A method for machining an alloy steel oil pump rotor

Abstract

This invention discloses a machining method for an alloy steel oil pump rotor, comprising the following steps: material preparation – turning (rough machining of the workpiece) – heat treatment – ​​turning (rough machining of the outer circle and end face) – milling (rough machining of the internal teeth) – fitting – chemical heat treatment – ​​heat treatment – ​​grinding (semi-finish machining of the outer circle and end face) – grinding (finish machining of the outer circle and end face) – fitting – grinding (finish machining of the chamfer at the outer circle) – wire cutting (semi-finish machining of the internal teeth) – grinding (finish machining of the internal teeth) – grinding (finish machining of the chamfer at the internal teeth); during the machining process, appropriate and reasonable heat treatment is performed on the workpiece, which effectively eliminates the internal stress of the workpiece and stabilizes the workpiece dimensions. At the same time, the process operation flow is changed, making the machining process smoother, the operation method simpler, and the workpiece quality more stable.

Description

Technical Field

[0001] This invention relates to the field of machining alloy structure oil pump rotors, and in particular to a machining method for an alloy structure steel oil pump rotor. Background Technology

[0002] The rotary oil pump mainly consists of an inner rotor, an outer rotor, and an oil pump housing. It is a key component in the transmission, with the inner rotor driving the outer rotor to rotate within the oil pump housing. High precision is required for both the inner and outer rotors, with a dimensional accuracy of IT6, a surface roughness of Ra0.8, carburizing and quenching, and a surface hardness of 58–62 HRC.

[0003] The main processing method is as follows: forging - normalizing + tempering - turning (turning both ends and inner and outer circles, enlarging the outer circle) - boring (drilling and boring positioning holes) - wire cutting (rough cutting of inner teeth) - heat treatment (carbonitriding, without quenching) - turning (turning off the carburized layer on the outer circle) - heat treatment (quenching 58~62HRC) - grinding (fine grinding of both planes) - grinding (fine grinding of the outer circle) - wire cutting (slow wire cutting of inner teeth) - turning (turning the outer circle) - grinding (fine grinding of the outer circle) - clamping (removing burrs) - flaw detection (magnetic flaw detection to check for cracks) - warehousing.

[0004] Existing processing methods have the following shortcomings:

[0005] (1) After the internal teeth are finished, the outer circle still needs to be rough and fine machined, which has a certain impact on the accuracy of the internal teeth and increases the weight of raw materials and processing steps.

[0006] (2) The machining cost of internal gear cutting using slow wire EDM is high;

[0007] (3) Manual deburring results in inconsistent quality;

[0008] (4) Due to the large positioning error, the form and position tolerance of the workpiece is unstable. Summary of the Invention

[0009] To solve the above-mentioned technical problems, the present invention provides a method for machining an alloy structural steel oil pump rotor.

[0010] The present invention is achieved through the following technical solutions.

[0011] The present invention provides a method for machining an alloy steel oil pump rotor, comprising all of the following steps:

[0012] S1: Material preparation, selecting carburized alloy structural steel forgings;

[0013] S2: Machining, use a three-jaw chuck to clamp the outer circle, machine the end face and inner hole, machine a section of the outer circle, clamp the outer circle, machine the other end face, machine the outer circle, leave allowance for the end face, inner hole and outer circle;

[0014] S3: Heat treatment, full annealing;

[0015] S4: Machining, use a three-jaw chuck to clamp the outer circle, machine the end face and inner hole, clamp the inner hole, machine the other end face and outer circle, leave allowance for the end face, inner hole and outer circle;

[0016] S5: Milling, using a machining center, with the workpiece positioned and clamped by fixture I on the machine tool, using one end face and outer circle for positioning, first using drilling and reaming to machine the fillet at the tooth root, then rough milling the internal teeth, and finally finish milling the internal teeth;

[0017] S6: Fitting process to remove burrs;

[0018] S7: Chemical heat treatment, carburizing, quenching and tempering, to obtain a workpiece with a surface hardness of 58-62 HRC and a core hardness of 32-45 HRC;

[0019] S8: Heat treatment, artificial aging;

