A straight gear hot precision forging forming die, system and method

Abstract

This invention discloses a hot precision forging mold, system, and method for spur gears in the field of spur gear manufacturing technology. The hot precision forging mold for spur gears includes an upper cover plate, a punch, a die, a base plate, and a push rod. The die has a spur gear cavity. The lower end face of the upper cover plate can mate with the upper end face of the die. The upper end face of the base plate is fixed to the lower end face of the die. The upper cover plate has a first through hole. The punch is slidably connected to the first through hole, and its lower end shape is adapted to the inner ring shape of the workpiece to be processed. The base plate has a second through hole coaxial with the spur gear cavity. The upper end of the push rod is slidably connected to the second through hole. The hot precision forging mold for spur gears provided by this invention is integrated and has high production efficiency; the hot precision forging system for spur gears is simple to operate and highly efficient; the hot precision forging method for spur gears using this mold is simple and convenient, and the gear forming quality is high.

Description

Technical Field

[0001] This invention relates to a hot precision forging mold, system, and method for spur gears, belonging to the field of spur gear manufacturing technology. Background Technology

[0002] Spur gears are characterized by high load capacity and large transmission ratio, and are widely used as planetary gears and sun gears in drive axles. Spur gears used in engineering machinery drive axles have large modules, making direct forging difficult; currently, the industry mainly uses machining. Precision forging is a new process that has emerged in recent years. Compared to traditional machining, precision-forged spur gears have advantages such as high material utilization, high production efficiency, simple processes, and low production costs, and also exhibit good bending strength and fatigue resistance at the tooth root.

[0003] Dies are an indispensable tool in the precision forging process of spur gears. A good die structure design can make the forging process more efficient, the die life longer, and the product quality better.

[0004] However, most existing forging molds are multi-stage molds, such as pre-forging molds, final forging molds, or sectional forging molds. During the tooling transfer process, the billet experiences problems such as a drop in surface temperature, increased surface oxidation, and low production efficiency. The complex processing steps reduce the fluidity of the billet metal, make it difficult to fill the upper and lower corner teeth, require higher forming loads, and lead to the selection of larger tonnage presses, which seriously affects the service life of the final forging mold and indirectly increases production costs. Summary of the Invention

[0005] The purpose of this invention is to provide a hot precision forging mold, system and method for spur gears, which can realize the integrated hot precision forging of spur gears, improve the efficiency of the forging process and achieve high forming quality.

[0006] To solve the above-mentioned technical problems, the present invention is implemented using the following technical solution: On one hand, the present invention provides a hot precision forging die for spur gears, including an upper cover plate, a punch, a die, a bottom plate, and an ejector pin; The die cavity is provided with a spur gear cavity; the upper cover plate is located above the die cavity, and the lower end face of the upper cover plate can be in contact with the upper end face of the die cavity; the upper end face of the bottom plate is fixed to the lower end face of the die cavity. The upper cover plate is provided with a first through hole; the punch is slidably connected to the first through hole, and its lower end shape is adapted to the inner ring shape of the workpiece to be processed; The base plate has a second through hole coaxial with the spur gear cavity; the upper end of the push rod is slidably connected to the second through hole, and the axial projection of the outer contour of the upper end of the push rod is located inside the axial projection of the tooth root circle of the spur gear cavity.

[0007] The hot precision forging die for spur gears of this invention is designed as an integrated forming method, where one die can simultaneously perform upsetting, punching, and gear profile filling. This integrated forming die not only reduces heat loss during forging and refines the gear structure, but also ensures the fluidity of the billet metal, reduces die stress, and consequently extends the service life.

[0008] Optionally, the top center of the ejector pin is provided with a locating pin for tight engagement with the bottom of the workpiece. The design of the locating pin on the ejector pin can effectively ensure the uniformity of tooth filling in the blank during the forging process, and also facilitate the demolding operation of the forged gear in the later stage.

[0009] Optionally, the positioning pin is a conical protrusion integrally formed with the top rod. The conical protrusion design allows for more precise positioning of the blank before upsetting, ensuring coaxiality accuracy during inner hole forming.

[0010] Optionally, the spur gear cavity periphery has an internal tooth cavity corresponding to the module, number of teeth, and pitch circle of the spur gear to be machined, and the internal gear has machining allowances on each side of the tooth width direction and on the gear profile. The machining allowance with a certain clearance ensures further precision machining in the later stages.

