Commercial vehicle connecting rod small flash forging process
The commercial vehicle connecting rod small flash forging process, which uses five-pass roll forging and a refined flattening die design, solves the problems of low material utilization and short die life, achieving the effects of material saving and extended die life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-03-24
AI Technical Summary
The existing forging process for connecting rods in commercial vehicles has low material utilization and short die life. This is mainly due to the limitations of roll forging dies in obtaining suitable billets and the material waste and severe die wear caused by the design differences between flattening dies and pre-forging.
The process employs a five-pass roll forging process and a refined flattening die design. By reducing flash width and volume, and combining a single-compartment pre-forging die and a final forging die, the forging process is optimized to reduce material consumption and extend die life.
It improved material utilization by 8%, increased mold life by 30%, reduced flash width and volume, saved raw material costs, reduced impact force, and extended mold life.
Smart Images
Figure CN121715501A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of automotive parts manufacturing technology, and in particular to a forging process for small flash on connecting rods of commercial vehicles. Background Technology
[0002] Connecting rods are a crucial component of commercial vehicle engines, converting piston thrust into crankshaft rotational torque. Due to the extremely harsh operating environment of engines, connecting rods must be forged to achieve optimal metal flow lines, ensuring good strength and toughness. However, current technologies suffer from limitations in roll forging and die forging die design, resulting in low material utilization rates for connecting rod products, typically around 70%. Furthermore, the die lifespan is relatively short, generally around 5000 pieces.
[0003] However, there are several reasons for the above situation, including: limitations of the roll forging die prevent the acquisition of suitable billets, resulting in significant material waste; and the large difference between the flattening die design and the pre-forging die design leads to die erosion during pre-forging, severely impacting die life. In the production of connecting rods, material waste is concentrated on flash and connecting skin. Since the diameter of the connecting skin is determined by the connecting rod's structure and cannot be changed, the key to improving the material utilization rate of connecting rods lies in shortening the length of flash, ultimately reducing material usage. Summary of the Invention
[0004] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a small flash forging process for commercial vehicle connecting rods, which reduces the volume of flash and the amount of material used by ensuring that the forging is fully filled, thereby solving the problems of low material utilization and short die life in traditional forging processes.
[0005] This invention provides a forging process for small flash on connecting rods of commercial vehicles, comprising: The billet forging process involves five passes of rolling in a forging die to deform and extend the round bar along its axial direction. This causes the cross-sectional shape of the round bar, corresponding to the connecting rod body, the connection between the connecting rod body and the large end, and the connection between the connecting rod body and the small end, to change sequentially from elliptical to circular to elliptical to circular to obtain the forging billet. Forming and flattening process: The forging blank is flattened using a flattening mold to obtain a flattened part, wherein the height of the flattened part is 2-5mm larger than the height of the pre-forging part, the width of the flattened part is 1-2mm smaller than the width of the pre-forging part, the cross-sectional area of each position of the flattened part is larger than the corresponding cross-sectional area of the pre-forging part, and the fillet radius of each position of the flattened part is one size larger than the corresponding fillet radius of the pre-forging part; Pre-forging and final forging processes: The flattened part is subjected to pre-forging and final forging processes to obtain pre-forged part and final forged part in sequence.
[0006] The commercial vehicle connecting rod flash forging process according to embodiments of the present invention has at least the following beneficial effects: the flash width formed by the forging blank corresponding to the area where the connecting rod body connects to the big end and the area where the connecting rod body connects to the small end is usually large. Therefore, by using five-pass roll forging, the cross-sectional shape of the round bar material changes from circle to ellipse, circle, ellipse, circle and circle in sequence, and its cross-sectional area gradually decreases, making the diameter of the area where the forging blank corresponds to the connecting rod body narrower, and the angle of the area where the forging blank corresponds to the area where the connecting rod body connects to the big end and the area where the connecting rod body connects to the small end is steeper, making less material used at the connection between the big end and the connecting rod body, the connecting rod body, and the connection between the small end and the connecting rod body, significantly reducing the flash width discharged in the final forging process at these locations.
