RU2784636C1 - Method for cleaning iron electrode surface from oxides - Google Patents

Abstract

FIELD: physical properties study.

SUBSTANCE: invention relates to the study of the physical properties of matter, in particular to the study of processes in plasma and in gas-discharge devices. Method for cleaning oxides of an area of the surface of an iron electrode in an arc pulsed discharge includes placing the electrode to be cleaned at a fixed distance from another electrode with a thin wire fixed on it, which excludes spontaneous ignition of the discharge and provides conditions for an avalanche breakdown of the discharge gap that occurs when vapors of an evaporating wire are present in the air. wetting the area of the electrode to be cleaned with liquid in the zone of contact with the wire attached to the other electrode, ensuring the creation of electrical conductivity in the oxide layer of the electrode being cleaned, voltage is applied to the electrode with a wire fixed on it, followed by the wire touching the moistened surface of the electrode being cleaned, the explosion of the wire as a result of a short circuit with its evaporation and the formation of a local high temperature area on the surface of the electrode being cleaned in the moistened zone of contact with the wire, inside which moisture evaporates and evaporates layer of oxides.

EFFECT: simplification and acceleration of the technology for cleaning iron from oxides.

5 cl, 2 dwg

Description

Technical field

The claimed invention relates to the field of studying the physical properties of a substance, in particular, to studying processes in plasma and in gas-discharge devices, in which voltage is applied between the anode and cathode at a fixed distance between them. The resulting current melts and evaporates a thin wire, which is placed between the electrodes, in contact with them. The effect achieved in the invention makes it possible to obtain oxide-free areas of the iron surface on rusty electrode surfaces. The invention can find application in engineering and scientific research, with the introduction of new technologies in electronics and microelectronics.

State of the art

Rust, scale and other oxides on the metal surface can be removed in various ways:

- chemical (etching with dilute acids);

- thermal (methods of flame treatment of metal);

- mechanical (on metal-cutting machines, abrasive tools, steel brushes, etc.).

Thus, a METHOD FOR CLEANING A SURFACE FROM RUST (RF patent No. 2361708) is known from the prior art, which is used before the start of welding and includes thermal exposure and mechanical surface treatment, while before thermal exposure, a thermite composition is applied to the cleaned metal surface with a layer thickness of 1.5-4 .0 mm and initiate its combustion.

This method requires sequential execution of several operations, which affects the speed of its implementation. The disadvantages of this method of cleaning can also be attributed to insufficient quality, non-environmental processes.

A METHOD OF ELECTRIC ARC VACUUM-GRAVITATIONAL CLEANING OF LONG-DIMENSIONAL PRODUCTS is known (RF patent No. 2116848), according to which the product is exposed to a stable arc discharge, and particles of pollution (scale, rust) separated from it are affected by gravitational forces.

The disadvantages of the known cleaning method include the mandatory presence of long products and prolonged exposure to an arc discharge, as well as the need for a vacuum to implement the method, which greatly complicates the possibility of its application.

A METHOD FOR ELECTRIC ARC CLEANING OF THE SURFACE OF METAL PRODUCTS (RF patent No. 2347010) is known, including the creation of a discharged, protective or reducing environment between at least part of the product and one electrode, excitation of an electric discharge by a power source and treatment of the product with cathode discharge spots, while on the treated the surface is preliminarily applied with alkali, alkaline earth or rare earth metals, or their chemical compounds.

This method seems to be extremely unecological as a result of applying alkaline, alkaline earth and other chemical compounds to the electrode surface.

A METHOD FOR VACUUM-ARC CLEANING OF WIRE AND A DEVICE FOR ITS IMPLEMENTATION is known (RF patent No. current source, excitation between the wire and the electrode of an arc discharge in vacuum and winding of the cleaned wire, while the wire to be cleaned after welding the ends supplied in series for cleaning the coils is passed through a scale breaker, a container with viscous oil, a series of electrodes connected to the current source, and wire cooling units, and a container with viscous oil is placed in front of the inlet seal, and the cleaned wire is wound inside the vacuum chamber.

The disadvantages of this method include the multi-stage nature of the method, which greatly complicates it, the need to use a vacuum, a scale breaker, and a container with viscous oil.

