Intermediate forging of suspension arms, method for manufacturing suspension arms

Abstract

This invention provides an intermediate forged suspension arm and a method for manufacturing a suspension arm that can suppress the occurrence of shrinkage and sink marks caused by the inner side of the rib being pulled by the excess material during the forging process of the suspension arm. [Solution] A web extending in the longitudinal direction, ribs formed to protrude from the web along the thickness direction of the web from each of the edges on both sides of the web along the longitudinal direction, and excess material protruding from the outer surface of the ribs are integrally formed, and when the outer surface of the ribs is viewed in plan, the thickness D1 of the excess material in the first region where the position of the parting line formed at the joint of the forging die does not coincide with the position of the web is thinner than the thickness D2 of the excess material in the second region where the position of the parting line and the position of the web coincide.

Description

Technical Field

[0001] The present invention relates to an intermediate forging of a suspension arm for a vehicle and a method for manufacturing a suspension arm.

Background Art

[0002] In recent years, aluminum alloys are being increasingly used as structural members in various products, taking advantage of their lightweight properties. For example, automotive undercarriage and bumper parts have hitherto been made of high-tensile steel, but in recent years, high-strength aluminum alloy materials have come to be used. Automobile parts, such as suspension parts, have hitherto been made exclusively of iron-based materials, but are increasingly being replaced with aluminum materials or aluminum alloy materials for the main purpose of weight reduction.

[0003] In an automotive suspension system, the suspension arm is one of the important components, and in recent years, suspension arms have been manufactured using the above-described aluminum alloy materials. In particular, forged suspension arms having an H-shaped or U-shaped cross-sectional shape perpendicular to the longitudinal direction can achieve high strength and durability (see, for example, Patent Document 1).

[0004] The above-described suspension arm is integrally formed with a web extending in the longitudinal direction and ribs protruding along the thickness direction of the web from edge portions on both sides of the web. When manufacturing such a suspension arm, problems such as the occurrence of sink marks and sink mark scratches may occur inside the ribs.

[0005] Specifically, in a region where the position of the parting line formed at a portion corresponding to the joint of the forging die does not coincide with the position of the web, after the rib is formed during forging, the forging material of the inner portion of the rib is pulled by the surplus material portion discharged outward from this rib, causing the inner side of the rib to dent and sink marks and sink mark scratches may occur.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2024-085798 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Conventionally, in forged suspension arms, insufficient measures were taken to prevent sink marks and defects on the inside of the ribs, which could negatively affect the quality of the suspension arms. Therefore, there was a need to effectively suppress the occurrence of sink marks and defects on the inside of the ribs of suspension arms.

[0008] The present invention has been made in view of the above technical background, and provides an intermediate forged suspension arm and a method for manufacturing a suspension arm that can suppress the occurrence of sink marks and sink marks caused by the inside of the rib being pulled by the excess material during the forging of the suspension arm. [Means for solving the problem]

[0009] To solve the above problems, the following means are proposed for the intermediate forged product of a suspension arm and the manufacturing method of the suspension arm according to one embodiment of the present invention. (1) An intermediate forged product of a suspension arm according to embodiment 1 of the present invention is an intermediate forged product of a suspension arm, which is obtained by forging a forging material using a forging die, and comprises a web extending in the longitudinal direction, ribs formed to protrude from the web along the thickness direction of the web from each of the edges on both sides of the web along the longitudinal direction, and excess material protruding from the outer surface of the ribs, wherein when the outer surface of the ribs is viewed in plan, the thickness D1 of the excess material in a first region where the position of the parting line formed at the joint of the forging die and the position of the web do not overlap is thinner than the thickness D2 of the excess material in a second region where the position of the parting line and the position of the web overlap.

[0010] (2) Embodiment 2 of the present invention is an intermediate forged product of the suspension arm of Embodiment 1, wherein the thickness of the excess material satisfies the following formula 1. D1 / D2 < 0.5 ···(1)

[0011] (3) A method for manufacturing a suspension arm according to aspect 3 of the present invention is a method for manufacturing a suspension arm, comprising at least a forging step of forging an intermediate forged product of a suspension arm using a forging die, such that the thickness D1 of the excess material protruding from the outer surface of the suspension arm in a first region where the position of the parting line formed at the joint of the forging die and the position of the web do not overlap when the outer surface of the rib is viewed in plan, is thinner than the thickness D2 of the excess material in a second region where the position of the parting line and the position of the web overlap; and a trimming step of removing the excess material from the intermediate forged product of the suspension arm by trimming to obtain a suspension arm.

