Method for manufacturing a forged shaped article

Abstract

Provided is a method for manufacturing a forged product in which quenching distortion of a forged body is suppressed without using an additive or a jig in a quenching process. A method for manufacturing a forged product, characterized in that a forging temperature in a heating process is in a range of 450°C or higher and 550°C or lower, a surface temperature of an upper side molding portion of a first upper die in a first forging process and a surface temperature of an upper side molding portion of a second upper die in a second forging process are each in a range of 150°C or higher and 190°C or lower, and a surface temperature of a lower side molding portion of a first lower die and a surface temperature of a lower side molding portion of a second lower die are each in a range of 190°C or higher and 230°C or lower, and the surface temperature of the lower side molding portion of the first lower die is higher than the surface temperature of the upper side molding portion of the first upper die by 5°C or more, and the surface temperature of the lower side molding portion of the second lower die is higher than the surface temperature of the upper side molding portion of the second upper die by 5°C or more.

Description

Technical Field

[0001] This invention relates to a method for manufacturing forged articles, which is used to manufacture forged articles of suspension arms for automobiles. Background Technology

[0002] In recent years, from the perspective of improving the fuel economy of automobiles through vehicle body lightweighting, suspension arms, such as lower arms or upper arms, which are running gear components of automobiles, have been made of lightweight aluminum alloy forgings. In forging such suspension arms, for example, straight round aluminum alloy raw materials are typically heated to a specified forging temperature and manufactured through two stages of forging: crushing forging and precision forging (see, for example, Patent Documents 1 and 2).

[0003] As demand for such aluminum alloy suspension arms increases, production lines that manufacture suspension arms by hot forging bar-shaped forging raw materials are mass-producing, for example, hundreds of thousands of suspension arms per month. For instance, Patent Document 3 discloses mass production equipment for such suspension arms. Specifically, it automates and efficiently processes numerous steps, from continuously casting aluminum alloy bars with small diameters matching the forging of the suspension arms, to homogenization heat treatment, and finally to hot forging (die forging) processes such as mechanical forging and hydraulic forging.

[0004] The aluminum alloy suspension arms produced in this way constitute the control arms of automotive running gear. Automotive suspension arms often have non-axisymmetric and complex shapes, requiring high strength and fatigue strength comparable to steel materials, while also needing high impact resistance. Therefore, the forging raw material for suspension arms is typically JIS standard 6000 series (Al-Mg-Si series) aluminum alloy. 6000 series aluminum alloys possess high strength and high toughness, as well as excellent corrosion resistance. Furthermore, they have low alloy element content, making it easy to reuse scrap as raw material for melting 6000 series Al alloys, thus exhibiting excellent recyclability.

[0005] As a method for manufacturing such an aluminum alloy suspension arm, Patent Document 4 discloses, for example, that hot forging is performed using an upper die and a lower die. According to this patent document, if the material is aluminum alloy, the die temperature is preferably 100°C to 300°C, and if the material is aluminum alloy, the forging material temperature is preferably 400°C to 550°C.

[0006] Furthermore, the forged aluminum alloy suspension arms undergo tempering processes such as solution treatment, quenching, and artificial aging hardening. In aluminum alloy suspension arms, achieving high strength and high toughness requires careful control of the aluminum alloy composition and microstructure during forging, as well as precise setting of the conditions for solution treatment, quenching, and artificial aging hardening.

[0007] Furthermore, as mentioned above, in the production line of aluminum alloy suspension arms, efficiency in the heat treatment process is also crucial for achieving mass production of hundreds of thousands of units per month. Therefore, to efficiently heat-treat relatively small forgings such as suspension arms, multiple forgings are typically arranged and housed in a case during solution treatment, quenching, and artificial aging hardening processes. Specifically, instead of transferring the forgings within the case to each individual process step, the case itself is placed together with the forgings into the solution treatment furnace, quenching bath, and artificial aging hardening furnace for comprehensive processing.

[0008] Furthermore, in the quenching process, to improve efficiency, these forgings are further stacked vertically in a stacked manner and then submerged in a quenching bath for quenching. In other words, these numerous, stacked aluminum alloy forgings are quenched simultaneously.

