About forging "zero heat preservation" quenching

During the heat treatment of forgings, because of the large power of heating electric furnace and long time of heat preservation, energy consumption is huge in the whole process. For a long time, how to save energy during the heat treatment of forgings has been a difficult problem.

The so-called "zero heat preservation" quenching refers to the heat treatment process of quenching cooling immediately without heat preservation when the forging is heated and its surface and core reaches the quenching heating temperature. According to the traditional austenite theory, the forging must be held for a long time during the heating process in order to complete the nucleation and growth of austenite grains, the dissolution of residual cementite and the homogenization of austenite.

The current quenching and heating process of forgings is produced under the guidance of this theory. Compared with the current quenching process, "zero heat preservation" quenching saves the heat preservation time required by the homogenization of austenite structure, which can not only save energy by 20%-30% and improve production efficiency by 20%-30%, but also reduce or eliminate the oxidation, decarbonization, deformation and other defects of forging in the heat preservation process, which is conducive to the improvement of product quality.

When carbon steel and low alloy structural steel are heated to Ac1 or Ac2, the homogenization of austenite and the dissolution of carbides in pearlite are faster. When the size of steel parts is in the range of thin parts, the calculation of heating time does not need to consider the heat preservation, that is, to achieve zero heat preservation quenching. For example, when the diameter or thickness of 45 steel workpiece is not more than 100mm, the temperature of the surface and core is almost reached at the same time in the air furnace, so the uniform time can be ignored. Compared with the traditional production process with large heating coefficient (R =aD), the quenching heating time can be shortened by nearly 20%-25%.

The theoretical analysis and experimental results show that it is feasible to adopt "zero heat preservation" for quenching and normalizing of structural steel. Especially 45, 45Mn2 carbon structural steel or single element alloy structural steel, the "zero insulation" process can ensure its mechanical properties requirements; 45, 35CrMo, GCrl5 and other structural steel forgings, using "zero heat preservation" heating than traditional heating can save heating time, total energy saving 10%-15%, improve work efficiency 20%-30%, at the same time, "zero heat preservation" quenching process helps to refine grain, improve strength.