[0012] (4) Aspect 4 of the present invention is a method for manufacturing a suspension arm according to aspect 3, wherein the cross section perpendicular to the extension direction of the suspension arm is H-shaped or U-shaped. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide an intermediate forged suspension arm and a method for manufacturing a suspension arm that can suppress the occurrence of sink marks and sink marks caused by the inner side of the rib being pulled by the excess material during the forging of the suspension arm. [Brief explanation of the drawing]

[0014] [Figure 1] This is an external perspective view showing an intermediate forged part of a suspension arm according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view taken along the line A-A' shown in Figure 1. [Figure 3] Figure 1 is a plan view of the intermediate forged part of the suspension arm, as seen from viewpoint Q. [Figure 4] This is an external perspective view showing other examples of suspension arm component shapes. [Figure 5] This is a cross-sectional view showing another example of the cross-sectional shape of a suspension arm member. [Figure 6] This is a flowchart illustrating the manufacturing method of the suspension arm in this embodiment, step by step. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described in detail below with reference to the drawings. Note that, for the sake of clarity, the drawings used in the following description may show enlarged versions of key features, and the dimensional ratios of each component may not be the same as those in reality. Furthermore, the materials, dimensions, etc., exemplified in the following description are merely examples, and the present invention is not necessarily limited to them. It can be implemented with appropriate modifications without altering its effects.

[0016] [Intermediate Forged Product of Suspension Arm] An intermediate forged product of a suspension arm according to an embodiment of the present invention will be described. FIG. 1 is an external perspective view showing an intermediate forged product of a suspension arm according to an embodiment of the present invention. Further, FIG. 2 is a cross-sectional view taken along the line A-A' shown in FIG. 1.

[0017] The intermediate forged product 10 of the suspension arm of the present embodiment (hereinafter simply referred to as the intermediate forged product) is an intermediate product in the intermediate stage of the manufacturing process for manufacturing the suspension arm. More specifically, it is an intermediate forged product obtained by forging a forging material (aluminum alloy) using a forging die.

[0018] As shown in FIG., the intermediate forged product 10 is integrally forged and formed with a suspension member 11, which is a part constituting the suspension arm as the final molded product, and a plate-like surplus portion (flash) 33 that protrudes outward along the outer edge of the suspension member 11.

[0019] [[ID=第十七]]The suspension member 11 generally forms a substantially U-shape, for example, and includes a wheel-side connecting portion 21, a first vehicle-body-side connecting portion 22, a second vehicle-body-side connecting portion 23, a first arm portion 26 connecting the wheel-side connecting portion 21 and the first vehicle-body-side connecting portion 22, and a second arm portion 27 connecting the wheel-side connecting portion 21 and the second vehicle-body-side connecting portion 23. Among these, the first vehicle-body-side connecting portion 22 and the second vehicle-body-side connecting portion 23 are parts also referred to as so-called bush portions.

[0020] As shown in FIGS. 1 and 2, the first arm portion 26 and the second arm portion 27 of the present embodiment have a substantially U-shaped cross-section perpendicular to the longitudinal direction, and include a web 31 extending in this longitudinal direction, and ribs 32 formed so as to protrude upward along the thickness direction T of the web 31 from each of the edges on both sides along the longitudinal direction of the web 31.

[0021] Furthermore, the rib 32 is provided with a flat plate-shaped excess material (flush) 33 that protrudes from its outer surface in a direction perpendicular to the thickness direction T of the web 31. This excess material (flush) 33 is formed to surround the outer edge of the entire suspension member 11, including the first arm portion 26 and the second arm portion 27.

[0022] Figure 3 is a plan view of the intermediate forged part of the suspension arm, viewed from viewpoint Q shown in Figure 1. The intermediate forged product 10 is manufactured in the forging process by, for example, forging an aluminum alloy material between an upper die and a lower die. At this time, a parting line P is formed on the resulting intermediate forged product 10 at the joint between the upper die and the lower die.

