JP2023057912A - Aluminum alloy plate processing method - Google Patents

Abstract

To provide a hot stamp processing technology of an aluminum alloy plate containing Si.SOLUTION: An aluminum alloy plate processing method comprising: a heating step of holding an aluminum alloy plate made of an aluminum alloy containing Si of 5 wt.% or more and less than 11 wt.% at a temperature of 350°C or more and less than 580°C for a time period within 10 minutes; and a press step of supplying the aluminum alloy plate to a mold and cooling the aluminum alloy plate to 100°C or less at a bottom dead center of the pressing, wherein a thickness of the aluminum alloy plate is 1.5 mm or more and less than 5 mm.SELECTED DRAWING: Figure 1

Description

The present invention relates to an aluminum alloy plate processing method.

Aluminum (aluminum alloy) plate materials are effective as weight-reducing substitutes for steel plate products and the like, and are also used as automobile parts, for example. Aluminum plate materials are used for press products such as hoods, trunks, fenders, and doors. In addition, aluminum plate material is used for automotive internal products, such as heat exchanger parts (radiators, etc.) around the engine and heat insulators for heat dissipation. Other than these, aluminum sheet materials are rarely used for internal products. Aluminum sheets are much inferior to steel sheets in formability, and in order to obtain the same rigidity, they are required to be considerably thicker.

Aluminum alloy products include engine-related parts (aluminum casting products) and cases for consolidating control and functions (aluminum die-cast products). These products are made by pouring molten aluminum into molds, and specialize in complex shapes and integrated molding. The aluminum alloy used is a 4000 series Al-Si material, and the wrought material used for processing (1000 series, 2000 series, 3000 series, 5000 series, 6000 series, 7000 series) has the required material properties. is different. The fluidity of the molten metal is important for aluminum alloys for casting, and is characterized by a high Si content. A representative example of a cast alloy is AC4A, and a representative example of a die-cast alloy is ADC12. Casting technology excels in mass production regardless of whether it is large or small. However, for example, in addition to the problems caused by the die gast product (ADC12) and the casting product (internal material defects: shrinkage cavities, etc., dimensional accuracy: cutting required), the addition of Cu in the aluminum alloy (strength assurance) There is a problem such as deterioration of corrosion resistance accompanying.

On the other hand, in the automobile industry, electric vehicles (PHEV (Plug-in Hybrid Electric Vehicle), E
From the viewpoint of V (Electric Vehicle), automatic driving (equipped with various sensors), ensuring safety, etc., the use of multi-materials to reduce the weight of the entire vehicle is being promoted. Furthermore, in recent years, the promotion of carbon neutrality is required, and the origin of the material itself is also important. In other words, it is important whether new ingots, which consume a large amount of electric power in manufacturing, are used as materials, or recycled products, which do not consume a large amount of electric power, are used. In addition to the conventional press (cold) technology, the use of hot stamping technology is becoming more prominent for steel sheets, which account for the majority of vehicle body weight. Hot stamping technology is being applied especially to cabin structural parts (steel plate ultra-high-tensile steel) for passenger protection. However, although the hot stamping technology for aluminum alloy sheets is recognized as a prototype at the exhibition, none of them are envisioned for practical use.

JP 2008-92895 A JP 2016-211999 A Japanese Patent No. 5681631 JP-A-9-78210 Japanese Patent Application No. 2002-80887 JP-A-9-78210 Japanese Patent Application No. 6-203720

In the recent world situation, there is a demand for carbon-free materials for the purpose of preventing global warming. Many automobile parts require a large amount of energy at the stage of raw materials, materials and processing. CO2 emissions vary depending on the type of power generation (thermal power, hydraulic power, nuclear power, solar power, wind power, etc.), but in the future (after 2050), it is desirable to use renewable energy, and fossil fuels are the way to go. conversion becomes important. However, for the time being, it is necessary to promote recycling and reuse that are effective in reducing CO2 emissions from raw materials (materials), reduce the amount of fossil fuels used in manufacturing processes, and shorten processing and heat treatment times in parts manufacturing.

The aluminum materials in Japan are produced by using imported new aluminum ingots (7V ingots: 99.7% Al) to meet the needs of customers (composition, strength, etc.). Among them, beverage can stock and die casting ADC 12 are products that have been successfully recycled. Although materials for other uses are also recycled without waste, the ratio of new ingots used is high, so further improvement activities are required to reduce CO2.

By the way, in view of the carbon neutralization of aluminum materials in recent years (target for 2050), new aluminum ingots are produced with a huge amount of energy, and thus emit a large amount of CO2. Therefore, it is desirable to refrain from using new aluminum ingots. Promotion of recycling or reuse of aluminum products is very important. The reuse of aluminum products requires about 3% less energy than the production of new ingots.
and effective for future carbon neutralization.

Under such circumstances, the electrification of automobiles (especially EV (Electric Vehicle) and FCV (Fuel Cell Vehicle)) is expected to expand rapidly after 2030. On the other hand, the number of vehicles equipped with engines is expected to decrease sharply. Many of the engine parts of engine-equipped vehicles are made of aluminum castings, and the destination (usage and processing method) of aluminum castings (aluminum alloy castings) from scrapped engine-equipped vehicles is an issue for the future. In particular, aluminum castings are mainly 4000 series aluminum alloys with a large Si content (for example, 5% or more in weight ratio), and wrought materials (1000 series, 2000 series, 3000 series, 5000 series, 6000 series, 7000 series aluminum alloy) is difficult. If the wrought material is the same, it can be easily returned to the same kind of wrought material (component adjustment: scrap and a small amount of new ingot). When the casting material is returned to the wrought material, a method of diluting the Si component with a large amount of new ingot and wrought material waste is conceivable, and the effect of reducing CO2 is small. It is desirable to be able to use cast aluminum as a wrought material without using a large amount of new metal.

