Method of application of coating by surface welding of solder on structural steel surface

FIELD: mechanical engineering; surface welding.

SUBSTANCE: invention can be used for application of wear resistant coating onto working surfaces of cutting tools, for instance, abrasive coating into surface of milling cutter. Surface to be treated is milled and degreased with organic solvent. Prior to application of solder, flux is applied in layers. Used as flux is saturated water solution of mixture of boric acid, 30%, and sodium tetraborate, 70%. In process of application, flux is head to 300-350°C to completely evaporate water and form solid layer of flux on surface of steel and subsequent porous layer of flux. Solder is applied to flux coated surface of steel with simultaneous delivery of flux of preliminarily dehydrate mixture of boric acid, 30% and sodium tetraborate, 70%, to zone of welding with provision of filling of pores in coating with molten flux. Coating is composite material containing metal solder, particles of hard alloy and glass solder. Glass solder, as viscous component, restrains grows and development of cracks formed in operation of cutting tool.

EFFECT: improved quality of working surface of cutting tools.

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The invention relates to the field of metallurgy. It can be used to produce wear-resistant coatings on steel substrate or the abrasive coating of the working surface of the cutting tool of the type cutters and other abrasive tools, obtained by deposition of solder containing carbide particles on the basis of copper.

Known methods of coating the surface of the cutting tool [1], namely, that the brazed surface previously subjected to degreasing, followed by drying, machining, blasting, chemical degreasing, washing with hot, then cold water, in the case of oxides, etching, rinsing, passivation followed by rinsing with hot and cold water. Then before soldering the parts dried at 50-60°, sherohovatami and using composite finish solder consisting of a filler and a low-melting component, and the flux in the form of a powder or paste [1], mixed with water or alcohol, napravlyayut solder brazed on the surface of the flame soldering. After soldering, the product is cooled and cleaned of flux by dipping the product in hot water for 30-60 minutes, then in cold water, followed by drying it under pressure with compressed air.

The method is complex, mnogooperatsionny, with many components to it and unproductive. The method is not applicable when a non-nuclear submarine is VCE steel solder copper-based using as a filler of solid particles of the alloy to obtain an abrasive tool, used in drilling technology. Cutter, reamer and other drilling tools are on the surface of the narrow areas that should be applied coatings from composite solder containing particles of hard alloy (type VK8) and low-melting component (type copper-zinc solder). Because these narrow platform or working surface of an abrasive tool placed round and tool (milling cutter, reamer, etc.) large size (⊘60-160 mm or more, and the length of 500-1500 mm), it is necessary to spend a huge amount of acids, water, solvents, and to use larger capacity furnaces, and soldering is accompanied by pore formation and obtaining a porous coating of low quality with flame surfacing, this method cannot be used to obtain an abrasive tool, the resulting flame welding of composite solder.

Closest to the proposed invention the selected method [2] soldering structural steels, namely, that in the beginning brazed surface is cleaned from grease, dirt mechanically (with a file, sandpaper) and chemical treatment (degreasing in alkaline media). Then brazed on the surface of the applied flux (in the case of brazing in a protective atmosphere). To this dry mixture of the components of the flux is diluted with distilled water to a thin paste and put spatel the m or a glass rod, then the item dried in a thermostat at a temperature of 343-K for 30...60 minutes With flame brazing flux is served on the brazed surface directly in the soldering process on the rod heated solder. Rod solder melts with gas-flame burner. For brazing of structural steels used copper-zinc solder, and flux use 200, 21, 209 [3], which contain borax 20% boric acid - 70%calcium fluoride - 10%. After soldering flux residues removed blasting, abrasive jet machining or prolonged boiling (5...6 hours.) product in an aqueous solution of chromic anhydride (0,3...0,5 g/l).

The disadvantages of the method of soldering are: limiting use for products of small size and horizontal surfaces of brazed products - in the case of pre-applying a flux containing an aqueous solution of a mixture of borax and boric acid with calcium fluoride and temperature control of the drying process when 343-C (60-80° (C)that leads to deterioration in the quality of welding solder, as further soldering process is accompanied by increased pore formation in the presence of brazed surface moisture; when the flux is fed to the brazed surface directly in the process of soldering the wire solder, too, there is an increase in porosity in the coating of because of the hygroscopic components of the fluorescence is sa, when this occurs the following: a jet of gas supplied to the surface of the rod to melt, discards the flux away from the surface of the rod and the flux does not perform its function, outside the zone of deposition of solder on the brazed surface; how little productive, as mnogooperatsionny.

