Induction quenching gear ring machining process

Abstract

The invention relates to the technical field of wind power gear ring machining technologies, in particular to an induction quenching gear ring machining technology which comprises the following steps of an induction quenching procedure, a magnetic powder inspection procedure, a machining center procedure and a finish turning procedure. The induction quenching process comprises a stress relief tempering process; the gear ring needs to be subjected to natural aging treatment after the machining center working procedure, the natural aging time is counted from the completion of the machining center working procedure to the completion of the finish turning working procedure, and the total time is longer than 48 hours. According to the process, the residual stress in the induction quenching gear ring can be effectively eliminated, deformation and cracks of the gear ring are reduced, the service life of the gear ring is prolonged, the machining cost is reduced, the quality control capacity is improved, and the product quality is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of wind power gear ring processing technology, and specifically to an induction hardening gear ring processing technology. Background Art

[0002] Gears are common mechanical transmission components. After precision machining, gears have high tooth profile accuracy, can maintain smoothness during transmission, and reduce vibration and noise. This is very important for improving the stability and reliability of mechanical systems. For example, in the transmission system of an aircraft's wind turbine generator, smooth gear transmission helps ensure the normal operation of the equipment and reduces the risk of failure.

[0003] During the gear processing process, in order to change the surface structure and properties of the gear to improve its wear resistance, fatigue resistance, and contact strength, surface heat treatment is required. There are many surface heat treatment methods, such as induction hardening treatment is one of them. Induction hardening uses the principle of electromagnetic induction to generate induced current in the workpiece in an alternating magnetic field, quickly heat the workpiece surface to the hardening temperature and then cool it, so that the treated workpiece surface obtains high hardness and high wear resistance.

[0004] For the gear ring of induction hardening, in order to improve product quality and efficiency, the prior art "A processing technology of high-precision gear ring" (publication number: CN115609249A) discloses a processing method. Using extrusion instead of the traditional method, only one finishing process is required to complete the processing of the gear ring, which can significantly improve the surface quality of the gear ring, greatly save materials, improve production efficiency, and thus achieve the purpose of reducing product production costs. However, the prior art still has the following technical problems:

[0005] Since the heat treatment method used for the gear ring is the induction hardening process, the surface of the gear ring will quickly reach a high temperature of 800 degrees during quenching. The rapid heating method will cause a large temperature gradient between the surface and the core of the gear ring. Due to the principle of thermal expansion and contraction, the surface expands rapidly while the core lags behind, resulting in large and concentrated residual thermal stress inside the gear ring; at the same time, mechanical processing such as turning, drilling, and gear cutting before the gear ring undergoes induction hardening will also cause residual stress inside the gear ring. Stress concentration inside the material will cause cracks to appear during the installation and use of the gear ring. Under the action of cyclic loads, the cracks will gradually expand, ultimately leading to fatigue damage of the gear ring and reducing the service life of the gear ring. Summary of the Invention

[0006] The present invention provides an induction hardening gear ring processing technology, which can solve the problem that the existing gear ring processing technology is prone to cause cracks in the gear ring and reduce the service life of the gear ring.

[0007] The present application provides the following technical solutions: A processing technology for induction-hardened gear rings, including the following steps: induction hardening process, magnetic particle inspection process, machining center process, finish turning process;

[0008] The induction hardening process includes a stress relief tempering process;

[0009] After the machining center process, the gear ring needs to be subjected to natural aging treatment. The natural aging time is timed from the completion of the machining center process until the start of the finish turning process, and the total time should be greater than 48 hours.

[0010] Beneficial effects:

[0011] 1. Avoid stress concentration and improve the service life of the gear ring. The induction hardening includes a stress relief tempering process, which can eliminate the residual stress generated inside the gear ring during the mechanical processing before and after induction hardening, helping to reduce the deformation and crack generation of the gear ring, thereby improving the service life of the gear ring. At the same time, natural aging treatment after the machining center process is to let the gear ring release the internal stress naturally and slowly through static placement to achieve the effect of eliminating residual stress, which can improve the machining accuracy and stability of the end face and stop of the gear ring in the subsequent finish turning process, improve the machining quality of the gear ring, and the natural aging time is timed from the completion of the machining center process until the start of the finish turning process, and the total time should be greater than 48 hours, allowing the internal stress of the gear ring to be fully released, thereby further avoiding the generation of cracks due to gear ring deformation and ensuring the service life of the gear ring.

