JP2010156024A - Method for producing aluminum alloy sheet for cold press forming, and cold press forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve both of securement of high formability of an Al-Mg-Si-based aluminum alloy sheet mainly used as an automotive body sheet and keeping of high productivity in the forming. <P>SOLUTION: Regarding the Al-Mg-Si-based aluminum alloy sheet lying in a sub-aged state by age hardening or in a worked and hardened state by rolling, before cold press forming therefor, solution heat treatment is partially performed, a strength difference is imparted to a heated part and a non-heated part, and the heated part having low strength is made to abut on the pressure pad part, and the non-heated part having high strength is made to abut on a punch shoulder part, thus cold press forming is performed. In the partial solution heat treatment, rapid cooling is performed at ≥50°C/min in such a manner that the heating arrival temperature of the heated part is controlled to 480 to <580°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention uses a method for producing an Al—Mg—Si-based aluminum alloy plate used by forming, particularly cold press forming and paint baking, and an aluminum alloy plate for cold press forming obtained thereby. In particular, various parts and parts of automobiles, ships, airplanes, etc., or building materials, structural materials, other machinery and appliances, home appliances and parts thereof, especially automobile body sheets and bodies The present invention relates to a manufacturing method and a cold press forming method for an Al—Mg—Si-based aluminum alloy plate suitably used for a panel.

Conventionally, cold rolled steel sheets have been mainly used as body seats for automobiles. Recently, however, reduction of CO ₂ emissions has been demanded from the viewpoint of global warming suppression. As a result of recognition, the use of rolled aluminum alloy sheets is increasing. By the way, since the formability of an aluminum alloy rolled sheet is generally inferior to that of a cold-rolled steel sheet, it is an obstacle to expanding its use. In order to improve the formability of the rolled aluminum alloy sheet, improvement of the formability of the material itself and a device for the forming method are strongly demanded.

  Patent Documents 1 and 2 propose applying a warm deep drawing method in order to improve the formability of an aluminum alloy plate. Certainly, the warm forming method can improve the deep drawability of the aluminum alloy sheet, but there are some problems if large-scale industrial production is assumed.

That is, as a feature of the warm deep drawing method, it is required to perform deep drawing while the flange portion is heated and the punch portion is cooled.
1. It is necessary to provide the press machine with heating and cooling functions for the aluminum alloy sheet. Compared with cold press forming, the total forming time is longer, resulting in lower production efficiency and lower forming costs. To increase.
2. Since the molding is performed warmly, the usual cold forming lubricating oil cannot be used, and therefore, it is necessary to develop a new lubricating oil.
3. The configuration of the press machine becomes complicated and requires high equipment costs.
4). As press machines become more complex, concerns about quality control arise.
There are problems such as.

  By the way, the warm deep drawing method is to locally heat and soften a portion having a high degree of processing with respect to the aluminum alloy plate blank at the time of forming, so if it is caught at the time of forming, the aluminum alloy plate blank It can be said that it is intended to improve the formability by partially imparting a strength difference to the other, but in the same way, other strengths that are intended to improve the formability by giving a strength difference to the aluminum alloy sheet blank. As a method, a method in which a blank is subjected to local heat treatment in advance is known (for example, Patent Document 3). This method is particularly suitable for age-hardening alloys such as Al-Mg-Si alloys, which are mainly used for automobile body sheets, in which solid solution precipitation occurs in the matrix due to heat treatment and the strength changes greatly. It is considered effective.

  Here, in the technique disclosed in Patent Document 3, while an Al—Mg—Si based alloy sheet that is shipped after being solution-treated by an aluminum rolling manufacturer is held at room temperature, Mg and Si can be obtained by aging at room temperature. It is possible to give a strength difference in the blank by utilizing the fact that extremely fine precipitates consisting of uniform precipitates in the matrix and the strength is improved compared to immediately after the solution treatment. Is going. That is, in the technique of Patent Document 3, the above-described precipitate formed at room temperature is easily re-solidified by short-time heating at a relatively low temperature of 250 ° C. or more, and the strength of the heated portion is reduced. By utilizing this, it is said that a partial strength difference can be imparted to the aluminum alloy plate by a relatively low-cost and short-time treatment.

By the way, the technique disclosed in Patent Document 3 is a technique for improving formability on the premise that a blank of an aluminum alloy plate is press-molded in a state where the periphery is clamped and the periphery is completely fixed. In the blank surface, the area directly under the punch to which the punch hits during press molding is heated and softened except for the area to which the shoulder of the punch hits to improve the formability. However, in this case, the strain is concentrated in the region immediately below the softened punch, and it has been found that there is a problem in that the thickness of the molded product is insufficient due to significant local thickness reduction in this portion. Further, since press molding is performed with the periphery completely fixed by a clamp, there is a disadvantage in that material inflow from the peripheral wrinkle pressing portion is not allowed at all, and thus the width of improvement in formability is limited. Further, when a body sheet for an automobile is targeted, severe press working (hem processing) is often performed at the periphery of the molded product after press molding. The area directly underneath, that is, the center part of the plate is heated, and the peripheral part of the plate remains in an aging-precipitated state due to normal temperature aging. There was a problem that occurred.
JP-A-4-351229 JP 2006-205244 A JP 2000-117338 A

  In forming the Al—Mg—Si based alloy plate according to the conventional technique as described above, it has been difficult to sufficiently satisfy the formability and other performances required for the recent automobile body sheet.

  That is, recently, a high designability is required for the shape of an automobile panel, and accordingly, a material having a higher formability than that of a conventional material is required, and a material having a particularly high drawability is required. Of course, not only the formability index such as squeezability but also the improvement of squeezability while preventing the bending workability (hem workability), strength and the like from being reduced, However, in these respects, the conventional Al—Mg—Si alloy plate forming method is still insufficient.

  The present invention has been made against the background of the above circumstances, and it is possible to achieve both the securing of the high formability of the Al-Mg-Si based aluminum alloy sheet and the maintenance of the high productivity of the forming process, and other required characteristics. The manufacturing method of an aluminum alloy plate for cold press forming excellent in formability, which can skillfully utilize the difference in material strength without deterioration of the material, and the aluminum alloy plate for cold press forming, An object of the present invention is to provide a cold press-molding method and a cold press-molded product.

  Specifically, cold press forming (cold forming) based on a technology that gives an in-plane strength difference by performing partial heat treatment (partial solution treatment) in advance on an aluminum alloy sheet blank. In order to allow the material inflow from the pressing portion around the drawing in the drawing forming), by performing the cold press forming on the blank whose strength distribution is optimized by appropriately adjusting the heating site by the partial solution treatment, The material flow from the periphery of the blank is promoted, and it is possible to produce a molded product with a uniform thickness and a deep drawing, and at the same time, it is easy to bend the peripheral part of the molded product. It is an object of the present invention to make the heat treatment performed in a short time a process so as not to impair the high production efficiency of the conventional cold press forming.

  As a result of repeated experiments and studies to solve the above-mentioned problems, the present inventors have found that an aluminum alloy plate that is age-hardened and is in a sub-aged state, i.e., room temperature aging or artificial aging after solution treatment on the entire plate. For aluminum alloy sheets that have been subjected to heat treatment or aluminum alloy sheets that have been rolled and work hardened, the heating section in the partial solution treatment is optimally selected so as to improve drawability and bending workability In addition, by optimizing the temperature to reach the heating in the partial solution treatment and the cooling rate after heating, the portion can be recovered in a very short time by recovery and recrystallization during the solution treatment. The present inventors have found that it can be efficiently softened and bendability can be improved, and the present invention has been made.

