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Flashcards in Metals Deck (68)
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1

Metals can be classified into two main groups. What are they?

  • Ferrous metals
  • Non-ferrous metals

2

What are ferrous metals?

A ferrous metal contains iron (ferrite) and carbon.

3

What is a non-ferrous metal?

A non-ferrous metal does not contain iron.

4

What is a ferrous alloy?

Ferrous alloys are a mixture of two or metals - at least one of which contains iron and carbon.

5

What is a non-ferrous alloy?

A non-ferrous alloy is a mixture of two or more metals - none of which contain iron.

6

Name four ferrous metals.

  • Cast Iron
  • Mild Steel
  • Medium Carbon Steel
  • High carbon steel

7

Name at least five non-ferrous metals.

  • Aluminium
  • Copper
  • Lead
  • Tin
  • Zinc
  • Titanium
  • Platinum
  • Gold
  • Silver

8

Name three ferrous alloys.

  • Stainless steel
  • High speed steel
  • Die (tool) steel

9

Name three non-ferrous alloys.

  • Brass
  • Bronze
  • Duralumin

10

Gold is the only metal found in a useable form. All other metals are extracted from ores. Which ores contain the following metals - iron, copper, aluminium, lead, tin, zinc?

  • Iron is found in magnetite and haematite
  • Copper is found in chalcopyrite
  • Aluminium is found in bauxite
  • Lead is found in galena
  • Tin is found in cassiterite
  • Zinc is found in zinc blende

11

What is added to iron to strengthen it? What is this material called?

  • Iron is combined with carbon to produce steel.
  • The amount of carbon determines the strength and hardness of the steel.

12

What are the two most common metal ores?

  • Aluminium is the earth's most common ore (bauxite).
  • Iron is the second most abundant metal ore.

To find out more click here and here

13

The structure of all metals are made from what?

Crystals

Each crystal has a boundary that is firmly bonded to the boundary of a neighbouring crystal.

14

How is iron converted from either haematite or magnetite ore?

  • The ore is heated in a blast furnace.
  • The impurities (slag) are removed from the surface.
  • The material produced is called "pig iron".
  • Pig iron is then converted into steel by adding carbon in a basic oxygen furnace.

To find out more click here and here and here

15

What effects are produced by increasing the carbon content in irons and steels?

(see the "Properties of materials" deck for key word definitions)

  • The material becomes harder
  • Toughness is reduced  and the material becomes more brittle. Cast Iron can be brittle under impact.
  • Medium and High Carbon steels can be heat treated to make them stronger and harder. The material can then be used for cutting tools (mild steel has insufficient carbon to be heat treated).

16

What is the carbon content % of Mild Steel?

Less than 0.3%

17

What is the carbon content % of Medium Carbon Steel?

0.3 to 0.6%

18

What is the carbon content % of High Carbon Steel?

0.6 to 1.7%

19

What is the carbon content % of cast iron?

3.5%

20

Name at least three uses for mild steel.

  • Nuts
  • Bolts
  • Washers
  • Car body panels
  • Panels for fridge freezers and other white goods

21

Name two uses for medium carbon steel.

  • Springs
  • General gardening tools

22

Name at least three uses for high carbon steel.

  • Hand tools
  • Scribers
  • Dot Punches
  • Chisels
  • Plane blades

23

Name at least three uses for cast iron.

  • Castings
  • Manhole covers
  • Engine blocks
  • Machine parts
  • Brake Discs
  • Vice jaws

24

Although aluminium ore (bauxite) is the most abundant ore in the Earth's crust, it is not the most processed metal - steel is. Why?

Aluminium is difficult to process, required large amounts of energy. It is therefore more expensive to produce.

25

Name three common uses for aluminium.

  • Saucepans
  • Overhead power cabels
  • Engine blocks
  • Brake calipers
  • Car Body panels
  • Aircraft parts

26

Name three common uses for copper.

