CN117245354A - A technology for improving the anti-fatigue performance of oil pump gears - Google Patents

Abstract

The invention discloses a process for improving the anti-fatigue performance of oil pump gears, which is characterized in that: after rough machining, the oil pump gear parts are carburized/nitrided; the oil pump gear parts are subjected to semi-finish grinding; and the oil pump gear is pressed. Stress precision grinding; free abrasive finishing on the surface of the part. This invention adopts "compressive stress high-precision grinding technology + free finishing technology to maintain the accuracy level of parts + Barkhausen signal non-destructive testing of gear parts" to comprehensively ensure the final processing accuracy of aviation oil pump gears and improve various surface microscopic performance indicators of oil pump gears. Compared with similar gear parts for foreign civil aviation engines, the oil pump gears produced using this technology have high-precision geometric tolerances, surface roughness, surface residual compressive stress, surface microstructure, and gear profile edge quality, all reaching the same level.

Description

A technology for improving the anti-fatigue performance of oil pump gears

Technical field

The invention relates to the technical field of aviation gear production, in particular to a process for improving the anti-fatigue performance of aviation oil pump gears.

Background technique

The aviation oil pump gear is a key core component of the aviation fuel power system. The gear is used in high-speed, high-load, and high-pressure conditions. Therefore, the aviation oil pump gear has long life, high reliability, and high efficiency requirements. During the use of domestic aviation oil pump products, faults such as wear of oil pump gears and support bearings, and cracks in oil pump gears may occur from time to time. According to research, the gear dimensional accuracy, positioning accuracy, part surface quality, gear profile edge quality, gear surface residual compressive stress, etc. are lower than similar foreign products.

For many years, the processing of domestic aerospace product components has been dominated by "forming and manufacturing" technology that meets the requirements of design drawings such as shape, surface roughness, etc. The main criterion for obtaining products is the processing and forming accuracy of the parts, and the main criterion for whether the product is qualified or not. Not aware of the important factors affecting component life and their complexity. The United States issued the "Guidelines for the Surface Integrity Manufacturing of Machined Components" in 1971 and implemented it in the "Military Aircraft Safety Life Design Specifications", taking the lead in realizing "surface integrity manufacturing" of gears and other parts. Among the many factors that affect the fatigue strength or fatigue life of a structure, surface roughness, surface stress state and surface tissue structure are one of the most important factors. The current domestic aviation oil pump product life requirements have increased from the original hundreds of hours for second- and third-generation aircraft to thousands to tens of thousands of hours for fourth- and fifth-generation aircraft, as well as the tens of thousands of hours required for civil aviation oil pump products, using the existing "forming manufacturing" Gears manufactured using advanced technology can no longer meet the performance requirements of current aviation oil pump products.

Contents of the invention

The object of the present invention is to provide a process for improving the anti-fatigue performance of oil pump gears. The obtained aviation oil pump gear not only meets many high-precision technical requirements of "forming manufacturing", but also reduces the gear surface roughness, increases the gear surface compressive stress, refines the gear surface microstructure, and makes the gear profile edges smooth and continuous, meeting the requirements of the aviation oil pump length. Lifetime reliability usage requirements.

The technical solution of the present invention: a process for improving the anti-fatigue performance of oil pump gears,

Step 1. After rough machining, the oil pump gear parts are carburized/nitrided;

Step 2. Perform semi-finish grinding on the oil pump gear parts;

Step 3. Perform compressive stress precision grinding on the oil pump gear;

Step 4. Perform free abrasive finishing on the surface of the part.

According to the above-mentioned oil pump gear anti-fatigue performance improvement process, the shape and position tolerance of the oil pump gear parts processed by semi-precision grinding is 0.003~0.005mm. The shape and position tolerance includes verticality, cylindricity, coaxiality and flatness.