An object of the present invention is to provide a hot stamping technique for an aluminum alloy sheet containing Si.

In order to solve the above problems, the following means are adopted.
That is, the first aspect is
A heating step of holding an aluminum alloy plate made from an aluminum alloy containing Si at a weight ratio of 5% or more and less than 11% at a temperature of 350 ° C. or more and less than 580 ° C. for a time of 10 minutes or less;
A press working step of supplying the aluminum alloy plate to a mold and press working, and cooling the aluminum alloy plate to 100 ° C. or less at the bottom dead center of the press working,
The aluminum alloy plate has a thickness of 1.5 mm or more and less than 5 mm.
An aluminum alloy plate processing method.

According to the present invention, it is possible to provide a hot stamping technique for an aluminum alloy sheet containing Si.

FIG. 1 is a diagram showing a configuration example of a die of a press working apparatus. FIG. 2 is a diagram showing an example of cooling water channels 150 and thermocouple installation holes 160 provided in the lower die set 122 of the mold 100. As shown in FIG. FIG. 3 is a diagram showing a configuration example of a die of the press working device. FIG. 4 is a diagram showing an example of an operation flow of a method for hot stamping an aluminum alloy plate. FIG. 5 is a diagram showing the strength and formability of a 4000 series aluminum alloy plate and a 6000 series aluminum alloy plate. FIG. 6 is a diagram showing an example of strength characteristics of a 4000 series aluminum alloy plate and a 6000 series aluminum alloy plate due to aging treatment. FIG. 7 is a diagram showing an example of strength characteristics of a 4000 series aluminum alloy plate after short-time baking.

Embodiments will be described below with reference to the drawings. The configuration of the embodiment is an example, and the configuration of the invention is not limited to the specific configuration of the disclosed embodiment. In carrying out the invention, a specific configuration according to the embodiment may be adopted as appropriate.

[Embodiment]
(Configuration example)
FIG. 1 is a diagram showing a configuration example of a die of a press working apparatus. A mold 100 includes an upper mold 110 and a lower mold 120 . The upper mold 110 includes an upper mold die set 111 , an upper mold wrinkle holder 112 and a punch 113 . The lower die 120 includes a lower die wrinkle holding portion 121 and a lower die set 122 . Here, FIG. 1 is a diagram of the mold 100 viewed from the front. The direction from left to right in FIG. to the upper die set 111) is the z-direction. The upper die set 111 and the lower die set 122 are fixed to a press molding device. The upper die wrinkle holding portion 112 and the punch 113 are fixed to the upper die set 111 . The punch 113 deforms the aluminum alloy plate 200 to be processed into a predetermined shape. The shape of the tip of the punch 113 (on the side of the lower die 120) is, for example, a conical shape, a columnar shape, or an arbitrary shape. The upper die wrinkle suppressing part 112 and the lower die wrinkle suppressing part 121 suppress the occurrence of wrinkles in the aluminum alloy plate 200 to be processed. The lower die wrinkle holding portion 121 is fixed to the lower die set. The lower mold 120 is arranged to face the upper mold 110 . An aluminum alloy plate (test material) 200 to be processed is set on the lower die wrinkle holding portion 121 . The upper die set 111 has a thermocouple installation hole 140 for installing the thermocouple 310 . In addition, the lower die set 122 has a cooling water channel 150 through which a cooling coolant flows, and a thermocouple installation hole 160 for installing the thermocouple 320 . The cooling water channel 150 is provided with an inlet and an outlet, and a coolant such as water for cooling the mold 100 is introduced from the inlet and discharged from the outlet. A thermocouple 310 and a thermocouple 320 are installed in the thermocouple installation hole 140 and the thermocouple installation hole 160 to measure the temperature of the mold 100 . The material of the mold 100 is, for example, steel (tool steel, high-speed steel, super steel, etc.). Here, a wrinkle holding control mechanism for suppressing shrinkage flange deformation is not required. The configuration of mold 100 is not limited to that described herein.

The upper die 110 (or the lower die 120) reciprocates in the vertical direction between the top dead center and the bottom dead center due to the operation of the press working device, so that the upper die 110 and the lower die 120 approach or move away from each other. do. When the upper die 110 and the lower die 120 approach each other, the punch 113 is pressed against the aluminum alloy plate 200, and the aluminum alloy plate 200 is deformed and pressed. In addition, the press working apparatus includes a mold sprayer that turns water or a water-soluble lubricant into a mist and sprays it toward the upper mold 110 and the lower mold 120 of the mold 100 . The mold sprayer sprays a predetermined amount of water mist or water-soluble lubricant onto the upper mold 110 and the lower mold 120 before the aluminum alloy plate to be processed is set in the mold 100 .

In the drawing process (shrink flange deformation), the die 100 generally has a wrinkle holding control mechanism for controlling the wrinkle holding to be pressed against the aluminum alloy plate 200 by a spring or the like. However, if the wrinkle-holding control mechanism is used, the aluminum alloy plate 200 and the wrinkle-holding control mechanism may come into contact with each other during press working, lowering the temperature of the aluminum alloy plate 200 and causing deterioration in formability. Here, no wrinkle control mechanism is used. That is, the contact portion of the wrinkle holding portion 121 of the lower die 120 is reduced as much as possible, and the receiving shape of the punch 113 exists in the lower die 120 .

