Speed reducer transmission gear shaft forge piece and forging process thereof

Abstract

The invention relates to a speed reducer transmission gear shaft forge piece and a forging process thereof, the gear shaft forge piece comprises a tooth part and a shaft part, the tooth part and the shaft part are integrally forged by alloy steel, and the forging process comprises the following steps of blank pretreatment, multidirectional composite forging forming, temperature control cooling and waste heat treatment, composite heat treatment and quality detection. Through the finish forging die and multidirectional composite forging, a metal flow line is attached to the stress direction, the torsional strength is improved, meanwhile, the utilization rate of raw materials is high, the machining efficiency of a gear shaft forge piece is effectively improved, a gear is formed through multidirectional pressure, and the abrasion resistance and pitting corrosion resistance of the gear tooth surface are remarkably superior to those of a traditional gear shaft.

Description

Technical Field

[0001] The present invention relates to the technical field of forging technology for reducer gear shafts, and particularly to a forging and its forging process for a reducer drive gear shaft. Background Art

[0002] The reducer drive gear shaft is an indispensable core component in a reducer. Its main function is to transmit power through the meshing of gears and achieve changes in rotational speed and torque. At the same time, it relies on accessories such as bearings and the housing to provide support and protection.

[0003] In the prior art, Chinese Patent CN202111561189.8 discloses a vertical forging process for high-quality shaft forgings. The steps include blanking; upsetting and drawing out; marking small steps at both ends; pre-drawing the small steps at both ends, retaining the deformation amount of the last heat treatment; standing the preformed blank forging, putting the small steps at both ends into the mold, putting the upper small step into the upper mold, and putting the lower small step into the lower mold; vertically upsetting the preformed blank forging to thicken the middle section until the diameter reaches the forming size of the forging; demolding; and redrawing the small steps at both ends to the forming size of the forging. The present invention saves raw materials, has a more uniform structure, can correct coaxiality, has small deformation amounts each time, can avoid the generation of cracks, and improves product quality.

[0004] Although the above patent can form the prefabricated blank through vertical forging, there is only axial pressure during forging, and subsequent gear cutting processing is required on the gear shaft. A large amount of waste will be generated during cutting processing, resulting in low utilization rate of raw materials. At the same time, its processing efficiency is low, and the strength of the processed gear is poor, the internal structure is loose, and the fatigue life is short.

[0005] Therefore, there is an urgent need for a forging and its forging process for a reducer drive gear shaft to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to solve the problems of low utilization rate of raw materials and low processing efficiency in the prior art, and to provide a forging and its forging process for a reducer drive gear shaft.

[0007] To achieve the above purpose, the present invention adopts the following technical solutions: A forging for a reducer drive gear shaft includes a tooth part and a shaft part. The tooth part and the shaft part are integrally forged from alloy steel. A strengthening boss with a thickness 1.2 - 1.5 times the tooth height is provided at the tooth root, and an inner concave positioning groove with a depth of 8 - 10% of the shaft diameter is provided at the end face of the shaft part.

[0008] A forging process for a reducer drive gear shaft forging includes the following steps: Step 1: Pretreatment of the blank; The blank is cut and then heated. Step 2: Multi-directional compound forging forming; Initial forging: Axial upsetting is carried out on a press; Final forging: Using a final forging die, after the upper and lower dies are closed, radial pressure and axial pressure are applied synchronously to make the metal flow along the tooth-shaped cavity for filling; The final forging die includes an upper die and a lower die. Shaft cavities are provided inside both the upper die and the lower die. An upper template is provided above the upper die. A punch penetrating the top of the upper die is provided at the bottom of the upper template. Pull rods penetrating the upper die are provided on both sides of the punch at the bottom of the upper template. An installation carrier plate is installed at the bottom of the upper die. Side templates are slidably installed on both sides of the installation carrier plate. Tooth dies are installed on one side of the side templates facing the installation carrier plate. After radial pressurization of the two tooth dies, a tooth-shaped cavity is formed between the two tooth dies. Guide rods are installed at both ends of the side templates. Ear plates slidably connected to the guide rods are symmetrically installed at both ends of the installation carrier plate. Pressing mechanisms are symmetrically installed at the bottom of both ends of the installation carrier plate. The pressing mechanism includes an installation frame fixedly connected to the installation carrier plate. The bottom end of the installation frame is rotationally connected to a pressing frame through a rotating shaft. The pressing frame is U-shaped. The end of the pressing frame is connected to a pressing plate through an elastic telescopic rod. The surface of the pressing plate facing the blank is arc-shaped. The bottom of the pressing frame is fixedly installed with a bottom plate extending towards the bottom of the pressing plate. A tail plate is installed at the bottom of the outer side of the installation frame. A spring is connected between the tail plate and the pressing frame; Step 3: Temperature-controlled cooling and after-treatment; Step 4: Composite heat treatment; Step 5: Quality inspection.

