materials technology joining processes. overview – joining materials option the student will learn...

Materials Technology

Joining Processes

Overview – Joining Materials

OPTIONThe 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 PROCESSESMECHANICAL

Screw Fasteners

Woodscrews


Screw Fasteners

Woodscrews

Wood Screw Pozi Head CSK Wood Screws Round Head Slotted


Screw Fasteners

Furniture Screws

Furniture Screws & ‘Knock Down’ fittings


Screw Fasteners

Knock Down Fittings


Self Drilling/Tapping Screws


Machine Screws


Bolts

Hexagon Socket HeadHexagon Flange Bolts

Chrome Hexagonal Bolts


Nuts & Washers


Compression Fittings

Straight Coupling Equal Tee

Used primarily in plumbing applications


Pop Rivets

Pop Riveting Tool with Threaded Inserts

This is a permanent joining process


Rivets

These are used for permanent joints in steel plate

Snap Head Rivet Countersunk Rivet

JOINING PROCESSESMETALURGICAL

Soldering

Electric Cable

Replaceable TipInsulated Handle

Electric Soldering Iron


Soldering

Soldering Iron Stand Soldering Wire


Soldering 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



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



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 The soldering wire and the soldering iron are then withdrawn and the joint is allowed to cool


Brazing

Brazing Hearth

Brazing Torch

Firebrick


Brazing

Brazing Torch

Brazing Rod (Spelter)

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


Brazing

Typical Brazing Applications

JOINING PROCESSESAdhesives

Natural Adhesives

These are made from natural ingredients rather than being fabricated synthetically from chemicals.

Sources•Animal based•Fish based•Vegetable based


Natural Adhesives

Some 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


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


Elastomer 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


Thermoplastic 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


Thermoset 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


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

materials technology joining processes. overview – joining materials option the student will learn...

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