JP2009242907A - Method for producing aluminum alloy blank for press forming - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Al-Mg-Si based aluminum alloy blank for press forming which has no need of preparing a special forming apparatus, has no generation of cracks and the generation of wrinkles upon press working, and can be stably press-formed while securing strength as the whole of a formed part. <P>SOLUTION: An Al-Mg-Si based aluminum alloy sheet which has been subjected to solution treatment and quenching treatment is heat-treated at 180 to 250°C for 3 to 20 h, and is thereafter cut into a prescribed shape, so as to be an aluminum alloy blank 1, and only the working schedule part 2 of the blank 1 is subjected to instantaneous heating at 480 to 550°C for 0.5 to 10 s. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for producing a blank material made of an Al—Mg—Si based aluminum alloy used when press-molding a large panel such as a panel for an automobile.

  In recent years, automobiles have a tendency to increase in body weight with each model change due to the background of improvement in safety and enhancement of comfort equipment, which causes deterioration of fuel consumption. In addition, in the body field of the entire transportation equipment including automobiles, improvement of fuel efficiency by pursuing light weight is pursued for global environmental problems caused by exhaust gas and the like. Therefore, instead of the steel plate conventionally used for the body of a transport machine such as an automobile, a lighter aluminum alloy plate is adopted as a rolled plate or extrusion mold material used for the body of a transport machine such as an automobile. A lot is happening.

  Of these, Al-Mg-Si based aluminum alloy plates are being considered for panels such as outer panels (outer plates) and inner panels (inner plates) such as automobile hoods, fenders, doors, roofs, and trunk lids. Has been.

  The Al—Mg—Si based aluminum alloy plate exhibits high strength by solid solution of Mg and Si as main additive elements by solution treatment and precipitation by aging treatment at about 170 to 200 ° C. performed thereafter. When using Al-Mg-Si-based aluminum alloy sheets as automotive panel materials, high-strength parts are formed by press-molding in a state of high elongation immediately after solution forming, and the subsequent baking treatment also serves as an aging treatment. Can be obtained.

  However, aluminum alloy sheets have poor ductility and inferior formability compared to steel sheets. Therefore, even if it is going to press-mold on the completely same conditions as a steel plate, a crack may generate | occur | produce at the time of press molding in a difficult-to-form part. Further, if the wrinkle holding force is lowered in order to avoid the occurrence of cracks, wrinkles will be generated this time.

  In particular, Al-Mg-Si-based aluminum alloy sheets are aged at room temperature and increase in strength, so cracks and wrinkles are more likely to occur during press forming than other aluminum alloy sheets. This makes it difficult to press-form Al—Mg—Si based aluminum alloy sheets.

  In the past, in order to improve the formability of the Al—Mg—Si based aluminum alloy plate itself, alloy elements other than Mg and Si have been added, or in addition to the addition of these alloy elements, the crystal grain size, Various metallurgical improvements such as controlling the microstructure of precipitate dispersion and grain boundary precipitates have been attempted.

  On the other hand, many proposals for improving the formability of an aluminum alloy plate have been made from the processing side of press forming. In Patent Document 1, a temperature of 50 to 150 ° C. is applied to a 6000 series aluminum alloy material (Al—Mg—Si based aluminum alloy material) that has undergone age hardening at room temperature (normal temperature) after being subjected to a work strain of 1% or more. Proposals have been made to perform molding such as hem processing by performing a recovery process of heating the steel.

  In Patent Documents 2 to 7, proposals have been made to improve the formability of an aluminum alloy plate by making some improvements to the press forming apparatus itself. Patent Document 2 describes a technique for heating a blank flange portion during molding by heating a plate presser and a die for sandwiching the flange portion of the blank with respective heaters. In Patent Document 3, the end face of a punch that is affected by heating while holding a plate material with a wrinkle presser provided with an electric heater inside and a die provided with an electric heater inside, and heating the holding portion at the same time. Describes a technique for cooling a portion of a plate material in contact with a cooling gas from a cooling air supply device provided on the opposite side of the punch. In Patent Document 4, the end face of a punch that is affected by heating while sandwiching a plate material with a wrinkle presser provided with an electric heater inside and a die provided with an electric heater inside, and simultaneously heating the holding portion. Describes a technique for cooling a portion of a plate material in contact with a non-oxidizing gas blown from a non-oxidizing gas supply device provided on the opposite side of the punch.

