Abstract: A process for treating the surface of a component prior to coating. The component is made from a Ni based superalloy designed for high temperature service. Both the component and the coating include the elements Al and/or Cr. The process includes depleting the outer surface of the component of any one or a combination of Al, Ti or Cr and thereafter applying the coating directly on the depleted surface. The process minimizes the formation of a brittle gamma prime phase within the interdiffusion zone during service of the component. The process can also be used to renew old damaged coatings.

Abstract: A method of joining superalloy substrates together comprises diffusion bonding the superalloy substrates by depositing an activator directly on the surface of the joint to be bonded and thereafter subjecting the joint to heat and pressure. The heat and pressure causes the surface of the superalloy, in the presence of the activator, to diffusion bond without the use of a brazing alloy. By eliminating the brazing alloy, a high strength, high temperature bond is achieved, yet there is no molten brazing alloy to be drawn through capillary action into any fine features surrounding the joint being bonded, and there is no residue left at the interface that would diminish the mechanical properties of the joint.

Abstract: A method and system for cleaning a metal article. The system is used to employ a method that comprises placing the article in a means defining a chamber; subjecting the article to a gaseous atmosphere in the means defining a chamber, where the gaseous atmosphere consisting essentially of carbon, hydrogen, and fluorine; and subjecting the article to the gaseous atmosphere at a temperature in a range from about 815° C. to about 1100° C. to clean the article.

Abstract: A process is described for forming a structure of aluminum sheet components by spot welding the aluminum sheet components. In the process, aluminum sheet components are pretreated in a single step to both clean and increase the surface resistivity thereof by contacting the aluminum sheets with a pretreatment solution comprising a blend of sulphuric acid and phosphoric acid to clean the surface and generate a surface coating acting as a barrier film to increase the surface resistivity of the sheets. Thereafter the sheet components are secured together by spot welding.

Abstract: A method is provided for treating cooperating, juxtaposed substantially uncoated alloy substrate surfaces in preparation for brazing, for example an inner wall of the radially outer open end of a turbine engine blading member with the rim of an end plate or tip cap. The method includes treating at least one of the cooperating surfaces with a reducing gas comprising halogen gas for a time and at a temperature, for example 1-6 hours at 1650-1950° F., sufficient to remove any surface debris, for example oxides, and to deplete the alloy substrate surface of the total of elements selected from Al and Ti to a level of less than about 1 weight %. Depletion is to a depth in the surface which avoids intergranular attack of the substrate alloy surface. For example, the depth is no greater than about 0.0015″. Then the cooperating surfaces are brazed together.

Abstract: The present invention relates to a self cleaning braze paste which is used in the repair of gas turbine engines. The braze paste comprises lithium fluoride in an amount sufficient to act as a flux which allows the braze material to flow into a crack or void in a part to be repaired up to an amount where there is no residual lithium or fluoride in the crack or void, preferably up to about 20% by volume, a gel binder in an amount up to about 15% by volume, and the balance comprising at least one of a nickel braze alloy and a cobalt braze alloy. In a preferred embodiment, the lithium fluoride is present in an amount from about 10% to about 15% by volume. The braze material of the present invention may be applied in a paste form or, alternatively, in a paint or tape form. A method for cleaning and repairing a braze joint is also disclosed.

Abstract: An improved method of manufacturing a piezoelectric element and an improved piezoelectric element are provided. The improved method comprises the steps of causing a gas discharge in a predetermined discharge gas at approximately atmospheric pressure and generating an excited active species of the discharge gas as a result of the gas discharge. Then, at least one of a connecting surface of an electrode formed of a piezoelectric piece on a piezoelectric resonator and a connecting portion of a lead terminal are exposed to the excited active species, whereby the exposed connecting portions are surface treated. Finally, the electrode and the lead terminal are connected together, and at least the electrode and the lead terminal are sealed in a case. The improved piezoelectric element is formed by this process and uses less solder and is more stable than prior art piezoelectric elements.

Abstract: A method and apparatus for uniformly solder plating leads on semiconductor packages wherein the leads are rotated during the solder plating process and the solder on the leads in planarized and solder between and bridging the leads is removed by the application of a hot gas to the device having the leads. The hot gas is preferably N2 which is inert to the process flow at the point in the process when it is utilized.