[0007] Furthermore, the flattening process follows the principle of "slender and tall," designing the height of the flattened part to be 2-5mm larger than that of the pre-forged part, the width of the flattened part to be 1-2mm smaller than that of the pre-forged part, the cross-sectional area of each position of the flattened part to be larger than the corresponding cross-sectional area of the pre-forged part, and the fillet radius of each position of the flattened part to be one size larger than the corresponding fillet radius of the pre-forged part. This makes the flattened part narrower and thicker than the pre-forged part, closer to the shape of the finished part, resulting in more precise material distribution, reduced wear on the pre-forging die, reduced flash width, and extended die life. Simultaneously, the pre-forging process pre-fills areas that are difficult to fill, preventing creases and ensuring high-quality connecting rods. Therefore, while ensuring the forging is fully filled, it reduces flash volume, saves material, and effectively overcomes the problems of low material utilization and short die life in traditional forging processes.
[0008] In some embodiments of the present invention, the pre-forging and final forging processes performed on the flattened part to obtain a pre-forged part and a final forged part sequentially include the following steps: The flattened part is forged using a pre-forging die with a single-compartment design to obtain a pre-forged part; The pre-forged part is forged using a single-compartment final forging die to obtain a final forging of a connecting rod with a small flash. The height of the pre-forged part is 1-1.2 mm larger than the height of the final forging, and the width of the pre-forged part is 0.5-1.2 mm smaller than the width of the final forging.
[0009] In some embodiments of the present invention, the volume change ratio of the pre-forging to the final forging is reduced from 6%-7% to 3%-5%.
[0010] In some embodiments of the present invention, the forging process of the flattened part using a single-compartment pre-forging die to obtain a pre-forging part includes the following steps: The flattened part is forged by using a pre-forging lower die and a pre-forging upper die with a storage compartment to obtain a pre-forged part.
[0011] In some embodiments of the present invention, the forging process of the pre-forging part using a single-compartment final forging die to obtain a final forging of the connecting rod with a small flash includes the following steps: The pre-forged part is forged by using the lower final forging die and the upper final forging die with the housing part to obtain the final forging part.
[0012] In some embodiments of the present invention, the following steps are included before the billet rolling forging process: Forging design process: Increase the thickness of the connecting rod's big end, small end, and wedge-shaped plane from 3mm to 2mm; increase the inner diameter of the connecting rod's big end and small end from 6mm to 5mm; increase the punching diameter of the connecting rod from 12mm to 10mm; increase the thickness of the connecting rod's body by 0.5mm; and increase the thickness of the connecting rod's web by 0.3mm.
[0013] In some embodiments of the present invention, the following steps are included before the billet rolling forging process: The process for determining the diameter of round bar stock is as follows: the flash width at the maximum cross-section of the final forging is set from 20-35mm to 10-20mm, and the flash thickness at the maximum cross-section of the final forging is set from 5-6mm to 4mm.
[0014] In some embodiments of the present invention, the forging process for small flash of commercial vehicle connecting rods further includes: Ejector rod arrangement process: If the diameter of the small end inner hole of the connecting rod is smaller than the set value, an ejector rod is arranged on each side of the connecting rod's large end connecting skin and the connecting rod body in the final forging lower die, so that the ejector rod can eject the final forging. Among them, the ejector rods corresponding to the two sides of the connecting rod body are placed on the flash bridge of the final forging lower die; If the diameter of the small end inner hole of the connecting rod is greater than or equal to the set value, an ejector rod is arranged on each side of the connecting rod's large end connecting skin and the small end connecting skin in the final forging lower die, so that the ejector rod can eject the final forging.
[0015] In some embodiments of the present invention, the upper end of the top rod corresponding to the large end connecting skin and the small end connecting skin of the connecting rod adopts a frustum-shaped structure with a large upper end and a small lower end.
[0016] In some embodiments of the present invention, a walking beam is used to transfer and place the workpieces along the billet rolling process, the forming and flattening process, and the pre-forging and final forging process.