[0009] Preferably, in Step 2, the final forging temperature is 850 - 900 °C.

[0010] Preferably, in Step 3, the temperature-controlled cooling includes the first-stage air cooling and the second-stage fog cooling. The air cooling reduces the temperature to 800 °C, and the fog cooling reduces the temperature from 800 °C to 500 - 550 °C.

[0011] Preferably, in Step 3, the after-treatment is to utilize the heat of the forging to enter a normalizing furnace, keep it at 680 - 720 °C for 2 - 3 hours, and introduce a hydrogen-nitrogen mixed gas into the furnace.

[0012] Preferably, in Step 4, the composite heat treatment includes local carburizing quenching, cryogenic treatment, and tempering.

[0013] Preferably, in Step 5, the quality inspection is to monitor the temperature and deformation amount in real time through an infrared thermal imager and a laser displacement sensor during the forging process.

[0014] Preferably, in step 1, internal defects of the blank are detected by ultrasonic flaw detection, and after heating to 1150 - 1200 °C, it is kept warm for 2 - 3 hours.

[0015] Compared with the prior art, the present invention provides a forging of a reducer drive gear shaft and its forging process, having the following beneficial effects: Through the finish forging die and multi-directional compound forging, the present invention makes the metal streamline fit the stress direction, improves the torsional strength, and at the same time, the utilization rate of raw materials is high, effectively improving the processing efficiency of the gear shaft forging; By using the waste heat of the forging to enter the normalizing furnace, the present invention effectively improves the utilization efficiency of waste heat and reduces energy consumption during the forging of the gear shaft forging; By forming the gear through multi-directional pressure, the wear resistance and pitting resistance of the gear tooth surface are significantly better than those of the traditional gear shaft; By setting the holding mechanism, when the blank is placed on the lower die, the blank is held by two symmetrical holding mechanisms, keeping the blank upright and stable during die closing. At the same time, after the upper die descends a certain distance, the upper part of the blank enters the upper die, and the bottom plate contacts and presses against the top of the lower die, causing the holding plate and the holding frame to rotate and turn over, releasing the clamping of the blank. At the same time, the turning over does not affect the normal die closing forging, improving the stability of the blank during die closing and increasing the forming accuracy of the forging. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the process of the present invention.

[0017] Figure 2 It is a schematic diagram of the structure of the finish forging die of the present invention.

[0018] Figure 3 It is a sectional view of the finish forging die of the present invention.

[0019] Figure 4 For the present invention Figure 3 Enlarged view at A.

[0020] Figure 5 It is a schematic diagram of the structure of the holding mechanism of the present invention.

[0021] In the figure: 1. Blank body; 2. Shaft part; 3. Tooth part; 4. Upper die; 5. Lower die; 6. Shaft cavity; 7. Tooth profile cavity; 8. Holding mechanism; 801. Mounting frame; 802. Tail plate; 803. Spring; 804. Holding frame; 805. Bottom plate; 806. Elastic telescopic rod; 807. Holding plate; 808. Rotating shaft; 9. Side template; 10. Upper template; 11. Punch; 12. Pull rod; 13. Guide rod; 14. Lower template; 15. Tooth die; 16. Mounting carrier plate; 17. Ear plate; 18. Top plate; 19. Ejector rod. Detailed implementation manners

