RU2725946C2 - Method of forming blade edge - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to application of coatings on metal surfaces by means of electric arc surfacing and can be used for machining of metal surfaces of tool cutting part, in particular formation of cutting edge of knives. Essence of the claimed method consists in the following. Surfacing with anode electrodes is performed simultaneously from both surfaces of knife edge, and the cutting edge of the knife is formed by means of a V-shaped draw plate of superhard material located near the weld zone, when the edge of the knife is moved from the deposition zone to the draw plate. At surfacing there used are electrodes—anodes from highly electroconductive carbon fiber in form of carbon nanotubes. During surfacing, filler material is used in form of steel wire, suite with highly electroconductive carbon fiber from carbon nanotubes.EFFECT: technical result is formation of tool cutting edge for various purposes.3 cl, 2 dwg

Description

The invention relates to the field of coating on metal surfaces by the method of electric arc welding and can be used to process metal surfaces of the cutting part of the tool, in particular the formation of the cutting surface of knives.

There are various methods of coating on the surface of metals by plasma, laser, electron beam processing. The methods used, as a rule, consist in carrying out micrometallurgical processes on the surface of the metal being treated or in its surface layers, leading to smoothing of the surface, elimination of impurities, and the creation of more stable surface structures.

Currently, carbon coatings are widely used. Carbon coatings have a number of unique properties: high hardness and at the same time low coefficient of friction, good thermal conductivity and high resistance to aggressive chemical environments. Their application to the working surface of parts of friction units, dies and punches of dies, parts of molds, cutting tools, etc. is one of the effective technological methods that can increase the wear resistance of surface layers, the durability and reliability of devices for various purposes.

The well-known "Method of applying a corrosion-resistant carbon coating to the surface of steel" according to patent RU 2591826 C2 using a high-speed laser treatment of ultrafine graphite powder placed on the surface of unalloyed steel, can be obtained a thin, up to 5 nm thick, surface film with transition amorphous crystalline state, having good adhesion to the substrate. Adhesion to the substrate is provided by the creation of an intermediate layer consisting of non-stoichiometric iron carbides. The obtained nanosized graphite layers in a wide range of anodic and cathodic potentials behave like an ideally polarizable electrode and prevent the flow of anodic dissolution of iron.

The known "Method of applying a diamond-like coating on the blades of surgical scalpels" patent RU 2527113 C1, according to which vacuum laser ablation is performed in the reaction chamber with the evaporation of the target by a solid-state laser and the subsequent deposition of an amorphous diamond-like coating in the form of a film on the blade of a surgical scalpel. The quality of surgical scalpels is improved by applying a carbon biocompatible coating. The cutting surface is more even and smooth, which provides an easier course of the postoperative period.

According to the materials of the scientific article "Mechanical Properties of Materials Obtained by Cladding of Carbon Fiber on Steel by Electron Beam in an Air Atmosphere" (authors A.I. Bardin, A.A. Losinskaya, publication in the journal "Actual Problems in Mechanical Engineering." Volume 4. No. 4 . 2017) non-vacuum electron beam deposition of carbon fibers is an effective method for creating high-carbon layers of great depth on the surfaces of low-carbon steel parts. The formed layers have high hardness (above 5 GPa), wear resistance and acceptable impact strength.

The known "Method for the formation of a carbon coating in a vacuum" patent BY 16244 C1, according to which produce an electric arc evaporation of a graphite cathode under the influence of an electric arc created between a graphite cathode and an anode by applying voltage to them and condensing carbon particles on the surface of the product to obtain hard wear-resistant coatings.

A disadvantage of the known methods is the complex process technology associated with the need for the availability of industrial equipment (laser, industrial electron accelerator, reaction chamber, etc.), long cycles of bringing the product materials to the consumer and their subsequent repair (restoration of the worn surface of the products and tools).

Closest to the claimed one is a method of electric arc surfacing of edge surfaces (AC 556909 V23 K9 / 04) of machine parts, including knives subject to abrasive wear, based on electric arc surfacing by electrodes under the influence of an electric arc created between two electrodes - anodes and knife edge surfaces by applying voltage to them, using filler material and forced surface formation by a die, which allows to reduce the amount of molten base metal, improve the quality of the deposited layer and increase the wear resistance of parts.

The disadvantage of this method is the use of hard graphite electrodes and their location on the same surface of the edge, which does not allow to obtain the desired shaping of the coating surface of the product, for example, the edge of the knife.

The problem to which the present invention is directed, is to simplify the technology of coating on the metal surface of the cutting part of the tool and obtain the required shaping of the coating surface on the product, for example, the edge of the knife.

The technical result is achieved by the fact that in the method of forming a knife edge based on electric arc surfacing with electrodes under the action of an electric arc discharge created between two electrodes - anodes and knife edge surfaces by applying voltage to them, using filler material in contrast to the known electrode surfacing - anodes produce simultaneously from both surfaces of the edge of the knife placed in the guide - the cathode, while the edge of the knife is moved from the surfacing zone into a V-shaped die made of superhard material.

At the same time, surfacing is carried out by electrodes - anodes of highly conductive carbon fiber in the form of carbon nanotubes.

At the same time, surfacing is carried out using filler material in the form of a steel wire twisted with highly conductive carbon fiber from carbon nanotubes.

In the proposed method, the guide performs the function of an electrode - a cathode.

The essence of the proposed method is as follows.