[0011] Optionally, the bottom sides of the upper cover plate are provided with pressure-reducing grooves facing the tip circle of the internal tooth cavity. In the final stage of tooth filling, the design of the pressure-reducing grooves not only reduces the effective stress of metal flow, making it easier to completely fill the upper corners, but also effectively reduces the mold stress of the die and extends the service life of the die.

[0012] Optionally, the base plate and the die are detachably fixed. This detachable fixed connection allows for easy replacement of the die according to the gear specifications.

[0013] Optionally, the contact surface between the base plate and the ejector pin is provided with a 1° draft angle. The draft angle design facilitates the ejector pin to more easily push the machined workpiece upward after the gear precision forging is completed.

[0014] Optionally, the punch and the first through hole, and the upper end of the ejector pin and the second through hole, are respectively fitted with transition fits. These transition fits make the punch and ejector pin easier to disassemble and install.

[0015] Optionally, the punch, die, base plate, and ejector pin are all made of materials with a surface hardness of 62 HRC or higher. Because the forming die operates under high temperature and high pressure conditions for extended periods, hot precision forging dies made of quenched die steel have greater strength, hardness, and thermal stability, as well as higher thermal fatigue resistance, toughness, and wear resistance.

[0016] Optionally, during the spur gear forming process, the upper cover plate, punch, die, base plate, and ejector pin are coaxial. The coaxiality of the mold components during forming maximizes the machining accuracy of the workpiece, thereby achieving a high-quality yield.

[0017] Secondly, the present invention also provides a system for hot precision forging of the spur gear, including a box furnace, a press, a mold temperature controller, a robot, a demolding drive structure, and a hot precision forging mold for the spur gear; Specifically, the box furnace can be used to heat the billet, and the robotic arm can be used to transfer the heated billet into the spur gear cavity of the spur gear hot precision forging die; The press has driving mechanisms for driving the upper cover plate and the punch to move in the vertical direction, respectively. The mold temperature controller can be used to control the temperature of the spur gear forming mold. The demolding drive mechanism can be used to drive the ejector rod to move in the vertical direction so as to eject the workpiece from the spur gear cavity.

[0018] The hot precision forging system for spur gears provided by this invention uses a box furnace to heat the billet to the required temperature, a robotic arm to quickly transfer the billet into the processing cavity, a press to provide the power source for the processing of the formed gears, and a mold temperature controller to maintain the constant temperature of the mold during processing, which prevents the billet from experiencing a rapid drop in deformation temperature and various defects such as poor metal fluidity. The demolding drive mechanism not only enables rapid demolding but also makes the entire production process quick and simple, and significantly improves production efficiency.

[0019] Thirdly, the present invention also provides a method for hot precision forging of spur gears using the aforementioned hot precision forging die, comprising the following steps: S1: Heat and keep the mold warm; A positioning hole is machined on one end face of the blank, and then heated to the set temperature and held at that temperature. S2: Transfer the heated and heat-preserved blank into the spur gear cavity, so that the positioning hole and the positioning pin on the push rod are tightly engaged; S3: The upper cover plate and the punch are driven by the press to simultaneously press the blank downward along the axial direction of the spur gear cavity until the lower end face of the upper cover plate contacts the upper end face of the die to complete the upsetting. Then the upper cover plate is controlled to stop moving. The punch is controlled to continue pressing the blank downwards until it reaches the preset depth in the spur gear cavity, so that the blank fills the internal gear cavity and completes the punching. S4: Remove the upper cover plate and the punch, and control the ejector rod to push the workpiece in the spur gear cavity upward through the demolding drive mechanism to complete the demolding.

[0020] The hot precision forging method for spur gears provided by this invention involves the upper cover plate and punch in the integrated forming mold moving collaboratively during the upsetting process; during the punching process, the punch continues to move axially to punch holes, while the upper cover plate constrains the reverse flow of the blank metal, forming a closed reverse extrusion forming of the gear blank, which creates metal flow lines perpendicular to the force direction at the tooth root, further improving its mechanical properties.

[0021] Meanwhile, the heat preservation control of the billet and the mold not only avoids the problem of poor metal fluidity of the processed parts caused by the rapid drop in temperature when changing the mold, but also solves a series of disadvantages such as the mold being subjected to greater deformation load due to the rapid drop in billet temperature, which leads to a shortened mold life and poor economic efficiency.

[0022] Optionally, before step S1, a release agent is sprayed onto the sidewall of the spur gear cavity of the die. The choice of release agent is more conducive to successful demolding.

