WO2005068678A1

WO2005068678A1 - Heat treatment method for aluminum die-cast product

Info

Publication number: WO2005068678A1
Application number: PCT/JP2005/000355
Authority: WO
Inventors: Jo Asada; Nobuhiro Miyamoto
Original assignee: Ryobi Ltd.
Priority date: 2004-01-15
Filing date: 2005-01-14
Publication date: 2005-07-28
Also published as: JP2005200702A

Abstract

In a heat treatment method for an aluminum die-cast product, a solution treatment process, a cooling process, a quenching process, and an aging process are performed, in that order. In the solution treatment process, a large number of aluminum die-cast products are subjected to a solution treatment. In the cooling process, the temperature of the aluminum products is cooled to below 450°C after the solution treatment process by using an intermediate furnace. In the quenching process, the aluminum die-cast products are quenched within 120 seconds after the solution treatment process. In the aging process, an artificial aging treatment is applied to the large number of the aluminum die-cast products came out through the quenching process. The heat treatment process described above for an aluminum die-cast product does not require large-scale facilities and is capable of producing die-cast products excellent in mass-productivity and capable of achieving high dimensional accuracy and strength.

Description

Specification

Heat treatment method for aluminum die cast products

Technical field

The present invention relates to a method for heat-treating an aluminum die-cast product, and more particularly to a method for heat-treating an aluminum die-cast product that suppresses the occurrence of heat treatment distortion in T6 treatment. Background art

[0002] In recent years, in order to reduce the weight of transportation means such as cars, the replacement of body frames conventionally made of steel materials with aluminum alloys has been progressing. When aluminum alloys are roughly classified, they are divided into wrought alloys and metal alloys. However, if they are roughly classified based on the properties of aluminum alloys, they can be classified into non-heat-treated alloys and heat-treated alloys. Heat-treatable alloys are age-hardenable alloys.Aging-hardenable alloys are heat treated at a temperature above the solid solubility limit and then quenched to bring the homogeneous state to room temperature. One that is left to stand at room temperature to cure by natural aging (T4 treatment), and one that obtains high hardness by quenching and then tempering at an appropriate temperature of 100 ° C-200 ° C for an appropriate time (T6 Processing).

[0003] Since the body frame of the vehicle is a structural material, it is required to have strength and ductility. For this reason, the body frame is made by extruding a 6000 series aluminum alloy, or by pressing a pressed material and an A1-Si-Mg alloy such as AC4CH alloy by rivets or welding. Can be The members constituting the vehicle body frame are generally subjected to the above-described T4 treatment or T6 treatment in order to improve the mechanical properties.

[0004] On the other hand, the die casting method is suitable for mass-producing components having complicated shapes at low cost.

For this reason, the above-mentioned extruded die, and the body frame, which had been manufactured by bonding the pressed materials ゃ and 铸 to each other, were integrally molded by the die casting method. Thus, the cost can be significantly reduced. In the die casting method, an A1-Si-Mg alloy represented by ADC3 is generally used. These alloys, when subjected to T4 or T6 treatment in the same manner as AC4CH alloy, can satisfy the mechanical properties required for the body frame for the first time. [0005] A product formed by the usual die casting method contains a large amount of gas inside, and when the product is heated to a high temperature, a large number of protrusions are generated on the surface of the product due to expansion of the gas, resulting in a defective product. . Therefore, in order to perform the above T4 or T6 treatment, a special die casting method that controls the amount of gas contained in the product is required. As such a die casting method, there are a vacuum die casting method in which the inside of the mold cavity is evacuated and depressurized, and a non-porous die casting method in which the air in the cavity is replaced with oxygen.

[0006] A body frame using the die casting method has already been put to practical use. Aluminum die cast body frames are often plate-like with a thickness of about 2-3 mm and a length exceeding lm. In addition, in order to make the body frame rigid, a design in which ribs are arranged on the body frame is usually used. When such a thin, large-area plate-shaped product is subjected to solution quenching and quenching, a product having high strength can be obtained, but large heat treatment distortion occurs.

[0007] A body frame is formed by joining an aluminum die-cast product with another member. However, in order to join the body frame in this way, the dimensional accuracy of the product should be kept within ± 0.5 or less and ± 1.0 Omm or less. Heat treatment distortion varies widely from product to product, and no technology has been established to predict the shape after deformation due to heat treatment distortion. Therefore, in order to satisfy such dimensional accuracy, the aluminum die cast product after the heat treatment is straightened by using a die press or a normal.

[0008] Here, the mechanism of occurrence of heat treatment distortion will be described. In the heat treatment method of performing the solution treatment and the quenching treatment, most of the strain generated in the cooling process of quenching. The solution temperature of the A1-Si-Mg alloy for die casting typified by ADC3 alloy is set at about 500 ° C-540 ° C, which is higher than the melting temperature of the strengthened precipitate MgSi.

