A method for precision machining of a surface of a thrust face friction pair

Abstract

The application discloses a kind of thrust end face friction pair surface precision machining method, belong to friction pair processing field, plane rough grinding, plane fine grinding and polishing combined machining process are successively used to process thrust end face friction pair surface, wherein plane rough grinding and plane fine grinding use white corundum grinding wheel, and plane polishing uses cubic boron nitride grinding wheel.The application uses grinding wheel plane grinding and polishing combined machining process, reduces the roughness value of thrust end face, reduces surface microstructure stress concentration, obtains smooth and strengthened working surface, improves the carrying capacity of thrust end face, wear resistance, prolongs the working life of thrust end face friction pair.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of friction pair processing, in particular to a processing method of a thrust end face. BACKGROUND

[0002] In order to meet the requirements of the axial installation position of the gear and the wear resistance of the end face, a thrust piece structure is designed. The roughness of the friction surface of the thrust piece is required to be Rz1.6, and the perpendicularity of the inner hole is required to be 0.02, which is relatively strict. The thrust piece belongs to the friction pair part, and the roughness of the friction surface is required to be relatively strict. Since the friction pair is generally made of carburized steel, the surface hardness is relatively high (56-60HRC), so the above-mentioned part is mainly processed by grinding as the final processing method, because there are a large number of alloy carbides in the carburized layer, and the hardness of the alloy carbides is not much higher than that of the abrasive of the grinding wheel, and the grinding property of the carburized steel is poor, and cracks and burns are easily generated.

[0003] The existing artificial corundum abrasive cannot meet the roughness requirement, and the grain size of the grinding wheel is too fine to easily generate corrugation and burn, so the end face is processed by manual grinding. After plane grinding, the grinding agent is coated on the grinding plate for manual grinding. Grinding processing is a precision processing method in which abrasive (usually micron grade) is added to the surface of a rigid tool under a certain pressure, and the abrasive is removed from the surface of the workpiece by the relative sliding of the tool and the workpiece through the micro-cutting action of the abrasive. Since the abrasive is in a free state during grinding, the abrasive performs rolling and micro-cutting on the surface of the workpiece, and the generated grinding is discontinuous.

[0004] The existing manual grinding mainly has the following disadvantages:

[0005] 1. The operator is required to have certain skill level and work experience, and to adjust the pressure and grinding motion trajectory applied on the workpiece according to the test results;

[0006] 2. Manual grinding is not suitable for batch production, the quality is unstable, and the roughness is not easy to guarantee. SUMMARY

[0007] The technical problem to be solved by the present application is to provide a precision processing method for the surface of a thrust end face friction pair, which adopts a combination of plane grinding and polishing of a grinding wheel to reduce the roughness value of the thrust end face, reduce the stress concentration of the surface microstructure, obtain a smooth and strengthened working surface, improve the carrying capacity and wear resistance of the thrust end face, and prolong the service life of the thrust end face friction pair.

[0008] To solve the above technical problems, the technical scheme adopted by the present application is:

[0009] A method for precisely machining the surface of a thrust end face friction pair comprises the following steps: using a combination of rough plane grinding, fine plane grinding, and polishing to process the surface of the thrust end face friction pair; a white corundum grinding wheel is used for rough plane grinding and fine plane grinding, and a cubic boron nitride grinding wheel is used for plane polishing.

[0010] A further improvement of the technical solution of the present invention is that: a 46-mesh white corundum grinding wheel is used for plane rough grinding, a 100-mesh white corundum grinding wheel is used for plane fine grinding, and a CBN1000 cubic boron nitride grinding wheel is used for plane polishing. The combination of plane rough grinding, plane fine grinding and polishing is divided into three processing states: cutting state, semi-cutting state and mirror polishing state.

[0011] A further improvement of the technical solution of the present invention is that a 46-mesh white corundum grinding wheel is used in the plane rough grinding process, and the shape error of the plane after the previous process is corrected by plane rough grinding, leaving a 0.05mm allowance for the next process of fine grinding, the grinding wheel speed is 1100r / min, the axial feed amount is 25mm, and the grinding depth is 0.02mm.

[0012] A further improvement of the technical solution of the present invention is that a 100-mesh white corundum grinding wheel is used in the plane fine grinding process to improve the microscopic geometry of the plane, leaving a polishing allowance of 0.01 mm for the next process, a grinding wheel speed of 1100 r / min, an axial feed of 22 mm, and a grinding depth of 0.01 mm.

[0013] A further improvement of the technical solution of the present invention is that the surface roughness after fine grinding is Rz2.5.