[0009] However, as mentioned above, during the quenching process, when relatively small forgings are arranged in a large number within a box and these boxes are stacked together, the temperature distribution of the cooling water used to cool the forgings can easily become uneven, leading to differences in the cooling rates of each forging. This is because, in order to optimize the efficiency of the quenching process, the forgings are housed in a tightly packed arrangement within the box through arrangement and stacking.

[0010] That is, for forgings arranged on the top and central sides within the box, it is difficult to ensure sufficient mutual space (gap, interval) for contact with the relatively low-temperature cooling water supplied recently. Therefore, only the cooling water, which cools the forgings located on the bottom and surrounding sides to become high-temperature, comes into contact with the forgings arranged on the top and central sides. Depending on their arrangement within the box, the temperature of the cooling water in contact with the forgings can sometimes differ.

[0011] On the other hand, in order to forge high-strength suspension arms, the forging body needs to be rapidly cooled during the quenching process after solution treatment. However, the faster the cooling rate during quenching, the more likely quenching deformation (bending of the forging body) will occur. Suspension arms that have undergone quenching deformation may interfere with other components when assembled into a vehicle.

[0012] To suppress quenching deformation during such a quenching process, one could consider increasing the temperature of the cooling water to reduce the cooling rate. However, due to the reduced cooling rate, the suspension arm may not be able to ensure sufficient strength.

[0013] Therefore, for example, Patent Documents 5 and 6 disclose the following: a jig used during quenching to restrain the aluminum alloy forgings individually to suppress deformation. Additionally, it discloses the addition of additives such as ethylene glycol to the cooling water.

[0014] Prior art literature

[0015] [Patent Documents]

[0016] [Patent Document 1] Japanese Patent Application Publication No. 2015-066572

[0017] [Patent Document 2] Japanese Patent Application Publication No. 2011-255404

[0018] [Patent Document 3] Japanese Patent Application Publication No. 2003-019533

[0019] [Patent Document 4] Japanese Patent No. 5483929

[0020] [Patent Document 5] Japanese Patent Application Publication No. 2005-146415

[0021] [Patent Document 6] Japanese Patent Application Publication No. 2005-177861 Summary of the Invention

[0022] However, the quenching deformation prevention jigs disclosed in patent documents 5 and 6 are effective for forgings with simple shapes such as cylindrical shapes. But in forgings with complex shapes like suspension arms, deformation occurs in multiple locations, making it difficult to effectively prevent overall deformation of the suspension arm using jigs. Furthermore, for mass-produced suspension arms, it is impractical to prepare a quantity of quenching deformation prevention jigs commensurate with the production volume from a manufacturing cost perspective.

[0023] On the other hand, in methods that add additives such as ethylene glycol to cooling water, the additives adhere to the forging body and become a cause of contamination. In addition, there are issues such as limited effectiveness in suppressing quenching deformation.

[0024] The purpose of this invention is to provide a method for manufacturing forged products that can suppress quenching deformation of the forged body without using additives or jigs during the quenching process.

[0025] To address the aforementioned issues, the present invention proposes the following solutions.

[0026] That is, the manufacturing method of the forged product of the present invention is used to manufacture forged products of suspension arms for automobiles, characterized in that it includes at least: a heating step, wherein a cylindrical forging material made of aluminum alloy is heated to a forging temperature range; a first forging step, wherein the forging material maintained in the forging temperature range is forged between a first upper die having an upper forming portion and a first lower die having a lower forming portion, which are shaped like a forging, to obtain a first forged body; a second forging step, wherein the first forged body is forged between a second upper die having an upper forming portion and a second lower die having a lower forming portion, which are shaped like a forging, to obtain a second forged body; a solution treatment step, wherein the second forged body is solution treated; a quenching step, wherein the second forged body is quenched; and an age hardening step, wherein the second forged body is hardened. The suspension arm is obtained by age hardening treatment of the body. The forging temperature range in the heating process is above 450°C and below 550°C. The surface temperature of the upper forming part of the first upper die in the first forging process and the surface temperature of the upper forming part of the second upper die in the second forging process are both above 150°C and below 190°C. The surface temperature of the lower forming part of the first lower die and the surface temperature of the lower forming part of the second lower die are both above 190°C and below 230°C. The surface temperature of the lower forming part of the first lower die is more than 5°C higher than the surface temperature of the upper forming part of the first upper die, and the surface temperature of the lower forming part of the second lower die is more than 5°C higher than the surface temperature of the upper forming part of the second upper die.