[0020] S9: Grinding process, using an external cylindrical grinding machine, using wide soft jaws to clamp the small inner teeth of the workpiece and close to one end face of the workpiece, grinding the outer circle and one end face of the workpiece;

[0021] S10: Grinding process, using a surface grinder, using the already ground end face as a reference, grinding the other end face;

[0022] S11: Fitting, deburring;

[0023] S12: Grinding process, using an external cylindrical grinder, with a wide soft jaw to clamp the outer circle and close to one end face of the workpiece, and chamfering at both ends of the outer circle;

[0024] S13: Wire EDM machining, using a fast wire EDM machine tool, using fixture II to position and clamp the workpiece, cut the internal teeth, and leave a allowance;

[0025] S14: Grinding process, using a vertical machining center, with the grinding head mounted on the machine tool spindle, and the workpiece positioned and clamped using fixture II, grinding internal teeth;

[0026] S15: Grinding: The grinding is performed using a vertical machining center. The grinding head is mounted on the machine tool spindle. The workpiece is positioned and clamped using fixture II. One end of the internal gear is chamfered, and the other end of the internal gear is chamfered using fixture II.

[0027] Preferably, during the S1 material preparation process, the forgings are forged according to the QJ500B-2014 standard and delivered in the normalized state.

[0028] Preferably, in step S2, the hard jaws of a three-jaw chuck clamp the outer circle of the blank, while the end face is corrected during clamping, one end face is machined, the thickness dimension is controlled, the inner hole is machined, the outer circle is machined, and the axial length of the outer circle is only about half of the total thickness.

[0029] Preferably, the soft jaws of the three-jaw chuck clamp the machined outer diameter and press against the machined end face. The thickness of the end face is controlled at 27±0.1mm, and the outer diameter is φ190mm. The outer diameter is allowed to be connected to the tool within the tolerance range.

[0030] Preferably, in step S5, the point where the fillet at the root of the workpiece is tangent to the arc near the two internal teeth is allowed to have a tool mark of less than or equal to 0.08 mm.

[0031] Preferably, in step S13, the fixture II consists of a positioning seat, a positioning plate, a cylindrical positioning pin I, a conical positioning pin, a cylindrical positioning pin II, and a pressure plate. The positioning holes on the positioning seat for mounting the cylindrical positioning pin I and the cylindrical positioning pin II are machined in combination with the positioning holes on the positioning plate. The positioning plate is fitted with the positioning hole of the conical positioning pin I. The three positioning holes are respectively machined to match the outer circles of the positioning holes of the cylindrical positioning pin I, the cylindrical positioning pin II, and the conical positioning pin I, ensuring a gap of 0.01mm to 0.015mm.

[0032] Preferably, the positioning seat is installed on the machine tool worktable. The plane of the positioning seat is aligned with the guide rail of the machine tool, and the parallelism is no greater than 0.02mm. The positioning hole of the positioning seat is located with a probe, and the center deviation is no greater than 0.02mm. The positioning seat is pressed tightly on the machine tool worktable, and the workpiece is installed. The cylindrical positioning pin I, the cylindrical positioning pin II, and the conical positioning pin I are respectively installed in the corresponding positioning holes to position the workpiece and determine the position of the positioning plate. The conical part of the conical positioning pin I is inserted into the tooth groove of the workpiece and has a zero-clearance fit with the tooth groove, thereby positioning the workpiece.

[0033] Use a pressure plate to clamp the workpiece, remove the tapered locating pin I, cylindrical locating pin I, cylindrical locating pin II and locating plate, and finish machine the internal teeth.

[0034] Preferably, during the grinding process in S14, the workpiece is positioned and clamped using fixture II, and the internal teeth are finely ground.

[0035] Preferably, during the grinding process in S15, one end of the grinding internal tooth is chamfered with a diameter of C0.3mm, and the other end of the grinding internal tooth is chamfered with a diameter of C0.3mm.

[0036] The beneficial effects of the present invention are as follows: 1. After rough machining of the outer circle, rough machining of the internal teeth is performed, and then finish machining of the outer circle and one end face is performed simultaneously. The outer circle and one end face are completed in one go through finish machining, ensuring the perpendicularity requirement between the outer circle and the end face, making the outer circle pass through a smaller error, and at the same time, it will not affect the accuracy of the internal teeth, thereby avoiding rework as much as possible.

