A manufacturing process of high-precision thin-wall gear ring

Abstract

This invention discloses a manufacturing process for high-precision thin-walled gear rings, comprising the following steps: precision casting, rough grinding of end faces and tooth surfaces, heat treatment, fine grinding of tooth surfaces, and ion nitriding. The precision casting process includes the following steps: wax pattern preparation, shell preparation, shell preheating, shell assembly with a die-casting machine, gear ring material melting, and vacuum low-pressure ultrasonic casting. The heat treatment process includes the following steps: high-temperature solution treatment, cyclic quenching, and tempering. Using the process steps described in this invention can effectively ensure the hardness of the tooth surface and the depth of the nitrided layer, reduce machining deformation of the thin-walled gear ring, improve the machining efficiency and precision of the gear ring, thereby extending the service life of equipment and reducing production and operating costs.

Description

Technical Field

[0001] This invention relates to the field of mechanical manufacturing technology, specifically to a manufacturing process for a high-precision thin-walled gear ring. Background Technology

[0002] Thin-walled gear rings, as key components of planetary reducers, are widely used in transmission devices of heavy-duty equipment in fields such as hoisting and transportation, metallurgy, mining, petrochemicals, shipbuilding, weaponry, and aerospace, serving functions such as load bearing, load sharing, and transmission. To minimize the effective size of the planetary reducer, the wall thickness of the thin-walled gear ring needs to be reduced to the greatest extent possible, resulting in a significant difference between its wall thickness and its radial and axial dimensions. During machining and heat treatment, due to clamping forces, cutting forces, and internal stresses, the thin-walled gear ring, as a typical thin-walled component, is prone to significant deformation and vibration. Furthermore, to ensure the hardness and wear resistance of the gear ring tooth surface, reduce wear, pitting, plastic deformation during gear meshing, and prevent scuffing during high-speed heavy-duty transmission, nitriding treatment of the tooth surface is required, with a nitriding layer depth of at least 0.3 mm.

[0003] Due to the structural characteristics of thin-walled gear rings and the technical difficulties in their manufacturing process, they suffer from large and uncontrollable deformation, numerous production processes, long production cycles, and high production costs. These factors affect the precision of machining and assembly, and restrict their mass production and quality improvement. Summary of the Invention

[0004] To address the aforementioned technical problems in the existing technology, this invention provides a manufacturing process for high-precision thin-walled gear rings.

[0005] The technical solution of this invention to solve the above-mentioned technical problems is: a manufacturing process for a high-precision thin-walled gear ring includes the following steps:

[0006] S1, Precision Casting: Select the raw material for the gear ring, and according to the shape and dimensions of the gear ring in the component process card, proceed through processes such as wax pattern preparation, shell preparation and flame retardant treatment, shell preheating, shell assembly with die casting machine, gear ring material melting, and vacuum low-pressure ultrasonic casting to obtain the semi-finished gear ring.

[0007] S2, Rough grinding of end face and tooth surface: After precision casting is completed, the end face and tooth surface of the gear ring semi-finished product are rough ground.

[0008] S3, Heat treatment: The semi-finished gear ring with rough grinding of the end face and tooth surface is subjected to solution treatment, cyclic quenching and tempering to refine the grains and relieve stress.

[0009] S4, Gear surface finishing: After the semi-finished gear ring has been heat-treated, its gear surface is finished, and then magnetic flaw detection and demagnetization are performed.

[0010] S5, Ion Nitriding: After the tooth surface of the semi-finished gear ring is precision ground, it is subjected to ion nitriding to obtain the finished gear ring, and its accuracy is tested.

[0011] Furthermore, in step S1, the raw material selected for precision casting of the gear ring is alloy structural steel that has undergone nitriding treatment.

[0012] Furthermore, in step S1, the precision casting process steps are as follows:

[0013] S101, Wax pattern preparation: Based on the shape and dimensions of the toothed ring in the part process card, design and manufacture the wax pattern and sprue, combine the wax pattern and sprue into a wax pattern, and inspect, correct and repair it.

[0014] S102, Shell preparation: Apply slurry to the wax model, coat it with sand, dry it, dewax it, and fire it to obtain the shell;

[0015] S103, Shell preheating: Fix the shell in the heat preservation device and place it in the electric heating furnace for preheating;

[0016] S104, Assembly of mold shell and die casting machine: Connect the preheated mold shell to the riser pipe of the vacuum low-pressure casting machine, place a filter screen between the mold shell and the riser pipe and seal it, and perform anti-oxidation protection treatment.

