The Difference between Pig Iron and Wrought Iron

Pig iron usually refers to the iron alloy with carbon content of the 2 to 4.3%, also known as cast iron. Besides carbon, pig iron also contains silicon, manganese and small amounts of sulfur and phosphorus, it can not be forged, but can be cast. According to the presence of carbon under the different forms, pig iron can be divided into steel-making pig iron, foundry pig iron and ductile iron.

The carbon in the steel-making pig iron is existed by the carbide form, and has the cross section of white, usually known as white iron. The performance of steel-making pig iron is hard and brittle, so it is generally used as raw materials of cast steel.

The form of carbon in the foundry pig iron is graphite flake, and its fracture is gray, usually known as gray iron. Because graphite is soft, with lubrication, which has good cutting, wearing and casting performance. But the strength of its anti-bit is not enough, so it can not be forged. Gray iron is only used for the manufacturing of castings, such as casting a variety of machine tool bed bases, iron pipes and so on.

The carbon in ductile iron is existed as spherical graphite, the mechanical properties are far better than gray iron and close to cast steel, it has excellent casting, machining and wear resistance, and has a certain flexibility. So, ductile iron has been widely used in manufacturing crankshaft, gears, pistons and other senior castings, and a variety of mechanical parts.

Besides above, there are some iron alloys, which have high amount of silicon, manganese, nickel or other elements, such as ferrosilicon, ferromanganese, etc.. These iron alloys are often used for the raw materials of cast steel. With these alloys, cast steel can get better physical performance.

The cast iron with carbon content of less than 0.2% is called wrought iron or pure iron. The cast iron with carbon content of 0.2-1.7% is called cast steel. So, cast steel is a kind of special cast iron. More than 2% of content is called pig iron. Wrought iron is very soft, plastic and easily deformed, but its strength and hardness are lower, so not widely used.

Home | More Articles