[0012] 2. Improve the quality control ability and ensure product quality. Since the tooth part of the gear ring needs to be ground after the finish turning process, magnetic particle inspection after induction hardening can confirm whether the induction hardening process causes cracks in the gear ring, so as to prevent it from being impossible to determine whether the crack is caused by induction hardening or grinding if a crack appears in the gear ring later, which is convenient for intercepting defective products in time after the crack problem appears to improve the quality control ability.

[0013] Furthermore, the interval time between the induction hardening process and the stress relief tempering process does not exceed 2 hours, the tempering temperature is not lower than 180°, and the tempering holding time is not lower than 12 hours.

[0014] Beneficial effects: After induction hardening, there is a large amount of quenching stress inside the gear ring. Tempering is carried out in a short time, and sufficient tempering temperature and holding time are ensured to eliminate the stress inside the gear ring, making the microstructure inside the gear ring tend to be stable, and ensuring the dimensional stability and performance reliability of the parts.

[0015] Furthermore, a shot peening process and a painting process are sequentially arranged between the machining center process and the finish turning process.

[0016] Beneficial effects: Since the time of natural aging is 48 hours, setting the shot peening process and the painting process after the machining center process and before the finish turning process can perform non-machining on the gear ring within the natural aging time, saving machining time and avoiding time waste during the static period of the gear ring, thereby improving production efficiency.

[0017] Furthermore, the machining center process includes the machining of threaded holes, through holes, and pin holes on the end face of the gear ring.

[0018] Beneficial effects: If the hole machining is carried out before the quenching process, due to the existence of threaded holes or pin holes, etc., the wall thickness of the gear ring will be inconsistent everywhere, resulting in uneven heating rates at different parts of the gear ring, affecting the consistency of the hardened layer depth of the gear ring after quenching. In the present invention, the hole machining process on the end face of the gear ring is arranged to be machined after the induction quenching process, so as to ensure that the entire wall thickness of the gear ring is consistent during the induction quenching process, improve the effect of the gear ring after quenching, ensure that the metallographic structure evaluation is qualified, improve the uniformity of the hardened layer depth, and ensure the quenching quality of the gear ring.

[0019] Furthermore, the threaded holes and through holes are directly machined to the finished product size in the machining center process, and a margin is reserved during the machining of the pin holes.

[0020] Beneficial effects: Since the assembly accuracy requirements for threaded holes and through holes are relatively low, they can be directly machined to the finished product size, avoiding subsequent secondary machining and saving machining time, improving production efficiency. The function of the pin hole is to be used for high-precision assembly with the box body of the wind power gearbox in the future. Therefore, a margin is reserved to facilitate subsequent secondary reaming and boring machining, preventing the size of the pin hole from deforming after induction quenching and affecting the assembly tightness accuracy.

[0021] Furthermore, a gear grinding process and a magnetic particle flaw detection process are sequentially arranged after the finish turning process. In the gear grinding process, only the tooth surface is ground, and the tooth root is not ground. In the magnetic particle flaw detection process, only the tooth part is flaw detected.

[0022] Beneficial effects: The gear grinding process only grinds the tooth surface part and avoids the tooth root part, which can avoid generating grinding cracks or burns during grinding of the tooth root, and at the same time avoid the rapid wear of the grinding wheel caused by grinding the tooth root, ensuring the quality of the gear ring while improving the service life of the grinding wheel; while the magnetic particle flaw detection process only flaw detects the tooth part, which can confirm whether grinding cracks are generated during gear grinding, can avoid unnecessary detection of other non-critical parts of the gear, focus the flaw detection on the key stressed part of the tooth part, and can more specifically detect defects that may affect the performance and life of the gear. Compared with comprehensive flaw detection of the entire part, it can save detection time and cost, improve detection efficiency, and can also more accurately discover potential problems in the tooth part and take timely measures for repair or scrapping.

