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Thursday, 12 April 2012

Important basic concepts in Engineering metallurgy: GATE Mechanical

The present resource contains the important basic concepts in Engineering metallurgy in Mechanical Engineering. Note down each concepts which might help in GATE 2013 Mechanical.

  • Delta iron occurs at temperature between 1400 oC and 1539 oC .
  • Gamma iron exists at temperature between 910 oC and 1400 °C .
  • Ferromagnetic alpha iron exists in temperature range below 723 °C .
  • Para-magnetic alpha iron changes to gamma iron at 910 °C.
  • Fatigue failure: Fatigue failure occurs when a part is subjected to compressive stress.
  • Homogeneous : A body having identical properties all over
  • Elastic behavior : If a material recovers its original dimensions, when load is removed.
  • A ductile fracture is characterized by appreciable plastic deformation prior to propagation of crack.
  • Resilience: The ability of a material to absorb energy when deformed elastically 
  • Machining properties of steel can be improved by adding sulphur, lead, phosphorus.
  • Eutectoid steel the percentage of carbon is 0.8%.
  • A cold chisel is made of high carbon steel.
  • An engineer’s hammer is made of forged steel.
  • Cyaniding: The process of adding carbon and nitrogen by heat treatment of steel to increase its surface hardness.
  • Tensile strength of common varieties of cast iron is in the range 840-500 Mpa.
  • In carbon steel casting the percentage of carbon is less than 1.7%.
  • Aluminium alloys for pressure die casting must posses considerable fluidity.
  • Electro forming is Specially valuable for thin walled parts requiring a high order of accuracy and internal surface finish.
  • In power metallurgy the process of heating the cold pressed metal power is called sintering.
  • The hardness of steel increases if it contains martensite.
  • The presence of sulphur in pig iron makes the casting unsound.
  • Compressive strength of grey cast iron in tones per square cm is of the order of 5-7.
  • The machinability of steel can be increased by phosphorous, lead and sulphur.
  • Steel with 0.8% carbon and 100% pearlite is known as eutectoid steel
  • The maximum hardenability of any steel depends on the carbon content.
  • In 18-4-1 high speed steel the maximum percentage is of iron.
  • In compression, a prism of brittle material will break by shearing along oblique plan.
  • Cast-alloy contains nickel and molybdenum.
  • Trimming is a process associated with forging.
  • Addition of lead and bishmuth to aluminium results in improving machinability
  • Foundry crucible is made of graphite.
  • Age-hardening is related with duralumin.
  • For heavy loads in aircraft bearings the malarial used with lead to reduce the risk of seizure, is silver.
  • As compared to steel the tensile strength of wood is generally 1/5.
  • Compressive strength of wood is generally more along the grains.
  • Superconducting property exist at temperatures below 10 K.
  • Weld Decay: The phenomenon of weld decay is associated with stainless steels.
  • Bloom: Bloom are obtained by passing hot ingots through the rolling mills and are of size 150 mm x 150mm to 350mm x 350mm.
  • A knoop indenter is a diamond group to a pyramdidal from.
  • A unit cell that contains nine atoms is known as body centered cubic space lattice.
  • The process commonly used for thermo-plastic material is injection moulding.
  • The most important element that controls the physical properties of steel is carbon.
  • In process annealing process, the hypoeutectoid steel is heated below A1 line with a view to make steel ductile for cold working.
  • The imperfection in the crystal structure of metal is known as dislocation.
  • Polyesters belong to the group of thermosetting plastics.
  • The effect of alloying zinc to copper is to increase strength and ductility (if added up to 10-30 %.)

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