[0027] According to the present invention, in manufacturing a suspension arm, by setting the surface temperature of the upper forming portion of the first upper die in the first forging process and the surface temperature of the upper forming portion of the second upper die in the second forging process to a range of 150°C or higher and 190°C or lower, and setting the surface temperatures of the lower forming portions of the first lower die and the lower forming portions of the second lower die to a range of 190°C or higher and 230°C or lower, and setting the surface temperature of the lower forming portion of the first lower die to be at least 5°C higher than the surface temperature of the upper forming portion of the first upper die, and setting the surface temperature of the lower forming portion of the second lower die to be at least 5°C higher than the surface temperature of the upper forming portion of the second upper die, deformation of the secondary forged body forged from the forging raw material can be reduced. Therefore, the automotive suspension arm obtained by subjecting the secondary forged body to a heat treatment process including a solution treatment process, a quenching process, and an age hardening process can achieve high strength without deformation for the designed dimensions.

[0028] In addition, in this invention, the forging raw material can also be a forging raw material whose surface has been pre-peeled.

[0029] Furthermore, in this invention, during the solution treatment process, the quenching process, and the age hardening process, multiple secondary forgings can be housed in a storage box that holds them at certain intervals with their lengths parallel to each other.

[0030] In addition, in the present invention, the cooling water used to quench and cool the secondary forging body in the quenching process can be in the range of 60°C or higher and 65°C or lower.

[0031] In addition, in this invention, the aluminum alloy may be a 6000 series aluminum alloy.

[0032] According to the present invention, a method for manufacturing forged articles is provided that can suppress quenching deformation of the forged body without using additives and fixtures during the quenching process. Attached Figure Description

[0033] Figure 1 This is a perspective view showing an example of an automotive suspension arm formed using a forging method according to an embodiment of the present invention.

[0034] Figure 2 This is a flowchart illustrating a method for manufacturing a forged article according to one embodiment of the present invention.

[0035] Figure 3 It is a three-dimensional view showing the appearance of the molds used in the first and second forging processes.

[0036] Figure 4 This is a plan view showing an example of a storage box used in a heat treatment process.

[0037] Figure 5 This is an explanatory diagram illustrating the method for measuring deformation in the verification example.

[0038] Figure 6 This is a graph representing the results of the verification example.

[0039] Explanation of reference numerals in the attached figures

[0040] 11…First mold

[0041] 11a…Upper molding part

[0042] 12…First mold

[0043] 12a…lower molding section

[0044] 21…Second upper mold

[0045] 21a…Upper molding part

[0046] 22…Second mold

[0047] 22a…Lower side molding part

[0048] 100… Suspension arm Detailed Implementation

[0049] The following description, with reference to the accompanying drawings, describes a method for manufacturing a forged article according to one embodiment of the present invention. Furthermore, the embodiments shown below are specifically described to better understand the gist of the invention, and are not intended to limit the invention unless otherwise specified. Additionally, the accompanying drawings used in the following description, for ease of understanding of the features of the invention, sometimes show enlarged portions of key parts, and the dimensional ratios of the constituent elements may not be identical to the actual dimensions.

[0050] In the following embodiments, forging is, for example... Figure 1 The image shows a suspension arm 100 for automobiles in the form shown. This suspension arm 100 is used to control the movement of the automobile wheels and is also called a control arm. Typically, one suspension arm 100 is installed on each side of the vehicle, and they are usually arranged along the direction of travel. However, sometimes three to five arms are used to counteract lateral forces. Therefore, the suspension arm 100 needs to be high-strength and lightweight.

[0051] Figure 2 This is a flowchart illustrating a method for manufacturing a forged article according to one embodiment of the present invention.

[0052] The manufacturing method of the forged product of this embodiment for manufacturing the suspension arm 100 as described above includes the following steps in sequence: a heating step S1 of heating the forging material to a forging temperature range; a primary forging step S2 of forging the forging material between a first upper die and a first lower die to obtain a primary forging body; a secondary forging step S3 of forging the primary forging body between a second upper die and a second lower die to obtain a secondary forging body; a solution treatment step S4 of solution treatment of the secondary forging body; a quenching step S5 of quenching treatment of the secondary forging body; and an age hardening step S6 of age hardening treatment of the secondary forging body.