Abstract: A method of pretreating a copper surface for protecting the surface from oxidation, by immersing the surface in a solution containing organic solderabilty preservatives, such as BenzoTriAzole, with the addition of a zinc salt. The method is particularly useful in the manufacturing of electronic Printed Circuit Boards for protecting the copper surfaces during the solder processes when the PCB undergoes high temperature. The addition of the zinc salts also gives the additional advantage of increasing the solderabilty properties of the copper surface (i.e. wettability and adhesion).

Abstract: At the step of printing a wiring portion of a ceramic substrate with a conductive adhesive for mounting an IC chip or a part such as a capacitor other than the IC chip, a wire bonding pad made of gold is formed by the ball bonding method or the like at the portion of the wiring portion to be wire-bonded. After the pad was formed and before the conductive adhesive is printed, a heat treatment is performed to cause a thermal diffusion between the wiring portion and the pad to improve the jointability therebetween.

Abstract: An upper shearing blade 3 equipped with a protrusion 30 of a triangle-columnar shape and a lower shearing blade 4 equipped with a protrusion 40 of the same shape are applied onto the overlapped portion of metal plates 1 and 2 to be bonded, and then pressed into the metal plates 1 and 2 in an oblique direction inclined with respect to the thickness direction by a stroke in such a range that the metal plates 1 and 2 are not completely cut off. The operating loci of the upper shearing blade 3 and the lower shearing blade 4 are overlapped each other so that one falls inside the other, and the sheared surfaces of the metal plates 1 and 2 are formed into a bonded portion by plastic flow deformation. Therein, since a compressive force is applied onto the portions to be bonded, the portion being defined by the amount of overlap, and the portions are compressed to form a compressed portion after completion of bonding, the bonding strength enhances.

Abstract: A process for the production of a homogenized material of metals and alloys from a slab, and the material has a fine microstructure or fine nonmetallic inclusions and has less segregation of alloying elements.

Abstract: A method of producing sectional strips and sectional sheets of different thicknesses over the width, in which at least two metal strips or metal sheets of different widths are joined to each other by roll bonded cladding which thins the thickness of the overlaid strips. One strip is wider than the other strip which is narrower. The two strips are arranged symmetrically to the rolling direction center line. The facing surfaces of the two overlaid strips may be prepared for bonding them. The invention also concerns sectional strips or sectional sheets produced by the method.

Abstract: Brazing or soldering materials which effectively improve the wettability of the brazing alloy or solder without using flux and a method of manufacturing such materials are provided. A metallic base is placed on turntable inside a vacuum chamber. A copper target is affixed to a sputtering electrode above the metallic base. Air is removed from the vacuum chamber through a vacuum outlet to increase the vacuum therein to a specific pressure, and carbon tetrafluoride and argon are introduced from a gas inlet to control the sputter pressure. Thereafter, turntable is rotated while a high frequency voltage is applied between the target and the metallic base to form a halide layer, such as a layer of copper fluoride, on a surface of metallic base.

Abstract: The present invention provides a joining, brazing or soldering material wherein solderability is effectively improved without using a flux, and a production method thereof. In production of a joining material, a halogen compound is mixed, a film is formed on the surface of a solder molding or the surface of a solder molding is halogenated. In production of a joining material, a halogen compound is added to a solder melt, a film of a halogen compound is formed on the surface of a processed joining material, or the surface layer of the processed joining material is converted to a halogen compound layer by halogenation. Film formation or surface treatment may be carried out either a dry or wet method.

Abstract: High frequency electrical discharge or nonpolar discharge using microwaves is generated in a gas that is introduced into a gas duct formed by a dielectric material, such as glass or ceramic. Surface treatment is applied to the components, which are under atmospheric pressure, by exposing them to the gas flow containing the active species generated by the above mentioned electrical discharge. Components are soldered before, during, or after the application of this surface treatment. The surface of the components is exposed to the active species by either directly exposing the components to the electrical discharge, or by blasting the reactive gas flow containing the active species at them. By selecting an appropriate gas for generating the active species, it is possible to improve the wettability of the surface of the component to be soldered, or to remove the organic substances or the oxide film.

Abstract: Minor additions of calcium (Ca) to Al--(1% to 14%) Si filler metals result in larger fillets than conventional Al--Si alloys normally used in the NOCOLOK brazing process. This new filler metal can be clad to 2XXX, 3XXX, 6XXX, and 7XXX series alloys and brazed with a fluoride flux. The filler metal contains between 0.005% Ca to 0.3% Ca. The new filler metal could have up to 0.3% Mg and up to 0.3% Li. Additionally, the brazing process can optionally include an aqueous treatment with a fluoride salt to reduce the need for NOCOLOK fluxing.