An object of the invention is to increase the efficiency of flux, improving the quality of the coating on the surface of structural steel composite solder flame welding in the manufacture of cutting tools used in drilling technology.

The technical result is achieved by a method of coating the solder surfaces of structural steel, including machining, degreasing, flame welding soldering in the presence of flux, cooling products, according to the invention the surface of the steel fraserview and thoroughly degreased with an organic solvent, is applied layers on her pre-prepared saturated aqueous solution of a mixture of boric acid - 30 vol.% with brown - 70 vol.%, heated to 300-350°until complete evaporation of water and formation of a dense coating layer on the steel surface and a porous layer of flux on it, Fluconazol the surface of the steel napravlyayut solder with simultaneous flow in the zone of welding solder and you usenow 200-250° With a mixture of boric acid - 30 vol.% and borax - 70 vol.%, formed in the floor of the pores fill with molten flux of the same composition.

The associated analysis of the claimed invention with the prototype shows that the inventive method differs from the known prior treatment of the surface of structural steel, the composition of the flux used, the difference in its condition when applied to the surface before, during and after fusion of the coating.

So in the method prototype pretreated surface structural steel abrasive, sandpaper, followed by degreasing in an alkaline solution laundering and degreaser in hot, then cold water. The inventive method does not emit in a single machining operation, since the method is primarily used to obtain an abrasive tool type cutters, the working surface is traditionally otrisovyvaetsja to obtain the specified size in height with regard to the thickness of the fused layer coating composite solder in the form of a rod containing particles of solid alloy and ligaments (solder). Thus, the proposed method allows to obtain a rough working surface on the workpiece cutters, cut off the better of the file or even the skins of the defective layer containing the greatest number of defects, cracks the dirt, fat. Degreasing the working surface of the cutter in the present invention is carried out carefully and organic solvent type acetone to clean the surface from dirt, but thus to expand and dry the pores and capillaries to obtain the quality of the boundary layer between the working surface and the abrasive coating. The prototype alkaline degreasing solution, but does not guarantee purification from impurities, but, on the contrary, contributes to clogged pores and capillaries with subsequent rastravleniya alkali and declining terms of build, the increase of steam formation.

In the proposed method, an organic solvent (mainly acetone) does not react with the material to be processed, evaporates quickly, freeing the pores and capillaries for further olusanya them. A thorough degreasing and involves reaching effect open the pores and capillaries. Unlike the prototype, in which the flame when the welding flux is supplied to the surface of a steel rod of solder, in the proposed method, thoroughly cleansed, the working surface of the cutter cover flux, and layers. Pre-prepared saturated aqueous solution containing a mixture of boric acid and borax, is applied to the steel surface by simple mechanical and heat the surface or the flux to a temperature of 300-350°C. When this is m first layers or the layer of flux penetrate all pores and capillaries on the surface and cover with a thick crust evenly the entire surface.

Since the first layer scoring all void on the surface, the subsequent layer contributes to the strengthening of ties at the interface of the surface - deposited abrasive coating.

Applying a flux on the working surface of the steel mill (mill) surface heated wire solder (as in the prototype) is not effective, because before applying solder, the working surface should be heated to a high temperature close to the melting point of the solder, and this means that the surface has time to oxidize. The process of soldering or welding flame way is fleeting, and the flux falling on the work surface at the time of deposition of the solder, enhances the chemical reaction between the components, pore formation and deterioration of the quality of the coating and, consequently, the operational properties of the cutting tool.

In the proposed method uses a flux in the form of saturated solution and the ratio of the components, where the Boers more (70 vol.%), while boric acid is less than (30 vol.%) because at the ratios, where the Boers more than 70 vol.%, while boric acid is less than 30 vol.%, during welding and cooling of the composite solder is formed somewhere glassy mass, covered with cracks, and somewhere (especially in the pores) in the form of a dry powder. Such flux promotes corrosion coating, it is necessary to wash out the volume on which rite. When the flux borax contains less than 70 vol.%, while boric acid is greater than 30 vol.%, observed oxidation coatings after cooling, and therefore, to avoid further oxidizing action of the flux, it should also be removed. The proposed ratio of the components of the flux allows you to get full protection from oxidation as the working surface of the steel, and surfaced coating layer on it.

