A forging process for gearbox gear blank forging

Abstract

The present invention discloses a forging process for gearbox gear blank forgings, which specifically includes the following steps: blanking → heating → blank making → forming → trimming → punching → heat treatment → shot blasting → flaw detection → inspection → issuance. The process steps of the present invention are simple, and the first-time qualified rate of the metallographic structure of the gear blank is significantly improved. A preheating step is added, and preheat treatment is performed in advance to obtain a more delicate normalizing structure, so that the produced forging products have excellent performance, can effectively improve the forging streamline and mechanical properties of the forging, improve product quality, and extend the life of the forging. 2. During forging, the present invention adds a spring to the forging die by punching up and pressing down, adopts a high-strength heavy-load spring, calculates the required force, selects the spring specifications, and effectively controls the flash thickness during forging; 3. Compared with the existing forging process, the present invention saves materials and manpower, saves time and effort, and saves equipment occupation, and is suitable for wide promotion and use.

Description

Technical Field

[0001] The invention belongs to the technical field of precision forging, and in particular relates to a forging process for a gearbox gear blank forging. Background Art

[0002] Gears are key mechanical components in steam turbines and gearboxes, and their quality directly impacts the performance of related products. Currently, gears are typically made of low-carbon steel, and the properties of low-carbon steel naturally determine the performance of the gears. Large gear blanks are currently widely used in China through die forging, due to their dense and uniform structure, continuous streamlines, high dimensional accuracy, and ease of forging internal material defects and broken dendritic structures. They are gradually replacing bulky open-die forgings and low-strength castings. However, existing methods for forging gears typically employ traditional forging processes. The process from blank to finished product is complex, inefficient, with high waste and low raw material utilization. Furthermore, controlling the flash thickness during forging is a technical challenge for gearbox gear blank forgings. Patent No. CN1544181A provides a composite manufacturing process for automotive gearboxes and gear blanks, which improves the overall mechanical properties of the gears to a certain extent. However, the process does not offer significant improvements, and the flash thickness cannot be controlled. Summary of the Invention

[0003] The object of the present invention is to provide a forging process for a gearbox gear blank forging to solve the problems raised in the above background technology.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is: a forging process for a gearbox gear blank forging, which specifically includes the following steps: blanking → heating → blanking → forming → trimming → punching → heat treatment → shot blasting → flaw detection → inspection → issuance:

[0005] (1) Cutting: Use vacuum degassed + refined steel billets as raw materials and cut the steel billets on a sawing machine;

[0006] (2) Heating: The blank obtained in step 1 is added to the medium frequency induction heating furnace for heating through a mechanical automatic loading device;

[0007] (3) Blank making: After the blank is made into a blank for forging, it is transferred to the forging die for forging. The direction of the forging hammer is perpendicular to the crystallization direction of the billet, and the forging is repeated. The forging die includes an upper die and a lower die. A heavy-load spring is provided between the upper and lower dies to control the thickness of the flash.

[0008] (4) Forming and trimming: The final forging is transported to the trimming station via the conveyor chain for trimming according to the required size;

[0009] (5) Punching: Use a conical punch block to punch. The conical punch block is placed in the ring in the center of the cross-shaped bracket. The cross-shaped bracket is placed on the outside of the steel billet. After one side is completed, punch again on the reverse side.

[0010] (6) Heat treatment: quenching, tempering and then air cooling the blank at room temperature;

[0011] (7) Grinding and shot blasting: The formed forgings are subjected to grinding and shot blasting in sequence. The grinding includes circular grinding and chamfering. The shot blasting is to place the forgings in a shot blasting machine to remove burrs and oxide scales, and then perform surface phosphorus saponification treatment to obtain precisely forged forging products.

[0012] (8) NDT: First spray the magnetic suspension, then conduct magnetic detection, and repeat twice. Finally, demagnetize the finished product and inspect it.

[0013] A further improvement of the present invention is that: before the blanking step, a pretreatment step is also included, and impurities on the surface of the steel billet are polished by a polishing device to remove impurities and defects on the surface of the steel billet, and then the polished steel billet is cleaned multiple times and dried for standby use.

[0014] A further improvement of the present invention is that in step (2), the temperature is first preheated to 600-700°C, kept warm for 3-4 hours, and then heated to 1000-1200°C.

[0015] A further improvement of the present invention is that in step (6), quenching is performed by oil cooling at 950-1000°C, and tempering is performed by slow cooling at 200-300°C.

[0016] A further improvement of the present invention is that in step (3), the blank is first forged using a 100-ton punch press, then pre-forged using a 1000-ton friction press, and then final forged using a 630-ton friction press, with the final forging temperature being 700-800°C.

