Wrought Iron free essay sample

Microstructure of Wrought Iron Wrought Iron †¢ Wrought iron was once the most important metallic engineering material but it has now been almost totally replaced by the different grades of steel. †¢ A little wrought iron is still made and will probably continue to be made since it possesses certain extremely valuable properties. †¢ Wrought iron is a soft but ductile metal made from pig iron by a low temperature oxidation process called ‘Puddling’. It is not fully molten when withdrawn from the furnace and therefore, always contains some slag. Production of Wrought Iron †¢ Wrought iron is made by removing silicon, sulphur, manganese, phosphorus and carbon from pig iron by oxidation conducted at a temperature of about 1300oC. †¢ Oxygen required for oxidation is supplied partly by the atmospheric air passing through the furnace and partly by the additions of iron oxide. †¢ Silicon, manganese and phosphorus in molten pig iron form SiO2, MnO and P2O5. We will write a custom essay sample on Wrought Iron or any similar topic specifically for you Do Not WasteYour Time HIRE WRITER Only 13.90 / page These oxides combine with iron oxide to form a low melting point liquid slag. †¢ As the iron loses its silicon, manganese, phosphorus and carbon, the melting point of the iron is raised and at the end of the refining the iron is in a pasty condition. †¢ At this stage the iron is gathered in the form of balls, worked as free of slag as possible and dragged out of the hearth. These balls are then placed under a hammer where as much of the slag as possible is squeezed out. The puddling process of smelting iron ore to make wrought iron from pig iron, Tiangong Kaiwu encyclopedia published in 1637, written by Song Yingxing (1587– 1666). Production of Wrought Iron †¢ The squeezed balls are then rolled into â€Å"muck bars† (3/4 to 1 in. thick and 2. 5 to 8 in. wide). The muck bars are then piled, reheated, and rolled into billets, plates, or other suitable shapes †¢ This rolling serves to elongate the slag. The slag, therefore, occurs in the direction of rolling and visible in the longitudinal section as streaks. In the transverse section the slag appears as round grayish dots. †¢ The metal consists of irregular grains of ferrite, which (although deformed in rolling) are no longer elongated, because the temperature at which the rolling has been done was sufficiently high to permit ferrite crystals to recrystallise. (a) (b) Microstructure of Wrought Iron (a) Longitudinal Section (b) Transverse Section Table 1: Chemical compositi on comparison of pig iron, plain carbon steel, and wrought iron[32] Material Pig iron Carbon steel Wrought iron Iron 91–94 98. – 99. 5 99–99. 8 Carbon 3. 5–4. 5 0. 07–1. 3 0. 05– 0. 25 Mangane se 0. 5–2. 5 0. 3–1. 0 0. 01–0. 1 Sulfur 0. 018– 0. 1 0. 02– 0. 06 0. 02–0. 1 Phosphor Silicon us 0. 03–0. 1 0. 002– 0. 1 0. 05–0. 2 0. 25–3. 5 0. 005– 0. 5 0. 02–0. 2 All units are percent weight Properties of wrought iron †¢ the slag inclusions in the wrought metal are largely large inclusions between crystals of the pure metal, in contrast to microscopic inclusions that are present in large quantities in cast steel made by the modern processes. Coagulated slag particles that pierce the metal decrease the mechanical properties (such as rupture strength) of wrought iron to some extent, but on the other hand, they impart some extremely valuable properties. †¢ These include extreme ductility and toughness and remarkable resistance to atmospheric corrosion. years The Delhi iron pillar is an example of the iron extraction and processing methodologies of India. The iron pillar at Delhi has withstood corrosion for the last 1600 years Containing 98% wrought iron The Eiffel tower is constructed from puddle iron, a form of wrought iron