MXPA01008959A - A method of depositing flux or flux and metal onto a metal brazing substrate - Google Patents

Abstract

The present invention is directed to a means for the surface preparation of a metal or metal alloy substrate. In the process of the present invention, a stream of a mixture of flux particles and metal particles is hurled at the substrate at velocities effective for flux adhesion to the surface. The velocities of the particle stream is adjusted so that the flux particles adhere to the surface and the metal particles bounce off the surface. At higher temperatures and velocities, the metal particles are co-deposited with the flux.

Description

A METHOD FOR DEPOSITING FUNDENT OR FUNDENT AND METAL ON A METAL CLAD WELDING SUBSTRATE FIELD OF THE INVENTION The present invention relates to a method for welding two or more metal articles by brazing. More particularly, the present invention relates to methods for depositing a fluxing method with or without metal powders on a metal substrate prior to a brazing operation.

BACKGROUND OF THE INVENTION Aluminum and its alloys are particularly useful materials for inclusion in metallic components of vehicles such as automobiles, trucks, aircraft and the like. Aluminum alloys are lighter than steel alloys and therefore provide weight advantages in many vehicle applications. The light weight and excellent heat transfer properties of aluminum alloys make them particularly attractive candidates for use in heat exchangers such as radiators, heaters, evaporators, oil coolers, condensers and the like. These heat exchangers and similar components are typically manufactured from a multitude of extruded shaped parts which are subsequently assembled, clamped, cleaned and welded in a brazing process. When brazing aluminum workpieces, an aluminum brazing alloy (eg, an aluminum-silicon alloy) is placed between the surfaces to be joined and the workpieces are heated to a temperature which melts the brazing alloy but not the underlying workpiece. By allowing to cool, the brazing alloy solidifies as a union between the work pieces. The brazing alloy is typically introduced into the surfaces of aluminum material by coating thereof in a roller bonding operation. A common practice of brazing includes cleaning the components via a suitable solvent (to remove oils and the like from the surfaces to be brazed) followed by the application of a flux to the components previously subjected to brazing to be joined. The co-dependent components are heated in a controlled atmosphere to replenish the oxidation, this atmosphere is typically dry nitrogen. The paper melts to reduce the oxides of the contact surfaces of the components which are to be joined by means of brazing. The flow is applied after fabrication that the individual workpieces have been brazed, commonly after assembling the components (for example as a heat exchanger) before subjecting them to brazing. The flux can be applied directly as a dry powder or can be mixed with a carrier such as water or alcohol and can be applied as a suspension over the entire work piece. In this latter case, the carrier is subsequently removed via a drying step, which leaves the flux as a powder on the surface of the workpiece. Flux is only required in areas where joints or metallurgical joints are required. However, it is a common manufacturing practice to apply fluxes over the entire assembly, often including devices to contain the parts during the brazing step in the furnace. This results in excessive use and waste of flux, the need to clean the devices and increased furnace maintenance due to the corrosive nature of the flux. In addition, the flux cleaning and application process is time consuming and concomitantly expensive. It should be noted that the flux adheres loosely to the work pieces as a powder. Therefore, care must be taken to avoid the removal of the flux during any handling of the components before subjecting it to brazing.

An alternative to covering with flux the whole assembly is to apply flux to the work pieces before working them or forming the material in a previous operation to the application of flux. The operation prior to the application of flux is advantageous insofar as flux can be applied only in the coating where the joints are formed; and the uncoated areas do not present flux. However, such conventional techniques of operation prior to the application of flux have not found wide commercial applications. One method of operation prior to the application of flux has been to disperse flux in a binder and coat the workpiece with a flux-binder mixture. During brazing, the binder volatilizes which can result in undesirable voids within the joint that must be filled to ensure sealing of the brazed components. Another drawback of this flux-binder coating technique is that the brazing surfaces typically have to be cleaned beyond standard laminate thereby increasing the operating costs by several hundred per batch of brazing metal mass that is produced. An alternative route to the operation prior to the application of flux is to eliminate the coating process and apply flux and a metal or alloy coating in a deposition process either simultaneously or sequentially. One such technique is thermal spraying, as described in U.S. Patent No. 5,594,930. The '930 patent describes the spraying of molten droplets of aluminum and silicon or an alloy thereof on an aluminum substrate susceptible to brazing. U.S. Patent No. 5,820,939 also discloses a method for thermally spraying metallic coatings onto cleaned non-roughened aluminum alloy substrates. The method includes a wire arch, thermally sprays the molten metal bond droplets and melt particles on the substrate using gas propulsion to concurrently deposit flux particles and bonding droplets. In these methods, the molten droplets pass through the air and form additional oxides thereon which generates the need to deoxidize the substrate. Hot pressing of powders of aluminum, silicon or an alloy or mixture thereof on an uncoated aluminum substrate is described in U.S. Patent Nos. 5,330,090 and 5,547,517. Powder compaction typically results in minimum hole levels of approximately 10%. The formation of voids is undesirable and the hot pressing process of the powders on the substrate can be problematic.