[0023] Optionally, in step S1, the mold is heated to 300°C and then kept at that temperature. The billet is heated to 1000°C in a box furnace and then kept at that temperature for 1 hour. During the billet heating process, the heating rate is set to 30°C / min.

[0024] Optionally, in step S3, a 1000-ton closed-loop precision forging press is used to drive and control the upper cover plate and the punch. The safety factor is set to 0.8. During the upsetting process, the movement speed of the upper cover plate is controlled at 20 mm / s. During the entire process from upsetting to completing the punching, the movement speed of the punch is controlled at 20 mm / s.

[0025] Based on actual production needs, the selection of specific parameters in steps S1 and S3 further improves the comprehensive performance of the forgings during the hot precision forging of spur gears, and maximizes the guarantee of quality and precision.

[0026] Furthermore, the method also includes air cooling the demolded workpiece, and after the workpiece temperature drops to room temperature, heat treatment and machining are performed to obtain the finished precision-forged gear. The hollow spur gear after forging can achieve the required surface roughness and dimensional accuracy through machining processes such as shaving or grinding.

[0027] The demolded workpiece has a punched skin, which helps protect the mold from damage; the heat treatment and thermomechanical processing are used at least for finishing the inner hole and the upper and lower end faces of the gear.

[0028] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: (1) The hot precision forging die for spur gears of the present invention is an integrated die, in which the upper cover plate and the punch work together to complete the upsetting process, and the punch alone completes the punching process. One die can complete the complex processes of upsetting and punching at the same time. The integrated design not only reduces die development and lowers costs, but also avoids the problems of low yield and short die life caused by heat loss during die replacement. (2) The system for hot precision forging of spur gears makes the entire production process quick and simple, and the production efficiency is significantly improved.

[0029] (3) The hot precision forging method using a spur gear hot precision forging die is simple to operate, which not only improves the tooth profile quality and fatigue strength at the tooth root, but also effectively reduces the die stress of the die and extends the service life of the die; and also effectively ensures the uniformity of tooth profile filling of the billet during the forging process. Attached Figure Description

[0030] Figure 1 This is a three-dimensional schematic diagram of a hot precision forging spur gear mold according to an embodiment of the present invention; Figure 2 for Figure 1 The diagram shows the axial cross-sectional structure of the hot precision forging spur gear mold. Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0032] Example 1 Combination Figure 1 and Figure 2 As shown, the present invention provides a hot precision forging die for spur gears, including a punch 1, an upper cover plate 2, a die 4, a bottom plate 5, and an ejector pin 6; The die cavity 4 is provided with a spur gear cavity; the upper cover plate 2 is located above the die cavity 4, and the lower end face of the upper cover plate 2 can be in contact with the upper end face of the die cavity 4; the upper end face of the bottom plate 5 is fixed to the lower end face of the die cavity 4. The upper cover plate 2 is provided with a first through hole; the punch 1 is slidably connected to the first through hole, and its lower end shape is adapted to the inner ring shape of the workpiece to be processed; The base plate 5 has a second through hole coaxial with the spur gear cavity; the upper end of the push rod 6 is slidably connected to the second through hole, and the axial projection of the outer contour of the upper end of the push rod 6 is located inside the axial projection of the tooth root circle of the spur gear cavity.

[0033] In this embodiment, due to the integrated molding of the forging die, pre-forging, upsetting, and punching operations of the blank can be realized without changing the die midway, making the operation simple. First, the bar blank is heated and held at a temperature in a box furnace to achieve uniform internal and external temperatures. Then it is transferred to the complete set of forming dies. This process should be as fast as possible to minimize the loss of external surface temperature. Under the action of the press, the upper cover plate 2 and the punch 1 move together during the upsetting process; during the punching process, the punch 1 continues to move axially to punch the hole, while the upper cover plate 2 restricts the reverse flow of the blank metal, forming a closed reverse extrusion molding of the gear blank. A metal flow line perpendicular to the direction of force is formed at the tooth root. After forging, the hollow spur gear can achieve the required surface roughness and dimensional accuracy after a machining process, such as shaving or grinding.

[0034] Example 2 Based on Example 1, this example also has the following design: The top center of the push rod 6 is provided with a positioning pin 7 for tightly fitting with the bottom of the workpiece to be processed. The positioning pin 7 is preferably located at the center of the top of the push rod 6, and the positioning pin 7 is a conical protrusion integrally formed with the push rod 6.