[0022] To better understand the technical solution of the present invention, the following will be described in detail with reference to relevant drawings. It should be understood that the following specific embodiments are not intended to limit the specific implementation modes of the technical solution of the present invention, but are only implementation modes that the technical solution of the present invention can adopt. It should be noted first that the descriptions of the positional relationships of various components herein, such as component A is located above component B, are based on the relative positions of the components in the drawings and are not intended to limit the actual positional relationships of the components. Embodiment 1

[0023] Refer to Figures 1-5 , Figure 1 , a process schematic diagram of the forging process of a forging of a speed reducer transmission gear shaft according to the present invention is drawn. As shown in the figure, a forging of a speed reducer transmission gear shaft includes a tooth part 3 and a shaft part 2, wherein the tooth part 3 and the shaft part 2 are integrally forged from alloy steel, a strengthening boss with a thickness 1.2 - 1.5 times the tooth height is provided at the tooth root, and an inner concave positioning groove with a depth of 8 - 10% of the shaft diameter is provided at the end face of the shaft part.

[0024] Refer to Figures 1-5 , the forging process of a forging of a speed reducer transmission gear shaft involved in this embodiment includes the following contents: S1: Blank pretreatment S11. Saw the alloy steel bar into blanks and detect internal defects by ultrasonic flaw detection; S12. Heat the blanks to 1150 - 1200 °C and hold for 2 - 3 hours to ensure the homogenization of austenite; S2: Multi-directional composite forging and forming Adopt a closed-die forging and radial extrusion composite process: S21. Initial forging: Axial upsetting is carried out on a 4000T press, and the reduction ratio is ≥ 3:1 to eliminate the original pores, form a preliminary shaft part contour, and eliminate casting defects.

[0025] S21. Final forging: Use the final forging die. After the upper and lower dies are closed, apply radial pressure (600 - 800 MPa) and axial pressure (300 - 400 MPa) synchronously to make the metal flow along the tooth-shaped cavity for filling; During the pressure holding stage, maintain the pressure for 10 - 15 seconds, utilize the metal creep effect to fill the dead corners such as the tooth top and tooth root, ensure that the cavity filling rate is ≥ 98%, and reduce the springback deformation; The final forging temperature is strictly controlled at 850 - 900 °C (cracks are likely to occur below this range, and grain coarsening will occur above this range).

[0026] The final forging die comprises an upper die 4 and a lower die 5, wherein the upper die 4 and the lower die 5 are both provided with an axial cavity 6, an upper die plate 10 is provided above the upper die 4, a punch 11 penetrating the top of the upper die 4 is provided at the bottom of the upper die plate 10, and a pull rod 12 penetrating the upper die 4 is provided at both sides of the punch 11 at the bottom of the upper die plate 10, and the blank is axially extruded by the punch 11, a mounting plate 16 is installed at the bottom of the upper die 4, and side die plates 9 are slidably installed on both sides of the mounting plate 16, and a tooth die 15 is installed on the side of the side die plate 9 facing the mounting plate 16, and after the two tooth die plates 15 are radially pressurized, a tooth-shaped cavity 7 is formed between the two tooth die plates 15; A lower mold plate 14 is installed at the bottom of the lower mold 5, a top plate 18 is provided at the inner bottom of the lower mold 5, and a top rod 19 is provided at the bottom of the top plate 18. By applying pressure to the top rod 19, the top plate 18 is driven to rise and fall, so that the formed gear shaft forging can be easily pushed out of the invention, making it convenient to take out the material.

