JP2021070833A - Manufacturing material of aluminum alloy forged material - Google Patents

Abstract

To provide an aluminum alloy forged material in which a mechanical characteristic difference between a periphery of a surface and a center part is small, in an undercarriage member for an automobile.SOLUTION: In a heat treatment process during manufacture of an aluminum alloy material, namely, during a quenching process in it, average wind speed of the atmosphere around the aluminum alloy material immediately after forging until water quenching is 1.0 m/sec or less.SELECTED DRAWING: Figure 3

Description

The present invention relates to, for example, an aluminum 6000 series alloy forged material suitable as a suspension member for supporting a vehicle body of a transport aircraft represented by a four-wheeled vehicle.

In recent years, due to the demands of environmental regulations in the automobile industry, various members used in automobiles, for example, suspension members for supporting the vehicle body, particularly high as undercarriage members for automobiles used for suspension arms, upper arms, lower arms, tie rod ends, etc. An aluminum 6000 series alloy (Al-Mg-Si series) having excellent strength, high toughness and corrosion resistance is used.

However, in recent years, there has been a demand for further weight reduction of automobiles, and in order to satisfy this demand, it has become necessary to further improve the strength from JIS standard 6000 series alloys. In other words, it is necessary to reduce the wall thickness of the member by increasing the strength. In addition, as a suspension member, further quality improvement is required not only in strength but also in corrosion resistance such as stress corrosion cracking.

In order to meet such demands, it has been proposed to obtain a required metal structure by controlling the composition and manufacturing process of a high-strength aluminum 6000 series alloy for automobile undercarriage members to solve the problem. Specifically, in the quenching process of the manufacturing process, it has been proposed to obtain a required metal structure and solve the problem by controlling the attitude of the aluminum alloy forged material when quenching in water (Patent Document 1 below). ).

JP-A-2017-179413

However, in the quenching process of the actual manufacturing process, there is a possibility that the required characteristics cannot be obtained due to external factors such as the temperature of the outside air and the time from the end of the temperature rise to the quenching in addition to the posture.

Specifically, when the outside temperature is low or the time until quenching is long, the heat of the aluminum alloy forged material is dissipated to the outside air by the time of quenching, and the temperature falls below the required temperature at the time of quenching. , It is impaired to obtain a sufficient supersaturated solid solution, and the mechanical properties may be inferior.

Further, in this case, when the heat is radiated preferentially in the vicinity of the outer peripheral portion of the aluminum alloy forged material as compared with the central portion and the aluminum alloy forged material is quenched in a state where a temperature difference occurs in the vicinity of the outer peripheral portion and the central portion, quenching There is a problem that the shrinkage is not uniform at the time of cooling, causing a shape defect.

Further, in this subject, during hot forging, the aluminum alloy forging material and the die used as a molding member during hot forging are heated to a high temperature, so that an updraft is generated by the heat source. It is also affected by the flow of air due to the updraft. That is, when the wind speed is high, heat is taken from the vicinity of the outer peripheral portion of the aluminum alloy forged material before quenching, and a temperature difference is generated between the outer peripheral portion and the central portion of the aluminum alloy forged material described above. There is a problem that these temperature differences cause shape defects as described above.

The present invention has been made in view of such a technical background, and in the quenching step in the manufacturing process of the aluminum alloy forged material, the wind speed is controlled so as to be formed at the outer peripheral portion and the central portion of the aluminum alloy forged material. It is an object of the present invention to provide a method for producing an aluminum alloy forged material, which has sufficient mechanical properties and can suppress shape defects in the shrinkage process during quenching.

In order to achieve the above object, the present invention provides the following means.

[1] A method for producing an aluminum alloy forged material, which includes a solution heat treatment step and a water quenching heat treatment step.
A method for producing an aluminum alloy forged material, characterized in that the average wind velocity of the atmosphere around the aluminum alloy forged material between the solution heat treatment step and the water quenching heat treatment step is 1.0 m / sec or less.

[2] The method for producing an aluminum alloy forged material according to item 1 above, wherein the aluminum alloy is an Al—Mg—Si based alloy.

[3] The method for producing an aluminum alloy forged material according to item 1 or 2 above, wherein the solution heat treatment step is combined with raising the temperature in the forging step.

