identify the given irons
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TYPES OF IRON
There are two major types of iron produced: wrought iron and cast iron. Within those, cast iron includes its own family of metals.
Wrought iron
The first type of iron produced and worked by blacksmiths was wrought iron. It is virtually pure elemental iron (Fe) that is heated in a furnace before being wrought (worked) with hammers on an anvil. Hammering iron expels most of the slag from the material and welds the iron particles together.
During the industrial revolution and the associated acceleration of construction activities, a new use for wrought iron was discovered. Its high tensile strength (resistance to breaking when under tension) made it ideal to use for beams in large construction projects such as bridges and high-rise buildings. However, the use of wrought iron for this purpose was largely abandoned in the early 20th century when steel products were developed with superior performance to iron for construction applications.
Wrought iron has become famous for decorative pieces. Churches of the 15th and 16th century contain fine wrought iron pieces produced by skilled artisans. In the modern world, railings, doors, and benches are still made from wrought iron as custom pieces.
Cast iron
Cast iron is produced by smelting iron-carbon alloys that have a carbon content greater than 2%. After smelting, the metal is poured into a mold. The primary difference in production between wrought iron and cast iron is that cast iron is not worked with hammers and tools. There are also differences in composition—cast iron contains 2–4% carbon and other alloys, and 1–3% of silicon, which improves the casting performance of the molten metal. Small amounts of manganese and some impurities like sulfur and phosphorous may also be present. Differences between wrought iron and cast iron can also be found in the details of chemical structure and physical properties.
It is the combination of high carbon content, and the presence of silicon, that gives cast iron its excellent castability. Various types of cast irons are produced using different heat treatment and processing techniques, including gray iron, white iron, malleable iron, ductile iron, and compacted graphite iron.
Cast iron bridge
Cast iron design details are produced by smelting metal and pouring it into a mold.
Gray iron
Gray iron is characterized by the flake shape of the graphite molecules in the metal. When the metal is fractured, the break occurs along the graphite flakes, which gives it the gray color on the fractured metal’s surface. The name gray iron comes from this characteristic.
White iron
With the right carbon content and a high cooling rate, carbon atoms combine with iron to form iron carbide. This means that there are little to no free graphite molecules in the solidified material. When white iron is sheared, the fractured face appears white due to the absence of graphite. The cementite microcrystalline structure is hard and brittle with a high compressive strength and good wear resistance. In certain specialized applications, it is desirable to have white iron on the surface of the product. This can be achieved by using a good conductor of heat to make part of the mold. This will draw heat out of the molten metal quickly from that specific area, while the rest of the casting cools at a slower rate.
Malleable iron
White iron can be further processed into malleable iron through a process of heat treatment. An extended program of heating and cooling, results in the breakdown of the iron carbide molecules, releasing free graphite molecules into the iron. Different cooling rates, and the addition of alloys, produces a malleable iron with a microcrystalline structure.
Ductile iron (Nodular iron)
Ductile iron, or nodular iron, obtains its special properties through the addition of magnesium into the alloy. The presence of magnesium causes the graphite to form in a spheroid shape as opposed to the flakes of gray iron. Composition control is very important in the manufacturing process. Small amounts of impurities such as sulfur and oxygen react with the magnesium, affecting the shape of the graphite molecules. Different grades of ductile iron are formed by manipulating the microcrystalline structure around the graphite spheroid. This is achieved through the casting process, or through heat treatment, as a downstream processing step.
Compacted graphite iron
Compacted graphite iron has a graphite structure and associated properties that are a blend of gray and white iron. The microcrystalline structure is formed around blunt flakes of graphite which are interconnected. An alloy, such as titanium, is used to suppress the formation of spheroidal graphite. Compacted graphite iron has a higher tensile strength and improved ductility compared to gray iron.