The above-mentioned anti-fatigue performance improvement process of oil pump gears and the compressive stress precision grinding process use ceramic alumina abrasive grinding wheels to perform precision grinding and micro-extrusion processing on gear parts. The shape and position tolerance of the processed oil pump gear parts reaches 0.002 ~0.003mm, the thickness tolerance is 0.003 mm, the surface roughness Ra0.08~0.12, and the residual compressive stress on the surface of the part reaches -500~-700 MPa.

The above-mentioned anti-fatigue performance improvement process of oil pump gears uses Barkhausen signals to detect grinding burns and surface integrity of oil pump gear parts after compressive stress precision grinding, and achieves 100% comprehensive inspection of the parts.

The above-mentioned anti-fatigue performance improvement process of oil pump gears and the finishing process is that the gear parts move planetarily in a circular trajectory at 1/3 of the depth of the abrasive material box, so that the free abrasive grains can maintain speed and pressure and pass through the oil pump gear parts. The oil pump gear parts rotate at a constant speed at the same time, so that all surfaces of the oil pump gear parts can be processed with free abrasive particles. The surface roughness of the oil pump gear parts is within Ra0.05, and all 0.003mm shape and position tolerances are maintained. The residual pressure on the surface of the parts The stress reaches -650~-1000 MPa.

Beneficial effects of the present invention: The present invention adopts "compressive stress high-precision grinding technology + free finishing technology to maintain the accuracy level of parts + Barkhausen signal non-destructive testing of gear parts" to comprehensively ensure the final machining accuracy of aviation oil pump gears and improve the various aspects of oil pump gears. Item surface microscopic performance indicators. The aviation oil pump gear can not only meet the high precision requirements of "forming processing", but also achieve the effect of reducing the surface roughness of the gear parts, making the gear surface have greater compressive stress, refining the microstructure of the gear surface, and smoothing the edges of the gear profile. , thus increasing the contact stiffness and contact area of the gear during operation of the aviation oil pump, increasing the load-bearing capacity, and reducing the friction and wear of the tooth surface, positioning surface and corresponding friction pair, thereby improving the fatigue resistance of the oil pump gear. Compared with similar gear parts for foreign civil aviation engines, the oil pump gears produced using this technology have high-precision geometric tolerances, surface roughness, surface residual compressive stress, surface microstructure, and gear profile edge quality, all reaching the same level. Compared with the prior art, the present invention has the following advantages:

①After the original grinding process, the gear positioning surface stress is -100~-150MPa. After the compressive stress precision grinding, the gear end face compressive stress reaches -500~-600MPa, and the gear cylindrical surface compressive stress is -600~-700MPa.

②The structure of the oil pump gear processed by this process is shown in Figure 7. After the free finishing process of the gear parts, the oil pump gear maintains the original multiple 0.003mm high-precision dimensional tolerances and geometric tolerances. The compressive stress on the gear surface increased by -100MPa, reaching the gear end face compressive stress of -650~-700MPa, and the gear cylindrical surface compressive stress was -900~-1000MPa, reaching a compressive stress level comparable to that of similar foreign gear parts. The surface roughness of the gear has stably reached Ra0.05, the surface microstructure has been refined (see the comparison of Figures 1-4 in the manual), and the edges of the gear profile are smooth and rounded (see the comparison of Figures 5 and 6 in the manual).

③The original process uses acid etching for sampling inspection of grinding burns and cracks. Parts after acid etching inspection are scrapped. Parts without acid etching inspection have certain risks of undetected defects. Using Barkhausen signals to detect oil pump gears eliminates the need to scrap parts and can also detect micro-defects on the surface of parts that cannot be observed with the naked eye. Test all parts to avoid the risk of failing to detect problematic parts during random inspections.

Description of drawings

Figure 1 is a microscopic morphology of the oil pump gear part of the present invention before smoothing.

Figure 2 is the microscopic morphology of the oil pump gear part of the present invention after finishing.

Figure 3 is the appearance of the oil pump gear part of the present invention before finishing.