[0017] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the description, claims, and drawings. Attached Figure Description
[0018] Figure 1 This is a schematic diagram of the specific process of small flash forging of commercial vehicle connecting rods according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the specific process of step S30 in the small flash forging process of commercial vehicle connecting rods according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the specific process of forging small flash for commercial vehicle connecting rods according to another embodiment of the present invention; Figure 4 This is a schematic diagram of the specific process of the pushrod arrangement step in the small flash forging process of commercial vehicle connecting rods according to an embodiment of the present invention. Figure 5 This is a structural schematic diagram of the connecting rod forging provided according to an embodiment of the present invention, viewed from a cross-sectional angle. Figure 6 This is a schematic diagram of the maximum cross-section of the connecting rod forging provided according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the structure of the connecting rod forging provided according to an embodiment of the present invention from a side view angle; Figure 8 This is a cross-sectional area curve of a connecting rod forging provided according to an embodiment of the present invention; Figure 9 This is a cross-sectional area curve of a connecting rod with flash forging provided according to an embodiment of the present invention; Figure 10 This is an ideal forging billet drawing provided according to an embodiment of the present invention; Figure 11 This is a schematic diagram of the structure of a five-pass roll forging die provided according to an embodiment of the present invention; Figure 12 This is a schematic diagram of the cross-section of a round bar in the prior art when it undergoes four round forging processes. Figure 13 This is a schematic diagram of the cross-section of a round bar material according to an embodiment of the present invention after undergoing five round forging processes; Figure 14 This is a cross-sectional comparison diagram of a flattened part and a pre-forged part provided according to an embodiment of the present invention; Figure 15 This is a schematic diagram of the chamber of a pre-forging die provided according to an embodiment of the present invention; Figure 16This is a cross-sectional comparison diagram of a pre-forging and a final forging provided according to an embodiment of the present invention; Figure 17 This is a schematic diagram of the arrangement of the top rods according to an embodiment of the present invention; Figure 18 This is a structural schematic diagram of the tapered top rod provided according to an embodiment of the present invention. Detailed Implementation
[0019] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.
[0020] In the description of this invention, it should be understood that the use of terms such as "first" and "second" may explicitly or implicitly include one or more of those features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.
[0021] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0022] As a crucial component of commercial vehicle engines, connecting rods convert the piston's thrust into crankshaft rotational torque. However, due to the extremely harsh operating environment of engines, connecting rods must be forged to achieve optimal metal flow lines, ensuring excellent strength and toughness. In existing technologies, deficiencies in roll forging die design and die forging die design result in low material utilization rates for connecting rod products, typically around 70%; furthermore, the die life is relatively short, generally limited to 5000 pieces.
[0023] The main reasons for the above situation include: Firstly, the existing process has low requirements for the precision of component placement, often resulting in larger billet specifications required for actual production, while maintaining product quality, thus leading to low material utilization. Secondly, limitations of the roll forging die prevent the acquisition of suitable billets, resulting in significant material waste. Thirdly, the design of the flattening die differs greatly from that of the pre-forging die, causing the die to be eroded by the billet during pre-forging, severely impacting die life. In connecting rod production, material waste is concentrated on flash and connecting skin. Since the diameter of the connecting skin is determined by the connecting rod product structure and cannot be changed, improving the material utilization rate of connecting rod products focuses on shortening the length of flash, ultimately reducing material usage.
[0024] Based on this, the present invention provides a small flash forging process for commercial vehicle connecting rods. By reducing the volume of flash while ensuring that the forging is fully filled, the amount of material used in the connecting rod production process is reduced, thus solving the problems of low material utilization and short mold life in traditional forging processes.
[0025] The following is for reference. Figures 1 to 18 This invention describes a forging process for small flash on connecting rods of commercial vehicles according to an embodiment of the present invention.
[0026] like Figures 1 to 4 As shown, the small flash forging process for commercial vehicle connecting rods according to an embodiment of the present invention can be applied to the manufacturing of commercial vehicle connecting rods.
[0027] like Figure 1 As shown, the forging process for small flash on commercial vehicle connecting rods includes the following steps: Step S10: Billet forging process: The round bar is deformed and extended along its axial direction by five rolling passes of the forging die, so that the cross-sectional shape of the round bar corresponding to the connecting rod body, the connection between the rod body and the big end, and the connection between the rod body and the small end changes sequentially from elliptical to round to elliptical to round to round, thereby obtaining the forging billet.