[0017] S105, Gear ring material melting: Melting gear ring material under a protective atmosphere or flux protection;

[0018] S106, Vacuum Low-Pressure Ultrasonic Casting: The molten gear ring material is passed through a vacuum low-pressure casting machine and pressed into a mold shell connected to a riser pipe. At the same time, ultrasonic vibration is applied to the mold shell to form a precision gear ring casting.

[0019] Furthermore, the shell fabrication process in step S102 is as follows: a layer of mixed coating is applied to the surface of the wax model. This mixed coating is made of 320-mesh zircon powder and silica sol at a powder-to-liquid ratio of 1:3. The silica sol is diluted with deionized water, and a wetting agent and defoamer are added. Next, a layer of 100-120 mesh zircon sand is applied using a rain-sprinkling sanding method and then dried. This process is repeated, applying 6-9 layers of zircon sand, and the resulting shell is dried for more than 24 hours. Then, the wax is removed using a rapid dewaxing method with a hot air gun. Finally, the shell is fired at 800-1000℃ for more than 2 hours and then cooled in the furnace.

[0020] Furthermore, in step S103, the preheating temperature of the shell is 400-500°C, and the preheating time is 2-3 hours.

[0021] Furthermore, in step S106, the pouring temperature of vacuum low-pressure ultrasonic casting is 1500-1600℃, the crystallization pressure is 25-35KPa, the holding time is 100-300s, and the ultrasonic power is 1000-1100W.

[0022] Furthermore, in step S2, a precision grinding machine is used to grind the two end faces of the gear ring semi-finished product to the design size, with a surface roughness value Ra = 0.6 μm; before grinding the surface, the working surface of the grinding machine and the positioning reference surface of the part are required to be clean, and sand particles and burrs are not allowed; a precision forming grinding wheel gear grinding machine is used to perform rough grinding of the tooth surface, leaving a single-sided allowance of 0.15 to 0.20 mm for each tooth.

[0023] Furthermore, in step S3, the heat treatment process steps are as follows:

[0024] S301 Solution treatment: The precision-cast gear ring semi-finished product is heated to 880-920℃ at a rate of 10-15℃ / min, held at the temperature for 60-90min, and then oil-cooled at an oil temperature of 55-65℃.

[0025] S302. Cyclic quenching: The solution-treated gear ring semi-finished product is heated to 800-850℃ at a rate of 10-15℃ / min, held for 5-10min and then oil-cooled at an oil temperature of 55-65℃; this cycle is repeated 3-5 times.

[0026] S303, Tempering: The semi-finished gear ring after cyclic quenching is heated to 560-600℃ at a rate of 10-15℃ / min, held for 120-180min and then water-cooled.

[0027] Furthermore, in step S4, a precision forming grinding machine is used to perform precision forming grinding according to the design dimensions, removing all machining allowances, and achieving a precision level of 2 after grinding; the pitch circle of the internal teeth is aligned, ensuring that the runout of the pitch circles of the internal and external teeth is no greater than 0.03; magnetic flaw detection is used to detect product defects such as microcracks and dents in the gear ring; after demagnetization, the magnetic induction intensity of the part does not exceed 1×10 -4 T.