  Here, the solution treatment is a precipitate composed of Mg and Si precipitated in a matrix by heating a sub-aged Al—Mg—Si alloy, which is a precipitation hardening type alloy, to a high temperature. The aluminum alloy is a softened aluminum alloy that is substantially free of precipitates in the matrix by rapidly cooling to room temperature or near room temperature so that precipitation does not occur during cooling immediately after this treatment. Is obtained. In the case of an aluminum alloy that has been subjected to a rolling process such as cold rolling and is in a work-hardened state (having a work structure), the work structure is recovered and recrystallized simultaneously with heating due to solution treatment. Even in this case, the aluminum alloy plate that has been hardened by rolling softens. In addition, the “partial” solution treatment here refers to selective heating of a predetermined portion for the purpose of improving moldability and bendability, so that only that portion is locally solutionized or recovered. It means a process of recrystallizing and softening a predetermined part.

  Specifically, in the manufacturing method of the aluminum alloy plate for cold press forming according to the first aspect of the invention, the entire Al—Mg—Si alloy rolled plate rolled to a predetermined plate thickness is subjected to a solution treatment. Then, it is age-hardened to be in a sub-aged state, and further, a predetermined region of the whole plate is defined as a heating portion and a region other than the heating portion is defined as a non-heating portion, and a solution treatment is partially performed on the heating portion. The strength of the heated portion at room temperature after the solution treatment is lowered from the strength of the non-heated portion by rapidly cooling after solidifying the aging precipitate.

  The method for producing an aluminum alloy sheet for cold press forming according to the invention of claim 2 is the method for producing an aluminum alloy sheet for cold press forming according to claim 1, wherein the whole rolled plate is subjected to a solution treatment. As a treatment for obtaining a sub-aging state in the above, a normal temperature aging treatment that is maintained at a temperature within a range of 0 ° C. or more and less than 40 ° C. and an artificial aging treatment that is maintained at a temperature within a range of 40 ° C. or more and less than 180 ° C. , One of the processes or a combination of both processes is performed.

  Furthermore, the manufacturing method of the aluminum alloy plate for cold press forming of the invention of claim 3 is preliminarily made out of the whole plate of the Al—Mg—Si alloy rolled plate in a state of being rolled and hardened to a predetermined plate thickness. By defining a certain region as a heating part and defining a region other than the heating part as a non-heating part, by subjecting the heating part to a partial solution treatment to recover or recrystallize the processed structure, The strength of the heated portion at room temperature after the solution treatment is lower than the strength of the non-heated portion.

  According to a fourth aspect of the present invention, in the method for manufacturing an aluminum alloy sheet for cold press forming according to any one of the first to third aspects, the punch shoulder is brought into contact during cold press forming. All or a part of the portion outside the region is defined as the heating portion, and at least a portion to which the punch shoulder portion is to be pressed is defined as the non-heating portion in the region other than the heating portion. It is characterized by this.

  Further, the invention according to claim 5 is the method for producing an aluminum alloy sheet for cold press forming according to any one of claims 1 to 4, wherein the partial solution treatment is performed except for a non-heated portion. Only the part is heated to a temperature in the range of 480 ° C. or more and less than 580 ° C., and cooled to a temperature range of 50 ° C. or less at a cooling rate of 50 ° C./min or more.

  Further, the invention of claim 6 is the method for producing an aluminum alloy sheet for cold press forming according to any one of claims 1 to 5, wherein the unheated part is pulled at room temperature after the partial solution treatment. The difference between the strength and the 0.2% proof stress of the heated portion is increased by 20 MPa or more after the partial solution treatment.

  Furthermore, the invention of claim 7 is the method for producing an aluminum alloy plate for cold press forming according to any one of claims 1 to 6, wherein the aluminum alloy plate is used as a heating part in the partial solution treatment. Of the blank, the portion outside the region where the punch shoulder is in contact during press molding is included, and the portion to be bent after molding is included.

  The invention of claim 8 is the method for producing an aluminum alloy plate for cold press forming according to any one of claims 1 to 6, wherein the heating part in the partial solution treatment is subjected to press forming. Of the aluminum alloy plate blank, all the regions inside the region where the punch shoulder is in contact or one region or two regions or more in any shape within this region are included.

  Furthermore, the invention of claim 9 is the method for producing an aluminum alloy sheet for cold press forming according to any one of claims 1 to 8, wherein the MgO. 2 to 1.5% (mass%, the same shall apply hereinafter), Si 0.3 to 2.0%, and Fe 0.03 to 1.0%, Mn 0.03 to 0.6%, Cr 0.01 to 0 .4%, Zr 0.01-0.4%, V 0.01-0.4%, Ti 0.005-0.3%, Zn 0.03-2.5%, Cu 0.01-1.5% It is characterized by using an aluminum alloy plate containing one or more selected from the group consisting of Al and inevitable impurities.

  On the other hand, the cold press forming method of the invention of claim 10 performs cold press forming using the aluminum alloy plate obtained by the manufacturing method according to any one of claims 1 to 9. It is characterized by.

  According to the present invention, an Al—Mg—Si-based aluminum alloy plate that is age-hardened after solution treatment of the entire plate and is in a sub-aged state, or an Al—Mg—Si-based aluminum that is work-hardened by rolling. Part of the alloy plate, especially the part that should become the wrinkle holding part during cold press forming, is locally heated (partial solution treatment), and the part is reduced in strength by solid solution or recovery / recrystallization of the precipitated elements. It is possible to improve press formability by providing a difference in strength between the punch shoulder portion which is a non-heated portion. Moreover, since such a partial solution treatment is performed as a separate process prior to cold press forming, the press forming itself can be performed at a high speed by a conventional cold press machine, so There is no increase in equipment cost or reduction in production efficiency of the press machine as in the case of forming, and there is no need for special lubricating oil. Furthermore, it becomes possible to improve the bending workability of the molded product by optimally selecting the heating region for performing the local solution treatment.

  The material of the aluminum alloy plate used in the present invention is basically an Al-Mg-Si aluminum alloy plate, and after the solution treatment is applied to the entire plate at a high temperature, normal temperature aging or artificial aging or It is assumed that it has been subjected to an aging treatment by a combination of normal temperature aging and artificial aging and is in a sub-aged state, or has been rolled and work hardened. Therefore, the present invention will be described in detail with the main items divided into items.

<Method for producing aluminum alloy sheet material for cold press forming>
First, the production method of the aluminum alloy sheet material for cold press forming will be explained. Basically, it can be produced by a method generally adopted in the aluminum alloy manufacturing industry.

  That is, an aluminum alloy melt adjusted to a predetermined component is cast by appropriately selecting a normal melting casting method. Here, the normal melt casting method includes, for example, a semi-continuous casting method (DC casting method), a thin plate continuous casting method (roll casting method, etc.) and the like. Next, the aluminum alloy ingot is subjected to homogenization at a temperature of 480 ° C. or higher. Homogenization treatment mitigates microsegregation of alloying elements during solidification of molten metal, and in the case of containing various transition elements including Mn / Cr, dispersed particles of intermetallic compounds mainly composed of these, This is a process necessary for uniformly and densely depositing in the matrix. The heating time for the homogenization treatment is usually 1 hour or more, and is usually terminated within 48 hours for economic reasons. However, since the heating temperature in this homogenization treatment is close to the heat treatment temperature for heating to the hot rolling start temperature before hot rolling, it is also possible to perform the homogenization processing together with the heat treatment before hot rolling. Before or after this homogenization treatment step, chamfering is performed as appropriate, hot rolling is started within a temperature range of about 300 to 590 ° C., and then cold rolling is performed, whereby an aluminum alloy having a predetermined plate thickness is obtained. Manufacture a board. In the course of hot rolling, in the middle of hot rolling and cold rolling, or in the middle of cold rolling, intermediate annealing or solution treatment may be performed as necessary.