Coating processes for simultaneous application of flux with aluminum and silicon are described in U.S. Patent Nos. 5,100,048 and 5,190,596. The '048 patent describes a process of immersing an uncoated aluminum substrate in a suspension in aluminum, silicon and flux alcohol. When the alcohol evaporates, the silicon and flux that remain on the substrate weakly adhere to it and tend to chip the substrate during assembly. The '596 patent discloses a method for applying a paste containing aluminum, silicon and a binder onto an uncoated aluminum substrate. In any case, silicon and aluminum form a thin coating layer on the aluminum substrate and a flux is incorporated therein. This system adheres better to the substrate, but the volatilized binder generates gaps in the joint. Accordingly, the need remains for a method for depositing flux for brazing onto metal substrates before working the metal which minimizes the amount of flux used in the assembly subjected to brazing, adheres the flux to the substrate without the use of a binder and additionally You can deposit the metallic coating on the substrates.

BRIEF DESCRIPTION OF THE INVENTION This need is met by the method of the present invention which includes a method for treating a surface of a metal article, a metal substrate by spraying a treatment composition that includes metal halide particles dispersed in a carrier gas on the surface of the metal. a metallic article at a high enough velocity to form a layer of the metal halide particles on the surface. The minimum deposition rate of the metal halide particles is approximately 100 m / sec. This technique is particularly useful for pre-bonding flux to the brazing components. The gas may be air, helium, nitrogen or combinations thereof and may have a temperature from about room temperature to 500 ° C. The type of gas and the temperature of the treatment composition can be varied to control the velocities of the particles entrained in the gas of the treatment composition. A less dense gas (for example helium), higher temperatures and higher pressures provide higher particle velocities. A further set of particles, preferably formed of a metal, an alloy thereof or a mechanical mixture of a metal and an alloy thereof, can also be dispersed in the gas. Next, reference to a metal as the material of a substrate, particle or coating means that it includes metal, alloys thereof as well as mechanical mixtures of metals and metal alloys, unless otherwise indicated. The metal or metal alloy particles are considered to assist in the deposition of the metal halide particles on the surface of the metal article. The metal halide particles and the metal particles preferably each have a diameter of about 5 to about 50 μm. The velocity of the particles sprayed onto the surface of the metal article to be treated determines whether the metal halide particles are deposited alone on the surface or if metal halide particles and metal particles are co-deposited on the surface. In one embodiment, the velocity of the particles is selected so that only the metal halide particles are incorporated into the surface of the article while the metal particles recede or bounce off the surface and are not incorporated into the article. When the treated composition is sprayed at speeds of about 200 to about 550 m / sec, a layer of metal halide particles is deposited on the metal surface in an amount of about 1 to about 12 grams per square meter of the surface.

In another embodiment, the treatment composition is sprayed at a rate and by which metal halide particles and metal particles are incorporated into the surface of the article. A higher speed of the treatment composition is needed for the incorporation of only the metal halide particles on the surface of the article, which preferably is greater than about 550 m / sec. This mode results in a metal halide layer on the surface of the metal article and also generates a coating layer of the metal particles. The method of the present invention can be used to treat metal articles formed of aluminum alloys, copper alloys, steel alloys, magnesium alloys and nickel alloys. Suitable aluminum alloys are those of the aluminum association series lxxx, 2xxx, 3xxx, 4xxx, 5xxx, 6xxx, 7xxx or 8xxx. The present invention is particularly suitable for producing a brazing sheet previously subjected to flux application which is coated or uncoated. An uncoated brazing sheet can be applied to flux and coating in a single process using the method of the present invention. In another additional embodiment of the invention, the metal halide particles can be encapsulated with a metal such as Al, Cu, Zn, Mg, Mn, Ni, In, Li or Fe. The metal coating on the metal halide particles provides metal-to-metal adhesion of the encapsulated particles to the substrate. Other particles, including those which otherwise traditionally exhibit poor adhesion to metallic substrates, such as particles of a transition metal (eg, silicon or silicon alloys) can be encapsulated in these metals and can also be deposited. These encapsulated particles provide the opportunity to apply a flux and a coating layer to braze a sheet with superior adhesion properties.

