Upset-extrusion composite forming process for flange shaft parts

Abstract

The invention discloses an upsetting-extruding composite forming process for flange shaft parts. The upsetting-extruding composite forming process comprises the steps that S1, blanking is conducted, specifically, a round bar is sawn into a short blank meeting the requirement; s2, heating is conducted, specifically, the short blank is heated to 1100-1230 DEG C; s3, upsetting is conducted, specifically, an upset blank is forged through a multi-station hot die forging press; s4, pre-upsetting-extruding: upsetting-extruding the upsetting blank into a pre-upsetting-extruding forging blank through a pre-upsetting-extruding die; s5, upsetting-extruding forming: upsetting-extruding the pre-upsetting-extruding forging blank into a forged piece with a flash through an upsetting-extruding forming die; the upsetting-extruding forming step mold comprises an upsetting-extruding forming upper mold and an upsetting-extruding forming lower mold, and the upsetting-extruding forming lower mold comprises an upsetting-extruding forming lower mold inner core, an upsetting-extruding forming lower mold outer ring and an upsetting-extruding forming lower mold ejector rod; and S6, trimming is conducted, specifically, redundant flashes of the forged piece with the flashes after upset-extrusion forming are cut off through a trimming die. The problems that in cross wedge rolling forming, the rolling ratio is too large, part characteristics of a disc part cannot be formed, and in local upsetting forming, multiple times of material gathering are needed, and the material utilization rate is low can be solved.

Description

Technical Field

[0001] This invention belongs to the field of forging technology and relates to a composite forming process for upsetting and extrusion of flange shaft parts. Background Technology

[0002] Please see Figure 1 This image shows a forged engine shaft for a new energy vehicle. The forged shaft is a flange-like part composed of a rod with a diameter of d1 and a disc with a diameter of d2. The rod is thin and long, while the disc diameter d2 is much larger than the rod diameter d1. In manufacturing such flange shaft parts, a blank is typically prepared first using a free forging or roll forging machine. A suitable bar stock is selected, drawn to lengthen the rod, and then the disc is formed using upsetting. However, without blank-making equipment such as free forging or roll forging machines, existing processes for producing such flange shaft parts can only use wedge rolling or partial upsetting.

[0003] A Chinese patent with publication number CN110508743 discloses a forging process for long flange shafts. This process produces flange shaft forgings using a first-aggregation-second-aggregation-pre-forging-final-trimming method on a flat forging mill. However, for... Figure 1 For the flange shaft parts, the height-to-diameter ratio (length of forming part / diameter of blank) of the formed part is 26 or more, requiring at least four gathering processes, resulting in a long process route and low production efficiency. If the material diameter is increased, gathering can be eliminated, but the machining allowance of the rod part is large, and the material utilization rate is low. If the wedge cross rolling forming method is used for production, the step drop is large, the rolling ratio is too large, and some features of the disc part cannot be formed.

[0004] Therefore, it is essential to research a new forming process for automotive engine shaft forgings. Summary of the Invention