  In addition, in Patent Document 5, a heating medium such as an electric heater is installed in the attachment portion of the die and / or the plate presser, and a cooling medium such as cooling water is refluxed by drilling a through passage in the punch. A technique for deep drawing a thin metal plate using a plate press and a punch is described. In Patent Document 6, as a technology related to warm press working for a 5000 series aluminum alloy, an aluminum alloy plate is warm-formed with a die embedded with a heater and a wrinkle holding metal fitting, and a punch embedded with piping for circulating a refrigerant. The technology to do is described. Patent Document 7 discloses a technique for warm forming an aluminum alloy plate using a forming apparatus having a punch, a die and a wrinkle presser with a built-in heater as a technique related to warm forming for a 6000 series aluminum alloy. Is described.

  However, in these techniques, there is a possibility that even a portion other than the blank processing scheduled portion may be heated to a high temperature due to heat transfer, and a temperature control device such as a heater is built in the press forming device itself. However, conventional molding apparatuses cannot be used, and there are various problems such as the necessity of preparing a special molding apparatus separately, and this cannot always be said to be an effective solution.

Japanese Patent Laid-Open No. 2005-240083 JP-A-4-351229 JP-A-5-237558 JP-A-5-309425 Japanese Patent Laid-Open No. 11-309518 JP 2007-125601 A JP 2006-205244 A

  The present invention was made as a solution to the above-described conventional problems, and it is not necessary to prepare a special molding device by applying instantaneous heating only to the processing scheduled portion of the blank material used for press molding, In addition, there is no generation of cracks or wrinkles during pressing, and Al-Mg-Si aluminum alloys for press forming that can be stably pressed while maintaining the strength of the entire molded product. It is an object to provide a blank material.

  According to the first aspect of the present invention, the Al—Mg—Si based aluminum alloy plate that has undergone solution treatment and quenching treatment is subjected to heat treatment at 180 to 250 ° C. for 3 to 20 hours, and then cut into a predetermined shape. An aluminum alloy blank material for press forming, which is an aluminum alloy blank material, and is subjected to instantaneous heating for 0.5 to 10 seconds at a temperature of 480 to 550 ° C. only on a planned processing portion of the blank material. It is a manufacturing method.

  According to a second aspect of the present invention, the difference in strength between the tensile strength of the part to be processed of the blank material subjected to instantaneous heating and the tensile strength of the other base material part of the blank material is more than 80 MPa and not more than 140 MPa. Item 2. A method for producing an aluminum alloy blank for press forming according to Item 1.

  According to the manufacturing method of the aluminum alloy blank material for press forming of the present invention, it is not necessary to prepare a special forming device by applying instantaneous heating only to the processing planned portion of the blank material used for press forming, In addition, there is no generation of cracks or wrinkles during pressing, and Al-Mg-Si aluminum alloys for press forming that can be stably pressed while maintaining the strength of the entire molded product. A blank material can be manufactured.

  In addition, by setting the difference in tensile strength between the blank portion subjected to instantaneous heating and the tensile strength of other portions of the blank material to be more than 80 MPa and 140 MPa or less, occurrence of cracks during press working or There is no occurrence of wrinkles, and it is possible to produce an Al—Mg—Si based aluminum alloy blank for press forming that can be stably pressed while ensuring the strength of the entire molded product. The effect can be achieved more reliably.

  Hereinafter, the present invention will be described in more detail based on embodiments.

  The main point of the present invention is that, in order to sufficiently improve the formability of an Al—Mg—Si-based aluminum alloy plate that is difficult to form, instantaneous heating is performed, so that the same aluminum alloy blank material is processed. That is, a difference in strength is provided between the tensile strength of the planned portion and the tensile strength of the other base material portions.

  The part to be processed indicates a part that is deformed by press molding. The part to be processed is instantaneously heated for 0.5 to 10 seconds at a temperature of 480 to 550 ° C. Without heating the material part), only the necessary part is heated to lower the tensile strength, making the part with relatively low proof stress, and making the other part (base material part) the part with relatively high proof stress.

  In the present invention, as described above, the strength of the entire molded product is ensured by mixing a portion having a relatively low yield strength and a location having a relatively high yield strength in the same single aluminum alloy blank. In addition, there is no generation of cracks or wrinkles during pressing, and stable press molding can be performed.

  In addition, it can respond | correspond to press molding of various shapes by adjusting the site | part and area which are heated instantaneously.