BRIEF DESCRIPTION OF THE DRAWINGS Other features of the present invention will be further described in the following related description of the preferred embodiments which should be considered in conjunction with the accompanying drawings, wherein similar figures refer to similar parts and further in which: Figure 1 is a photomicrograph enlarged ten times from a coated aluminum sample in example 1, - figure 2 is a ten-fold enlarged photomicrograph of the coated aluminum sample in example 1, after working; - Figure 3 is a backscattered electron image showing a cross section of the coated aluminum sample in example 2; Figure 4 is an X-ray map of the image of Figure 3 showing the location and concentration of elemental aluminum Figure 5 is an X-ray map of the image of Figure 3 showing the location and concentration of elemental silicon; Figure 6 is an X-ray map of the image of Figure 3 showing the location and concentration of elemental potassium; and Figure 7 is an X-ray map of the image of Figure 3 showing the location and concentration of elemental fluorine.

DESCRIPTION OF THE PREFERRED MODALITIES This need is met by the method of the present invention, which includes a method for coating the surface of the metal substrate with a stream of a treatment composition containing metal halide particles (flux, an inorganic fluoride salt) or metal particles. , or both, which is sprayed onto a metal substrate at speeds sufficient to result in adhesion to the substrate of the halide particles both the halide particles and the metal particles. The particle stream and the resulting coating may comprise: 1) metal halide single particles, 2) a mechanical mixture of metal halide particles and other particles that are formed from a metal, or 3) flux particles or metal particles. of transition, or both, encapsulated within a metallic or metallic alloy cover. In a first embodiment of the invention, the treatment composition includes flux particles. The treatment composition is sprayed at particle speeds resulting in a coating of the flux particles on the metal surface, preferably higher than about 100 to about 1200 m / sec. The resulting coating consists solely of flux, preferably in amounts of about 1 to about 12 g per square meter of metal surface. In a second embodiment of the invention, the treatment composition includes flux particles and other particles. The other particles can be formed from metals, metal alloys, ceramic materials, cermets, polymers or mixtures thereof with metals or metal alloys as particularly preferred. The flux particles and the other particles preferably range from about 5 to about 50 μm in diameter. The ceramic particles can be formed from SiC, Si3N4, A1203, cubic boron nitride or combinations thereof. The speed of the treatment composition determines whether the flux particles alone are deposited on the metal surface or if the flux particles and other stirred particles are deposited on the metal surface. It is considered that other particles, particularly when formed of metal, clean and roughen the metal surface to be coated and also impede and drive the flux particles on the surface. A flux-only coating is obtained when the flux particle velocities within the treatment composition stream are above the critical velocity for them (greater than about 100 m / sec), but below the critical velocity of the flux. the other particles (typically about 550 m / sec or less for metals and metal alloys). The critical speed is defined as the minimum speed necessary for the adhesion of a specific material to a specific substrate. The other particles bounce off the substrate and can be recycled for reuse by applying another coating of the flux particles. Under certain circumstances, the resulting adhesion of a flux coating prepared on mixing with other particles may be superior to a flux coating prepared by directing flux particles alone on the underlying substrate. The ratio of percent flux volume to percent volume of other particles in the treatment composition can vary widely, based on the rate of coating application, the cleaning of the substrate and other operating parameters, and can be from about 5:95 to about 95: 5. Alternatively, a second embodiment can be used to deposit a coating of flux particles and metal particles simultaneously on the underlying substrate when the critical speeds of the metal particles are exceeded (typically greater than 550 m / sec or greater). As described above, the metal interspersed with the flux may be pure metal, metal alloys or mechanical mixtures thereof. It should be recognized that the particle velocities that are obtained within the particle stream are a function of the density, shape and size of the particles. Therefore, a distribution of particle velocities is present within the particle stream. The incorporation of metal and flux into the coating may be particularly desirable when the metal can be used for coating material in the brazing process.