The method of electric arc surfacing is well known and is a common type of welding, while the arc burns between the base metal (substrate) and the electrode, and the deposited (filler) material is fed into the welding zone as it is deposited. This type of welding can be done with one or more electrodes. According to the welding journal "Welding Handbook" Materials and Applications Part 2, Figure 6.7, the electrical conductivity of graphite is higher than that of alloy steels and platinum, however, due to its layered structure, it is brittle and unstable and is used, as a rule, in the form of a non-consumable electrode - a rod during surfacing filler wire, which, however, is also involved in the welding process and is spent on evaporation and transfer of carbon plasma to the surface of the metal substrate. At the same time, superhard carbon materials have now appeared consisting of tightly packed carbon nanotubes (CNTs), the conductivity of which is on the same level as copper, gold and aluminum, with the formation of thin wires and behaving like wires, industrially produced in the form of CNT fiber coils and available on the market. "Strong, Light, Multifunctional Fibers of Carbon Nanotubes with Ultrahigh Conductivity" Science Jan 11, 2013: Vol.339, Issue 6116, pp. 182-186.

The strength of the created materials reaches 9.6 GPa "High-Strength Carbon Nanotube Film from Improving Alignment and Densification" Nano Lett., 2016, 16 (2), pp 946-952, which meets the requirements for the material of the cutting zone of the cutting tool when they are application by electric arc deposition.

The cutting surface of a tool, such as a knife, includes leads and a cutting edge. The dimensions of the inlets are 1-2 mm, the cutting edge is approximately 0.1 mm, and the tip of the edge itself is tens of microns, with a width of several microns.

Thus, the formation of a superhard coating is required in the zone of the edge of the edge, which is a comb structure of the composition of the steel grade material.

The formation of the edge is carried out by a V-shaped die made of superhard material, mainly diamond (hardness 10 GPa), located at the surfacing when moving the edge from the surfacing to the die.

The implementation of the method according to the invention is as follows and is explained

FIG. 1, which shows a method of forming a knife edge;

FIG. 2, section AA in FIG. 1, which shows a knife edge forming die.

The knife to be formed by the edge is installed by the edge part adjacent to its handle into the guide (cathode) in the form of a cone 1, behind which there is a welding (surfacing) zone 2, with a slight pressure of the edge on the guide. In this case, the surfaces of the knife edge are contacted with the anode electrodes 3 wound on coils 4 and connected by means of spring-loaded current leads 5 to the DC power circuit, and the knife walls with the ends of the coils 6 with filler wire 7 (high-alloy steel). When applying AC voltage (manually closing the circuit with button 8) 220 V, the pulse transformer 9 circuit generates a constant (welding) current (in the absence of a transformer, a short circuit current - short circuit) is generated, performing arc ignition and surfacing process. Simultaneously with the supply of voltage and the start of the welding process, the edge of the knife under the influence of a hand on the handle of the knife moves in the V-shaped die 10, while the deposited material from the surfacing zone enters the die, which forms the edge of the knife. The filler wire is fed into the surfacing zone synchronously (unwinding from coils) with the knife moving. After the knife leaves the deposition zone and the die, the circuit is opened and the opening of the chain is duplicated manually by opening the button 8.

The proposed method of forming the edge of the knife takes into account the following technological factors:

- the amount (volume) of the deposited material corresponds to the required volume of the formed edge (performed by the correspondence of the diameter area of the filler wire to the cross-sectional area of the formed edge);

- provides quick heating of the surface region of the substrate (knife material) by modifying its metallurgical structure, without significant heating of the underlying bulk of the substrate, followed by rapid cooling, thereby suppressing the nucleation and growth of crystals and does not phase segregation and separation of additives or components of the substrate;

- the stability of the arc burning and the deposition process is ensured by the implementation of the principle of the arrangement of arc machines for feeding the electrode or filler material with a constant speed independent of the arc voltage or any other factors and is performed by synchronizing the supply of material to the deposition zone and moving the knife rotating the ends of the coils with filler wire, at a current density of 70-85 a / mm ² and a feed speed of 5 cm / sec, which leads to a complete melting of the filler material and contributes to the process of self-regulation of the arc in the form of an external characteristic of the power source close to hard V AC in optimal mode of operation;

- power consumed for 2-3 seconds (the time the knife edge passes through the fusion zone), taking into account the required electrode section, does not exceed 0.6-0.75 kW;

The deposition process can be modified, taking into account the purpose and size of the tool, for example, to form the edge of the ax, the corresponding welding parameters, the corresponding diameters of the electrodes, filler wire and the corresponding die section with an angle of | 3, which must correspond to the shape of the tool sharpening depending on the purpose of the tool .

When a die passes from a highly heat-conducting material (diamond), the deposited (carbon) material begins to cool, the die walls, polished to a surface roughness of 1-2 μm, form a surface with a similar roughness, which provides low friction resistance and, accordingly, easy cutting of the processed material.

The method and devices developed on its basis, for example, portable using a battery, can be used to form the cutting edge of tools for various purposes, and any housewife will appreciate the claimed device.

Claims (3)

1. The method of forming the edge of the knife, including electric arc surfacing of filler material on the surface of the edge of the knife under the action of an electric arc generated between two electrode anodes by applying voltage to them, characterized in that the surfacing is performed simultaneously on both surfaces of the edge of the knife, which is placed in the guide -cathode, then the edge of the knife is formed, which is moved with the deposited material from the surfacing zone into a V-shaped die made of superhard material. 2. The method according to p. 1, characterized in that the surfacing is performed by electrodes-anodes of conductive carbon fiber in the form of carbon nanotubes. 3. The method according to p. 1, characterized in that they use filler material in the form of a steel wire twisted with an electrically conductive carbon fiber of carbon nanotubes.

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