and if the ratio of the local elongation to the total elongation is less than 60%, the moldability of the material is too low and the warm formability is not improved.

  In the measurement of the local elongation and the total elongation, the test material temperature in the tensile test is set to 200 to 300 ° C. Of course, although the local elongation and the total elongation vary depending on the material temperature, the temperature range of 200 to 300 ° C. indicates a temperature range widely used in warm forming. In the present invention, since it is desired to define the elongation in this widely used temperature range, it is defined in a temperature range of 200 to 300 ° C.

(Al alloy composition)
In order to achieve the ratio of the local elongation and the total elongation and improve the warm formability, in the Al-Mg-Si based alloy sheet of the present invention, the composition balance of Si and Mg contained is important. In this regard, in the present invention, the Si and Mg contained in the Al-Mg-Si based alloy sheet are in the range of 0.25 to 1.25 at% in terms of the content equivalent to the Mg ₂ Si composition, and the content of these Si and Mg Deviations from the Mg ₂ Si balance are each in the range of 0.5 at% or less and consist of the balance aluminum and inevitable impurities.

FIG. 1 shows the range of 0.25 to 1.25 at% in the content equivalent to the Mg ₂ Si composition specified by the present invention, and the deviation of the Si and Mg content from the Mg ₂ Si balance is 0.5 at% or less. The range is indicated by the relationship between the Si content (at%) on the vertical axis and the Mg content (at%) on the horizontal axis.

  Due to the compositional balance of Si and Mg contained in these materials, the part to be punched of the aluminum alloy plate has a low flow stress when heated as a flange part of the plate, and the contact part with the bottom of the punch As a result, the breaking strength when cooled is increased. That is, the difference between the breaking strength when cooled and the flow stress when heated becomes a characteristic, and the warm formability is improved.

(Content equivalent to Mg ₂ Si composition)
If the content of Si and Mg is less than 0.25 at% in the content equivalent to the Mg ₂ Si composition, the solid solution of Mg and Si cannot be secured, the local elongation is lowered, and the warm formability is lowered. Moreover, the strength after molding also decreases. On the other hand, when the content of Si and Mg exceeds 1.0 at% in the content equivalent to the Mg ₂ Si composition, coarse Mg ₂ Si or simple substance Si precipitates, and this is the starting point of the fracture. Elongation becomes low and warm formability decreases. Therefore, Si and Mg contained in the Al—Mg—Si based alloy plate are in the range of 0.25 to 1.25 at% in terms of the content equivalent to the Mg ₂ Si composition.

(Deviation of Si and Mg content from Mg ₂ Si balance)
When the deviation of the Si and Mg content from the Mg ₂ Si balance deviates beyond the range of 0.5 at% for either Si or Mg, the warm formability decreases.

If the Si content is too low, or the Mg content is too high, and the deviation from the Mg ₂ Si balance exceeds 0.5 at%, the amount of Si in solid solution cannot be secured and the local elongation becomes low. , Warm formability decreases. In addition, the strength after warm forming also decreases.

On the other hand, if the Si content is too high, or the Mg content is too low and the deviation from the Mg ₂ Si balance exceeds 0.5 at%, the solid solution Mg content cannot be secured, and In addition, the amount of precipitation of coarse single-body Si increases, which becomes a starting point of fracture, again, the local elongation is lowered, and the warm formability is lowered.

Therefore, the deviation from the Mg ₂ Si balance of the contents of Si and Mg contained in the Al—Mg—Si based alloy sheet is set to a range of 0.5 at% or less.

(Remainder composition)
In the Al-Mg-Si alloy sheet of the present invention, the balance composition is the balance composition in order to guarantee the achievement of the ratio to the local elongation and the total elongation by the composition balance of Si and Mg contained, and to improve the warm formability. Basically, it consists of aluminum and inevitable impurities.