[0037] 1. During the grinding of the internal teeth, fixture II is used to position the workpiece. The internal teeth are cut and ground through three finishing processes, and the positioning reference of the three finishing processes is unified. The clamping plate is also processed by a matching machining method, which reduces the manufacturing error of fixture II and ensures high workpiece positioning accuracy.

[0038] 2. During the processing of the workpiece, appropriate and reasonable heat treatment procedures are carried out to effectively eliminate internal stress and stabilize the dimensions of the workpiece, thereby minimizing the possibility of deformation during use.

[0039] 4. Using a fast wire EDM machine to cut the internal teeth accelerates the cutting speed. At the same time, the internal teeth are finely ground through grinding, which can effectively remove the burn layer on the tooth surface caused by EDM. The chamfering of sharp edges is also changed from manual chamfering to machine chamfering, and the chamfering size can be controlled more precisely, reducing errors. This makes the processing flow smoother, the operation method simple, and the workpiece quality stable, thereby reducing the processing cost by about 7%. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of the oil pump rotor to be processed according to the present invention;

[0041] Figure 2 yes Figure 1 Enlarged schematic diagram of section I;

[0042] Figure 3 This is a schematic diagram of the structure for rough machining of a workpiece according to the present invention;

[0043] Figure 4 This is a schematic diagram of the structure for semi-finishing the outer circle and end face of a workpiece according to the present invention;

[0044] Figure 5 This is a schematic diagram of the structure for rough machining of the internal teeth of a workpiece according to the present invention;

[0045] Figure 6 This is a schematic diagram of the structure for precision machining of the outer circle and one end face of the workpiece according to the present invention;

[0046] Figure 7 This is a schematic diagram of the structure for precision machining of the other end face of the workpiece according to the present invention;

[0047] Figure 8 This is a schematic diagram of the structure for precision machining of the chamfer at the outer circle of a workpiece according to the present invention;

[0048] Figure 9 yes Figure 8 Enlarged structural diagram of Part II;

[0049] Figure 10This is a schematic diagram of the structure for semi-finishing the internal teeth of a workpiece according to the present invention;

[0050] Figure 11 This is a schematic diagram of the structure for precision machining of the internal teeth of a workpiece according to the present invention;

[0051] Figure 12 This is a schematic diagram of the structure for precision machining of the chamfer at the internal teeth of a workpiece according to the present invention;

[0052] Figure 13 yes Figure 12 Enlarged structural diagram of Part III;

[0053] Figure 14 This is a schematic diagram of the structure of the fixture II as shown in this invention;

[0054] Explanation of reference numerals in the attached drawings: 141-Location seat; 142-Location plate; 143-Cylindrical locating pin I; 144-Conical locating pin I; 145-Cylindrical locating pin II; 146-Pressure plate; 147-Conical locating pin II. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0056] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0057] In this embodiment of the application, a method for processing an alloy structural steel oil pump rotor includes the following steps:

[0058] S1: Material preparation, refer to... Figure 1 It adopts alloy structural steel 20CrMnTi-GB / T3077-2015 and is forged according to II-QJ500B-2014.

[0059] S2: Reference Figure 3 Specifically, it is machined using a conventional horizontal lathe; the first step is to clamp the outer diameter of the blank with the hard jaws of a three-jaw chuck, and simultaneously correct the end face; turn one end face, controlling the thickness dimension, which is 27mm plus the allowance for the other end face, and turn the inner hole dimension. Outer diameter of the car The axial length of the outer circle is only about half of the total thickness.

[0060] The second step involves using the soft jaws of the three-jaw chuck to clamp the machined outer diameter, simultaneously bringing the machined end face close to the chuck; then machining the other end face, controlling the thickness to be 27±0.1mm, and machining the outer diameter. The outer diameter allows for tool insertion within tolerance ranges. This enables rough machining of the workpiece while controlling its dimensions within permissible error ranges.

