Joining Metals

8/13/2019 Joining Metals

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Joining Metals


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2 Main Types

Temporary - when access will be needed at

some time in the future

Permanent - when a joint will never need to

be undone


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Nut and Bolt

Temporary fixing when

both sides can beaccessed


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Machine Screw

Temporary fixing when

access is from one sideonly


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Riveting Countersink and Round HeadRivets make a permanentfixing. Usually the head is

formed on the other side which

is the same as the original one.

Round Head rivets use a Snap

and Set to form new head, and

protect original.

If loose joints are required - insert

a piece of card between the pieces

and remove on completion


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Soldering

Soldering is the joining of pieces of metal with a different

metal which is melted between the pieces. The pieces being

joined do not melt.

2 typesSoft Soldering

Electrical

Gas

Hard Soldering Brazing

Silver Soldering


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Electric Soft Soldering

Use an electric soldering iron

Solder

Tin/Lead alloyFlux

Resin contained within the solder

Use soldering electronic components


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Soft Soldering

Use a small gas oven or blow torch and copper soldering

irons


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Soft Soldering

Solder

Tin/Lead alloy, called Tinmans Solder

Flux Zinc Chloride, separate from solder

Use

Soldering tin plate containers

copper water pipes (mostly pre-prepared and just needwarming)


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Brazing

Used to join Mild Steel (mainly)

Work is heated in the forge with a natural

gas/air flame

Solder

Brazing Rod (a brass alloy)

Flux

Borax, mixed to a paste with water, or

brazing rod dipped in powder flux


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Silver Soldering

Used to join silver or other non-ferrous metals

Work is heated in the forge with a natural gas/air flame

Solder

Silver solder -a silver alloy with a lower melting point thansolid silver

Flux

Borax, as brazing

UseUsed to assemble items that will be hallmarked. Silver solder

must contain a high percentage of silver or it will not be

hallmarked.


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Welding

Welding is the joining of metals by melting

the two pieces to be joined and fusing them

together with the addition of welding rodwhich is the same as the metal being

welded.

e.g. when welding mild steel the weldingrod is mild steel


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Different Types of Welding

Gas (oxy-acetylene)

Arc

Spot

MIG (Metal Inert Gas)

TIG (Tungsten Inert Gas)


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Oxy-Acetylene Welding

Flame is a mixture of oxygen and acetylene, supplied in gas

bottles


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Arc Welding

Uses the heat from a spark jumping between

the welding rod and work, completing a

circuit.

The welding rod is Mild Steel coated with

flux which melts as welding is done. It has

to be chipped off after.

Arc welding is becoming rarer as MIG

welding is much easier


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Spot Welding

Used to join sheet mild steel.

Does not distort the metal as it is only

heated in a small area.

Used to assemble car bodies.


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Metal Inert Gas

Used to weld Mild Steel

Welding rod is fed automatically through

the gun.

No flux is needed as the joint is protected

from the atmosphere by a shield of Inert

Gas (argon)

Much cleaner than arc welding


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Tungsten Inert Gas

Uses the same principle as MIG but the

welding rod is not fed automatically.

The tip of the welding gun is made oftungsten, and the welding rod is fed by

hand.

Used to weld aluminium and StainlessSteel.


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Now its your turn

In your exercise books

Sketch the process of forming a round head

rivet

Sketch a copper soldering iron

Describe the advantages of MIG welding

over Arc Welding


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Forming a Round Head Rivet


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A Copper Soldering Iron


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Advantages of MIG over Arc

No flux to chip off afterwards

Welding rod is fed automatically

Greater control with MIG. Arc very difficult

with a new rod, because of its length.

Joining Metals

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