2

It is. Generally, the yield stress of a material decreases with increasing temperature of the material. The yield stress of aluminum alloys drops significantly above 400 ° C. Therefore, after the solution treatment at a temperature of 500 ° C or higher, the yield stress of the alloy is extremely low, and is permanently set with relatively small stress until the temperature decreases to about 400 ° C during the cooling process by quenching. It is in a state where distortion occurs.

[0009] The stress that causes permanent set in an aluminum die-cast product is generated by a temperature difference inside the aluminum die-cast product. In general, substances expand with increasing temperature . Therefore, if there is a portion having a different temperature in the material, a difference occurs in the amount of expansion, and this causes an internal stress. When the internal stress exceeds the yield stress, permanent distortion occurs in the material. Permanent strain occurs in the high temperature part where the yield stress is lower.

[0010] There are several causes for the temperature difference inside the aluminum die cast product during the quenching process. One major cause is, for example, that the thickness of the product varies from location to location. As described above, the product is provided with the ribs and the like, and the cooling is delayed as the ribs and the like are provided. As the cooling rate increases and the quenching process increases, the temperature difference increases, and heat treatment distortion, which is permanent distortion, occurs.

[0011] Another major cause is the boiling phenomenon of cooling water used for quenching. In general, hot water of about 60 ° C is used as cooling water for quenching aluminum-palladium die-cast products. When a high-temperature aluminum die-cast product is immersed in cooling water during the quenching process, heat of vaporization for boiling is supplied from the high-temperature die-cast product to the hot water. As a result, a portion of the hot water in contact with the product is heated and boiled. At this time, the partial heat of the die cast product that supplied the heat of vaporization is taken away.

[0012] Because boiling does not occur uniformly in the entire hot water in contact with the product surface, the degree of cooling differs depending on the location, which causes a temperature distribution in the product. There are two types of boiling, film boiling and nucleate boiling. Film boiling refers to boiling when a relatively hot substance comes into contact with water and the entire surface of the substance undergoes a transformation from water to water vapor. Nucleate boiling refers to boiling that occurs when a relatively low-temperature substance comes into contact with water, and nucleates at protruding parts such as dust adhering to the substance surface and corners provided on the substance surface. In quenching aluminum die cast products, nucleate boiling occurs selectively at the tips of protruding parts such as ribs provided on the product, so this part is cooled particularly strongly, causing a temperature difference inside the product and causing permanent distortion. Appreciable heat treatment distortion occurs.

[0013] As described above, heat treatment distortion occurs after heat treatment in order to satisfy the desired dimensional accuracy. Aluminum die-casting products are corrected using a die press or a hammer. Correction after heat treatment is a factor that increases the manufacturing cost of products, and correction may not be possible in some cases. Therefore, heat treatment methods that minimize the occurrence of heat treatment distortion have been devised. [0014] One of them is a method using a glycol-based organic synthetic polymer as a quenching agent. This quenching agent dissolves uniformly in water at room temperature, but becomes insoluble above the cloud point and separates hydraulically. When this aqueous solution is used as a cooling medium for quenching, when a high-temperature aluminum die-cast product enters the solution, the solution in contact with the product surface locally exceeds the cloud point. Thus, a film-like polymer compound is formed. This polymer in the form of a film protects the entire product from quenching water as a cooling medium for quenching and prevents excessive cooling by nucleate boiling. Thereafter, when the temperature of the solution in contact with the product surface falls below the cloud point over time, the high molecular compound is re-dissolved and the product is rapidly cooled. The cloud point is adjusted to about 80 ° C.

[0015] However, the use of such a quenching agent reduces distortion, but requires a cleaning step after the treatment, and also requires disposal of waste material.

[0016] As another method, as described in JP-T-2003-517100, quenching is performed by forced air cooling from both surfaces or one surface of an aluminum alloy sheet product using a gas or a gas-liquid mixture. There is a way. Since quenching by gas does not cause a boiling phenomenon, it is possible to suppress the occurrence of heat treatment distortion, which tends to cause a temperature distribution inside the product.

Patent Document 1: Japanese Patent Publication No. 2003-517100 (page 8 to page 22, FIG. 3)

Disclosure of the invention

Problems to be solved by the invention

[0017] However, in the method described in JP-T-2003-517100, the aluminum alloy sheet product is subjected to forced air cooling on both sides or one side, so that it is not possible to quench a large number of products in an overlapping manner. This limits the number of products that can be processed in a single quench and significantly impairs mass productivity. In order to improve mass productivity, it is necessary to adopt a continuous furnace type, in which case the equipment becomes large. This is a problem in terms of capital investment and installation area.

Accordingly, an object of the present invention is to provide a heat treatment method for an aluminum die-cast product that does not require a large-scale facility, is excellent in mass productivity, and can produce a die-cast product satisfying desired dimensional accuracy and strength. And

Means for solving the problem [0019] In order to achieve the above object, the present invention provides a solution treatment step in which an aluminum die-cast product is subjected to a solution treatment, and a method in which the aluminum die-cast product undergoes a boiling phenomenon by using a cooling means after the solution treatment step. A cooling step of cooling the temperature of the aluminum die-cast product to 450 ° C. or lower, and quenching the aluminum die-cast product after the cooling step with water within 120 seconds after the solution treatment step. An object of the present invention is to provide a method of heat treating an aluminum die-cast product having a quenching step and an artificial aging step of artificially aging the aluminum die-cast product after the quenching step.