Figure 4 is the appearance of the oil pump gear part of the present invention after finishing.

Figure 5 shows the profile of the tooth root before smoothing of the oil pump gear part of the present invention.

Figure 6 shows the profile of the tooth root after finishing of the oil pump gear part of the present invention.

Figure 7 is a schematic structural diagram of the oil pump gear parts of the present invention.

Reference signs:

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and examples, but this does not serve as a basis for limiting the present invention.

Embodiment of the present invention: a process for improving the anti-fatigue performance of oil pump gears,

Step 1. After rough machining, the oil pump gear parts are carburized/nitrided;

Step 2. Perform semi-finish grinding on the oil pump gear parts;

Step 3. Perform compressive stress precision grinding on the oil pump gear;

Step 4. Perform free abrasive finishing on the surface of the part.

Even better, the semi-precision grinding oil pump gear parts have a geometric tolerance of 0.003 to 0.005 mm, and the geometric tolerance includes verticality, cylindricity, coaxiality and flatness.

Even better, for the compressive stress precision grinding process, a ceramic alumina abrasive grinding wheel is used to perform precision grinding and micro-extrusion processing on the gear parts. The processed oil pump gear parts have a shape tolerance of 0.002~0.003mm and a thickness of The dimensional tolerance is 0.003 mm, the surface roughness Ra0.08~0.12, and the residual compressive stress on the surface of the part reaches -500~-700 MPa. According to the material and size of the oil pump gear parts, selecting a ceramic alumina abrasive grinding wheel with appropriate hardness and particle size so that the residual compressive stress on the surface of the part meets the requirements is one of the key factors in the fatigue resistance of the oil pump gear parts.

Even better, the Barkhausen signal is used to detect grinding burns and surface integrity of oil pump gear parts after pressure stress precision grinding, and achieve 100% comprehensive inspection of the parts. In addition to being able to detect gear parts Burns caused by abnormal grinding processes can also detect micro-defects on the surface of parts that cannot be observed with the naked eye, ensuring the surface integrity of gear parts.

Even better, in the finishing process, the gear parts move in a circular trajectory at 1/3 of the depth of the abrasive material box, so that the free abrasive grains can maintain speed and pressure and pass through the oil pump gear parts, and the oil pump gear parts move at a constant speed at the same time The rotation allows all surfaces of the oil pump gear parts to be processed with free abrasive grains in a balanced manner. The surface roughness of the oil pump gear parts is within Ra0.05, and all geometric tolerances of 0.003mm are maintained. The residual compressive stress on the surface of the parts reaches -650~ -1000MPa. This ensures that the surface of gear parts can receive extremely small and uniform free abrasive micro-cutting and polishing effects. The surface microtexture of gear parts is more uniform and dense, and the edges of the gear profile are smooth, uniform and rounded, further improving fatigue resistance.

Example 2. A process for improving the anti-fatigue performance of oil pump gears, including the following steps:

Step 1. After rough machining, the oil pump gear parts are carburized/nitrided;

Step 2. Perform semi-finish grinding on the oil pump gear parts;

Step 3. Perform compressive stress precision grinding on the oil pump gear;

Step 4. Perform free abrasive finishing on the surface of the part.

The requirements for semi-finishing grinding in step 2 are as follows (geometric tolerance 0.003~0.005mm)

Step 3. Compressive stress precision grinding

Equipment: Swiss Stutt S31

Grinding wheel: CS66A1802Ⅱ8PVB3

Gear cylindrical grinding adopts "oscillating plunge grinding". During the grinding process, the radial feed removes a small amount of allowance, and the grinding is repeated with oscillation at a distance "J" in the axial direction. The grinding parameters are:

B: 0.01mm (semi-finishing allowance)

C: 0.005mm (fine grinding allowance)

E: 0.025mm/min (semi-finishing feed)

F: 0.01mm/min (fine grinding feed)

The gear end face grinding uses a double bevel grinding wheel "end face grinding with oscillation", and after the grinding allowance is completed, polishing without allowance is performed.