[0061] S3: Heat treatment, which involves fully annealing the workpiece with machined outer diameter and end face. The heating temperature is 870℃±10℃, and the workpiece is cooled in the furnace to 150℃ and then air-cooled. This helps to refine the grains, eliminate structural defects and residual stress, and stabilize the workpiece dimensions to prepare for subsequent processing and quenching.

[0062] S4: Reference Figure 4 Specifically, it is machined using a conventional horizontal lathe; the first step is to clamp the outer diameter with the hard jaws of a three-jaw chuck, and press it against the end face, then machine one end face until it is finished, while ensuring that there is machining allowance on the other end face. Next, machine the inner hole, the inner hole dimension of which is... The second step involves clamping the machined inner hole with the soft jaws of a three-jaw chuck and pressing it against the machined end face. Then, machine the other end face, controlling the thickness to 24.2 ± 0.042 mm. Finally, machine the outer diameter, controlling its dimensions. Rough machining is performed on the outer circle and end face of the workpiece, and the rough machining of the outer circle and end face of the workpiece is completed.

[0063] S5: Milling, see reference Figure 5 Specifically, a vertical machining center is used for machining. Fixture I is mounted on the machine tool's worktable, ensuring its plane is parallel to one of the machine tool's guide rails. The positioning hole φD5 is calibrated, and the workpiece is positioned and clamped using fixture I. Using one end face and the outer circle for positioning, the workpiece's tooth root fillet is first machined using drilling and reaming, with a dimension of 26-R4.1mm. Then, the internal teeth are rough-milled with a rough milling cutter, followed by a finish milling cutter. The finish milling of the internal teeth with the finish milling cutter results in dimensions of φ163.2mm and 13-R13.4mm. A tool mark of no more than 0.08mm is allowed at the tangent point between the tooth root fillet and the two arcs, allowing for a margin. This completes the rough machining of the workpiece's internal teeth.

[0064] S6: Fitting process, removing burrs remaining after milling.

[0065] S7: Chemical heat treatment; carburizing temperature 920℃±10℃, carburizing medium: methanol 60~80 drops / min, kerosene 120~140 drops / min, carburizing time approximately 6.5h (specific time to be determined by sample testing), after carburizing, placed in a pit tank for cooling. Carburized layer depth 0.8mm~1.3mm, which is the machining allowance (0.4mm~0.5mm) + the final required carburized layer depth (0.4mm~0.8mm).

[0066] The quenching heating temperature is 820℃±10℃, and the holding time is determined according to the furnace loading method, furnace loading quantity and the effective thickness of the workpiece. Oil cooling is used, with an oil temperature of 20℃~60℃.

[0067] The tempering heating temperature is 160℃±10℃, and the holding time is determined according to the furnace loading method, furnace loading quantity and effective thickness of the workpiece. Air cooling is performed.

[0068] Obtaining a workpiece with a surface hardness of 58–62 HRC and a core hardness of 32–45 HRC helps to enhance the stability of the workpiece and minimize the risk of deformation.

[0069] S8: Heat treatment; artificial aging, heating temperature 150℃±10℃, holding time 6h~8h; in order to eliminate internal stress of the workpiece and stabilize its dimensions, and reduce deformation of the workpiece during processing and use.

[0070] S9: Grinding process, see reference. Figure 6 The machining process is performed using an external cylindrical grinder. Wide soft jaws are a common type of soft jaw used in production. The wide soft jaws clamp the small inner diameter teeth of the workpiece and press them against one end face. The outer diameter is then precision ground to a dimension of [missing value]. Grind the end face again to control its dimensions. This ensures that the form and position tolerances of the workpiece are within the control range.

[0071] S10: Grinding process, see reference. Figure 7 The surface grinder is used for machining. A wide, soft jaw is used to clamp the small internal toothed circle, and it is held close to one end face of the workpiece. Using the already ground end face as a reference, the other end face is precision ground, controlling the end face dimensions to be as follows: It also controls the form and position tolerances of the workpiece.

[0072] S11: Fitting, removing burrs remaining from the grinding process;

[0073] S12: Grinding process, see reference. Figure 8 and Figure 9 The outer diameter is machined using an external cylindrical grinding machine. The outer diameter is clamped with a wide soft jaw and pressed against one end face of the workpiece. A chamfer of C0.3mm is ground at one end of the outer diameter. The outer diameter is then clamped with a wide soft jaw and pressed against one end face of the workpiece. A chamfer of C0.3mm is ground at the other end of the outer diameter.

