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Quenching heating method and parts protection

  • Author:kerry
  • Release on:2021-06-21

Quenching and tempering are the most easy processes to cause deformation and cracking of parts.  For some small die casting molds, slender cylindrical parts or high alloy steel mold parts, direct heating quenching mode should be avoided. Instead, it should be preheated to 520 to 580 degrees Celsius first, and then heated to quenching temperature in a medium-temperature salt bath furnace.  Practice has proved that using this heating method of parts, than directly in the electric furnace or furnace heating quenching, deformation is obviously smaller, cracking can be basically avoided. 

In quenching, if the heating temperature of austenitic parts is too high, the grain size will be coarse, and it is easy to cause oxidation, decarbonization and other phenomena, leading to deformation and cracking of parts.  And if the temperature is low, it will cause the shrinkage of the inner hole of the parts, and the size of the aperture will become smaller.  Therefore, the temperature upper limit should be selected as far as possible for quenching within the allowable range of heating temperature.  For alloy steel, heating temperature is high, will cause the expansion of the inner hole, pore size becomes larger, the best choice is to allow the lower limit of temperature. 

In addition, in quenching and tempering treatment, it is necessary to take effective measures to protect the parts that are prone to deformation and cracking, so that the shape and section are symmetrical, and the internal stress is balanced.  This is especially true for parts with complex shapes.  Commonly used protection methods include bundle method, filling method and blocking method.