In a third embodiment of the invention, the treatment composition includes gas entrained flux particles encapsulated in metal or metal alloy which likewise and sprayed onto the substrate at sufficient rates resulting in adhesion of the encapsulated flux to the substrate. The presence of a metallic / metal alloy outer shell over the flux improves the deposition efficiency of the process (the deposition efficiency is the ratio of particles that adhere to the total number of particles directed to the substrate). The amount and type of metal (or metal alloy) that encapsulates the flux can be varied. Examples of suitable encapsulating metals include Al, Cu, Zn, Mg, Mn, Ni, In, Li or Fe. In a particularly desirable embodiment, the encapsulated metal flux can be mixed with particles of silicon or silicon alloy and can be deposit to form a coating on aluminum alloys. The deposition efficiency of silicon or silicon alloy particles can also be improved by encapsulating them with a metal or metal encapsulated with silicon or with a silicon alloy. The metal-silicon coated flux or the metal-coated flux and the metal-coated silicon interact with the underlying aluminum substrate to create a molten coating within the furnace during a brazing cycle. In this embodiment, the encapsulated powders are typically sprayed at speeds in excess of about 400 m / sec. The present invention uses a coating technique similar to that detailed in U.S. Patent Nos. 5,302,414 (the '414 patent) and 5,795,626. The '414 patent describes an apparatus and process for spraying metal, metal alloy, polymer or a mechanical mixture of a metal and an alloy onto a substrate at supersonic speeds, whereby the surface of the substrate is coated with any material that is entrained in the flow. When polymer is sprayed onto the substrate, the '414 patent indicates that a subsequent polymerization step (heat) is required to adhere the polymer to the substrate. The result of this rigorous treatment of the surface is a coating of the particles bound to the substrate. Each of the embodiments of the present invention uses the same basic method of spraying particles on a surface to form a coating therewith. Nevertheless, in the present invention, the metal halide (an ionic salt or mixture of ionic salts) is deposited on a metal substrate. Although metal or metal alloy particles can freely share electrons for binding to a metal substrate, ionic salts (eg fluxes) do not. Despite this inability, it has been shown that the flux adheres to metal substrates when sprayed at speeds greater than about 100 m / sec. The control of particle velocity is integral to the present invention so that the desired particle is deposited, particularly when multiple types of particles are present in the treatment composition. Particle velocity is affected by various factors including the geometry of the spray nozzle, the density of the particle, the shape of the particle, the size of the particle, the type of gas, the temperature of the gas and the pressure of the gas . The velocity of the particles is affected in part by the design of the equipment used to spray the treatment composition. A preferred apparatus is a convergent-divergent type nozzle that compresses gas and entrained particles through a minimum throat and then expands and accelerates the gas and entrained particles at high speeds. The internal dimensions of the nozzle can alter the speed of the particles. In general, the larger the convergent-divergent nozzle, the faster particle velocities are obtained. The placement distance (nozzle to substrate) is not especially critical and can be approximately 2.5 to 13 cm (1-5 inches). At this distance, the resulting spray stream has a certain area in cross section. The velocity of the particles in the area and cross section is not uniform. In general, the particles move more slowly around the periphery of the spray cross-section. As a result, the particles around the periphery of the metal surface do not reach the critical speed for adhesion. Advantageously, these slower particles serve to perform abrasion and clean and clean the surface immediately in front of the portion of the spray cross section which flows at or above the critical speed. This can eliminate the need to clean the substrate before the adhesion of flux and braze. The particle density inherent to the material used. The particle size preferably is from about 5 to about 50 μm. The supersonic flow of the treatment composition against the substrate develops a shock wave on the surface of the substrate. Typically small particles, ie, smaller than about 5 μm, can not pass through it and never reach the substrate. These small particles generate waste and can contaminate the spray apparatus and the environment. Therefore, it is desirable to use particles which are larger than 5 μm in diameter. The larger particles move more slowly than the smaller particles, and therefore there is an upper limit for the particles used in the present invention, which will experience a supersonic flow. This upper limit is preferably about 50 μm. The particles used in the present invention may be in the form of powders or flakes, the powders being preferred. The gas pressure, the temperature of the gas and the type of gas used in the present invention influence the velocity of the gas and therefore the velocity of the particles entrained within the gas stream. The higher the