[4] The method for producing an aluminum alloy forged material according to any one of items 1 to 3 above, wherein the temperature of water in the water quenching heat treatment step is 40 ° C to 90 ° C.

[5] The method for producing an aluminum alloy forged material according to any one of items 1 to 4 above, wherein the aluminum alloy forged material is an automobile suspension member.

In the invention of [1], by controlling the average wind speed of the atmosphere to 1.0 m / sec or less, it is possible to eliminate the temperature difference between the outer peripheral portion and the central portion of the aluminum alloy forged material as much as possible, and it is sufficiently mechanical. It has characteristics and can suppress shape defects during the shrinkage process during quenching. Further, it is possible to provide an aluminum alloy forged material having less shape deformation due to the heat treatment step.

In the invention of [2], it is possible to provide an Al—Mg—Si based alloy having less shape deformation due to the heat treatment step.

In the invention of [3], it is possible to inexpensively provide an aluminum alloy material having less shape deformation due to the heat treatment step.

In the invention of [4], the shape deformation caused by the heat treatment step of the aluminum alloy member can be further reduced.

In the invention of [5], it is possible to provide an aluminum alloy undercarriage member with less shape deformation due to a heat treatment step.

It is a process flow diagram which shows an example of the process in the manufacturing method of the aluminum alloy forged material of this invention. It is a perspective view which shows an example of the cut casting material formed in the manufacturing process in the manufacturing method of the aluminum alloy forging material of this invention. It is a perspective view which shows an example of the forged product made of the aluminum alloy material which concerns on this invention.

Hereinafter, embodiments of the aluminum alloy material according to the present invention and the method for producing the aluminum alloy forged material according to the present invention will be described in detail. The embodiments shown below are merely examples, and the present invention is not limited to these illustrated embodiments, and can be appropriately modified without departing from the technical idea of the present invention.

The aluminum 6000 series alloy forged material according to the present invention is an Al—Mg—Si based alloy forged material, and during the quenching treatment in the manufacturing process, the time from the start of exposure to the atmosphere to the quenching, the temperature of the atmosphere and the atmosphere. It is characterized in that the wind speed inside is controlled within a certain condition.

With such a configuration, the aluminum alloy forged material is hardened with the temperature difference between the outer peripheral portion and the central portion as small as possible, and a sufficient supersaturated solid solution can be obtained, and at the same time, a shape generated due to the temperature difference. It is possible to suppress defects. The present invention can solve the above-mentioned problems by the above design and provide an aluminum 6000 series alloy forged material suitable as a member for an automobile suspension.

The method for producing an aluminum alloy forged material of the present invention includes a solution heat treatment step and a water quenching heat treatment step, and the average wind velocity of the atmosphere around the aluminum alloy forged material between the solution heat treatment step and the water quenching heat treatment step. Is 1.0 m / sec or less.

As a means for controlling the average wind velocity of the atmosphere around the aluminum alloy forged material to 1.0 m / sec or less, for example, in the transport section of the aluminum alloy forged material when moving to the water quenching heat treatment step after the solution heat treatment step. It is possible to provide an enclosure. By providing the enclosure in this way, the wind speed of the atmosphere in the transport section can be controlled.

Further, the means for controlling the wind speed of the atmosphere is not limited to providing an enclosure, and it is sufficient that the average wind speed of the atmosphere can be controlled to 1.0 m / sec or less in the transport section.

Further, in the present invention, the average wind speed of the atmosphere is controlled to be 1.0 m / sec or less, but it is preferable that the average wind speed is 0 m / sec, that is, there is no wind. By doing so, it is possible to manufacture an aluminum alloy forged product of the same quality with higher accuracy.

As described above, the average wind velocity of the atmosphere around the aluminum alloy forged material between the solution heat treatment step and the water quenching heat treatment step is 1.0 m / sec or less, so that the outer peripheral portion of the aluminum alloy forged material and the outer peripheral portion of the aluminum alloy forged material and It is possible to eliminate the temperature difference in the central portion as much as possible, have sufficient mechanical properties, and suppress shape defects in the shrinkage process during quenching. Further, it is possible to provide an aluminum alloy forged material having less shape deformation due to the heat treatment step.

