RU2840822C1 - Method of repair of positive-displacement hydraulic drive - Google Patents

Abstract

FIELD: performing operations.

SUBSTANCE: invention relates to machine building and repair of machine parts and may be used at machine building and repair enterprises. Method comprises hardening the cylinder block soldering working surface with a tin bronze electrode in manual mode on an electric spark installation with a pulse energy of 0.045 J, pulse supply frequency 1200 Hz and processing time of 2.5 min/cm² with subsequent mechanized finishing on grinding and polishing machine. Build-up on working surfaces of pistons and slide valve of housing of rear cover by electrode from spring steel in mechanized mode on electric spark installation with pulse energy of 10 J, pulse feed frequency 45 Hz, electrode longitudinal displacement 0.16 mm/min, disc electrode rotation peripheral speed 0.018 m/s, number of passes 1. Cylinder block bushing bore and rear cover bore for slide valve are reconditioned by machining by blind adjustable diamond reamers at precision machining tool. Built-up working surfaces of pistons and rear cover housing slide valve are ground at centreless grinder to produce clearance in joints between piston and cylinder block bushing of 20-40 mcm and that of slide valve and rear cover housing bore of 10-18 mcm.

EFFECT: improving the physical and mechanical properties of applied metal coatings on the working surfaces of restored parts through the use of new electrode materials and technological modes of electric spark machining.

1 cl, 1 tbl

Description

The invention relates to the fields of mechanical engineering and repair of machine parts and can be used in mechanical engineering and repair and technical enterprises.

A method for repairing the Eaton 6423-618/6433-113 series volumetric hydraulic drive (National Research Mordovian State University named after N.P. Ogarev, Russia) is known. It consists of finishing the steel distributor on a grinding and polishing machine, restoring the holes in the cylinder block bushings and the holes in the valve box housing for the spool valve. The soldering surface of the distributor is strengthened with a molybdenum electrode in manual mode on an electric spark installation with a pulse energy of 0.02 J, a pulse frequency of 1560 Hz and a processing time of 3 min/cm²with subsequent mechanized finishing on a grinding and polishing machine (RU No. 2805739, IPC B23Р 6/02, B22D 19/10, B24B 37/00, publ. 10/23/2023).

The disadvantages of the known method are the design differences of the main parts, namely the cylinder block (lack of bronze brazing), the presence of additional parts (distributor with bronze brazing and valve box body). The working surfaces of the parts to be restored have other materials and technological gaps. Therefore, the use of electrode materials and technological modes of this method is not possible.

The closest in technical essence to the claimed invention is a method for repairing a Sauer Danfoss series 90 volumetric hydraulic drive (OOO Technical Service, Russia), which consists in the fact that the brazed surface of the cylinder block is strengthened with a molybdenum electrode in manual mode by an electric spark installation under certain process modes, followed by mechanized finishing on a grinding and polishing machine together with a distributor, the surfaces of the pistons and the valve of the rear cover housing are welded with an electrode made of medium-carbon steel in a mechanized mode by an electric spark installation under certain process modes, the holes of the cylinder block bushings and the hole of the rear cover housing for the valve are restored by mechanical processing with blind adjustable diamond reamers on a machine for precision processing, the welded surfaces of the pistons and the valve of the rear cover housing are ground on a centerless grinding machine until technological gaps are achieved in the piston-cylinder block bushing hole and valve-rear cover housing hole connections (RU No. 2794352, IPC B22D 19/10, B23P 6/02, B24B 37/11, published 17.04.2023).

In the Linde HPV/HMF (Germany) volumetric hydraulic drive, in contrast to the prototype, other materials of the restored parts are used, which differ in properties, and the working surfaces of individual parts (piston, valve of the rear cover housing, cylinder block) have differences in dimensional design and technological gaps. Thus, the use of electrode materials and technological modes of electrospark machining presented in the prototype for repair of the foreign Linde HPV/HMF volumetric hydraulic drive does not seem possible.

The technical result consists in the formation of metal coatings on the working surfaces of restored parts with high physical and mechanical properties due to the use of new electrode materials and technological modes of electric spark processing.

