Wrought Iron

Wrought iron is an iron alloy, when compared with steel it has very low carbon content and has the fibrous inclusions called slag. It is tough, malleable, ductile and easily welded. It is commercially pure iron, and it is qualifies no longer, because the current standard for commercially pure alloy requires a carbon content of less than .008 wt%.

The large amounts of steel, wrought iron was the most common form of malleable iron, before the development of effective methods of steelmaking. For manufacturing the steel, the modest amount of wrought iron was used as the raw material, mainly to produce swords, cutlery and blades. In 1860s, the wrought iron reached peak in the usage of ironclad warships and railways, until mild steel came into process. Since then it is declined due to more availability of mild steel. Before they came to made mild steel, the items produced by wrought iron includes rivets, nails, wire chains, bolts, nuts, horseshoes, roof trusses, handrails, railway couplings, water and steam pipes.

Properties of wrought iron

The slag inclusions in wrought iron give it properties not found in other forms of ferrous metal. In includes approximately 250,000 inclusions per square inch. A fracture shows the bluish color with high silky luster and fibrous appearance. Wrought iron lacks in carbon content which is necessary for hardening through heat treatment, but the areas where steel is not known, sometimes tools were cold worked in order to harden them. It is excellent weld ability due to the advantage of its low carbon content in it.

When compared with steel sheet metal, sheet wrought iron cannot bend as steel sheet metal. There are many mechanisms behind the corrosion resistance, the nickel enrichment bands reduce corrosion was found by Chilton and Evans. Surroundings with a high concentration of chlorine ions will tend to decrease wrought iron’s corrosion resistance. Wrought iron can hold plating’s and coatings because it has the rough surface.  For example Zinc finish is approximately 25 – 40 % thicker than the steel.

History

The first indirect process was the osmand process, developed by 1203, but the bloomer production was continued in many places. The blomery and osmand processes were replaced in 15^th century by finery process, it consist of two versions, the German and Waloon. It was replaced by puddling process from 18^th century, with certain variants such as Swedish Lancashire process.  These two are now said to be out dated and wrought is no longer manufactured commercially.

Questions:

• What is wrought iron?
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