Here, the cooling means used in the cooling step is a liquid bath containing a liquid mixture of lead-bismuth, and in the cooling step, cooling may be performed by immersing the aluminum die-cast product in the liquid bath. Like,.

[0021] Alternatively, the cooling means used in the cooling step is an intermediate furnace, and the intermediate furnace is a fluidized bed furnace using alumina powder as a medium. In the cooling step, the aluminum die-cast product is placed in the fluidized bed furnace. Is preferably maintained for a predetermined period of time for cooling.

The invention's effect

According to the heat treatment method for an aluminum die-cast product according to claim 1 of the present invention, the temperature of the aluminum die-cast product is reduced by using a cooling means after the solution treatment step so that the aluminum die-cast product does not cause a boiling phenomenon. Since a cooling step of cooling to 450 ° C or less is performed, heat treatment distortion can be suppressed to ± 0.5 or less and ± 1.0 Omm or less, and a die-cast product having high dimensional accuracy can be manufactured. Also, by quenching within 120 seconds after the solution treatment step, it is possible to obtain the mechanical properties required for the body frame and the like. Therefore, an aluminum die-cast product can be used for a vehicle body frame or the like that requires high dimensional accuracy and mechanical characteristics.

According to the method for heat-treating an aluminum die-cast product according to claim 2 of the present invention, the cooling means used in the cooling step is a liquid bath containing a liquid mixture of lead-bismuth, and in the cooling step, the aluminum bath is added to the liquid bath. Cooling is performed by immersing the product, so that a large number of die-cast products can be heat-treated at once, and the heat treatment method for aluminum die-cast products is as powerful as a continuous furnace. Mass production can be increased without the need for equipment. [0024] Further, since the temperature of the aluminum die-cast product can be lowered to 350 ° C or less within 120 seconds after the solution annealing process, the displacement amount of the aluminum die-cast product after heat treatment, that is, the amount of heat treatment distortion, is reduced. Can be set to a very low value of ± 0.5 mm or less, and very high dimensional accuracy can be obtained. Therefore, aluminum die-cast products can be mass-produced without performing a process for correcting heat treatment distortion.

[0025] According to the method for heat-treating an aluminum die-cast product according to claim 3 of the present invention, the cooling means used in the cooling step is an intermediate furnace, and the intermediate furnace is a fluidized bed furnace using alumina powder as a medium. In order to cool a large number of die-cast products at once, the aluminum die-cast products were cooled in a fluidized bed furnace by holding them for a predetermined time. Mass production can be improved without requiring large and powerful equipment such as a continuous furnace.

[0026] Further, since the temperature of the aluminum die-cast product can be lowered to 350 ° C or less within 120 seconds after the solution annealing process, the amount of displacement of the aluminum die-cast product after the heat treatment, that is, the amount of the distortion of the heat treatment. Can be set to a very low value of ± 0.5 mm or less, and very high dimensional accuracy can be obtained. Therefore, aluminum die-cast products can be mass-produced without performing a process for correcting heat treatment distortion.

Brief Description of Drawings

FIG. 1 is a graph showing the relationship between the temperature of an aluminum die-cast product during quenching and the amount of displacement of the aluminum die-cast product.

[Figure 2] A graph showing the relationship between the quenching delay time and the hardness after aging treatment of an aluminum die-cast product that also has A1-Si-Mg alloy strength.

FIG. 3 is a schematic diagram showing a method for heat-treating an aluminum die-cast product according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram showing the relationship between elapsed time and temperature in a method for heat-treating an aluminum die-cast product according to the first embodiment, which was performed to manufacture the material 1 of the present invention.

FIG. 5 is a schematic diagram showing a relationship between elapsed time and temperature in a heat treatment method for an aluminum die-cast product performed to manufacture comparative materials 1 and 2.

FIG. 6 shows a method for heat-treating an aluminum die-cast product according to the first embodiment of the present invention. FIG. 3 is a front view showing the shapes and dimensions of the present invention material 1, comparative material 1, and comparative material 2 used in a tensile test for testing the effect.

FIG. 7 is a schematic view showing a heat treatment method for an aluminum die-cast product according to a second embodiment of the present invention.

FIG. 8 is a schematic diagram showing the relationship between elapsed time and temperature in a method of heat-treating an aluminum die-cast product according to a second embodiment for manufacturing the material 2 of the present invention.

FIG. 9 is a schematic diagram showing the relationship between elapsed time and temperature in a method of heat-treating an aluminum die-cast product performed to manufacture comparative material 3.

