Materials Technology Joining Processes

Overview – Joining Materials OPTION The student will learn about… The methods by which materials are joined – permanent and semi-permanent techniques The student will be able to… Demonstrate a knowledge of the main methods of joining materials – metallurgical processes, mechanical joining and adhesive/chemical bonding

Overview – Joining Processes JOINING TECHNIQUES Metallurgical Brazing Soldering Mechanical Screw Fasteners Compression Joints Riveting Sheet Metal Folding Adhesive Natural Elastomer Thermoplastic Thermoset Toughened P P NP P P P P P P P P = Permanent NP = Non-permanent

JOINING PROCESSES MECHANICAL Screw Fasteners These are non-permanent methods of joining materials. There is a very wide variety of screw fasteners available they include; Woodscrews Self-drilling/tapping screws Machine screws Furniture screws Bolts Compression Joints

JOINING PROCESSES MECHANICAL Screw Fasteners Woodscrews

JOINING PROCESSES MECHANICAL Screw Fasteners Woodscrews Wood Screw Pozi Head CSK Wood Screws Round Head Slotted

JOINING PROCESSES MECHANICAL Screw Fasteners Furniture Screws Furniture Screws & ‘Knock Down’ fittings

JOINING PROCESSES MECHANICAL Screw Fasteners Knock Down Fittings

JOINING PROCESSES MECHANICAL Self Drilling/Tapping Screws

JOINING PROCESSES MECHANICAL Machine Screws

JOINING PROCESSES MECHANICAL Bolts Hexagon Socket Head Hexagon Flange Bolts Chrome Hexagonal Bolts

JOINING PROCESSES MECHANICAL Nuts & Washers

JOINING PROCESSES MECHANICAL Compression Fittings Straight CouplingEqual Tee Used primarily in plumbing applications

JOINING PROCESSES MECHANICAL Pop Rivets Pop Riveting Tool with Threaded Inserts This is a permanent joining process

JOINING PROCESSES MECHANICAL Rivets These are used for permanent joints in steel plate Snap Head RivetCountersunk Rivet

JOINING PROCESSES METALURGICAL Soldering Electric Cable Replaceable Tip Insulated Handle Electric Soldering Iron

JOINING PROCESSES METALURGICAL Soldering Soldering Iron StandSoldering Wire

JOINING PROCESSES METALURGICAL Soldering a Component on A Circuit Board Soldering Iron Circuit Board Foil Component Lead The soldering iron tip is placed against the lead and the circuit board foil. Both are heated for 3 or 4 seconds

JOINING PROCESSES METALURGICAL Soldering a Component on A Circuit Board Cored Solder Wire The solder is applied to the lead opposite the soldering iron. It is the heated lead and circuit board foil that melts the solder

JOINING PROCESSES METALURGICAL Soldering a Component on A Circuit Board Molten Solder As the solder melts it flows around the connection and forms a good conductive joint with the foil. The soldering wire and the soldering iron are then withdrawn and the joint is allowed to cool

JOINING PROCESSES METALURGICAL Brazing Brazing Hearth Brazing Torch Firebrick

JOINING PROCESSES METALURGICAL Brazing Brazing Torch Brazing Rod (Spelter) Whole of joint area is heated and it is the heated joint that melts the Spelter

JOINING PROCESSES METALURGICAL Brazing Typical Brazing Applications

JOINING PROCESSES Adhesives Natural Adhesives These are made from natural ingredients rather than being fabricated synthetically from chemicals. Sources Animal based Fish based Vegetable based

JOINING PROCESSES Adhesives Natural Adhesives Some natural adhesives have the following properties, they can be; Strong Flexible Waterproof Soluble in water Transparent However they are not as strong as synthetic adhesives and are usually more expensive

JOINING PROCESSES Adhesives Natural Adhesives Are often used in furniture and architectural restoration projects They are also friendlier to the environment; No chemicals released into the soil or atmosphere in production or use No aggravation of chemical based allergies Manufactured from renewable resources

JOINING PROCESSES Adhesives Elastomer Adhesives Are based on natural and synthetic rubbers. They set by solvent evaporation or heat curing. Used for flexible bonds in plastics and rubber TypeDescriptionMaterials Natural RubberWater resistantRubber, plastics, steel, fabrics, wood, glass NeopreneContact adhesiveWood, metal, leather, plastics Butyl RubberTyre repairsRubber products PolyurethaneHigh strength jointGlass, polyurethane, plastic, metals Silicone RubberSealant, space filling, water resistant, glazing Silicone, glass, metals

JOINING PROCESSES Adhesives Thermoplastic Adhesives Are fusible, soluble but with poor heat and creep resistance TypeDescriptionMaterials Polyvinyl Acetate (PVA)Emulsion type wood glue, poor resistance to water Wood, metal, glass, ceramics CyanoacrylatesHardens in seconds based on catalytic action Metal, plastics, ceramics, etc PolyaminesApplied hot – sets on cooling (hot glue gun) Metal, wood, plastics, laminates Anerobic Acrylic Acid Diesters Locking and sealing nuts and threaded parts Metals

JOINING PROCESSES Adhesives Thermoset Adhesives High strength, suitable for high load assemblies and resistant to heat and cold. Comparable with the strength of welded or riveted joints TypeDescriptionMaterials Resorcinol ResinsUsed in exterior plywoodWood and other porous materials Polyesters (unsaturated)Hardens by chemical reaction, not evaporation – very little shrinkage Binder for fibre glass Epoxy Resin2-part, high strength, little shrinkage Metal, glass, elastomers, some plastics Redux© adhesive (brand name) High performance, aerospace, marine, automobiles Metals

JOINING PROCESSES Adhesives Toughened Adhesives Research has led to the development of high strength, toughened adhesives. They have small rubber-like particles dispersed throughout the glassy matrix. This gives the adhesive a high resistance to crack formation