Wrought iron is almost pure iron.
It is made from pig iron in a puddling furnace and has a carbon content of less than 0.08 percent. Carbon and other elements present in pig iron are taken out, leaving almost pure iron. In the process of manufacture, some slag is mixed with iron to form a fibrous structure in which long stringers of slag, running lengthwise, are mixed with long threads of iron. Because of the presence of slag, wrought iron resists corrosion and oxidation, which cause rusting.
Wrought Iron Uses. Wrought iron is used for gates, porch railings, fencing, farm implements, nails, barbed wire, chains, modern household furniture, and decorations.
Wrought Iron Capabilities. Wrought iron can be gas and arc welded, machined,plated, and is easily formed.
Limitations. Wrought iron has low hardness and low fatigue strength.
Properties. Wrought iron has Brinell hardness number of 105; tensile strength of 35,000 psi; specific gravity of 7.7; melting point of 2750°F (1510°C); and is ductile and corrosion resistant.
Appearance test. The appearance of wrought iron is the same as that of rolled, low-carbon steel.
Fracture test. Wrought iron has a fibrous structure due to threads of slag. As a result, it can be split in the direction in which the fibers run. The metal is soft and easily cut with a chisel, and is quite ductile. When nicked and bent, it acts like rolled steel. However, the break is very jagged due to its fibrous structure. Wrought iron cannot be hardened.
Spark test. When wrought iron is ground, straw-colored sparks form near the grinding wheel, and change to white, forked sparklers near the end of the stream.
Torch test. Wrought iron melts quietly without sparking. It has a peculiar slag coating with white lines that are oily or greasy in appearance.