FIG. 10 is a schematic view showing a heat treatment method for an aluminum die-cast product according to a third embodiment of the present invention.

FIG. 11 is a schematic diagram showing the relationship between elapsed time and temperature in a method for heat-treating an aluminum die-cast product according to a third embodiment, which was performed to manufacture the inventive material 4 and the inventive material 6.

FIG. 12 is a schematic diagram showing the relationship between elapsed time and temperature in a method of heat-treating an aluminum die-cast product performed to manufacture comparative material 4.

BEST MODE FOR CARRYING OUT THE INVENTION

[0028] A method for heat-treating an aluminum die-cast product according to the first embodiment of the present invention will be described with reference to FIGS. The heat treatment method for an aluminum die-cast product according to the first to third embodiments described below is a heat treatment method applied to an aluminum die-cast product manufactured by a die casting method using an aluminum alloy. Yes, they are performed in the order of solution treatment step, cooling step, quenching step, artificial aging step and force.

[0029] In the solution annealing process in the method for heat-treating an aluminum die-cast product according to the first embodiment, a large number of aluminum die-cast products are maintained at a temperature of 500 ° C-550 ° C for several hours. Heat to form a solution. In the cooling process, the temperature of the aluminum die-cast product is cooled to 450 ° C or less using a cooling device after the solution treatment process is completed. The cooling device used is an intermediate furnace provided with a stirrer capable of keeping the inside at an atmosphere at a predetermined intermediate temperature for a predetermined period of time and mounting a large number of die-cast products inside. The A large number of die-casting products are held in a force in the intermediate furnace for a predetermined period of time, so that the 500-540 ° C force, which is the temperature at which the solution is solidified, is cooled to 450 ° C or less. The cooling device corresponds to a cooling means.

[0030] In the quenching step, a number of aluminum die-cast products that have undergone the cooling step are quenched by immersing them in warm water at a predetermined temperature within 120 seconds after the solution treatment step is completed. In the artificial aging process, a number of aluminum die-cast products that have undergone the quenching process are subjected to artificial aging by holding them in an aging furnace for a predetermined time. The inside of the aging furnace is maintained at a predetermined temperature between 100 ° C and 200 ° C.

[0031] After the solution shading process step was completed, the temperature of the aluminum die-cast product was cooled to 450 ° C or lower using a force cooling device, and an intermediate furnace was used as a cooling device. Die-cast products can be cooled at the same time without boiling. For this reason, it is possible to produce a die-cast product having high strength and high dimensional accuracy with a heat treatment distortion of ± 1.0 Omm or less with excellent mass productivity. In addition, a large-scale facility such as a continuous furnace is not required for performing a heat treatment method for an aluminum die-cast product, which is advantageous in terms of capital investment and installation area.

[0032] Cooling the temperature of the aluminum die-cast product to 450 ° C or less within 120 seconds after the completion of the solution casting process can also be achieved by natural air cooling. However, after the solution treatment, if a large amount of die-cast products are allowed to cool outside the solution furnace by batch processing, the temperature difference between the product that first came out of the solution furnace and the product that came out of the solution furnace later. Therefore, the variation in mechanical properties after heat treatment increases. However, in the present embodiment, since the intermediate furnace is used, it is possible to prevent such variation from increasing.

[0033] Here, the grounds for cooling the aluminum die-cast product to 450 ° C or lower and quenching within 120 seconds after the solution treatment step is completed will be described. As described above, the solution temperature of the A1-Si-Mg-based alloy for die casting represented by the ADC3 alloy is 500 ° C to 540 ° C. If the aluminum die-cast product is quenched as it is at such a high temperature, the high-temperature aluminum alloy has a remarkably low yield stress, and is likely to cause permanent heat treatment distortion. On the other hand, if the temperature of the aluminum die-cast product at the time of quenching is low, the generated distortion is small. [0034] As shown in Fig. 1, the average value and the variation of the displacement amount due to the heat treatment distortion decrease as the quenching temperature, that is, the temperature of the aluminum die-cast product at the start of quenching decreases. In Figure 1, 300. C, 350. C, 400. C, 425 ° C, 450 ° C, 475 ° C, 500 ° C, 7 kinds of quenching temperature, displacement and variation when quenching a total of 35 samples of 5 samples of the same shape at each quenching temperature However, it can be seen that the displacement of all products at each quenching temperature is 1.Omm or less when the quenching temperature force is 50 ° C or less.

[0035] Further, it can be seen that the displacement of all products becomes 0.5 mm or less when the quenching temperature is 350 ° C or less. Therefore, when high dimensional accuracy is required as in the case of a vehicle body frame, it is necessary to reduce the quenching temperature to 50 ° C or less (preferably 350 ° C or less).

[0036] In order to quench at 450 ° C or lower after performing a solution treatment at 500 ° C to 540 ° C, some cooling step is required during the process. It is not preferable to use a method involving boiling as the cooling step because heat treatment distortion, which is permanent distortion, occurs.