[0028] Furthermore, the ion nitriding process in step S4 is as follows: the semi-finished gear ring with finely ground tooth surfaces is placed in a vacuum ion nitriding furnace and heated to 300°C at a rate of 2.5–3°C / min; then heated to 500–550°C at a rate of 1.5–2°C / min, with an ammonia flow rate of 700–900 ml / min, a furnace pressure of 250–300 Pa, and a holding time of 15–20 h; then cooled to 300°C at a rate of 1.0–1.5°C / min while still glowing; the furnace is then stopped and cooled to 150°C at a rate of 1.0–1.5°C / min; the ring is then removed from the furnace and air-cooled to room temperature.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] This invention replaces the forging, rough turning, finish turning, and gear shaping processes in conventional thin-walled gear ring manufacturing with precision casting. This allows for a one-time molding of the gear ring semi-finished product, reducing machining errors caused by machine tool and fixture changes and tool setting, thus saving production time. During precision casting, ultrasonic vibration is applied to the mold shell, accelerating the filling of the gear ring material molten metal and refining the grain size. In the heat treatment process, solution treatment, cyclic quenching, and tempering further refine the grain size of the gear ring material, facilitating the penetration and diffusion of nitrogen atoms in the subsequent nitriding process, increasing tooth surface hardness, and reducing internal stress in the semi-finished gear ring. Placing ion nitriding as the final process avoids the problem of insufficient nitriding layer depth and tooth surface hardness caused by the traditional method of nitriding followed by grinding, resulting in less machining allowance and deformation, and improved machining efficiency. Through the process steps described in this invention, tooth surface hardness and nitriding layer depth can be effectively guaranteed, reducing machining deformation of thin-walled gear rings, improving machining efficiency and accuracy, thereby extending equipment service life and reducing production and operating costs. The process steps described in this invention can effectively ensure the hardness of the tooth surface and the depth of the nitriding layer, reduce the deformation during the processing of thin-walled gear rings, improve the processing efficiency and accuracy of gear rings, thereby extending the service life of equipment and reducing production and usage costs. Attached Figure Description

[0031] Figure 1 This is a flowchart of the manufacturing process in an embodiment of the present invention. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, these embodiments do not limit the present invention, and any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the scope of protection of the present invention.

[0033] like Figure 1 As shown, this invention discloses a manufacturing process for a high-precision thin-walled gear ring, the process comprising the following steps:

[0034] S1. Precision casting: 42CrMo is selected as the raw material for the gear ring. According to the shape and dimensions of the gear ring in the component process card, the semi-finished gear ring is obtained through processes such as wax pattern preparation, shell preparation and flame retardant treatment, shell preheating, shell assembly with die casting machine, gear ring material melting, and vacuum low-pressure ultrasonic casting.

[0035] S2. Rough grinding of end faces and tooth surfaces: After precision casting is completed, the end faces and tooth surfaces of the gear ring semi-finished product are rough ground.

[0036] S3. Heat treatment: The semi-finished gear ring with rough grinding of the end face and tooth surface is subjected to solution treatment, cyclic quenching and tempering to refine the grains and relieve stress.

[0037] S4. Gear surface finishing: After the semi-finished gear ring has been heat-treated, its gear surface is finished, and then magnetic flaw detection and demagnetization are performed.

[0038] S5. Ion Nitriding: After the tooth surface of the semi-finished gear ring is precision ground, it is ion nitrided to obtain the finished gear ring, and its accuracy is tested.

[0039] Furthermore, in step S1, the raw material selected for precision casting of the gear ring is alloy structural steel that can be nitrided.

[0040] Furthermore, in step S1, the precision casting process steps are as follows:

[0041] S101. Wax pattern preparation: Based on the shape and dimensions of the toothed ring in the component process card, design and manufacture the wax pattern and sprue, combine the wax pattern and sprue into a wax pattern, and inspect, correct and repair it.

[0042] S102, Shell preparation: Apply slurry, sand, dry, dewax, and fire the wax model to obtain the shell;

[0043] S103. Shell preheating: Fix the shell in the heat preservation device and place it in the electric heating furnace for preheating;

[0044] S104. Assembly of the mold shell and die casting machine: Connect the preheated mold shell to the riser pipe of the vacuum low-pressure casting machine. Place a filter screen between the mold shell and the riser pipe and seal it, and perform anti-oxidation protection treatment.

[0045] S105. Gear ring material melting: Melting the gear ring material under a protective atmosphere or flux protection;

[0046] S106. Vacuum low-pressure ultrasonic casting: The molten gear ring material is passed through a vacuum low-pressure casting machine and pressed into a mold shell connected to a riser pipe. At the same time, ultrasonic vibration is applied to the mold shell to form a precision gear ring casting.

[0047] Furthermore, the shell fabrication process in step S102 is as follows: a layer of mixed coating is applied to the surface of the wax model. This mixed coating is made of 320-mesh zircon powder and silica sol at a powder-to-liquid ratio of 1:3. The silica sol is diluted with deionized water, and a wetting agent and defoamer are added. Next, a layer of 120-mesh zircon sand is applied using a rain-sprinkling sanding method and then dried. This process is repeated for 8 layers of zircon sand, and the resulting shell is dried for 24 hours. Then, the wax is removed using a rapid dewaxing method with a hot air gun. Finally, the shell is fired at 900°C for 2 hours and cooled in the furnace.