Preparation of a saturated aqueous solution of a flux of a mixture of boric acid and borax allows you to have fine and coarse fractions, which is necessary for use of the crystalline fraction of oflesbian pores and capillaries and coarse together with the crystalline - to improve the quality of surround fluxing in the coating process applying solder. Such a flux well into emptiness, and when heated it up to 300-350°get strong nematodes floor in the first layer and the same properties, but porous coating over the first layer. This greatly simplifies the process of olusanya surfaces with any inclination to the horizontal plane, which is necessary for oflesbian many working surfaces of such abrasive tool, as the cutter.

In the method prototype flux after application on the working surface of the cutter and the point e is on at 60-80° To become aggressive because of the larger amount of boric acid (70 vol.%), and after the final drying - leaves from the surface of the loose powder mixture. The proposed method is up to 200°removes moisture from plusbank layers, and then when 300-350°firmly establishes that repeatedly confirmed experimentally. Unlike the prototype in the process of welding composition of the first solder is melted flux, located on the working surface of the cutter, then served in the Deposit area at the same time the dry mixture of the same composition of the flux, as before, and melt the rod composite solder with flux. When flame surfacing coating abrasive layer on the working surface of the cutter has significant advantages over the method of the prototype, since the working surface is constantly in an inclined state, the solder is in contact only with a dry flux, which contributes to the reduction of steam formation, receiving higher quality dense layers of the coating. And the most distinctive feature of the proposed method is filling forming pores in the melt, and then cooling the coating of molten flux. I.e. first flux, dry mixture of boric acid and borax, flushed melt the solder, not allowing it to oxidize, and then strengthens it further, filling the pores and cracks (if they poyavilas the) high-melting solder glasses, what is the melt flux. For the first time, the flux becomes necessary to cover and does not play a negative role, as previously (in the prototype).

This distinctive feature was detected unexpectedly, in the time it took to prepare the samples for metallographic studies. For cutting with cooling needed EDM cutting. But it could not be done due to the fact that the glass adhesive is not conductive and insulated the entire sample. Because drilling is present in the well fluid, the abrasive effect of stray electric currents. In the formation of galvanic couples in the abrasive coating of the tool is destroyed. The proposed method allows for the formation of solder glasses not only to improve crack resistance, to increase the strength and durability of the tool, but also to protect from the destructive electrochemical action. Thus, the claimed method meets the criteria ovelty and significant differences. He has a practical application. It is expected to apply in the LLC bittechnical and other organizations in the manufacture of drilling cutting tools for various purposes and types. Metallographic studies have confirmed coatings offer a high quality fashion.

The proposed pic is b coating applying solder to the surface of the structural steel is implemented as follows.

For the manufacture of abrasive tools type cutter use the cutter body with the pads installed at an angle to the axis of the housing, which after deposition of the abrasive coating on them, i.e. cutting edges. The body is made of steel grade 40 according to GOST 1050-74. The future surface cutting edges fraserview to the depth calculated from the desired height of the cutting part of the cutter. The surface becomes rough. Roughness is regulated regime milling. After milling the surface of the edges thoroughly washed with an organic solvent, mainly acetone as more quickly and without a trace of evaporated solvent, seeking not only to clean and degrease the surface, and free from clogging and oiling the pores and capillaries on it. Prepare a flux for oflesbian the surface edges. This known method of preparing a saturated aqueous solution of a mixture of boric acid, taken in an amount of 30 vol.%, with brown, taken in an amount of 70 vol.%, as the optimal composition exhibiting maximum activity with excellent insulating properties. Water over the crystals are drained, and the thick portion of the mixture is applied (by brush, spatula, etc.) on the surface of the edges in several layers. After you have applied the first layer, which has penetrated into the pores and capillaries and RA is nomemo distributed over the entire surface, heat the cutter body to 300-350°for water evaporation and tight fastening of the flux coating on the surface edges. Then put layers of flux until get enough (˜0,5 mm thickness (the height of the abrasive coating solder paste flux, determined experimentally, continuing the heating at the same temperature, until the evaporation of water and is not formed is not hygroscopic porous layer of flux on the first dense layer of flux. Take the finished solder containing filler particles of solid alloy (VK-8) -30-40 vol.% and a bunch of (Lncomc-49-9-02-02) 60-70 vol.%, in the form of composite solder in the form of a rod. At a given angle to the surface of the edge cutters set rod and flux dispenser. The flux dispenser is a device that represents a container with drainage in the form of a tube, but with refractory material (such as tungsten) in the part where it's located near the burner flame.