[0037] Further, as shown in Fig. 2, if cooling takes too much time, the strengthened precipitate grows excessively, becomes coarse and deteriorates mechanical properties. In carrying out the present invention, the relationship between the quenching delay time and the hardness after aging treatment was investigated in order to confirm the limit of the quenching delay time of aluminum die-cast products made of A1-Si-Mg based alloys. The resulting force is as shown in FIG. 2, and the hardness that satisfies the mechanical properties used as the body frame is 75 to 80 for Rockwell F Scanneret.

[0038] Therefore, it can be seen from the graph shown in FIG. 2 that the quenching delay time must be within 120 seconds in order for the hardness to be 75 to 80. From the above, in order to manufacture an aluminum die cast product that can be used as a body frame, etc., after the product solution treatment process is completed, the temperature of the aluminum die cast product is cooled to 450 ° C or less, and the solution process is performed. It can be seen that it is necessary to quench the aluminum die-cast product within 120 seconds after.

Next, a test was conducted to test the effect of the heat treatment method for an aluminum die-cast product according to the first embodiment. In the test, 5 specimens were obtained for each of the two materials The displacement amount was measured and the tensile test was carried out using 16 pieces each, 6 pieces each for the comparative material 2. As the material 1 of the present invention, an aluminum die-cast product having a general thickness of 2.5 mm, a width of 350 mm, and a length of 500 mm was manufactured using an aluminum alloy having the composition shown in Table 1 below, according to the first embodiment. An aluminum die-cast product that had been subjected to a heat treatment method was used.

[table 1]

wt.%

[0040] The method of heat-treating the aluminum die-cast product performed to manufacture the material 1 of the present invention is described in more detail in FIG. 3 and FIG. After performing a solution treatment process at 3 ° C for 3 hours, the solution was transferred to an intermediate furnace maintained at an ambient temperature of 150 ° C, and kept therein for 90 seconds to perform a cooling process. After that, the product was taken out of the intermediate furnace and quenched in hot water at 60 ° C to perform the quenching process. The temperature of the product immediately before quenching in hot water ranged from 330 ° C to 400 ° C with varying forces. After the quenching process, an artificial aging process was performed in an aging furnace at 180 ° C for 3 hours.

As a comparative material 1, an aluminum alloy having the same composition as the material 1 of the present invention was used to produce an aluminum die-cast product having the same shape as the material 1 of the present invention, and the aluminum die-cast product according to the first embodiment was manufactured. A heat treatment method different from the heat treatment method was used. The difference between the heat treatment method and the heat treatment method for an aluminum die-cast product according to the first embodiment is that (1) a quenching step is performed without performing a cooling step after a solution treatment step; (2) After the quenching process, only the artificial aging process at 130 ° C for 3 hours was performed in the aging furnace, as shown in Fig. 5.

As a comparative material 2, an aluminum alloy having the same composition as the material 1 of the present invention was used to produce an aluminum die-cast product having the same shape as the material 1 of the present invention, and the aluminum-die-cast product of the first embodiment was manufactured. A heat treatment method different from the heat treatment method was used. Heat treatment method for aluminum die cast product according to the first embodiment in heat treatment method and The difference is that (1) the quenching step was performed without performing the cooling step after the solution treatment step, and (2) the artificial aging step at 130 ° C for 3 hours in an aging furnace after the quenching step. And (3) in the quenching process, the only difference was that a 30 ° C glycol aqueous solution, that is, an aqueous solution in which a heat treatment agent was dissolved, was used instead of the 60 ° C hot water, as shown in FIG. It is. In the measurement of the amount of displacement, the displacement in the direction perpendicular to the wall thickness of each of the present invention material 1, the comparative material 1 and the comparative material 2 was measured at six locations arbitrarily selected. The total number of products measured was three in total: 1 for the invention, 1 for the comparison, and 2 for the comparison. Table 2 shows the measurement results of the displacement under each condition.

[Table 2] Measurement location numbers

5 formula fee ¾

1 2 3 4 5 6

Invention material 1

1-0.29 -0.71 0.13 0.52 -0.26 -0.24

2 0.13 -0.51 0.02 0.35 0.25 0.33

3 -0.06 -0.42 0.42 0.75 0.98 0.46

4 0.06 -0.62 0.01 0.57 0.22 0.10

5 0.1 1 -0.27 0.39 0.49 0.74 0.42 Maximum absolute value 0.29 0.71 0.42 0.75 0.98 0.46 Comparative material 1

1 0.08-0.46 0.10 0.1 1 -0.86 -0.64

2 0.15 -0.72 -0.34 0.27 -0.26 0.05

3 0.43 0.1 1 1 .06 0.32 3.29 1.99

4 0.01 -0.71 0.20 0.79-0.25 -0.27

5 0.12 -0.48 0.02 0.21 -0.10 0.00 Maximum absolute value 0.43 0.72 1.06 0.79 3.29 1.99 Comparative material 2

1 -0.10 -0.20-0.40 -0.60 -0.70 -0.30

2 0.06 0.27 0.66 0.22 0.99 0.56

3 0.00 -0.30 0.88 1.93 0.27 one 0.10

4 -0.10 0.02 0.03 0.01 0.06 0.03

5 -0.00 -0.10 0.00 -0.20 0.00 0.03

6 0.25 -0.20 0.39 0.12 0.72 0.51 Maximum absolute value 0.25 0.30 0.88 1.93 0.99 0.56 [0044] As shown in Table 2, the comparative material 1 and the comparative material 2 have a maximum displacement of 2-3 mm. On the other hand, in the material 1 of the present invention, the displacement was suppressed to 1. Omm or less, which indicates that high dimensional accuracy was obtained.

