7 ferrous alloys

ferrous alloys

cast iron, wrought iron. inferior for today. superior to many others due to high ductility and strength. Pig iron divided in 1. steel 2. other ferrous alloys

advantages of using steel in structures

1. highly recyclable material

2. compatible with other building materials

3. enables light construction

4. improves earthquake resistance

5. rapid construction

6. durable and sustainable

non-ferrous alloys

aluminium aloys, copper alloys

Steel

contains carbon b/w 0.1-2%. More carbon→ harder. made from pig iron

iron ores

ferrous alloys cant be found in nature, have to be made from the ores→ rocks and minerals from which metallic materials are extracted. Found in the forms of oxides sulfides, carbonates

E-modulus of steel

210 GPa

Ferrous alloy production

1. collecting necessary raw materials (iron ore, coke(essentialy carbon), limestone(used to purify iron))

2. ground down in size + blended

3. blend fed to blast furnace (melting ores and extracting iron-rich alloy)

pig iron

iron with about 4wt% carbon, highly brittle and unsuitable for use. Needs to be further processed.

Blast furnace slag

waste material for pig iron production, lime(CaO) reactis with silica rich impurities of iron ore and produces slag.

Cast iron

further refinement based on pig iron, no longer preferred

grey cast iron

composed of ferrite crystals and graphite flakes, poor impact resistance and low strength

white cast iron

highly brittle and hard phases

wrougth iron

not used often anymore, contains below 0.1% carbon. contains up to 5% slag fibers. Good weldability, high ductility, good corrosion resistance and high tensile strength

room temp steel

2 phases ferrite(a)(almost pure iron, BCC crystal structure, low strength, hg=igh ductility) and iron carbide (Fe3C) (hard and brittle)

eutectoid point

eutectic like, not from liquid to solid but solid to solid.

hypereutectoid steel

Fe-C alloys with over 0.8% carbon

HYpoeutectoid steel

lowe carbon content than 0.8%

pearlite

a+Fe3C

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