Abstract: An intermetallic bond between a ferrous metal and a non-ferrous metal wherein an intermetallic bond layer that is substantially free of graphic inclusions joins the two. The graphite is effectively eliminated from the bond layer by either removing it from the ferrous metal or by sealing it off from the bond layer. Graphite removal may be accomplished in a variety of ways, including electrochemical cleaning and laser surface treatment. Alternatively, the graphite may be prevented from incursing into the bond region by sealing it off with a layer of metal, such as a chromium plating, that prevents it from penetrating through the bond layer and into the non-ferrous metal.

Abstract: A method for preparing a Ni base superalloy inner wall surface of a body open end, such as an end of a turbomachinery blade, and an end plate, such as a blade tip cap, for brazing together at a rim of the end plate includes electrochemically removing oxides from the inner wall surface. The end plate is prepared, at least at its rim, by first removing surface and subsurface oxides, for example by mechanical abrading or a combination of such abrading and acid cleaning. Then at least the rim is electroplated with Ni which is heated to diffuse the Ni into the rim substrate. This provides an improved combination of surfaces for brazing, for example with a Ni base brazing alloy. After brazing the rim to the inner wall, there is provided an article with an improved relatively low oxide brazed joint, including less than about 20 volume % oxides, and a plate rim of substantially Ni along with elements diffused from the brazing alloy and the rim.

Abstract: A method of making an expanded metal sandwich structure includes cleaning at least two metal superplastic core sheets to remove metal oxides and residues that would interfere with diffusion bonding of the sheets. The core sheets are placed face-to-face and a gas pressure line fitting is inserted between one edge and is welded into place. The fitting has a through bore through which gas can flow under pressure into the space between the core sheets. The core sheets are pressed together and laser welded together into a core pack along lines which will form junction lines between the core sheets when the core pack is superplastically expanded. The core pack and the two metal face sheets having superplastic characteristics are each chemically cleaned, and the face sheets are placed over and under the core pack.

Abstract: A method of forming hydrogen fluoride (HF), to allow fluxless soldering, from a solid source such as potassium hydrogen fluoride (KF.HF) using a specialized apparatus, including a cartridge which is heated in a controlled atmosphere apparatus. The gaseous reaction product, HF, may be extracted from the apparatus either by itself or in a carrier gas (such as argon or nitrogen). The solid reaction product, potassium fluoride (KF), is an inert material which remains in the cartridge. The combination of the cartridge and KF may be safely disposed of as a unit or refilled with KF.HF under controlled conditions.

Abstract: A method for dry fluxing at least one metallic surface of an article comprising the steps of:a) passing at least one initial gas mixture comprising (1) at least one of an inert gas and a reducing gas and (2) an oxidizing gas mixture comprising water vapor into at least one apparatus for forming excited or unstable gas species, the initial gas mixture including 50 ppm to 6% water vapor;b) converting the at least one initial gas mixture to at least one primary gas mixture comprising excited or unstable gas species; andc) treating the surface to be fluxed, at a pressure close to atmospheric pressure, with a gaseous treatment atmosphere comprising excited or unstable gas species and substantially free of electrically charged species obtained from the primary gas mixture.

Abstract: A piezoelectric resonator is provided which is formed of an element piece. This element piece further includes a piezoelectric material and an electrode formed on the surface of the piezoelectric material. A plug for mounting the element piece and a case for housing said element piece in an air-tight manner are also provided. The surface of the element piece is coated with a resin film formed from an excited active species of an organic compound generated through a gas discharge in a predetermined discharge gas at approximately atmospheric pressure. A method of manufacturing a piezoelectric resonator is also provided, which comprises the steps of first mounting the element piece on the plug. Next, a gas discharge in a predetermined discharge gas is produced at approximately atmospheric pressure and an excited active species of an organic compound which is a liquid or a gas at room temperature is generated as a result of this gas discharge in a gas discharge region.

Abstract: Cleaning in periodic acid (H.sub.5 IO.sub.6) aqueous solutions (HI solutions) of particular compositions removes thermally unstable hydrocarbons from the surfaces of semiconductor wafers and enables the direct bonding of semiconductor surfaces such that the bonded interface between these surfaces remains free of bubbles even after heating subsequent to bonding.

Abstract: A process for improving the fillet-forming capability of brazeable aluminum articles includes providing a brazeable aluminum article, having at least one surface; and contacting the surface with a dilute, aqueous solution of fluoridic compounds, for at least 5 seconds at a temperature ranging from about 150.degree. to 212.degree. F. to produce an oxide-free surface which can be readily brazed with a minimal drip loss.