[0005] The purpose of this invention is to propose a composite upsetting and extrusion forming process for flange shaft parts, in order to solve the problems of excessive rolling ratio and inability to form certain features in wedge cross rolling, as well as the problems of needing multiple material gathering and low material utilization in local upsetting.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] A composite forming process for upsetting and extrusion of flange shaft parts includes the following steps: S1: Cutting: Cut the round bar into short billets that meet the requirements. The weight of the short billet is the weight of the forging to be formed plus the weight of the flash. S2: Heating: The short billet is heated to 1100℃~1230℃ using a medium-frequency induction heating furnace; S3: Upsetting: The heated short bar is placed on the lower upsetting platform and forged into an upsetting billet using a multi-station hot die forging press; the upsetting platform has a columnar structure and two continuous countersinks are opened on the lower upsetting platform, the upper countersink is used for positioning the short bar, and the lower countersink is used to extrude the short bar into a step that is positioned in the pre-upsetting die; after upsetting, the lower end of the short bar is extruded by the lower countersink of the lower upsetting platform to form a protrusion with a conical surface; S4: Pre-upsetting: The upset billet is upset into a pre-upsetting forging billet through a pre-upsetting die; specifically, it includes: before the pre-upsetting begins, the upset billet is placed in the center of the lower pre-upsetting die, and the conical protrusion on the lower part of the upset billet is positioned in the conical cavity of the lower pre-upsetting die; during the pre-upsetting process, under the impact force of the upper pre-upsetting die, the upper part of the upset billet is upset into a bowl-shaped structure, and the lower part of the upset billet is extruded into a frustoconical shape; after the pre-upsetting is completed, the pre-upsetting forging billet obtained is a bowl-shaped structure, and the outer edge of the pre-upsetting forging billet forms a flash; the lower part of the pre-upsetting forging billet is frustoconical, and the lower end forms a complete platform; S5: Upsetting: The pre-upsetting forging billet is upset into a forging with Z-shaped flash that meets the drawing requirements through an upsetting die; specifically, the upsetting die includes an upper upsetting die and a lower upsetting die, wherein: the upper upsetting die is fixed together with the upper die holder on the upper slide of the hot forging press and can move up and down with the upper slide; the lower upsetting die includes an inner core, an outer ring, and an ejector pin, which are fixed on the lower die holder of the hot forging press; the inner core of the lower upsetting die has a double-step structure that is larger at the top and smaller at the bottom; Before upsetting begins, the outer ring of the lower die is heated to 300℃~500℃ and placed in the furnace. After holding at this temperature for 1.5~2 hours, the outer ring of the lower die expands due to the heat. The inner core of the lower die is then inserted into the outer ring of the lower die. After natural cooling, the inner core of the lower die and the outer ring of the lower die become an integral structure. The pre-upset forging billet is then placed into the lower die and positioned by the conical surface at the upper end of the inner core of the lower die. S6: Trimming: After the forging is formed by upsetting, the excess flash is cut off by the trimming die to obtain a forging that meets the requirements of the drawing.

[0008] Furthermore, in S1, the ratio of the short billet length h to the billet diameter d is: 1.2≤h / d≤2.5; the short billet size is Φ80×73 / 6.83kg (+40g / -20g).

[0009] Furthermore, in S3, the upper recessed platform has a diameter d2 of Φ82 and a depth of 3mm; the lower recessed platform has a diameter d11 of Φ47.3 and a depth of 18mm.

[0010] Furthermore, in S4, the flash structure of the pre-upsetting die is set in an arc shape.

[0011] Furthermore, in S5, the inner core and outer ring of the lower die of upsetting are interference fit, that is, the upper outer diameter d41 of the inner core of the lower die of upsetting is greater than the upper inner diameter d42 of the outer ring of the lower die of upsetting, d41-d42=0.2~0.3mm.

[0012] Furthermore, in S5, the Z-shaped burr includes a bridge section and a storage section. The bridge section is an L-shaped structure composed of an inclined section and a horizontal section. The storage section is located at the upper end of the inclined section of the bridge section and together with the bridge section forms a Z-shaped structure. The storage section and the inclined section of the bridge section form a certain angle. The horizontal sections of the bridge are, in order of width b2 and b1 respectively, a front section and a rear section, with b2 < b1, facing the forging; the inclined section of the bridge has a width of b3, b3 ≤ b2; and the bin section has a width of b4, b4 > b1. The angle between the silo section and the inclined section of the bridge section is 92° to 95°, and the two sides of the inclined section of the bridge section are parallel to each other. The inclined section from the warehouse to the bridge, and the transition section from the inclined section of the bridge to the horizontal section, are arc-shaped.