[0017] A further improvement of the present invention is that: in the step (8), the magnetic suspension is evenly sprayed on the surface of the forging, and then the forging is placed in an environment of 100-150°C, and the interior of the forging is detected by a magnetic detector to ensure the quality of the forging. After the magnetic detection is completed, the magnetic suspension on the surface of the forging is removed, and the interior of the forging is re-detected using an ultrasonic flaw detector.

[0018] A further improvement of the present invention is that the magnetic suspension is a mixture of oily fluorescent magnetic powder, odorless kerosene, flux and surfactant.

[0019] A further improvement of the present invention is that the steel billet is 20CrMnTi carburizing steel with a carbon content of 0.17-0.24 wt%.

[0020] Compared with the prior art, the beneficial effects of the present invention are: 1. The process steps are simple, which significantly improves the first-time qualified rate of the metallographic structure of the gear blank, adds a preheating step, preheats in advance, and obtains a more delicate normalizing structure, so that the forging products produced have excellent performance, can effectively improve the streamline of the forging and the mechanical properties of the forging, improve the quality of the product, and extend the life of the forging. 2. During forging, the present invention adds a spring to the forging die by punching up and pressing down, adopts a high-strength heavy-load spring, calculates the required force, selects the spring specifications, and effectively controls the flash thickness during forging; 3. Compared with the existing forging process, it saves materials and manpower, saves time and effort, and saves equipment occupation, and is suitable for wide promotion and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of forging die;

[0022] 1-upper die, 2-lower die, 3-spring. DETAILED DESCRIPTION

[0023] The present invention is further illustrated by the following examples. The present invention can be better understood according to the following examples. However, it will be readily understood by those skilled in the art that the specific process conditions and results described in the examples are merely illustrative of the present invention and should not and will not limit the present invention as described in detail in the claims.

[0024] This embodiment provides a forging process for a gearbox gear blank forging, which specifically includes the following steps: blanking → heating → blanking → forming → trimming → punching → heat treatment → shot blasting → flaw detection → inspection → issuance:

[0025] (1) Blanking: vacuum degassed + refined steel billets are selected as raw materials. The steel billets are 20CrMnTi carburizing steel with a carbon content of 0.17-0.24wt%. The steel billets are then cut by sawing. Before the blanking step, a pretreatment step is also included. Impurities on the surface of the steel billets are polished by a polishing device to remove impurities and defects on the surface of the steel billets. The polished steel billets are then washed multiple times and dried for standby use.

[0026] (2) Heating: The blank obtained in step 1 is added to the medium frequency induction heating furnace through a mechanical automatic loading device for heating. The temperature is first preheated to 650°C, kept warm for 3 hours, and then heated to 1100°C;

[0027] (3) Blanking: After the blank is made into a blank for forging, it is transferred to the forging die for forging. The direction of the forging hammer is perpendicular to the crystallization direction of the billet, and the forging is repeated. Specifically, the blank is first forged with a 100-ton punch press, then pre-forged with a 1000-ton friction press, and finally final forged with a 630-ton friction press. The final forging temperature is 750°C. The forging die includes an upper die and a lower die. A heavy-load spring is provided between the upper and lower dies to control the thickness of the flash.

[0028] (4) Forming and trimming: The final forging is transported to the trimming station via the conveyor chain for trimming according to the required size;

[0029] (5) Punching: Use a conical punch block to punch. The conical punch block is placed in the ring in the center of the cross-shaped bracket. The cross-shaped bracket is placed on the outside of the steel billet. After one side is completed, punch again on the reverse side.

[0030] (6) Heat treatment: The blank is quenched, tempered and then air-cooled at room temperature. The quenching is done by oil cooling at 950-1000℃, and the tempering is done by slow cooling at 200-300℃.

[0031] (7) Grinding and shot blasting: The formed forgings are subjected to grinding and shot blasting in sequence. The grinding includes circular grinding and chamfering. The shot blasting is to place the forgings in a shot blasting machine to remove burrs and oxide scales, and then perform surface phosphorus saponification treatment to obtain precisely forged forging products.

[0032] (8) Flaw detection: First spray the magnetic suspension, then conduct magnetic detection, and repeat twice. The specific operation is to evenly spray the magnetic suspension on the surface of the forging. The magnetic suspension is a mixture of oily fluorescent magnetic powder, odorless kerosene, flux and surfactant. Then place the forging in an environment of 150°C and use a magnetic detector to detect the inside of the forging to ensure the quality of the forging. After the magnetic detection is completed, the magnetic suspension on the surface of the forging is removed, and the ultrasonic flaw detector is used to check the inside of the forging for damage again. Finally, the finished product is demagnetized and inspected before being shipped.