[0074] Through the above three grinding processes, the finishing of the outer circle and one end face of the workpiece can be completed in one clamping, ensuring the perpendicularity requirements of the outer circle and the end face. At the same time, it also unifies the positioning datum, reduces the manufacturing error of the fixture, and achieves high positioning accuracy.

[0075] S13: Wire EDM machining, see reference. Figure 14The workpiece is machined using a fast wire EDM machine and positioned and clamped using fixture II. Fixture II consists of a positioning seat 141, a positioning plate 142, cylindrical positioning pin I 143, tapered positioning pin 144, cylindrical positioning pin II 145, and a pressure plate 146. The positioning holes of cylindrical positioning pin I 143 and cylindrical positioning pin II 145 on the positioning seat 141 are combined with the positioning holes of the positioning plate 142 for machining. The positioning plate 142 is equipped with the positioning hole of tapered positioning pin I 144. The three positioning holes are respectively machined to fit the outer circles of cylindrical positioning pin I 143, cylindrical positioning pin II 145, and tapered positioning pin I 144, thereby realizing the assembly of cylindrical positioning pin I 143, cylindrical positioning pin II 145, and tapered positioning pin I 144 on the positioning seat 141 and the positioning plate 142.

[0076] The specific combination processing method is as follows: Install the positioning seat 141 on the machine tool workbench, calibrate the plane Pm deviation of the positioning seat 141 to be no greater than 0.005mm, calibrate the positioning hole φD14 of the positioning seat 141, and the deviation is no greater than 0.005mm; install the positioning plate 142 on the positioning seat 141 and press it tight, and then process the positioning holes φD141, φD142, and φD143 by drilling and boring, measure the values ​​of the three holes, and record them.

[0077] The specific machining method is as follows: according to the actual measured values ​​of the three positioning holes, grind the outer circles of the positioning pins I143, II145 and I144 to ensure a gap of 0.01mm to 0.015mm.

[0078] Reference Figure 10 During the clamping process of the workpiece by fixture II, the positioning seat 141 is installed on the machine tool worktable. The plane Pm of the positioning seat 141 is aligned with the first guide rail of the machine tool, and the parallelism is not greater than 0.02mm. The positioning hole φD10 of the positioning seat 141 is located with the center deviation not greater than 0.02mm. The positioning seat 141 is pressed tightly on the machine tool worktable, and the workpiece is installed.

[0079] Cylindrical locating pin I143, cylindrical locating pin II145, and tapered locating pin I144 are respectively installed in the corresponding locating holes φD141, φD142, and φD143 to locate the workpiece and determine the position of the locating plate 142. The conical part of the tapered locating pin I144 is inserted into the tooth groove of the workpiece with a zero-clearance fit, thereby locating the workpiece. The workpiece is pressed with the pressure plate 146, and the tapered locating pin I144, cylindrical locating pin I143, cylindrical locating pin II145, and locating plate 142 are removed. The internal teeth are semi-finished with dimensions of 26-R3.8mm, 13-R13.05mm, and φ163.9mm.

[0080] S14: Grinding process, see reference. Figure 11The machining is performed using a vertical machining center. The machine tool spindle is equipped with a grinding head, and the workpiece is positioned and clamped using fixture II. The positioning seat 141 is installed on the machine tool worktable. A dial indicator is used to calibrate the plane Pm of the positioning seat 141 to be parallel to one of the machine tool's guide rails, with a parallelism of no more than 0.01 mm. The positioning hole of the positioning seat 141 is located using a dial indicator, with a size of φ187.5 and a center deviation of no more than 0.01 mm. The positioning seat 141 is then pressed firmly onto the machine tool worktable, and the workpiece is mounted on it.

