RU2537411C2 - Hard-facing of part grooves - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to machine building and may be used in hard-facing of part groove inner surfaces. Container with current conducting balls is vibrated at 20-30 Hz to make said balls reciprocate through part grooves. Low voltage is applied to container case and processed part isolated therefrom. Weakly conducting fluid is fed into container for transfer of low voltage (4-8 V) between said balls.

EFFECT: uniform cold-hardening, ruled out micro cracks.

1 dwg, 1 ex

Description

The invention relates to the field of combined processing and can be used for finishing and hardening with conductive granules of the inner surfaces of the channels, for example, narrow through interscapular channels of the wheels of turbines with an external bandage, having unstable initial micro- and macrogeometry of the surface and uneven physical and mechanical properties of the surface layer of the material.

A known method of processing using a flow of conductive electrolyte and solid filler in the form of abrasive, conductive or electrically neutral granules for finishing and hardening surfaces remote from the electrode-tool [1]. Voltage is applied to the part and to the electrolyte and granule supply device. However, in this method, the granules in the electrolyte stream and due to constant collisions with each other significantly lose kinetic energy and do not provide constant electrical contact with the part for stable anodic dissolution of the surface layer of the material in order to align the microrelief of the treated surface.

A known method of vibration processing [2], which consists in forcing the working medium along the walls of the channels of the part under the action of vibration from the wide part of the interscapular channels. This method does not allow to process narrow channels in which special inserts cannot be placed that align the granules of the processing medium with respect to the walls of the channels.

The closest analogue of the claimed method is a method of vibration processing [3]. This processing method consists in periodically reciprocating (vibroextruding) the granular working medium through the interscapular channels of the part under conditions of low-frequency (20-30 Hz) vibration. This advancement is carried out under the influence of dynamic pressure created in the working medium alternately at the inlet and outlet of the interscapular channel, in accordance with the directions of its vibro-extrusion. During processing, the container with the workpiece and the working medium is notified of the oscillatory movement in the vertical plane. After each vibroextrusion cycle, container rotates 180 ° around the horizontal axis (alternating rotations). After each rotation, the container is fixed in vertical angular positions corresponding to the position of its axis and the main axis of the workpiece.

The main disadvantage of this method is the limited time of continuous processing due to the formation from periodic collisions of granules with a detail on the treated surface of a solid oxide layer that prevents further removal of the allowance. Constant (after 10-15 minutes of processing) updating of the processing granular medium and etching of the surfaces of the blade to remove oxides is required, which violates the microstructure of the surface layer of the material. Also, the absence of uniform local influences between the granular tool and the workpiece does not allow one to obtain a given stable hardening of the channel surface layer, smooth the surface microgeometry and completely remove the defective layer from previous technological operations, which shortens the life of the products.

The present invention is aimed at obtaining a uniform degree of hardening and the elimination of microdefects over the entire machined surface.

This is achieved by the fact that with the method of combined processing of channels, based on the periodic reciprocating advancement of the granular working medium through the interscapular channels of the part under conditions of low-frequency order of 20-30 Hz vibration, the processing process is carried out in a liquid low conductive medium with an electric field of 4-8 B, and low-voltage voltage is supplied directly to the device case and the workpiece isolated from the case.

The invention is illustrated in the drawing, which shows the processing diagram.

The method is carried out in the following sequence: part 1 is installed in a snap 2 using fixing bolts 3 on the connector line of the housing 4. The flow of current through the housing 4 of the container to the component 1 is eliminated by installing between it and the snap 2 dielectric spacers 5 and bushings 6. In the upper part of the housing 4 conductive granules are placed over part 1, filling the internal cavity of the housing 4 with a volume of 0.5-0.75. A direct current power source 8 is connected, connected to the part 1 and the housing 4. A positive voltage is applied to the part 1 through the snap-in 2, and a negative voltage is applied to the conductive granules 7 through the housing 4, thereby providing anodic dissolution of the surface of the part at the moment of collision with the granules. The granules 7 together with the housing 4 perform reciprocating movements in conditions of low-frequency vibration, moving along the channels of the part under the action of gravity, as a result of which the channel is processed. After each vibro-extrusion cycle, the container periodically rotates 180 ° around the horizontal axis. After each rotation, the container is fixed in vertical angular positions for a period of time sufficient for the granules to completely pass through the channels of the part. During processing, the device is continuously supplied with a slightly conductive liquid 9, for example, industrial water, for transmitting a low-voltage 4-8 V between granules.

