Zero heat preservation, quenching and normalizing forgings

In the heat treatment of forging, due to the large power of the heating furnace and long insulation time, the energy consumption is huge in the whole process, in a long period of time, how to save energy in the heat treatment of forging has been a difficult problem.

The so-called “zero insulation” quenching, is to point to the forging heating, its surface and core to reach the quenching heating temperature, no insulation, immediately quenching cooling process.According to the traditional austenitic theory, the forging must have a long insulation time in the heating process, so as to complete the nucleation and growth of austenitic grains, the dissolution of residual cementite and the homogenization of austenitic.The present quenching and heating technology of forgings is produced under the guidance of this theory.Compared with the current quenching process, “zero heat preservation” quenching saves the time of heat preservation required by the homogenization of austenitic structure, not only can save 20%-30% of energy, improve the production efficiency 20%-30%, but also can reduce or eliminate the defects of oxidation, decarbonization, deformation and so on, which is conducive to the improvement of product quality.

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When carbon steel and low alloy steel are heated to Ac1 or Ac2, the homogenization process of austenite and the dissolution of carbides in pearlite are faster.When the steel size belongs to the thin part range, the calculation of heating time does not need to consider the thermal insulation, that is, to achieve zero thermal insulation quenching.For example, when the diameter or thickness of 45 steel workpiece is no more than 100mm, heating in the air furnace, the temperature of the surface and the core is almost reached at the same time, so its uniform time can be ignored, compared with the traditional production process (r=aD) with large heating coefficient, can be reduced by nearly 20%-25% quenching heating time.

The theoretical analysis and experimental results show that it is feasible to adopt “zero insulation” in quenching and normalizing heating of structural steel.In particular, 45, 45 mn2 carbon structural steel or single element alloy structural steel, the use of “zero insulation” process can ensure the mechanical properties of the requirements;45, 35CrMo, GCrl5 and other structural steel workpiece, the use of “zero insulation” heating than the traditional heating can save heating time of about 50%, the total energy savings of 10%-15%, improve the efficiency of 20%-30%, at the same time “zero insulation” quenching process helps to refine grain, improve the strength.

(From:168 forgings net)

Post time: Mar-26-2020
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