RU2451837C1 - Method of part cutting of gear wheel pump - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: method of part cutting of a gear wheel pump involves grinding of plate surfaces and internal, external surfaces and end planes of gear wheels. The plates and gear wheels are made of austenite steel. After the grinding, the plates and end planes of the gear wheels are polished that is ensured by placing the plates and gear wheels into patterns and pressed them to a lapping disk of one-lap lapping and polishing machine. The patterns are actuated to go around, and simultaneously the lapping disk having annular grooves on its surface rotates. From above, the disk is coated with an ultradispersed detonation diamond (UDDD) suspension of the grain size of 100 nm and less which gets into the annular grooves and is actuated by centrifugal force to move in a radial direction and thereby uniformly distributed in a space between the ground surfaces of the parts and the lapping disk. While pressing, the ultradispersed detonation diamonds are used to cut off micro-and nanoparticles of the materials from the ground surfaces of the parts thereafter used to fill with micro- and nanopores of the surfaces that is combined with surface plastic deformation of the ground surfaces with using the UDDD suspensions.

EFFECT: higher reliability and life of the parts of the gear wheel pump.

4 cl, 4 dwg

Description

The invention relates to mechanical engineering, in particular to the processing of gear pump parts with external gearing of gears, which can be used to supply chemically active liquid media to the consumer, as well as in spinning machines that form chemical fibers in a wet and dry-wet manner.

A known method of processing parts of gear metering pumps, including the performance of parts made of steel martensitic grade EP890-Ш with heat treatment of parts (hardening) to a hardness of HRC ≥ 56 (see copyright certificate SU No. 922316, class F04C 2/04, 04/23/1982).

The specified heat treatment improves the wear resistance of gear pump parts. However, the aforementioned steel is not corrosion-resistant, which leads to corrosion-mechanical wear of the pump tribological joints when reactive media are supplied. The tribo-conjugation of gears and gear-housing are especially corroded and worn, since the metal surfaces of these parts are constantly in contact during the operation of the pump. This leads to corrosion-mechanical and hydrogen wear of friction pairs and, as a result, to a change in the geometry of tribological conjugations. As a result, the gear pump, when pumping chemically active media, quickly loses its required characteristics.

Known methods of mechanical abrasive processing of various kinds of parts - polishing, sharpening, grinding, which are one of the stages of a typical technological process of superfinishing in the production of metal laser mirrors based on non-ferrous, ferrous metals and alloys, as well as non-metallic materials. In this case, free or bonded abrasives are used (micropowders of titanium and chromium carbide, cubic boron nitride, powders of diamond, aluminum oxide, etc.) (see A.D. Nikiforov et al., High technology for dimensional processing in mechanical engineering, textbook for universities, M., Higher School, 2007, 327 pp.).

However, studies have shown that a relatively large particle size of abrasives, including diamonds (more than 1 μm), which are part of grinding wheels, pastes and suspensions, does not allow roughness during mechanized abrasive treatment of austenitic stainless steels on finishing machines more than 12 ... Grade 13 (Ra 0.025 ... 0.012 microns), which, in turn, does not allow to increase the service life of parts of gear pumps when operating in chemically active environments.

Closest to the invention in technical essence and the achieved result is a method of machining parts of a gear pump, including grinding the surfaces of the plates and the inner, outer surfaces and end surfaces of the gears (see utility model patent RU No. 92919, class F04C 2/00, 10.04. 2010).

Polished tribo-mating surfaces can reduce friction losses. The grade 35 steel hardened for hardness 37-42 HRC and the grade 45 steel hardened for HRC 46-52, having sufficient hardness, indicated in the patent, having sufficient hardness, can increase wear resistance and, as a result, the service life when pumping liquid media with abrasive inclusions. However, these steels are not corrosion-resistant, which leads to corrosion-mechanical and hydrogen wear of tribological conjugations of the pump when reactive media are supplied. In addition, the need for hardening of pump parts leads to a complication and cost of the manufacturing process of pump parts, but it does not allow to achieve the required reliability and durability of the pump in chemically active environments.

The problem to which the invention is directed, is to simplify the manufacturing process of pump parts while increasing their operational characteristics, in particular wear resistance when working in chemically active environments.

The technical result consists in that an increase in the reliability and durability of the gear pump parts is achieved.