  Thus, about the board (cold-rolled board) rolled to the predetermined sheet thickness, after performing the solution treatment to the whole cold-rolled sheet, it is age-hardened, and then the partial solution treatment is performed. When applied (Claims 1 and 2) and in the state of being work hardened by cold working (including the case of being slightly aged at room temperature during the room temperature standing period after the final cold rolling) There is a case (Claim 3) for use in processing.

The solution treatment described above is a step for dissolving Mg ₂ Si, elemental Si, etc. in the matrix, and differs from the subsequent partial solution treatment in that it is performed over the entire plate. This solution treatment is usually performed at a high temperature of 480 ° C. or higher. Since eutectic melting may occur when the solution treatment temperature exceeds 590 ° C., it is usually set to 590 ° C. or less, and after reaching the heating temperature, it is not held or is held for a short time of about 5 minutes or less and then 50 ° C. Rapid cooling to room temperature or near room temperature (usually to about 50 ° C. or less) at a cooling rate of about / min or more.

  Here, the solution treatment over the entire plate can be efficiently performed by continuously passing the cold rolled plate wound in a coil shape through a continuous annealing furnace having a heating zone and a cooling zone. it can. In such a continuous annealing furnace, the aluminum alloy sheet is heated to a high temperature of 480 ° C. or more and 590 ° C. or less when passing through the heating zone, and then rapidly cooled when passing through the cooling zone. Through such a series of treatments, Mg and Si, which are the main alloying elements of the alloy targeted by the present invention, were once dissolved in the matrix at a high temperature, and then rapidly cooled, thereby becoming supersaturated at room temperature. It becomes a state.

<Age hardening for sub-aging state>
In order to give a difference in strength between the heated part and non-heated part of the plate by partial solution treatment, the sub-aging state is preliminarily applied by aging treatment to the alloy that has been solution-treated over the entire plate as described above. That is, it is necessary to increase the overall strength of the alloy plate in a state where clusters or fine precipitates (usually called β ″ phase) made of Mg and Si are generated in the matrix. If it is not in such a state, even if a partial solution treatment is subsequently performed, the strength difference cannot be imparted to the alloy plate because there is no decrease in strength in the heating section.

  As an aging treatment for obtaining a sub-aging state, normal temperature aging is performed in which the material is held within a temperature range of 0 ° C. or more and less than 40 ° C. In this normal temperature aging, a cluster called a low temperature cluster out of clusters mainly composed of Mg and Si precipitates and sub-aging progresses, thereby improving the strength. If such normal temperature aging is performed, the aging temperature is low, so even if one year, which is a long-term holding time assumed in normal industrial production, has passed, the peak aging that gives the maximum strength or exceeds this state An overaged state in which the strength decreases cannot be achieved, and the subaged state can always be maintained.

  Moreover, when it is desired to increase the difference in strength between the heated part and the non-heated part to increase the range of improvement in formability, as an aging treatment for making the sub-aged state, within a temperature range of 40 ° C. or higher and lower than 180 ° C. Artificial aging to hold the material may be performed. The holding time in this case is not particularly limited. However, in consideration of the fact that the peak aging of the Al—Mg—Si alloy is usually achieved at a holding time of 8 hours or more at 180 ° C. The condition of the artificial aging treatment for setting the aging state is that the holding time in the range of 40 ° C. or more and less than 110 ° C. within the temperature range of 40 ° C. or more and less than 180 ° C. is within 24 hours, and the range of 110 ° C. or more and less than 180 ° C. The holding time is preferably within 6 hours.

  Here, when the aging treatment is performed beyond the sub-aging and the peak aging is obtained to obtain the maximum strength, the region that becomes the non-heated portion in the partial solution treatment is in a state of peak aging at the time of press molding. In such a peak aging state, the elongation is greatly reduced, and it becomes extremely easy to crack during press molding. This is the same even when it is aged beyond the peak aging at which the maximum strength is obtained and until it reaches an overaging state in which the strength decreases, and the elongation in the region that becomes the non-heated part in the partial solution treatment is low. , Very easy to break. On the other hand, when the sub-aged state is set as in the present invention, the elongation of the non-heated portion is larger than the peak-aged state, so that cracking hardly occurs during press molding. Therefore, from the viewpoint of preventing the occurrence of cracks in the non-heated region at the time of molding, the artificial aging performed in the temperature range of 40 ° C. or higher and lower than 180 ° C. is as low as possible for a short time (preferably a temperature of 40 ° C. or higher and lower than 110 ° C. The holding time in the range is 14 hours or less, the holding time in the temperature range of 110 ° C. to 180 ° C. is 4 hours or less), and even in the sub-aging range, the material is stretched in the initial state as much as possible. It becomes large and preferable. This is because the strength difference between the heated and non-heated parts after the partial solution treatment is larger when the strength is increased by promoting aging within the sub-aging range before the partial solution treatment. The moldability improvement effect by means that there is a trade-off relationship. Therefore, in practice, it is necessary to adjust to an optimum aging state within the sub-aging range according to the shape of the molded product.

<Work hardening by rolling>
In order to give a difference in strength between the heated part and non-heated part of the plate by the partial solution treatment, the state of the alloy plate subjected to the partial solution treatment is in the sub-aging state as described above. In addition, it may be in a state of being work hardened by rolling (a state having a working structure). This is because heat treatment is performed under the conditions of the partial solution treatment specified in the present invention, and the work structure that has been hardened by rolling is softened by recovery and recrystallization, and the strength difference between the heated part and the non-heated part. This is because the purpose of granting can be achieved. Usually, in the production of an alloy plate, the final rolling process is performed by cold rolling, and the degree of hardening by cold rolling of the alloy plate depends on the cold rolling rate defined by the following equation.
Cold rolling rate = (sheet thickness before cold rolling−sheet thickness after cold rolling) / (sheet thickness before cold rolling) × 100
Here, the plate thickness before cold rolling is usually the plate thickness before hot rolling is finished and cold rolling is started, but as described later, in the middle of cold rolling after hot rolling. When the solution treatment (intermediate solution treatment) is performed on the entire plate, the thickness is the plate thickness before starting the final cold rolling after the intermediate solution treatment.

  In the present invention, the cold rolling rate (final cold rolling rate) is not particularly limited, but is preferably 20% or more. When the cold rolling rate is less than 20%, the increase in the strength of the entire alloy sheet due to work hardening in cold rolling is small, so that in the subsequent partial solution treatment, softening in the heating part is caused. Since the degree is small, it becomes impossible to give a sufficient strength difference, and the crystal grains generated by recrystallization in the heating part in the partial solution treatment process become coarse, which may cause an appearance defect called rough skin. .