pressure and temperature of the gas, the higher the resulting speeds. As gas density decreases, gas velocities are increased through the convergent-divergent nozzle. Therefore, the use of helium or a mixture of helium or air (for a given temperature and pressure of gas) will result in higher gas velocities compared to the use of air alone. The preferred gases are air, nitrogen, helium and mixtures thereof. Helium is significantly more expensive than air or nitrogen and therefore, if helium is used, it is preferred to recycle the gas. If the gas is not recycled, then air or nitrogen is preferred. There is a potential explosion when metallic powders are handled; the selection of the composition of the particles and the composition of the gas can be critical from a safety perspective. Inert gases such as helium and nitrogen are advantageous with respect to minimizing the possibility of a potential explosion. Economic factors as well as safety factors influence the selection of gas type, pressure and temperature. Air, nitrogen and recycled helium are all potentially justifiable from an economic perspective. It should also be noted that increasing the temperature of the gas may be more effective in increasing the particle velocities and increasing the gas pressure, although both increase the particle velocities non-linearly. The method of the present invention is suitable for coating metallic articles with flux or flux and a coating layer for brazing purposes. The coatings can be applied to metal substrates such as aluminum alloys, copper alloys, steel alloys, magnesium alloys and nickel alloys. Aluminum or aluminum alloys registered in the Aluminum Association and any non-registered variant thereof can be treated in accordance with the method of the present invention. These include, but are not limited to the aluminum alloys of the series lxxx, 2xxx, 3xxx, 4xxx, 5xxx, 6xxx, 7xxx and 8xxx and any of the records of international associations that are not included in the following. Preferred metal alloys are typically referred to as a brazing sheet and are typically multi-layer composite materials of the 3xxx, 7xxx, 2xxx and 6xxx series alloys, which can be coated with an alloy of the 4xxx series. The articles can be extrusions, coatings or sheets without coating, sheets, plates or sheets. The flow of the treatment composition mixture can be any material capable of removing the oxide layer and which melts below 582 ° C (1080 ° F). A preferred flux is a potassium fluoroaluminate complex. As used herein, potassium fluoroaluminate refers to materials containing the elements potassium, aluminum and fluorine, in proportions such as compounds such as KF, A1F3, KA1F4, K2A1F5, K3A1F6, either alone, double or in combinations and that are present. The composition can be expressed in terms of the elemental composition of 20 to 45% K; 10 to 25% of Al and 45 to 60% of F; or in terms of the concentration of the compounds KF and A1F3 as 40 to 70% of A1F3 and 30 to 70% of KF. These and other suitable fluoroaluminates having the desired flux properties are described in U.S. Patent No. 5,190,596. An example of a commercially sold potassium fluoroaluminate is the Nocolok® flux, other potassium fluoroaluminates such as KA1F4, K2A1F5, K3A1F6 / and mixtures thereof, and potassium fluoroaluminate mixed with one or more of cesium chloride, rubidium chloride, fluoride lithium, cesium fluoride and other alkali metal halide salts to reduce the melting point of the flux. Other fluxes for known aluminum brazing are mixtures of alkali metal or alkaline earth metal chloride and fluorides, ammonium chloride, ammonium fluoride, potassium acid fluoride (KHF2), sodium acid fluoride (NaHF2), ammonium acid fluoride (NH4HF2) , zinc chloride, mixtures of zinc chloride, potassium acid fluoride and ammonium chloride as well as potassium fluorozirconate (K2ZrF6). The flux coating on a brazing surface may be constituted of separate islands of flux on the surface of the metal. This deposition technique allows the melt to adhere to the metal substrate as well as to itself. Consequently, separate flux islands can act as a flux reservoir. Flux deposits can flow to critical areas of the workpiece by gravity or capillary action during the brazing cycle. In the practice of brazing, the treated metal workpiece is heated to temperatures at which the adhering flux material liquefies and flows, providing a broad flux for brazing at specific site positions. The adhesion of the coatings created by these modalities are specifically designed to survive conformation operations and are therefore supplied as a coating on the incoming metallic raw material. This does not prevent its use on work pieces formed in advance. The advantage of supplying the coating on incoming raw materials avoids the need to add flux to work pieces with the work in process, and therefore the entire manufacturing stage is eliminated, which minimizes the use of flux and guarantees the presence of flux on the surfaces that are to be subjected to brazing. It is particularly advantageous for use in workpieces which until now must be added flux before the assembly of the component; for example, plate type heat exchangers (evaporators, plate type heaters, plate type condensers, intercoolers and oil coolers) and subassemblies such as internal baffles in multiples, brazed one-piece manifolds, two-piece manifolds , separators and the like.