Thus, the technical problem solved by the claimed invention lies in the need to overcome the disadvantages inherent in the analogues of the invention by creating a method for cleaning oxides from a local area of the surface of rust-coated iron in an arc pulsed discharge during an explosion of a wire placed between the electrodes.

Brief summary of the invention

The technical result achieved as a result of the application of the claimed invention is the simplification and acceleration of the technology for cleaning iron from oxides. The method does not require long-term preparation of equipment or surfaces to be cleaned, the use of expensive materials and technologies, is easy to implement and effective in terms of cleaning quality.

The claimed technical result is achieved by the fact that the method of cleaning the iron surface area from oxides in an arc pulsed discharge includes

- placement of the electrode to be cleaned at a fixed distance from another electrode with a thin wire fixed on it, which excludes spontaneous ignition of the discharge, and provides conditions for an avalanche breakdown of the discharge gap that occurs when there is an evaporating wire vapor in the air,

- wetting the area of the electrode to be cleaned with liquid in the zone of contact with the wire attached to the other electrode, ensuring the creation of electrical conductivity in the oxide layer of the electrode being cleaned,

- applying voltage to the electrode with a wire fixed on it, followed by touching the wire to the moistened surface of the electrode to be cleaned,

- explosion of the wire as a result of a short circuit with its evaporation and the formation of a local area of high temperature on the surface of the electrode being cleaned in the moistened zone of contact with the wire, inside which the moisture evaporates and the oxide layer evaporates. The fixed distance between the electrodes is 10 to 30mm, and the wire diameter is 0.03-0.1mm. The dimensions of the cleaned area of the electrode depend on the magnitude of the discharge current, while for cleaning the area with a diameter of 2 to 15 mm, the discharge current is 10 - 100 A, and the duration of the discharge is 0.01 - 0.05 seconds. Water, for example, tap or distilled water, at room temperature is used as the wetting liquid.

Brief description of the drawings

The claimed invention is illustrated by figure 1, where the positions are marked:

1 - wire,

2 - electrode-wire holder,

3 - variable resistance,

4 - block for supplying voltage to the electrodes,

5 - electrode made of iron coated with a layer of oxides,

and also FIG. 2, where

position 6 shows the parts of the iron surface cleaned from rust in the case when the wire fixed on the anode touches the cathode. The section of the cathode cleared of oxides is indicated by an arrow.

Implementation of the invention

The physical processes underlying the proposed method are as follows. When the wire explodes around the point of contact between the wire and the cathode (or anode) surface made of pure iron, at a sufficiently large discharge current, an excess volumetric space charge of electrons is formed and a thermal cumulative flow of electrons flowing from it, along which the discharge channel moves. In the case of using a cathode (or anode) made of rust-coated iron, no cumulative molten metal channel is formed. In the zone of contact between the wire and the electrode covered with rust moistened to create electrical conductivity, during an electric explosion of the wire, as a result of applying voltage to it, an area of the iron surface free from rust is formed. Cleaning of metal from rust is achieved due to the local release of heat during a short circuit, as well as the action of positive ions of the gas discharge plasma on the electrode when the energy is concentrated around the contact point of the wire with the electrode, which is achieved by eliminating the cumulative thermal channel. As a result, a local area of high temperature (up to 5000 K) is created on the surface of the electrode being cleaned, inside which moisture evaporates, as well as melting and evaporation of iron oxides. At the same time, the iron oxides that have got rid of moisture and surround the area of the metal freed from rust turn into a dielectric and are negatively charged by thermionics of the excess volume space charge. As a result, an electric field decelerates the motion of electrons. The electrons of the volumetric space charge are "locked" inside the region of iron, freed from oxides, and ions from the plasma also enter there.

This method makes it possible to obtain oxide-free sections of the iron surface (cathode or anode) on rusty iron surfaces during the explosion of a wire placed between the electrodes.