  If a solution treatment (intermediate solution treatment) is performed on the entire plate before such final cold rolling, a large strength difference can be imparted with a smaller cold rolling rate. This intermediate solution treatment is usually performed by passing the rolled sheet wound in a coil shape through a continuous annealing furnace having a heating zone and a cooling zone, as in the solution treatment before the sub-aging treatment. This is performed on the entire plate and may be performed under the same conditions as the solution treatment before the sub-aging treatment already described. After solid solution of Mg and Si once by such an intermediate solution treatment, the final cold rolling is performed, so that the hardening by normal temperature aging becomes work hardening while keeping the cold rolled sheet at room temperature. Superimpose. That is, in the actual mass production process, after the final cold rolling, it is usually left at room temperature for a certain period of time until the partial solution treatment is performed. Although normal temperature aging progresses to a certain extent, it is normal that such age hardening during normal temperature standing is superimposed on work hardening. If such an alloy plate is subjected to a partial solution treatment, the precipitate is formed into a solution, and the recovery and recrystallization of the processed structure are simultaneously generated and softened. Therefore, a large strength difference can be imparted by the partial solution treatment even at a lower cold rolling rate.

<Partial solution treatment>
The most important feature of the present invention is that the Al—Mg—Si based aluminum alloy sheet in the sub-aged state or work hardened state is partially (as a place in a two-dimensional plane) before cold press forming. This means that the solution treatment is performed partially and not the degree), and a strength difference is imparted between the heated portion and the non-heated portion by the partial solution treatment after cooling at room temperature.

  Here, it is known that the deep drawing forming limit is determined by the magnitude relationship between the breaking strength of the punch shoulder and the inflow resistance of the wrinkle holding portion (flange). Aluminum alloy sheets for automobile body sheets are usually left at room temperature from material solution treatment at the manufacturer to press forming by the user, but Al-Mg-Si alloys are age-precipitation hardening type alloys. Therefore, if the room temperature storage period is long, the material strength increases due to room temperature aging during the room temperature storage period. If it is going to be cold press-molded as it is, the inflow resistance of the wrinkle holding part is large, and the press formability is lowered.

  However, the Al-Mg-Si-based aluminum alloy plate in the sub-aged state or the work-hardened state as described above is partially subjected to solution treatment before cold press forming. The strength of the is reduced locally. The present invention utilizes such partial softening of the alloy plate, with the heated portion having reduced strength applied to the wrinkle holding portion and the non-heated portion remaining high in strength to the shoulder portion of the punch. By press molding, press moldability can be greatly improved.

  Here, as a result of detailed studies by the present inventors, the difference between the tensile strength of the non-heated part and the proof stress of the heated part (0.2% proof stress) at room temperature is 20 MPa or more before and after partial recovery heating. It became clear that the expansion was essentially effective. This is because, by giving such a large difference in strength, the material inflow resistance (the proof strength of the wrinkle holding portion) from the wrinkle holding portion, whose strength has been relatively reduced during the drawing process, is reduced. This is because the material strength (tensile strength) of the portion corresponding to the strong punch shoulder can withstand a larger inflow of material, and as a result, deep drawing is possible. As described above, the difference between the tensile strength in the non-heated part and the proof stress value in the heated part, which is more important in improving the drawability, can be expanded before and after the partial solution treatment. They have found that it is effective in improving the deep drawability of the alloy plate. When the increase in the difference between the tensile strength of the non-heated part at room temperature and the proof stress of the heated part before and after the partial solution treatment is less than 20 MPa, sufficient improvement in moldability cannot be obtained.

  Here, the tensile strength and the proof strength in the state before the partial solution treatment can be considered to be almost uniform in the alloy blank, and the tensile test piece is sampled from an arbitrary position of the alloy plate blank. The tensile strength and the proof strength obtained by performing the above can be regarded as the tensile strength of the non-heated portion and the proof strength of the heated portion before partial solution treatment, respectively. On the other hand, in the state after the partial solution treatment, the strength is different between the heated part and the non-heated part. Therefore, it is necessary to collect a tensile test piece from each part and perform a tensile test. Here, the non-heated part means a part (region) that is not intended to decrease the strength due to the partial solution treatment, but the performance of the partial solution treatment apparatus and the reached temperature in the partial solution treatment. Depending on the temperature, the temperature of the non-heated part may rise to some extent due to heat transfer and residual heat from the heating part. When the partial solution treatment is performed in an ideal manner in which the temperature does not substantially increase in the non-heated part, the tensile strength of the non-heated part is the same as that before the partial solution treatment. In this case, the decrease in the yield strength in the heated portion is an increment before and after the partial solution treatment of the difference between the tensile strength of the non-heated portion and the yield strength of the heated portion at room temperature. On the other hand, depending on the method and conditions of partial solution treatment, the temperature of the non-heated part rises to some extent in the partial solution treatment, and the solid solution of precipitates and the recovery / re-working of the processed structure are slight. Crystals may be generated, and the tensile strength of the non-heated part may be slightly reduced. However, even in such a case, as defined in the present invention, if the increase before and after the partial solution treatment about the difference between the tensile strength of the non-heated part at room temperature and the proof stress of the heated part is 20 MPa or more, The press formability of the alloy plate blank can be substantially improved by the partial solution treatment. This is the reason why the increase in the tensile strength of the non-heated part and the difference in yield strength of the heated part before and after the partial solution treatment in the present invention was used as an index.

<Details about the site for partial solution treatment>
Next, the part heated in the partial solution treatment and the part not heated will be described in more detail.

  Basically, as described above, the heating part is selected so that the heated part with low strength hits the wrinkle holding part and the non-heated part with high strength hits the shoulder of the punch, but press forming for deep drawing 1 is schematically shown in FIG. 1, and a portion where the partial solution treatment is performed will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a die, 2 denotes a punch, 3 denotes a shoulder of the punch 2, 4 denotes a wrinkle presser, and 5 denotes an aluminum alloy plate blank.

  In FIG. 1, in the partial solution treatment, a region A (wrinkle presser 4) that is a portion of the aluminum alloy plate blank 5 that is outside the region B with which the punch shoulder 3 comes into contact during press forming. It is effective to soften all or a smaller part of the region on the other side as a heating part. As a special case, one or two or more shapes that are partially deepened in the region C inside the region B with which the punch shoulder 3 is in contact (for example, described later) In Example 3 and FIG. 6), as defined in claim 8, one region or two regions or more of an arbitrary shape optimized corresponding to the shape in the region C is added as a heating unit. However, it is effective for obtaining a good molded product by press molding.

  In addition, the present invention solves the problem of low bending workability of molded products, which has been a problem in the prior art, in which a partial heat treatment is applied to an alloy plate blank that is aged at room temperature to improve formability. The In other words, this is a problem in panels that require bending after forming, but bending after press forming is often a part outside the region B where the punch shoulder is in contact. In the case of this invention, it can be solved by selectively adding a part to be bent after press molding as a heating part. This is defined in claim 8. Here, since the partial solution treatment has the effect of greatly improving the bending workability deteriorated by normal temperature aging, artificial aging, and rolling, the above-described effects can be obtained.

<Detailed conditions for partial solution treatment>
As a condition for the partial solution treatment, in claim 5, after heating to a temperature in the range of 480 ° C. or more and less than 590 ° C., the solution is cooled to a temperature of 50 ° C. or less at a cooling rate of 50 ° C./min or more. The reason why such conditions are specified will be described next.