  As this unavoidable impurity, Fe, Ti, Mn, Cr, Zr, V, Cu, Zn or other elements are added as long as they do not impair the properties required for warm formability and automotive material panels described later. Allow to include. Other alloy elements and gas components other than these alloy elements are also 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. When these are melted, these other elements are necessarily included. For this reason, in the present invention, as described above, these impurity elements are allowed to be contained in an amount that does not inhibit the intended effect of the present invention.

(Composition for automotive panel materials)
On the other hand, in the Al-Mg-Si based 6000 series Al alloy plate targeted by the present invention, for the above-mentioned automobile panel materials, etc., in addition to the warm formability that is the main purpose, excellent bending workability, BH Various properties such as (bake hard) property, strength, weldability and corrosion resistance are required. In order to guarantee such various properties and warm formability, it is preferable to further define the content ranges of Si and Mg and to define the allowable amounts of other elements.

  As such a composition, specifically, the aluminum alloy plate for warm forming of the present invention contains, by mass%, Si: 0.30 to 1.8%, Mg: 0.45 to 2.6%, and other elements, Fe: 1.0 % Or less, Ti: 0.05% or less, Mn: 1.0% or less, Cr: 0.3% or less, Zr: 0.3% or less, V: 0.3% or less, Cu: 1.0% or less, and Zn = 1.0% or less are allowed. It preferably consists of the balance aluminum and inevitable impurities. The above other elements are basically impurities, but when scrap is used in large quantities as a melting raw material in addition to metal, there is a high possibility that these elements are mixed. And, for example, reducing these to below the detection limit itself increases costs, and a certain amount of allowance is required. Moreover, even if it contains a substantial amount, there is a content range that does not hinder the object and effect of the present invention, and within this range, there is also each content effect. Therefore, it is allowed to be contained within a range not exceeding the above specified amounts.

Si: 0.30 to 1.8%.
Si, together with Mg, exhibits aging hardening ability by forming aging precipitates that contribute to strength improvement during the above-mentioned low temperature and short time artificial aging treatment such as paint baking treatment for automotive panel materials, etc. To do. Thereby, for example, the strength (proof strength) required for an outer panel of an automobile can be obtained, and various characteristics such as press formability and hem (bending) workability can be provided.

  When the Si content is less than 0.30%, the age-hardening ability, press formability and the like are lowered. On the other hand, when Si exceeds 1.8%, hemmability and press formability deteriorate. Furthermore, weldability is significantly impaired.

Mg: 0.45 to 2.6%.
Mg is used for automobile panel materials, etc., during the artificial aging treatment such as solid solution strengthening and paint baking treatment, forms an aging precipitate that contributes to strength improvement together with Si, and exhibits age hardening ability. Obtains the required strength for the outer panel.

  If the Mg content is less than 0.45%, 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 proof stress required as a motor vehicle outer panel cannot be obtained. On the other hand, if the Mg content exceeds 2.6%, the hem bending workability and press formability are deteriorated.

Cu: 1.0% or less
Cu has the effect of facilitating the formation of aging precipitates that contribute to the improvement of strength in the crystal grains of the Al alloy material structure under the conditions of the artificial aging treatment at a low temperature for a short time and easily obtaining high proof stress. Further, solid solution Cu has an effect of improving formability. However, Cu reduces corrosion resistance. For this reason, Cu is allowed to contain 1.0% or less.

Mn: 1.0% or less, Cr: 0.3% or less, Zr: 0.3% or less, V: 1.0% or less For these transition elements, dispersed particles (dispersed phase) are generated during the homogenization heat treatment. Since there is an effect of hindering grain boundary movement after recrystallization, there is an effect that fine crystal grains can be obtained. However, they easily form coarse Al—Fe—Si— (Mn, Cr, Zr) -based intermetallic compounds and crystal precipitates during melting and casting, and lower the mechanical properties of the Al alloy sheet. Moreover, bending workability and flat hem workability are also reduced. Therefore, it is allowed to contain Mn: 1.0% or less, Cr: 0.3% or less, Zr: 0.3% or less, and V: 1.0% or less.