[0045] The tensile test was performed using an Instron type testing machine by cutting a test piece from the above three types of heat-treated materials into a shape shown in Fig. 6 with a thickness of 2.5 ± 0.1mm. This was performed using The unit of the dimension shown in Fig. 6 is "mm (millimeter)". The strain rate was measured at room temperature at 5 mmZ min. The test results are as shown in Table 3, and the numerical values of the test results are the values obtained by measuring three types of the present invention material 1, comparative material 1, and comparative material 2, each of which is a total of 15 measurements. , The average value for each type.

[Table 3]

As shown in Table 3, the material 1 of the present invention has mechanical properties required for a vehicle body frame and the like in any of tensile strength, 0.2% strength, and elongation at break. RU

Next, a heat treatment method for an aluminum die-cast product according to a second embodiment of the present invention will be described with reference to FIGS. 7 to 9. The heat treatment method for an aluminum die-cast product according to the second embodiment uses a liquid bath containing a lead-bismuth (Pb-Bi) synthetic liquid without using an intermediate furnace as a cooling device used in the cooling step. The only difference from the heat treatment method for an aluminum die-cast product according to the first embodiment is that cooling is performed by immersing the aluminum die-cast product in the liquid bath. Except for this, it is the same as the heat treatment method for an aluminum die-cast product according to the first embodiment.

[0048] Since a liquid bath containing a lead-bismuth mixed liquid was used as a cooling device, a large number of die-cast products were simultaneously stabilized within 500 seconds within 500 seconds in a liquid bath without causing a boiling phenomenon. It can be cooled below 350 ° C. For this reason, aluminum die-cast products cooled to 350 ° C or less should be quenched within 120 seconds after the solution treatment step. Therefore, it is possible to produce a die-cast product having a high strength and a high dimensional accuracy with a heat treatment distortion of ± 0.5 mm or less with excellent mass productivity. In addition, it is possible to prevent variations in mechanical properties after the heat treatment from increasing. In addition, large-scale equipment such as a continuous furnace is not required to perform the heat treatment method for aluminum-die casting products, which is advantageous in terms of capital investment and installation area.

Next, a test was conducted to test the effect of the heat treatment method for an aluminum die-cast product according to the second embodiment. In the test, the displacement amount was measured and the tensile test was performed using two materials of the present invention material 2 and the comparative material 3 and a total of ten pieces each having five pieces. As the material 2 of the present invention, an aluminum alloy having the same composition as that of the material 1 of the present invention was used to produce an aluminum die-cast product having a general thickness of 2.5 mm, a width of 160 mm, and a length of 240 mm. A die-cast product that had been subjected to a heat treatment method was used.

[0050] The method of heat-treating the aluminum die-cast product performed to manufacture the material 2 of the present invention is described in more detail in FIG. 7 and FIG. After performing a solution treatment process at 500 ° C for 3 hours, a cooling device was constructed and immersed in a synthetic liquid bath with a Pb power of 4.5% by mass and a Bi of 55.5% by mass maintained at 255 ° C. Then, the cooling process was performed by holding the sample for 30 seconds. After that, the product was removed from the intermediate furnace and quenched in hot water at 60 ° C to perform the quenching process. The temperature of the product immediately before quenching in warm water was 350 ° C. After the quenching process, an artificial aging process was performed in an aging furnace at 140 ° C for 3 hours.

As a comparative material 3, an aluminum alloy having the same composition as the material 2 of the present invention was used to produce an aluminum die-cast product having the same shape as the material 2 of the present invention, and the aluminum die-cast product according to the second embodiment was manufactured. A heat treatment method different from the heat treatment method was used. The only difference between the heat treatment method and the heat treatment method for aluminum die-cast products according to the second embodiment is that the quenching step was performed without performing the cooling step after the solution treatment step. As shown.

[0052] For the measurement of the amount of displacement, the displacement in the direction perpendicular to the wall thickness was arbitrarily measured at three locations of the material 2 of the present invention and the material 3 of the comparative example. The number of products measured was two for the material of the present invention 2 and the comparative material 3, a total of ten for each of five. Measurement results of displacement under each condition Are shown in Table 4.

[Table 4]

[0053] As shown in Table 4, in the present invention material 2, the displacement amount was suppressed to about one third of the displacement amount of the comparative material 3, and extremely high dimensional accuracy was obtained. You can see that.