The essence of the invention is that the method for repairing a volumetric hydraulic drive includes strengthening the surface of the brazing of the cylinder block on an electric spark installation in manual mode with subsequent mechanized finishing on a grinding and polishing machine together with a distributor, surfacing the surface of the pistons and the valve of the rear cover housing on an electric spark installation in mechanized mode, restoring the holes of the cylinder block bushings and the hole of the rear cover housing for the valve by mechanical processing with blind adjustable diamond reamers on a machine for precision processing, grinding the surfacing pistons and the valve of the rear cover housing on a centerless grinding machine. The brazed surface of the cylinder block is strengthened with an electrode made of tin bronze using an electric spark unit in manual mode at a pulse energy of 0.045 J, a pulse frequency of 1200 Hz and a processing time of 2.5 min/ ^cm2; a metal coating of spring steel is deposited on the surface of the pistons and the valve stem of the rear cover housing using an electric spark unit in mechanized mode, with a pulse energy of 10 J, a pulse frequency of 45 Hz, a longitudinal movement of the electrode of 0.16 mm/min, a peripheral speed of rotation of the disk electrode of 0.018 m/s, a number of passes of 1, and subsequent grinding ensures technological gaps in the piston-cylinder block bushing hole connections of 20-40 μm, and the valve stem-rear cover housing hole of 10-18 μm.

Table 1 shows the results of the study of deposited coatings.

The method of repairing volumetric hydraulic drives is carried out as follows. The working surface of the cylinder block brazing is strengthened with a tin bronze electrode using a BIG-5 electric spark installation in manual mode at a pulse energy of 0.045 J, a pulse frequency of 1200 Hz and a processing time of 2.5 min/cm ² . The strengthened working surface of the cylinder block brazing and the working surface of the distributor are finished on a grinding and polishing machine (3ShP-320) in a mechanized mode, at a load of 1.0 ... 1.3 kgf, a stroke length of the driver of 90 mm, a rotation frequency of the finishing plate of 120 rpm, until the roughness parameter of these surfaces is Ra 0.2. The working surfaces of the pistons and the valve of the rear cover housing are coated with a metal coating of spring steel using a BIG-5 electric spark unit in a mechanized mode, with a pulse energy of 10 J, a pulse frequency of 45 Hz, a longitudinal movement of the electrode of 0.16 mm/min, a peripheral speed of rotation of the disk electrode of 0.018 m/s, and a number of passes of 1. The worn holes in the cylinder block bushings and the hole in the rear cover housing for the valve are restored by mechanical treatment with blind adjustable diamond reamers on a precision machining machine (SPO-01) until traces of wear are removed and the roughness parameter of these surfaces is reached Ra 0.4. The welded working surfaces of the pistons and the valve stem of the rear cover housing are ground on a centerless grinding machine until the technological gaps in the piston-cylinder block bushing connection are 20-40 µm, the valve stem-rear cover housing opening are 10-18 µm, and the roughness parameter of these surfaces is Ra 0.1.

The selected electrode materials and modes of electric spark machining were obtained as a result of studies using single- and multifactorial experiments to determine (optimization parameters) the thickness, continuity and microhardness of deposited metal coatings. The BIG-5 unit was used as an electric spark generator in the experimental studies, which ensures the obtained modes of electric spark machining.

For comparison of the prototype and the proposed solution, Table 1 presents the parameters of the coatings obtained by the method of electric spark treatment on the BIG-5 installation during the restoration of worn parts of volumetric hydraulic drives.

As a result of hardening with a tin bronze electrode using a BIG-5 electric spark installation in manual mode, a coating up to 30 μm thick, 95…100% continuity and 170…174 HV hardness was obtained on the working surface of the cylinder block brazing, which is 1.47 times higher than the hardness of the base material. The hardness of the base material of the cylinder block brazing, which is BrOCS 4-7-5, is 115…120 HV. In the prototype, the parameters of the obtained coating on the working surface of the cylinder block brazing, which is BrOS 10-10 bronze, hardened with a molybdenum electrode, were: thickness 10…30 μm, continuity 90…100% and hardness 150…154, which is 1.42 times higher than the hardness of the base material, respectively. The hardness of the main material of the cylinder block brazing, having the material BrOS 10-10, is 105...110 HV.

