Cast Iron

Cast Iron

The  earliest successful iron founding has been credited to the ancient civilizations which occupied the plains of Mesopotamia.

It was here that the Babylonians , Assyrians , and Chaldeans evolved the metallurgical knowledge necessary to make castings from high carbon iron. there is evidence that the Chinese capitalized on early discoveries which were undoubtedly passed along by migrating Mesopotamian craftsmen . the Chinese became the first people to produce iron castings successfully and regularly. Ancient records indicate that the Chinese were making iron castings as early as the 6th century before Christ. Many of the old castings were of utilitarian nature such as cooking stoves , kitchen utensils , bells, agricultural implements , and tools, and ornamental objects. Various Chinese temples with cast iron roofs a thousand years old appear to be in first class condition today .

In the 12th century A.D., iron founding progress tapered off in china .the scene then shifted to European countries , principally Germany , Belgium , France , Italy , and England .

Even as late as the 1600’s iron was considered a luxury item ,and during the region of Edward III , iron pots and skillets were numbered among the royal jewels .by the 1700’s European production included bells, cannon , gunshot , pipe, stoves, and cast iron cooking utensils.

The first casting made in American was produced at the Saugus iron works near lynn , mass., shortly after its establishment in was not long afterward that foundries appeared in Connecticut , Rhode Island ,New jersey, Virginia ,the Carolinas  , Pennsylvania ,and Maryland . the foundries supplied neighboring farmers and industries with cast iron cooking utensils , stoves , tools, and agricultural implements .As the foundry industry grew in America .it became a real threat  to England’s profitable colonial export business. In 1750, in order to protect her markets, the English government  passed laws requiring that American-made pig iron be shipped to England to be cast into finished products. This burdensome restriction is believed to be one of the important provocations which finally led to the Revolutionary war.

When war struck ,foundry men were both generous financially and active politically. Many served as military leaders in trying to gain independence from England .six prominent foundry men,including colonel george  taylor , signed the declaration of Independence in 1776.

Today designers ,engineers ,and users recognize the unique properties of cast iron as it fills a very important role in our modern world. There are cast irons available with excellent ductility and heat resistance ,cast irons which can damp out vibrations in machinery.

Cast irons is essentially an alloy of carbon , silicon, and iron in which more carbon is present than can be retained in solid solution in austenite at the eutectic temperature . thus cast irons usually contain some decomposition products such as free graphite or cementite  . the carbon content in cast irons is usually more than 1.7 percent and less than 4.5 percent. The high percentage of carbon renders the cast iron brittle and unworkable except by casting.

Cast iron always contains a certain amount of manganese , phosphorus  and sulfur because of the refining methods used in its production. Special alloying elements such as copper ,molybdenum, nickel and chromium are added for the purpose of altering the chemical and mechanical properties available in cast iron .However , they may be classified into one of the following main groups:1-gray cast iron, 2-white cast iron 3-malleable iron 4- ductile (nodular)iron 5-alloy cast irons.

The terms gray and white , when applied to cast iron ,refer to the appearance of the fracture of a casting . the gray iron fractures with a dark gray fracture, whereas the white cast iron shows a light gray , almost white fracture . malleable iron gets its name from its ability to bend or undergo permanent deformation before fracturing. ductile iron can be produced with higher yield tensile strength than malleable iron .alloy cast irons are those to which chromium , nickel , molybdenum , copper ,or other elements have been deliberately added to modify the properties attainable by the normal elements-iron, carbon , silicon, manganese , phosphorus , and sulfur .For example: nickel may be added to gray cast iron in sufficient amount as to lower the eutectoid transformation temperature to such a degree that austenite will be retained at room temperature . this cast iron has unusual magnetic properties and corrosion resistance and is known as austenitic cast iron.


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