In the tensile test, the test pieces cut out from the above two types of heat-treated materials in the same shape as the test pieces used in the tensile test in the first embodiment were used. The test was performed using an Instron type testing machine in the same manner as in the tensile test. The strain rate was measured at room temperature at 5 mmZmin. The test results are as shown in Table 5, and the numerical values of the test results are the average of the values obtained by measuring two samples of the present invention material 2 and comparative material 3, five of each, and a total of ten measurements. Value.

[Table 5]

[0055] As shown in Table 5, the material 2 of the present invention exhibited any of tensile strength, 0.2% power resistance, and elongation at break. In addition, it has the mechanical properties required for the body frame and the like.

Next, a heat treatment method for an aluminum die-cast product according to the third embodiment of the present invention will be described with reference to FIGS. 10 to 12. The heat treatment method for an aluminum die-cast product according to the third embodiment uses a fluidized-bed furnace using alumina powder as a medium as an intermediate furnace of a cooling device used in a cooling process, and in the cooling process, the aluminum die-cast product is placed in the fluidized-bed furnace. Only the point that cooling is performed by holding the aluminum die for a predetermined time is different from the heat treatment method for an aluminum die-cast product according to the first embodiment. Except for this, the method is the same as the heat treatment method for the aluminum die-cast product according to the first embodiment.

[0057] Here, a fluidized bed furnace is a method in which a metal container (retort) is filled with a fluidized heating medium such as alumina powder, and a dispersion plate force gas placed below the retort is blown into the metal container to heat the metal container. This is a heat treatment furnace that heats non-heat treated material with a fluidized bed in which the fluid expands and fluidizes, and the force acts like a liquid.

[0058] Since a fluidized bed furnace using alumina powder as a medium was used as an intermediate furnace constituting the cooling device, a large number of die cast products were simultaneously and stably kept in a liquid bath for 120 seconds without causing a boiling phenomenon. It can be cooled from 500 ° C to below 350 ° C. For this reason, it becomes possible to quench the aluminum die-cast product cooled to 350 ° C or less within 120 seconds after the solution treatment process, has high strength, and has a heat treatment strain of ± 0.5 mm or less. Die casting products with high dimensional accuracy can be produced with excellent mass productivity.

[0059] Further, it is possible to prevent the variation in mechanical properties after the heat treatment from increasing.

In addition, a large-scale facility such as a continuous furnace is not required for performing a heat treatment method of an aluminum die-cast product, which is advantageous in terms of capital investment and installation area. Furthermore, since it is not necessary to use Pb-Bi or the like, a heat treatment method for an aluminum die-cast product can be performed at low cost.

Next, a test was conducted to test the effect of the heat treatment method for an aluminum die-cast product according to the third embodiment. In the test, the displacement amount was measured and the tensile test was performed using 25 specimens of 5 specimens each of 5 specimens of the present invention 3, 4 present invention, 5 present invention, 6 present invention, and 4 comparative materials. Was. The displacement was measured using the inventive material 3 and the comparative material 4, and the tensile test was performed using the inventive material 4, the inventive material 5, the inventive material 6, and the comparative material 4. As the material 3 of the present invention, five disk-shaped products each having a thickness of 2 mm and a diameter of 150 mm made of a rolled plate of 6061 alloy were prepared, and were arranged in parallel at 10 mm intervals. Of the heat treatment method of an aluminum die-cast product according to the third embodiment, ie, a solution treatment step, a cooling step and a quenching step of the heat treatment method of an aluminum die-cast product according to the third embodiment. A heat treatment method for performing the above was used.

[0062] The reason why the artificial aging process is not performed on the material 3 of the present invention is that the material 3 of the present invention is used only for a test for measuring the amount of displacement, and is not used for a test for examining mechanical properties such as a tensile test. On the other hand, the presence or absence of the artificial aging process has almost no effect on the displacement of aluminum die-cast products. In addition, although the inventive material 3 is not an aluminum die-cast product, in the displacement measurement test, the displacement is almost the same regardless of whether a rolled plate of 6061 alloy or an aluminum die-cast product is used. Therefore, inexpensive rolled 6061 alloy plates were used instead of aluminum die-cast products.

The material 4 of the present invention and the material 6 of the present invention are made of an aluminum alloy having the same composition as the material 1 of the present invention, and are formed of a substantially rectangular flat aluminum die-cast having a thickness of 3 mm, a width of 100 mm and a length of 300 mm. Cut the manufactured product by 10 mm in the length direction, cut out 15 pieces each for 5 of the present invention, 5 for the present invention, and 5 for the 6 present invention. The heat treatment method for the aluminum die-cast product according to the third embodiment was used.

