26-06-2012, 01:27 PM
Project Report on Cast Iron Pipe
Cast Iron Pipe.docx (Size: 1.53 MB / Downloads: 87)
Introduction
Cast iron pipe is a historical pipe which found widespread use as a pressure pipe for transmission of water, gas and sewage, and as a water drainage pipe, during the 19th and 20th centuries. It comprises predominantly a gray cast iron tube and was frequently used uncoated, although later developments did result in various coatings and linings to reduce corrosion and improve hydraulics. Cast iron pipe was gradually superseded by ductile iron pipe, which is a direct development, with most existing manufacturing plants transitioning to the new material during the 1970s and 1980s.
Early Use
The first use of cast iron pipe is not recorded. Cast iron tubes were first manufactured in the 14th century in Europe for cannon and it is presumed that similar tubes would have found use as water pipes at the same time; however, it was not until 1455 in Siegerland that the first officially recorded cast iron water pipe was produced for use in Dillenburg Castle (since destroyed).
The oldest extant water pipes date from the 17th century and were installed to distribute water throughout the gardens of the Chateau de Versailles. These amount to some 35 km of pipe, typically 1m lengths
With flanged joints. The extreme age of these pipes make them of considerable historical value. Following extensive refurbishment in 2008 by Saint-Gobain PAM, 80% remain original.
Manufacture
Vertically Cast
The first cast iron pipe was produced in horizontal molds which resulted in an uneven distribution of metal around the pipe circumference. In 1845, the first pipe was cast vertically and by the turn of the century, all pipes were manufactured to this method.
Centrifugally Cast
Subsequent to its invention by Dimitri Sensaud deLavaud, a French-Brazilian, in 1918, much cast iron pipe manufacture shifted to the dramatically different technique of centrifugal casting. Modern ductile iron pipe production continues to use this method of casting.
Metals used:
During the process of smelting, the liquid iron absorbs and combines with a considerable quantity of carbon, sulphur, silicon, phosphorus, and manganese from the ore and coke. Some of the carbon is chemically combined with the iron in the form of iron carbide, while the remainder exists as a form of free carbon called graphite. While the fusibility (ease of melting) of iron depends upon the percentage of carbon that it contains, too high a per cent of carbon weakens the iron. The slower a casting cools, the larger the amount of graphite formed and thus the softer the iron. Pig iron is graded according to the appearance of its fracture. All iron produced in the blast furnace whether in molten state or cast into pigs is called pig iron. Iron ore, coke and limestone are charged into a blast furnace to produce pig iron. The composition of pig iron varies with the quality of the ore and operation of the blast furnace. Due to the reducing conditions in the furnace, the impurities in the ore gets reduced and incorporated with the iron. These impurities are mainly phosphorous, silicon, manganese, sulphur and carbon. The composition of slag, regulation of blast furnace and percentage of fuel determine these impurities. These must be removed because they affect the properties of iron. Pig iron can be regarded as the impure form of cast iron and is the raw material for all the iron and steel products.
IMPURITIES IN PIG IRON AND THEIR EFFECTS:
PHOSPHORUS: the quantity of phosphorus present in pig iron varies from 0.1% to 2%.it combines with iron to form Fe3 which embrittles cast iron. Phosphorus is introduced into the iron from phosphate in the ore. Phosphates get reduced in the reducing temperature of blast furnace and phosphorus is formed. This phosphorus is combined with the iron and some amount of it gets oxidized into P2O5.if this is formed it is removed by slag which is basic in character. Thus the amount of phosphorus is reduced and kept as low as possible.
Phosphorus in pig iron increases the fluidity of molten iron and thus makes the filling of the moulds in a better way.
SULPHUR: It is introduce from coke used in production of pig iron. Its quantity varies from 0.4 to 1%.Presence of manganese in iron lowers the % of sulphur by combining with sulphur in iron and forming MnS . This combines with CaO and is remove thus sulphur is removed from their It may be noted that FeS has low melting point and it forms between the grains that make up the alloy. Iron sulphide being very brittle, the whole alloy becomes brittle
Presence of sulphur tends to make iron hard and produces unsound castings. It makes steel either cold short or hot short and that steel cannot be hot or cold worked.
SILICON: Percentage of silicon present in pig iron varies from 1 to 4%.Source of silicon in iron is the presence of it in any of its raw materials. At low temperatures some silicon is oxidized into silica and basic slag removes it. Thus silicon is eliminated from the iron.
Silicon affects the hardness and strength of the iron. Both of these properties worsen by the presence of silicon in iron. It also increases the electrical resistance. silicon promotes the decomposition of cementite to form graphite..
MANGANESE: The quantity of manganese varies from 0.2 to 1.5%.The source of this impurity is from its ore. Manganese dioxide in ore is reduced at higher temperature as the reduction reaction is endothermic in nature. Mn thus formed gets mixed with the iron. Some of it is removed as acid slag.
Presence of Mn in iron reduces the sulphur content in the iron by forming MnS thereby improving the quality of alloy since MnS is not as harmful as FeS. Mn increases the tensile strength of iron.