[0081] The tapered locating pin I144 is replaced with the tapered locating pin II147. The cylindrical locating pin I143, the cylindrical locating pin II145, and the tapered locating pin II147 are respectively installed in the corresponding locating holes φD141, φD142, and φD143 to locate the workpiece. The cylindrical locating pin I143 and the cylindrical locating pin II145 (with different outer diameters) determine the position of the locating plate 142. The conical part of the tapered locating pin II147 is inserted into the tooth groove of the workpiece and has a zero-clearance fit with the tooth groove, thereby locating the workpiece. The workpiece is pressed with the pressure plate 146. The tapered locating pin II147, the cylindrical locating pin I143, the cylindrical locating pin II145, and the locating plate 142 are removed, and the internal teeth of the workpiece are precision ground.

[0082] S15: Grinding process: Refer to Figure 12 and Figure 13 The machining is carried out using a vertical machining center. The machine tool spindle is equipped with a grinding head. The workpiece is positioned and clamped using fixture II. The workpiece is positioned by positioning seat 141, cylindrical positioning pin I 143, cylindrical positioning pin II 145 and tapered positioning pin II 147. Finally, the workpiece is pressed by pressure plate 146. The tapered positioning pin II 147, cylindrical positioning pin I 143, cylindrical positioning pin II 145 and positioning plate 142 are removed. The chamfer C0.3mm is finely ground at one end of the internal gear.

[0083] The workpiece is then positioned using positioning seat 141, cylindrical positioning pin I 143, cylindrical positioning pin II 145, and tapered positioning pin II 147. Finally, the workpiece is pressed down using pressure plate 146. The tapered positioning pin II 147, cylindrical positioning pin I 143, cylindrical positioning pin II 145, and positioning plate 142 are then removed, and the other end of the internal gear is chamfered at C0.3mm.

[0084] The internal teeth of the workpiece are semi-finished and finished sequentially through one wire EDM and two grinding processes. The workpiece is positioned and fixed using fixture II. The same positioning tools and methods are used in all finishing processes, which unifies the positioning datum of the three finishing processes. At the same time, the fixture is assembled using a matching machining method, which reduces the manufacturing error of fixture II and ensures high positioning accuracy. Grinding is also used to remove the burn layer on the tooth surface caused by wire EDM, which improves the performance. The chamfering of sharp edges is changed from manual chamfering to machine chamfering, and the chamfering size is controlled. The processing flow is more reasonable and the operation method is more convenient.

[0085] First, the outer diameter and end face of the workpiece are precision machined, and then the internal teeth of the workpiece are precision machined. Compared with the original technology, this method avoids damage to the internal teeth during the precision machining of the outer diameter and end face of the workpiece, thereby improving the finished product yield and minimizing the need for rework. At the same time, by incorporating a reasonable heat treatment process, the mechanical properties of the workpiece are guaranteed, reducing deformation during use and lowering the processing cost.

[0086] S16: Flaw detection, magnetic flaw detection, to check for cracks in the workpiece and ensure the pass rate of the finished workpiece.

[0087] S17: Warehousing.

[0088] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made under the concept of the present invention using the description and drawings of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for machining an alloy steel oil pump rotor, characterized in that, Includes all of the following steps: S1: Material preparation, selecting carburized alloy structural steel forgings; S2: Machining, use a three-jaw chuck to clamp the outer circle, machine the end face and inner hole, machine a section of the outer circle, clamp the outer circle, machine the other end face, machine the outer circle, leave allowance for the end face, inner hole and outer circle; S3: Heat treatment, full annealing; S4: Machining, use a three-jaw chuck to clamp the outer circle, machine the end face and inner hole, clamp the inner hole, machine the other end face and outer circle, leave allowance for the end face, inner hole and outer circle; S5: Milling, using a machining center, with the workpiece positioned and clamped by fixture I on the machine tool, using one end face and outer circle for positioning, first using drilling and reaming to machine the fillet at the tooth root, then rough milling the internal teeth, and finally finish milling the internal teeth; S6: Fitting process to remove burrs; S7: Chemical heat treatment, carburizing, quenching and tempering, to obtain a workpiece with a surface hardness of 58-62 HRC and a core hardness of 32-45 HRC; S8: Heat treatment, artificial aging; S9: Grinding process, using an external cylindrical grinding machine, using wide soft jaws to clamp the small inner teeth of the workpiece and close to one end face of the workpiece, grinding the outer circle and one end face of the workpiece; S10: Grinding process, using a surface grinder, using the already ground end face as a reference, grinding the other end face; S11: Fitting, deburring; S12: Grinding process, using an external cylindrical grinder, with a wide soft jaw to clamp the outer circle and close to one end face of the workpiece, and chamfering at both ends of the outer circle; S13: Wire EDM machining, using a fast wire EDM machine tool, using fixture II to position and clamp the workpiece, cut the internal teeth, and leave a allowance; S14: Grinding process, using a vertical machining center, with the grinding head mounted on the machine tool spindle, and the workpiece positioned and clamped using fixture II, grinding internal teeth; S15: Grinding: The grinding is performed using a vertical machining center. The grinding head is mounted on the machine tool spindle. The workpiece is positioned and clamped using fixture II. One end of the internal gear is chamfered, and the other end of the internal gear is chamfered using fixture II.