  In order to improve the press formability by increasing the difference between the tensile strength of the non-heated part at room temperature and the proof stress of the heated part by 20 MPa or more before and after the partial solution treatment, in the region heated by the partial solution treatment It is preferable that the heating attainment temperature is within a range of 480 ° C. or more and less than 590 ° C. If the heating temperature is within this temperature range, it is possible to completely dissolve Mg and Si from the clusters and fine precipitates that are in the sub-aging state and exist in the matrix, and work hardening by rolling. It becomes possible to recover and recrystallize the processed structure in the finished state. As a means for softening the Al—Mg—Si alloy in the sub-aged state by heating, heating within a temperature range lower than the temperature reached by heating (about 150 ° C. or more and less than about 350 ° C.) defined in claim 5 A holding method is also conceivable. However, only the so-called low-temperature cluster composed of Mg and Si formed during normal temperature aging is re-dissolved by such relatively low-temperature heating. High-temperature clusters formed at temperatures slightly higher than normal temperature and precipitates called β '' do not dissolve in such heat treatment within a relatively low temperature range, but rather the size of these precipitates. There is a risk that aging will increase and curing will occur. On the other hand, in the solution treatment performed within the temperature range defined in the present invention, any of these types of clusters and precipitates can be easily solid-solved and softened, so before the partial solution treatment. High degree of freedom in aging conditions to achieve sub-aging state. In addition, by performing sub-aging treatment under conditions where β '', which greatly contributes to precipitation strengthening, is set to a relatively high state of the alloy sheet, a heated part and a non-heated part are obtained by partial solution treatment. It is easy to increase the difference in strength.

Here, when the heating attainment temperature of the heating part in the partial solution treatment is less than 480 ° C., since the temperature is low, the solid solubility limit of Mg and Si is small, and Mg and Si can be completely solutionized. As a result, a large amount of Mg and Si, which are not dissolved, are precipitated on the grain boundaries as coarse Mg ₂ Si particles. For this reason, intergranular cracking is likely to occur, the elongation of the material is greatly reduced, and it becomes extremely susceptible to cracking during press molding, and the press moldability is not substantially improved. When the temperature reached by heating is 590 ° C. or higher, the alloy melts in a part of the matrix, and the elongation of the material after cooling to room temperature is significantly reduced. Cracks are very likely to occur, and the press formability is not substantially improved.

Further, the difference between the tensile strength of the non-heated part at room temperature and the proof stress of the heated part is increased by 20 MPa or more before and after the partial solution treatment, and the heating part after the partial solution treatment for improving the press formability is obtained. A cooling rate shall be 50 degrees C / min or more. When the cooling rate is less than 50 ° C./min, many precipitates on the coarse Mg ₂ Si crystal grain boundary composed of Mg and Si during cooling, so that intergranular cracking easily occurs, and the elongation of the material decreases, It becomes extremely fragile during press molding, and the press moldability is not substantially improved.

  Further, cooling at a cooling rate of 50 ° C./min or more needs to be performed to 50 ° C. or less. When the cooling is not performed to 50 ° C. or lower, age hardening is again performed in the region where the partial solution treatment is performed until the natural cooling is performed from the temperature higher than 50 ° C. to the temperature of 50 ° C. or lower after the cooling is completed. As a result, the softening effect decreases.

  In addition, although the heating temperature increase rate to the heating ultimate temperature with respect to the heating part in a partial solution treatment is not specifically limited, Usually, it shall be 50 degrees C / min or more. Similarly, the holding time at the heating temperature in the partial solution treatment is not particularly defined, but it may be held for about 10 minutes or less without holding.

  In addition, as a partial solution treatment, a specific means for locally heating a predetermined portion (heating portion) is not particularly limited. For example, a portion corresponding to a wrinkle holding portion during press molding is heated. It is possible to apply a method such as bringing a metal lump into contact with each other or heating only that portion with hot air.

<Normal temperature standing period from partial solution treatment to cold press forming>
Although it is not particularly limited in this invention, as the period of standing at room temperature from the partial solution treatment to cold press forming, the strength of the portion softened by the partial solution treatment is the original strength due to normal temperature aging It is desirable to determine that cold press forming is performed before returning to the upper limit. Further, a substantially preferable state is that while the difference between the tensile strength of the non-heated portion before the partial solution treatment and the yield strength of the heated portion is maintained at 20 MPa or more after the solution treatment, the cooling is maintained. It is to perform press forming. However, in order to obtain a sub-aging state before partial solution treatment, artificial aging is performed at a predetermined temperature condition in addition to normal temperature aging, and the strength of the entire alloy plate is sufficiently increased, or rolling processing It has been found that the strength difference imparted by the partial solution treatment is hardly lowered during the holding at room temperature, and the effect is maintained semipermanently.

  The oiling process necessary for normal press molding is desirably performed during this standing period or immediately before performing cold press molding.

<Component composition of aluminum alloy plate>
The aluminum alloy plate for forming according to the present invention may basically be an Al—Mg—Si alloy, and its specific composition is not particularly limited, but is usually specified in claim 9. An alloy having such a component composition, that is, Mg 0.2 to 1.5%, Si 0.3 to 2.0%, Fe 0.03 to 1.0%, Mn 0.03 to 0.6%, Cr0 0.01-0.4%, Zr 0.01-0.4%, V 0.01-0.4%, Ti 0.005-0.3%, Zn 0.03-2.5%, Cu 0.01-1. It is preferable to use an aluminum alloy containing one or two or more selected from 5%, with the balance being Al and inevitable impurities.

  The reason for limiting the component composition of the material alloy defined in claim 9 will be described below.

Mg:
Mg is an alloy element that is a basic alloy of the system targeted by the present invention, and contributes to strength improvement in cooperation with Si. If the Mg content is less than 0.2%, the amount of β "phase that contributes to strength improvement by precipitation hardening during baking is reduced, so that sufficient strength improvement cannot be obtained, while if it exceeds 1.5%, it is coarse. Mg-Si based intermetallic compounds are produced, and the formability, particularly bending workability, is reduced, so the Mg content is within the range of 0.2 to 1.5%. In order to improve the workability, the Mg content is preferably in the range of 0.3 to 0.9%.

Si:
Si is also an alloy element that is fundamental in the alloy of the present invention, and contributes to strength improvement in cooperation with Mg. In addition, Si is produced as a crystallized product of metal Si at the time of casting, and the periphery of the metal Si particles is deformed by processing and becomes a recrystallization nucleus generation site during solution treatment. It also contributes to If the amount of Si is less than 0.3%, the above effect cannot be obtained sufficiently. On the other hand, if it exceeds 2.0%, coarse Si particles and coarse Mg-Si based intermetallic compounds are produced, and formability, particularly This causes a decrease in bending workability. Therefore, the Si amount is set in the range of 0.3 to 2.0%. In order to obtain a better balance between press formability and bending workability, the Si content is preferably in the range of 0.5 to 1.4%.

  The above Mg and Si are basic alloy elements as an Al—Mg—Si-based aluminum alloy, but Fe 0.03 to 1.0%, Mn 0.03 to 0.6%, Cr 0.01 to 0.4%, Zr 0.01-0.4%, V 0.01-0.4%, Ti 0.005-0.3%, Zn 0.03-2.5%, Cu 0.01-1.5% One or two or more selected from among them are included. The reason for these additions and the reason for limiting the addition amount are as follows.

Ti, V:
Ti is an element effective for improving the strength and preventing corrosion by refining the ingot structure, and V is an element effective for improving the strength and preventing corrosion. If the Ti content is less than 0.005%, a sufficient effect cannot be obtained. On the other hand, if the Ti content exceeds 0.3%, the effects of refinement of the ingot structure and corrosion protection due to the addition of Ti are saturated. If V is less than 0.01%, a sufficient effect cannot be obtained. On the other hand, if it exceeds 0.4%, the anticorrosive effect by addition of V is saturated. If the upper limit is exceeded, coarse Ti or V-based intermetallic compounds increase, which leads to a decrease in formability and hemmability.

