A level metals

Question 1

Alloying definition

Answer 1

A parent metal combined with another substance (metal or carbon) resulting in superior properties including strength, hardness, durability etc.

Question 2

Common alloying metals for steel

Answer 2

Chromium- increased corrosion resistance, hardness and toughness

Vanadium- increases strength and toughness including wear resistance

Nickel- increased strength and hardness and corrosion resistance

Question 3

Smart alloys

Answer 3

Alloys that react to changes in the external environment eg. Nitinol which reforms to a set shape when heated ( made of nickel and titanium)

Question 4

Tungsten carbide

Answer 4

Tungsten and carbon a made into a powder then sintered (heated and pressurised extremely to produce a solid)
Cutting tools, jewellery, machinery

Pros - 2x as hard as steel and 2x density

Cons - expensive to work with, need diamond to process

Question 5

high speed steel

Answer 5

18% tungsten, chromium and vanadium are mixed with carbon steel
- higher melting point means it is used for machining bits and it is also very hard

Question 6

heat treatment

Answer 6

involves the use of heating and chilling to extreme temperatures to make a metal harder or softer

Question 7

hardening and tempering

Answer 7

• heat gradually with a torch until it is red hot
• plunge into cold water or oil

to temper:
- use emery cloth to clean the surface
- heat again to red hot
- leave to cool in air until it reaches the desired colour
- quench in water again to make it less brittle

Question 8

steel tempering colours

Answer 8

pale yellow - lathe tools - 230
dark yellow - drill bits - 250
brown - shears - 260
purple - knives - 270
dark purple - saws - 280
blue - screwdrivers - 300

Question 9

case hardening

Answer 9

works by creating a thin layer of high carbon steel that is much harder
- placed in a high carbon environment like being covered in carbon and then heated till red hot and repeat to increase the cases thickness
- allow to slowly cool

creates a hard edge but maintains a soft core

Question 10

annealing

Answer 10

softens the metal

• for steel use a torch to heat until red hot (900 degrees)
• allow to slowly cool
• for aluminium hold the torch at a distance and use soap to show when it is hot enough
• allow to slowly cool

Question 11

normalising

Answer 11

returning to its original state

• heat the steel until cherry red
• allow to cool in air

Question 12

mig welding

Answer 12

(metal inert gas)
- heat generated through an electric current
- workpiece clamped into negative electrode
- steel electrode used as filler material

Question 13

tig welding

Answer 13

(tungsten inert gas)
- heat generated by an electric arc (electrode doesn’t touch the work)
- tungsten electrode isn’t used up
- filler material added separately

Question 14

spot welding

Answer 14

• welds sheets together without filler material
• contacting sheets are joined by heat from an electric current
• workpieces held by electrodes

Question 15

oxypropane/acetalyne welding

Answer 15

uses a gas torch to melt the metal together
- oxygen and other gas ratio are altered to change the temperature of the flame

Question 16

soft soldering

Answer 16

for below 320 degrees
- tin or lead solder is added and heated by a soldering iron
- melted between two components to join them

Question 17

hard soldering

Answer 17

590-870 degrees
- used for higher MP metals
- uses a torch to melt the solder
- used in jewellery making

Question 18

brazing

Answer 18

more than 850 degrees
- heated with a torch to melt brazing rods
- used to join copper or brass

Question 19

hot/cold riveting

Answer 19

when both sides are accessible the rivet is crushed to dome the end to stop it pulling through but extreme fore is required for large rivets so instead hot riveting is used where the steel is heated to near melting and then it is easily hammered into a dome

Question 20

pop riveting

Answer 20

when both sides aren’t accessible use pop rivets

• the end of the rivet as its pulled through crushes the walls on the hard to reach side this causes it to crumple creating a ridge that stops it pulling back through

Question 21

self tapping screws

Answer 21

cut their own tread whilst being screwed in so mainly is used in metal work but if precise application is needed then it is best to drill a pilot hole

Question 22

machine screws

Answer 22

type of bolt that has a fine thread and have a screw head rather than the regular hexagonal bolt head and are used in many product casings where the holes are already screwed and tapped so they mainly have a blunt end

Question 23

bolt

Answer 23

goes through many parts and then has a nut screwed on and tightened to hold the parts together

Question 24

metal finishes

Answer 24

galvanising - coating in a thin layer of zinc
zinc anodes - blocks of zinc attached at regular intervals to the surface
painting - can include plastic and acrylic or even cellulose paint
oil or grease - for moving parts
electroplating - coating cheaper metals with more desired metals