B. Metals Flashcards
What is a ferrous metal?
- All contain iron ferrite
- Most are magnetic
- Have a high tensile strength and durability
- Vulnerable to rust if exposed to moisture without a protective finish
What are the types of ferrous metal?
- Cast iron
- Low carbon / mild steel
- High carbon steel
What are the properties of cast iron?
Ferrous
Hard but brittle, resists deformation and rust
What are the uses of cast iron?
Uses: Kitchen pans, machine bases, manhole covers
What are the properties of low carbon / mild steel?
Ferrous
Tough, ductile, rusts easily if not protected
What are the uses of low carbon / mild steel?
Uses: Car bodies, steel building frames, pipelines
What are the properties of high carbon steel?
Ferrous
Hard, brittle, Hard wearing, resists abrasion, retains its shape
What are the uses of high carbon steel?
Uses: Tools, blades, scissors
Why is metal an expensive material to obtain?
- Mining is dangerous and often remote
- Mining machinery is expensive to buy, operate and maintain
- Significant electrical/heat energy needed to separate metal from iron ore
What is a non-ferrous metal?
- Pure metal that does not contain iron
- Non-magnetic (so used for electronics)
- Higher resistance to rust, but will still corrode or oxidise
Why is stainless steel protected from rust?
It is protected due to the presence of chromium
What are the properties of aluminium?
Non-ferrous
Lightweight, ductile, resists corrosion
What are the uses of aluminium?
Uses: Bike frames, drinks cans, takeaway trays
What are the properties of zinc?
Non-ferrous
Brittle but malleable, highly resistant to corrosion
What are the uses of zinc?
Galvanising steel
What are the properties of copper?
Non-ferrous
Ductile and malleable, good electrical conductor
What are the uses of copper?
Plumbing supplies, electrical cables
What are the properties of tin?
Non-ferrous
Malleable and ductile, high corrosion resistant, good electrical conductor
What are the uses of tin?
Solder, plating surfaces e.g. cans
What makes metal an expensive material to obtain?
Mining is dangerous and often very remote
Mining machinery is very expensive to buy and operate
Techniques for extraction uses dynamite
Significant electrical or heat energy is required to separate metal from its ore
What is an alloy?
Alloys are a mixture of at least one pure metal and another element
Why are alloys harder than pure metals?
Because they contain atoms of different sizes, distorting the arrangement of the atoms making it hard for the layers to slide over each other
What is the composition of high speed steel?
Chromium Molybdenum
Tungsten Vanadium
Cobalt Carbon
What are the properties of high speed steel?
Can withstand high temperatures when machining at high speed
What are the uses of high speed steel?
Cutting tools such as the drill bits, mill cutters, taps and dies
What is the composition of stainless steel?
Low carbon 0.03-0.08%
Chromium 10.5-26%
Iron
What are the properties of stainless steel?
Hard
Ductile
Rust resistant
Why is stainless steel rust resistant?
Chromium layer protects steel from corrosion
What are the uses of stainless steel?
Cutlery, kitchen and medical equipment
What is the composition of brass?
Copper 65%
Zinc 35%
What are the properties of brass?
Malleable, easily cast, corrosion resistant
What are the uses of brass?
Musical instruments, plumbing filaments and ornate artefacts
What are the advantages of alloys over pure metals?
Harder than pure metals because they are made from different sized molecules that make it harder for them to slide over each other.
What is aluminium extracted from?
Bauxite
What is liquation?
Metals with low melting points (e.g. tin and lead) is separated from an ore or alloy using liquation.
The impure metal is melted in a sloped container, and runs off, leaving behind the impurities
What properties do hand tools need to have?
Hard, tough, resistant to tension and compression, ergonomic and comfortable for use
What metal is used to make hand tools?
High carbon steel
What properties do cooking utensils need to have?
Tough, durable, corrosion resistant, food safe, flame and heat resistant
What metal is usually used to make cooking utensils? Why?
Stainless steel
It’s strong, rust resistant and hygenic
What is annealing?
The process of heating and slowly cooling metal to alter its properties, reducing its hardness and increasing ductility
Why is annealing useful?
Hard, brittle metals fracture when bent or pressed. In comparison, annealing will improve the malleability and reduces the risk of fracture
What is hardening?
Steel is heated at high temperatures until some of the carbon content dissolves. The metal is then rapidly cooled.
What does hardening do for the properties of metal?
Increases strength and wear resistance, but increases brittleness
What are the three steps in welding?
High heat melts the base materials
A metal filler is melted to fill the joint
As they cool the parts fuse together, creating a very strong joint