Mn, Cr, Zr:
These elements are effective for improving the strength, refining crystal grains, or improving aging (bake hardenability). If the Mn content is less than 0.03% or the Cr and Zr contents are each less than 0.01%, the above effect cannot be obtained sufficiently, while the Mn content exceeds 0.6%. If the Cr, Zr content exceeds 0.4%, not only the above effects will be saturated, but also a large number of intermetallic compounds may be produced, which may adversely affect the formability, particularly hem bendability. Therefore, Mn is in the range of 0.03 to 0.6%, and Cr and Zr are in the range of 0.01 to 0.4%, respectively.

Fe:
In general aluminum alloys, Fe is usually contained as an inevitable impurity in an amount of less than 0.03%. On the other hand, Fe is an element effective for strength improvement and crystal grain refinement, and in order to exert these effects, Fe may be positively added by 0.03% or more. However, if the content is less than 0.03%, a sufficient effect cannot be obtained. On the other hand, if it exceeds 1.0%, the formability, particularly the bending workability, may be lowered. Therefore, Fe is actively added. In this case, the amount of Fe was set in the range of 0.03 to 1.0%.

Zn:
Zn is an element that contributes to strength improvement through aging improvement and is effective in improving surface treatment properties. However, if the amount of Zn is less than 0.03%, the above effect cannot be obtained sufficiently, while 2.5 If it exceeds 50%, the moldability and the corrosion resistance decrease, so the Zn content is set in the range of 0.03 to 2.5%.

Cu:
Cu is an element added for improving formability and strength, and 0.01% or more is added for the purpose of improving formability and strength. However, if the Cu content exceeds 1.5%, the corrosion resistance (intergranular corrosion resistance, yarn rust resistance) deteriorates, so the Cu content is restricted to 1.5% or less. In addition, when importance is attached to strength improvement, the Cu content is preferably 0.4% or more, and when it is desired to further improve the corrosion resistance, the Cu content is preferably 1.0% or less.

  Moreover, in general Al alloy, B may be added simultaneously with the above-mentioned Ti for refining the ingot structure. By adding B together with Ti, the ingot structure can be refined and stabilized. The effect becomes more remarkable. In the case of this invention, it is permissible to add 500 ppm or less of B together with Ti.

  Examples of the present invention will be described below together with comparative examples. The following examples are for explaining the effects of the present invention, and the processes and conditions described in the examples do not limit the technical scope of the present invention.

[Example 1]
After the aluminum alloy was dissolved and the components were adjusted, the alloy No. 1 in Table 1 was cast by DC casting. 1-No. An aluminum alloy ingot having the chemical composition shown in 4 was produced. The ingot was subjected to soaking for 10 hours at 530 ° C., and then hot rolled according to a conventional method to produce a rolled plate having a thickness of 4 mm. Thereafter, cold rolling, solution treatment, and aging treatment were performed in the process sequence and conditions shown in Table 2 to produce an aluminum alloy plate having a thickness of 1 mm, which was used as a test material for the following experiments. The solution treatment described above is a method in which rapid heating, short-time holding, and rapid cooling are continuously performed on the entire plate. Here, the ultimate temperature in this treatment is 530 ° C., and the cooling rate is 200. Cooled to room temperature at a temperature of ° C / min.

  From these alloy sheets, a tensile test piece (JIS No. 5 test piece shape) is taken so that the tensile direction is perpendicular to the rolling direction, and a tensile test is performed to obtain mechanical properties (tensile strength, yield strength, elongation). The results are shown in Table 2 as the mechanical properties before the partial solution treatment. The alloy plate was subjected to a partial solution treatment by the method described below and then subjected to a formability evaluation test.

  That is, a disc blank for formability evaluation of a predetermined size was produced from each alloy plate. As shown in FIG. 2, a partial solution treatment was performed by setting the region of 55.7 mmφ at the center of the disk sample 5 as a non-heating portion Q and the surrounding region as a heating portion P. This heating part P is all the part outside the area where the shoulder part 3 of the punch 2 comes into contact during press molding. As a specific method of the partial solution treatment, the disc blank 5 was sandwiched between the upper board 6 and the lower board 7 of the partial solution treatment apparatus having a shape schematically shown in FIG. In FIG. 3, each of the upper board 6 and the lower board 7 is a non-heating part 8 whose central part is cooled by water cooling, and the surrounding part is a heating part 9 incorporating a heater. Table 2 shows the heating temperature and cooling rate conditions in the heating section at this time. In any case, the holding time at the heating temperature was 1 second.

  The disc blank subjected to the partial solution treatment under these conditions is subjected to the formability evaluation test described below, and the small tensile test piece 10 having the shape shown in FIG. Samples were taken from both the part P and the non-heated part Q (the collection position is shown in FIG. 5), and subjected to a tensile test to examine the tensile strength of the non-heated part Q and the proof stress of the heated part P. It was shown to. The strength evaluation of each part after the partial solution treatment was performed one day after the partial solution treatment. Also, one day after the partial solution treatment, a small tensile test piece was taken from the heated part of the disk, and after applying 5% tensile deformation, the parallel part of the test piece was cut out. The bendability evaluation test was conducted.

  That is, after bending at a bending radius of 0.8 mm until the angle is 90 °, a line perpendicular to the tensile direction located at the center of the parallel part of the test piece is bent, and further bent to an angle of 135 °, A plate having a thickness of 1.0 mm was inserted on the assumption that the inner panel was to be inserted inside, and the plate was folded to an angle of 180 ° so as to sandwich the plate and adhered. The outside of the bent portion was confirmed with a loupe, and it was judged that the bending workability was good when no cracks occurred, and the bending workability was judged poor when the cracks occurred. The bendability evaluated in this way is shown in Table 3.

  The moldability evaluation test was conducted by a cylindrical deep drawing test one day after the partial solution treatment. The punch used in this test had a punch diameter of 50 mm and a punch angle radius of 5.0 mm, and the die had a die inner diameter of 53.64 mm and a die shoulder radius of 13.0 mm. As conditions for the deep drawing test, the punching speed was 180 mm / min, the wrinkle pressing force was 150 kg, and Johnson Wax (trademark) was applied to both sides of the blank as a lubricant. A deep drawing test was performed on a partially blanked alloy sheet blank. If three or more of the five sheets could be drawn, the diameter of the disk was increased by 0.5 mm and the deep drawing test was performed again. went. By repeating this, the diameter of the maximum disk that can be drawn was determined, and this numerical value was divided by the punch diameter of 50 mm to determine the limit drawing ratio LDR. For comparison, LDR was also obtained for a game metal plate not subjected to partial solution treatment, and the results of these cylindrical deep drawing tests are shown in Table 3. Here, when the partial solution treatment is performed, when the LDR is increased by 0.1 or more compared to the case where this treatment is not performed, the partial solution treatment has substantially improved the moldability. It was judged.

  Conditions 1 to 6 are cold rolling, solution treatment, and aging treatment after hot rolling under the process conditions within the range of the present invention as shown in Table 2 for Alloy 1 within the component composition range defined in the present invention ( A match solution that has been sub-aged by performing normal temperature aging) is subjected to partial solution treatment under different conditions.