Ti: 0.05% or less
Ti has the effect of refining ingot crystal grains. However, Ti forms a coarse crystallized product and reduces formability. Therefore, Ti is allowed to be contained up to 0.05% or less.

Fe: 1.0% or less Fe mixed as an impurity and contained as an impurity produces a crystallized product, serves as a nucleus of recrystallized grains, and has an effect of preventing coarsening of crystal grains to make fine grains. However, these crystallized materials deteriorate fracture toughness and fatigue properties, as well as bending workability, flat hem workability, and press formability. For this reason, the content of Fe up to 1.0% is allowed.

Zn: 1.0% or less
Zn decreases the corrosion resistance. For this reason, Zn is allowed to contain up to 1.0%.

(Production method)
Next, a method for producing the Al alloy plate of the present invention will be described below. The aluminum alloy plate referred to in the present invention may be a plate-like aluminum alloy produced by rolling, extrusion, forging, casting, or the like, or an aluminum alloy that has been subjected to tempering treatment such as solution treatment and quenching treatment. Among these, a representative method for producing a rolled sheet will be described below.

  In the method for producing a rolled plate, the Al alloy ingot having the above composition is subjected to homogenization heat treatment, hot rolling, and further cold rolling, followed by solution treatment and quenching treatment. It is. However, in order to combine hem bendability and bake hardness, there are preferable manufacturing process conditions such as particularly controlling the homogenization heat treatment conditions and the pre-aging treatment conditions after solution treatment and quenching treatment.

(Melting, casting)
First, in the melting and casting process, a normal melt casting method such as a continuous casting rolling method and a semi-continuous casting method (DC casting method) is appropriately selected for the molten Al alloy melt adjusted within the above-mentioned 6000 component standard range. And cast.

(Homogenization heat treatment)
Next, the cast Al alloy ingot is subjected to homogenization heat treatment. The temperature of the homogenization heat treatment itself is appropriately selected as a homogenization temperature of 450 ° C. or higher and a temperature lower than the melting point. The purpose of this homogenization heat treatment is to homogenize the structure, that is, to eliminate segregation in the crystal grains in the ingot structure.

  If the heat treatment temperature is lower than 450 ° C, intragranular segregation in the ingot cannot be sufficiently eliminated, sufficient strength cannot be obtained, and it acts as a starting point for fracture, so press formability and hem bendability Deteriorates. The homogenization heat treatment time is preferably selected from the range of 0.5 to 6 hours depending on the thickness of the ingot. If the homogenization heat treatment time is too short, intragranular segregation of the ingot cannot be sufficiently eliminated, and this may act as a starting point for fracture.

(Hot rolling)
In the present invention, there are no particular restrictions on the hot rolling conditions, but preferably a lower hot rolling start temperature suppresses precipitation promotion and precipitate coarsening during hot rolling, and formation of coarse recrystallized grains. Is suppressed and strength and formability are not deteriorated. Preferably it is 500 ° C. or lower, more preferably 400 ° C. or lower, and the lower limit is preferably 250 ° C. or higher, more preferably 300 ° C. or higher. When the temperature is higher than this, the precipitates become coarse, and recrystallization occurs, and coarse recrystallized grains are generated during hot rolling, thereby reducing strength and formability. Further, when the hot rolling start temperature is less than 250 ° C., the hot rolling itself becomes difficult.

(Hot rolled sheet annealing)
The hot rolled sheet is annealed (roughened) before cold rolling as necessary. It may be omitted for the sake of manufacturing efficiency and reduction of manufacturing cost, and cold rolling may be performed without pre-annealing the hot-rolled sheet.

(Cold rolling)
Cold rolling after hot rolling is performed to produce cold rolled sheets (including coils) with a desired thickness.

(Solution and quenching)
The conditions for the solution treatment are preferably 500 ° C. or higher and the melting point or lower in order to sufficiently precipitate the aging precipitates that contribute to the improvement of strength by precipitation by the subsequent low-temperature and short-time artificial age hardening treatment. In the temperature range.