[0023] In this embodiment, the intermediate forged product 10 has a first region E1 where the position of the parting line P and the formation position of the web 31 do not overlap when the outer surface of the rib 32 is viewed from above, and a second region E2 where the position of the parting line P and the formation position of the web 31 overlap.

[0024] In the intermediate forged product 10 of this embodiment, the thickness of the excess material (flash) 33 is adjusted to be different in the first region E1 and the second region E2.

[0025] Specifically, the intermediate forged product 10 is formed such that the thickness D1 of the excess material 33a in the first region E1 is thinner than the thickness D2 of the excess material 33b in the second region E2. The connection portion between the excess material 33a in the first region E1 and the excess material 33b in the second region E2 may be formed so that the thickness changes gradually along the extension direction, or it may be changed in a stepped manner at one point.

[0026] More specifically, it is preferable that the thickness D1 of the excess material 33a in the first region E1 and the thickness D2 of the excess material 33b in the second region E2 satisfy the following equation 1. D1 / D2 < 0.5 ···(1)

[0027] As described above, in the intermediate forged product 10 of this embodiment, by making the thickness D1 of the excess material portion 33a in the first region E1 where the position of the parting line P and the position of the web 31 do not overlap thinner than the thickness D2 of the excess material portion 33b in the second region E2 where the position of the parting line P and the position of the web 31 overlap, the stress on the rib 32 that is pulled outward by the excess material portion 33a formed in the part that does not overlap with the web 31 can be reduced in the forging process described later.

[0028] This effectively suppresses deformation on the inside of the rib 32 in the first region E1, i.e., sink marks and sink marks, improving the appearance of the suspension member 11 obtained after removal of the excess material 33, and improving the uniformity of its mechanical properties.

[0029] Furthermore, by suppressing sink marks and scratches on the ribs 32, the structural weaknesses of the suspension member 11 are reduced, allowing it to maintain high durability over a long period of time and improving reliability.

[0030] Furthermore, by suppressing the occurrence of sink marks and scratches on the rib 32, the amount of work required to correct sink marks and scratches, as well as the occurrence of defective products, can be reduced, improving yield and increasing manufacturing efficiency. This improvement in manufacturing efficiency leads to reduced manufacturing costs and enables the stable supply of high-quality products.

[0031] In this embodiment, the suspension member 11 constituting the intermediate forged product 10 has a roughly U-shape overall, but the shape of the suspension arm member is not limited to this. For example, as shown in Figure 4(a), it may be an L-shaped suspension arm member 15, or as shown in Figure 4(b), it may be an I-shaped suspension arm member 16.

[0032] Furthermore, in this embodiment, the cross-section perpendicular to the longitudinal direction of the first arm portion 26 and the second arm portion 27 of the suspension member 11 is substantially U-shaped, but it is not limited to this, and for example, as shown in Figure 5, the suspension arm member may have an arm portion with an H-shaped cross-section.

[0033] [Manufacturing method for suspension arms] Next, we will describe a method for manufacturing a suspension arm according to one embodiment of the present invention. Figure 6 is a flowchart illustrating the manufacturing method of the suspension arm according to this embodiment, step by step.

[0034] In manufacturing the suspension arm according to this embodiment, an aluminum casting material of a predetermined composition, such as an A6061 aluminum alloy material containing Mg and Si, is melted to cast a rod-shaped aluminum alloy, and an aluminum rod material is prepared by subjecting it to a homogenization heat treatment process as needed.

[0035] Then, this aluminum rod is cut to the appropriate length, heated, and bent using a hydraulic processing device or press (bending process S1).

[0036] Next, the aluminum alloy material that has undergone this bending process is roughly processed using a press or the like to create a rough shape, such as a U-shape, to obtain an aluminum alloy material formed into a basic shape (rough processing step S2).

[0037] Next, the rough-machined aluminum alloy material is used to form the intermediate forged part of the suspension arm (forging process S3). In forging process S3, the roughly machined aluminum alloy material (forging material) is heated to a predetermined temperature, and then pressure is applied using a press machine equipped with a forging die to perform die shaping, thereby obtaining an intermediate forged product.