Next, an example of a method for producing an aluminum 6000 series alloy forged material according to the present invention will be described in detail. The present manufacturing method includes a molten metal forming step of obtaining a molten metal of an Al—Mg—Si based alloy, and a casting step of obtaining a casting material by casting the obtained molten metal.

In the molten metal forming step, an aluminum alloy molten metal prepared by dissolving Si and Mg in an amount of 0.05% by mass to 1.3% by mass and having a composition of Al and unavoidable impurities is obtained. If necessary, metals such as Fe, Cu, Cr, Mn, Ni, Ti, and Zr may be added to the molten alloy.

Next, a casting material (forging billet) is obtained by casting the obtained molten metal (casting step). The casting method is not particularly limited, and a conventionally known method may be used. Examples thereof include a continuous casting and rolling method and a semi-continuous casting method (DC casting method).

As described below, if necessary, further select one or more of the steps such as homogenization heat treatment step, hot forging step, solution treatment step, quenching treatment step, artificial aging curing treatment step, and the like. It may be carried out (see FIG. 1).

(Homogenization heat treatment process)
By subjecting the obtained cast material to homogenization heat treatment, microsegregation generated by solidification is homogenized, supersaturated solid solution elements are precipitated, and the metastable phase is changed to an equilibrium phase. The size of the intermetallic compound can be reduced by the homogenization heat treatment. By reducing the size of the intermetallic compound in this way, fracture starting from the intermetallic compound is suppressed, and the tensile strength is further improved. Further, by performing the homogenizing heat treatment, each element contained in the intermetallic compound is uniformly diffused into the base metal, and it is possible to further improve the tensile strength by solid solution strengthening and precipitation. ..

The homogenization heat treatment is preferably performed within a temperature range that does not cause eutectic melting and at a high temperature as much as possible. By performing the homogenizing heat treatment under such conditions, the intermetallic compound is effectively dissolved and diffused in the base metal. As a result, the size of the intermetallic compound can be reduced.

Next, the cast material after the homogenization heat treatment is cut to a predetermined length to obtain a forging billet.

(Hot forging process)
The temperature conditions of hot forging are related in that the characteristics of the aluminum alloy are expressed more reproducibly, that is, the microstructure after the solution treatment of the aluminum alloy can be made into equiaxed crystal grains. .. Above all, the hot forging is preferably performed by setting the mold temperature to 100 ° C. to 300 ° C. and the material temperature to 400 ° C. to 550 ° C. By performing hot forging under such conditions, the tensile strength of the aluminum alloy material can be further improved.

(Solution treatment process, quenching treatment process, artificial age hardening process)
Next, the solution heat treatment step, the quenching treatment step, and the artificial aging hardening treatment step will be described. The solution treatment is a heat treatment in which an aluminum alloy is held at a high temperature and then rapidly cooled to form a supersaturated solid solution. The quenching treatment is a heat treatment in which the solid solution state obtained by the solution treatment is rapidly cooled to form a supersaturated solid solution. The artificial age hardening treatment is a heat treatment for heating and holding an aluminum alloy at a relatively low temperature to precipitate elements that are supersaturated and solid-solved to impart appropriate hardness. By performing these heat treatments (solution heat treatment, quenching treatment, artificial age hardening treatment), fine precipitates are uniformly dispersed, and an aluminum alloy material having a highly balanced strength, ductility and toughness can be obtained.

Further, the solution treatment step can be omitted as follows by using the temperature rise in the forging step together. That is, in the forging process, the aluminum alloy held at a high temperature immediately after forging is rapidly cooled as it is to form a supersaturated solid solution. In these steps (hot forging, forging quenching), aluminum alloys of the same quality can be obtained as compared with the conventional steps of slow cooling once after forging and then heating again in a continuous heating furnace or a single furnace to perform solution treatment. Not only that, it not only saves the energy required for reheating, but also makes it possible to significantly improve the manufacturing time.

As described above, by combining the solution heat treatment step with the temperature rise in the forging step, it is possible to inexpensively provide an aluminum alloy material having less shape deformation due to the heat treatment step.

