Metals

Question 1

Iron ore is the basis for most steals, how is pure iron extracted?

Answer 1

Iron ore is heated in a furnace in a process known as smelting.

Question 2

Name two primary processes of metal

Answer 2

Rolling and extrusion.

Question 3

How does the rolling process work?

Answer 3

The metal is heated until it is malleable. It is then squeezed between two special rollers. If a flat sheet is required, the rollers are circular. For a required shape, the rollers are shaped into dies. Each roller or die is slightly smaller than the previous one so that each time the metal passes through a die, it is reduced closer to the desired profile.

Question 4

How does extrusion work?

Answer 4

Extruding involves pushing heated material through a die with the use of a ram. The ram creates a large pressure behind the material and it is quickly forced out of the die. The metal coming through the die needs supporting and cooling so that it does not lose its shape. Extrusions tend to be long thin parts with a constant profile such as window frames.

Question 5

Name five stock forms of metals

Answer 5

Flat strip, round tube, hexagonal, channel, sheet.

Question 6

What are the properties of ferrous metals?

Answer 6

• Contain iron.
• Will corrode and less protected.
• Are attracted by a magnet.
• Are strong, rigid and cheap.

Question 7

Describe cast iron?

Answer 7

• It is composed of iron + 3% carbon.
• It is used for car brake discs, vices and the machine parts and fireplaces.
• It is brittle, can’t be forged or bent, strong in compression.
• It melts at 1200°C.

Question 8

Describe mild steel

Answer 8

• It is composed of iron + 0.15–0.25% carbon.
• It is used for car bodies, structural beams, nuts and bolts.
• It is malleable, tough, ductile, good in tension, corrodes easily.
• It melts at 1600°C.

Question 9

Describe high carbon steel

Answer 9

• It is composed of iron + 0.7–1.5% carbon.
• It is used for hammers, chisels, screwdrivers, scribers.
• It is very hard, difficult to cut, not very malleable.
• It melts at 1800°C.

Question 10

What are ferrous metals?

Answer 10

Metals obtained from iron ore, they contain iron.

Question 11

What are non-ferrous metals?

Answer 11

Metals that do not contain iron.

Question 12

What are the properties of non-ferrous metals?

Answer 12

• Do not contain iron.

- Are not attracted by a magnet.

Question 13

Describe aluminium

Answer 13

• It is a pure metal.
• It is used for cans, foil and window frames.
• It is malleable, soft ductile, corrosion resistant and it difficult to join.
• It’s a melts at 600°C.

Question 14

Describe zinc

Answer 14

• It is a pure metal. It is used for corrosion proof coating for mild steel and die casting alloys.
• It melts at 420°C.

Question 15

Describe copper

Answer 15

• It is a pure metal.
• It is used for pipework, electrical wires and the central heating cylinders.
• It is malleable, has good heat and electrical properties and corrosion resistant.
• It melts at 1083°C.

Question 16

Describe tin

Answer 16

• It is a pure metal.
• It is used for coating on the cans and allied with other materials for solder.
• It is ductile, has a low melting point, is extremely resistant to corrosion.
• It melts at 230°C.

Question 17

What are alloys?

Answer 17

Metals that are made up of two or more metals and other elements. This is done to improve their properties.

Question 18

What can alloying metals do?

Answer 18

• Lower the melting point.
• Alter thermal and electrical properties.
• Make a material harder for cutting purposes.
• Improve resistance to corrosion.
• Help metal to flow better into a cast.

Question 19

Describe brass

Answer 19

• It is composed of 60% copper and 40% zinc.
• It is used for ornaments, plumbing fittings, furniture hardware.
• It is corrosion resistant, polishes very well and easily joined.
• It melts at 950-1000°C.

Question 20

Describe stainless steel

Answer 20

• It is composed of carbon steel + 18% chromium, 8% nickel and 8% magnesium.
• It is used for kitchen utensils, sinks and surgical instruments.
• It is resistant to wear and tear, durable, tough and hard.
• It melts at 1400°C.

Question 21

Describe high speed steel

Answer 21

• It is composed of medium carbon steel plus high content of tungsten, chromium and vanadium.
• It is used for drill bits and cutting tools.
• It is very hard, brittle but extremely durable.
• It melts at 1400°C.

Question 22

Describe pewter

Answer 22

• It is composed of 80% tin and 20% lead.
• It is used for Jewelry, decorative work and tankards.
• It is malleable, easily cast and polishes well.
• It melts at 230°C.

Question 23

What are the definitions for the properties of metals?

Answer 23

• Durability - ability to withstand general wear and tear.
• Electrical - how well a material conducts or insulates electrical current.
• Toughness - ability to withstand sudden impact without fracturing.
• Hardness - ability to withstand dents and abrasive wear.
• Malleability – how workable a metal is.

Question 24

Name three elements that can be added to a metal and a benefit it offers

Answer 24

• Manganese – improves toughness and hardness.
• Tungsten – allows steel to be cut at high strength.
• Chromium – increases resistance to wear and tear, improves durability.

Question 25

Name three types of heat treatment

Answer 25

- Heated and rapidly cooled – hardening steel. This can only be carried out on steels with a carbon content of less than 0.35%. - Tempering - steel is reheated to between 230°C and 300°C and then quickly called with water. This process will make a material slightly tougher. - Annealing - The softening of metals so they can be worked.

Question 26

Name and describe two industrial processes

Answer 26

- Milling machines are used to remove thin layers from a billet (block of material) which is clamped to the bed of the machine. The material is fed past a cutting tool which has many sharp teeth and can remove material quickly. - Centre lathes are used to make cylindrical products. Metals and plastics can be used on this machine. The work is held in a chuck and a cutting tool is moved towards the work while being held in a tool holder, mounted on the tool post.

Question 27

What are four finishing techniques that can be used on metals

Answer 27

- Paint - Lacquering - Plastic coating - Enamelling

Question 28

Describe paint as a finishing technique for metal

Answer 28

- Surface must be smooth and de-greased. - Primer is required. - Hammerite is a good one-coat metal paint.

Question 29

Describe Lacquering as a finishing technique for metal

Answer 29

- Helps to prevent corrosion after polishing. - A layer of cellulose or varnish is applied. - Often used on jewellery.

Question 30

Describe plastic coating as a finishing technique for metal

Answer 30

- It is suitable for most metals. - Object is heated and dipped in a tank of powder paint. - Object is returned to oven to ensure a smooth, glossy finish.

Question 31

Describe enamelling as a finishing technique for metal.

Answer 31

- Powdered glass is melted onto the metal surface. | - Provides a hard but brittle finish with different colours and textures.

Question 32

Where do metals come from?

Answer 32

They come from the earths crust. Metal ore is mined and washed to remove other minerals and unwanted materials.