What engineering properties are likely to decline during the cold working of a metal? Best answer on the web

Posted in: darrelrussell.com edit
07 Jan 2009
  • What engineering properties are likely to decline during the



    cold working of a metal?


  • As the metal is formed into the desired shape or form, the metal becomes more brittle and less malleable. Over time, the metal could develop a crack and possibly cause damage to the structure it was used for. This is called fatigue cracking.


  • *Cold rolling is a metal working process in which metal is deformed by passing it through rollers at a temperature below its recrystallization temperature.

    *Cold rolling increases the yield strength and hardness of a metal by introducing defects into the metal's crystal structure.

    *These defects prevent further slip and can reduce the grain size of the metal, resulting in Hall-Petch hardening.

    *Cold rolling is a method of cold working a metal. When a metal is cold worked, microscopic defects are nucleated throughout the deformed area. These defects can be either point defects (a vacancy on the crystal lattice) or a line defect (an extra half plane of atoms jammed in a crystal). *As defects accumulate through deformation, it becomes increasingly more difficult for slip, or the movement of defects, to occur. This results in a hardening of the metal.

    *If enough grains split apart, a grain may split into two or more grains in order to minimize the strain energy of the system. When large grains split into smaller grains, the alloy hardens as a result of the Hall-Petch relationship. If cold work is continued, the hardened metal may fracture.

    *During cold rolling, metal absorbs a great deal of energy, some of this energy is used to nucleate and move defects (and subsequently deform the metal). The remainder of the energy is released as heat.

    *While cold rolling increases the hardness and strength of a metal, it also results in a large decrease in ductility. Thus metals strengthened by cold rolling are more sensitive to the presence of cracks and are prone to brittle fracture.


  • it decreases the ductility of the metal

    it also decreases the ageing time of the metal