These heat treatment conditions may be selected according to the component composition, required properties, and the like. The solution treatment is not particularly limited, but is preferably performed by setting the heating temperature to 510 ° C. to 560 ° C. and the holding time to 0.5 hour to 6 hours. In this case, the cost and characteristics. The balance becomes better. In the forging and quenching step, it is preferable to set the temperature immediately after forging to 510 ° C. to 560 ° C. and the holding time, that is, the time from immediately after forging to quenching to 1 second to 30 seconds at the same temperature.

When the design concept according to the present invention is used in the quenching process, the result is as follows. That is, in the quenching step or the forging quenching step, the time from the completion of the temperature rise of the aluminum alloy forged material to the quenching and the outside air temperature are controlled within a certain range, and the outside air wind speed is controlled to a certain value or less. With such a configuration, in the aluminum forged material at the time of quenching, the temperature difference between the outer peripheral portion and the central portion of the aluminum forged material is kept as small as possible, and the temperature is maintained so that a sufficient supersaturated solid solution can be obtained. It can be hardened as it is.

The quenching treatment is not particularly limited, but it is preferable to quench with water at 10 ° C. to 90 ° C. (water quenching treatment).

In particular, the temperature of water is preferably 40 ° C to 90 ° C. This is because the shape deformation caused by the heat treatment step of the aluminum alloy member can be further reduced.

The artificial age hardening treatment is not particularly limited, but is preferably performed by setting the heating temperature to 160 ° C. to 250 ° C. and the holding time to 10 minutes to 8 hours. The balance of characteristics becomes better.

Aluminum alloy products (cast products, forged products, etc.) manufactured in this way have excellent tensile properties at room temperature, and in addition, have higher strength on surfaces that are susceptible to external factors. Therefore, for example, it is suitably used as a material for undercarriage parts for automobiles (suspension arm, upper arm, lower arm, tie rod end, etc.).

Next, specific examples of the present invention will be described, but the present invention is not particularly limited to those of these examples.

<Example 1>
Si: 1.10% by mass, Fe: 0.25% by mass, Cu: 0.40% by mass, Mn: 0.50% by mass, Mg: 0.85% by mass, Cr: 0.15% by mass. After heating an aluminum alloy whose balance is Al and unavoidable impurities to obtain a molten aluminum alloy, a continuous cast material was obtained using the molten aluminum alloy. The obtained continuous cast material was homogenized and heat-treated, and then air-cooled.

Next, after cutting the continuous cast material after air cooling, hot forging was performed on the cut cast material 10 (see FIG. 2). The obtained forged material 20 (see FIG. 3) was heated at a solution temperature of 540 ° C., placed in water at 50 ° C. for water quenching, and then heated at 180 ° C. for 6 hours for artificial age hardening. Forged product 20 was obtained.

When this water quenching was performed, the quenching was performed in a state where the average wind speed of the outside air was 0.8 m / sec.

<Example 2>
Si: 1.10% by mass, Fe: 0.25% by mass, Cu: 0.40% by mass, Mn: 0.50% by mass, Mg: 0.85% by mass, Cr: 0.15% by mass. After heating an aluminum alloy whose balance is Al and unavoidable impurities to obtain a molten aluminum alloy, a continuous cast material was obtained using the molten aluminum alloy. The obtained continuous cast material was homogenized and heat-treated, and then air-cooled.

Next, after cutting the continuous cast material after air cooling, the cut cast material 10 (see FIG. 2) was hot forged at a material temperature of 530 ° C. and a mold temperature of 180 ° C. After the obtained forging material 20 (see FIG. 3) was forged, it was placed in water at 50 ° C. and water-quenched while the heating during hot forging was maintained. Then, it was heated at 180 ° C. for 6 hours and subjected to artificial age hardening treatment to obtain a forged product 20.

When this water quenching was performed, the quenching was performed in a state where the average wind speed of the outside air was 0.8 m / sec.

<Comparative example 1>
Si: 1.10% by mass, Fe: 0.25% by mass, Cu: 0.40% by mass, Mn: 0.50% by mass, Mg: 0.85% by mass, Cr: 0.15% by mass. After heating an aluminum alloy whose balance is Al and unavoidable impurities to obtain a molten aluminum alloy, a continuous cast material was obtained using the molten aluminum alloy. The obtained continuous cast material was homogenized and heat-treated, and then air-cooled.