[0027] Guide rods 13 are installed at both ends of the side template 9, and ear plates 17 are symmetrically installed at both ends of the mounting plate 16. The guide rods 13 penetrate the ear plates 17 and slide, and apply radial pressure to the side template 9 to drive the side template 9 to move, so as to extrude the blank located in the gear cavity; The bottom of both ends of the mounting plate 16 are symmetrically mounted with a holding mechanism 8, through which the blank on the lower die 5 is preliminarily positioned to keep the blank stable during forging. The holding mechanism 8 includes a mounting frame 801 fixedly connected to the mounting plate 16, the bottom end of the mounting frame 801 is rotatably connected to a holding frame 804 via a rotating shaft 808, the holding frame 804 is U-shaped, and the end of the holding frame 804 is connected to a holding plate 807 via an elastic telescopic rod 806, and the side of the holding plate 807 facing the blank is arc-shaped, and the holding plate 807 is clamped in the clamp. The elastic telescopic rod 806 includes a sleeve and an inner rod connected by a compression spring, which is convenient for increasing the contact pressure between the pressing plate 807 and the blank during clamping, thereby improving the clamping effect. A bottom plate 805 with one end extending toward the bottom of the pressing plate 807 is fixedly installed at the bottom of the pressing frame 804. When the bottom plate 805 descends, it is convenient to abut against the lower mold 5, so that the turning of the pressing mechanism 8 is smoother and more stable, reducing the wear on the elastic telescopic rod 806 and the bottom of the pressing plate 807, thereby improving the service life of the pressing mechanism 8; A tail plate 802 is installed at the bottom of the outer side surface of the mounting frame 801, and the tail plate 802 is connected to the holding frame 804 by a spring 803. When clamping, the elastic force of the spring 803 drives the holding plate 807 to rotate toward the blank and hold the blank. At the same time, after the flipping is completed, the upper mold is raised, and the holding plate 807 is reset by the spring 803 to facilitate the holding of the next blank.

[0028] S3: Temperature control cooling and waste heat treatment S31, using gradient controlled cooling process, Transfer the forging to a dual-channel temperature-controlled box within 10 seconds after forging: S311. First stage (final forging temperature → 800 °C): Air cooling (cooling rate 30 - 40 °C / s), quickly skip the grain growth sensitive zone (700 - 900 °C).

[0029] S312. Second stage (800 °C → 500 - 550 °C): Mist cooling (cooling rate 20 - 30 °C / s), inhibit bainite transformation.

[0030] S32. Post-forging isothermal normalizing S321. Utilize the heat of the forging (500 - 550 °C) to directly enter the normalizing furnace, hold at 680 - 720 °C for 2 - 3 hours, and introduce a hydrogen-nitrogen mixed gas (H 2 with a proportion of 3% - 5%) into the furnace to accelerate carbide spheroidization.

[0031] The hardness after normalizing is 180 - 220 HB, and the grain size reaches ASTM 8 - 10 (the traditional process is 6 - 7).

[0032] S4: Composite heat treatment S41. Local carburizing and quenching; S42. Adopt shielded gas carburizing: Only carburize the tooth area, and coat other parts with anti-carburizing paint (SiO 2 base).

[0033] Carburizing parameters: Temperature: 920 - 930 °C Carbon potential: 1.1% - 1.3% C Time: 4 - 6 hours (case depth 1.2 - 1.8 mm) Quenching medium: Step-by-step oil cooling, cool in hot oil at 120 °C for 10 s and then transfer to cold oil at 60 °C to reduce quenching distortion.

[0034] S43. Deep cryogenic treatment and tempering S431. Immediately conduct -80 °C deep cryogenic treatment after quenching and hold for 2 hours to transform retained austenite.

[0035] S432. Tempering process: Low-temperature tempering: 200 - 250 °C × 4 - 6 hours, eliminate stress, and maintain hardness at 58 - 62 HRC; Additional vibration aging treatment (frequency 50 Hz, amplitude 0.5 mm) to further stabilize dimensional accuracy.

[0036] S5: Quality inspection Embed an infrared thermal imager (accuracy ±5 °C) and a laser displacement sensor (accuracy ±0.02 mm) during forging to monitor temperature and deformation in real time.

[0037] The above are only specific application examples of the present invention and do not constitute any limitation to the protection scope of the present invention. Any technical solutions formed by equivalent transformation or equivalent substitution fall within the protection scope of the present invention's rights.

Claims

1. A reducer transmission gear shaft forging, characterized in that: The invention comprises a tooth portion (3) and a shaft portion (2), wherein the tooth portion (3) and the shaft portion (2) are integrally forged from alloy steel, a strengthening boss having a thickness 1.2 to 1.5 times the tooth height is provided at the tooth root, and an inner concave positioning groove having a depth of 8 to 10% of the shaft diameter is provided on the end face of the shaft portion.