  The aluminum alloy used in the method for producing an aluminum alloy blank for press forming according to the present invention is an Al—Mg—Si aluminum alloy. The component composition of this Al—Mg—Si-based aluminum alloy is not particularly limited, but a more preferable component range is exemplified below.

  The Al—Mg—Si based aluminum alloy having a preferable component range contains, for example, Mg: 0.2 to 1.2 mass%, Si: 0.4 to 2.0 mass%, with the balance being Al and inevitable impurities. Al-Mg-Si-based aluminum alloy or Mg: 0.2-1.2% by mass, Si: 0.4-2.0% by mass, Cu: 0.1-1.0% by mass The balance is an Al—Mg—Si—Cu based aluminum alloy consisting of Al and inevitable impurities.

  Mg is an element that contributes to the strength and formability together with Si. If it is less than 0.2% by mass, the strength is not always sufficient, and the formability is poor. On the other hand, if it exceeds 1.2% by mass, rolling becomes difficult and the formability decreases. Therefore, the Mg content is preferably 0.2 to 1.2% by mass.

  Si is an element that contributes to strength and formability together with Mg. If it is less than 0.4% by mass, the strength is not always sufficient, and the formability is poor. On the other hand, if it exceeds 2.0 mass%, molding becomes difficult due to crystallization of coarse Si alone. Therefore, the Si content is preferably 0.4 to 2.0 mass%.

  In the present invention, by using an Al—Mg—Si-based aluminum alloy containing Mg and Si as main additive elements, a sufficient effect can be obtained. However, in order to improve formability, Mg and In addition to Si, an Al—Mg—Si—Cu-based aluminum alloy containing Cu as a main additive element can also be used.

  In this Al—Mg—Si—Cu-based aluminum alloy, if the Cu content is less than 0.1% by mass, formability becomes insufficient. On the other hand, if it exceeds 1.0% by mass, the corrosion resistance, particularly the yarn rust resistance, is significantly reduced. Therefore, the content of Cu is preferably 0.1 to 1.0% by mass.

  In producing an aluminum alloy blank for press forming according to the practice of the present invention with an aluminum alloy plate made of an Al-Mg-Si-based aluminum alloy having the above-described composition range, until the solution treatment and quenching treatment, Can be produced by a conventional method known from US Pat. The ordinary method is a process of melting / casting → homogenization treatment → hot rolling → cold rolling, in which an Al—Mg—Si-based aluminum alloy sheet is made a predetermined thickness, and then a continuous annealing furnace or heat treatment furnace In this method, solution treatment is performed using a salt bath or the like, and further, quenching is performed with water (including mist) or air, and then left at room temperature to obtain T4 refining. If necessary, intermediate annealing may be included between hot rolling and cold rolling.

  So far, the Al—Mg—Si-based aluminum alloy plate used when press-molding large panels such as automobile panels is this T4 tempered material. This T4 tempered material has improved material strength (yield strength) when allowed to stand at room temperature and has reduced elongation, which causes a decrease in formability and bendability.

  Therefore, in the present invention, first, the Al-Mg-Si aluminum alloy plate in the T4 tempered state is subjected to a heat treatment at 180 to 250 ° C for 3 to 20 hours to obtain a T6 temper (peak aging treatment). Alternatively, T7 tempering (overaging treatment) is performed.

  In this heat treatment (aging treatment), when the heat treatment temperature is lower than 180 ° C., high strength cannot be obtained, and it takes about several tens of days to obtain the strength, which is suitable for manufacturing industrial products. No. On the other hand, when the heat treatment temperature is higher than 250 ° C., it becomes an annealed state, and in this case, sufficient strength cannot be obtained. Therefore, the heat treatment temperature is 180 to 250 ° C.

  When the heat treatment time is shorter than 3 hours, sufficient strength cannot be obtained when heat treatment is performed at a relatively low temperature, and when heat treatment is performed at a relatively high temperature, an annealed state cannot be obtained and sufficient strength cannot be obtained. On the other hand, if the heat treatment time is longer than 20 hours, regardless of the heat treatment temperature, the treatment time becomes too long, and an annealing state is obtained and sufficient strength cannot be obtained. Therefore, the heat treatment time is 3 to 20 hours.

  Subsequent steps will be described with reference to FIG. First, it cuts into the predetermined shape from the state of Fig.1 (a), and it is set as the aluminum alloy blank material 1 shown in FIG.1 (b).

