Properties of iron and steel

-Iron produced in a blast furnace is called pig iron, and isn't very useful

-It's about 96% iron and contains impurities,mainly of carbon, this makes it very brittle 

-However, we can treat the iron from the blast furnace to remove some of the carbon 

-If we remove all the carbon and impurities from pig iron, we get pure iron which is very soft and easily shaped, but too soft for most uses 

-To make iron more useful its need to be combined with tiny amounts of other elements including carbon and certain metals 

- An alloy is a metal that contains other elements 

-Iron that has been alloyed with other elements is called steel. By adding elements in carefully controlled amounts, we can change the properties of steel 

-Pure iron is soft and so easily shaped because the layers can slide over each other 

-There are lots of different types of steel which are all alloys of iron carbon and/or other elements 

-The simplest steels are carbon steels. These are made by alloying iron with small amounts of carbon, these are the cheapest steals to make 

-They are used for things such as; bodies of cars, knives, machinery, ships, containers and structural steel for building 

-Often these carbon steels have small amounts of other elements in the, as well

-High carbon steel is very strong but brittle 

-Low carbon steel is soft and easily shaped, its not as strong but less likely to shatter 

-Mild steel is one type of low carbon steel, which contains less that 0.1% carbon. It's very easily pressed into shape which makes it useful in mass production like making car bodies  

-Low-alloy steels are more expensive than carbon steels because they contain between 1%-5% of other metals such as nickel, titanium,chromium, tungsten and manganese

-Each of these metals give steel that is well suited for a particular job, e.g. nickel steel alloys are used to build long-span bridges, bicylce chains and military armour-plating, becuase they are very resistant to stretching forces 

-Tungsten steel operates well under very hot conditions so it is used to make high-speed tools 

-High- alloy steels are even more expensive because they contain a much higher percentage of other metals 

-E.g. chromium steels have between 12% and 15% chromium mixed with iron, and often nickel  is mixed with it too, this provides strenght and chemical stability 

-These chromium nickel steels are more commonly known as stainless steels, we use them to make cooking utnesils and cutlery, they are also used to make chemical reaction vessels becuase they combine hardness and strenght with great resistance to corrosion