[0013] Furthermore, the rear width b1 of the horizontal section of the bridge is set to 3~5mm; the front width b2 of the horizontal section of the bridge and the width b3 of the inclined section of the bridge are both set to 2~3mm; the distance h4 from the lower end of the bin to the front bottom of the horizontal section of the bridge is ≥10mm; and the width b4 of the bin is ≥5mm.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: The upsetting and extrusion composite forming process for flange shaft parts of this invention enables the production of flange shaft forgings on a forging press using an upsetting-pre-upsetting-upsetting-trimming process without the need for billet-making equipment such as free forging or roll forging mills. This overcomes many disadvantages of wedge cross rolling, such as large step drop, excessive rolling ratio, and inability to form certain features of the disc portion; as well as the need for multiple material accumulation in local upsetting, resulting in a long process route or the elimination of material accumulation when increasing the material diameter, but with large machining allowances and low material utilization in the rod portion. In addition, the overall structure of the Z-shaped flash used in this invention also serves as a mold guide, ensures that the forging is fully filled and has good final filling, and accommodates excess metal. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a forged shaft for a new energy vehicle engine. Figure 2 This is a schematic diagram of the main steps of the upsetting and extrusion composite molding process for flange shaft parts of the present invention, wherein (a) is upsetting; (b) is pre-upsetting and extrusion; (c) is upsetting and extrusion molding; and (d) is trimming. Figure 3This is a schematic diagram simulating the forging of an engine shaft, where (a) represents the start of upsetting; (b) represents the end of upsetting; (c) represents the start of pre-upsetting; (d) represents the end of pre-upsetting; (e) represents the start of upsetting; and (f) represents the end of upsetting. Figure 4 This is a schematic diagram of the structure of an upsetting die; Figure 5 It is a common structure for flash; Figure 6 This is a schematic diagram of the Z-shaped flash.

[0016] Figure 4 The meanings of the labels are as follows: 1. Upper die for upsetting; 2. Inner core of lower die for upsetting; 3. Outer ring of lower die for upsetting; 4. Ejector pin of lower die for upsetting.

[0017] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0018] The upsetting and extrusion composite molding process for flange shaft parts provided in this invention is as follows: Figure 2 As shown, the process of upsetting-pre-upsetting-upsetting-trimming is used on a hot forging press to produce products such as... Figure 1 The flange-shaped forging shown includes the following steps: S1: Cutting: Cut the round bar into short blanks that meet the requirements. The weight of the short bar is... Figure 1 The weight of the flange shaft forging shown is plus the weight of the flash; ensure that the ratio of the short billet length h to the billet diameter d is: 1.2≤h / d≤2.5. In this embodiment, the short billet size is Φ80×173 / 6.83kg (+40g / -20g)).

[0019] S2: Heating: The short billet is heated to 1100℃~1230℃ using a medium-frequency induction heating furnace (1200±10℃ is used in this embodiment); S3: Upsetting: The heated short bar stock is placed on the lower upsetting table, and an upsetting billet with a specific shape is forged using a multi-station hot die forging press (see...). Figure 2 (a) like Figure 3As shown in (a) and (b), the upper upsetting platform has a columnar structure, and two continuous countersunk platforms are formed on the lower upsetting platform. The lower upsetting platform serves the following functions: 1. To ensure good positioning of the short bar stock when placed on the lower upsetting platform, thereby ensuring good concentricity of the various local steps of the upset billet after upsetting and preventing skewing. 2. To ensure accurate positioning of the upset billet in the subsequent pre-upsetting die, the lower end of the upset billet needs to be extruded to form a step that matches the opening of the pre-upsetting die. Therefore, two countersunk platforms are provided on the lower upsetting platform. The upper countersunk platform is used for positioning the short bar stock, and the lower countersunk platform is used to extrude the short bar stock to form the step positioned in the pre-upsetting die. After upsetting, while the diameter of the short bar stock is increased, its lower end is compressed by the lower countersunk platform of the lower upsetting platform to form a convex protrusion. In this embodiment, the upper recessed platform has a diameter d2 of Φ82 and a depth of 3mm; the lower recessed platform has a diameter d11 of Φ47.3 and a depth of 18mm.

[0020] S4: Pre-upsetting: Please refer to Figure 3 (c) and (d) involve upsetting the rough billet into a pre-upsetting forging billet using a pre-upsetting die (see...). Figure 2 (b) (In this embodiment, the dimensions of the pre-upsetting forged billet are as follows) Figure 2 As shown in (b), d12=Φ36; d42=Φ44.6; h12=50.1; h22=115.6; h32=43.3).

[0021] Figure 2 (b) represents the pre-upsetting step. The diameter d12 of the rod portion of the pre-upsetting forged billet, along with its frustoconical shape, ensures good positioning when placed into the lower die of the upsetting forming process. Therefore, the diameter d12 = the diameter of the upsetting forming rod portion at the corresponding height - 0.2 mm. That is, d12 = d33 - 0.2 mm, where h33 = h32.