[0014] A further improvement of the technical solution of the present invention is that a CBN1000 cubic boron nitride grinding wheel is used in the plane polishing process, and the fine grinding surface can be further smoothed by plane extrusion polishing to reach the mirror surface standard. The grinding wheel speed is 1400 r / min, the axial feed is 20 mm, and the grinding depth is 0.002 mm.

[0015] A further improvement of the technical solution of the present invention is that the plane roughness after plane polishing is Rz1.6.

[0016] A further improvement of the technical solution of the present invention is that when the white corundum grinding wheel is being ground, a diamond pen is used to feed the grinding wheel axially to dress the grinding wheel to a cutting height equal to a micro-edge. When dressing the grinding wheel, the radial feed amount of the diamond pen is 0.002 mm.

[0017] Due to the adoption of the above technical solution, the technical advancements achieved by the present invention are:

[0018] The present application adopts the combined processing technology of plane grinding (rough grinding and fine grinding) and polishing, and reasonably sets the main process parameters such as the grinding wheel rotating speed, axial feed amount and grinding depth of the fine grinding and polishing processes. The wave peak of the processed surface is changed to a fine and smooth form, the micro plasticity of the abrasive grain is mainly used, the plane is smoothed, a fine and smooth surface with high fatigue strength is obtained, the load-carrying capacity and wear resistance of the thrust end surface are significantly improved, and the development of high-power, high-explosion pressure and high-reliability diesel engine technology is promoted.

[0019] The present application can effectively avoid the surface defects of traditional plane grinding processing, and the final process cutting mode is changed from abrasive grain scratching to extrusion polishing, thereby changing the microstructure form of the surface of the friction pair, obviously eliminating the rough edges and corners of the grinding surface microstructure, making the form fine and smooth, effectively reducing the surface roughness value, significantly improving the micro working performance, enhancing the load-carrying capacity of the surface of the friction pair, and effectively avoiding the wear of the friction pair.

[0020] The surface roughness value of the present application is low, which is beneficial to the establishment of oil film, improves the wear resistance of the surface of the friction pair, and prolongs the service life of the friction pair. DETAILED DESCRIPTION

[0021] The present application will be further described in detail in combination with examples:

[0022] A thrust end surface friction pair surface precision machining method, plane rough grinding, plane fine grinding and polishing combined machining process are used in sequence to process the thrust end surface friction pair surface, the wave peak of the processed surface is changed to a fine and smooth form, the micro plasticity of the abrasive grain is mainly used, the plane is smoothed, a fine and smooth surface with high fatigue strength is obtained, the load-carrying capacity and wear resistance of the thrust end surface are significantly improved, and the development of high-power, high-explosion pressure and high-reliability diesel engine technology is promoted.

[0023] 1. Principle description:

[0024] Through the subdivision of plane rough grinding, plane fine grinding and polishing process, the appropriate combination of plane grinding and polishing wheel characteristics, the reasonable matching of main process parameters such as grinding wheel rotating speed, axial feed amount and grinding depth, the surface reaching mirror standard and strengthened wear-resistant surface is finally obtained.

[0025] 2. Detailed process:

[0026] (1) Plane rough grinding

[0027] Plane rough grinding is a process that reduces the plane grinding time to the minimum. In this process, 46 mesh white corundum grinding wheel is used to correct the shape error of the plane after the previous process, form a certain flatness, and leave a margin of 0.05mm for the fine grinding of the next process.

[0028] Main process parameters setting of rough grinding:

[0029] Grinding wheel speed 1100 r / min, axial feed 25 mm, grinding depth 0.02 mm.

[0030] (2) Fine grinding of plane

[0031] Fine grinding of plane is an important process to form the expected plane roughness. In this process, 100 mesh white corundum grinding wheel is used to further improve the micro-geometric morphology of the plane, so as to lay a good foundation for the subsequent polishing process to obtain mirror standard roughness, and leave a polishing allowance of 0.01 mm for the next process.

[0032] Main process parameters of fine grinding:

[0033] Grinding wheel speed 1100 r / min, axial feed 22 mm, grinding depth 0.01 mm.

[0034] Plane roughness parameters after fine grinding: Rz 2.5.

[0035] (3) Plane polishing

[0036] Plane polishing is the key process to finally obtain mirror standard roughness. In this process, CBN1000 cubic boron nitride grinding wheel is used, and plane extrusion polishing can further finish the fine grinding plane to achieve mirror standard and obtain fine and reinforced roughness surface.

