Deformation of Metals

Deformation is the change in dimension or forms of matter under the action of the applied forces. Deformation is caused either by the mechanical action of the external forces or by various physical and physio-chemical processes. Deformation may be permanent or temporary depending upon the type of deformation whether it is plastic or elastic. So metal deformation are of following two types:  (a)      Elastic deformation  (b)      Plastic deformation Elastic Deformation – The deformation is called elastic if the strain or deformation produced in the material corresponding to a given stress completely…

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Basic Modes of Plastic Deformation – Deformation by Slip & Deformation by Twinning

Deformation by Slip Slip is defined as sliding of blocks of crystal over one another along definite crystallographic planes called slip planes. So it is the relative displacement along a definite direction. When slip takes place, one part of the lattice moves with respect to the other. Generally slip plane is the plane of highest atomic density and slip direction is the closest packed direction within the slip plane. This is because the bond between these planes is weakest, so when force is applied in proper direction, relative movement takes place very easily. The shear stress…

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Property Changes by Deformation

Due to the cold working of metals, there arise a large number of dislocation and distortions of planes. Cold working of metals or alloys increases the hardness, yield strength, ultimate strength and electrical resistance whereas the ductility and plasticity are decreased. Following are some important changes in properties in metals due to plastic deformation. Work (Strain) Hardening Strain hardening or work hardening is the phenomenon whereby a ductile metal becomes harder and stronger as it is plastically deformed. The temperature, at which deformation takes place is cold, relative to the…

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Production Process and Classification of Pig Iron

Ferrous metals are iron based metals which include all varieties of iron and steels. Ferrous basically refers to iron. Iron is the name given to pure ferrite (Fe), as well as to mixtures of this ferrite with about 1.7% Carbon also known as Pig Iron. Pig iron is the basic raw material which is produced from iron ore in the blast furnace. Cast iron, wrought iron and steels are made from Pig iron. Cast iron is produced in cupola furnace. Cast iron can be cast but it cannot be forged….

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Production Process and Properties of Cast Iron

Cast iron is an alloy of iron and carbon. It is obtained by re-melting pig iron with coke, limestone and steel scrap in a furnace known as ‘‘cupola”. The carbon percentage varies from 1.7 to 4.5 %. It also contains small amount of silicon, manganese, phosphorus and sulphur. Production of Cast Iron Cast irons are normally produced by melting Pig iron in cupola furnace with coke, lime stone and other fluxes. The limestone and fluxes aid in separating the impurities from the pig iron. The limestone also acts as an agent…

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Puddling Process of Wrought Iron

Wrought iron is virtually pure iron, containing a large number of minute threads of slag lying parallel to each other, thereby giving the metal a fibrous appearance when broken. It contains negligible carbon percentage and therefore, does not harden when quenched in water. Wrought iron is produced by puddling process in reverberatory furnace. Puddling Process              Wrought iron is produced in reverberatory furnace by puddling process which is similar to open hearth furnace with combustion taking place at one end only. The furnace is lined with iron oxide. (in the…

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Effect of Alloying Metals

An alloy is a substance having metallic properties. Alloying is done by combining one metallic element with one or more metallic or non-metallic elements. In an alloy, the metallic or non-metallic elements do not exist or operate in distinct layers when solid. An alloy when solid may be composed of eutectic alloy or eutectoid, solid solution, chemical compounds with each other or with pure metals. Alloying is done by the following four methods Melting two metals separately and mixing them. Melting one of the metals having higher melting point than…

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Effects of Alloying Elements on Carbon Steel

When certain special properties are required, some alloying elements are added to carbon steels.  The alloying element may be Ni, Cr, Mn, Va ,W etc. The steel thus obtained are called alloy steels. The purposes of alloying elements are to improve the following properties: Hardness, toughness, and tensile strength Wear resistance Corrosion resistance Ability to retain shape at high temperature Machinability Resistance to distortion at high temperature Fine grain size to steel Elasticity Case hardening Cutting ability Nickel – Nickel is added to steel to: Increase toughness Increase tensile strength, yield…

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Engineering 

Alloy Steel Elements and Properties

Nickel Steel – The percentage of Nickel (Ni) varies from 2 to 45. 2%Ni makes steel more suitable for rivets, boiler plates, bolts and gears etc. Ni from 0.3 to 5% raises elastic limit and improves toughness. Steel containing 20% Nickel has very high tensile strength. 25% Ni makes the steel particularly stainless and might be used for I.C. engine valves, turbine blade etc. If Ni is present up to 27%, it makes the steel non-magnetic and non-corrodible. Invar (Ni 36%) and super-invar (Ni 31 %) are the popular materials for…

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Engineering 

Classes of Steel and Its Uses

Steel is an alloy of iron and carbon with content upto a maximum of 1.5%. The carbon present in the form of iron carbide, because of its ability to increase the hardness and strength of the steel. Other elements such as Silicon, Sulphur, Phosphorus and Manganese are also added to improve the various qualities of steels. Carbon present in the steel is in combined form. Plain Carbon Steel Plain carbon steels are those which contain primarily Iron and Carbon. Silicon, Manganese, Sulphur and Phosphorus are present but these are considered…

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