[0022] Before pre-upsetting begins, the upsetting billet is placed in the center of the pre-upsetting die. The conical protrusion on the lower part of the upsetting billet forms a good position in the conical cavity of the pre-upsetting die, preventing the billet from being skewed when placed into the pre-forging process, resulting in more material on one side and less material on the other, which would lead to a particularly large flash on one side and an incomplete filling on the other side in the final forging.

[0023] During the pre-upsetting process, under the impact force of the pre-upsetting die, the metal on the upper part of the upset billet is upset into... Figure 2 (b) shows a bowl-shaped structure, and at the same time, the metal at the bottom of the upsetting billet is extruded. Figure 2 (b) shows a frustoconical rod shape, which facilitates positioning and further extrusion molding during subsequent upsetting.

[0024] After pre-upsetting, the outer edge of the resulting pre-upsetting forging billet forms a flash of a certain thickness (approximately 2 mm), ensuring that metal flows towards the flash while the pre-upsetting die cavity is completely filled. The lower part of the pre-upsetting forging billet is frustoconical, with a complete platform at the lower end (lower end diameter d12), ensuring good filling of the rod end face during subsequent upsetting. Otherwise, due to the extrusion action during upsetting, a protruding arc would form at the diameter d13 of the forging rod, resulting in insufficient machining allowance. The resulting pre-upsetting forging billet has a bowl-shaped structure, ensuring that there is more metal on the inner side and less metal on the outer side, guaranteeing smooth extrusion of the rod in the final upsetting process and preventing excessive metal from flowing towards the flash.

[0025] The flash structure of the pre-upsetting die is set in an arc shape to avoid stress concentration at the flash, which could lead to premature die failure. At the same time, this type of flash structure can prevent the flash from being twisted during the final upsetting of the pre-upsetting forging billet, thus preventing the metal from continuing to flow to the flash during upsetting.

[0026] S5: Upsetting: Please refer to Figure 3 (e) and (f) involve upsetting the pre-upsetting billet into a forging with flash that meets the drawing requirements using an upsetting die (see...). Figure 2 (c)).

[0027] Preferred, such as Figure 4 As shown, the upsetting die for the forging process includes an upper upsetting die 1 and a lower upsetting die. The upper upsetting die 1 is fixed to the upper slide block of the hot forging press with bolts, and can move up and down with the upper slide block. The lower upsetting die includes an inner core 2, an outer ring 3, and an ejector pin 4, all of which are fixed to the lower die base of the hot forging press with bolts. In this structural design, the lower upsetting die is not designed as a single piece. This design effectively avoids stress concentration at the junction of the inner core 2 and the outer ring 3 during forging, preventing premature cracking and scrapping of the lower upsetting die at this point.

[0028] However, dividing the upsetting die into an inner core 2 and an outer ring 3 introduces new problems: during upsetting, excess metal easily flows into the gap between the inner core 2 and the outer ring 3, causing difficulties in the subsequent ejection process. To solve this problem, the inner core 2 and the outer ring 3 are designed as an interference fit, meaning the upper outer diameter d41 of the inner core 2 is greater than the upper inner diameter d42 of the outer ring 3, with d41-d42 = 0.2-0.3 mm. During installation, the outer ring 3 of the upsetting die is heated to 300℃~500℃ (i.e., the outer ring of the upsetting die is placed in a furnace at 500℃ and kept at that temperature for 1.5~2 hours). Due to thermal expansion and contraction, the outer ring of the upsetting die will expand, allowing the inner core of the upsetting die to be easily inserted into the outer ring. After natural cooling, the inner core 2 of the upsetting die and the outer ring 3 of the upsetting die will become an integral structure. Furthermore, the inner core 2 of the upsetting die is designed with a double-step structure, wider at the top and narrower at the bottom. This design ensures accurate positioning during installation and prevents the die from loosening due to repeated forming and ejection during forging.