[0028] Step S20: Forming and flattening process: The forging blank is flattened using a flattening die to obtain a flattened part. The height of the flattened part is 2-5mm larger than that of the pre-forging part, the width of the flattened part is 1-2mm smaller than that of the pre-forging part, the cross-sectional area of each position of the flattened part is larger than that of the corresponding position of the pre-forging part, and the fillet radius of each position of the flattened part is one size larger than that of the corresponding position of the pre-forging part.
[0029] Step S30: Pre-forging and final forging process: The flattened part is pre-forged and final forged to obtain the pre-forged part and the final forged part in sequence.
[0030] It is understandable that in the billet forging process of step S10, such as Figures 7 to 10As shown, the roll forging process uses a roll forging machine and roll forging dies to precisely divide the round bar stock along its axial direction, resulting in a connecting rod forging with as uniform a flash as possible and a minimum width. For connecting rod forgings, the forging has a maximum cross-sectional area Amax and a minimum cross-sectional area Amin, as shown... Figure 8 As shown; for connecting rod forgings with flash, the connecting rod forgings with flash have the largest cross-sectional area A'max and the smallest cross-sectional area A'min, as shown. Figure 9 As shown; where A'max equals the sum of Amax and the burr width, and A'min equals the sum of Amin and the burr width.
[0031] like Figure 10 As shown, an ideal forging billet can be divided into five regions along its axial direction, specifically regions A, B, C, D, and E. Region A corresponds to the large end of the connecting rod, region B corresponds to the connection between the large end and the rod body, region C corresponds to the rod body, region D corresponds to the connection between the small end and the rod body, and region E corresponds to the small end of the connecting rod. Region A is the clamping part of the roll forging mill and does not participate in the forming of the forging billet (or roll blank). The flash width formed in regions B and D is usually relatively large; therefore, in this embodiment, the focus of the billet rolling forging process is to optimize regions B, C, and D to reduce the formed flash.
[0032] like Figures 10 to 13 As shown, this embodiment increases the original four-pass roll forging process to five passes, using a five-pass roll forging die. Simultaneously, the cavity system of the five-pass roll forging die is improved, changing from the original circle→square→circle→square→circle to circle→ellipse→circle→ellipse→circle→circle. This ensures that the areas of the connecting rod body, the connection between the body and the big end, and the connection between the body and the small end of the round bar stock all begin with a circular cross-section and sequentially undergo ellipse→circle→ellipse→circle→circle cross-sectional shape changes. This allows for a narrower diameter in region C and steeper angles in regions B and D. Specifically, the necking ratio of regions A and C in the original process is increased from 40% to 50%, and the angles of regions B and D are changed from ≥60° to ≥45°. This improvement reduces the amount of material used at the connection between the big end and the body, the body itself, and the connection between the body and the small end of the connecting rod, significantly reducing the width of the flash discharged during final forging at these locations.
[0033] Traditional flattening dies have simple structures, only allowing for basic material separation of the billet. Furthermore, the larger end of the forging is wider, requiring more material and resulting in larger flash. Simultaneously, the pre-forging process causes significant erosion and wear on the pre-forging die, severely impacting its lifespan, and also hinders the filling of complex structural areas. In step S20, the forming flattening process, compared to traditional flattening, allows for earlier forming of the difficult-to-form larger end of the connecting rod, and limits premature expansion of the billet into the flash area. This embodiment optimizes the flattening die cavity, resulting in a more refined structure that allows the flattened part to more closely resemble the finished part shape, enabling more precise material separation, reducing wear on the pre-forging die, increasing its lifespan by nearly 30%, and reducing the width of the flash. It also ensures that difficult-to-fill areas in the pre-forging die are pre-filled, preventing creases and ultimately guaranteeing high-quality finished connecting rods.
[0034] The flattening design follows the principle of slenderness and height, meaning the flattened part is narrower and thicker than the pre-forged part. In this embodiment, the specific design principle of the flattening die is as follows: Figure 14 As shown, in terms of height, the flattened part is 2 to 5 mm larger than the pre-forged part, and in terms of width, the flattened part is 1 to 2 mm smaller than the pre-forged part. Moreover, the cross-sectional area of each position of the flattened part is larger than the corresponding cross-sectional area of the pre-forged part, and the fillet design of each position of the flattened part is one size larger than the corresponding fillet design of the pre-forged part.
