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

NP

P

P

P

P

P

P

P

P = Permanent

NP = Non-permanent

JOINING PROCESSESMECHANICALScrew FastenersThese 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 PROCESSESMECHANICALScrew FastenersWoodscrews

JOINING PROCESSESMECHANICALScrew FastenersWoodscrews

Wood Screw Pozi Head CSK Wood Screws Round Head Slotted

JOINING PROCESSESMECHANICALScrew FastenersFurniture Screws

Furniture Screws & ‘Knock Down’ fittings

JOINING PROCESSESMECHANICALScrew FastenersKnock Down Fittings

JOINING PROCESSESMECHANICALSelf Drilling/Tapping Screws

JOINING PROCESSESMECHANICALMachine Screws

JOINING PROCESSESMECHANICALBolts

Hexagon Socket HeadHexagon Flange BoltsChrome Hexagonal Bolts

JOINING PROCESSESMECHANICALNuts & Washers

JOINING PROCESSESMECHANICALCompression Fittings

Straight Coupling Equal TeeUsed primarily in plumbing applications

JOINING PROCESSESMECHANICALPop Rivets

Pop Riveting Tool with Threaded Inserts

This is a permanent joining process

JOINING PROCESSESMECHANICALRivets

These are used for permanent joints in steel plate

Snap Head Rivet Countersunk Rivet

JOINING PROCESSESMETALURGICALSoldering

Electric Cable

Replaceable TipInsulated Handle

Electric Soldering Iron

JOINING PROCESSESMETALURGICALSoldering

Soldering Iron Stand Soldering Wire

JOINING PROCESSESMETALURGICALSoldering a Component on A Circuit Board

Soldering Iron

Circuit BoardFoil

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 PROCESSESMETALURGICALSoldering 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 PROCESSESMETALURGICALSoldering 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 PROCESSESMETALURGICALBrazing

Brazing Hearth

Brazing Torch

Firebrick

JOINING PROCESSESMETALURGICALBrazing

Brazing Torch

Brazing Rod (Spelter)

Whole of joint area is heated and it is the heated joint that melts the Spelter

JOINING PROCESSESMETALURGICALBrazing

Typical Brazing Applications

JOINING PROCESSESAdhesivesNatural AdhesivesThese are made from natural ingredients rather than being fabricated synthetically from chemicals.

Sources•Animal based•Fish based•Vegetable based

JOINING PROCESSESAdhesivesNatural AdhesivesSome natural adhesives have the following properties, they can be;•Strong•Flexible•Waterproof•Soluble in water•TransparentHowever they are not as strong as synthetic adhesives and are usually more expensive

JOINING PROCESSESAdhesivesNatural AdhesivesAre 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 PROCESSESAdhesivesElastomer AdhesivesAre based on natural and synthetic rubbers. They set by solvent evaporation or heat curing. Used for flexible bonds in plastics and rubber

Type Description MaterialsNatural Rubber Water resistant Rubber, plastics, steel,

fabrics, wood, glass

Neoprene Contact adhesive Wood, metal, leather, plastics

Butyl Rubber Tyre repairs Rubber products

Polyurethane High strength joint Glass, polyurethane, plastic, metals

Silicone Rubber Sealant, space filling, water resistant, glazing

Silicone, glass, metals

JOINING PROCESSESAdhesivesThermoplastic AdhesivesAre fusible, soluble but with poor heat and creep resistance

Type Description MaterialsPolyvinyl Acetate (PVA) Emulsion type wood glue,

poor resistance to waterWood, metal, glass, ceramics

Cyanoacrylates Hardens in seconds based on catalytic action

Metal, plastics, ceramics, etc

Polyamines Applied hot – sets on cooling (hot glue gun)

Metal, wood, plastics, laminates

Anerobic Acrylic Acid Diesters

Locking and sealing nuts and threaded parts

Metals

JOINING PROCESSESAdhesivesThermoset AdhesivesHigh strength, suitable for high load assemblies and resistant to heat and cold. Comparable with the strength of welded or riveted joints

Type Description MaterialsResorcinol Resins Used in exterior plywood Wood and other porous

materials

Polyesters (unsaturated) Hardens by chemical reaction, not evaporation – very little shrinkage

Binder for fibre glass

Epoxy Resin 2-part, high strength, little shrinkage

Metal, glass, elastomers, some plastics

Redux© adhesive (brand name)

High performance, aerospace, marine, automobiles

Metals

JOINING PROCESSESAdhesivesToughened AdhesivesResearch 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