Cast Iron

Cast iron is an alloy of iron and carbon with the content of carbon being more than 2%. In addition, it contains impurities such as manganese, phosphorous, silicon and sulphur. The presence of manganese makes it brittle when it is more than 0.75%. The fluidity of cast iron is increased by the presence of phosphorous. Silicon decreases shrinkage and ensures softer and better casting when it is less than 2.5%.

1. Manufacture of Cast Iron

Cast iron is manufactured by re-melting pig iron with coke and limestone. This process of re-melting is done in a furnace called the cupola furnace. Except for the size, it is almost the same as that of blast furnace. To some extent, the impurities in the pig iron are removed by this process and comparatively pure iron is obtained in the molten stage from the bottom of the furnace. The slag is removed at regular intervals from the top of the cast iron. The molten cast iron is led into the moulds called cast-iron castings.

2. Properties of Cast Iron

As an engineering material, cast iron has the following properties:

1. It has high compressive strength.
2. It has high machinable qualities based on the composition.
3. It has a fairly low melting point.
4. It has high fluidity which helps in making good casting impressions.
5. It has fairly good corrosion resistance.
6. It lacks plasticity and is not suitable for forging.
7. It is hard and brittle but not ductile.
8. It can not be magnetised.