This problem is solved, and the technical result is achieved due to the fact that the method of processing gear pump parts includes grinding the surfaces of the plates and the inner, outer surfaces and the end planes of the gears, while the plates and gears are made of austenitic steel, after grinding the plates and the end surfaces of the gears they are carried out polishing, for which the plates and gears are inserted into the stencils and pressed to the lapping disk of a single-disk flat-lapping machine, while organizing the rotation of the stencil ov about its axis while rotating the lapping disk, on the surface of which annular grooves are made; a suspension of ultrafine diamonds (UDD) with a grain size of less than 100 nm is fed from above to the disk, which, after falling into the annular grooves under the action of centrifugal force, is moved in the radial direction and, thus, evenly distributed in the space between the polished surfaces of the parts and the finishing disk, at the same time, during the pressing process, ultrafine diamonds are cut from the polished surfaces of the parts of the micro- and nanoparticles of materials and they are filled with micro- and nanopores of the surfaces, and simultaneously superficial plastic deformation of polished surfaces with suspensions with UDD.

The rotation speed of the lapping disk is preferably 36 to 72 rpm.

The flow rate of the suspension to the lapping disc is preferably from 2 to 20 l / min.

The parts are pressed against a finishing disk, preferably with a pressure of from 0.5 to 1.0 bar.

In the course of the studies, it was found that in order to increase the surface roughness class of parts made of ductile metals, it is necessary to nano-polish products in suspensions based on ultrafine diamonds (UDD) with grain sizes less than 100 nm. In this case, UDDs perform the functions of both an ultrafine abrasive that removes nanoparticles of metal grains, fills micro- and nanopores of the metal surface, and a tool for plastic deformation of the surface, which contributes not only to increase the hardness of the surface layer, but also to increase the roughness class. At the same time, favorable compressive stresses arise in the surface layer, which leads to an increase in the fatigue strength and wear resistance of the product with boundary friction.

The basis of the developed method is the combination of nanoabrasive machining of “soft” plastic austenitic steels with a free abrasive (UDD with nanograin sizes of 80 ... 100 nm), which is part of the suspensions, with the surface plastic deformation of these parts with surface diamonds and thus creating a surface layer with increased physical -mechanical characteristics. The high hardness and large specific surface area of diamond nanopowders of the suspension and, consequently, the enormous amount of surface energy allow them to perform the functions of a surface-forming agent for nanoscale processing and at the same time serve as ideal “tools” for nanoabrasive machining and surface plastic deformation of the surface of gear pump parts made of austenitic steels.

Figure 1 shows a longitudinal section of a gear pump, the details of which are made in accordance with the described method of processing parts.

Figure 2 is a section aa in figure 1.

Figure 3 schematically shows the machined parts of the gear pump installed in the stencils when machining the end surfaces of the gears and the surfaces of the plates.

Figure 4 shows the profilogram of the surface of austenitic stainless steel processed by the described method.

The gear pump selected as an example contains two gears 1 and 2, each of which is made with polished inner 3 and outer 4 surfaces and end planes 5, and plates 6 with polished surfaces 7. Gears 1 and 2 and plates 6 are made of austenitic steel. The end surfaces 5 of each gear 1 and 2 and the surface 7 of the plates 6, facing the side of gears 1 and 2, are polished using a suspension based on ultrafine diamonds with grain sizes less than 100 nm on the lapping disk of a single-disk flat-grinding machine, when the stencils 8 rotate into which gears 1 and 2 or plates 6 are inserted around its axis while rotating the lapping disk 9, and thus, a more durable surface layer with a thickness of 12 to 20 nm and a hardness 3-3.5 times higher than the rest is formed on the parts material.

A method of processing parts of a gear pump includes grinding the surfaces of the plates 6 and the inner 3, the outer 4 surfaces and the face 5 of the plane of the gears 1 and 2. After the grinding of the plates 6 and gears 1 and 2, their end surfaces are polished, for which the plates 6 and gears 1 and 2 are inserted into the stencils 8 and press them to the lapping disk 9 of the single-disk flat-lapping machine, while organizing the rotation of the stencils 8 around its axis while rotating the lapping disk 9, on the surface of which annular channels are made 10. A suspension based on ultrafine diamonds (UDD) with a grain size of less than 100 nm is fed from above to the disk 9, which, after falling into the annular grooves 10, is radially displaced by centrifugal force and, thus, is evenly distributed in the space between the polished surfaces parts (plates 6 and gears 1 and 2) and a finishing disk 9. During the pressing process, ultrafine diamonds are cut from the polished surfaces of the parts of the micro- and nanoparticles of materials and filled with them micro- and nanopores to the surface d, and simultaneously carry out surface plastic deformation of polished surfaces with suspensions with UDD.

