Hot rolling and cold rolling process

Replies

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  N.Gowtham Raj

  Hot rolling process takes place at a temperature greater than re-crystallization temperature of the material. And do a detrimental layer called ' scale' is formed on the surface of the part which in turn governs the surface roughness.
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  Void Runner

  ^The above post is the correct answer as far as your exam is concerned. But this question is a good example of why there is no such thing as one single answer. If you ask me to answer, I'll come across a completely different explanation and still make sense 😁
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  zaveri

  Void Runner

  ^The above post is the correct answer as far as your exam is concerned. But this question is a good example of why there is no such thing as one single answer. If you ask me to answer, I'll come across a completely different explanation and still make sense 😁

  So what is your answer ?
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  Void Runner

  #-Link-Snipped-# ^The smoothness or roughness of a surface is defined by the structure and form (crystalline/amorphous) of the surface material. Those surfaces which have similar bonding structure and crystal planes along the length of the surface axis will generally be more smooth.
  
  Now, hot rolling vs. cold rolling - Each time you "press" or "roll" something into a substrate, you are giving some energy to it. Energy given to an atom or molecule on the surface tends to break the bonds and reorient the crystal planes. When the rolling is HOT, you add heat energy to this mix - more bonds broken per unit second. The net result is that the surface becomes rougher due to the presence of different bond structures and different crystal planes. Thus, hot rolling results in a rougher surface than cold rolling.
  
  (The above is from the perspective of physical chemistry).