  With respect to the blank material 1 having a predetermined shape obtained by this cutting, instantaneous heating is performed only on a portion that is deformed by the next press forming, that is, only the planned processing portion 2. The processing planned portion 2 in the case of performing press forming in deep drawing is generally the entire peripheral portion 2a (flange portion) of the blank material. In addition, when a necessary part (local part 2b) in a part surrounded by the entire peripheral part 2a (flange part) is also required to be processed, that part is also designated as a planned processing part 2. The instantaneous heating temperature is 480 to 550 ° C., and the heating time is 0.5 to 10 seconds. Then, as shown in FIG.1 (c), by carrying out cooling and rapid cooling, only the process planned part 2 is made into the raw material intensity | strength of about T4 refining.

  In this instantaneous heating, when the heat treatment temperature is lower than 480 ° C., since it is instantaneous heating, sufficient heat treatment is not performed and the moldability is not improved. On the other hand, when the heat treatment temperature is higher than 550 ° C., the heat at the time of instantaneous heating is transmitted to the peripheral portion other than the processing scheduled portion 2, and the partial heat treatment cannot be performed, and high moldability cannot be obtained. Therefore, instantaneous heating temperature shall be 480-550 degreeC.

  On the other hand, if the instantaneous heating time is shorter than 0.5 seconds, the effect of the heat treatment is hardly obtained and the moldability is not improved. On the other hand, if the instantaneous heating time is longer than 10 seconds, the heat at the time of instantaneous heating is transmitted to the peripheral portion other than the processing scheduled portion 2, and partial heat treatment cannot be performed, and high moldability cannot be obtained. Therefore, the instantaneous heating time is 0.5 to 10 seconds.

  Moreover, the tensile strength (proof stress) of the base material part 3 (the part which has not been instantaneously heated while being T6 tempered or T7 tempered) of the aluminum alloy blank for press forming 1 manufactured by the above manufacturing method, and the instantaneous When the strength difference in the tensile strength (yield strength) of the heated processing target portion 2 is 80 MPa or less, the moldability is not sufficiently improved. On the other hand, when it exceeds 140 MPa, the tensile strength of the processing scheduled part 2 heated instantaneously becomes low, and a crack may occur. Therefore, the strength difference between the tensile strength (proof stress) between the base material portion 3 of the blank material 1 and the instantaneously heated processing portion 2 is set to be more than 80 MPa and 140 MPa or less.

  As described above, among the same blank material 1, in the press molding, the processing scheduled portion 2 accompanied by deformation is the soft portion, and the remaining base material portion 3 is the hard portion, so that the crack is generated during the press molding. As shown in FIG. 1 (d), it is possible to stably press-mold as shown in FIG.

  As shown in FIG. 2, when the blank material 1 is press-formed by deep drawing, the boundary between the soft portion and the hard portion in the blank material 1 is the vertical wall portion 1 a of the blank material 1. If it is on the flange 1b side that exceeds, the die shoulder R1c will be the starting point and cracking will occur. Conversely, if the boundary between the soft part and the hard part is closer to the center side of the blank 1 than the vertical wall part 1a, a crack occurs in the punch shoulder R1d. Therefore, when the blank material 1 is press-formed by deep drawing, the boundary between the soft portion and the hard portion in the blank material 1 may be in the middle of the vertical wall portion 1a, and the depth of the vertical wall portion 1a. It is desirable that it is about 1/2 of that.

  A 6000 series aluminum alloy (Al-1.0 mass% Mg-0.6 mass% Si) T4 tempered material for automobile panels having a plate thickness of 1.0 mm is processed at a processing temperature of 180 to 250 ° C. and a processing time of 3 to 20 hours. Based on this range, heat treatment (artificial aging treatment) is performed by varying the treatment temperature and treatment time, and then cut into the size shown in FIG. 3 (vertical 200 mm × width 200 mm square). It was.

  Furthermore, local heating was performed on the planned processing portion 2 on the entire circumference of the test material (blank material 1) shown in FIG. The local heating was performed by varying the processing temperature and processing time based on instantaneous heating at a processing temperature of 520 ° C. and a processing time of 5 seconds. Immediately after the local heating, the test material was water-cooled, and the locally heated processing scheduled portion 2 was T4, and the remaining base material portion 3 was in a state maintaining the strength of the artificial aging treatment. . (The comparative example does not have this intensity distribution.)