2. The machining method for an alloy structural steel oil pump rotor as described in claim 1, characterized in that: During the preparation of materials for S1, the forgings are forged according to the QJ500B-2014 standard and delivered in the normalized state.

3. The machining method for an alloy structural steel oil pump rotor as described in claim 1, characterized in that: In step S2, the hard jaws of a three-jaw chuck clamp the outer circle of the blank, while the end face is corrected during clamping. One end face is machined to control the thickness dimension, the inner hole is machined, and the outer circle is machined. The axial length of the outer circle is only about half of the total thickness.

4. The machining method for an alloy structural steel oil pump rotor as described in claim 1, characterized in that: In step S2, the soft jaws of the three-jaw chuck clamp the machined outer diameter and press against the machined end face. The end face is machined to control the thickness. The outer diameter is machined within tolerance.

5. The machining method for an alloy structural steel oil pump rotor as described in claim 1, characterized in that: In S5, the workpiece's tooth root fillet is allowed to have a tool mark of less than or equal to 0.08 mm at the point where it is tangent to the arc near the two internal teeth.

6. The machining method of an alloy structural steel oil pump rotor as described in claim 1, characterized in that: S13, the fixture II is composed of a positioning seat (141), a positioning plate (142), a cylindrical positioning pin I (143), a conical positioning pin (144), a cylindrical positioning pin II (145), and a pressure plate (146). The positioning holes of the cylindrical positioning pin I (143) and the cylindrical positioning pin II (145) on the positioning seat (141) are combined with the positioning holes of the positioning plate (142) for machining. The positioning plate (142) is equipped with the positioning hole of the conical positioning pin I (144). The three positioning holes are respectively machined to match the outer circles of the positioning holes of the cylindrical positioning pin I (143), the cylindrical positioning pin II (145), and the conical positioning pin I (144) to ensure a gap of 0.01mm to 0.015mm.

7. The machining method of an alloy structural steel oil pump rotor as described in claim 1, characterized in that: The positioning seat (141) is installed on the machine tool worktable. The plane of the positioning seat (141) is aligned with the guide rail of the machine tool, and the parallelism is not greater than 0.02mm. The positioning hole of the positioning seat (141) is located with a probe, and the center deviation is not greater than 0.02mm. The positioning seat (141) is pressed on the machine tool worktable. The workpiece is installed. The cylindrical positioning pin I (143), cylindrical positioning pin II (145) and conical positioning pin I (144) are respectively installed in the corresponding positioning holes to position the workpiece and determine the position of the positioning plate (142). The conical part of the conical positioning pin I (144) is inserted into the tooth groove of the workpiece and has a zero clearance fit with the tooth groove, thereby positioning the workpiece. Use the pressure plate (146) to press the workpiece, remove the tapered locating pin I (144), cylindrical locating pin I (143), cylindrical locating pin II (145) and locating plate (142), and finish machine the internal teeth.

8. The machining method of an alloy structural steel oil pump rotor as described in claim 1, characterized in that: During the grinding process in S14, the workpiece is positioned and clamped using fixture II, and the internal teeth are finely ground.

9. The machining method of an alloy structural steel oil pump rotor as described in claim 1, characterized in that: During the grinding process in S15, one end of the grinding internal tooth is chamfered with a diameter of C0.3mm, and the other end of the grinding internal tooth is chamfered with a diameter of C0.3mm.

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