The present invention also includes methods for depositing fluxes on a coated or uncoated metal surface in a coating on the surface of a non-reverted metal surface for brazing purposes. Table 1 sets forth the various methods included in the present invention based on the type of particle deposited and the type of metal surface treated.

Table 1 The present invention is suitable for brazing aluminum alloy workpieces, with or without a pre-cleaning step. An aluminum workpiece may be subjected to brazing according to a method having the following steps: (a) providing an aluminum workpiece, the workpiece has a surface for brazing; (b) providing a treatment composition that includes a gas and flux particles for brazing; and (c) spraying the treatment composition onto the brazing surface of the workpiece at a rate by which brazing flux particles are incorporated within the brazing surface to thereby form a flux coating on the surface brazing; and (d) placing the flux-coated workpiece adjacent to another metal workpiece and heating the work pieces to form a brazing joint or joint between the work pieces. Notably in this list of stages no cleaning step is mentioned to remove oils, dirt and the like from the brazing surface prior to the brazing process, although such cleaning can be carried out if desired. If the aluminum workpiece is coated, only the flux or flux encapsulated in metal (to improve adhesion to the coated substrate) needs to be deposited on it, according to the first embodiment of the invention. A flux-containing treatment composition optionally may include metal particles according to the second embodiment of the invention for placing the flux on the surface of the substrate. The speed of the treatment composition sprayed onto the substrate is controlled such that only the metal encapsulated base or flux is deposited on the substrate as described above, ie, from about 200 to about 550 m / sec. This does not prevent the deposition of flux and metal on a coating surface to intentionally modify the nominal composition of the brazing coating by additionally including metal particles, for example by adhering Zn to an Al-Si coating to improve the slaughter potential of the coating. In a typical brazing process, flux is applied to the metal surface before forming or working the workpiece. A forming or assembly operation, or both, may result in part in complex geometries which may have areas that are not easily accessible to a traditional flux adhesion operation subsequent to assembly. The incorporation of the flux adhesion material on the surface of the aluminum brazing workpiece according to the present invention eliminates the need for post-assembly accessibility to essential brazing areas that require flux. Post-assembly flux adhesion operations apply excess flux to the entire assembly, including devices that hold the parts together. This practice results in unwanted and harmful flux residues in assembly areas and corresponding devices. Some of the forming or working operations that are typical in the industry can optionally be applied to the substrate to which the flux has been added. Examples of these operations in hot and cold, stamping, laminate, engraving, preforming, roller forming, pressing, hydroforming and stretching. The substrate material can be heat treated by annealing, heat treatments in solution, aging or cooling either with air or with liquid. After the work piece has been formed, there may be areas of the work piece that benefit from the adhesion of flux but which are not accessible once they are formed. Additionally, a shaped workpiece may have an obtuse shape which increases the difficulty of applying a flux. Previously, excess flux is applied after shaping which often requires an additional downstream blow-off step to remove excess aggregate flux before the brazing step. When the present invention is used, the flux can be applied before shaping and much less flux is applied per work piece (for example by heat exchanger) compared to conventional processes. This results in a product with an improved cosmetic appearance after the brazing process, opportunity for more complex forms in the design of parts subjected to brazing with flux and reduced corrosion of the brazing furnace (due to a reduction in the amount of molten flux). corrosive present in the oven). The flux needs to be applied only in areas where metallurgical joints are necessary. Fortunately, the flux flows at increased temperatures necessary for brazing. Therefore, the specific position of the flux is not highly critical when the underlying surface of the workpiece is treated with the flux using the process of the present invention. Although the surface treatment with the flux may result in a discontinuous flux layer, the layer is substantially uniform in areas where the flux will be needed and will therefore be available for brazing purposes. Approximately the locations where brazing will be required are known, and the present invention provides an opportunity to enrich certain areas of the article with flux. By the same concept, in some other areas where brazing is not desired to occur, unnecessary adhesion of flux can be avoided.

The advantages of using this type of process to coat substrates for brazing applications are many, and include (but are not limited to) excellent adhesion of the coating without the need for a binder, the ability to coat material with a standard laminate cleaning without need of a cleaning step before coating due to the cleaning effects on the periphery of the convergent-divergent nozzle and the ability to selectively coat only the areas that need to be joined. The present invention further includes methods for simultaneously depositing coating material and a flux for brazing onto an uncoated aluminum alloy workpiece. This method includes the steps of: (a) providing an aluminum workpiece, the workpiece has a brazing surface; (b) providing a treatment composition that includes: 1) a gas, ii) brazing flux particles, and iii) metal particles; (c) spraying the treatment composition on the brazing surface of the workpiece at a rate high enough to incorporate the brazing flow particles and the metal particles on the brazing surface to form a metallic coating layer, by which forms a workpiece coated with flux, with a coating layer of metal particles adjacent to the brazing surface; and (d) placing the flux coated and adjacent coated workpiece to another metal workpiece and heating the workpiece to form a flux joint subjected to brazing between the work pieces. The speed of the sprayed treatment composition on the substrate is controlled so that the metal particles and the metal-encapsulated flux or flux are deposited on the substrate as described above, ie, at a rate greater than about 550 m. / sec. The treatment composition may further include transition metal particles (eg, silicon or silicon alloys or mixtures thereof) or transition metal particles encapsulated in metal, or both. High-speed spraying (greater than about 550 m / sec) of particles containing metal or silicon, or metal-coated silicon results in a coating layer thereof on the aluminum substrate which has hitherto been produced in a separate coating process. Some alloys which have a nominal composition that is traditionally difficult or impossible to create via traditional laminate bonding practices can be obtained using the method of the present invention. These alloys, which traditionally can not be subjected to overshoot, have insufficient utility (ie, less than about 15%) to allow lamination bonding.

The present invention contemplates the coating of a metal substrate without the use of a conventional lamination bonding process and includes a method for treating the surface of an aluminum alloy having a ductility less than about 15% by incorporating metal particles on the surface according to the invention. An additional benefit of adding a metal alloy flux according to the invention thereof is a means to identify certain types of alloy and coating weights. A problem in this technique may be that the different alloys and the articles made thereof have similar appearances and can not be separated by visual inspection. Through this process, identification marks can be included within the flux material either by color identification powders or by uniquely marking the metal alloy itself. Then different articles, different sides of the alloy, different coating weights and whether the alloy has been coated or not can be identified. Although the invention has been generally described above, the particular examples provide additional illustration of the product and the typical process steps of the present invention.

