PowerPoint PresentationBrazingFiller MetalsFluxesBrazing MethodsSlide 6Other Types Of BrazingBraze WeldingBrazing Process CapabilitiesGood/Poor DesignsSolderingReflow SolderingWave SolderingTypes Of FluxesAdhesive BondingTypes of adhesivesAdhesive Peeling TestJoint Design in Adhesive BondingConfigurations for adhesive bondsMechanical FasteningRivetsJoining PlasticsTHE ENDChapter 30Brazing, Soldering, Adhesive, Bonding& Mechanical Fastening processBrazing•Joining process•A filler metal is placed between two workpieces and heated until melted•Two main types of Brazing–Ordinary–Braze welding•Use of flux is very importantFiller Metals•Available in a wide range of brazing temperatures•They come in a wide range of shapes•Choice of the filler metal and its composition are important•Diffusion of the filler metal in to the workpeice is an important considerationFig: a) Brazing b) Braze welding operationFluxes•The use of flux in brazing is very important •Generally made of:–Borax–Boric acid–Borates–Fluorides–Chlorides•Wetting agents may also be addedBrazing Methods•Torch Brazing–Performed by heating the joint with a torch–Depositing the filler metal in the joint–Suitable part thickness (0.25 – 6.0)mm–Not a automated process–More than one torch can be used in this process•Furnace Brazing–Precleaned & Preloaded with brazing metal–Heated in a furnaceFig:An example of furnace brazing a)before b) afterBrazing MethodsOther Types Of Brazing•Induction Brazing•Resistance Brazing•Dip Brazing•Infrared Brazing•Diffusion BrazingBraze Welding•Prepared like fusion welding•Filler metal is deposited at the joint with the use of an oxyacetylene torch•Considerably more filler is used•Temperature is minimal compared to that of fusion welding; part distortion is minimalBrazing Process Capabilities•Dissimilar metals can be assembled with good joint strength•Shear strength of brazed joints can reach 800MpaFig:Joint Designs commonly used in brazing operations.The clearance between the two parts being brazed is an important factor in joint strength.If the clearance is to small, the molten braze metal will not fully penetrate the interface.Good/Poor DesignsSoldering•Different types of soldering–Torch–Furnace–Iron–Induction–Resistance–Dip–Infrared–Ultrasonic–reflow (paste)–WaveReflow Soldering•Solvents present in the paste are evaporated•The Flux in the paste is activated and the fluxing action occurs•The components are carefully preheated•The solder particles are melted and wet the joint•The assembly is cooledWave Soldering•Popular approach to attaching circuits to circuit boardsFig: a)Screening or stenciling paste onto a printed circuit board: 1) Stenciling process 2) a section of a typical stencil pattern b) wave soldering processTypes Of Fluxes•Inorganic acids or salts – clean the surface rapidly•Noncorrosive resin-based – used in electrical applications•Soldering is used extensively in electronics industryAdhesive Bonding•Products are joined and assembled by the use of Adhesives•Adhesives properties to be considered–Strength–Toughness–Resistance to various fluids–Ability to wet the surface to be bondedTypes of adhesivesSurface must be clean for joining parts•Should avoid joints that might be subjected to peeling forces•Design for adhesive bondingAdhesive Peeling TestFig : Characteristic behavior of (a) brittle (b) tough adhesive in a peeling testJoint Design in Adhesive BondingFig:Various joint design in adhesive bonding.Configurations for adhesive bondsFig : (a) single lap (b) double lap (c) scarf (d) strapMechanical Fastening•Threaded Fasters–Bolts–Screws–Nuts•Other Fastening Methods–Stapling–Crimping–Snap-in Fasteners–Shrink and press fitsRivetsFig:a)solid b)tubular c) split (bifurcated) d) compressionFig : Design guidelines for riveting (a)Exposed shank is too long; the result is buckling instead of upsetting (b)Rivets should be placed sufficiently far from edges to avoid stress concentrations (c)Joined sections should allow ample clearance for riveting tools (d) section curvature should not interfere with the riveting processJoining Plastics•Heat softens the plastic to a molten state•Then pressure added & fusion takes place•External Heat Sources–Hot air–Heated tools & dies–Electrical-Resistance–Lasers•Internal Heat Sources–Ultrasonic welding–Friction weldingTHE
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