In the subsequent quenching treatment from the solution treatment temperature, if the cooling rate is slow, Si, Mg ₂ Si, etc. are likely to precipitate on the grain boundary, which tends to be the starting point of cracks during press molding and bending, and these formability descend. In order to ensure this cooling rate, the quenching process should be performed by selecting and using water cooling means and conditions such as forced air cooling with a fan, mist, spraying, immersion, etc., respectively, and quenching at a rate of 100 ° C / min or more. preferable.

  In the present invention, in order to enhance age-hardening in an artificial age-hardening treatment such as a paint baking process of a molded panel, in order to suppress the formation of clusters after solution hardening and to promote the precipitation of GP zone, pre-aging It may be processed. This preliminary aging treatment is preferably maintained in a temperature range of 50 to 140 ° C. for a required time of 1 to 24 hours.

  As the preliminary aging treatment, the quenching end temperature after the solution treatment is increased to 50 to 140 ° C., and then immediately reheated or kept as it is. Alternatively, it is immediately reheated to 50 to 140 ° C. after quenching to room temperature after solution treatment. Further, in the case of continuous solution quenching, the quenching process is completed within the temperature range of the preliminary aging, and the coil is wound around a coil at the same high temperature. In addition, you may reheat before winding up to a coil, and you may heat-retain after winding. Moreover, after the quenching process to room temperature, it may be reheated to the above temperature range and wound at a high temperature.

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

(Warm forming method)
Next, a preferred warm forming method to which the 6000 series Al alloy plate of the present invention is applied will be described below.
The 6000 series Al alloy plate of the present invention can be applied to press forming at various warm temperatures such as deep drawing and overhanging. In other words, as the warm forming method itself, normal press forming such as deep drawing and overhanging can be applied. Moreover, the press apparatus used with these warm forming methods can also apply a normal warm forming press.

  Press forming intended for deep drawing will be described with reference to a cross-sectional view of the press forming machine in FIG. In FIG. 2, 1 is a 6000 series aluminum alloy plate to be formed, 5 is a punch, 6 is a die (die), and 7 is a plate retainer. Reference numeral 2 denotes a flange portion around the plate 1 sandwiched between the plate presser 7 and a die (die) 6, 3 denotes a cylindrical wall portion of the cylindrical molded product that flows into the die 6 of the plate 1, and 4 denotes a punch 5. It is the cylinder bottom part of the cylindrical molded product shape | molded by contact | abutting to the bottom part of (no load).

  Here, as a preferable warm forming method, the flange portion 2 of the plate 1 is set to a relatively high temperature of 150 to 400 ° C. so that the flange portion 2 of the plate 1 can easily flow into the die 6. For this purpose, the flange part 2 of the plate 1 is heated. In this heating method, the entire plate or only the flange portion 2 of the plate 1 is heated in advance using a heater, a furnace or the like before being introduced into the press, or the die 6 and / or the plate presser 7 shown in the figure is used. It heats with the heater 8 etc., and the flange part 2 around the board 1 is partially heated after introducing into a press.

  In the present invention, as described above, the punched portion of the Al alloy plate is heated as a flange portion of the plate due to the composition balance between Si and Mg contained in the 6000 series Al alloy plate that is warm-formed. The flow stress is low, and the breaking strength when cooled as a contact portion with the punch bottom is increased. That is, the difference between the breaking strength when cooled and the flow stress when heated is large, and the warm formability is improved.

  However, the heating temperature is preferably 150 ° C. or higher. If the heating temperature is less than 150 ° C., the heating temperature is too low, which is no different from normal room temperature forming, and even the 6000 series Al alloy sheet of the present invention impairs the advantages of warm forming itself.

  On the other hand, when the heating temperature exceeds 400 ° C., the temperature is too high, and even the 6000 series Al alloy plate of the present invention may cause the amount of material flowing into the die 6 to be too large. I am prone to wrinkles.

  On the other hand, as the portion to be punched of the plate 1, the corner portion of the plate 3 that contacts the corner portion of the punch 5 and the portion of the plate 4 that contacts the bottom portion of the punch 5, Use a relatively low temperature of ℃ or less.