[0035] The spur gear cavity has an internal tooth cavity corresponding to the module, number of teeth, and pitch circle of the spur gear to be machined. The internal gear has machining allowances on each side of the tooth width and on the gear profile. Specifically, a 2mm machining allowance is left on one side of the tooth width and a 1mm machining allowance is left on the tooth profile. This certain clearance of machining allowance facilitates subsequent machining, thereby improving the dimensional accuracy and surface roughness of the hole.

[0036] The upper cover plate 2 has pressure-reducing grooves 3 on both sides of its bottom end, facing the tooth tip circle of the inner tooth cavity. In the later stage of tooth filling, the forming load rises rapidly, but always remains within the safety limit of the press. The pressure-reducing grooves at the lower end of the upper cover plate 2 not only reduce the effective stress of metal flow, making it easier to completely fill the upper corner, but also effectively reduce the mold stress of the die 4 and extend the service life of the die 4.

[0037] The base plate 5 and the die 4 are detachably fixed together. The detachable connection makes it easier to replace the die 4 according to the gear specifications. Specifically, bolts and nuts can be used to fix the base plate 5 and the die 4 together.

[0038] The contact surface between the base plate 5 and the ejector rod 6 is provided with a draft angle of 1°, which facilitates the ejector rod 6 to push the workpiece upward after precision forging.

[0039] The punch 1 and the first through hole, and the upper end of the ejector rod 6 and the second through hole, are respectively transition fits. The punch 1 passes through the first through hole of the upper cover plate 2 and is connected to the upper end of the die 4. The upper end of the ejector rod 6 passes through the second through hole of the base plate 5 and is fixed to the die 4. The transition fit connection method makes it easier to disassemble the components.

[0040] The punch 1, die 4, base plate 5, and ejector pin 6 are all cylindrical components made of hardened die steel with a surface hardness of 62 HRC or higher. Because the forming die operates under high temperature and high pressure conditions for extended periods, hot precision forging dies made of hardened die steel exhibit greater strength, hardness, and thermal stability, as well as higher thermal fatigue resistance, durability, and wear resistance.

[0041] During the spur gear forming process, the upper cover plate 2, punch 1, die 4, base plate 5 and ejector pin 6 are coaxially arranged, so that the machining accuracy of the workpiece can reach a high standard and the finished product can achieve high quality.

[0042] Example 3 This embodiment describes a system for hot precision forging of spur gears, which includes a box furnace, a press, a mold temperature controller, a robot, a demolding drive structure, and the hot precision forging mold for spur gears described in Embodiment 1 or 2.

[0043] It is worth noting that the box furnace is used to heat the billet; the robotic arm is used to transfer the heated billet into the spur gear cavity of the spur gear hot precision forging die; the press has drive mechanisms for driving the upper cover plate 2 and the punch 1 to move vertically; the mold temperature controller is used to control the temperature of the spur gear forming die; and the demolding drive mechanism is used to drive the ejector rod 6 to move vertically to eject the workpiece from the spur gear cavity.

[0044] In this embodiment of the spur gear hot precision forging system, the blank is heated and kept warm in a box furnace to achieve uniform internal and external temperatures. The mold temperature controller also controls the forming mold to maintain a constant temperature. Then, the blank is quickly transferred to the entire forming mold by a robot arm. This process should be as fast as possible to reduce the loss of external surface temperature. Then, under the action of the press, the heated blank is forged into a semi-finished hollow spur gear. After that, the demolding drive mechanism drives the ejector rod 6 to move in the vertical direction to eject the workpiece. Finally, after a machining process, such as shaving or grinding, a finished spur gear with the required surface roughness and dimensional accuracy can be obtained.

[0045] Example 4 This embodiment describes a hot precision forging method for spur gears using the hot precision forging die of Embodiment 1, specifically including the following steps: S1: Heat and keep the mold warm; machine a tapered positioning hole on one end face of the blank, then heat it to the set temperature and keep it warm.

[0046] First, a conical notch of 8mm × 8mm is machined on one end face of a 90mm × 120mm bar. Then, the billet is placed in a box furnace and heated to 1000℃. The heating rate of the furnace is set to 30℃ / min, and the temperature is held for 60 minutes to ensure the consistency of the core and surface temperature of the billet. At the same time, a mold temperature controller is used to maintain a constant temperature of 300℃ for all molds, and lubricant is applied to the mold surface to reduce friction between the billet and the mold.