[0023] Furthermore, a rough milling tooth process and a finish milling tooth process are also provided before the induction hardening process. The rough milling tooth process is processed by using a milling cutter with the same pressure angle as the processed gear ring and a module difference of no more than 1 mm.

[0024] Beneficial effects: Borrowing the milling cutter can avoid using the same milling cutter for rough milling teeth and finish milling teeth, and avoid the situation where the milling cutter is not enough when rough milling and finish milling are carried out simultaneously, which may force the replacement of products or the purchase of multiple milling cutters, thus increasing the tool cost. For the production of large wind power gear rings, this can save huge economic costs; moreover, after the wind power gearbox is mass-produced, it will only be processed again when it needs to be replaced after-sales. Generally, there is an interval of several years between mass production and after-sales. During this period, the tools and inserts will be idle. Borrowing the milling cutter can consume the existing inventory inserts and avoid waste of inventory inserts. Description of the Drawings

[0025] Figure 1 Isometric view of the gear ring of the present invention;

[0026] Figure 2 is Figure 1 Isometric view of each tooth part of the gear ring in

[0027] Figure 3 is Figure 2 Cross-sectional view of each tooth part in Specific Embodiments

[0028] The following is a more detailed description through specific embodiments:

[0029] Embodiment 1

[0030] As Figures 1 to 3 shown, an induction hardening gear ring processing process includes the following steps:

[0031] S1 Incoming inspection and acceptance. This process includes ultrasonic flaw detection of the blank and inspection of the blank size. Ultrasonic flaw detection can promptly detect blank defects, and size inspection can detect out-of-tolerance blank sizes, avoiding out-of-tolerance machining allowances in subsequent processes.

[0032] S2 Rough milling of teeth. For the rough milling of teeth process, a milling cutter with the same pressure angle as the processed gear ring and a module difference of no more than 1 mm is borrowed for processing. For example, a gear ring with a module of M13 and a pressure angle of a22.5° can borrow a milling cutter with a module of M12.5 and a pressure angle of a22.5°. Borrowing the milling cutter can avoid using the same milling cutter for both rough milling and finish milling, and prevent the situation where the milling cutter is insufficient when rough milling and finish milling are carried out simultaneously, which may force the replacement of products or the purchase of multiple milling cutters, thus increasing the tool cost. This can save a huge economic cost for the production of large wind power gear rings. Moreover, after the wind power gearbox is mass-produced, it will only be processed again when replacement is needed after-sales. Generally, there is an interval of several years between mass production and after-sales. During this period, the tools and inserts will be idle. Borrowing the milling cutter can consume the existing inventory inserts and avoid waste of inventory inserts.

[0033] S3 Chamfering of tooth profile. Chamfer the edges of the tooth part of the gear ring after rough milling of teeth to prevent noise and damage to the meshing tooth surface caused by small bumps resulting in raised tooth surfaces.

[0034] S4 Quenching and tempering. Quenching and tempering treatment can maintain a certain hardness of the raw material while improving the toughness and strength of the material, greatly adjusting the performance and material quality of the steel, and enhancing the machining performance of the gear ring.

[0035] S5 Semi-finish turning. Perform external circle cutting on the gear ring after quenching and tempering. During semi-finish turning, the external circle of the gear ring is turned to the finished size, with a 2-mm allowance left on the outside diameter of the stop, and a 0.4-mm to 0.5-mm allowance left on the end face.

[0036] S6 Finish milling of teeth. Used for finish machining the tooth part of the gear ring after semi-finish turning. When finish milling teeth, a tooth surface allowance of 0.35 mm to 0.4 mm is left, and a milling cutter with root cutting is used. The finished root cutting amount is 0.2 mm to 0.4 mm; when grinding teeth with a root-cutting milling cutter, the tooth root is not ground, which can avoid grinding burns or cracks generated during tooth root grinding.

[0037] S7 Chamfering of tooth profile. Chamfer the edges of the tooth part of the gear ring after finish milling of teeth to prevent noise and damage to the meshing tooth surface caused by small bumps resulting in raised tooth surfaces, improve the meshing accuracy, reduce the impact during meshing transmission of the gear ring, and enhance the transmission stability.