[0053] The forging raw material used to manufacture the suspension arm 100 using the forging method of this embodiment can be any aluminum alloy that is formed into a cylindrical (bar-shaped) form. For example, its dimensions are approximately 40-60 mm in diameter and 500-600 mm in length. The aluminum alloy can be, for example, a 6000 series aluminum alloy as specified in JIS. For example, its composition can be an Al-Mg-Si alloy containing Si: 0.65-0.80 wt%, Fe: 0.20-0.40 wt%, Cu: 0.27-0.40 wt%, Mn: 0.08-0.15 wt%, Mg: 0.97-1.20 wt%, Cr: 0.20-0.30 wt%, with the balance being Al and unavoidable impurities. It may also further contain B: 0.0001-0.03 wt%.

[0054] For such forging raw materials, it is preferable to first perform a peeling process by grinding the outer peripheral surface to a specified thickness to remove the oxide film and make the peripheral surface smooth.

[0055] In heating step S1, the forging material described above is heated to the forging temperature range. Regarding heating, a heating furnace can be used to heat most of the forging material together. The forging temperature range of the forging material is 450°C or higher and 550°C or lower; in this embodiment, the forging material is heated to 500°C. Heating the forging material in this way increases its plasticity and fluidity.

[0056] Figure 3 It is a perspective view showing the appearance of the molds used in the first forging process S2 and the second forging process S3.

[0057] The first forging process S2, referred to as rough forming, involves forging the forging material, which has been heated to the forging temperature range in the heating process S1, into the approximate shape of the cantilever arm 100 as a forging. In this first forging process S2, a first upper die 11 and a first lower die 12 are used.

[0058] The first lower die 12 is a fixed die fixed to a horizontal platform or the like, and has a lower forming portion 12a that imitates the shape of the lower half of the suspension arm 100, which is a forging part. The lower forming portion 12a can be any recessed portion that opens on the side facing the first upper die 11. During forging, forging material heated to the forging temperature range is placed on the lower forming portion 12a.

[0059] The first upper die 11 is a movable die capable of moving up and down along the vertical direction. It moves up and down between its upper stop and its lower stop, which contacts the first lower die 12, via a vertical movement mechanism (not shown) such as a hydraulic cylinder. The first upper die 11 has an upper forming portion 11a, primarily the upper half of a suspension arm 100 used as a forging. The upper forming portion 11a can simply be a recessed portion that opens on the side facing the first lower die 12.

[0060] In a single forging process S2, the surface temperature of the upper forming portion 11a of the first upper die 11, as described above, is heated to a range of 150°C or higher and 190°C or lower. Furthermore, the surface temperature of the lower forming portion 12a of the first lower die 12 is heated to a range of 190°C or higher and 230°C or lower. At this time, the surface temperature of the lower forming portion 12a of the first lower die 12 is at least 5°C higher than the surface temperature of the upper forming portion 11a of the first upper die 11.

[0061] As an example, in a forging process S2, the surface temperature of the upper forming part 11a of the first upper die 11 is set to 150°C, the surface temperature of the lower forming part 12a of the first lower die 12 is set to 190°C, and the temperature difference is set to 40°C.

[0062] Based on heating the first upper die 11 and the first lower die 12 to a predetermined temperature, the forging material heated to the forging temperature range is placed in the lower forming part 12a of the first lower die 12, and the first upper die 11 is lowered in the vertical direction to the lower stop point that contacts the first lower die 12. As a result, the cylindrical forging material flows in a manner that expands within the forming space formed by the upper forming part 11a and the lower forming part 12a, thereby obtaining a primary forging body that is approximately shaped like a suspension arm 100.

[0063] The resulting forged body is then subjected to the subsequent secondary forging process S3 while maintaining the temperature within the forging temperature range.

[0064] The secondary forging process S3, also known as precision forming, involves forging the primary forging body within its forging temperature range to achieve the designed shape of the cantilever arm 100 as the forging part. In this secondary forging process S3, a second upper die 21 and a second lower die 22 are used.