Abstract: High frequency electrical discharge or nonpolar discharge using microwaves is generated in a gas that is introduced into a gas duct formed by a dielectric material, such as glass or ceramic. Surface treatment is applied to components, which are under atmospheric pressure, by exposing them to the gas flow containing the active species generated by the above mentioned electrical discharge. The components are soldered before, during, or after the application of this surface treatment. The surface of the components is exposed to the active species by either directly exposing the components to the electrical discharge, or by directing the reactive gas flow containing the active species at the component surfaces. By selecting an appropriate gas for generating the active species, it is possible to improve the wettability of the surface of the component to be soldered, or to remove organic substances or oxide film surfaces.

Abstract: A method for wave soldering a circuit having two or more faces comprising the steps of:(i) passing at least one initial gas mixture comprising at least one of an inert gas, a reducing gas and an oxidizing gas into at least one apparatus for forming excited or unstable gas species;(ii) converting the at least one initial gas mixture into at least one primary gas mixture comprising excited or unstable gas species and substantially free of electrically charged species;(iii) treating each of the two or more faces of the circuit with the at least one primary gas mixture at a pressure close to atmospheric pressure; and(iv) contacting the two or more faces of the circuit with at least one wave of a liquid soldering alloy.

Abstract: An improved guidewire for advancing a catheter within a body lumen which has a high strength proximal portion, a distal portion formed of superelastic alloy and a connector formed of superelastic alloy to provide torque transmitting coupling between the distal end of the proximal portion and the proximal end of the distal portion. The superelastic alloy elements are preferably cold worked and then heat treated at a temperature well above the austenite-to-martensite transformation temperature, while being subjected to longitudinal stresses equal to about 5 to about 50% of the room temperature yield stress to impart to the metal a straight "memory." The guiding member using such improved material exhibits a stress induced austenite-to-martensite phase transformation at an exceptionally high constant yield strength of at least 70 ksi for solid members and at least 50 ksi for tubular members with a broad recoverable strain of at least about 4% during the phase transformation.

Abstract: A method for preparing a Ni base superalloy inner wall surface of a body open end, such as an end of a turbomachinery blade, and an end plate, such as a blade tip cap, for brazing together at a rim of the end plate includes electrochemically removing oxides from the inner wall surface. The end plate is prepared, at least at its rim, by first removing surface and subsurface oxides, for example by mechanical abrading or a combination of such abrading and acid cleaning. Then at least the rim is electroplated with Ni which is heated to diffuse the Ni into the rim substrate. This provides an improved combination of surfaces for brazing for example with a Ni base brazing alloy. After brazing the rim to the inner wall, there is provided an article with an improved relatively low oxide brazed joint, including less than about 20 volume % oxides, and a plate rim of substantially Ni along with elements diffused from the brazing alloy and the rim.

Abstract: A method is available for wave-soldering component groups, especially printed circuit boards with shielding from the environment, in which lead-free or at least low-lead solders, especially tin solders, with a melting point of more than 210.degree. C., are used. Since in wave soldering the solder bath temperature must usually be set considerably higher than the melting point of the solder, problems with overheating the components are encountered with higher-melting lead-free or low-lead solders. This problem is solved in accordance with the invention by setting a solder bath temperature which is only a few degrees Celsius above the melting point of the solder material, and performing the wave-soldering by the action of a plasma of a process gas atmosphere at low pressure.

Abstract: For fastening a first substrate (11) on a second substrate (21), gallium is selectively deposited on the surface of electrically conductive structures (18) located on the first substrate (11), being deposited in a CVD process upon employment of a metalloorganic compound. After the joining of the substrates (11, 21), the gallium (19) is mixed with a metal (28) that forms a refractory intermetallic phase with gallium, this forming a firm connection between the substrates. The method can be especially utilized for cubic integration.

Abstract: A method for pretreating a solder surface for fluxless soldering is disclosed. The method uses a noble fluorine gas to remove surface oxides from solder surfaces, without the use of external stimulation. A noble fluorine gas is suffused across the solder surface to reduce or eliminate or chemically convert the surface oxides. The process can take place at atmospheric pressure and room temperature. A simple belt driven transport may be used to move the parts past a nozzle which emits the vapor in a system similar to a conventional solder reflow machine.

Abstract: A fluxless soldering method utilizing a strongly internally bonded fluorine containing gas such as hydrogen fluoride (HF). The solder surface is exposed to the gas in place of a flux treatment, resulting in a modified surface layer which allows reflow or joining for an extended period.