EXAMPLES Example 1: Sprayed flux, deposited flux A sample of test material (5.1 x 13 cm) (2 x 5 inches), 0.48 mm (0.019 inches gauge) of an aluminum alloy 4147 is applied as a coating with a flux material, in accordance with the present invention. The flux is a conventional fluoride of aluminum and potassium fluoride or standard Solvay Nocolok ™. The flux is entrained in nitrogen gas at a flow rate of 200 CFM and a pressure of 345 kPa (50 psig). The gas entrained flux is sprayed onto the surface of the aluminum alloy sample through an asymmetric convergent-divergent nozzle. The nozzle is displaced or moved back and forth across the surface to deposit the flux in a row on the substrate. The sample coated with flux is worked by bending the sample at 180 ° around a weak rod with a diameter of 4.8 mm (3/16 inch). Figure 1 shows the aluminum sample after coating. The coating appears as flux islands as well as larger coated flux area. Figure 2 presents the sample after working, the flux remains mostly or largely adhered to the surface of the sample.

Example 2: Flux and sprayed material, only flux is deposited A metal alloy sample, an aluminum alloy 4147, is coated with a flux material according to the present invention. The flux is a mixture of a standard potassium fluoride and aluminum flux, and a 4047 aluminum alloy (which contains 11-13% Si). The flux is entrained in helium gas at a flow rate of a pressure of 200 CFM of 345 kPa (50 psig). The flux entrained with gas is supplied to the surface of the aluminum alloy sample through a converging-divergent axisymmetric nozzle. The nozzle is displaced or turned back and forth across the surface to deposit the flux in rows on the substrate. Figure 3 is a backscattered electronic image of a test panel showing the substrate coated in cross section with a preform polishing plate adjacent thereto. The preform polishing plate appears in the lower portion of the image. The panel is tested to determine the concentration of aluminum (Al), silicon (Yes), potassium (K) and fluorine (F) in both the coating and the substrate, as shown in Figures 4-7. The Al and Si of the coating appear in Figures 4 and 5, respectively. The K and the Fl appear in Figures 6 and 7, respectively, and are the result of a fluoro aluminate potassium flux layer deposited on the test panel. There is an absence of Si and Fe in the coating. Silicon and iron are present in the 4047 powder.

Apparently, 4047 powder is not part of the coating. It will be appreciated that some features of the present invention may change without departing from the present invention. Thus, for example, it should be appreciated that although the invention has been described in terms of a preferred embodiment in which flux particles and an Al-Si alloy or flux and aluminum are sprayed, the materials contemplated by the present invention to be used with the flux include metals, ceramics, transition metals, cermets, semiconductors and polymers. In addition, at lower particle speeds, a wide variety of materials can be intermixed with the flux. Although the preferred embodiments of the present invention have been described above in terms of a silicon-aluminum alloy substrate, it will be apparent to those skilled in the art that metals suitable for use with the present invention are not limited to aluminum and aluminum alloys. aluminum. The present invention will also be useful for applying a flux to any metal or alloy substrate. Other metal substrates such as magnesium, copper, iron, zinc, nickel, cobalt, titanium and alloys thereof can also benefit in the present invention. Although the preferred embodiments of the present invention have been described above in terms of codepositing metal articles and flux particles, it should also be contemplated that the metal particles may be a pure metal, an alloy or a mechanical mixture of metals or alloys. Therefore, the present invention allows the creation of coating chemicals which until now could not be extensively laminated due to the inherent brittleness of the coating material. Although the present invention has been described in terms of a deposited flux, metal can also be deposited. For example, a pure Si or Si-Al alloy can be co-deposited on a bare aluminum substrate to form a coating which replaces the almost traditional authentic Al-Si series 4xxx coating. The resulting coatings made by the present invention also do not require an additional flux addition step since the flux is incorporated into the product at the time of coating. In addition, since the present invention is a finishing step, a limited number of steps is not required by the rolling. It will be readily appreciated by those skilled in the art that modifications may be made to the invention without departing from the concepts described in the foregoing description. Such modifications are also considered to be included within the following claims, unless the claims, by their language, expressly mention it otherwise. Accordingly, the particular embodiments that are described in detail are only illustrative and not limiting of the scope of the invention which is provided with its full scope of the appended claims and any and all equivalents thereof.

Claims (31)

1. A method for treating a surface of a metallic article, characterized in that it comprises the steps of: a) providing a treatment composition that includes a gas and metal halide particles; and b) spraying the treatment composition on a surface of a metal article at a rate high enough to deposit a layer of the metal halide particles on the surface, where the gas is at a temperature from about room temperature to about 500 ° C.

2. The method according to claim 1, characterized in that the metal halide particles are formed from potassium fluoroaluminate.

3. The method in accordance with the claim 1, characterized in that the spraying step of the treatment composition is carried out in such a way that the amount of metallic halide particles deposited is from about 1 to about 12 g / m.