The tube has a valve for closing and termination of receipt of the flux in the area of welding or blank in the tank in the transition portion to the pipe. The flux that is in the tank, is prepared in advance. The composition of the flux - boric acid - 30 vol.% and borax - 70 vol.%. The mixture components are dried at a temperature of 200°With (all the water from the boric acid leaves at 100-150°and from the Boers, 200°). The container is sealed, and the flux in the area of non-nuclear submarines the Cai to melt solder is supplied dry and does not create conditions for steam formation in the coating and on the border with the surface edges. After the filing of the jet of gas from the acetylene-oxygen burner composite solder from the end melts and covers the surface of the edge on which the gas stream at the same time melts layers of flux that protects from oxidation. Supplied from a dispenser flux promotes the best effective flowing property of the solder, improves the wettability of the bundle of the surface of the particles of the alloy, which is very important to obtain a strong adhesive connections between the components and obtaining a high-quality coatings with improved performance characteristics. In the process of deposition of the coating is the process of evaporation of components of the ligament, flatulence. Therefore, despite the fact that the method solves the problem of steam formation due to the presence of water in the Deposit area, there remains the problem of steam formation as a result of a chemical reaction and evaporation of the more fusible component. This problem is solved by a method as follows. The resulting pores are filled with the molten flux of the same composition. Due to this, the coating becomes solid and adhesive hardening of the walls of the pores with a glassy high-melting solder inside them (which is the flux after melting the mixture). Thus we get the working surface of the cutting tool with improved performance characteristics (see table 1).

The experiment was carried out using rod (composite solder composition Mnsac-49-9-02-02 (Cu - 49%; Ni -9%; Co - 0,2%; Mn - 0.2%, the rest - Zn). Particulate alloy were taken from 0.5-5 mm Milled sample is made of steel 40. The milling parameters: speed 1.6 s^-1axial load - 7.5 MPa, and the washing liquid is water. The time interval for all experiments the same and equal to 1 hour. For the performance of milling were adopted, the volume of milled metal object and the wear per unit time and unit performance.

The results of the study (see table). showed that, compared with f the m proposed method of coating the solder surface structural steel allows you to receive the cutting tool, with the ability to more effectively and efficiently to carry out the volume of milled material (1.2-1.5 times), and the wear of the coating decrease (1.5-1.6 times). The effectiveness of the proposed composition of the flux has increased manifold in connection with the use of a mixture of borax and boric acid. Found the best option in the interest regarding the use of the mixture as the drill begins to stir after 900°and gives a fragile glass or remains in the form of powder on the walls of the pores. The use of boric acid in a greater number provokes her work as acid, which is not acceptable for welding, since it adversely affects the particles of solid alloy, and a bunch of (solder). At the optimum ratio, as suggested in the way) the action of the flux during the preliminary application to the steel surface and the deposition process is restorative in nature. This is evidenced by the high quality border welding, shining surface and shiny surface then (observed in the fracture of the sample).

Filling molten flux then gives a new solution when using flux. Prior to the proposed method, the flux must be cleaned after soldering, welding - they destroyed the coating and the steel, which was napravlyali solder. The proposed method allowed the flux to work as solder glasses in OS is Alannah areas of the coating (in the pores), which has the following valuable qualities. The coating is a composite material containing solder metal particles of solid alloy and solder glasses that enhance the total system (wettability, adhesion, crack resistance, wear resistance increase). The growth and development of cracks during operation of the cutting tool constrains solder glasses as viscous component of the composition, since the cutting is associated with increasing temperature in the cutting zone.

Sources of information

1. Sveska, Nfesc. Brazing of metals. M: mechanical engineering, 1988 (pages 28-30, 46-160) (similar).

2. GPhotoShow. Welding and brazing in the aviation industry. M: mechanical engineering, 1983, p.148-181 (prototype).

3. The mechanical engineer's Handbook (6 tons) (edited Aaaas), volume 5, book 1, M, 1964, s (similar).

Method of coating applying solder to the surface of structural steel, including machining, degreasing, flame welding soldering in the presence of flux and cooling, wherein the mechanical treatment is carried out by milling, carry out degreasing with an organic solvent before applying solder is applied layers of the flux in the form of saturated aqueous solution of a mixture of boric acid 30% vol. and the Boers 70 vol.%, in the process of applying heat flew the temperatures of 300-350° With a total evaporation of water with the formation of a dense layer of flux on the surface of the steel and subsequent porous layer of flux and welding solder spend on Fluconazol a steel surface with simultaneous flow in the zone of welding flux of the pre-dehydrated mixture of boric acid 30% vol. and the Boers 70% vol. to ensure filling of the molten flux generated in the coating pores.