[0038] S8 Induction hardening. This process includes a stress relief tempering process after the induction hardening treatment is completed. The interval between the induction hardening process and the stress relief tempering process is no more than 2 hours, the tempering temperature is not lower than 180°, and the tempering holding time is not less than 12 hours. After the induction hardening process, hardness testing is required. The hardness testing positions are three tooth parts evenly distributed along the circumference of the gear ring. For each tooth part, three positions, namely the upper, middle, and lower positions, are detected along the axial direction of the gear ring, as Figure 2 shown ( Figure 2Axonometric view of each tooth part), the middle position is the middle position of the tooth width, and the upper and lower positions are within 25 mm from the end face. The detection area at each position includes Figure 3 as shown in Figure 3 cross-sectional view of each tooth part), which are respectively at the tooth root fillet 1 and 4, at a distance of H / 3 from the tooth tip 3 and 6, and at a distance of 2H / 3 from the tooth tip 2 and 5. H is 0.5×(the diameter from the starting meshing point of the involute to the tooth top circle).

[0039] Since induction hardening will rapidly heat the surface of the gear ring to a high temperature of 800 degrees, the rapid heating method will cause a large temperature gradient between the surface and the core of the gear ring. Due to the principle of thermal expansion and contraction, the surface expands rapidly while the core lags behind relatively, resulting in large and concentrated residual thermal stress inside the gear ring. At the same time, mechanical processes such as turning, drilling, and gear cutting before induction hardening of the gear ring will also cause residual stress inside the gear ring. The stress concentration inside the material will cause cracks to appear during the installation and use of the gear ring. Under the action of cyclic loads, the cracks will gradually expand, ultimately leading to fatigue damage of the gear ring and reducing the service life of the gear ring. The stress relief tempering process adopted in the present invention has large quenching stress inside the gear ring after induction hardening. Tempering is carried out in a short time, and sufficient tempering temperature and holding time are ensured to eliminate the residual stress generated inside the gear ring during the mechanical processing before and after induction hardening, making the microstructure inside the gear ring tend to be stable, ensuring the dimensional stability and performance reliability of the parts, helping to reduce the deformation and crack generation of the gear ring, and thus improving the service life of the gear ring.

[0040] S9 magnetic particle flaw detection is used to detect defects such as cracks in the gear ring after induction hardening, facilitating rapid interception after the crack problem occurs and preventing defective products from flowing into the subsequent processes to improve the quality control ability.

[0041] S10 machining center, this process includes the processing of threaded holes, through holes and pin holes on the end face of the gear ring; and the threaded holes and through holes are directly processed to the finished product size in the machining center process, and a 2mm-3mm margin is reserved for the pin hole processing. This process is set after the induction quenching process. If the hole processing is performed before the quenching process, the existence of threaded holes or pin holes will lead to inconsistent wall thickness in various parts of the gear ring, making the heating rate of different parts of the gear ring uneven, affecting the uniform depth of the hardened layer of the gear ring after quenching. The present invention sets the hole processing process of the end face of the gear ring to be processed after the induction quenching process, so as to ensure that the entire wall thickness of the gear ring is consistent during the induction quenching process, so as to improve the induction quenching effect of the gear ring, improve the uniformity of the hardened layer depth, and ensure the quenching quality of the gear ring. In addition, since the assembly accuracy requirements for threaded holes and through holes are relatively low, they can be directly processed to the finished product size, avoiding subsequent secondary processing, saving processing time, and improving production efficiency. The function of the pin hole is to be used for subsequent high-precision assembly with the wind turbine gearbox body. Therefore, a margin is reserved to facilitate subsequent secondary hole expansion and reaming processing to prevent the pin hole size from being deformed after induction quenching and affecting the assembly accuracy.

[0042] S11 shot blasting removes oil stains, oxide layers and other impurities on the surface of the gear ring after induction quenching to improve the surface quality and service life of the gear.

[0043] S12 paint can prevent the gear ring surface from secondary contamination, moisture and oxidation after shot blasting by painting.

