RU2614913C1 - Method for electric-spark alloying of hardened steel parts - Google Patents

Abstract

FIELD: electricity.

SUBSTANCE: in the method for electric-spark alloying of the hardened steel parts, dopant material transfer of the electrode-tool is carried out to the workpiece surface under the effect of the pulsed electric spark discharges between the electrode-tool connected to the DC source as anode and the workpiece as cathode. In the process of alloying, electrode-tool continuous contact is carried out with the part, and electric current supply to them is carried out so that 10≤j≤100, 10^-3≥t_ch≥10^-5, t_p>t_ch, where j - current density (kA/cm²), t_ch - current pulse duration (s), t_p - pause duration between the current pulses (s).

EFFECT: hardening the steel parts by electric-spark alloying, providing improved performance.

7 dwg, 1 tbl, 1 ex

Description

The invention relates to mechanical engineering, in particular to electrophysical processing methods for hardening hardened steel parts by electrospark alloying.

The prior art method for electrospark coating on metal surfaces, which consists in the fact that between the vibrating electrode-tool and the workpiece is excited by an electric discharge in a gaseous medium. In this case, a directed transfer of the material of the processing electrode (anode) to the workpiece (cathode) takes place and its diffusion coupling with the base material is carried out (USSR Author's Certificate No. 89933, 05/27/1943).

A disadvantage of the known method is that when applying coatings to heat-treated (hardened) parts, a tempering zone — a zone of reduced hardness — is formed under the hardened layer. This leads to the forcing of the hardened layer of the part during its operation and, as a consequence, to the rapid wear of the parts.

The closest to the claimed technical solution according to the technical essence and the achieved result - the prototype - is a method of electrospark alloying of hardened steel parts, which consists in transferring the alloying material of the electrode-tool to the surface of the part under the influence of electric spark discharges between the electrode-tool and the part connected to the electric current source in which electrospark (electroerosive) alloying is carried out in combination with ion nitriding, which is carried out before or after the alloying process for a time sufficient to saturate the metal with nitrogen to the depth of the heat-affected zone (Tarelnik VB Hardening of compressor parts by electroerosive alloying and ion nitriding // Chemical and Petroleum Engineering. 1996. No. 2, p. 77) .

The disadvantage of the prototype is the low productivity due to the introduction of an additional operation of ion nitriding. In addition, the process of ion nitriding requires the use of complex and expensive equipment, which ultimately increases both current and capital costs.

The objective of the invention is the exclusion of additional operations during hardening of hardened steel parts with spark spark alloying.

The technical result to which the invention is directed is to increase the hardening performance of hardened steel parts by electrospark alloying.

The problem is solved, and the claimed technical result is achieved in that in the method of electrospark alloying of hardened steel parts, which consists in transferring the alloying material of the electrode-tool to the surface of the part under the influence of pulsed electric spark discharges between the electrode-tool connected to the source of constant electric current as an anode , and as a cathode - a part, in the process of doping, a continuous contact of the electrode-tool with the part is carried out, and m of electric current is carried out so that 10≤j≤100, 10 ^-3 ≥t _ch ≥10 ^-5 , t _p > t _ch , where j is the current density (kA / cm ² ), t _ch is the duration of the current pulse (s ), t _p - the duration of the pause between current pulses (s).

The invention is illustrated by illustrations, which represent:

in FIG. 1 is a schematic diagram of an implementation of a method for hardening hardened steel parts with spark spark alloying;

in FIG. 2 is a graph of the microhardness of the part processed by the claimed method at various depths;

in FIG. 3 is a graph of the microhardness of the machined part at various depths at 10> j, 10 ^-3 ≥t _ch ≥10 ^-5 , t _p > t _ch ;

in FIG. 4 is a graph of the microhardness of the machined part at various depths for j> 100, 10 ^-3 ≥t _ch ≥10 ^-5 , t _p > t _ch ;

in FIG. 5 is a graph of the microhardness of the machined part at various depths at 10≤j≤100, 10 ^-3 ≤t _ch , t _p > t _ch ;

in FIG. 6 is a graph of the microhardness of the machined part at various depths at 10≤j≤100, 10 ^-5 ≥t _ch , t _p > t _ch ;

in FIG. 7 is a graph of the microhardness of the machined part at various depths at 10≤j≤100, 10 ^-3 ≥t _ch ≥10 ^-5 , t _p <t _ch .

The claimed method of electrospark alloying of hardened steel parts is as follows.

The tool electrode 1 is brought into contact with the workpiece 2 and moved along the workpiece using, for example, a standard machine feed system 3 controlled by a numerical control system 4 (CNC), while the contact of the tool electrode with the part is carried out continuously during the entire operation doping (continuous contact of the tool with the part is ensured by standard means, for example, similar to those used in electromechanical processing of electromagnetic radiation - http://mirprom.ru/public/elektromehanicheskaya-obrabotka.html-0). When this electrode tool 1 is connected to the positive pole of the DC source 5, and the workpiece 2 to the negative, in addition, the circuit includes an electric pulse generator 6 (GIT), which supplies electric current to the electrode tool 1 and the workpiece 2 with parameters: 10≤j≤100, 10 ^-3 ≥t _ch ≥10 ^-5 , t _p > t _ch , where j is the current density (kA / cm ² ), t _ch is the current pulse duration (s), t _p - the duration of the pause between current pulses (s).