  • Electric contacts
  • domestic water pipe work
  • electrical cable
  • jewellery

27

Name three common uses for gold.

  • Jewellery
  • Electronic components
  • Switch and cable contacts
  • SIM cards

28

Name a common use for lead.

  • Flashing on roofs - where the tiles meet the brickwork

29

Name two common uses for platinum.

  • Expensive jewellery
  • Thermocouple cables

30

Name two common uses for silver.

  • Expensive cutlery
  • Jewellery
  • Solder
  • Ornaments

31

Name two common uses for tin.

  • Coating for steel food cans
  • food wrapping (foil)

32

Name two common uses for titanium.

  • Hip replacements
  • spectacle frames
  • aerospace parts due to it's high strength to weight ratio

33

Name at least three common uses for zinc.

  • A coating for steel (galvanising and zinc plating)
  • buckets
  • electrical unit casings
  • lock mechanisms
  • high detail die castings

34

List at least four benefits of alloying metals.

  • changes the melting point
  • changes the colour
  • increases strength, hardness and ductility
  • enhances resistance to corrosion and oxidation
  • changes electrical/thermal properties
  • improves flow properties, producing better castings

For more information click here

35

What is oxidation?

Oxidation is an oxide layer that forms on a metal surface when in contact with oxygen. In most metals this protects the surface from further oxidation but in steels, it is porous and results in further oxidation and corrosion.

36

What metals are alloyed to produce duralumin and what is it commonly used for?

  • Duralumin is an alloy of aluminium and 4% copper, 1% manganese and 0.1% magnesium.
  • It is used for structural components on aircraft.

37

What metals are alloyed to produce brass and what is it commonly used for?

  • Brass is an alloy of copper and 35% zinc.
  • It is used for cast valves, taps, boat fittings and ornaments.

38

What metals are alloyed to produce bronze and what is it commonly used for?

  • Bronze is an alloy of copper and 10% tin.
  • It is used for statues, coins and bearings.

39

What metals are alloyed to produce nitinol and what is it commonly used for?

  • Nitinol is made from nickel and titanium
  • It is a smart metal alloy used in springs and muscle wires

For more info click here and here

40

Which metals can be alloyed with steel to produce High Speed Steels (HSS)?

  • Tungsten
  • Chromium
  • Vanadium
  • Cobalt

41

What are the properties of high speed steels and what are they used for?

  • HSSs are very hard and will cut at very high temperatures
  • Therefore they are used for cutting tools such as drills

42

What are the properties of high tensile steels and what are they used for?

  • High tensile steels have a good tensile strength and toughness and are generally corrosion resistant.
  • They are used for car engine components.

43

Which metal is alloyed with steel to produce high tensile steel?

  • Nickel

44

Which three metals are alloyed with steel to produce stainless steel?

  • Chromium
  • Nickel
  • Magnesium

45

What are the properties and uses of stainless steel?

  • Stainless steel is tough, durable and corrosion resistant
  • It is used for sinks, cutlery and sanitary ware.

46

Which two metals are alloyed with steel to produce tool and die steel?

  • Chromium
  • Manganese

47

What are the properties of tool and die steels and what are they used for?

  • Tool and die steels are very hard and tough with excellent wear resistance.
  • They are used for fine press tools, extruder dies, blanking punches and dies, some hand tools.

48

Explain the term work hardening.

Work hardening occurs when metals are "cold worked" such as bending, rolling or hammering. The crystal structure of the metal is distorted causing internal stresses that make the metal harder.

49

How do you return work hardened metal to a "soft" state?

The metal must be annealed.

For information on annealing click here

50

What is planishing?

Planishing is the term given to a beaten decorative finish in a metal such as copper or silver. The hammering work hardens the material.

51

List at least four heat treatment processes.