[0037] Cubic boron nitride grinding wheel is very beneficial to reducing roughness parameter value. Such grinding wheel works with dull abrasive particles for a long time, which can polish the surface in addition to cutting. The characteristics of the grinding wheel are high hardness, good wear resistance, and strong combination of abrasive particles and binder. The reduction process of cubic boron nitride abrasive particles is faster than the grinding wheel being ground, so the distance of the binder from the cutting surface is reduced, the contact area with the processed material is increased, and the extrusion polishing effect of the binder is enhanced, thereby improving the surface quality characteristics.

[0038] Main process parameters of extrusion polishing:

[0039] Grinding wheel speed 1400 r / min, axial feed 20 mm, grinding depth 0.002 mm.

[0040] Plane roughness parameters after fine grinding: Rz 1.6.

[0041] (4) Dressing of grinding wheel

[0042] The dressing of white corundum grinding wheel uses diamond pen to dress the grinding wheel along the axial feed to dress the grinding wheel into micro-blades and other cutting heights. When dressing the grinding wheel, the radial feed of the diamond pen is 0.002 mm.

[0043] 3. Analysis of plane grinding and polishing combined machining mechanism

[0044] The combined machining mechanism of plane grinding and polishing is very complex, but it can be divided into three machining states, i.e. cutting state, semi-cutting state and mirror polishing state.

[0045] In the rough grinding cutting state, the cutting edge of the abrasive grain is sharp, the pores on the grinding wheel surface are not blocked, and the ground surface has numerous obvious cutting marks and is not glossy.

[0046] In the fine grinding semi-cutting state, the fallen abrasive grains and the chips block some pores on the grinding wheel surface, and the cutting edge of some abrasive grains begins to blunt, thus reducing the cutting ability of the grinding wheel. The blunt abrasive grains scratch the workpiece surface. However, due to the falling of some abrasive grains, some new abrasive grains are exposed on the grinding wheel surface, and their new cutting edges participate in the cutting. Thus, the cutting marks on the machined surface are shallower and have a darker gloss.

[0047] In the mirror polishing machining state, the pores on the grinding wheel surface are blocked, and there is no trace of abrasive grain falling. The grinding wheel surface becomes very smooth. At this time, the blunt abrasive grains polish the workpiece surface, and the machined surface has no cutting marks, reaching the mirror standard.

[0048] The test results prove that the process parameters such as grinding wheel speed, axial feed amount and grinding depth have a great influence on the plane grinding and polishing machining state. If the grinding depth is too small, in the cutting state, only part of the "peaks" of the surface roughness can be cut, and after entering the semi-cutting state, the cutting effect of the grinding wheel is weakened and it has no ability to cut the remaining "peaks" of the surface roughness, thus leaving the machining marks of the previous step on the workpiece surface. On the contrary, if the grinding depth is too large, after cutting the "peaks" on the surface, the abrasive grains of the grinding wheel still have cutting effect until the machining allowance is cut off, and the workpiece surface still cannot reach the mirror roughness. Only when the cutting depth is selected at a suitable value, the machining state will automatically change from the cutting state to the semi-cutting state, and then to the mirror polishing state, so that the machined surface can reach the mirror roughness standard.

Claims

1. A method for precision machining the surface of a thrust end face friction pair, characterized by: The surface of the thrust end face friction pair was processed by a combination of plane rough grinding, plane fine grinding and polishing. A 46-mesh white corundum grinding wheel was used for plane rough grinding. The shape error of the plane after the previous processing was corrected through plane rough grinding, and a 0.05mm allowance was given to the next process of fine grinding. The grinding wheel speed was 1100r / min, the axial feed was 25mm, and the grinding depth was 0.02mm. A 100-mesh white corundum grinding wheel was used for plane fine grinding. The micro-geometry of the plane was improved through plane fine grinding. A 0.01mm allowance was given to the next process of polishing. The grinding wheel speed was 1100r / min, the axial feed was 22mm, the grinding depth was 0.01mm, and the plane roughness after fine grinding was Rz2.

5. A CBN1000 cubic boron nitride grinding wheel was used for plane polishing. The fine-ground plane could be further smoothed through plane extrusion polishing. The grinding wheel speed was 1400r / min, the axial feed was 20mm, the grinding depth was 0.002mm, and the plane roughness after polishing was Rz1.

6.

2. A method for precision machining of the surface of a thrust end face friction pair according to claim 1, characterized in that: The combination of plane rough grinding, plane fine grinding and polishing is divided into three processing states: cutting state, semi-cutting state and mirror polishing state.

3. The method for precision machining the surface of a thrust end face friction pair according to claim 1, characterized in that: When the white corundum grinding wheel is being dressed, a diamond pen is used to feed the grinding wheel axially to dress the grinding wheel to a cutting height such as a micro-edge. When dressing the grinding wheel, the radial feed amount of the diamond pen is 0.002mm.