[0035] For example, such as Figure 14 As shown, if the width of the large end of the pre-forged part is set as G and the height is set as N, then the width of the large end of the flattened part is the difference between G and 1~2, and the height is the sum of N and 2~5; if the width of the rod part of the pre-forged part is set as G and the height is set as N, then the width of the rod part of the flattened part is the difference between G and 1~2, and the height is the sum of N and 2~5; if the width of the small end of the pre-forged part is set as G and the height is set as N, then the width of the small end of the flattened part is the difference between G and 1~2, and the height is the sum of N and 2~5.
[0036] In the pre-forging and final forging process of step S30, after obtaining the flattened part through the forming and flattening process, a forging press and corresponding forging die can be used to first pre-forge the flattened part to obtain a pre-forged part, and then the pre-forged part can be final-forged to obtain a final forged part. At this time, the final forged part has flash, and then a trimming process can be performed on the final forged part to remove the flash.
[0037] In the process of forging small flash of commercial vehicle connecting rods provided in the embodiments of the present invention, since the flash width formed by the forging blank corresponding to the connection between the rod body and the big end and the connection between the rod body and the small end is usually large, by adopting five-pass roll forging, the cross-sectional shape of the round bar material is changed from circle to ellipse, circle, ellipse, circle and circle in sequence, and its cross-sectional area gradually decreases, so that the diameter of the area of the forging blank corresponding to the rod body of the connecting rod is narrower, and the angle of the forging blank corresponding to the connection between the rod body and the big end and the connection between the rod body and the small end is steeper, so that less material is used at the connection between the big end and the rod body, the rod body and the connection between the small end and the rod body of the connecting rod, significantly reducing the flash width discharged in the final forging process at these positions.
[0038] Furthermore, the flattening process follows the principle of "slender and tall," designing the height of the flattened part to be 2-5mm larger than that of the pre-forged part, the width of the flattened part to be 1-2mm smaller than that of the pre-forged part, the cross-sectional area of each position of the flattened part to be larger than the corresponding cross-sectional area of the pre-forged part, and the fillet radius of each position of the flattened part to be one size larger than the corresponding fillet radius of the pre-forged part. This makes the flattened part narrower and thicker than the pre-forged part, closer to the shape of the finished part, resulting in more precise material distribution, reduced wear on the pre-forging die, reduced flash width, and extended die life. Simultaneously, the pre-forging process pre-fills areas that are difficult to fill, preventing creases and ensuring high-quality connecting rods. Therefore, while ensuring the forging is fully filled, it reduces flash volume, saves material, and effectively overcomes the problems of low material utilization and short die life in traditional forging processes.
[0039] In some embodiments, such as Figure 1 and Figure 2 As shown, step S30, which involves pre-forging and final forging the flattened part to obtain the pre-forged part and the final forged part sequentially, specifically includes the following steps: Step S31: Forge the flattened part using a pre-forging die with a single-compartment design to obtain a pre-forged part.
[0040] Step S32: Forging the pre-forged part using a single-compartment final forging die to obtain a final forging of the connecting rod with small flash, wherein the height of the pre-forged part is 1-1.2 mm larger than the height of the final forging, and the width of the pre-forged part is 0.5-1.2 mm smaller than the width of the final forging.
[0041] It is understandable that step S31, which is the step of forging the flattened part using a single-compartment pre-forging die to obtain a pre-forged part, specifically includes the following steps: the flattened part is forged by cooperating with the lower pre-forging die and the upper pre-forging die with the compartment to obtain the pre-forged part. Step S32, which is the step of forging the pre-forged part using a single-compartment final forging die to obtain a final forging of the connecting rod with a small flash, specifically includes the following steps: the pre-forged part is forged by cooperating with the lower final forging die and the upper final forging die with the compartment to obtain the final forging.
[0042] like Figure 15 As shown, this embodiment eliminates the lower die compartment from the original process, replacing it with a single-compartment forging die. The compartment on the forging die allows the flash to be discharged more smoothly during forging. With the single-compartment design, the horizontal discharge length of the flash increases by 3-5mm, while the vertical thickness decreases by 2mm. Overall, the amount of flash discharged is reduced.