In the course of the study, it was found that the best results were achieved when the speed of the finishing disk 9 is from 36 to 72 rpm, the suspension flow to the finishing disk 9 is from 2 to 20 l / min and the parts are pressed to the finishing disk 9 with a pressure of 0, 5 to 1.0 bar.

During nanopolishing, two processes occur simultaneously. In the contact zone “part (1, 2 or 6) - lapping disk 9”, the process of grinding metal, carbides, oxides by millions of particles of abrasive - UDD occurs. Moreover, since the grain section of the protrusions of the metal surface is produced by nanodiamonds, the size of which is not more than 100 nm, grains are formed whose size is in the nanoscale range. These grains fill macro-, micro- and nanopores, thereby reducing the surface roughness and porosity. At the same time, there is a decrease in the size of metal grains located in the surface layer as a result of their wear during high-energy grinding in the process of nanopolishing, which leads to an increase in the strength of the surface layer.

At the same time, during the relative “lapping disk - part” rotational motion, millions of nanodiamonds with enormous surface energy are rolled during complex kinematic motion and, under the above pressure on the polished parts, create the effect of surface plastic deformation on them. Thus, the surface of the parts is “smoothed”, which leads to an even higher degree of lowering its porosity and roughness.

Due to these processes occurring simultaneously, a modified UDD layer of increased hardness is formed on the surface of the polished metal, which has strength characteristics of the material that differ from bulk properties. The size of this layer is in the range of 12 ... 20 nm. It was found that the minimum required layer thickness is 12 nm, which allows to increase the wear resistance and strength of the parts necessary for operation when pumping chemically active media. At the same time, it is inappropriate to increase the thickness of the deformed layer more than 20 nm, since in this case the increase in strength and wear resistance is negligible, while the deformation changes in the parts sharply increase compared to the initial values, which can lead to a deterioration in the performance of the gear pump.

Determination of the surface hardness of the gears of metering pumps, nano-polished with suspensions with UDD, the average size of which is 80 ... 100 nm, in comparison with the hardness of the surfaces of the gears polished with suspensions with diamond powders of a fraction of 2 ... 4 μm, was carried out on a scanning nanoscale hardness tester "NanoScan" developed by Federal State Technological University Institute of Superhard and New Carbon Materials, Troitsk. As a result, the following data were obtained:

- the hardness of the surface layer of 12X18H10T austenitic stainless steel subjected to nanopolishing with suspensions of UDD nanopowders is 230 ... 244 HV (HRC 19.2 ... 22), whereas the surface layer polished with ordinary powders is 176 ... 180 HV (HRC 6 ... 7) , i.e. hardness in the first case is 3 ... 3.5 times higher.

Figure 4 shows the profilogram of the surface of austenitic stainless steel processed by the described method. As follows from the profilogram, the roughness of the nanopolished surface is Ra 0.003 μm, which exceeds the highest roughness class 14 according to GOST 2789-73, equal to 0.008 μm. The measurements were carried out on a device for measuring the roughness of the model HOMMEL TESTER W55 (Germany).

The present invention can be used in the oil and gas, automotive, chemical and other industries for pumping various liquid, mainly aggressive environments.

Claims (4)

1. A method of processing parts of a gear pump, including grinding the surfaces of the plates and the inner, outer surfaces and the end surfaces of the gears, characterized in that the plates and gears are made of austenitic steel, after grinding the plates and the end surfaces of the gears, they are polished, for which the plates and gears inserted into the stencils and press them to the finishing disk of a single-disk flat-cutting machine, while organizing the rotation of the stencils around its axis while rotating the finishing disc A ka, on the surface of which annular grooves are made, a suspension based on ultrafine diamonds (UDD) with grain sizes less than 100 nm is fed from above to the disk, which, after falling into the annular grooves under the action of centrifugal force, is moved in the radial direction and, thus, evenly distributed the space between the polished surfaces of the parts and the finishing disk, while in the process of pressing, ultrafine diamonds are cut from the polished surfaces of the parts of the micro- and nanoparticles of materials and filled with them micro- and nanopores of surfaces and simultaneously conduct surface plastic deformation of polished surfaces with suspensions with UDD. 2. The method according to claim 1, characterized in that the rotation speed of the lapping disk is from 36 to 72 rpm. 3. The method according to claim 1, characterized in that the suspension flow to the lapping disk is from 2 to 20 l / min. 4. The method according to claim 1, characterized in that the parts are pressed against a lapping disk with a pressure of from 0.5 to 1.0 bar.

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