As a material for the mold 100, for example, aluminum alloy (eg, 5000 series, 7000 series), tool steel (eg, SKD61, etc.), high-speed steel, or steel such as super steel is used. 5000 series aluminum alloys are excellent in terms of cost. 7000 series aluminum alloys are excellent in terms of strength. The material of the mold 100 can be selected according to the required characteristics of the processed product. Aluminum alloys, tool steels, high-speed steels, and super steels may be used only for the surface layer portion (working surface) of the mold 100 . The surface of the mold 100 may be left as a polished surface, but in order to prevent adhesion of the aluminum alloy plate 200, a plating process such as high-hardness chromium plating or nickel plating is applied to the surface of the mold 100 to reduce friction. It is desirable to form a modulus coating. For example, electroless nickel plating with a film thickness of 5-10 μm is desirable. Methods of plating the mold 100 include electrolysis, electroless, thermal spraying, and the like. The mold 100 is an example of a steel mold. Steel materials such as tool steel, high-speed steel, and super steel have lower thermal conductivity than aluminum alloys, but are easy to process and low in cost.

Also, a spray atomizer for aluminum alloy plates is provided in the vicinity of the press working device. The aluminum alloy plate sprayer sprays a predetermined amount of water mist or a water-soluble lubricant onto the pressed aluminum alloy plate (molded product).

FIG. 2 is a diagram showing an example of cooling water channels 150 and thermocouple installation holes 160 provided in the lower die set 122 of the mold 100. As shown in FIG. The lower die set 122 has a cuboid shape. The cooling channel 150 has a first portion 151 , a second portion 152 and a third portion 153 .

In the example of FIG. 2, the right side surface of the lower die set 122 is provided with the inlet and outlet of the cooling water channel 150 and the thermocouple inlet. A first portion 151 of the cooling channel 150 is a cylindrical channel extending parallel to the x-direction from the inlet. The second portion 152 of the cooling channel 150 is a cylindrical channel that is connected to the end of the first portion 151 opposite to the inlet side end and extends parallel to the y-direction. The third portion 153 of the cooling channel 150 is a cylindrical channel connected to the end of the second portion 152 opposite to the end connected to the first portion 151 and extending in parallel to the x-direction to the outlet. For example, hoses and pipes are connected to the inlet and outlet of the cooling water channel 150 . A coolant such as water is introduced from the inlet of the cooling water channel 150, passes through the first portion 151, the second portion 152, and the third portion 153, and is discharged from the outlet, thereby cooling the lower die set 122. be. For example, hoses and pipes are connected to the inlet and outlet of the cooling water channel 150 . By cooling the lower die set 122, the lower die 120 including the lower die wrinkle holding portion 121 is cooled. Also, the upper mold 110 that contacts the lower mold 120 during pressing can be cooled. The diameter of the cooling channel 150 is, for example, 10 mm when the thickness (length in the z-direction) of the lower die set 122 is 50 mm.

The thermocouple installation hole 160 is a cylindrical hole extending parallel to the x-direction from a thermocouple insertion opening provided on the right side surface of the lower die set 122 . The thermocouple installation hole 160 extends to near the center of the lower die set 122 . A thermocouple 320 is inserted into the thermocouple installation hole 160 from a thermocouple insertion port. A temperature-measuring junction (a portion for measuring temperature) of the thermocouple 320 is arranged near the center of the lower die set 122 within the thermocouple installation hole 160 . The temperature of the lower die set 122 of the mold 100 can be measured by the thermocouple 320 inserted into the thermocouple installation hole 160 .

The shapes of the cooling water channel 150 and the thermocouple installation hole 160 are not limited to those described here, and may be appropriately changed according to the shape of the mold 100 and the like. Also, a plurality of cooling channels may be provided. Also, a plurality of thermocouple installation holes may be provided to measure the temperature at a plurality of positions. The thermocouple installation hole 160 and thermocouple 310 provided in the upper die set 111 are similar to the thermocouple installation hole 160 and thermocouple 320 provided in the lower die set 122 . Instead of the thermocouples 310 and 320, a thermistor, a resistance temperature detector, a thermocamera, or the like may be used to measure the temperature of the mold 100. FIG. The mold 100 is cooled by flowing the coolant through the cooling water channel 150, and the aluminum alloy plate 200 set in the mold 100 is cooled.

FIG. 3 is a diagram showing a configuration example of a die of the press working device. In the mold 100 of FIG. 3, the upper die set 111 is provided with cooling water channels 130 similar to the cooling water channels 150 of the lower die set 122 . Other configurations of the mold 100 of FIG. 3 are the same as those of the mold 100 of FIG. By providing cooling water channels in the upper die set 111 and the lower die set 122, the mold 100 can be cooled more appropriately. The amount of refrigerant flowing through cooling waterway 130 is the same as the amount of refrigerant flowing through cooling waterway 150 .

(Manufacturing method of aluminum alloy plate)
Here, a method for manufacturing an aluminum alloy plate used in the hot stamping method of this embodiment will be described. The raw material for the aluminum alloy plate used here is, for example, a scrap of casting (casting product) made of a 4000 series aluminum alloy. Aluminum alloy castings are made by pouring an aluminum alloy melted at a high temperature into a mold cavity and then cooling and hardening it.