Abstract: A wire bonding apparatus has a sealed casing having an opening which can be opened and closed, a device for gas-tightly dividing the casing into first and second chambers, a sealing device that is movable for communicating the two chambers with each other, a device for supplying an inert gas into the first chamber, a device for supplying oxygen gas or ozone gas into the second chamber, a device for connecting an electrode of the substrate to an electrode of the semiconductor chip via the wire in the first chamber, a device for generating glow discharge in the second chamber, and a device for transporting the substrate between the first and second chambers. Wire bonding is immediately performed after impurities are removed from the electrodes by electrical discharge.

Abstract: A method of soldering a copper layer without the use of fluxing agents by exposing the copper layer to a fluorine-containing plasma. Solder is then placed onto the surface of the copper layer and reflowed. Reflow can take place at low temperatures, atmospheric pressure and in an inert or oxidizing atmosphere using standard solder reflow equipment.

Abstract: A method of cleaning a metal surface includes covering the portion of the metal surface with a cleaning tape. The cleaning tape is chromium in combination with a fluoride ion source bound together by fibrillated polytetrafluoroethylene. This is applied to the portion of the area to be cleaned and is subject to heat treatment at about 1800.degree. F. and a reducing atmosphere of preferably hydrogen. This effectively cleans only the area covered by the tape. Further, the tape and binder format acts to force fluoride ions into the cracks on the surface providing a significantly improved cleaning operation.

Abstract: A method is provided for joining Be-Al alloy structural members to yield a high shear strength at the interface. Surface oxides are first removed from the Be-Al alloy members. Aluminum is then selectively etched from the bonding surfaces to allow the flow of braze alloy into high aspect ratio capillary sites. A discontinuous ceramic reinforcing material, such as Al.sub.2 O.sub.3 or SiC in particulate or whisker form, is added in small quantities to a braze foil, such as Al-Si, to create a composite at the bond interface. The braze foil and reinforcing material are sandwiched between the Be-Al alloy members, and the joint is heated to above the liquidus temperature of the braze alloy but below the melting point of aluminum. The resulting interface shear strength of the Be-Al alloy bond has been tested to an average of about 60% of the parent alloy shear strength.

Abstract: In the process according to the invention for soldering electronic boards, in particular, printed circuit boards with devices installed on them, first, during the pickling process, a condensable process material, for example, water, is introduced into flaws in the oxide layers on the soldering connection surfaces and at least partially condensed in the flaws. Then, the oxide layers are exposed to rapid heating such that the process material condensed in the flaws vaporizes explosively and thus the oxide layer breaks up and cracks off of the basis material, such that the soldering connection surfaces for the subsequent actual soldering process are brought to virgin condition. In the case of wave soldering, the rapid heating occurs preferably by means of the wave of solder itself. If non-oxide passive layers must also be removed, this occurs preferably in a preceding stage of the pickling process, during which the oxide layer is hydrophilized. For this, a plasma pretreatment is suitable.

Abstract: The invention is directed to a procedure for processing joints to be soldered, preferably printed circuit boards fitted with electric components, and an arrangement for executing this procedure, wherein the joints are subjected to plasma treatment before the soldering process. The joints may be subjected to plasma treatment separately or in the relative position necessary for the soldering process.

Abstract: The fillet-forming ability of brazeable aluminum alloy materials, such as brazing sheet or heat exchanger components, for example fins, tubes and headers, is significantly improved by treating the material, prior to brazing, with an aqueous acid solution containing a dilute mixture of HF and HNO.sub.3. The treatment generally takes place for a period of not less than 5 seconds within the temperature range from about 15 to about 98.degree. C.

Abstract: A metallized ceramic substrate having an enhanced bond strength between the ceramic substrate and a conductive metal layer bonded thereto is disclosed. The metallized ceramic substrate includes a heterogeneous juncture band between a ceramic workpiece and a layer of electrically conductive material. The metallized ceramic substrate is made by a process which includes an acid etchant step that increases the actual surface area of the treated surface of the ceramic workpiece without undermining the integrity of the ceramic surface while at the same time selectively attacking vitreous binder phase present between substrate grains and creating even deeper penetration at the relatively higher energy triple joint junctures. In this manner, metal anchor sites that enhance adhesion are provided. During subsequent high temperature firing these anchors hold the resulting composite together as a chemical bond is formed in addition to a mechanical bond or interlock.