[0038] In this embodiment, a rough-machined aluminum alloy material is forged at a heating temperature of, for example, 450°C to 560°C to form an intermediate forged suspension arm. In this case, it is preferable that the forging start temperature of the forging material be 450°C to 560°C. If the start temperature is below 450°C, the deformation resistance will increase, potentially preventing sufficient machining. On the other hand, if it exceeds 560°C, defects such as forging cracks and eutectic melting may easily occur. Furthermore, it is more preferable that the material temperature of the forging material be within the range of 480°C to 520°C.

[0039] Then, in this forging process S3, when viewing the outer surface of the rib 32 from above, the thickness D1 of the excess material 33a protruding from the outer surface in the first region E1, where the position of the parting line P formed at the joint of the forging die does not overlap with the position of the web 31, is forged using a forging die so that it is thinner than the thickness D2 of the excess material 33b in the second region E2, where the position of the parting line P and the position of the web 31 overlap.

[0040] In this case, for example, it is preferable that the thickness D1 of the excess material 33a in the first region E1 and the thickness D2 of the excess material 33b in the second region E2 satisfy the following equation 1. D1 / D2 < 0.5 ···(1)

[0041] By forging the intermediate forged product 10 into the shape described above in forging process S3, the excess material 33a formed in the portion that does not overlap with the web 31 reduces the stress that pulls the rib 32 outward. This effectively suppresses deformation on the inside of the rib 32 in the first region E1, i.e., sink marks and sink marks.

[0042] Next, the intermediate forged product 10 obtained in the forging process S3 is trimmed (hot trimming process S4). In the hot trimming process S4, which is an example of a trimming process, for example, the intermediate forged product 10 is heated at a temperature of, for example, more than 100°C and less than or equal to 250°C while the excess material (flash) 33 is trimmed (trimming).

[0043] This hot trimming process (trimming process) S4 removes the excess material 33 that protrudes outward along the outer edge of the suspension member 11 that constitutes the intermediate forged product 10, thereby obtaining the suspension member (suspension arm) 11. When this excess material 33 is removed, burrs, which are the traces left by the removal of the base portion of the excess material 33, become exposed on the outer edge of the suspension member 11.

[0044] Furthermore, even after the removal of the excess material portion 33 from the suspension member (suspension arm) 11, it is possible to determine the thickness D1 of the excess material portion 33a in the first region E1 and the thickness D2 of the excess material portion 33b in the second region E2 of the intermediate forged product 10 by measuring the thickness of these burrs.

[0045] Furthermore, in this embodiment, a hot trimming process S4 is performed as an example of a trimming process, but in addition to this, a cold trimming process can also be performed to trim the excess material (flash) 33 from a cooled intermediate forging 10 (for example, at about 60°C).

[0046] After this, it is preferable to perform a solution treatment step S5 on the suspension member (suspension arm) 11 from which the excess material 33 has been removed, for example, by heating it to a temperature of 500°C or higher to induce a solution, thereby relieving the strain introduced in the forging step S3 and causing a solid solution of solute elements. Furthermore, it is preferable to perform a quenching step S6 in which the suspension member 11 in the solid solution state obtained in the solution treatment step is rapidly cooled to form a supersaturated solid solution. Finally, it is preferable to perform an aging treatment step S7 in which the suspension member 11 is heated and held at a relatively low temperature to precipitate the supersaturated solid solution elements and impart appropriate hardness.

[0047] Through the above process, a high-quality suspension member (suspension arm) 11 with high strength and durability can be manufactured, in which deformation on the inside of the rib 32 in the first region E1, i.e., the occurrence of sink marks and sink marks, is effectively suppressed.

[0048] Although one embodiment of the present invention has been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be carried out in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Examples]

[0049] The effects of the present invention were verified. The effect of setting the thickness of the excess material (flash) on the strain inside the rib was analyzed using computer-aided forging simulations. To simplify the calculations, the preceding bending process was omitted, and the analysis was performed on a bent material with only rough machining and finishing (forging) processes. In this simulation, the thickness of the excess material (flash) at the relevant location was set to three patterns: 4 mm, 2 mm, and 1 mm, and the equivalent strain inside the rib was evaluated. The thickness of the excess material (flash) at other locations was set to 4 mm.