  Among these, conditions 1 to 3 are that the temperature reached by heating and the cooling rate of the partial solution treatment are both within the condition range of the present invention. Therefore, in each case, the tensile strength of the non-heated part and the proof stress difference of the heated part at room temperature. However, it increased by 20 MPa or more before and after the partial solution treatment. In these examples, the LDR in the moldability evaluation test was improved by 0.1 or more compared with the case where the partial solution treatment was not performed, and it was confirmed that there was a substantial improvement in moldability. In these examples, the bendability of the heated portion was also good.

On the other hand, Condition 4 is an example in which the temperature reached by heating in the partial solution treatment is lower than the process condition range defined in the present invention. In this case, the solid solubility limit of Mg and Si is small, and Mg and Si are completely contained. A large amount of Mg and Si that could not be dissolved in the solution and precipitated as coarse Mg ₂ Si particles on the grain boundaries, and therefore, grain boundary cracking in the heating part of the partial solution treatment And the elongation of the material was greatly reduced, making it very easy to crack during press molding. Therefore, the LDR in the moldability evaluation test was determined not to improve by 0.1 or more compared to the case where the partial solution treatment was not performed, and it was determined that the moldability was not substantially improved. Further, in this case, it was found that cracking is likely to occur during bending in the heating section, and the bendability is poor.

  Condition 5 is an example in which the temperature reached by heating in the partial solution treatment is higher than the range specified in the present invention. In this case, the alloy melts in a part of the matrix and is cooled to room temperature. The elongation of the material was remarkably reduced, and cracking was very likely to occur in this heated portion during press molding. And it turned out that LDR in a moldability evaluation test does not improve 0.1 or more compared with the case where a partial solution treatment is not performed, and the moldability does not substantially improve. Further, in this example, it was confirmed that cracking was likely to occur during bending at the heated portion, and the bendability was poor.

Condition 6 is an example in which the cooling rate after heating in the partial solution treatment is lower than the range defined in the present invention. In this case, on the coarse Mg ₂ Si crystal grain boundary composed of Mg and Si during cooling. In the heated portion, grain boundary cracking was likely to occur, and the elongation of the material was reduced, making it very easy to crack during press molding. And it turned out that LDR in a moldability evaluation test does not improve 0.1 or more compared with the case where a partial solution treatment is not performed, and the moldability does not substantially improve. Further, in this case, it was confirmed that cracking was likely to occur during bending at the heated portion, and the bendability was poor.

  On the other hand, the condition 7 is the cold rolling, solution treatment, aging treatment (artificial aging) after hot rolling on the alloy 1 in the component composition plate of the present invention under the conditions within the process condition range of the present invention as shown in Table 2. It is an example in which a partial solution treatment was performed under conditions within the scope of the present invention for match money that was sub-aged by performing (+ normal temperature aging). In this case, the difference in tensile strength between the non-heated part at room temperature and the proof stress of the heated part is increased by 20 MPa or more before and after the partial solution treatment, and therefore LDR in the moldability evaluation test does not perform the partial solution treatment. Compared to the case, it was confirmed that the moldability was substantially improved by 0.1 or more.

  Condition 8 and Condition 9 are for the alloy 1 within the composition range of the present invention, cold rolling / solution treatment / room temperature after hot rolling under the conditions within the process condition range of the present invention as shown in Table 2. By performing neglect (normal temperature aging that does not become sub-aged), game solution in a state of being substantially rolled (work hardened) is partially solutionized under conditions within the scope of the present invention. This is an example of processing. Also in these cases, the difference in tensile strength between the non-heated part and the proof stress of the heated part at room temperature increases by 20 MPa or more before and after the partial solution treatment. For this reason, it was found that the LDR in the moldability evaluation test was improved by 0.1 or more compared to the case where the partial solution treatment was not performed, and the moldability was substantially improved.

  On the other hand, the condition 10 is the cold rolling / solution treatment / aging after hot rolling under the conditions outside the process condition range of the present invention as shown in Table 2 for the alloy 1 within the component composition range of the present invention. This is an example of processing. Specifically, the aging treatment is performed by a combination of artificial aging (185 ° C. × 7 h) and normal temperature aging (20 ° C. × 10 days), the temperature of the artificial aging is higher than the range specified in the present invention, and the time is This is a long example. In this example, the alloy plate exceeds the sub-aging state, which is an optimum state, reaches a peak aging state or an over-aging state where the maximum strength is obtained, and the material has a small elongation and is easily cracked. For this reason, the region that becomes the non-heated portion in the partial solution treatment is very easily cracked during press molding, and the LDR in the moldability evaluation test is 0.1 as compared with the case where the partial solution treatment is not performed. It was confirmed that the moldability was not substantially improved without improvement.

  On the other hand, Condition 11, Condition 12, and Condition 13 are those after hot rolling under the conditions within the process condition range of the present invention as shown in Table 2 for Alloys 2, 3, and 4 within the component composition range of the present invention, respectively. This invention is also shown in Table 2 for the match money that was sub-aged by performing cold rolling, solution treatment and aging treatment (normal temperature aging or aging treatment combining normal temperature aging and artificial aging). In any case, the difference in tensile strength of the non-heated part at room temperature and the difference in yield strength of the heated part increased by 20 Mpa or more before and after the partial solution treatment. Yes. For this reason, in any case, it was confirmed that the LDR in the moldability evaluation test was improved by 0.1 or more compared to the case where the partial solution treatment was not performed, and the moldability was substantially improved. Moreover, it was confirmed that the bendability of the heated part is also good.

[Example 2]
The hot rolled sheet of alloy 1 in the component composition range of the present invention used in Example 1 was used as a test material. This alloy sheet was subjected to cold rolling, solution treatment and aging treatment under the same conditions as condition 3 shown in Table 2, and this alloy sheet was similarly subjected to partial solution treatment under the same conditions as condition 3. However, in Example 2, the partial solution treatment was performed by changing each region of the heated portion and the non-heated portion in the partial solution treatment as shown in Table 4. A blank subjected to partial solution treatment under each region condition was subjected to a cylindrical deep drawing test under the same conditions as in Example 1 after 1 day to obtain LDR, and the results are shown in Table 4.

  Condition 1, which is a comparative example, is an example in which there is no heating region, that is, a partial solution treatment is not substantially performed. In this case, the LDR was 2.01. Further, Condition 2 as a comparative example is an example in which the entire surface is a heated portion, and the LDR is only slightly increased to 2.02, and a sufficient moldability improvement effect cannot be obtained. Further, Condition 3 as a comparative example is an example in which all of the portions that contact the punch shoulder at the time of molding (region B in FIG. 2) and all of the outer portions (region A in FIG. 2) are heating portions. For this reason, it was found that the strength of the punch shoulder portion was lowered and breakage was likely to occur at this portion, the LDR was 2.01, and it did not increase effectively, and the moldability was not improved. Further, Condition 4 as a comparative example is an example in which a part (region B in FIG. 2) that contacts the punch shoulder at the time of molding and the entire outer part (region A in FIG. 2) are used as a heating unit. For this reason, it was found that the strength of the punch shoulder portion was lowered and breakage was likely to occur at this portion, the LDR was 2.02, and it did not increase effectively, and the moldability was not improved.