Abstract: A technique is disclosed for achieving reduced residues on a circuit board (10) following soldering of each conductive member (18) of a component (20) to each corresponding metallized area (12) on the board. At the outset, a layer (22) of low solids solder paste is applied to the metallized areas (12) on the board. Thereafter, an acid is applied to the paste layers (22). Finally, the low solids paste is reflowed while the circuit board (10) is immersed in the inert atmosphere to bond the conductive members (18) of the component (20) to the metallized areas (12) on the circuit board (10).

Abstract: A process for cleaning the surface of aluminides to prepare them for weld by first washing the surface to be welded with a chemical that removes aluminum, an inhibitor to strong welds.

Abstract: A seal between two ceramic articles, or between a ceramic article and a metal article, is formed by providing a sealing member comprising an aluminum body, and a film of zinc or tin being deposited threon, with the inevitable aluminum oxide surface film removed, and subsequently a coating of silver and/or gold, or a suitable alloy containing silver or gold, being provided. The sealing member is positioned between the articles, and the bonding operation comprises heating the assembly in an inert atmosphere, or in a high vacuum, to melt the composite sealing member, there being obviated the need to apply pressure during the bonding operation. Any oxide film on silver readily decomposes at a temperature of, at most, 250.degree. C. No oxide film is formed on gold. The zinc or tin film, and the coating, are readily absorbed into the molten aluminum produced during the bonding operation. Subsequently, the bonded assembly is out-gassed at a temperature up to 600.degree. C.

Abstract: A first surface of a first metal component of an ink jet print head is bonded to a second surface of a second metal component of the ink jet print head, the first and second surfaces being of materials having the same or similar coefficients of thermal expansion. A layer of filler material is electroplated or otherwise placed on at least one of these surfaces. The filler material has a melting point which is below the melting point of the first and second components, and the total thickness of the filler material on the surfaces together is in the range of from approximately one-sixteenth micron to approximately five microns, with one-eighth micron to two microns being a preferred range. These surfaces are placed together and brazed under low pressure. Preferably, the braze pressure is from about one-half psi to no more than about one hundred psi, with about ten psi being most preferred.

Abstract: A method of preparing a surface of a silicon carbide article for joining by metal brazing to metal by micro-roughening that surface of the silicon carbide which is to be brazed, applying catalyst consisting essentially of aqueous PdCl.sub.2 directly to the micro-roughened surface, in the absence of pretreatment of said surface with stannous chloride, and electrolessly depositing a thin layer of metal selected from the group consisting of Ni, Cr, Au, Ag and Cu on said catalyst-treated surface.

Abstract: A method for depositing solder onto aluminum metal material comprises steps of:(a) activating the surface of aluminum metal;(b) substituting zinc for the surface of aluminum as activated;(c) forming a nickel coating film over the surface of the zinc-substituted layer on the aluminum metal material by the non-electrode plating; and(d) attaching soldering material onto the nickel coating film surface.

Abstract: In a compact heat sink the heat exchange surface consists of metal screen which has been crimped in a wave-like form and then brazed to a metal mounting base. The braze is along the trough of the wave where the mesh contacts the base. The base serves as a carrier for attaching the wire mesh to the object requiring heat transfer. The primary application of this form is heat sinking small electronic package such as "flat-packs" etc. An advantage of the design is that it makes a package which is physically compatible with miniature, low static pressure fans. A secondary form described in the disclosure is an air-to-air heat exchanger in which two crimped screens are attached to the base- one on either side. This application is useful for removing heat from a totally enclosed package. In this case the mounting base is larger than the crimped screen to allow for a flange of clear metal around the perimeter of the screen such that it may be attached to a prepared opening in the sealed package.

Abstract: A process is provided in which engine-induced cracks are first converted to weld-induced cracks caused to occur in a chromium halide environment then a braze alloy is brought into contact with the weld-induced cracks and the whole results in a far superior product.

Abstract: The specification discloses an apparatus and method for cleaning printing screens or the like work surfaces in which solvent is pumped from a reservoir to the surface to be cleaned at a point closely adjacent a vacuum cleaning tool. The vacuum cleaning tool is connected by a vacuum line to the reservoir and vacuum means are provided to draw a vacuum on the reservoir whereby solvent is delivered to the surface to be cleaned and residue laden solvent is vacuumed off the surface to be cleaned through the vacuum tool and vacuum line. A clean up tray and light panel are provided to facilitate the clean up operation. A control assembly comprising independently or simultaneously actionable foot pedals for control solvent feed and vacuum is provided.