Next, after cutting the continuous cast material after air cooling, hot forging was performed on the cut cast material 10 (see FIG. 2). The obtained forged material 20 (see FIG. 3) was heated at a solution temperature of 540 ° C., placed in water at 50 ° C. for water quenching, and then heated at 180 ° C. for 6 hours for artificial age hardening. Forged product 20 was obtained.

When this water quenching was performed, the quenching was performed in a state where the average wind speed of the outside air was 1.1 m / sec.

<Comparative example 2>
Si: 1.10% by mass, Fe: 0.25% by mass, Cu: 0.40% by mass, Mn: 0.50% by mass, Mg: 0.85% by mass, Cr: 0.15% by mass. After heating an aluminum alloy whose balance is Al and unavoidable impurities to obtain a molten aluminum alloy, a continuous cast material was obtained using the molten aluminum alloy. The obtained continuous cast material was homogenized and heat-treated, and then air-cooled.

Next, after cutting the continuous cast material after air cooling, the cut cast material 10 (see FIG. 2) was hot forged at a material temperature of 530 ° C. and a mold temperature of 180 ° C. After the obtained forging material 20 (see FIG. 3) was forged, it was placed in water at 50 ° C. and water-quenched while the heating during hot forging was maintained. Then, it was heated at 180 ° C. for 6 hours and subjected to artificial age hardening treatment to obtain a forged product 20.

When this water quenching was performed, the quenching was performed in a state where the average wind speed of the outside air was 1.1 m / sec.

Various evaluations were performed on each forged product obtained as described above based on the following evaluation method.

<Hardness measurement>
In the obtained forged product, the hardness near the surface layer and the hardness at the center were measured, respectively. Specifically, an arbitrary arm portion was cut out, and a sample for hardness measurement of 10 mm square was cut out from the vicinity of the surface layer and the central portion of the arm portion. The surface on which the hardness is measured is the surface in the vicinity of the surface layer which is about 1 mm from the surface layer, and the central portion is the surface where the hardness is measured at a position halved from the surface layer to the opposite surface layer. .. A sample cut into a 10 mm square was embedded in resin, the target surface was polished to # 2000 with emery paper, and then the Vickers hardness was measured using a Vickers hardness tester. The load at the time of measuring the Vickers hardness was 10 g, and 10 points were measured for one sample to calculate the average Vickers hardness. The measurement results of Vickers hardness are shown in Table 1. In the evaluation method, when the hardness was 120 or more and the hardness difference between the vicinity of the surface layer and the central portion was 5 or less, the evaluation method was “◯”, and the case where either one was not satisfied or both were not satisfied was evaluated as “x”.

From Table 1, it can be seen that in Examples 1 and 2, the hardness difference between the vicinity of the surface layer and the central portion is small and the hardness is high.

Further, it can be seen that in Comparative Examples 1 and 2, the difference in hardness between the vicinity of the surface layer and the central portion is larger and the hardness is lower than that of Examples 1 and 2.

Since the aluminum alloy material according to the present invention and the forged product for undercarriage obtained by the manufacturing method of the present invention have a small difference in strength inside the forged product, for example, a suspension arm, an upper arm, and a lower arm for an automobile undercarriage. , But it is preferably used as a material for tie rod ends and the like, but is not particularly limited to such applications.

10 ... Casting product (casting material)
20 ... Forged product (forged material)

Claims (5)

A method for producing an aluminum alloy forged material, which includes a solution heat treatment step and a water quenching heat treatment step.
A method for producing an aluminum alloy forged material, characterized in that the average wind velocity of the atmosphere around the aluminum alloy forged material between the solution heat treatment step and the water quenching heat treatment step is 1.0 m / sec or less. The method for producing an aluminum alloy forged material according to claim 1, wherein the aluminum alloy is an Al—Mg—Si based alloy. The method for producing an aluminum alloy forged material according to claim 1 or 2, wherein the solution heat treatment step is combined with raising the temperature in the forging step. The method for producing an aluminum alloy forged material according to any one of claims 1 to 3, wherein the temperature of water in the water quenching heat treatment step is 40 ° C to 90 ° C. The method for producing an aluminum alloy forged material according to any one of claims 1 to 4, wherein the aluminum alloy forged material is an automobile suspension member.

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