[0050] The settings for the forging simulation are as follows: "Material Requirements" Shape: U-shaped forged aluminum suspension arm Material: Aluminum alloy Dimensions: Round bar material with a diameter of 50-60mm and a length of 600-800mm.

[0051] "Forging process" Material preparation: Cut the aforementioned round bar material to the appropriate length and heat it to a temperature suitable for forging. Bending process: Heated rod material is bent using hydraulic equipment or a press. Rough machining: The heated material is roughly machined in a press to form a basic U-shape. Finishing process: After rough machining, the material is further finished (forged) using a press machine to approximate the final shape.

[0052] The analysis revealed that, if the equivalent strain inside the rib is set to 100% when the excess material (flash) thickness is 4 mm, then the equivalent strain inside the rib is 97.8% when the excess material (flash) thickness is 2 mm, and 96.8% when the excess material (flash) thickness is 1 mm. These results confirm that reducing the thickness of the excess material (flash) reduces the considerable strain applied to the ribs, thereby suppressing the occurrence of sink marks on the inside of the ribs. [Industrial applicability]

[0053] The present invention's intermediate forged suspension arm and suspension arm manufacturing method effectively suppress the occurrence of sink marks and sink marks in the suspension arm ribs. This makes it possible to manufacture high-quality, durable suspension arms, contributing to improved driving performance and safety of automobiles. Furthermore, suppressing the occurrence of sink marks and sink marks in the ribs reduces the amount of correction work and defective products. This makes it possible to reduce manufacturing costs and provide high-quality products at competitive prices. Moreover, optimizing the flash thickness using forging simulation can improve the efficiency of the manufacturing process. This is expected to shorten manufacturing time and improve productivity. As described above, the present invention is widely applicable in the automotive industry and contributes to improved quality, cost reduction, and improved manufacturing efficiency. Therefore, it has industrial applicability. [Explanation of symbols]

[0054] 10…Intermediate forging 11…Suspension components (suspension arms) 21...Wheel side connection part 22... First car body side coupling section 23...Second car body side coupling section 26...First arm section 27...Second arm section 31…Web 32... Rib 33... Excess flesh (flash) E1…first area E2…Second Domain

Claims

1. An intermediate forged product of a suspension arm, which is an intermediate product in the manufacturing of a suspension arm, obtained by forging a forging material using a forging die, A web extending in the longitudinal direction, ribs formed to protrude from the web along the thickness direction of the web from each of the edges on both sides of the web along the longitudinal direction, and excess material protruding from the outer surface of the ribs are integrally formed. An intermediate forged suspension arm, wherein, when the outer surface of the rib is viewed from above, the thickness D1 of the excess material in a first region where the position of the parting line formed at the joint of the forging die does not overlap with the position of the web is thinner than the thickness D2 of the excess material in a second region where the position of the parting line and the position of the web overlap.

2. The thickness of the excess material satisfies the following formula 1, wherein this is an intermediate forged product of a suspension arm according to claim 1. D1 / D2<0.5...(1)

3. A method for manufacturing a suspension arm, A forging process for forging an intermediate forged suspension arm using a forging die, wherein a web extending in the longitudinal direction, ribs formed to protrude from the web along the thickness direction of the web from each of the edges on both sides of the web along the longitudinal direction, and excess material protruding from the outer surface of the ribs are integrally formed, and when the outer surface of the ribs is viewed in plan, the thickness D1 of the excess material protruding from the outer surface in a first region where the position of the parting line formed at the joint of the forging die and the position of the web do not coincide is thinner than the thickness D2 of the excess material in a second region where the position of the parting line and the position of the web coincide, A method for manufacturing a suspension arm, comprising at least a trimming step of removing the excess material from the intermediate forged product of the suspension arm by trimming to obtain a suspension arm.

4. The method for manufacturing a suspension arm according to claim 3, wherein the cross-section perpendicular to the extension direction of the suspension arm is H-shaped or U-shaped.

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