[0064] The heat treatment method of the aluminum die-cast product performed to manufacture the inventive material 3—the present invention 6 is described in more detail with reference to FIGS. After performing a solution treatment process at 500 ° C for 3 hours in a gasification furnace, transfer to a fluidized bed furnace as an intermediate furnace, which is a cooling device maintained at an ambient temperature of 250 ° C, and hold it for 7 seconds in it. To perform a cooling step. The retort size of the fluidized bed furnace is 250 mm in diameter and 300 mm in depth. The retort was filled with 150 kg of alumina powder. The particle size of the aluminum powder is # 150. The gas blown from the dispersing plate flowed at 86 L (liter) Zmin as the atmosphere.

[0065] Thereafter, the product was also taken out of the fluidized bed furnace and quenched by quenching in hot water at 60 ° C. The process was performed. The temperature of the product immediately before quenching in warm water was 350 ° C. After the quenching process, an artificial aging process was performed in an aging furnace at 140 ° C for 3 hours. The above is the heat treatment method performed when manufacturing the material 4 of the present invention. The inventive material 5 and the inventive material 6 differ from the inventive material 4 only in that the aging furnace temperature in the artificial aging process is 160 ° C and 180 ° C, respectively. Identical. Further, as described above, the heat treatment method performed to manufacture the material 3 of the present invention does not include an artificial aging step! Only the point ヽ differs from the heat treatment method performed to produce the material 4 of the present invention.

[0066] As the comparative material 4, an aluminum alloy having the same composition as the material 4 of the present invention 4 and the material 6 of the present invention was used. A heat treatment method different from the heat treatment method for the aluminum die-cast product according to the third embodiment was used. The difference between the heat treatment method and the heat treatment method for an aluminum die-cast product according to the third embodiment is that (1) a quenching step is performed without a cooling step after a solution treatment step, and (2) ) After the quenching process, only the artificial aging process at 130 ° C for 3 hours was performed in the aging furnace, as shown in Fig. 12.

[0067] In the measurement of the displacement, the displacement at the one-point of the outer peripheral portion and the displacement at the center of the material 3 of the present invention and the comparative material 4 were measured in the direction perpendicular to the plane of the plate. . The number of products measured was two for the material 3 of the present invention and the material 4 for the comparison, five for each, and a total of ten products. Table 6 shows the difference between the amount of displacement at the outer periphery and the amount of displacement at the center under each condition.

[Table 6]

Single Til: mm

[0068] As shown in Table 6, the average value of the displacement amount of the comparative material 4 was 5.52 mm. On the other hand, in the case of the material 3 of the present invention, the average value of the displacement amount was as small as 0.20 mm, and it was found that an extremely high dimensional accuracy was obtained. The tensile test was performed using the same four types of heat-treated materials of the present invention material 4, the present invention material 5, the present invention material 6, and the comparative material 4 as the test pieces used in the tensile test in the first embodiment. Using a test piece cut out in a shape, the test was performed using an Instron type testing machine in the same manner as in the tensile test in the first embodiment. The strain rate was measured at 5 mmZmin at room temperature. The test results are as shown in Table 7, and the numerical values of the test results were measured for four types of the present invention material 4, the present invention material 5, the present invention material 6, and the comparative material 4, a total of 20 for each of 5 types. This is the average of the values for each type.

[Table 7]

[0070] As shown in Table 7, the materials of the present invention 4 and the present invention 6 have different tensile strengths, 0.2% resistance to fracture, and elongation at break, which are required for the vehicle body frame and the like. With the characteristic nature.

[0071] The method of heat-treating an aluminum die-cast product according to the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made within the scope described in the claims. For example, in the heat treatment method for an aluminum die-cast product according to the present embodiment, an intermediate furnace, a fluidized-bed furnace, or a liquid bath containing a lead-bismuth alloy liquid is used as a cooling device. For example, a cooling device that performs cooling using steam as a medium may be used.

Industrial applicability

[0072] The heat treatment method for an aluminum die-cast product of the present invention is extremely useful particularly in the field of heat treatment for performing T6 treatment on an aluminum die-cast product.

Claims

The scope of the claims

[1] a solution treatment step of solution treating an aluminum die-cast product;

A cooling step of cooling the temperature of the aluminum die-cast product to 450 ° C. or less by using cooling means after the solution immersion treatment step so that the aluminum die-cast product does not cause a boiling phenomenon;

A quenching step of quenching the aluminum die-cast product having passed through the cooling step with water within 120 seconds after the solution treatment step;

An artificial aging step of artificially aging the aluminum die-cast product after the quenching step.

[2] The cooling means used in the cooling step is a liquid bath containing a lead-bismuth combined liquid, and in the cooling step, cooling is performed by immersing the aluminum die-cast product in the liquid bath. The method for heat-treating an aluminum die-cast product according to claim 1.

[3] The cooling means used in the cooling step is an intermediate furnace. The intermediate furnace is a fluidized bed furnace using alumina powder as a medium. In the cooling step, the aluminum die-casting product is placed in the fluidized bed furnace. 2. The aluminum according to claim 1, wherein the cooling is performed by holding for a predetermined time.

-Heat treatment method for PMM die cast products.