[0048] Furthermore, in step S103, the preheating temperature of the shell is 400°C and the preheating time is 3 hours.

[0049] Furthermore, in step S106, the pouring temperature of vacuum low-pressure ultrasonic casting is 1550℃, the crystallization pressure is 30KPa, the holding time is 200s, and the ultrasonic power is 1000W.

[0050] Furthermore, in step S2, a precision grinding machine is used to grind the two end faces of the gear ring semi-finished product to the design size, with a surface roughness value Ra = 0.6 μm; before grinding the surface, the working surface of the grinding machine and the positioning reference surface of the part are required to be clean, and sand particles and burrs are not allowed; a precision forming grinding wheel gear grinding machine is used to perform rough grinding of the tooth surface, leaving a single-sided allowance of 0.20 mm per tooth.

[0051] Furthermore, in step S3, the heat treatment process steps are as follows:

[0052] S301 Solution treatment: The precision-cast gear ring semi-finished product is heated to 900℃ at a rate of 15℃ / min, held at that temperature for 90min, and then oil-cooled at an oil temperature of 60℃.

[0053] S302. Cyclic quenching: The solution-treated gear ring semi-finished product is heated to 820℃ at a rate of 10℃ / min, held for 5 minutes, and then oil-cooled at 60℃; this cycle is repeated 4 times.

[0054] S303, Tempering: The semi-finished gear ring after cyclic quenching is heated to 580℃ at a rate of 10℃ / min, held for 180min and then water-cooled.

[0055] Furthermore, in step S4, a precision forming grinding machine is used to perform precision forming grinding according to the design dimensions, removing all machining allowances, and achieving a precision level of 2 after grinding; the pitch circle of the internal teeth is aligned, ensuring that the runout of the pitch circles of the internal and external teeth is no greater than 0.03; magnetic flaw detection is used to detect product defects such as microcracks and dents in the gear ring; after demagnetization, the magnetic induction intensity of the part does not exceed 1×10 -4 T.

[0056] Furthermore, the ion nitriding process in step S4 is as follows: the semi-finished gear ring with finely ground tooth surface is placed in a vacuum ion nitriding furnace and heated to 300°C at a rate of 2.5°C / min; then heated to 520°C at a rate of 1.5°C / min, with an ammonia flow rate of 900 ml / min, a furnace pressure of 250 Pa, and a holding time of 18 h; then cooled to 300°C at a rate of 1.0°C / min while still glowing; the furnace is then stopped and cooled to 150°C at a rate of 1.0°C / min; the ring is then removed from the furnace and air-cooled to room temperature.