During processing, the material of the electrode tool 1 is transferred from the anode (electrode tool 1) to the cathode (workpiece 2).

The indicated current parameters make it possible to realize contact electric microexplosion of the end surface of the electrode and high-intensity transfer of its material to the hardened surface. In this case, the microhardness of the machined part increases no worse than in the prototype, and the short duration of the process does not lead to tempering of the heat-treated (hardened) part, which is clearly presented in FIG. 2 and, as shown by experiments, is observed within the declared ranges.

Exit of parameters beyond the declared ranges makes processing impossible or significantly reduces its quality, namely:

- at 10> j, 10 ^-3 ≥t _ch ≥10 ^-5 , t _p > t _ch transfer of the electrode-tool material to the hardened surface is not observed, the microhardness of the machined part remains unchanged (see Fig. 3);

- at j> 100, 10 ^-3 ≥t _ch ≥10 ^-5 , t _p > t _{ch the} microexplosion of the end surface of the electrode is accompanied by spraying of the molten material of the electrode-tool, the transfer of material of the electrode-tool to the hardened surface becomes unstable, the microhardness of the machined part in depth changes stepwise both upward and downward from the original value (see Fig. 4);

- at 10≤j≤100, 10 ^-3 ≤t _ch , t _p > t _ch excessive current pulse duration leads to tempering of the heat-treated (hardened) part, which leads to a "failure" 7 of the microhardness of the machined part in depth (see Fig. 5);

- at 10≤j≤100, 10 ^-5 ≥t _ch , t _p > t _ch, due to the short duration of the current pulse, the transfer of the material of the electrode-tool to the hardened surface decreases sharply (exponentially), the microhardness of the machined part remains practically unchanged (see Fig. 6);

- at 10≤j≤100, 10 ^-3 ≥t _ch ≥10 ^-5 , t _p <t _{ch a} small pause between current pulses leads to tempering of the heat-treated (hardened) part, which leads to a "failure" of 7 microhardness of the processed part in depth (see Fig. 7).

An example implementation of the method.

Experiments were carried out on carbide alloying of the working surfaces of parts (disk mills for metalworking). The VK-8 hard alloy was used as the electrode material, the material of the workpieces was high-speed (hardened) P6M5 steel with an initial microhardness of HK 740 units. Processing modes and results are shown in the table below.

All experiments showed complete agreement between the results and the graph in FIG. 2 subject to the declared parameters J, t _ch and t _p ; the exit of at least one of these parameters beyond the declared ranges makes processing impossible or significantly reduces its quality.

Obviously, in the process of carbide alloying using the proposed method, tempering of the treated hardened parts is not observed, the microhardness of the treated parts monotonically increases towards the periphery. Moreover, the need for additional operations (ion nitriding) during hardening of hardened steel parts by electrospark alloying, as is the case in the prototype, is completely eliminated when at least not worse performance indicators are achieved.

The foregoing allows us to conclude that the task set - the exclusion of additional operations during hardening of hardened steel parts by electrospark alloying - has been solved, and the claimed technical result - increased productivity - has been achieved.

Analysis of the claimed technical solution for compliance with the conditions of patentability shows that the characteristics indicated in the independent claim are essential and interconnected with each other with the formation of a stable population, unknown at the priority date of the prior art of the necessary features, sufficient to obtain the desired synergistic (over-total) technical result.

Thus, the above information indicates the fulfillment of the following set of conditions when using the claimed technical solution:

- the object embodying the claimed technical solution, when it is implemented, relates to the field of mechanical engineering, in particular to electrophysical processing methods for hardening hardened steel parts with electrospark alloying;

- for the claimed object in the form as described in the independent claim, the possibility of its implementation with

using the above-described in the application or known from the prior art on the priority date of the means and methods;

- the object embodying the claimed technical solution, when implemented, is able to ensure the achievement of the technical result perceived by the applicant.

Therefore, the claimed subject matter meets the requirements of the patentability conditions of “novelty”, “inventive step” and “industrial applicability” under applicable law.

Claims (1)

The method of electric-spark alloying of hardened steel parts, including the transfer of alloying material of the electrode-tool to the surface of the part under the influence of pulsed electric spark discharges between the electrode used as an anode-tool and a component as a cathode, characterized in that the alloying process with the introduction of the electrode-tool in continuous contact with the part and the supply of electric current to them with parameters 10≤j≤100, 10 ^-3 ≥t _ch ≥10 ^-5 , t _p > t _ch , where j is the current density, kA / cm ² , t _ch is the duration of the current pulse, s, t _p is the duration of the pause between current pulses, s.

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