9.4 - Property Suitability Flashcards
What are the types of carbon steel?
High carbon
Medium carbon
Low carbon (mild steel)
What’s the carbon % in steel?
<1.8%
What’s the carbon % in grey cast irons?
3.2-3.5%
What are low carbon steels?
Cheapest and most widely used group of steels, they’re the weakest by still stronger than most non-ferrous metals and alloys, can be easily hot / cold worked
Uses of low carbon steels?
Pressing out panels for car bodies and general sheet-metal applications
What are medium carbon steels?
Harder, tougher, more expensive and stronger than low carbon steels, but less ductile and can’t be bent when cold without risk of cracking (greater force needed too)
Low carbon steel carbon %?
<0.3%
Medium carbon steel carbon %?
0.3-0.6%
How to toughen low carbon steels?
Heating and quenching with water, they cannot be hardened
Uses of medium carbon steels?
Crank shafts, forgings, axles (mechanically stressed components)
What is high carbon steel?
Hardest, strongest, and most expensive steel, but less tough than medium carbon steel, available as hot rolled bars or forgings
High carbon steel carbon %?
> 0.6%
High carbon steel uses?
Cold drawn wire (piano wire)
Used to make chisels, cutting tools and drill bits
What’s the effect of carbon on iron?
0% carbon - v high duct, low hard, lower strength
- 9% - v high strength, high hard, v low
- 4% - slightly lower strength, slightly higher hard, low duct
Properties of copper?
High strength
Very ductile (cold worked, annealed stretch twice length)
Corrosion resistant
Good conductor
Uses of copper?
Electrical conductors and switchgear components (second only in conductivity to silver)
Copper powders used for sintered components
Non ferrous metals and metal alloys?
Copper Brass (alloy) Tin bronze (alloy) Aluminium Zinc
Properties of brass?
Alloy of copper and zinc
Properties based on amount of zinc, dezincification occurs in sea water, so tin is added
Brass castings are coarse grained and porous
How to machine brass?
Depends on hot rolling from cast ingots, then cold rolling to give mechanical strength
Properties of tin bronze?
Alloy of copper and tin
They have deoxidising agent to prevent tin from oxidising during casting and hot working (becomes scratchy), agents include zinc in gun metal alloys
Properties of Aluminium?
1/3 as dense as steel
Much weaker, strength/weight ratio weaker
Good conductor
Corrosion resistant, but not marine environments
Uses of aluminium?
Stressed components, eg on aircrafts (alloys)
Commercial aluminium?
Contains 1% silicon to improve stiffness and strength, loses qualities as a result
Use of tin bronze?
Castings