[0029] Before upsetting begins, the pre-upsetting forging blank is placed into the lower upsetting die and positioned by the conical surface at the upper end of the core 2 of the lower upsetting die. During the upsetting process, the design of the flash structure needs to ensure that it can provide sufficient resistance for the extrusion of the forging rod, thereby ensuring that the forging fills the cavity.

[0030] Forgings with flash are Figure 1 The forging shown is enlarged by 1.5% based on the coefficient of thermal expansion and a Z-shaped flash structure is added. This Z-shaped flash structure can provide sufficient resistance for the extrusion of the forging rod, thereby ensuring that the forging fills the cavity.

[0031] Designed using upsetting composite molding process Figure 1 The flange shaft forging process simulation shown (see...) Figure 3 It was found that in order to ensure smooth extrusion and good filling of the rod, it is necessary to design the flash structure reasonably to ensure that there is sufficient resistance when the metal flows to the flash, so as not to cause the mold cavity to be insufficiently filled due to too much metal flowing to the flash.

[0032] Existing common flash structures such as Figure 5As shown, there are six structures, from Form I to Form VI. However, the existing common flash structures have the following problems: 1. The bridge width b of the flash shown in Forms I to IV is limited, which is insufficient to provide enough resistance for the metal flow to the flash when the forging rod is extruded, making it impossible to ensure that the forging fills the cavity, especially potentially causing the rod length to be insufficiently extruded; 2. The flash structure shown in Form V adds a damping groove of R=4 to 5 to the flash structure of Form III, which can increase the resistance to metal flow to a certain extent. However, simulations show that even with the flash structure shown in Form V, it is still impossible to ensure that the forging fills the cavity; 3. The flash structure shown in Form VI can increase the resistance to metal filling the cavity, but the flash volume is too small, which is insufficient to accommodate the excess metal flowing to the flash when producing the above-mentioned flange shaft forgings; 4. The flash structures shown in Forms I to VI do not consider the guidance of the upper and lower dies. In actual production, this can easily lead to misalignment of the upper and lower dies, resulting in a large forging misalignment.

[0033] Based on this, the present invention designs a Z-shaped flash, such as Figure 6 As shown, the structure includes a bridge section and a storage section. The bridge section is an L-shaped structure composed of an inclined section and a horizontal section. The storage section is located at the upper end of the inclined section of the bridge section and together with the bridge section forms a Z-shaped component. The storage section and the inclined section of the bridge section form a certain angle. The horizontal section of the bridge section, facing towards the forging, has widths of b2 and b1 respectively at the front and rear, where b2 < b1. The width of the inclined section of the bridge section is b3, and b3 ≤ b2. The width of the storage section is b4, and b4 > b2.

[0034] The width b1 of the rear section of the horizontal segment of the bridge is set according to the width of the conventional forged flash bridge, which can be set to 3-5mm.

[0035] The front width b2 of the horizontal section of the bridge is 2~3mm, which increases the resistance of the metal flow to the flash, and is equivalent to a damping groove.

[0036] The design of the inclined section width b3 of the bridge is crucial. It forms a certain angle A with the bulkhead, typically A = 92° to 95°, and the opposite sides of the inclined section of the bridge are parallel to each other. Its functions are: a. to further increase the resistance of metal flow to the flash, extending the length of the aforementioned damping groove; b. to provide guidance for the entire upper and lower dies, preventing misalignment of the upper and lower dies during the upsetting process. Therefore, the distance h4 from the lower end of the bulkhead to the front bottom of the horizontal section of the bridge needs to be sufficiently long to fulfill the guiding function; h4 ≥ 10mm.

[0037] The purpose of the storage compartment is to hold excess metal; therefore, the width b4 of the storage compartment needs to have sufficient volume, b4≥5mm.

[0038] Preferably, the inclined section from the hopper to the bridge, and the transition section from the inclined section of the bridge to the horizontal section, are arc-shaped. The arc design ensures that the metal flows smoothly and seamlessly through this section, and also reduces mold wear caused by the metal flow.

