Wrought iron
It is a semi-fused mass of iron with fibrous slag inclusions (up to 2% by weight), which give it a wood-like "grain" that is visible when it is etched, rusted, or bent to failure.
[1]: 145 [failed verification] Wrought iron is highly refined, with a small amount of silicate slag forged out into fibers.
[2] The presence of slag can be beneficial for blacksmithing operations, such as forge welding, since the silicate inclusions act as a flux and give the material its unique, fibrous structure.
[3] The silicate filaments in the slag also protect the iron from corrosion and diminish the effect of fatigue caused by shock and vibration.
[4] Historically, a modest amount of wrought iron was refined into steel, which was used mainly to produce swords, cutlery, chisels, axes, and other edged tools, as well as springs and files.
Many items, before they came to be made of mild steel, were produced from wrought iron, including rivets, nails, wire, chains, rails, railway couplings, water and steam pipes, nuts, bolts, horseshoes, handrails, wagon tires, straps for timber roof trusses, and ornamental ironwork, among many other things.
Many products described as wrought iron, such as guard rails, garden furniture,[6] and gates are made of mild steel.
It is the equivalent of an ingot of cast metal, in a convenient form for handling, storage, shipping and further working into a finished product.
Antique music wire, manufactured at a time when mass-produced carbon-steels were available, was found to have low carbon and high phosphorus; iron with high phosphorus content, normally causing brittleness when worked cold, was easily drawn into music wires.
[22] In addition to accidental lumps of low-carbon wrought iron produced by excessive injected air in ancient Chinese cupola furnaces.
Throughout much of the Middle Ages, iron was produced by the direct reduction of ore in manually operated bloomeries, although water power had begun to be employed by 1104.
The process depended on the development of the blast furnace, of which medieval examples have been discovered at Lapphyttan, Sweden and in Germany.
However, the design of a bloomery made it difficult to reach the melting point of iron and also prevented the concentration of carbon monoxide from becoming high.
[1]: 62–66 During the Middle Ages, water-power was applied to the process, probably initially for powering bellows, and only later to hammers for forging the blooms.
It survived in Spain and southern France as Catalan Forges to the mid 19th century, in Austria as the stuckofen to 1775,[1]: 100–101 and near Garstang in England until about 1770;[27][28] it was still in use with hot blast in New York in the 1880s.
The finery always burnt charcoal, but the chafery could be fired with mineral coal, since its impurities would not harm the iron when it was in the solid state.
[31] The introduction of coke for use in the blast furnace by Abraham Darby in 1709 (or perhaps others a little earlier) initially had little effect on wrought iron production.
[32]: 725–726 A number of processes for making wrought iron without charcoal were devised as the Industrial Revolution began during the latter half of the 18th century.
After his return to Sweden in the 1830s, he experimented and developed a process similar to puddling but used firewood and charcoal, which was widely adopted in the Bergslagen in the following decades.
[41][14]: 282–285 In 1925, James Aston of the United States developed a process for manufacturing wrought iron quickly and economically.
[35] Steel began to replace iron for railroad rails as soon as the Bessemer process for its manufacture was adopted (1865 on).
The slag inclusions, or stringers, in wrought iron give it properties not found in other forms of ferrous metal.
[7] A fresh fracture shows a clear bluish color with a high silky luster and fibrous appearance.
[50] They also found that in puddled, forged, and piled iron, the working-over of the metal spread out copper, nickel, and tin impurities that produce electrochemical conditions that slow down corrosion.
[49] Wrought iron may be welded in the same manner as mild steel, but the presence of oxide or inclusions will give defective results.
Although it appears that wrought iron and plain carbon steel have similar chemical compositions, that is deceptive.
Because of the large number of boiler explosions on steamboats in the early 1800s, the U.S. Congress passed legislation in 1830 which approved funds for correcting the problem.
As part of the study, Walter R. Johnson and Benjamin Reeves conducted strength tests on boiler iron using a tester they had built in 1832 based on a design by Lagerhjelm in Sweden.
[5] The importance of ductility was recognized by some very early in the development of tube boilers, evidenced by Thurston's comment: If made of such good iron as the makers claimed to have put into them "which worked like lead," they would, as also claimed, when ruptured, open by tearing, and discharge their contents without producing the usual disastrous consequences of a boiler explosion.
It was found that the stringers common to other wrought irons were not present, thus making it very malleable for the smith to work hot and cold.