[0044] S13 natural aging, the natural aging time starts from the completion of the machining center process and ends before the start of the fine turning process, and the total time should be greater than 48 hours. The natural aging treatment is to let the gear ring stand still so that the internal stress of the gear ring is naturally and slowly released to eliminate the residual stress. It can improve the machining accuracy and stability of the end face and stop of the gear ring in the subsequent fine turning process, and improve the machining quality of the gear ring. The natural aging time starts from the completion of the machining center process and ends before the start of the fine turning process. The total time should be greater than 48 hours to fully release the stress in the gear ring, so as to further avoid the deformation of the gear ring and the generation of crack defects and ensure the life of the gear ring.

[0045] S14 finishing turning, the end face and outer circle of the gear ring are processed to the finished product size.

[0046] S15 gear grinding: in this process, only the tooth surface is ground, and the tooth root is not ground. The gear grinding process only grinds the tooth surface part and avoids the tooth root part, which can avoid grinding cracks or burns caused by grinding the tooth root, and avoid excessive wear of the grinding wheel caused by grinding the tooth root, ensuring the quality of the gear ring while increasing the life of the grinding wheel.

[0047] S16 Magnetic particle flaw detection. In the magnetic particle flaw detection process, only the tooth part is inspected. By only inspecting the tooth part in the magnetic particle flaw detection process, it is possible to confirm whether grinding cracks are generated during gear grinding, avoid unnecessary inspections of other non-critical parts of the gear, focus the flaw detection on this key stress-bearing part of the tooth, and be able to more specifically detect defects that may affect the performance and life of the gear. Compared with comprehensive flaw detection of the entire part, it can save detection time and cost, improve detection efficiency, and at the same time can more accurately discover potential problems in the tooth part and take timely measures for repair or scrapping.

[0048] S17 Burn detection, which is used to detect whether there are burn defects in the tooth part of the gear ring during gear grinding to improve the quality control ability.

[0049] S18 Combined pin fitting. Combined pin fitting is to assemble the gear ring and the housing and tighten them with bolts, and then use a radial drill to ream and finish reaming the pin holes. By machining after assembly, the positional accuracy of the pin holes of the gear ring and the housing can be guaranteed, the assembly accuracy can be ensured, and at the same time, the radial drill is used to complete the reaming and finish reaming processing, reducing the equipment usage requirements and saving costs.

[0050] S19 Inspection, which is to perform finished product size detection on the processed gear ring to ensure product quality.

[0051] The above are only embodiments of the present invention. The present invention is not limited to the fields involved in this embodiment. Common knowledge such as specific structures and characteristics known in the solution is not described in detail here. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several deformations and improvements can still be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application should be based on the content of its claims, and the specific implementation manners described in the specification can be used to explain the content of the claims.

Claims

1. An induction hardening gear ring processing process, characterized in that: The following steps are involved: Induction hardening process, magnetic particle inspection process, machining center process, finishing process; The induction hardening process includes a stress relief tempering process; After the machining center process, the gear ring needs to be subjected to natural aging treatment. The natural aging time starts from the completion of the machining center process and ends before the start of the fine turning process. The total time should be greater than 48 hours.

2. The induction hardening gear ring processing process according to claim 1, characterized in that: The interval between the induction quenching process and the stress relief tempering process shall not exceed 2 hours, the tempering temperature shall not be lower than 180°, and the tempering holding time shall not be less than 12 hours.

3. The induction hardening gear ring processing process according to claim 2 is characterized in that: A shot blasting process and a painting process are arranged in sequence between the machining center process and the finishing process.

4. The induction hardening gear ring processing process according to claim 3 is characterized in that: The machining center process includes the processing of threaded holes, through holes and pin holes on the end face of the gear ring.

5. The induction hardening gear ring processing process according to claim 4, characterized in that: The threaded holes and through holes are directly processed to the finished product size in the machining center process, and the pin holes are processed with a reserve margin.

6. The induction hardening gear ring processing process according to claim 5, characterized in that: After the finishing process, a gear grinding process and a magnetic particle flaw detection process are sequentially provided. In the gear grinding process, only the tooth surface is ground without grinding the tooth root. In the magnetic particle flaw detection process, only the tooth part is inspected.

Images