4. The method according to claim 1, characterized in that the treatment composition associated with a velocity greater than about 100 ml / sec up to about 1200 m / sec.

5. The method according to claim 4, characterized in that the gas is selected from the group consisting of air, He, N and mixtures thereof.

6. The method in accordance with the claim 1, characterized in that the treatment composition further includes other particles, the other particles are formed of a material that is selected from the group consisting of metals, metal alloys, transition metals, ceramics, cermets, semiconductors, polymers and combinations of the same.

7. The method according to claim 6, characterized in that the other particles are formed from a metal that is selected from the group consisting of aluminum, silicon, aluminum alloy, silicon alloy and mixtures thereof.

8. The method according to claim 6, characterized in that the ratio of percent volume of metal halide particles to the percent volume of the other particles in the treatment composition is from about 5:95 to about 95: 5.

9. The method according to claim 6, characterized in that the treatment composition is sprayed at a rate by means of which the halide particles are incorporated on the surface of the article and the other particles are not incorporated in the article.

10. The method according to claim 9, characterized in that the speed of the treatment composition is greater than about 100 to about 550 m / sec.

11. The method according to claim 6, characterized in that the treatment composition is sprayed at a rate by which the metal halide particles are incorporated into the surface of the article and the other particles are incorporated into the article.

12. The method according to claim 11, characterized in that the speed of the treatment composition is greater than about 550 to about 1200 m / sec.

13. The method according to claim 6, characterized in that the treatment particles and the delivery particles are from about 2 to about 50 μm in diameter.

14. The method according to claim 1, characterized in that the metal article is formed of a composition that is selected from the group consisting of aluminum alloys, copper alloys, steel alloys, magnesium alloys and nickel alloys.

15. The method in accordance with the claim 14, characterized in that the metal article is formed of an aluminum alloy and of the Aluminum Association series lxxx, 2xxx, 3xxx, 4xxx, 5xxx, 6xxx, 7xxx or 8xxx.

16. The method in accordance with the claim 15, characterized in that the metallic article is formed from a coated aluminum alloy.

17. The method according to claim 11, characterized in that the metal article is formed of an uncoated aluminum alloy.

18. The method according to claim 17, characterized in that a coating layer of the other particles is formed in the aluminum metal article, wherein the coating layer alone has a ductility of less than about 15%.

19. A method of brazing an aluminum alloy workpiece, characterized in that it comprises the steps of: a) providing an aluminum workpiece, the workpiece has a non-fused brazing surface; b) providing a treatment composition that includes a gas and brazing flux particles; c) spraying the treatment composition onto the brazing surface of the workpiece at a rate by which the brazing flux particles are incorporated into the brazing surface whereby a flux coating is formed on the brazing surface; and d) placing the brazing surface coated with flux adjacent to another metal workpiece and heating the work pieces to form a flux gasket subjected to brazing between the work pieces.

20. The method in accordance with the claim 19, characterized in that the flux composition comprises a metal halide.

21. The method in accordance with the claim 20, characterized in that the workpiece is formed of an Aluminum Association 3xxx series alloy.

22. The method according to claim 20, characterized in that the composition of the treatment is sprayed at a higher speed of about 100 to about 1200 m / sec.

23. The method according to claim 19, characterized in that the treatment composition also includes metal particles.

24. The method according to claim 23, characterized in that the treatment composition associated with a speed by which the metal particles are incorporated into the brazing surface to additionally form a coating layer of the metal particles in the workpiece of aluminum adjacent to the brazing surface.

25. The method in accordance with the claim 24, characterized in that the speed of the treatment composition is greater than about 550 to about 1200 m / sec.

26. The method in accordance with the claim 25, characterized in that the metallic particles are formed of a composition selected from the group consisting of aluminum, silicon, aluminum alloy, silicon alloy and mixtures thereof.

27. A method for treating a surface of a metal article, characterized in that it comprises the steps of: a) providing a treatment composition that includes gas and particles, the particles have a core of a metal halide and a coating of a second material, the second material is a metal or an alloy thereof; b) spraying the treatment composition on a surface of a metal article at a sufficient speed whereby the second material adheres to the surface whereby a coating of the first material on the surface is formed.

28. The method in accordance with the claim 27, characterized in that the second material is a coated metal which is selected from the group consisting of Al, Cu, Zn, Mg, Mn, Ni, In, Li and Fe.

29. The method in accordance with the claim 28, characterized in that the speed of the treatment composition is high enough to form a layer of the coating metal on the surface of the metal article.

30. The method in accordance with the claim 29, characterized in that the speed of the treatment composition is greater than about 400 m / sec.

31. The method in accordance with the claim 30, characterized in that the metal article is formed of an aluminum alloy.