2. A forging process for a reducer transmission gear shaft forging according to claim 1, characterized in that: The steps include: Step 1: blank pretreatment; Heating of the blank after cutting; Step 2: Multi-directional composite forging; Initial forging: axial upsetting on a press; Final forging: using the final forging die, after the upper and lower dies are closed, radial pressure and axial pressure are applied simultaneously to make the metal flow and fill along the tooth-shaped cavity (7); The final forging die comprises an upper die (4) and a lower die (5), wherein the upper die (4) and the lower die (5) are both provided with an axial cavity (6), an upper die plate (10) is provided above the upper die (4), a punch (11) penetrating the top of the upper die (4) is provided at the bottom of the upper die plate (10), and pull rods (12) penetrating the upper die (4) are provided at both sides of the punch (11) at the bottom of the upper die plate (10), a mounting plate (16) is installed at the bottom of the upper die (4), side die plates (9) are slidably installed on both sides of the mounting plate (16), a tooth die (15) is installed on the side of the side die plate (9) facing the mounting plate (16), and after radial pressure is applied to the two tooth die plates (15), a tooth-shaped cavity (7) is formed between the two tooth die plates (15), guide rods (13) are installed at both ends of the side die plate (9), and the mounting plate (16) is provided with a tooth-shaped cavity (7). Ear plates (17) slidably connected to the guide rod (13) are symmetrically mounted at both ends; holding mechanisms (8) are symmetrically mounted at the bottom of both ends of the mounting plate (16); the holding mechanism (8) comprises a mounting frame (801) fixedly connected to the mounting plate (16); the bottom end of the mounting frame (801) is rotatably connected to a holding frame (804) via a rotating shaft (808); the holding frame (804) is U-shaped; the end of the holding frame (804) is connected to a holding plate (807) via an elastic telescopic rod (806); the holding plate (807) has an arc-shaped surface facing the blank; a bottom plate (805) having one end extending toward the bottom of the holding plate (807) is fixedly mounted at the bottom of the holding frame (804); a tail plate (802) is mounted at the bottom of the outer side surface of the mounting frame (801); the tail plate (802) is connected to the holding frame (804) via a spring (803); Step 3: Temperature controlled cooling and waste heat treatment; Step 4: Composite heat treatment; Step 5: Quality inspection.

3. The forging process of a reducer transmission gear shaft forging according to claim 2, characterized in that: In step 2, the final forging temperature is 850-900°C.

4. The forging process of a reducer transmission gear shaft forging according to claim 2, characterized in that: In step 3, the temperature-controlled cooling includes a first-stage air cooling and a second-stage mist cooling. The air cooling reduces the temperature to 800°C, and the mist cooling reduces the temperature from 800°C to 500°C-550°C.

5. The forging process of a reducer transmission gear shaft forging according to claim 4, characterized in that: In step 3, the residual heat treatment is to use the residual heat of the forging to enter the normalizing furnace, keep it at 680-720℃ for 2-3 hours, and introduce a hydrogen and nitrogen mixed gas into the furnace.

6. The forging process of a reducer transmission gear shaft forging according to claim 2, characterized in that: In step 4, the composite heat treatment includes local carburizing and quenching and deep cryogenic treatment and tempering.

7. The forging process of a reducer transmission gear shaft forging according to claim 2, characterized in that: In step 5, quality inspection is to monitor the temperature and deformation in real time during the forging process through an infrared thermal imager and a laser displacement sensor.

8. The forging process of a reducer transmission gear shaft forging according to claim 2, characterized in that: In step 1, the internal defects of the blank are detected by ultrasonic testing, and the blank is heated to 1150-1200°C and kept at this temperature for 2-3 hours.

9. The forging process of a reducer transmission gear shaft forging according to claim 2, characterized in that: A lower mold plate (14) is installed at the bottom of the lower mold (5), a top plate (18) is provided at the inner bottom of the lower mold (5), and a top rod (19) is provided at the bottom of the top plate (18).

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