  For this purpose, it is necessary to cool the heated plate, and the bottom of the punch 5 is cooled to a relatively low temperature of 100 ° C. or less by circulating water or the like. The lower limit temperature of 100 ° C. or less is about room temperature although it depends on the cooling ability of the plate 4 by the punch 5.

  However, when this temperature exceeds 100 ° C., even in the 6000 series Al alloy plate of the present invention, the corner portion of the plate 3 that contacts the corner portion of the punch 5 and the portion of the plate 4 that contacts the bottom portion of the punch 5 The breaking strength of the sheet becomes low, and the possibility of cracking during the molding increases.

  Warm formability is further improved by such a warm forming condition and a composition balance between Si and Mg contained in the 6000 series Al alloy plate of the present invention.

  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. 6000 series Al alloy plates having each composition of 1 to 9 (invention example) and 10 to 16 (comparative example) shown in Table 1 and a composition balance of Si and Mg were produced, each of which was warm-formed, The moldability was evaluated.

  More specific common production conditions for each test material Al alloy plate are as follows. An ingot of 500 mm thickness, 2000 mm width, and 7 m length of each composition shown in Table 1 was melted by a DC casting method and then subjected to a homogenization heat treatment at 480 ° C. × 2 hours. After this homogenization heat treatment, hot rolling was performed at a start temperature of 390 ° C. and an end temperature of 280 ° C. to a thickness of 2.5 mmt. The hot-rolled sheet was subjected to direct cold rolling after omitting the roughening to obtain a cold-rolled sheet coil having a thickness of 1.0 mmt. The plate coil was subjected to a solution quenching process at 550 ° C. for several seconds in a continuous furnace, followed by a water quenching process for cooling to room temperature at a cooling rate of 300 ° C./min. Immediately thereafter, a series of tempering treatments were carried out, such as reheating to a temperature of 70 ° C. and maintaining in this temperature range for 2 hours.

(Test plate tensile properties)
A test plate (blank) was cut out from each plate after tempering, and the mechanical warming properties (As characteristics) of the plates at 300 ° C were investigated and evaluated. Table 2 shows the results of local elongation (%), total elongation (%), (local elongation / total elongation) × 100 (%) of the plate at 300 ° C.

  Specifically, the tensile test was performed by taking a JIS Z2201 No. 5 test piece (width 25 mm x gauge distance 50 mm x plate thickness) perpendicular to the rolling direction from the tempered plate and heating it to 300 ° C. A tensile test was performed. This tensile test was based on JIS Z2241 (1980) (metal material tensile test method). The crosshead speed was 5 mm / min, and the test piece was run at a constant speed until the test piece broke.

(Sample plate formability)
Further, a test plate (blank) was cut out from the tempered plate, and the limit drawing ratio (LDR) was evaluated by a warm forming test using the press shown in FIG. These results are shown in Table 2, respectively.

  At this time, the temperature conditions for warm forming by the press shown in FIG. That is, the flange portion 2 of the plate 1 was heated to 260 ° C. using the heater 8. Moreover, the bottom part of the punch 5 is cooled with circulating water, and the corner part of the plate 3 in contact with the corner part of the punch 5 and the part of the plate 4 in contact with the bottom part of the punch 5 are set to a relatively low temperature of 100 ° C. or less. . These temperatures were measured with a contact-type thermometer and used as an average temperature in a plurality of measurements within a predetermined measurement time.

The limit drawing ratio (LDR) was determined by punching test pieces of various diameters from the test plate, punch: 50mmφ-shoulder R4.5mm, die: 54.5-56.0mmφ-shoulder R8-10mm, Nippon Tool Oil A deep drawing test was carried out using a lubricant CF853 manufactured under the conditions of a wrinkle holding load of 0.8 kg / cm ² and a punch speed of 20 mm / min. And the shaping | molding limit blank diameter which cannot be deep-drawn was determined, and the limit drawing ratio was computed by the following formula | equation. Limit drawing ratio = forming limit blank diameter / punch diameter. The larger the limit drawing ratio, the better the deep drawing formability. For example, in order to satisfy the deep drawing formability required for forming an automobile panel, it may be 2.4 or more.