A 4000 series aluminum alloy (Al—Si series alloy) is an aluminum alloy in which silicon (Si) is mainly added to aluminum. The 4000 series aluminum alloy used here is, for example, an aluminum alloy containing Si in an amount of 5% or more and less than 11% by weight. Aluminum alloys containing less than 5% of Si are less likely to have precipitation hardening due to the Al--Mg--Si system and the Al--Cu--Mg--Si system in addition to the solid solution strengthening of the Si additive component. Aluminum alloys containing 11% or more of Si have low rollability, and are prone to edge cracks and rolling fractures. Therefore, an aluminum alloy containing 5% or more and less than 11% of Si is preferable in terms of rollability and strength characteristics when made into an aluminum alloy sheet. In addition, the 4000 series aluminum alloy used here contains, for example, Si of 5% or more and less than 11%, Mn of less than 0.6%, Mg of less than 0.6%, and Cu of less than 2.0% by weight. It may be an aluminum alloy containing. In addition, the 4000 series aluminum alloy used here includes, for example, Si of 5% or more and less than 11%, Mn of 0.2% or more and less than 0.6%, and 0.2% or more and less than 0.6% by weight. of Mg and 0.05% or more and less than 2.0% of Cu. Mn and Mg contribute to improving the strength of the aluminum alloy. If the amount of Mn or Mg is less than 0.2%, the strength improvement effect is small. When the amount of Mn or Mg is 0.6% or more, the formation of Al--Mn-based and Al--Fe--Mn--Mg-based compounds and macro-compounds is accelerated, and cracking during working is accelerated. Therefore, 0.2% or more and less than 0.6% of Mn and 0.2% or more and less than 0.6% of Mg are preferable. Cu is an element particularly effective in improving strength. If Cu is less than 0.05%, the strength improvement effect is small. A Cu content of 2.0% or more results in a decrease in corrosion resistance, excessive promotion of cracking susceptibility, and delayed fracture after forming. Therefore, 0.05% or more and less than 2.0% of Cu is preferable. The 4000 series aluminum alloy is not limited to this. Each aluminum alloy may contain elements other than those shown here. For example, Fe, Zn, Ti, etc. may be included. Fe, Zn, Ti and the like are allowed as long as they do not adversely affect formability. For example, Fe is made less than 0.3% in order to prevent deterioration of moldability due to the formation of Al--Fe-based giant compounds. Zn is controlled to be less than 0.5% in order to suppress precipitation hardening due to Al--Zn--Mg-based precipitates and to prevent stress corrosion cracking. Ti should be less than 0.10% to reduce the nucleation of large compound formation. JIS component standards for aluminum alloy castings include AC1B to AC9B depending on the application. These are examples of 4000 series aluminum alloys.

A slab is produced by melting and casting a raw material aluminum alloy (for example, a cast product of a 4000 series aluminum alloy). At this time, degassing treatment and inclusion removal treatment are performed. The degassing process is a process for removing hydrogen gas and the like contained in the molten aluminum alloy. The inclusion removal treatment is a treatment for removing inclusions such as oxides, carbides and nitrides contained in the molten metal. When inclusions are contained in the molten metal, problems such as deterioration of castability occur. In addition, a segregation removal treatment is performed on the cast slab. The segregation removing treatment is a treatment for removing non-homogeneous segregation generated during casting from the slab. Also, during casting, P or Na may be added in an amount less than 100 ppm. Addition of P or Na refines the cast structure of the aluminum alloy.

Next, a homogenization heat treatment is performed at a temperature of 400° C. or more and less than 530° C. on the slab that has been subjected to the segregation removal treatment. Homogenization heat treatment is a process that eliminates the uneven distribution of atoms in the slab obtained by casting. Homogenization heat treatment at less than 400° C. leaves the cast structure, causing edge cracks during hot rolling and deterioration of formability during cold rolling. In the homogenization heat treatment at 530° C. or higher, burning occurs on the slab surface, and surface defects such as seizure occur on the surface of the aluminum alloy plate. Therefore, the homogenization heat treatment is preferably performed at a temperature of 400°C or more and less than 530°C. Furthermore, the slab subjected to the homogenization heat treatment becomes a hot coil having a plate thickness of 2 mm or more and less than 8 mm by hot rolling. A hot coil is obtained by coiling an aluminum alloy plate produced by hot rolling. At this time, the winding temperature is 300°C or higher and lower than 400°C. If the plate thickness is less than 2 mm, the inner and outer surfaces rub against each other during winding, causing scratches. A plate thickness of 8 mm or more causes flaws due to winding looseness. Therefore, the plate thickness of the hot coil is preferably 2 mm or more and less than 8 mm. If the winding temperature is less than 300°C, recrystallization is insufficient. At a coiling temperature of 400° C. or higher, the solid-solution strengthening increases, resulting in a change in deformation resistance. Inappropriate winding temperature causes a change in deformation resistance and causes defects. Therefore, the winding temperature is preferably 300°C or higher and lower than 400°C.

After that, roughening is performed at 300° C. or more and less than 400° C., and an aluminum alloy plate having a thickness of 1.5 mm or more and less than 5 mm is manufactured by cold rolling. The cold rolling process is performed, for example, at room temperature (for example, 0° C. or more and less than 150° C.). The cold rolling process is performed at a lower temperature than the hot rolling process. Roughing leads to prevention of ear (end) cracking during cold rolling. Roughening is suitably performed at a temperature of 300° C. or more and less than 400° C. as a temperature for softening the aluminum alloy plate. For example, if the hot rolling temperature is above 300°C, roughing may not be performed. After the cold rolling treatment, finish annealing at 330° C. or more and less than 400° C. and strain correction may be performed. By performing the finish annealing at 330°C or more and less than 400°C, the strength of the aluminum alloy plate is stabilized and the residual stress is reduced.

(Operation example)
FIG. 4 is a diagram showing an example of an operation flow of a method for hot stamping an aluminum alloy plate. An aluminum alloy plate is an aluminum alloy plate to be processed. The aluminum alloy plate is, for example, a 4000 series aluminum alloy plate manufactured by the method described above. Here, an aluminum alloy plate is processed into a cut plate of a suitable size for press working. Here, it is assumed that the mold 100 is set in the press working device, and the cooling water channel 150 of the mold 100 is supplied with a coolant. It is assumed that cooling water passage 150 is supplied with water as a refrigerant in an amount of 3 L (liter)/minute to 15 L/minute. If the mold 100 is an aluminum alloy, for example, a supply rate of 3 L/min-10 L/min is appropriate. If the mold 100 is a steel material such as tool steel, for example, a supply rate of 7 L/min-15 L/min is appropriate. During press working, the internal temperature and surface temperature of the mold 100 are maintained at 100° C. or less by the coolant. The amount of coolant supplied to the cooling channel 150 is adjusted according to the temperature of the mold 100 measured by the thermocouples 310 and 320 so that the internal temperature and surface temperature of the mold 100 are 100° C. or less. may be adjusted. If the temperature exceeds 100° C., the amount of solid solution Si, Mg, and Cu decreases in the aluminum alloy plate 200 to be processed, and the cooling time of the aluminum alloy plate 200 becomes longer, resulting in lower productivity. For example, the higher the temperature measured by the thermocouples 310 and 320, the greater the amount of coolant supplied to the cooling water passage 150. FIG. When the mold 100 is sufficiently cooled by mist spraying, cooling by the cooling water passage 150 may not be performed.