Claims

1. A manufacturing process for a high-precision thin-walled gear ring, characterized in that, The process includes the following steps: S1, Precision Casting: Select the raw material for the gear ring, and according to the shape and dimensions of the gear ring in the component process card, proceed through wax pattern preparation, shell preparation and flame retardant treatment, shell preheating, shell assembly with the die-casting machine, gear ring material melting, and vacuum low-pressure ultrasonic casting to obtain the semi-finished gear ring; specifically: S101. Wax pattern preparation: Based on the shape and dimensions of the toothed ring in the component process card, design and manufacture the wax pattern and sprue, combine the wax pattern and sprue into a wax pattern, and inspect, straighten and repair it. S102, Shell preparation: Apply slurry, sand, dry, dewax, and fire the wax model to obtain the shell; S103. Shell preheating: Fix the shell in the heat preservation device and place it in the electric heating furnace for preheating; S104. Assembly of the mold shell and die casting machine: Connect the preheated mold shell to the riser pipe of the vacuum low-pressure casting machine. Place a filter screen between the mold shell and the riser pipe and seal it, and perform anti-oxidation protection treatment. S105. Gear ring material melting: Melting the gear ring material under a protective atmosphere or flux protection; S106. Vacuum low-pressure ultrasonic casting: The molten gear ring material is pressed into a mold shell connected to the riser pipe through a vacuum low-pressure casting machine, and ultrasonic vibration is applied to the mold shell at the same time to form a precision gear ring casting. S2, Rough grinding of end face and tooth surface: After precision casting is completed, the end face and tooth surface of the gear ring semi-finished product are rough ground. S3, Heat Treatment: The semi-finished gear ring, after rough grinding of the end faces and tooth surfaces, undergoes solution treatment, cyclic quenching, and tempering to refine the grains and relieve stress; the heat treatment process steps are as follows: S301 Solution treatment: The precision-cast gear ring semi-finished product is heated to 880-920℃ at a rate of 10-15℃ / min, held at the temperature for 60-90min, and then oil-cooled at an oil temperature of 55-65℃. S302. Cyclic quenching: The solution-treated gear ring semi-finished product is heated to 800-850℃ at a rate of 10-15℃ / min, held for 5-10min and then oil-cooled at an oil temperature of 55-65℃; this cycle is repeated 3-5 times. S303, Tempering: The semi-finished gear ring after cyclic quenching is heated to 560-600℃ at a rate of 10-15℃ / min, held for 120-180min and then water-cooled. S4, Gear surface finishing: After the semi-finished gear ring has been heat-treated, its gear surface is finished, and then magnetic flaw detection and demagnetization are performed. S5, Ion Nitriding: After the tooth surface of the semi-finished gear ring is precision ground, it is ion nitrided to obtain the finished gear ring, and its accuracy is tested. The specific steps are as follows: the semi-finished gear ring with precision ground tooth surface is placed in a vacuum ion nitriding furnace and heated to 300℃ at a rate of 2.5-3℃ / min; then heated to 500-550℃ at a rate of 1.5-2℃ / min, with an ammonia flow rate of 700-900ml / min, a furnace pressure of 250-300Pa, and a holding time of 15-20h; then cooled to 300℃ at a rate of 1.0-1.5℃ / min with glow discharge; the furnace is stopped, and the temperature is cooled to 150℃ at a rate of 1.0-1.5℃ / min; the gear ring is removed from the furnace and air-cooled to room temperature.

2. The manufacturing process of a high-precision thin-walled gear ring according to claim 1, characterized in that, In S1, the raw material selected for precision casting of the gear ring is alloy structural steel that has undergone nitriding treatment.

3. The manufacturing process of a high-precision thin-walled gear ring according to claim 1, characterized in that, The process of making the S102 medium shell is as follows: A layer of mixed coating is applied to the surface of the wax model. The mixed coating is made of 320-mesh zircon powder and silica sol at a powder-to-liquid ratio of 1:

3. The silica sol is diluted with deionized water and a wetting agent and defoamer are added. Then, a layer of 100-120 mesh zircon sand is applied by a rain-sprinkling sanding method and dried. This process is repeated for 6-9 layers of zircon sand, and the resulting shell is dried for more than 24 hours. Then, the wax is removed by a hot air gun using a rapid dewaxing method. Finally, the shell is fired at 800-1000℃ for more than 2 hours and cooled in the furnace.

4. The manufacturing process of a high-precision thin-walled gear ring according to claim 1, characterized in that, In S103, the preheating temperature of the shell is 400-500℃, and the preheating time is 2-3 hours.

5. The manufacturing process of a high-precision thin-walled gear ring according to claim 1, characterized in that, In S106, the pouring temperature of vacuum low-pressure ultrasonic casting is 1500-1600℃, the crystallization pressure is 25-35KPa, the holding time is 100-300s, and the ultrasonic power is 1000-1100W.

6. The manufacturing process of a high-precision thin-walled gear ring according to claim 1, characterized in that, In step S2, a precision grinding machine is used to grind the two end faces of the gear ring semi-finished product to the design size, with a surface roughness value Ra=0.6μm; a precision forming grinding wheel gear grinding machine is used for rough grinding of the tooth surface, leaving a single-sided allowance of 0.15~0.20mm for each tooth.

7. The manufacturing process of a high-precision thin-walled gear ring according to claim 1, characterized in that, In step S4, a precision forming grinding machine is used to perform precision forming grinding according to the design dimensions, removing all machining allowances, and achieving a precision level of 2 after grinding; the pitch circle of the internal teeth is aligned, ensuring that the runout of the pitch circles of the internal and external teeth does not exceed 0.03; magnetic flaw detection is used to detect microcracks and product defects such as impacts in the gear ring; after demagnetization, the magnetic induction intensity of the parts does not exceed 1×10 -4 T.

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