[0039] When producing flange shaft forgings with the aforementioned flash, as the upper die strikes downwards, excess metal flows from the rear of the horizontal section of the bridge (part b1), i.e., the flash inlet, into the flash as the metal flows to fill the cavity. As the upper die continues to move downwards, the metal first fills part b1 and continues to flow outwards, beginning to flow towards part b2. Since the thickness of part b2 is less than that of part b1, it is further thinned after passing through the rear of the horizontal section (part b2), effectively increasing the resistance to the outward flow of metal, thus facilitating the filling of the cavity. After the rear of the horizontal section (part b2) is filled, excess metal continues to flow outwards from part b2 into the inclined section of the bridge (part b3). In part b3, the metal is forced to flip and flow upwards, while being further thinned, which provides even greater resistance to the continued outward flow of metal. Meanwhile, the width h4 of the inclined section (b3 part) of the bridge is large enough that if there is misalignment between the upper and lower dies, the flash metal layer can buffer the direct impact between them. The resistance to metal flow will force the metal thickness of the b3 part to become more uniform, thereby correcting the misalignment between the upper and lower dies. Therefore, it can also play a guiding role, reducing forging errors caused by misalignment between the upper and lower dies during forging. In addition, the inclined section (b3 part) of the bridge should not be designed too narrow. If this part is too narrow (e.g., b3 < 1mm), the metal will cool rapidly after flowing into the b3 part and will not be able to continue flowing out, which will greatly increase the forging resistance and may cause the equipment to stall. The width b4 of the flash structure's compartment (b4 part) is ≥ 5mm, providing sufficient volume to accommodate excess metal.

[0040] The above-mentioned Z-shaped flash has the following advantages: 1. During the upsetting process, the metal flow follows the principle of minimum resistance. While filling the forging die cavity, some metal flows towards the flash. If the flash structure is not properly designed, too much metal flowing towards the flash will lead to insufficient filling of the die cavity and the generation of scrap. Therefore, it is necessary to add some structures (such as damping grooves) to the flash to increase the resistance of metal flow towards the flash. The overall structural design of the horizontal section (b1 part + b2 part) and inclined section (b3 part) of the bridge of the Z-shaped flash used in this invention can effectively increase the resistance of metal flow towards the flash, thereby ensuring smooth extrusion of the rod and good filling of the forging.

[0041] 2. The inclined section of the bridge (part b3) forms an angle A with the chamber section. In actual production, this ensures that the upper die can smoothly enter the lower die. After the metal fills the front part (part b2) of the horizontal section of the bridge, the Z-shaped flash structure design forces the metal to flip upwards, further increasing the resistance to the metal flow towards the flash. Furthermore, if there is misalignment between the upper and lower dies while the metal continues to fill the inclined section (part b3), the flash metal layer can buffer the direct impact between the dies. The resistance to metal flow forces the metal thickness in part b3 to become more uniform, thus correcting the misalignment between the upper and lower dies. Therefore, this part not only functions as a conventional flash bridge but also provides excellent guidance for the upper and lower dies, reducing forging errors caused by misalignment.

[0042] S6: Trimming: Please refer to... Figure 2 (d) After the forging is upset and has flash, the excess flash is cut off by the edge trimming die to obtain a forging that meets the requirements of the drawing.