As a result of surfacing with an electrode made of 60S2A spring steel using the BIG-5 electric spark installation in a mechanized mode, a metal coating with a thickness of 348…400 μm, a continuity of 90…95%, a hardness of 834…872 and 862…880 HV, respectively, was obtained on the working surfaces of pistons and spools, which is 1.38…1.35 times higher than the hardness of the base materials. The hardness of the base materials of the working surfaces of the 16KhGN piston is 610…625 HV and the 20HF spool is 627…660 HV, respectively.

In the prototype, the parameters of the obtained metal coating on the working surfaces of pistons and spools with an electrode made of medium-carbon steel 50KhFA were: thickness 283…391 µm, continuity 90…95%, hardness 824…867 and 855…885 HV, respectively, which is 1.35…1.36 times higher than the hardness of the base materials. The hardness of the base materials of the working surfaces of the 45Kh piston is 620…640 HV and the 30KhMA spool - 630…650 HV, respectively.

Operational tests of a batch of five sets of volumetric hydraulic drives restored using the proposed method showed that no failures of the second and third degree of complexity were detected.

The invention makes it possible to obtain high physical and mechanical properties of applied metal coatings on the working surfaces of restored parts due to the use of new electrode materials and technological modes of electric spark processing.

Table 1

Repair method Type of processing Detail (material) Electrode material Thickness of the applied layer h, µm Continuity of coating, % Hardness, HV Basics coatings Suggested Strengthening Brazing of cylinder block (CuSn2ZnPb DIN 17656 / Bronze BrOCS 4-7-5) Bronze BrOCS 4-7-5 15-30 95-100 115-120 170-174 Surfacing Piston (Steel 16NiCr4 AFNOR NF EN ISO / Steel 16ХГН) Steel 60S2A 348-400 90-95 610-625 834-872 Surfacing Spool (Steel 22CrV4 AFNOR NF EN ISO / Steel 20HF) Steel 60S2A 348-400 90-95 627-660 862-880 Prototype Strengthening Brazing of cylinder block (SnPbB z10 DIN 17656 / Bronze BrOS 10-10) Molybdenum Mo 10-30 95-100 105-110 150-154 Surfacing Piston (Steel 41Cr4 AFNOR NF EN 10083 / Steel 45X) Steel 50KhFA 283-391 90-95 620-640 824-867 Surfacing Spool (Steel 25CrMo4 EN / Steel 30ХМА) Steel 50KhFA 283-391 90-95 630-650 855-885

Claims (1)

A method for repairing a volumetric hydraulic drive, including hardening the brazed surface of a cylinder block on an electric spark installation in manual mode, followed by mechanized finishing on a grinding and polishing machine together with a distributor, surfacing the surface of the pistons and the valve of the rear cover housing on an electric spark installation in mechanized mode, restoring the holes in the cylinder block bushings and the hole in the rear cover housing for the valve by mechanical processing with blind adjustable diamond reamers on a machine for precision processing, grinding the hardened pistons and the valve of the rear cover housing on a centerless grinding machine, characterized in that the brazed surface of the cylinder block is hardened with a tin bronze electrode by an electric spark installation in manual mode at a pulse energy of 0.045 J, a pulse frequency of 1200 Hz and a processing time of 2.5 min/cm ² , a metal coating is deposited on the surface of the pistons and the valve of the rear cover housing from spring steel by an electric spark installation in a mechanized mode, with a pulse energy of 10 J, a pulse frequency of 45 Hz, a longitudinal movement of the electrode of 0.16 mm/min, a peripheral speed of rotation of the disk electrode of 0.018 m/s, a number of passes of 1, subsequent grinding ensures technological gaps in the connections of the piston - the opening of the cylinder block bushing of 20-40 μm, the valve - the opening of the rear cover housing of 10-18 μm.