In S101, a heating furnace such as an electric heater furnace (an electric furnace), an induction heating furnace, or an infrared heating furnace is used to hold the aluminum alloy plate 200 to be processed at a temperature of 450° C. or more and less than 560° C. for less than 10 minutes. Heat up in time. That is, after raising the temperature of the aluminum alloy plate 200 to the target temperature in the heating furnace, the aluminum alloy plate 200 is further heated at the target temperature for a holding time of less than 10 minutes. During heating, it is desirable that the temperature difference between the respective positions in the aluminum alloy plate 200 is within 40°C at maximum. Moreover, it is desirable that the heating rate is 50° C./min or more during heating. The heating rate affects the material structure (crystal grains), and if it is less than 50° C./min, it leads to a decrease in formability due to grain growth, a rough surface on the processed surface, and a decrease in productivity. On the other hand, if the width of the temperature distribution in the material is wide, the strength variation becomes large. Moreover, the thickness of the aluminum alloy plate is, for example, 1.5 mm or more and less than 5 mm. The ultimate temperature can be changed depending on the type of aluminum alloy.

The temperature reached is preferably 450°C-560°C. If the ultimate temperature is less than 450° C., solid solution of the additive components in the aluminum alloy plate is insufficient, and it is difficult to increase the strength. Also, if the temperature reaches 560° C. or higher, burning (surface dissolution) occurs due to alloying elements, which is not preferable. The holding time at the reached temperature may be 60 minutes or more, but if the holding time at the reached temperature is long, the productivity will drop significantly, so the holding time at the reached temperature is preferably less than 60 minutes. In particular, when the temperature reached is 500° C.-560° C., the holding time is preferably shorter, and even within 10 minutes is sufficient. In addition, when the reaching temperature is 500° C.-560° C., it contributes to the improvement of moldability and strength. A shorter holding time contributes to improved productivity and energy saving. Moreover, when the thickness of the aluminum alloy plate is thin (for example, less than 3 mm), the holding time at the reached temperature may be less than 1 minute without any problem, and it is desirable to make it as short as possible. If the thickness of the aluminum alloy plate is less than 1.5 mm, it is not preferable because it is likely to be deformed during transportation. Also, even if the thickness of the aluminum alloy plate is 5 mm or more, the processing is possible, but other methods such as extrusion are more convenient. In addition, if the thickness of the aluminum alloy plate is 5 mm or more, it takes time to heat before press working and to cool after press work, resulting in a decrease in productivity. Therefore, the thickness of the aluminum alloy plate 200 here is preferably 1.5 mm or more and less than 5 mm.

In S<b>102 , the mold sprayer of the press machine sprays water or a water-soluble lubricant in the form of mist toward the upper mold 110 and the lower mold 120 of the mold 100 . The mold sprayer sprays water or a water-soluble lubricant in the form of mist in an amount of 10 mg or more per 100 cm ² of area of the aluminum alloy plate 200 to be processed to the upper mold 110 and the lower mold 120 . Mist water or water-soluble lubricant is sprayed by the mold sprayer before the aluminum alloy plate 200 to be processed is set in the mold 100 . If the spray amount is less than 10 mg per 100 cm ² area of the aluminum alloy plate 200 to be processed, the cooling capacity and lubricating performance are insufficient, causing adhesion of the aluminum alloy plate 200 to the mold 100 . Further, when the spray amount is 3000 mg or more per 100 cm ² of the area of the aluminum alloy plate 200 to be processed, the mold 100 is sufficiently cooled, but the water or water-soluble lubricant becomes excessive. Excess water or water-soluble lubricant in the mold 100 requires draining work to remove the liquid (water or water-soluble lubricant) from the mold 100, resulting in deterioration of workability and quality. Also, an excessive amount of spray causes unevenness in strength due to temperature unevenness in the aluminum alloy plate 200 . Therefore, the spray amount is preferably 10 mg or more and less than 3000 mg per 100 cm ² area of the aluminum alloy plate 200 to be processed. For example, when sufficient cooling is obtained in the cooled mold 100, cooling by mist spray may not be performed. Spraying mist by the mold sprayer is effective for cooling the aluminum alloy plate 200 . It is preferable to increase the spray amount as the plate thickness of the aluminum alloy plate 200 increases.

In S103, the aluminum alloy plate 200 heated in S101 is taken out from the heating furnace and quickly (for example, within 5 seconds) is set on the lower mold wrinkle holder 121 of the mold 100 of the press machine. Taking out the aluminum alloy plate from the heating furnace and setting it in the mold 100 is performed by, for example, a well-known robot or the like. The robot has, for example, an arm that grips the aluminum alloy plate 200 , takes out the aluminum alloy plate 200 heated for a predetermined time from the heating furnace, and moves it to the mold 100 . Further, the robot may take out the pressed aluminum alloy plate 200 from the mold 100 .