[0065] The second lower die 22 is a fixed die fixed to a horizontal platform or the like, and has a lower forming part 22a that imitates the shape of the lower half of the suspension arm 100, which is a forged part. The lower forming part 22a can be any recessed part that opens on the side facing the second upper die 21. During forging, the primary forging body, which is within the forging temperature range, is placed on the lower forming part 22a.

[0066] The second upper die 21 is a movable die capable of moving up and down along the vertical direction. It moves up and down between its upper stop and its lower stop, which contacts the second lower die 22, via a vertical movement mechanism (not shown) such as a hydraulic cylinder. The second upper die 21 has an upper forming portion 21a, primarily the upper half of a suspension arm 100 used as a forging. The upper forming portion 21a is simply a recessed portion that opens on the side facing the second lower die 22.

[0067] In the secondary forging process S3, the surface temperature of the upper forming portion 21a of the second upper die 21, as described above, is heated to a range of 150°C or higher and 190°C or lower. Furthermore, the surface temperature of the lower forming portion 22a of the second lower die 22 is heated to a range of 190°C or higher and 230°C or lower. At this time, the surface temperature of the lower forming portion 22a of the second lower die 22 is at least 5°C higher than the surface temperature of the upper forming portion 21a of the second upper die 21.

[0068] As an example, in the secondary forging process S3, the surface temperature of the upper forming part 21a of the second upper die 21 is set to 160°C, the surface temperature of the lower forming part 22a of the second lower die 22 is set to 200°C, and the temperature difference is set to 40°C.

[0069] Based on heating the second upper die 21 and the second lower die 22 to a specified temperature, the primary forging body, which is within the forging temperature range, is placed on the lower forming part 22a of the second lower die 22. The second upper die 21 is lowered vertically to the lower stop point where it contacts the second lower die 22. As a result, the primary forging body undergoes metal flow within the forming space formed by the upper forming part 21a and the lower forming part 22a, thereby obtaining a secondary forging body that is precisely forged into the shape of the suspension arm 100.

[0070] The secondary forged body, after undergoing the secondary forging process S3, is, for example, at approximately 350°C. This secondary forged body is then naturally cooled to 300°C at room temperature, and subsequently cooled from 300°C to room temperature using air cooling based on forced draft. During this cooling process, the secondary forged body preferably maintains the same posture as during forging. Afterward, burrs and excess material generated during forging are removed from the secondary forged body.

[0071] Next, the secondary forging body is processed in the following order as heat treatment processes: solution treatment S4, quenching S5, and age hardening S6.

[0072] Solution treatment process S4 is a process that uniformly dissolves undissolved elements in the aluminum alloy, thereby improving corrosion resistance and other properties. In solution treatment process S4, the secondary forging body is heated to the solution treatment temperature using, for example, a heating furnace. In the case of aluminum alloy, heating to, for example, a range of 500°C or higher and 530°C or lower is sufficient.

[0073] In the quenching process S5, the secondary forging body, which was heated to the solution temperature in the previous solution treatment process S4, is rapidly quenched and cooled using cooling water. It is preferable that the temperature of the cooling water be in the range of 60°C or higher and 65°C or lower.

[0074] In the quenching process S5, the secondary forging body, heated to the solution temperature, is immersed in the cooling water very quickly. Therefore, when the cooling water temperature is below 60°C, the arm portions 100a, 100b, and 100c of the cantilever arm 100 (refer to...) exist as the secondary forging body. Figure 1 There are concerns about deformation during quenching. Additionally, if the cooling water temperature exceeds 65°C, there is a concern that the rapid cooling effect will be reduced. Therefore, systems such as warm water circulation systems and heaters are used to maintain the cooling water temperature in the tank between 60°C and 65°C.

[0075] The aging hardening process S6 is a process in which the secondary forging body, which has undergone the quenching process S5 (the preceding process), is artificially aged in an artificial aging hardening furnace. This allows elements that have dissolved through supersaturation to precipitate artificially, increasing the hardness of the secondary forging body through crystal strain.

[0076] This age hardening process S6 can be carried out by heating the secondary forging body that has undergone the quenching process S5 to, for example, about 200°C.

[0077] In the heat treatment process that includes the solution treatment step S4, quenching step S5, and age hardening step S6 described above, for example, in order to carry out mass production of hundreds of thousands of suspension arms per month, it is preferable that: in the case of Figure 4 When a large number of secondary forgings are contained in the heat treatment storage box 110 as shown, the secondary forgings are not transferred in the solution treatment process S4, the quenching process S5, and the age hardening process S6. Instead, the heat treatment processes are carried out with the storage box intact or together with the storage box.