[0043] Furthermore, compared to the original process, the cavity of the pre-forging die in this embodiment is closer to the shape of the final forging. In this embodiment, as... Figure 16 As shown, compared to the final forging, the pre-forging has an overall thickness increase of 1 to 1.2 mm and a width decrease of 0.5 to 1.2 mm. The volume change ratio between the pre-forging and the final forging is reduced from 6%-7% to 3%-5%. This not only reduces the width of flash discharge and the amount of material used, but also reduces wear on the final forging die and improves the life of the final forging die.
[0044] For example, such as Figure 16 As shown, if the width of the large end of the final forging is set as G and the height as N, then the width of the large end of the pre-forging is G plus the difference between 0.5 and 1.2, and the height is N plus the sum of 1 and 1.2. If the width of the rod of the final forging is set as G and the height as N, then the width of the rod of the pre-forging is G plus the difference between 0.5 and the height is N plus the sum of 1 and 1.2. If the width of the small end of the final forging is set as G and the height as N, then the width of the small end of the pre-forging is G plus the difference between 0.5 and 1.2, and the height is N plus the sum of 1 and 1.2.
[0045] In some embodiments, such as Figure 3As shown, before the billet rolling forging process in step S10, the small flash forging process of the commercial vehicle connecting rod also includes: Step S1: Forging design process: The thickness of the connecting rod's big end, small end and wedge plane is increased from 3mm to 2mm, the size of the connecting rod's big end inner hole and small end inner hole is increased from 6mm to 5mm, the size of the connecting rod's punching hole is increased from 12mm to 10mm, the thickness of the connecting rod's body is increased by 0.5mm, and the thickness of the connecting rod's web is increased by 0.3mm.
[0046] Understandably, the basic principle of forging design is to minimize the amount of material required while ensuring the quality of the connecting rod product. The design must ensure that the machined surfaces of the connecting rod have appropriate machining allowances, allowing the cutting tool to cut normally and remove surface defects without excessive tool wear. Furthermore, some compensation should be made in some important non-machined areas to ensure sufficient strength in these areas; for example, the rod body should be thicker than the theoretical model.
[0047] Compared to traditional techniques, such as Figure 5 As shown, this embodiment makes the following improvements: the thickness of the connecting rod's big end, small end, and wedge-shaped plane is increased from 3mm to 2mm; the dimensions of the connecting rod's big end inner hole and small end inner hole are increased from 6mm to 5mm; the connecting rod's punching size is increased from 12mm to 10mm; the connecting rod's body thickness is increased by 0.5mm; and the connecting rod's web thickness is increased by 0.3mm. Overall, this embodiment reduces material usage by approximately 3% compared to traditional processes while ensuring sufficient machining allowance, thus saving raw material costs. The wedge-shaped plane of the connecting rod refers to a wedge-shaped forging structure at the end of the small end (the end connected to the piston pin), which is thicker at one end and thinner at the other.
[0048] Furthermore, such as Figure 3 As shown, before the billet rolling forging process in step S10, the small flash forging process of commercial vehicle connecting rods also includes: Step S2: Determining the diameter of the round bar: The flash width at the maximum cross-section of the final forging is set from 20-35mm to 10-20mm, and the flash thickness at the maximum cross-section of the final forging is set from 5-6mm to 4mm.
[0049] Understandably, the principle for selecting the diameter of round bar stock is to minimize the flash width while ensuring the maximum cross-section of the forging is filled, thereby reducing the diameter of the selected round bar stock. For example... Figure 6 As shown, in this embodiment, the flash width at the largest cross-section, i.e., section AA, is designed to be 10-20mm, which is 10-15mm narrower than the normal flash width. The flash thickness is also changed from the original 5-6mm to 4mm, thus determining the diameter of the round bar. Production verification has shown that this flash design parameter can ensure the forging is fully filled.
