WEEK 9 - Bronze and Iron Flashcards
What’s the invention of bronze?
- As copper ores like malachite became scarce, copper needed to be extracted from sulphide minerals.
- Chalcopyrite (copper sulphide) often occurs with metals like arsenic in minerals such as arsenopyrite.
- Copper mixed with arsenic formed the first metal alloy: bronze.
Examples:
- Chalcopyrite (CuFeS2)
- Arsenopyrite (FeAsS)
What change led to the development of better bronze?
- Arsenic was originally added to copper to control its properties, but it was later replaced by tin.
- The shift to tin may have been due to high death rates among early bronze workers (due to arsenic exposure).
Why was tin preferred over arsenic?
Tin lowers the melting point of copper, making it easier to smelt.
Why was bronze so useful?
Bronze is attractive, easy to work, and ideal for creating ornamental objects.
What is the main advantage of bronze over pure copper?
- Bronze is harder than pure copper, making it much more useful for tools.
- Bronze containing 90% copper and 10% tin is twice as hard as pure copper!
How was iron discovered and processed during the Iron Age?
- The discovery of iron for tool-making likely happened by accident.
- In a basic furnace, iron doesn’t melt into liquid but forms a soft, spongy mass called a bloom because iron melts at a higher temperature than copper.
What was the process for purifying iron during the Iron Age?
- Iron blooms had impurities trapped inside (called slag).
- To purify the iron, the bloom was heated and hammered on an anvil.
- The pounding removed the slag, and the process was repeated to further purify the metal.
When did humans first develop iron smelting and forging?
- The earliest methods of smelting and forging iron are believed to have developed around 1,500 BC.
- These methods became widespread by about 1,200 BC.
Example: Iron mask from Africa and iron spear tips.
What is pure iron’s undesirable qualities?
- It is softer than bronze
- It is too soft to hold a sharp edge
- Iron tends to oxidize (rust)
How was the quality of iron improved via technology?
- Steeling
- Tempering
What is steeling?
Steeling is the process of adding carbon to iron to make it harder.
What is steel?
Steel is an iron-carbon alloy that contains less than 1.7% carbon.
How was carbon added to iron?
Carbon likely came from carbon monoxide in the furnace or from the carbon in the fuel used to heat the iron.
What is tempering?
A method used to change the properties of metal, especially steel.
How does tempering work?
It involves two steps:
- Quenching – cooling the hot metal quickly in water to make it harder
- Reheating – gently reheating the metal to reduce brittleness
Why is tempering useful?
It creates strong metal that is also slightly flexible (not too brittle).
Famous example of tempering
Japanese steel swords are known for their excellent tempering
What is casting?
The process of melting metal and pouring it into moulds to shape it.
How was casting used in ancient China?
- Chinese artisans built powerful furnaces that could melt iron.
- The molten iron was poured into moulds to form tools or objects.
What happened after casting?
The cast iron was reheated to remove extra carbon, which made the final product more flexible and easier to work with.
Why was steel important in the Industrial Revolution?
Steel became essential because it is strong, versatile, and could be made in large amounts.
How did steelmaking change?
New methods were developed to create different types of steel with specific properties for different uses.
Why is steel still important today?
Steel is used in buildings, tools, transportation, and many everyday products—making it one of the most important modern metals.