[0078] The storage box 110 is made of a heat-resistant metal, for example, and contains a number of secondary forgings that are spaced apart in a parallel manner along their length. Such a storage box 110 only needs to have a structure that allows hot and cooling water to easily enter the interior.

[0079] By using such a storage box 110 in the heat treatment process, relatively small secondary forgings such as suspension arms can be grouped together for efficient heat treatment, thereby improving the productivity of suspension arms.

[0080] Through the above processes, the suspension arm 100 for automobiles can be manufactured from forging raw materials.

[0081] As described above, in the method for manufacturing a forged product according to an embodiment of the present invention, when forging a suspension arm 100 for automobiles, the surface temperature of the upper forming portion 11a of the first upper die 11 in the first forging step S2 and the surface temperature of the upper forming portion 21a of the second upper die 21 in the second forging step S3 are respectively set to a range of 150°C or higher and 190°C or lower. Furthermore, the surface temperature of the lower forming portion 12a of the first lower die 12 and the surface temperature of the second lower die 22 are also set to a range of 150°C or higher and 190°C or lower. The surface temperatures of the lower forming portions 22a are set to a range of 190°C or higher and 230°C or lower. Furthermore, the surface temperature of the lower forming portion 12a of the first lower die 12 is set to be at least 5°C higher than the surface temperature of the upper forming portion 11a of the first upper die 11, and the surface temperature of the lower forming portion 22a of the second lower die 22 is set to be at least 5°C higher than the surface temperature of the upper forming portion 21a of the second upper die 21. This reduces deformation in the secondary forged body forged from the forging raw material. Consequently, the automotive suspension arm 100 obtained by the secondary forged body through a heat treatment process including a solution treatment process S4, a quenching process S5, and an age hardening process S6 can achieve the designed dimensions without deformation and with high strength.

[0082] The embodiments of the present invention have been described above, but such embodiments are provided as examples and are not intended to limit the scope of the invention. Such embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are also included within the scope of the invention as described in the claims and its equivalents.

[0083] [Example]

[0084] The effectiveness of the present invention has been verified.

[0085] <Example 1 of the present invention>

[0086] Prepare a cylindrical aluminum alloy forging material (48mm in diameter, 543mm in length) that has undergone pre-peeling treatment, and heat the forging material to 500℃ (heating process). Then, for the heated forging material... Figure 2 The surface temperature of the forming part of the first upper mold shown is set to 150°C, and the surface temperature of the forming part of the first lower mold is set to 230°C to perform rough forming (one forging process) and obtain a one-time forged body.

[0087] Next, for this forged body, Figure 2 The surface temperature of the forming part of the second upper die shown is set to 150°C, and the surface temperature of the forming part of the second lower die is set to 230°C for precision forming (secondary forging process) to obtain a secondary forged body. Then, the secondary forged body, which is approximately 350°C after the secondary forging process, is cooled to 300°C by natural cooling, and then further cooled to 50°C by air cooling based on a fan. At this point, the ambient temperature remains at room temperature, and the posture of the secondary forged body is maintained. Then, the cooled secondary forged body is trimmed to remove burrs and excess material, producing a finished product. Figure 1 The shape of the secondary forged body shown.

[0088] Then, the secondary forged body is heat-treated in the same order as the above-described embodiments, following the solution treatment process, quenching process, and age hardening process, to obtain the suspension arm of Example 1 of the present invention.

[0089] <Comparative Example 1>

[0090] As a prior comparative example 1, the surface temperature of the forming part of the first upper die was set to 230°C, and the surface temperature of the forming part of the first lower die was set to 150°C for rough forming (one forging process). The surface temperature of the forming part of the second upper die was set to 230°C, and the surface temperature of the forming part of the second lower die was set to 150°C for fine forming (two forging processes). Otherwise, the same manufacturing conditions as in Example 1 of the present invention were used.