[0050] The core principle for determining the diameter of round bar stock is to select a billet of appropriate specifications based on the volume and shape of the forging, ensuring that it fills the die cavity without generating excessive flash waste, while simultaneously meeting the requirements of forging ratio and forging processability. According to the existing design process, first analyze the forging drawing, calculate the volume of the forging, then estimate the flash volume and burn-off volume, calculate the volume of the billet, and finally determine a reasonable length-to-diameter ratio based on the main forming processes (upsetting or drawing), and calculate and round the diameter and length of the round bar stock.
[0051] Furthermore, such as Figure 4 As shown, the forging process for small flash of connecting rods in commercial vehicles also includes: Step S3: Push rod arrangement process: If the diameter of the inner hole of the small end of the connecting rod is smaller than the set value, a push rod is arranged on each side of the connecting rod's large end skin and the connecting rod body in the final forging lower die, so that the push rod can eject the final forging. The push rods corresponding to the two sides of the connecting rod body are placed on the flash bridge of the final forging lower die; If the diameter of the inner hole of the small end of the connecting rod is greater than or equal to the set value, a push rod is arranged on each side of the connecting rod's large end skin and the connecting rod's small end skin in the final forging lower die, so that the push rod can eject the final forging.
[0052] Understandably, the arrangement of ejector pins should ensure that the forging can be ejected normally under conditions of small flash. Based on the diameter of the small end bore of the connecting rod, this embodiment employs two different ejector pin arrangement methods, such as... Figure 17 and Figure 18 As shown. If the inner diameter of the small end's inner hole is smaller than a certain value, making it impossible to arrange ejector pins, then a three-ejector pin structure is adopted on the final forging lower die. Specifically, ejector pins are arranged on the large end connecting skin and both sides of the rod body of the corresponding connecting rod in the final forging lower die, with the ejector pin corresponding to the rod body placed on the flash bridge. Compared to the traditional design of placing ejector pins in the chamber, this embodiment can normally eject small flash forgings. Production verification shows that when the flash covers two-thirds of the top area of the ejector pin, the forging can be ejected normally. At the same time, because the cavity at the corresponding rod body of the final forging die is shallow, it has strong impact resistance, and there is no need to worry about the final forging die cracking easily.
[0053] If the inner diameter of the small end bore is greater than or equal to a certain value, allowing for the placement of ejector pins, then a double ejector pin structure is adopted on the final forging die. Specifically, one ejector pin is placed at each of the large and small end connecting plates of the corresponding connecting rod in the final forging die. Preferably, the ejector pins are tapered ejector pins. Specifically, the upper end of the ejector pin corresponding to the large and small end connecting plates of the connecting rod has a frustum-shaped structure with a larger upper end and a smaller lower end. The structure of the tapered ejector pin is as follows: Figure 18 As shown, the tapered ejector pin has a large contact area at its tip, resulting in more even force distribution on the forging compared to ordinary ejector pins. This ensures smooth ejection of the forging and guarantees parallel demolding.
[0054] In some embodiments, a walking beam is used to transfer and place the workpieces along the billet rolling forging process, the forming and flattening process, and the pre-forging and final forging process.
[0055] It is understood that this embodiment employs an automated transfer method for the workpieces, using a walking beam to automatically and continuously transport and place the workpieces, achieving precise and efficient transfer of the workpieces between different workstations. This makes the positioning of the workpieces in each process more accurate, thereby enabling precise small flash forming. The small flash forging process for commercial vehicle connecting rods provided in this embodiment can be applied to an automated hot forging line for walking beams.
[0056] After the process improvement in this embodiment, the material utilization rate of the current connecting rod product is increased by 8%, and the mold life is increased by 30%. Specifically, compared with the original process, the diameter of the round bar can be reduced by 3%, making the flash at the big end of the connecting rod narrower, resulting in a 10-15mm reduction in flash length and a 1-2mm reduction in thickness. This increases the material utilization rate from 70% to 78%, significantly reduces raw material costs, and reduces the impact force by 20%, extending the mold life.