B (semi-finishing allowance): 0.03mm

C (finishing allowance): 0.01mm

E (semi-finishing speed): 0.03mm/min

F (finishing speed): 0.01 mm/min

Q: 20.000 (stay time S)

Step 31. Barkhausen signal non-destructive testing

Equipment: Rollscan250

Workwear: Camscan100

Probe: 3 probe arms are respectively equipped with 1 cylindrical probe, 1 gear probe and 1 cylindrical end face probe.

Operation mode: The workpiece is fixed by the chuck, and the motor drives the workpiece to rotate. One probe is installed on each of the three probe arms, which can be adjusted left and right. The relative movement between the workpiece and the probe achieved by the tooling can greatly avoid measurement errors caused by manual labor, thus ensuring the accuracy and reliability of the measurement data.

Production of oil pump gear standard sample: Use acid etching to screen the gears without burns as standard samples. The Barkhausen signal data of the standard sample is the reference value.

Detection parameters: Magnetization voltage: 4V. Constant frequency: 125HZ.

Production and analysis of inspection data line graph: From the inspection data line graph, the data mutation points are the surface micro-defects caused by burns or other factors.

Step 4. Gear free abrasive finishing

Equipment: BJG-X400B free abrasive finishing equipment

The gear part moves in a circular trajectory at the 1/3 depth position of the abrasive material box, so that the free abrasive grains can pass through the oil pump gear part, and the oil pump gear part rotates at a constant speed at the same time. Processing parameters: Use X400 S3-1G grinding block, HA-PC grinding fluid, finishing for 30 minutes (15 minutes, turn around and clamp gear parts); spindle speed 147rpm, material box speed 55rpm.

Claims (5)

1. A process for improving the anti-fatigue performance of oil pump gears, which is characterized by: Step 1. After rough machining, the oil pump gear parts are carburized/nitrided; Step 2. Perform semi-finish grinding on the oil pump gear parts; Step 3. Perform compressive stress precision grinding on the oil pump gear; Step 4. Perform free abrasive finishing on the surface of the part. 2. The process for improving the anti-fatigue performance of oil pump gears according to claim 1, characterized in that: the shape and position tolerance of the oil pump gear parts processed by semi-precision grinding is 0.003~0.005mm, and the shape and position tolerance includes verticality, cylindricity, Coaxiality and flatness. 3. The anti-fatigue performance improvement process of oil pump gears according to claim 1, characterized in that: in the compressive stress precision grinding process, a ceramic alumina abrasive grinding wheel is selected to perform precision grinding and micro-extrusion processing on the gear parts. The processed oil pump gear parts have a shape tolerance of 0.002~0.003mm, a thickness tolerance of 0.003mm, a surface roughness of Ra0.08~0.12, and a residual compressive stress on the surface of the part of -500~-700MPa. 4. The anti-fatigue performance improvement process of oil pump gears according to claim 1, characterized in that: the Barkhausen signal is used to detect grinding burns and surface integrity of the oil pump gear parts after precision grinding under compressive stress. And achieve 100% comprehensive inspection of parts. 5. The process for improving the anti-fatigue performance of oil pump gears according to claim 1, characterized in that: the finishing process means that the gear parts move planetarily in a circular trajectory at the 1/3 depth position of the abrasive material box, so that the gear parts can be freely ground. The particles can maintain speed and pressure through the oil pump gear parts, and the oil pump gear parts rotate at a constant speed at the same time, so that each surface of the oil pump gear parts can be processed with free abrasive particles in a balanced manner. The surface roughness of the oil pump gear parts is within Ra0.05, and each surface is maintained The geometric tolerance is 0.003mm, and the residual compressive stress on the surface of the part reaches -650~-1000 MPa.