[0047] Specifically, the box furnace is a muffle furnace, the heating element is a silicon carbide rod, the temperature is controllable (room temperature - 1500℃), the heating rate is controllable (3-50℃ / min), and the temperature control accuracy is ±1℃. During use, a protective gas is introduced, and the microstructure of the billet at the initial forging temperature is determined by adjusting the heating rate, heating temperature, and holding time of the furnace.

[0048] Before step S1, an oil circuit can be designed in advance inside the mold and a release agent can be sprayed on the side wall of the spur gear cavity of the concave mold. The selection of the release agent is more conducive to the completion of demolding.

[0049] S2: Transfer the heated and heat-preserved blank into the spur gear cavity, so that the positioning hole and the positioning pin 7 on the push rod 6 are tightly engaged.

[0050] With the help of a robotic arm, the blank is quickly transferred to the die 4, and the notched end face is tightly fitted with the positioning pin 7 on the ejector pin 6. The upper end face of the blank is in contact with the upper cover plate 2 and the punch 1, ensuring that the heated blank is located in the center of the die 4, thus ensuring the uniformity of the tooth profile forming and the coaxiality accuracy during the inner hole forming.

[0051] Specifically, a positioning pin 7 is provided at the center of the top of the push rod 6. The selection of the conical positioning pin effectively ensures the uniformity of tooth filling in the blank during the forging process, and also facilitates the demolding operation of the forged gear in the later stage.

[0052] S3: Drive the upper cover plate 2 and the punch 1 simultaneously to press the blank downward along the axial direction of the spur gear cavity until the lower end face of the upper cover plate 2 contacts the upper end face of the die 4 to complete the upsetting. Then control the upper cover plate 2 to stop moving. Control the punch 1 to continue pressing the blank downward until it reaches the preset depth in the spur gear cavity, so that the blank fills the internal gear cavity and completes the punching.

[0053] During the upsetting stage, ensure the forging end face is flat and perpendicular to the billet axis. By controlling the rotation of the base plate and ejector pin, drive the die and the billet inside to rotate, preferably uniformly, to straighten the bending in time. The press drives the upper cover plate 2 and the punch 1 to simultaneously press the billet downwards at a speed of 20 mm / s. The height of the billet gradually shortens and the radial direction increases. The outer surface begins to be constrained by the inner wall tooth profile of the die 4 until the upper cover plate 2 touches the upper surface of the die 4. The upper cover plate 2 stops moving, but the punch 1 continues to press the billet downwards at the same speed.

[0054] During the punching stage, punch 1, acting as the power die, continues to press the blank downwards. The material extruded from the inner hole flows towards the tooth profile and the upper end. Constrained by the counter-pressing action of the upper cover plate 2, it eventually flows towards the tooth profile, gradually filling the tooth shape. This forms a tooth filling sequence of first the middle, then the lower, and finally the upper, creating a directional metal forging flow line. In the later stage of tooth filling, the forming load rises rapidly but remains within the safety limits of the press. The pressure-reducing groove 3 at the lower end of the upper cover plate 2 provides a certain pressure reduction and buffering effect.

[0055] It is worth noting that in step S3, a 1000-ton closed-mode precision forging press is used to drive and control the upper cover plate and the punch 1. The safety factor is set to 0.8. During the upsetting process, the movement speed of the upper cover plate 2 is controlled to be 20 mm / s. During the entire process from upsetting to completing the punching, the movement speed of the punch 1 is controlled to be 20 mm / s.

[0056] Based on actual production needs, the selection of specific parameters in steps S1 and S3 further improves the comprehensive performance of the forgings during the hot precision forging of spur gears, and maximizes the guarantee of quality and precision.

[0057] S4: Remove the upper cover plate and the punch 1, and control the ejector rod 6 to push the workpiece in the spur gear cavity upward through the demolding drive mechanism to complete the demolding.

[0058] After step S4, the demolded workpiece is air-cooled. Once the workpiece temperature drops to room temperature, it undergoes heat treatment and machining to obtain the finished precision-forged gear. The forged hollow spur gear, after machining processes such as shaving or grinding, can achieve the required surface roughness and dimensional accuracy.

[0059] Specifically, the demolded workpiece has a perforated connecting skin, which can prevent the mold from being damaged or struck; at the same time, the heat treatment and thermomechanical processing are used at least for the precision machining of the inner hole and the upper and lower end faces of the gear.