[0091] <Comparative Example 2>

[0092] As a prior comparative example 2, the surface temperature of the forming part of the first upper die and the surface temperature of the forming part of the first lower die were both set to 190°C for rough forming (one forging process), and the surface temperature of the forming part of the second upper die and the surface temperature of the forming part of the second lower die were both set to 190°C for fine forming (two forging processes). Otherwise, the same manufacturing conditions as in Example 1 of the present invention were used.

[0093] The deformation of each suspension arm of Example 1, Comparative Example 1, and 2 of the present invention, obtained as described above, was measured.

[0094] During the measurement, use Figure 5 The measuring device G shown is used to measure the height at points g1, g2, and g3. The length is measured at g4, and the width... Figure 5 The positioning (in the depth direction) is carried out at g5 and g6. The deformation is measured at the point of greatest bending (g6) of each suspension arm using a linear gauge in the vertical direction. The evaluation method is to use a standard sample with a design deformation of "0" to adjust the linear gauge to zero point, and the difference from the standard sample is taken as the deformation.

[0095] exist Figure 6 The results of such deformation measurements are illustrated using charts.

[0096] according to Figure 6 The deformation measurement results shown indicate that the suspension arm of Example 1 of the present invention, obtained using the forging method of this embodiment, has a deformation value limited to -0.01 mm. On the other hand, the suspension arm of Comparative Example 1 has a deformation value of -0.20 mm, and the suspension arm of Comparative Example 2 has a deformation value of 0.07 mm, both of which exhibit larger deformations than those of Example 1 of the present invention.

[0097] Therefore, it can be confirmed that the manufacturing method of the forged product according to this embodiment can produce a suspension arm with less error relative to the design value and suppressed deformation.

[0098] Industrial availability

[0099] The method for manufacturing forged products of the present invention enables the production of automotive suspension arms with minimal deformation using bar-shaped forging raw materials. Therefore, it has industrial applicability.

Claims

1. A method for manufacturing a forged product, used for manufacturing forged products of suspension arms for automobiles, characterized in that, At least have: The heating process involves heating the cylindrical forging material, made of aluminum alloy, to the forging temperature range. In a single forging process, the forging material, maintained within the forging temperature range, is forged between a first upper die having an upper forming portion and a first lower die having a lower forming portion, which are modeled after the shape of a forging, to obtain a single forging body. The secondary forging process involves forging the primary forging body between a second upper die having an upper forming part and a second lower die having a lower forming part, which are modeled after the shape of the forging, to obtain the secondary forging body. The solution treatment process involves treating the secondary forging body with a solution. The quenching process involves quenching the secondary forging body. and The age-hardening process involves subjecting the secondary forged body to age-hardening treatment to obtain the suspension arm. The forging temperature range in the heating process is above 450°C and below 550°C. In the first forging process, the surface temperature of the upper forming part of the first upper die and the surface temperature of the upper forming part of the second upper die in the second forging process are both in the range of 150°C or higher and 190°C or lower. In addition, the surface temperature of the lower forming part of the first lower die and the surface temperature of the lower forming part of the second lower die are both in the range of 190°C or higher and 230°C or lower. Furthermore, the surface temperature of the lower forming part of the first lower die is more than 5°C higher than the surface temperature of the upper forming part of the first upper die, and the surface temperature of the lower forming part of the second lower die is more than 5°C higher than the surface temperature of the upper forming part of the second upper die.

2. The method for manufacturing forged articles according to claim 1, characterized in that, The forging material is a forging material whose surface has been pre-peeled.

3. The method for manufacturing a forged product according to claim 1, characterized in that, In the solution treatment process, the quenching process, and the age hardening process, multiple secondary forgings are stored in a storage box that holds them at certain intervals with them parallel to each other in the length direction.

4. The method for manufacturing a forged product according to claim 2, characterized in that, In the solution treatment process, the quenching process, and the age hardening process, multiple secondary forgings are stored in a storage box that holds them at certain intervals with them parallel to each other in the length direction.

5. The method for manufacturing a forged article according to any one of claims 1 to 4, characterized in that, In the quenching process, the temperature of the cooling water used to quench and cool the secondary forging body is in the range of 60°C or higher and 65°C or lower.

6. The method for manufacturing a forged article according to any one of claims 1 to 4, characterized in that, The aluminum alloy is a 6000 series aluminum alloy.

7. The method for manufacturing a forged product according to claim 5, characterized in that, The aluminum alloy is a 6000 series aluminum alloy.

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