Joining Metals

Learning Intention: understand the processes of soldering, brazing, welding, riveting/pop

riveting

Permanent / Temporary

Soldering

• Three Rules of Soldering -• All surfaces must be clean (no grease or dirt),• Both parts must be hot so the solder will flow

towards the heat,• Flux must be used to clean the surface and

encourage the solder to flow.

Flux

• the elevated temperatures required to melt the filler metal (the solder) encourages the work piece (and the solder/brazing rod) to re-oxidize

Joining Metals - Soft soldering

Quick method of joining copper, brass and tinplate when little strength is required in the joint. Also for fixing electronic components

• Soft solder – tin & lead

Silver / Hard Soldering

• Alloys of copper with either zinc or silver. Stronger join. Solder can be filed – soft solder can not.

Brazing – typically for joining steel

• Melting point of filler rod above 450• Very strong join. • Can be used to braze copper and brass but skill is needed.

Welding

• Strongest type of join• The two pieces of metal are melted along the

filler rod, fusing together as they cool..

Welding - oxy-acetylene

• a very hot flame is used

Welding - electric arc welding

• type of welding that uses a welding power supply to create an electric arc between an electrode and the base material to melt the metals at the welding point.

Welding - electric arc welding

Welding - MIG Welding(Metal Inert Gas)

• Commonly used in schools. • A form of electric arc welding but carbon

dioxide gas surrounds the arc and prevents the oxidation of the molten steel. The joint is clean of slag and very strong. The arc is very bright and a protective eye shield must be used..

Welding - MIG Welding (Metal Inert Gas)

Welding - Spot Welding

Welding - Spot Welding

• Spot welding used on sheet steel , stainless steel, Aluminium and light-alloys, galvanized sheets, brass and copper

• Electrodes which are copper tipped are brought together on either side of the joint. When the electric current flows a high temperature is produced, melting the metal at the point of contact. A spot weld is produced

Riveting• components used for joining metal

Riveting• and sometimes plastics and plywood

• A hole is drilled through both pieces of work, the rivet is placed through it, and its end beaten into a dome. A tool called a rivet set or rivet snap is used to finish the joint off neatly. Some rivets are countersunk.

Riveting

Riveting

• With most rivets you need to get at both sides of the work to make the joint. Pop rivets enable you to complete the joint while only having access to one side of the work. They are usually used for joining thin sheets together.

Machine Screws

• Machine ScrewsHave a screw thread to fit into a threaded hole

or a hexagonal nut. They can be used to join two or more pieces of metal or plastic.

Nuts and Bolts

A bolt is only threaded for part of its length. Bolts normally have hexagonal heads.

Set screw• Have a screw thread along the whole or most

of their length, and normally have hexagonal heads

Adhesives