[0060] In summary, the hot precision forging die, system, and method for spur gears of the present invention, by realizing the processes of upsetting, punching, and tooth profile filling, not only reduces heat loss during forging, lowers the initial forging temperature, and refines the microstructure of the gear to be processed, but also ensures the fluidity of the billet metal, appropriately reduces the die stress of the die 4, and improves the service life of the die.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A straight gear hot precision forging forming method, characterized by, The hot precision forging die for spur gears used includes an upper cover plate, a punch, a die, a base plate, and an ejector pin; The die cavity is provided with a spur gear cavity; the upper cover plate is located above the die cavity, and the lower end face of the upper cover plate can be in contact with the upper end face of the die cavity; the upper end face of the bottom plate is fixed to the lower end face of the die cavity. The upper cover plate is provided with a first through hole; the punch is slidably connected to the first through hole, and its lower end shape is adapted to the inner ring shape of the workpiece to be processed; The base plate has a second through hole coaxial with the spur gear cavity; the upper end of the push rod is slidably connected to the second through hole, and the axial projection of the outer contour of the upper end of the push rod is located inside the axial projection of the tooth root circle of the spur gear cavity; the top center of the push rod has a positioning pin for tightly fitting with the bottom of the workpiece to be processed; the bottom sides of the upper cover plate have pressure-reducing grooves facing the tooth tip circle of the inner tooth cavity of the spur gear cavity; The hot precision forging method for spur gears includes the following steps: S1: Heat and keep the mold warm; and machine a positioning hole on one end face of the blank, then heat it to the set temperature and keep it warm; S2: Transfer the heated and heat-preserved blank into the spur gear cavity, so that the positioning hole and the positioning pin on the push rod are tightly engaged; S3: The upper cover plate and the punch are driven by the press to simultaneously extrude the blank downward along the axial direction of the spur gear cavity until the lower end face of the upper cover plate contacts the upper end face of the die, completing the upsetting process. Then, the upper cover plate is controlled to stop moving. During the upsetting stage, before the outer surface of the blank is constrained by the tooth profile of the inner wall of the die, the bottom plate and the ejector rod are controlled to rotate, which drives the die and the blank inside to rotate, so as to straighten the bending in time. The punch is controlled to continue pressing the blank downwards until it reaches the preset depth in the spur gear cavity, so that the blank fills the internal gear cavity and completes the punching. S4: Remove the upper cover plate and the punch, and control the ejector rod to push the workpiece in the spur gear cavity upward through the demolding drive mechanism to complete the demolding.

2. The hot precision forging method for spur gears according to claim 1, characterized in that, The positioning pin is a conical protrusion integrally formed with the top rod.

3. The hot precision forging method for spur gears according to claim 1, characterized in that, The spur gear cavity periphery has an internal tooth cavity corresponding to the module, number of teeth and pitch circle of the spur gear to be machined, and the internal tooth cavity has machining allowance on each side in the tooth width direction and on the gear profile.

4. The hot precision forging method for spur gears according to claim 1, characterized in that, The base plate and the cavity mold are detachably fixed together; The contact surface between the base plate and the ejector pin is provided with a draft angle of 1°.

5. The hot precision forging method for spur gears according to claim 1, characterized in that, The punch and the first through hole, and the upper end of the ejector pin and the second through hole, are respectively transition fits.

6. The hot precision forging method for spur gears according to claim 1, characterized in that, The punch, die, base plate and ejector pin are all cylindrical bodies made of hardened die steel with a surface hardness of 62HRC or higher. During the spur gear forming process, the upper cover plate, punch, die, base plate and ejector pin are coaxial.

7. The hot precision forging method for spur gears according to claim 1, characterized in that, Before step S1, a release agent is sprayed onto the side wall of the spur gear cavity of the die. After demolding, the workpiece is air-cooled. When the workpiece temperature drops to room temperature, it is heat-treated and machined to obtain the finished precision forged gear. The demolded workpiece has a punched skin, and the heat treatment and thermomechanical processing are used at least for finishing the inner hole and the upper and lower end faces of the gear.

8. The hot precision forging method for spur gears according to claim 7, characterized in that, In step S1, the mold is heated to 300°C and then held at that temperature. The billet is heated to 1000°C in a box furnace and then held at that temperature for 1 hour. During the billet heating process, the heating rate is set to 30°C / min. In step S3, a 1000-ton closed-loop precision forging press is used to drive and control the upper cover plate and the punch. The safety factor is set to 0.

8. During the upsetting process, the movement speed of the upper cover plate is controlled at 20 mm / s. During the entire process from upsetting to completing the punching, the movement speed of the punch is controlled at 20 mm / s.

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