AQA GCSE Engineering 8852: manufacturing processes (joining and assembly)

spec ref: 3.2.5 textbook ref: ch2.5 pages 56-58

What are the two types of joining methods?

Permanent and temporary

What is a permanent joining method?

A joint that cannot be easily taken apart without damage

What is a temporary joining method?

A joint that can be taken apart without damaging components

What is a rivet?

A permanent mechanical fastener that joins materials by deforming a metal pin

Properties of riveted joints

Strong, permanent, no heat required

Uses of rivets

Aircraft structures, bridges

What is a threaded fastening?

A temporary joining method using screws, nuts or bolts

Advantages of threaded fastenings

Can be disassembled, reusable, adjustable

Uses of threaded fastenings

Machinery, structures, assemblies

What is soldering?

A joining process using a filler metal without melting the base metals

What is soft soldering?

A low temperature soldering process (below ~450°C)

Properties of soft soldering

Weak joint, low melting point, used for delicate work

Uses of soft soldering

Electronics, circuit boards

What is hard soldering?

A high temperature soldering process (silver soldering)

Properties of hard soldering

Higher strength than soft soldering, uses higher temperatures (620-740°C)

What is used in hard soldering?

Silver-based alloy filler and flux

Why is flux used in soldering?

Prevents oxidation and improves bonding

Uses of hard soldering

Jewellery, stronger joints than soft soldering

What is brazing?

A joining process using a filler metal melted above 450°C without melting base metals

Properties of brazing

Stronger than soldering, lower temperature than welding

Temperature range of brazing

Approximately 450-1200°C

Why must surfaces be cleaned before brazing

To remove oxides, grease and dirt for a strong joint

Uses of brazing

Pipe joints, metal assemblies

What is welding?

A joining process where base metals are melted to form the joint

Properties of welding

Very strong joint, permanent, high temperatures (>3000°C)

What is the key difference between welding and brazing?

Welding melts the base metals; brazing does not

What is oxyacetylene welding?

Welding using a flame from burning acetylene with oxygen

What is TIG welding?

Uses a non-consumable electrode with separate filler metal

What is MIG/MAG welding?

Uses a consumable electrode that melts to form the filler

What is arc welding?

Welding using an electric arc to generate heat

What is a weld pool?

The molten area formed during welding

Why is shielding gas used in welding?

To prevent oxidation and contamination of the weld

What happens in MMA welding?

Flux covers the weld and must be removed after cooling

Why is welding stronger than soldering and brazing?

The base metals are fused together

Advantages of welding

Strong, permanent, suitable for structural applications

Disadvantages of welding

High temperature, safety risks, not easily reversible

Advantages of soldering

Low temperature, easy, suitable for delicate components

Disadvantages of soldering

Weak joints, not suitable for high loads

Advantages of brazing

Stronger than soldering, joins dissimilar metals

Disadvantages of brazing

Requires high temperature and preparation

Behaviour during joining (machining link)

Materials must be clean; heat can affect properties

What is flux?

A chemical used to prevent oxidation during joining processes

Which joining methods use a filler metal?

Soldering, brazing and welding (sometimes)

How does a rivet form a joint?

The rivet is inserted and then deformed to form a second head, clamping materials together

Why are rivets permanent?

They cannot be removed without destroying the rivet

What types of threaded fastenings are there?

Bolts, screws and nuts

What is the key difference between hard soldering and brazing?

Hard soldering uses a silver-based filler at lower temperatures (≈620-740°C), while brazing uses a wider range of filler metals at higher temperatures (≈450-1200°C)

Can brazing join dissimilar metals?

Yes, brazing can join different types of metals

Can welding join dissimilar metals easily?

No, welding usually joins similar metals

Which joining methods require surface cleaning before joining?

Soldering, brazing and welding

Which joining methods use heat?

Soldering, brazing and welding

Which joining method does NOT use heat?

Riveting and threaded fastenings