[0033] In step 3, first calculate the required force, then select the spring specifications. The die action during forging is: when the upper die moves downward, the spring is compressed by the upper die under the action of the spring force, resulting in force deformation. When the designed peak value is reached in a short time, the spring stops moving, so the die also stops moving downward, thereby achieving the effect of controlling the flash thickness.

[0034] The test results of the corresponding gearbox gear blank forgings made by the above process are shown in Table 1. All indicators are within the specified requirements, among which the flash residue and flatness are more advantageous than those of traditional forging.

[0035] Table 1

[0036]

[0037] The embodiments are only used to explain the present invention. The embodiments described above are only preferred implementation modes of the present invention, and are not intended to limit the scope of protection of the present invention. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. Any improvements made based on the spirit of the present invention should be within the scope of protection of the present invention.

Claims

1. A forging process for a gearbox gear blank forging, characterized by: The specific steps include: blanking → heating → blanking → forming → trimming → punching → heat treatment → shot blasting → flaw detection → inspection → dispatching: (1) Cutting: Use vacuum degassed + refined steel billets as raw materials and cut the steel billets on a sawing machine; (2) Heating: The blank obtained in step 1 is added to the medium frequency induction heating furnace for heating through a mechanical automatic loading device; (3) Blank making: After the blank is made into a blank for forging, it is transferred to the forging die for forging. The direction of the hammer drop of the forging press is perpendicular to the crystallization direction of the steel billet, and the forging is repeated. The forging die includes an upper die and a lower die. A heavy-load spring is provided between the upper and lower dies to control the thickness of the flash. During forging, the required force is calculated first, and then the spring specifications are selected. The die action during forging is as follows: when the upper die moves downward, the spring is compressed by the upper die under the action of the spring force, resulting in deformation under force. When the design peak value is reached in a short time, the spring stops moving, so that the die stops moving downward, thereby achieving the effect of controlling the thickness of the flash; (4) Forming and trimming: The final forging is transported to the trimming station via the conveyor chain for trimming according to the required size; (5) Punching: Use a conical punch block to punch. The conical punch block is placed in the ring in the center of the cross-shaped bracket. The cross-shaped bracket is placed on the outside of the steel billet. After one side is completed, punch again on the reverse side. (6) Heat treatment: quenching, tempering and then air cooling the blank at room temperature; (7) Grinding and shot blasting: The formed forgings are subjected to grinding and shot blasting in sequence. The grinding includes circular grinding and chamfering. The shot blasting is to place the forgings in a shot blasting machine to remove burrs and oxide scales, and then perform surface phosphorus saponification treatment to obtain precisely forged forging products. (8) NDT: First spray the magnetic suspension, then conduct magnetic detection, and repeat twice. Finally, demagnetize the finished product and inspect it. The magnetic suspension is a mixture of oily fluorescent magnetic powder, odorless kerosene, flux and surfactant.

2. The forging process for a gearbox gear blank forging according to claim 1, characterized in that: Before the blanking step, a pretreatment step is also included, in which impurities on the surface of the steel billet are polished by a polishing device to remove impurities and defects on the surface of the steel billet, and then the polished steel billet is cleaned multiple times and dried for standby use.

3. The forging process for a gearbox gear blank forging according to claim 1, wherein: In the step (2), the temperature is first preheated to 600-700°C, kept warm for 3-4 hours, and then heated to 1000-1200°C.

4. The forging process for a gearbox gear blank forging according to claim 1, wherein: In the step (6), quenching is performed by oil cooling at 950-1000°C, and tempering is performed by slow cooling at 200-300°C.

5. The forging process for a gearbox gear blank forging according to claim 1, wherein: In the step (3), the blank is first forged using a 100-ton punch press, then pre-forged using a 1000-ton friction press, and then final forged using a 630-ton friction press, with the final forging temperature being 700-800°C.

6. The forging process for a gearbox gear blank forging according to claim 1, characterized in that: In the step (8), the magnetic suspension is evenly sprayed on the surface of the forging, and then the forging is placed in an environment of 100-150°C, and the interior of the forging is detected by a magnetic detector to ensure the quality of the forging. After the magnetic detection is completed, the magnetic suspension on the surface of the forging is removed, and the interior of the forging is re-detected by an ultrasonic flaw detector.

7. The forging process for a gearbox gear blank forging according to claim 1, characterized in that: The steel billet is 20CrMnTi carburizing steel with a carbon content of 0.17-0.24wt%.

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