Heat treatment Process- heat treatment of steel

Heat treatmentProcess


  • Annealing:-
    Quenching medium – furnace
    Full annealing – ductility, and toughness
    Process of annealing – relieving
    Spherodise tunneling – machinability increases
    Diffusion annealing – To homogenized the chemistry of the material.Normalizing::-
    a. Quenching medium – Air
    b. Produce hard surface and tough core.
    c. Normalising gives a more homogenized and refined grain structure than annealing.
    d. Normalizing is fast, efficient, and less costly.

    1.The objective of hardening is to produce martensite.
    2.Quenching medium::-
    3.Water- Deepa blanket from(HT 2) non-uniform cooling.
    4.Salt bath- decreases the tendency of vapor blanket formation.
    5.Oil bath- uniform cooling
    6.Only medium carbon steel can be hardened.

    Case hardening::-
    Process of increasing the hardness of the only surface by the process of diffusion of carbon and nitrogen.

    A) Pack carburizing – 50% charcoal
    B) Liquid carburizing – 90% NaCN
    C) Gas carburizing – gas(CH4)

    30%NaCN, NaCl,Na2CO3,

    Flame hardening::-
    Carburizing flame( 2900’C)
    Neutral flame ( 3150’C)
    Oxidizing flame( 3500’C)

    Induction hardening
    A faster method of case hardening.
    Medium carbon steel can be hardened by this technique.
    The copper induction coil is used in induction hardening for application over camshaft, crankshaft.

    Process of introducing toughness.
    High-temperature tempering( 500- 650’C): Sorbate.
    Medium temperature( 350- 500’C): Toroostrite Spring and dies.
    Low temperature(on250′): Martensite is heated at( 250’c) 250′ and coded slowly to relevance internal speed

    Defect in material::-
    a)Point defect:-
    b)Vacancy defect.
    c)Internal defect.
    d)Substitutional defect.
    e)Frenkel defect.
    f)Schottky defect.

    Surface defect::-
    1.Grain boundary defect.
    2.Twin boundary defect.
    3.Tilt boundary defect.
    4.Stacking fault.

    Line defect::-
    1.Edge dislocation defect.
    2.Screw dislocation defect. 

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