In S104, in the press machine, the upper die 110 of the die 100 is moved to the bottom dead center, and the punch 113 and the upper die wrinkle holding portion 112 are brought into contact with the aluminum alloy plate 200, so that the aluminum alloy plate 200 is pressed to a predetermined level. deformed (pressed) into the shape of Here, it is preferable that the height of the drawn product after processing into the aluminum alloy plate 200 is less than 40 mm. Since the wrinkle holding control mechanism is not used here, when the height of the molded product is 40 mm or more, insufficient material flow occurs due to wrinkles in the flange portion. Here, the height of the molded product obtained by shrink flanging means, for example, the dimension of the processed product in the molding direction, that is, in the press direction after working in press working. Therefore, if the height of the molded product is 40 mm or more, constriction or the like may appear in the molded product, and the product performance may not be satisfied.

In S105, the upper mold 110 of the mold 100 is maintained at the bottom dead center, and the aluminum alloy plate 200 is cooled to 200° C. or less. For example, the aluminum alloy plate 200 is cooled to 100° C. or less by maintaining the upper die 110 at the bottom dead center for 1 to 5 seconds (bottom dead center holding time of 1 to 5 seconds). If the bottom dead center holding time is less than 1 second, it is difficult to cool the aluminum alloy plate 200 to 100° C. or lower. If the bottom dead center holding time exceeds 5 seconds, the productivity is poor. Since the mold 100 is cooled in advance by water cooling or the like, the aluminum alloy plate 200 sandwiched between the upper mold 110 and the lower mold 120 of the mold 100 is also cooled. If the temperature of the aluminum alloy plate 200 exceeds 100° C., the additional elements that increase the strength are precipitated, making it impossible to ensure high strength, and the deformation of the molded product is likely to occur. In addition, by cooling the aluminum alloy plate 200 to 100 ° C. or less, the temperature difference (thermal contraction rate) between the ultimate temperature of the aluminum alloy plate 200 and the cooling temperature at the bottom dead center can be used to improve the flatness of the molded product. and the releasability from the mold 100 can be improved. The temperature of the aluminum alloy plate 200 is lowered by contact with the mold 100, and the temperature difference imparts tension to the aluminum alloy plate 200, contributing to improvement in flatness. The lower the temperature at the bottom dead center, the better. On the other hand, heat shrinkage causes the aluminum alloy plate 200 to stick to the punch 113 side, making release difficult. Therefore, it is preferable to reduce the tension by optimizing the ultimate temperature of the aluminum alloy plate 200 . In addition, if there is a shape that is difficult to release from the aluminum alloy plate 200 even with measures against heat shrinkage, for example, the punch 113 on the convex side of the mold 100
It is effective to provide a clearance angle of several degrees (for example, 1 to 3 degrees) on the side and to reduce the deformation resistance during processing. Deformation resistance is seizure. Deformation resistance is reduced by appropriately combining plating (for example, nickel plating, chromium plating) on the mold 100 and applying a water-soluble coolant (lubricant). Known release agents can be used as lubricants. Plating the mold 100 can reduce the coefficient of friction between the mold 100 and the aluminum alloy plate 200 . The dimensional accuracy (flatness, etc.) of the molded product can be improved by providing the mold 100 with a convex clearance angle, plating, and the like. In addition, the dimensional accuracy of the molded product can be improved by the forced separation method. In the forced detachment method, a force is applied to a part of the molded product (aluminum alloy plate 200) by a mechanical method (knockout bar, stripper, etc.) to the extent that the molded product (aluminum alloy plate 200) is not deformed. This is a method of separating the aluminum alloy plate 200).

In S106, the aluminum alloy plate 200 is heated to a temperature of 190° C. or more and less than 250° C. for 5 minutes or more and 60 minutes or less using a heating furnace such as an electric heater furnace (an electric furnace), an induction heating furnace, or an infrared heating furnace. Baking process is performed for a short period of time. That is, after raising the temperature of the aluminum alloy plate 200 to the target temperature in the heating furnace, the aluminum alloy plate 200 is further heated at the target temperature for a holding time of 5 minutes or more and 60 minutes or less. If the temperature is less than 190°C, the precipitation hardening is insufficient, and if the temperature is 250°C or more, the precipitates become large and the precipitation hardening is reduced. Therefore, the short-time baking treatment is preferably performed at 190°C or higher and lower than 250°C. Also, instead of the short-time baking process, a long-time baking process may be performed. The long-time baking treatment is performed on the aluminum alloy plate 200 by a heating furnace such as an electric heater furnace (an electric furnace), an induction heating furnace, and an infrared heating furnace, for example, at a temperature of 150° C. or more and less than 180° C. for 5 hours or more. Heat with a hold time of less than 20 hours (eg 170° C., 8 hours). The temperature and time for the long-term baking treatment are not limited to those described here, as long as they are determined as conditions for reliably obtaining the desired strength. Short-time baking treatment and long-time baking treatment are examples of artificial aging treatment. The treatment of S106 may be performed after other treatments (cold press such as trimming, piercing, restrike, etc.) after the aluminum alloy plate 200 is treated in S101 to S105. Further, the treatment of S106 may be maintained at 100° C.-200° C. after the treatment of the aluminum alloy plate 200 of S101 to S105. This promotes high strength in the artificial aging treatment. Also, natural aging (leaving at room temperature (about 25° C.)) may be performed instead of the artificial aging treatment.

(Example 1)
FIG. 5 is a diagram showing the strength and formability of a 4000 series aluminum alloy plate and a 6000 series aluminum alloy plate. Here, as a 4000-series aluminum alloy plate, a cast part scrap (Al-8.9% Si-0.1% Cu-0.4% Mn-0.5% Mg) by AC4A is melt-cast and 480 After homogenization heat treatment at ℃, hot rolling treatment, cold rolling treatment and final annealing at 350 ℃ are performed to produce an aluminum alloy plate with a thickness of 2 mm. A 6022-T4 material is used as the 6000 series aluminum alloy plate. Here, the produced 2 mm thick 4000 series aluminum alloy plate (AC4A material) and the 2 mm thick 6000 series aluminum alloy plate (6022-T4 material), tensile strength, proof stress, elongation, Erichsen value, critical drawing ratio Compare LDR.