Inventive Examples 1 to 9 use alloys having respective compositions shown in Table 1, and as shown in Table 2, each Al-Mg-Si alloy plate contains Si and Mg in a content equivalent to Mg ₂ Si composition of 0.25. The deviation of the content of Si and Mg from the Mg ₂ Si balance is in the range of ± 0.5 at% or less, and the balance is aluminum and inevitable impurities. Further, as a characteristic of the plate, the local elongation at 300 ° C. is 20% or more, and the ratio of the local elongation to the total elongation is 60% or more. As a result, as shown in Table 2, Invention Examples 1 to 9 have excellent warm formability.

On the other hand, as shown in Table 2, each of the Al-Mg-Si-based alloy plates in Comparative Examples 10-13, 17, and 18 satisfies the preferable content ranges of Si and Mg, The content of Si and Mg is within the range of 0.25 to 1.25 at% corresponding to the Mg ₂ Si composition, or the deviation of the Si and Mg content from the Mg ₂ Si balance is out of the range of 0.5 at% or less. .

  As a result, in Comparative Examples 10 to 13, 17, and 18, the local elongation at 300 ° C. is less than 20%, and the ratio of the local elongation to the total elongation is less than 60%. As a result, as shown in Table 2, Comparative Examples 10 to 13, 17, and 18 have poor warm formability.

Further, as shown in Table 2, in Comparative Examples 14 to 16, each Al—Mg—Si based alloy plate has Si and Mg within the content range corresponding to the Mg ₂ Si composition, and the deviation from the Mg ₂ Si balance. Is within the range. However, as shown in Table 1, Comparative Example 14 contains too much Mn, Comparative Example 15 contains Cr, and Comparative Example 16 contains too much Zr. As a result, as shown in Table 2, the comparative examples 14 to 16 are similarly inferior in warm formability.

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

  ADVANTAGE OF THE INVENTION According to this invention, the 6000 series Al alloy plate which improved warm formability, and its warm forming method can be provided. As a result, the application of the 6000 series aluminum alloy plate can be expanded to press forming applications such as automobile panels.

The Mg ₂ Si composition range of the balance to which the present invention is defined is an explanatory diagram showing. It is sectional drawing which shows warm forming of an aluminum alloy plate.

Explanation of symbols

1: plate, 2: plate flange, 3: plate wall, 4: plate bottom (contact portion with punch),
5: Punch, 6: Die (mold), 7: Plate holder

Claims (3)

The Al-Mg-Si alloy plate contains Si and Mg in the range of 0.25 to 1.25 at% in terms of the content equivalent to the Mg ₂ Si composition. From the Mg ₂ Si balance of the content of these Si and Mg The deviation of each is within ± 0.5 at%, consisting of the balance aluminum and inevitable impurities. The characteristic of this plate is that the local elongation at 200-300 ° C is 20% or more and the total elongation of this local elongation is The aluminum alloy plate for warm forming, characterized in that the ratio to is 60% or more.   The aluminum alloy plate contains, by mass%, Si: 0.30 to 1.8%, Mg: 0.45 to 2.6%, Fe: 1.0% or less, Ti: 0.05% or less, Mn: 1.0% or less, Cr The temperature according to claim 1, comprising: 0.3% or less, Zr: 0.3% or less, V: 0.3% or less, Cu: 1.0% or less, and Zn = 1.0% or less, and is composed of the balance aluminum and inevitable impurities. Aluminum alloy sheet for hot forming.   When the aluminum alloy plate according to claim 1 or 2 is warm-formed, the flange portion of the aluminum alloy plate is set to a relatively high temperature of 150 to 400 ° C, while the punched portion of the aluminum alloy plate is set to 100 ° C. A warm forming method characterized by press forming at a relatively low temperature as follows.

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