308A Metal Types and Properties

Question 1

What is the most commonly used metal for HVAC ductwork fabrication?

Accepted Answer

Galvanized steel

Answer

Copper

Answer

Stainless steel

Answer

Aluminum

Question 2

What is the purpose of the zinc coating on galvanized steel?

Accepted Answer

To provide sacrificial corrosion protection — the zinc corrodes before the base steel

Answer

To make it look shiny

Answer

To increase the weight

Answer

To make it easier to weld

Question 3

What gauge system is used for sheet metal thickness in Canada, and how does the gauge number relate to thickness?

Accepted Answer

Lower gauge numbers indicate thicker metal — 16 gauge is thicker than 24 gauge

Answer

Higher gauge numbers mean thicker metal

Answer

All gauge numbers represent the same thickness

Answer

Gauge is measured in pounds per square foot

Question 4

What type of stainless steel is most commonly used in sheet metal work and what makes it 'stainless'?

Accepted Answer

Type 304 (18-8), containing at least 18% chromium and 8% nickel that form a passive oxide layer

Answer

Type 100, containing lead

Answer

Type 500, containing copper

Answer

Type 700, containing tin

Question 5

What is the primary advantage of using aluminum sheet metal for certain applications?

Accepted Answer

It is lightweight (about 1/3 the weight of steel) and naturally corrosion-resistant

Answer

It is the strongest metal available

Answer

It is cheaper than all other metals

Answer

It is the easiest metal to weld

Question 6

What does the term 'temper' refer to in sheet metal materials?

Accepted Answer

The hardness and strength condition of the metal, determined by the degree of cold working or heat treatment

Answer

The temperature of the metal during installation

Answer

The colour of the metal

Answer

The age of the metal