To implement the method, wire 1 is fixed on one of the electrodes (for example, the anode-holder). In the experiment, wires of different metals and alloys were used: Cu, Ni, Fe, and others. The diameter of the wires varied in the range of 0.03 - 0.1 mm, their length varied from 10 to 30 mm. The electrode (cathode) covered with a layer of oxides is placed at a fixed distance from the anode with a wire fixed on it, with the possibility of touching the cathode with the wire. The cleaned section of the iron electrode in the contact zone of the wire and the electrode is wetted with a liquid (preferably water) to create electrical conductivity. Then voltage is applied to create a discharge between the electrodes, from a rectifier unit, for example, "Dolphin" 4 with a rectified voltage of 220 V. The discharge current at the maximum with the help of resistance 3 is changed in the region of 10 - 100 A, the discharge duration is maintained 0.01 - 0, 05 seconds. When the wire 1 touches the second iron electrode 5 covered with a layer of oxides, when a voltage is applied between the electrodes, a pulsed arc discharge occurs in the atmosphere. Wire 1 melts and evaporates. When a voltage is applied between the electrodes, when a thin metal wire, fixed on the electrode - holder, touches the surface covered with a layer of oxides of the second electrode, the electric current melts and evaporates the wire, which is placed between the electrodes, while the distance between the electrodes is chosen such that the discharge without a wire does not ignite, and conditions are created between the electrodes for an avalanche breakdown of the discharge gap, which occurs when there is metal vapor of the exploding wire in the air. In this case, around the point of contact of the wire with the surface of the rusted iron electrode during a short circuit, a local area of the surface free of iron oxides is formed, created with the help of thermoelectrons of excess volume space charge and positive ions coming from the plasma.

Between the contact point of one of the electrodes (cathode or anode) covered with a layer of oxides and a thin wire fixed at the end of the other electrode, when the discharge circuit is closed at a voltage applied between the electrodes in the moistened oxide layer on the iron surface, conditions are created for an avalanche breakdown that occurs in the presence of vapors of an evaporating wire in the air, and the appearance of an electric discharge. When the electrical circuit is closed, the local area of the electrode is heated, while the moisture from the iron oxides (from preliminary wetting of the surface) instantly evaporates, and the oxides from the local area of the iron surface melt and also evaporate.

As a result, a section of iron cleaned of rust is formed, surrounded by a non-conductive electric current, a layer of iron oxide freed from moisture, which is negatively charged by electrons from the region of excess space charge. The negative charge on the surface of the oxide layer prevents the spreading of electrons and energy. Ions from the plasma also enter the region of iron cleaned from rust.

An example of a specific implementation.

When implementing a non-self-sustaining arc discharge with a distance between the cathode and anode of 30 mm, a copper wire with a diameter of 0.03 mm was used.

The electrodes (anode and cathode) were iron plates, 40 cm long and 15 cm wide, covered with a layer of oxides. The maximum current per pulse was 80 A. With a single explosion of the wire, a rust-free oval-shaped iron surface with an average diameter of approximately 11 mm was formed. Local wetting of rust was carried out with tap water. The cleaning efficiency is confirmed by Oxford electron microscope studies. As a result of repeated application of the described process, it is possible to quickly and effectively clean the surface of the iron electrodes.

Thus, in the proposed method, for the first time, the problem of cleaning a local area of the iron surface from oxides in an arc pulsed discharge during a wire explosion was solved. The method is simple to implement and effective.

Claims (9)

1. A method for removing oxides from a surface area of an iron electrode in an arc pulsed discharge, including - placement of the electrode to be cleaned at a fixed distance from another electrode with a thin wire fixed on it, which excludes spontaneous ignition of the discharge and provides conditions for an avalanche breakdown of the discharge gap that occurs when vapors of an evaporating wire are present in the air, - wetting the area of the electrode to be cleaned with liquid in the zone of contact with the wire attached to the other electrode, ensuring the creation of electrical conductivity in the oxide layer of the electrode being cleaned, - applying voltage to the electrode with a wire fixed on it, followed by touching the wire to the moistened surface of the electrode to be cleaned, - explosion of the wire as a result of a short circuit with its evaporation and the formation of a local area of high temperature on the surface of the electrode being cleaned in the moistened zone of contact with the wire, inside which the moisture evaporates and the oxide layer evaporates. 2. The method according to claim 1, characterized in that the distance between the electrodes is from 10 to 30 mm. 3. The method according to claim 1, characterized in that the diameter of the wire is 0.03-0.1 mm. 4. The method according to claim 1, characterized in that the dimensions of the cleaned area of the electrode depend on the magnitude of the discharge current, while for cleaning the area with sizes from 2 mm to 15 mm, the discharge current is 10–100 A, the discharge duration is 0.01– 0.05 seconds. 5. The method according to claim 1, characterized in that water is used as the wetting liquid.

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