  At this time, regarding the strength of each part, the test material B in a state where heat treatment (artificial aging treatment) was performed, and the test material in a state where the test material B was further heated under the same conditions as the local heating JIS No. 5 test pieces were collected from the material C, respectively, and subjected to a tensile test using an Instron universal testing machine. Table 1 shows the difference in tensile strength between the test material B and the test material C obtained in this tensile test as a difference in yield strength.

  Further, a molding test of the specimen A was performed using a deep drawing die. As shown in FIG. 4, the deep-drawing mold used in the molding test has a special punch shape, an outer peripheral portion is a square tube, and a central portion is a cylinder. The molding test conditions were a wrinkle holding force of 3 MPa, a molding speed of 10 mm / min, and lubrication using a polysheet.

  In this test, after cutting the four corners of the test piece of the size described above (vertical 200 mm × width 200 mm square) as shown in FIG. 3, it was set in a deep-drawing mold and brought to room temperature (25 ° C.). Then, deep drawing was performed under the conditions described above, and the presence or absence of cracks was confirmed. The confirmation result is shown in Table 1 by ○ ×.

  No. Nos. 1 to 10 were obtained by fixing the conditions for instantaneous heating to a processing temperature of 520 ° C. and a processing time of 5 seconds within the requirements defined in the present invention. Nos. 1 to 6 are invention examples in which the conditions of the first heat treatment (artificial aging treatment) were variously changed within the requirements defined in the present invention. Nos. 7 and 8 are comparative examples in which the processing temperature is outside the requirements defined in the present invention, among the conditions of the first heat treatment (artificial aging treatment), No. Nos. 9 and 10 are comparative examples in which the treatment time out of the conditions defined in the present invention is the condition of the first heat treatment (artificial aging treatment).

  No. Nos. 11 to 18 were prepared by fixing the conditions of the first heat treatment (artificial aging treatment) to a treatment temperature of 230 ° C. and a treatment time of 8 seconds within the requirements defined in the present invention. Nos. 11 to 14 are invention examples in which the conditions of instantaneous heating are variously changed within the requirements defined in the present invention, No. 11 to No. 14. Nos. 15 and 16 are comparative examples in which the processing temperature is out of the requirements defined in the present invention among the conditions of instantaneous heating, No. Nos. 17 and 18 are comparative examples in which the processing time is out of the requirements defined in the present invention among the instantaneous heating conditions.

  No. satisfying the requirements of the present invention. 1-6 and no. In Nos. 11 to 14, the proof stress difference obtained in the tensile test was 110 to 140 MPa, and no cracks occurred in the molding test.

  On the other hand, No. which does not satisfy the requirements of the present invention. 7-10 and no. For 15 to 18 (excluding No. 16), the yield strength difference obtained in the tensile test was 80 MPa or less, and cracks occurred in the molding test. No. In No. 16, since the instantaneous heating temperature was too high, the heat was transferred to the peripheral portion, and partial heat treatment could not be performed, so that the specimen was melted.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the process of performing press molding using the aluminum alloy blank material for press molding processing which concerns on this invention, (a) is the blank material before cut | disconnecting to a predetermined shape, (b) is a moment after cutting a predetermined shape. The heated blank material, (c) shows the cooled blank material, and (d) shows the molded product after press forming. It is a longitudinal cross-sectional view which shows the state which performed the press molding of the blank material with the metal mold | die for press molding. It is explanatory drawing which shows the shape of the blank material used as a test material in an Example. It is explanatory drawing which shows the shape of the punch of the deep drawing metal mold | die used for the shaping | molding test of an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Aluminum alloy blank 2 ... Planned part 2a ... All-around part 2b ... Local part 3 ... Base material part

Claims (2)

After heat treatment at 180 to 250 ° C. for 3 to 20 hours on the Al—Mg—Si aluminum alloy plate that has undergone solution treatment and quenching treatment, it is cut into a predetermined shape to obtain an aluminum alloy blank material,
A method for producing an aluminum alloy blank material for press forming, characterized by performing instantaneous heating for 0.5 to 10 seconds at a temperature of 480 to 550 ° C. only on a portion to be processed of the blank material. 2. The press forming process according to claim 1, wherein a difference in tensile strength between a part to be processed of the blank material subjected to instantaneous heating and a tensile strength of another base material part of the blank material is more than 80 MPa and not more than 140 MPa. A method for producing an aluminum alloy blank.

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