The AC4A material is inferior to the 6022-T4 material in strength and yield strength. Also, the AC4A material has a lower elongation rate and Erichsen value than the 6022-T4 material. On the other hand, the AC4A material and the 6022-T4 material have the same critical drawing ratio LDR. This is due to the influence of the material structure (crystal grain, eutectic structure, etc.). The drawability of the two materials is the same due to the contribution of improved shrink flangeability (wrinkle suppression) due to the low strength of the AC4A scrap material. Therefore, if the strength of the AC4A material is equivalent to that of the 6022-T4 material, the formability of the AC4A material is inferior.

(Example 2)
Here, using test materials of AC4A material and 6022-T4 material of Example 1, molding tests by cold pressing and the above-described hot stamping method for automotive ECU cases are carried out. In the cold press, both test materials cracked 10 mm before the bottom dead center. The degree of cracking is greater in the AC4A material than in the 6022-T4 material. On the other hand, in the above hot stamping method (reaching temperature of 550 ° C., water-soluble lubricant application, water cooling mold, bottom dead center holding time of 2 seconds), cracks do not occur in both test materials, and the moldability is good. .

(Example 3)
FIG. 6 is a diagram showing an example of strength characteristics of a 4000 series aluminum alloy plate and a 6000 series aluminum alloy plate due to aging treatment. Here, assuming hot stamping, the AC4A material and 6022-T4 material test material (JIS No. 5 test piece) of Example 1 are solution treated at 550 ° C., water cooled, and then naturally aged. Treatment (2 weeks, left at room temperature) or artificial aging treatment (long-term baking treatment, 170° C. for 8 hours) is performed. Tensile strength, yield strength, and elongation are measured for each test material. A test material obtained by subjecting the AC4A material to artificial aging treatment has a high strength comparable to that of a steel plate (high tensile strength steel). The test material obtained by subjecting the AC4A material to artificial aging treatment has higher strength than the test material obtained by subjecting the 6022-T4 material to artificial aging treatment. The AC4A material is a 4000 series aluminum alloy and belongs to non-heat-treated alloys. It is said that non-heat-treated alloys basically do not exhibit precipitation hardening behavior. is obtained. In particular, the test material obtained by subjecting the AC4A material to artificial aging treatment has a higher strength than the test material obtained by subjecting the 6022-T4 material used as a panel material for automobiles to artificial aging treatment.

(Example 4)
FIG. 7 is a diagram showing an example of strength characteristics of a 4000 series aluminum alloy plate after short-time baking. Here, assuming hot stamping, the AC4A material test material (JIS No. 5 test piece) of Example 1 is subjected to solution treatment at 550 ° C., water cooling, and artificial aging treatment (short-time baking process). Tensile strength, yield strength, and elongation are measured for test materials that have been subjected to artificial aging treatment. The baking conditions for the short-time baking treatment are 180° C. for 20 minutes, 200° C. for 20 minutes, 220° C. for 20 minutes, 240° C. for 20 minutes, and 260° C. for 20 minutes. Here, a tensile strength of 320 MPa or more and a yield strength of 250 MPa or more are considered acceptable. When the baking temperature is 200° C., 220° C., and 240° C., the tensile strength is 320 MPa or more. Moreover, when the baking temperature is 180° C. and 260° C., the tensile strength is less than 320 MPa. Moreover, when the baking temperature is 200° C., 220° C., and 240° C., the yield strength is 250 MPa or more. Also, when the baking temperature is 180° C. and 260° C., the yield strength is less than 250 MPa. Therefore, when the baking time is 20 minutes, the baking temperature is preferably 190°C or higher and lower than 250°C. In addition, the elongation rate is 8% or more under each condition, and an elongation rate of 8% or more is a sufficient value. The tensile strength of the test material is 365 MPa under the baking conditions of 200° C. and 20 minutes for the short-time baking treatment. The tensile strength of 365 MPa corresponds to 96% of the tensile strength of 380 MPa of the long-time baking treatment (8 hours at 170° C.) of the AC4A test material of Example 3. By performing the short-time baking treatment in this manner, it is possible to obtain an aluminum alloy plate having strength equivalent to that obtained by the long-time baking treatment. By performing the short-time baking treatment, it is possible to obtain an aluminum alloy plate equivalent to the long-time baking treatment with less energy consumption than the long-time baking treatment.

(Action and effect of embodiment)
In the present embodiment, an aluminum alloy plate of a 4000 series aluminum alloy is produced using a casting product of an aluminum alloy such as a 4000 series aluminum alloy as a raw material. At this time, for example, a slab is produced by melting and casting a scrap material of an aluminum alloy cast product. At this time, degassing treatment and inclusion removal treatment are performed. Further, the cast slab is subjected to segregation removing treatment. Also, during casting, P or Na may be added in an amount less than 100 ppm. Addition of P or Na refines the cast structure of the aluminum alloy. Next, a homogenization heat treatment is performed at a temperature of 400° C. or more and less than 530° C. on the slab that has been subjected to the segregation removal treatment. Furthermore, the slab subjected to the homogenization heat treatment becomes a hot coil having a plate thickness of 2 mm or more and less than 8 mm by hot rolling. At this time, the winding temperature is 300°C or higher and lower than 400°C. Furthermore, roughening is performed at 300° C. or more and less than 400° C., and an aluminum alloy plate having a thickness of 1.5 mm or more and less than 5 mm is manufactured by cold rolling. Hot stamping is performed on the aluminum alloy plate 200 .