[0057] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0058] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims
1. A forging process for small flash on connecting rods of commercial vehicles, characterized in that, include: The billet forging process involves five passes of rolling in a forging die to deform and extend the round bar along its axial direction. This causes the cross-sectional shape of the round bar, corresponding to the connecting rod body, the connection between the connecting rod body and the large end, and the connection between the connecting rod body and the small end, to change sequentially from elliptical to circular to elliptical to circular to obtain the forging billet. Forming and flattening process: The forging blank is flattened using a flattening mold to obtain a flattened part, wherein the height of the flattened part is 2-5mm larger than the height of the pre-forging part, the width of the flattened part is 1-2mm smaller than the width of the pre-forging part, the cross-sectional area of each position of the flattened part is larger than the corresponding cross-sectional area of the pre-forging part, and the fillet radius of each position of the flattened part is one size larger than the corresponding fillet radius of the pre-forging part; Pre-forging and final forging processes: The flattened part is subjected to pre-forging and final forging processes to obtain pre-forged part and final forged part in sequence.
2. The commercial vehicle connecting rod small flash forging process according to claim 1, characterized in that, The process of pre-forging and final forging the flattened part to obtain a pre-forged part and a final forged part successively includes the following steps: The flattened part is forged using a pre-forging die with a single-compartment design to obtain a pre-forged part; The pre-forged part is forged using a single-compartment final forging die to obtain a final forging of a connecting rod with a small flash. The height of the pre-forged part is 1-1.2 mm larger than the height of the final forging, and the width of the pre-forged part is 0.5-1.2 mm smaller than the width of the final forging.
3. The commercial vehicle connecting rod small flash forging process according to claim 2, characterized in that, The volume change ratio between the pre-forging and the final forging is reduced from 6%-7% to 3%-5%.
4. The commercial vehicle connecting rod small flash forging process according to claim 3, characterized in that, The process of forging the flattened part using a single-compartment pre-forging die to obtain a pre-forging part includes the following steps: The flattened part is forged by using a pre-forging lower die and a pre-forging upper die with a storage compartment to obtain a pre-forged part.
5. The forging process for small flash of commercial vehicle connecting rods according to claim 3, characterized in that, The process of forging the pre-forged part using a single-compartment final forging die to obtain the final forging of the connecting rod with small flash includes the following steps: The pre-forged part is forged by using the lower final forging die and the upper final forging die with the housing part to obtain the final forging part.
6. The forging process for small flash of commercial vehicle connecting rods according to claim 1, characterized in that, The process includes the following steps prior to the billet rolling forging process: Forging design process: Increase the thickness of the connecting rod's big end, small end, and wedge-shaped plane from 3mm to 2mm; increase the inner diameter of the connecting rod's big end and small end from 6mm to 5mm; increase the punching diameter of the connecting rod from 12mm to 10mm; increase the thickness of the connecting rod's body by 0.5mm; and increase the thickness of the connecting rod's web by 0.3mm.
7. The forging process for small flash of commercial vehicle connecting rods according to claim 1, characterized in that, The process includes the following steps prior to the billet rolling forging process: The process for determining the diameter of round bar stock is as follows: the flash width at the maximum cross-section of the final forging is set from 20-35mm to 10-20mm, and the flash thickness at the maximum cross-section of the final forging is set from 5-6mm to 4mm.
8. The forging process for small flash of commercial vehicle connecting rods according to claim 1, characterized in that, Also includes: Ejector rod arrangement process: If the diameter of the small end inner hole of the connecting rod is smaller than the set value, an ejector rod is arranged on each side of the connecting rod's large end connecting skin and the connecting rod body in the final forging lower die, so that the ejector rod can eject the final forging. Among them, the ejector rods corresponding to the two sides of the connecting rod body are placed on the flash bridge of the final forging lower die; If the diameter of the small end inner hole of the connecting rod is greater than or equal to the set value, an ejector rod is arranged on each side of the connecting rod's large end connecting skin and the small end connecting skin in the final forging lower die, so that the ejector rod can eject the final forging.
9. The forging process for small flash of commercial vehicle connecting rods according to claim 8, characterized in that, The top rod, corresponding to the large end and small end of the connecting rod, adopts a frustum-shaped structure with a larger top end and a smaller bottom end.
10. The forging process for small flash of commercial vehicle connecting rods according to claim 1, characterized in that, Along the billet rolling forging process, the forming and flattening process, and the pre-forging and final forging process, a walking beam is used to transfer and place the workpieces.