Ironmaking and Steelmaking

Question 1

Where did the invention of ferrous metallurgy occur?

Answer 1

Protoliterate Vinca Culture based in the lower Danube where it empties into the Black Sea

Question 2

What is the first step of iron making?

Answer 2

Minerals from iron ore need to be removed by washing and/ or roasting, this changes the composition making it more easily processed

Question 3

Name 4 iron ores found in Britain

Answer 3

Carbonate ores
Haematite ores
Liminite ores
Bog iron ore

Question 4

Describe Carbonate ores

Answer 4

FeCO3 (iron carbonate), roaring this ore drives off CO2 = FeO

Further roasting + Fe2O3, haematite

Question 5

Describe Haematite ores

Answer 5

Fe2)3, valued to its purity, contained little P, compared to iron ores from the continent

Question 6

Describe Liminite ores

Answer 6

Also known as hydrated iron oxide ores, with absorbed water (fe2O3.H2O)

Probably dug out of outcrops i.e. open cast mining.

Question 7

Describe bog iron ore

Answer 7

Found mainly in the highland zone.

Consist of a deposit of iron ore occurring in sub-Artic conditions, caused by precipitation where iron-bearing surface water meets organic material. Deposition is continuous, at the rate of.a few mm/ year

Question 8

Why was iron smelting realised relatively late?

Answer 8

(Not due to high mp 1538oC) but means required for its reduction, which takes place at ~800oC

Question 9

Name some common impurities in iron

Answer 9

oxides of other elements

a common one is silica SiO2

Question 10

What is slag

Answer 10

Fragments of iron ore form a charge for reduction and melting, but also contain large amounts of SiO2, which in combination with iron oxide (Fe2O3) form a slag (fayalite)

Slag is detrimental to properties

Question 11

How is slag removed

Answer 11

Removed by liquidation, requires high T 1150oC, above T @ which FeO reduced but below mp pure Fe

Question 12

What is bloom

Answer 12

A single sponge-like solid state, produced after removal of slag

Consists of iron interspersed with L slag

Some of L slag drains away in the furnace, remainder “squeezed-out” by subsequent re-heating and hammering

Question 13

How is the temperature obtained that is needed to make the slag molten

Answer 13

Need fuel to burn, insulation to maintain the T achieved by burning the fuel

Question 14

What was initially used in the second stage of ironmaking?

Answer 14

Simple bowl furnace, consisting of a layer of insulating brick, through which a tuyere would be introduced

Question 15

What does the iron smelting process use

Answer 15

Carbon monoxide, generated through partial combustion of charcoal in air pumped through tyre, using bellows to reduce iron oxide to iron

Increase the T in furnace and allows some of L slag to run out of the bottom of the furnace

Question 16

What is the equation to reduce iron oxide

Answer 16

Fe2O3 + 3CO –> 2Fe+3CO2

Question 17

What is cinder

Answer 17

The liquid slag that runs out of the bottom of the furnace

Question 18

What happens if the temperature in a bowl furnace becomes too high

Answer 18

Heating conditions can become more oxidising

If rate of oxidisation of iron is increased, this reduces the amount of iron finally obtained

Question 19

What was obtained 5 hours after heating an iron ore?

Answer 19

Bloom obtained, consisting of mostly iron but still containing some slag

Question 20

What happens in the third stage of iron making

Answer 20

bloom is reheated and hammered

Reheated to around 1150oC to make slag fluid

Hammering forces L slag to flow between the iron grains in the bloom, to be extruded out of the bloom

Improves properties –> piece of wrought iron

Question 21

What is the microstructure like after the third stage of iron making

Answer 21

Simple

Relatively pure

Reduced FeO so largely C free

Question 22

Why is further pick up of C in wrought iron rare?

Answer 22

Because it is processed in solid state

Question 23

What is the microstructure of wrought iron

Answer 23

grains of ferrite (ductile) interspersed with stringers of slag

Question 24

What is fluxing

Answer 24

The addition of compounds to lower the mp of the slag, so processing can take place at lower temperatures

Question 25

What is a shaft furnace

Answer 25

It’s like a bowl furnace, but has a tall chimney above 5-10 ft high

Allows air to be drawn in, rather than pumped in by bellows = more efficient process

Question 26

When were shaft furnaces used and when is there little evidence

Answer 26

common practice in roman times

To retrieve the bloom the furnace would be dismantled

Question 27

In the Iron Age what was the size of the blooms produced

Answer 27

10kg in weight

uses bowl furnaces of ~ 0.5m in size

Question 28

What was characteristic of the blooms produced

Answer 28

They had high P pick up

from a P-bearing mineral difficult to remove from the iron ore

Question 29

Where was coinage used

Answer 29

Coinage that came into use in the Lowland Zone of Britain in ~50BC

(Probably as a result of the Gallic wars of Julius Caesar)

Consisted of gold staters and silver and bronze units

Question 30

What was found in the Highland Zone

Answer 30

Long straight bars of iron found

(e.g. on the malvern Hills, and at Bourton-on-the-Water in the Cotswolds)

interpreted as means of currency

Question 31

What did the bending of one end of the currency bar indicate

Answer 31

Interpreted as showing the quality of the bar - if bent = ductile = high quality

currency bars seen as currency as could be converted into swords

Question 32

How long and heavy were Iron Age swords

Answer 32

3 ft long, ~600g

same shape and size as currency bars

typically up to ~0.5% C

Question 33

How were Iron Age swords made

Answer 33

edges of the sword were either hammered to make OR work harden –> retain a ground edge on the weapon

OR

by hammering together leaves of thinner iron plates

LATER

Blades had edges hardened by carburising

Question 34

What is Carburising

Answer 34

edge of blade being placed in a C-rich atmosphere (e.g. packed with charcoal)

Causes C atoms to diffuse into the structure

Increases the C content locally = grater pearlite content = tougher and able to receive a ground edge

Question 35

Compare iron and bronze swords

Answer 35

Iron Age: relatively ductile, might bend in combat - could be straightened then used again

Bronze sword: more brittle, would fracture in combat - could not be used agian

Question 36

When was the Delhi Iron pillar erected?

Answer 36

~400 AD

Question 37

How was the Delhi iron pillar said to be made

Answer 37

By bloomers process described above, blooms being beaten into discs, piled on top of each other until they fused

Question 38

Why is the Delhi iron pillar remarkable

Answer 38

for its lack of corrosion - attributed to high purity of the alloy

Contains a certain amount of P, which has led to the suggestion that the corrosion resistance is due to the formation of a P-containing passive layer