With the proposed combined treatment, granules create a smoothed microrelief without microcrack concentrators due to mechanical action, form residual compressive stresses in the surface layer of the material of the part at a given degree of hardening, and the anodic dissolution of microprotrusions due to the electrochemical effect forms a stable roughness favorable for the operation of the part. The achievable change in roughness in this case depends on the rate of anodic dissolution at the microprotrusion site, which sharply increases at the moment of contact of the ball with the part due to an increase in the conductivity at the impact site by 1.2-1.3 times depending on the physical properties of the material of the part.

An example implementation of the method.

The interscapular channels of the turbine wheel are processed in the form of a disk with a diameter of 110 mm, having the form of tapering along the length of grooves of variable cross-section, made in the radial direction so that a bandage ring 10 mm wide remains on the periphery of the disk end. The cross section of such a groove is trapezoidal and has dimensions on one end of the disk - 3 × 5 × 12 mm, and on the other 3 × 7 × 12 mm, the channel length is 10 mm. The opening angle of the channel P = 30 °. All surfaces of the blades forming the channel are curved. The initial surface roughness of the groove R _a = 10 ... 20 microns. As the working medium, polished steel balls with a diameter of 1.5 mm are used (Material steel 95X18, hardness HRC-60 ... 62). Processing is carried out for 20 min with an oscillation frequency of 30 Hz and components of the oscillation amplitude: horizontal - 2.0 mm, vertical - 3.0 mm. The bulk volume of the working medium is 60% of the container. The maximum resonant value of the vertical component of the swing range of the container (when the vibrator is stopped) is not more than 5 mm. As a slightly conductive liquid, industrial water is used. Voltage on current leads 5 V.

The results of finishing hardening processing of the interscapular channels of the part are as follows:

- the parameter of surface roughness Ra, microns - 0.19-0.36;

- continuity (uniformity) of processing,% - 100;

- the deflection of the tuning samples in the simulator (an indicator of the effectiveness of their surface hardening), mm - 0.2-0.3, which corresponds to the degree of hardening of the surface layer - 5 ÷ 8%.

Using the method will expand the technological capabilities for finishing and hardening parts of the blade type, increase the productivity and quality of surface treatment of the interscapular channels, which will provide an increase in fatigue strength, improving their operational characteristics.

Information sources

1. Electrophysical and electrochemical methods of processing materials. In 2 vols. T.2 / Ed. V.P.Smolentseva // M .: Higher school., 1983. - 208 p.

2. Patent RU 2269406 C2 Russian Federation, IPC В24В 31/116. The method of vibration processing / V.P. Smolentsev, A.N. Nekrasov, A.V. Bondar // Bulletin of inventions. - 2006. - No. 4.

3. Patent RU 2173627 C2 Russian Federation, IPC 7 V 24 V 31/06. The method of vibration processing / G.A. Sukhochev, A.V. Bondar, A.V. Levchenko // Discovery. Inventions - 2001. - No. 26, - prototype.

Claims (1)

The method of hardening the inner surfaces of the channels of the part, including providing vibration with a frequency of 20-30 Hz of the container body containing a granular working medium for reciprocating movement of the latter through the channels of the part, characterized in that low voltage is applied to the body and to the workpiece that is isolated from cases, while conductive steel balls are used as a granular working medium, and a weakly conductive liquid in the form of process water for transmission is supplied to the container and between low voltage bulbs of 4-8 V.