Cold working process - produces internal stress in metals - Material Science

Q.  Which of the following statements is/are true for cold working process?

1. Cold working process does not provide good surface finish
2. Cold working process produces internal stress in a metal
3. Fatigue strength of metals can be improved
4. Cold working process cannot take place below recrystallization temperature

- Published on 05 Aug 15

a. statement 1 and statement 2
b. statement 2 and statement 3
c. statement 3 and statement 4
d. all the above statements are true

ANSWER: statement 2 and statement 3
 

    Discussion

  • Sravanthi   -Posted on 06 Oct 15
    - A piece of metal deforming plastically below recrystallization temperature is called as cold working process. Cold working process produces good surface finish and hot working process do not have good surface finish.

    - Amount of work done on metal is stored internally as strain-energy. In any cold worked metal, this stored energy produces internal stresses. Heat treatment process such as annealing can be used to remove these internal stresses otherwise these metals are liable to crack when subjected to heat treatment.

    - Cold working process increase fatigue strength, tensile strength and electrical resistance of metals and decreases creep resistance and ductility.

    - Hot working process takes place above recrystallization temperature and they do not produce internal stresses. It has no effect on hardness, fatigue and tensile strengths.

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