  On the other hand, Condition 5, which is an example of the present invention, is an example in which the entire outer portion (region A in FIG. 2) of the portion (region B in FIG. 2) that comes into contact with the punch shoulder during molding is used as the heating portion. In this case, the strength of the blank that comes in contact with the shoulder of the punch is higher than that of the outer portion, so that the LDR is 2.21, which is an effect of 0.1 or more compared with the case where the partial solution treatment is not performed. As a result, it was found that the moldability was improved. Further, Condition 6 and Condition 7, which are examples of the present invention, are examples in which a part of the outer portion of the portion (region B in FIG. 2) that comes into contact with the punch shoulder during molding is used as a heating portion. The strength of the blank that comes into contact with the shoulder is higher than that of a part of the outer portion, so that the LDR is 2.20 and 2.18, respectively, compared to the case where the partial solution treatment is not performed. It was confirmed that the moldability was effectively increased by 0.1 or more and the moldability was improved.

[Example 3]
The hot rolled sheet of alloy 1 in the component composition range of the present invention used in Example 1 was used as a test material. The alloy sheet was subjected to cold rolling, solution treatment, and aging treatment under the same conditions as condition 3 shown in Table 2, and further subjected to partial solution treatment under the same conditions as condition 3. However, in Example 3, the shape of the punch used for press molding was made different from that in each of the above examples. That is, as shown in FIG. 6, a two-stage cylindrical punch 2 having two-stage punch shoulder portions 3A and 3B is used. Here, the first stage of the punch 2 has a punch shoulder portion 3A having a size of φ50 mm and 5 mmR, and the second step of the punch 2 has a punch shoulder portion 3B having a size of φ25 mm and 5 mmR. Further, the die corresponds to the shape of the two-stage punch 2, and the disc blank 5 is press-formed with such a two-stage punch 2 and a die.

  At this time, as an example of the present invention, the region A outside the region B that will be in contact with the punch shoulder portion 3A on the one-step surface at the time of molding is used as the heating portion in the partial solution treatment, and further the region C inside the region B Of these, the outer region A ′ of the region B ′ that would be in contact with the punch shoulder 3B was also added as a heating portion to perform partial solution treatment. On the other hand, as a comparative example, the partial solution treatment was performed using only the region A outside the region B that would be in contact with the punch shoulder portion 3A on the one-step surface during molding as a heating part in the partial solution treatment. About the blank which performed these 2 types of partial solution treatment of this invention example and a comparative example, the press molding was performed using these punches and die | dyes 3 days after the partial solution treatment. As a result, in the example of the present invention, it was possible to produce a two-stage cylindrical molded product without breaking in the middle, but in the comparative example, the fracture occurred at a site corresponding to the punch shoulder 3B of the molded product. Oops.

In order to demonstrate the heating part and non-heating part at the time of performing a partial solution treatment according to the present invention, it is a schematic cross-sectional view showing the state of press forming of an aluminum alloy plate step by step. It is a schematic diagram for showing the heating part and the non-heating part at the time of the partial solution treatment in Example 1. 1 is a schematic perspective view of a partial solution treatment apparatus used in Example 1. FIG. 2 is a plan view showing the shape and dimensions of a tensile test piece collected in Example 1. FIG. In Example 1, it is a top view which shows the tensile test piece collection position from the heating part and non-heating part of the blank which performed the partial solution treatment. It is typical sectional drawing which shows the position of the heating part and non-heating part in the partial solution treatment with respect to the punch of 2 steps | paragraphs of the press used in Example 3, and the blank in that case.

Explanation of symbols

1 Die 2 Punch 3, 3A, 3B Punch shoulder 4 Wrinkle presser 5 Blank P Heating part Q Non-heating part

Claims (10)

  After subjecting the whole Al-Mg-Si alloy rolled sheet rolled to a predetermined sheet thickness to solution treatment, it is age-hardened to a sub-aged state. At the room temperature after solution treatment, the region other than the heating portion is determined as a non-heating portion, and the heating portion is partially subjected to a solution treatment to dissolve the aging precipitate and then rapidly cooled. The manufacturing method of the aluminum alloy plate for cold press forming characterized by making the intensity | strength of a heating part lower than the intensity | strength of a non-heating part. In the manufacturing method of the aluminum alloy plate for cold press forming of Claim 1,
As a treatment for obtaining a sub-aging state after subjecting the whole rolled sheet to a solution treatment, a normal temperature aging treatment for holding at a temperature within a range of 0 ° C. or higher and lower than 40 ° C. and a range of 40 ° C. or higher and lower than 180 ° C. A process for producing an aluminum alloy sheet for cold press forming, characterized in that either one of the artificial aging treatments held at a temperature of or a combination of both of them is performed.   Of the entire plate of the Al-Mg-Si alloy rolled plate that has been rolled to a predetermined plate thickness and is work hardened, a predetermined region is defined as a heating portion and a region other than the heating portion is defined as a non-heating portion. The strength of the heated portion at room temperature after solution treatment is lower than the strength of the non-heated portion by subjecting the heated portion to solution treatment partially to recover or recrystallize the processed structure and then rapidly cooling. A method for producing an aluminum alloy sheet for cold press forming, characterized by comprising: In the manufacturing method of the aluminum alloy plate for cold press forming in any one of Claims 1-3,
All or part of the portion outside the region where the punch shoulder is in contact during cold press forming is defined as the heating portion, and at least the punch shoulder portion is in the region other than the heating portion. A method for producing an aluminum alloy plate for cold press forming, wherein a portion to be pressed is defined as the non-heated portion. In the manufacturing method of the aluminum alloy plate for cold press forming in any one of Claims 1-4,
As the partial solution treatment, only the heating part except the non-heating part is heated to a temperature in the range of 480 ° C. or more and less than 580 ° C. and cooled to a temperature range of 50 ° C. or less at a cooling rate of 50 ° C./min or more. A method for producing an aluminum alloy plate for cold press forming. In the manufacturing method of the aluminum alloy plate for cold press forming according to any one of claims 1 to 5,
Cold press characterized in that the difference between the tensile strength of the non-heated part at room temperature after the partial solution treatment and the 0.2% proof stress of the heated part is increased by 20 MPa or more after the partial solution treatment. A method for producing an aluminum alloy sheet for forming. In the manufacturing method of the aluminum alloy plate for cold press forming of any one of Claims 1-6,
The heating part in the partial solution treatment includes a part of the aluminum alloy plate blank that is to be bent after forming out of the part outside the region where the punch shoulder is in contact during press forming. A method for producing an aluminum alloy plate for cold press forming. In the manufacturing method of the aluminum alloy plate for cold press forming of any one of Claims 1-6,
All regions inside the region where the punch shoulder portion of the aluminum alloy plate blank comes into contact with the heating portion in the partial solution treatment at the time of press forming, or one region or two regions or more in any shape in this region The manufacturing method of the aluminum alloy plate for cold press forming characterized by including these. In the manufacturing method of the aluminum alloy plate for cold press forming according to any one of claims 1 to 8,
As an Al-Mg-Si-based aluminum alloy plate, Mg 0.2-1.5% (mass%, the same shall apply hereinafter), Si 0.3-2.0%, and Fe 0.03-1.0%, Mn0 0.03-0.6%, Cr 0.01-0.4%, Zr 0.01-0.4%, V 0.01-0.4%, Ti 0.005-0.3%, Zn 0.03-2. A cold press characterized by using an aluminum alloy plate containing 5%, one or more selected from 0.01 to 1.5% of Cu and the balance being Al and inevitable impurities A method for producing an aluminum alloy sheet for forming.   A cold press forming method, wherein cold press forming is performed using the aluminum alloy plate obtained by the manufacturing method according to any one of claims 1 to 9.

Images