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.

    Hardening::-
    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.

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

    Cyaniding::-
    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.

    Tempering::-
    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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