Claims

1. A composite molding process for upsetting and extrusion of flange shaft parts, characterized in that, Includes the following steps: S1: Cutting: Cut the round bar into short billets that meet the requirements. The weight of the short billet is the weight of the forging to be formed plus the weight of the flash. S2: Heating: The short billet is heated to 1100℃~1230℃ using a medium-frequency induction heating furnace; S3: Upsetting: The heated short bar is placed on the lower upsetting platform and forged into an upsetting billet using a multi-station hot die forging press; the upsetting platform has a columnar structure and two continuous countersinks are opened on the lower upsetting platform, the upper countersink is used for positioning the short bar, and the lower countersink is used to extrude the short bar into a step that is positioned in the pre-upsetting die; after upsetting, the lower end of the short bar is extruded by the lower countersink of the lower upsetting platform to form a protrusion with a conical surface; S4: Pre-upsetting: The upset billet is upset into a pre-upsetting forging billet through a pre-upsetting die; specifically, it includes: before the pre-upsetting begins, the upset billet is placed in the center of the lower pre-upsetting die, and the conical protrusion on the lower part of the upset billet is positioned in the conical cavity of the lower pre-upsetting die; during the pre-upsetting process, under the impact force of the upper pre-upsetting die, the upper part of the upset billet is upset into a bowl-shaped structure, and the lower part of the upset billet is extruded into a frustoconical shape; after the pre-upsetting is completed, the pre-upsetting forging billet obtained is a bowl-shaped structure, and the outer edge of the pre-upsetting forging billet forms a flash; the lower part of the pre-upsetting forging billet is frustoconical, and the lower end forms a complete platform; S5: Upsetting: The pre-upsetting forging billet is upsetting into a forging with Z-shaped flash that meets the requirements of the drawing through an upsetting die; specifically, the upsetting die includes an upper upsetting die (1) and a lower upsetting die, wherein: the upper upsetting die (1) is fixed together with the upper die base on the upper slide of the hot forging press and can move up and down with the upper slide; the lower upsetting die includes an inner core (2), an outer ring (3), and an ejector rod (4), which are fixed on the lower die base of the hot forging press; the inner core (2) of the lower upsetting die is a double-step structure with a larger upper part and a smaller lower part; Before the upsetting process begins, the outer ring (3) of the lower die is heated to 300℃~500℃ and placed in the furnace. After holding it at that temperature for 1.5~2 hours, the outer ring of the lower die will expand due to the heat. The inner core of the lower die will be inserted into the outer ring of the lower die. After natural cooling, the inner core (2) of the lower die and the outer ring (3) of the lower die will become an integral structure. The pre-upsetting forged billet will be placed into the lower die and positioned by the conical surface at the top of the inner core (2) of the lower die. S6: Trimming: After the forging is formed by upsetting, the excess flash is cut off by the trimming die to obtain a forging that meets the requirements of the drawing.

2. The upsetting and extrusion composite molding process for flange shaft parts as described in claim 1, characterized in that, In S1, the ratio of the short billet length h to the billet diameter d is: 1.2≤h / d≤2.5; the short billet size is Φ80×73 / 6.83kg (+40g / -20g).

3. The upsetting and extrusion composite molding process for flange shaft parts as described in claim 1, characterized in that, In S3, the upper recessed platform has a diameter d2 of Φ82 and a depth of 3mm; the lower recessed platform has a diameter d11 of Φ47.3 and a depth of 18mm.

4. The upsetting and extrusion composite molding process for flange shaft parts as described in claim 1, characterized in that, In S4, the flash structure of the pre-upsetting die is set to an arc shape.

5. The upsetting and extrusion composite molding process for flange shaft parts as described in claim 1, characterized in that, In S5, the inner core (2) of the lower die for upsetting and the outer ring (3) of the lower die for upsetting are interference fits, that is, the upper outer diameter d41 of the inner core (2) of the lower die for upsetting is greater than the upper inner diameter d42 of the outer ring (3) of the lower die for upsetting, and d41-d42=0.2~0.3mm.

6. The upsetting and extrusion composite molding process for flange shaft parts as described in any one of claims 1 to 5, characterized in that, In S5, the Z-shaped burr includes a bridge section and a storage section. The bridge section is an L-shaped structure composed of an inclined section and a horizontal section. The storage section is located at the upper end of the inclined section of the bridge section and together with the bridge section forms a Z-shaped structure. The storage section and the inclined section of the bridge section form a certain angle. The horizontal sections of the bridge are, in order of width b2 and b1 respectively, a front section and a rear section, with b2 < b1, facing the forging; the inclined section of the bridge has a width of b3, b3 ≤ b2; and the bin section has a width of b4, b4 > b1. The angle between the silo section and the inclined section of the bridge section is 92° to 95°, and the two sides of the inclined section of the bridge section are parallel to each other. The inclined section from the warehouse to the bridge, and the transition section from the inclined section of the bridge to the horizontal section, are arc-shaped.

7. The upsetting and extrusion composite molding process for flange shaft parts as described in claim 6, characterized in that, The rear width b1 of the horizontal section of the bridge is set to 3~5mm; the front width b2 of the horizontal section of the bridge and the width b3 of the inclined section of the bridge are both set to 2~3mm; the distance h4 from the lower end of the bin to the bottom front end of the horizontal section of the bridge is ≥10mm; the width b4 of the bin is ≥5mm.

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