At present, domestic automobile factories have introduced many foreign models, and the technical requirements of gear materials meet the international standards. Specific requirements for stable hardenability of H steel (narrow band low carbon alloy carburized steel) has caused widespread attention by steel mills and corresponding departments. It is believed that after a period of time, through the technical transformation of steel mills and the use of advanced technology, the quality of forging blank gear materials will have a big increase. By then, coupled with the simultaneous adoption of advanced technology in the automobile industry, the quality of automobile gears will have improved greatly.
After isothermal annealing of gear forging blanks (refers to the general alloy carburized steel, for some high alloy carburized steel, isothermal annealing is also difficult to avoid the formation of bainite, need to increase the high temperature tempering process) not only to ensure the excellent cutting performance, but also because it obtains uniform organization, the dimensional stability after carburizing quenching is also of great help. Of course, to make the gear in the process of carburizing quenching deformation is small and stable, but also need the material itself hardenability can be stable, parts in the bottom plate swing uniform to ensure the uniformity of quenching cooling, as well as the cooling process of the choice of cooling oil, oil temperature, stirring intensity control.
When these blanks are loaded into the furnace, the weight of each part is the same to ensure the same cooling conditions. Through this treatment can avoid the banded structure, obtain ferrite - pearlite mixed structure, hardness of 140~170HIB, ensure the excellent cutting performance, parts surface finish is good, the tool life is longer.