In the method of hot stamping an aluminum alloy plate according to the present embodiment, the aluminum alloy plate 200 is heated in a heating furnace to reach a temperature of 450° C. or more and less than 560° C. for a holding time of less than 10 minutes. The mold 100 is a mold made of aluminum alloy, tool steel, high-speed steel, super steel, or the like. The mold 100 is cooled by the coolant flowing through the cooling water channel 150 . Also, the mold 100 is cooled by mist spraying. The heated aluminum alloy plate 200 is taken out from the heating furnace, set in the mold 100, and pressed. During press working, the aluminum alloy plate 200 is cooled to 100° C. or less at the bottom dead center of the die 100 . As a result, Si, Mg, and Cu, which contribute to strength, can be solid-dissolved. According to the hot stamping method for the aluminum alloy plate of the present embodiment, the formability of the aluminum alloy can be improved, a shape that has been difficult to form is possible, and the number of mold steps can be reduced. By cooling the mold 100, the temperature of the mold 100 can be reduced to less than 100°C. By cooling the mold 100, the aluminum alloy plate 200 to be processed can be cooled. By subjecting the pressed aluminum alloy plate 200 to a short-time baking treatment, the strength of the aluminum alloy plate 200 can be increased (tensile strength of 320 MPa or more). By introducing a coolant into the mold 100 and spraying mist, the aluminum alloy plate can be cooled to a predetermined temperature. Also, by cooling the aluminum alloy plate 200 to 100° C. or less, a molded article having excellent shape fixability and flatness can be produced. Direct water cooling of the aluminum alloy plate after press working can be omitted by cooling with a cooling water channel and mist spraying. By not directly cooling with water, it is possible to suppress the decrease in press speed, the complication of the mold shape, and the complication of the working process. Thereby, the productivity and simplicity of the press working process can be improved.

The method of hot stamping an aluminum alloy plate according to the present embodiment can realize a pressed product of a 4000 series Al—Si alloy containing a large amount of Si. According to the present embodiment, it is possible to manufacture a pressed product from a 4000 series aluminum alloy having a strength equivalent to that of a 6000 series aluminum alloy. According to the present embodiment, by producing an aluminum alloy plate using a cast product of a 4000 series aluminum alloy as a raw material and producing a pressed product, compared to the case of producing a pressed product using a new aluminum ingot, Energy consumption can be reduced. By reducing energy consumption, it is possible to reduce CO2 emissions.

Each of the above embodiments can be implemented in combination as much as possible.

100 Mold 110 Upper mold 111 Upper mold die set 112 Upper mold wrinkle holding part 113 Punch 120 Lower mold 121 Lower mold wrinkle holding part 122 Lower mold die set 130 Cooling channel 140 Thermocouple installation hole 150 Cooling channel 151 First part 152 Second Second part 153 Third part 160 Thermocouple installation hole 200 Aluminum alloy plate 310 Thermocouple 320 Thermocouple

Claims (10)

A heating step of holding an aluminum alloy plate made from an aluminum alloy containing Si at a weight ratio of 5% or more and less than 11% at a temperature of 350 ° C. or more and less than 580 ° C. for a time of 10 minutes or less;
A press working step of supplying the aluminum alloy plate to a mold and press working, and cooling the aluminum alloy plate to 100 ° C. or less at the bottom dead center of the press working,
The aluminum alloy plate has a thickness of 1.5 mm or more and less than 5 mm.
Aluminum alloy plate processing method. A heating step of holding an aluminum alloy plate made from an aluminum alloy casting at a temperature of 350° C. or more and less than 580° C. for a time of 10 minutes or less;
A press working step of supplying the aluminum alloy plate to a mold and press working, and cooling the aluminum alloy plate to 100 ° C. or less at the bottom dead center of the press working,
The aluminum alloy plate has a thickness of 1.5 mm or more and less than 5 mm.
Aluminum alloy plate processing method. The aluminum alloy plate contains, by weight, 5% or more and less than 11% Si, 0.2% or more and less than 0.6% Mg, and 0.01% or more and less than 2.0% Cu.
The aluminum alloy plate processing method according to claim 1 or 2. The aluminum alloy plate is added with less than 100 ppm of P or less than 100 ppm of Na,
The aluminum alloy plate processing method according to claim 3. The aluminum alloy plate is obtained by melting and casting the aluminum alloy, homogenizing heat treatment at a temperature of 400 ° C. or higher and lower than 530 ° C., and hot rolling to a thickness of 2 mm or higher and lower than 8 mm at a temperature of 300 ° C. or higher and lower than 400 ° C. Manufactured by performing a cold rolling process to a thickness of 1.5 mm or more and less than 5 mm,
The aluminum alloy plate processing method according to any one of claims 1 to 4. A spraying step of spraying a mist of water or a water-soluble lubricant onto the mold in an amount of 10 mg or more and less than 3000 mg per 100 cm ² of the aluminum alloy plate area,
The bottom dead center holding time in the pressing step is 1 second or more and less than 5 seconds,
The aluminum alloy plate processing method according to any one of claims 1 to 5. After the pressing step, a baking step of holding the aluminum alloy plate at a temperature of 190 ° C. or more and less than 250 ° C. for 5 minutes or more and 60 minutes or less,
The aluminum alloy plate processing method according to any one of claims 1 to 6. After the pressing step, a baking step of holding the aluminum alloy plate at a temperature of 150 ° C. or more and less than 180 ° C. for 5 hours or more and 20 hours or less,
The aluminum alloy plate processing method according to any one of claims 1 to 6. The mold has a relief angle on the convex side or is plated,
The aluminum alloy plate processing method according to any one of claims 1 to 8. After the pressing step, a separating step of applying a force to a part of the aluminum alloy plate to remove the aluminum alloy plate from the mold,
The aluminum alloy plate processing method according to any one of claims 1 to 9.

Images