  • Annealing
  • Hardening
  • Tempering
  • Normalising
  • Quenching
  • Case Hardening
  • Carburising
  • Nitriding
  • Flame hardening
  • Induction hardening

52

What is the definition of heat treatment?

Heat treatments are processes to heat and cool metals in a controlled way to achieve a beneficial change in the properties of the materials.

53

What is annealing?

Annealing is a metal heat treatment process that reverses the internal stresses caused by work hardening. By heating the metal, the crystals grow making the material softer and more ductile. The temperature must be maintained for a sufficient period of time to allow the material to "soak". The material is then cooled slowly allowing the crystals to keep their new shape.

Glass can also be annealed.

For more information click here

54

When working with steel, what is hardening and how is it achieved?

Hardening is a heat treatment that changes the way the carbon within the steel affects the strength and hardness of the material. The carbon in the structure moves out of its normal position and when the material is quenched, the carbon does not have time to return to its original place. This causes the material to be strengthened and hardened.

For more information click here

55

What is tempering and why is it an important process to carry out after hardening medium and high carbon steels?

Tempering is carried out after hardening to remove any brittleness in the hardened steel. First the hardened steel is cleaned to a shiny grey colour and then heat is applied to the correct tempering colour. The material is then rapidly cooled (quenched). Without tempering the steel could well fail by cracking or shattering.

For more information click here

 

56

How can you tell the what the tempering temperature is and what happens to the steel as the temperature rises?

The tempering temperature is determined by the colour of the steel. At 230ºC the steel is a pale straw colour. At 300ºC it is blue. This is known as the tempering colour. As the temperature rises the steel's hardness is reduced but the toughness is increased.

Click here to view a tempering colour chart.

57

What is quenching?

Quenching is the rapid cooling of heat treated metals. Sometimes the quenching media (brine, water, oil or air) is agitated to prevent rapid localised cooling that might result in cracks.

58

What is normalising and how is it achieved?

Normalising is a heat treatment process where the crystal structure is allowed to become a uniform size. The metal is heated to a specific temperature where the crystal structure begins to change. The temperature is maintained (soaked) until all the crystals have been normalised. After cooling in air, the metal is tougher and more ductile.

59

What type of steels can be case hardened?

Low carbon steels such as mild steel are suitable for case hardening.

60

What is case hardening and what types of product benefit from the process?

  • Case hardening is the hardening of the surface/outer skin of a low carbon steel.
  • Cams and gears benefit from case hardening as it is only the surface that needs to be hard, leaving the remainder of the component in a less brittle state.

For more information click here

61

List four different ways of case hardening mild steel.

  • Carburising
  • Nitriding
  • Flame hardening
  • Induction hardening

62

Explain the case hardening process of carburising.

In carburising the steel is placed in a ceramic box packed with carbon rich material and then heated to produce a carbon layer. Then the steel is heated to around 760ºC and then quenched to produce a hard case.

63

List two advantages of case hardening mild steel.

  • Steels that have too little carbon for heat treatment can be given a hardened surface.
  • The process leaves a tough inner core, making it suitable for camshafts, gears, steering components, all of which take a lot of wear.

64

Name one disadvantage of case hardening.

In most cases grain-growth occurs which increases the size of the steel. A machining process is then required to return the steel to its required size.

65

Nitriding is another case hardening process. Explain how its done.

In nitriding, steel is immersed in nitrogen whilst being heated to 500ºC. No additional hardening is necessary.

66

List at least three advantages of nitriding.

  • No additional hardening is necessary.
  • It removes the chance of surface cracks.
  • It increases resistance to corrosion.
  • It is a clean process.
  • It is economical for large numbers.

67

Name two disadvantages of nitriding.

  • Initial set up costs are high.
  • If overheated there is a permanent loss of hardness.

68

Name two advantages of case hardening by flame hardening or induction hardening.

  • A localised area of the product can be hardened leaving other area unaffected where toughness is required.
  • Grain growth does not occur so no additional machining is required.