Regarding energy-saving issues in heat treatment processes, let's first talk about the advantages of quenching processes.
Research has confirmed that hypoeutectoid steel α+γ Heating and quenching in the two-phase zone (i.e. sub temperature quenching) can improve the strength and toughness of steel, reduce the brittle transition temperature, and eliminate tempering brittleness. The quenching heating temperature can be reduced by 40 ℃.
The quenching heating temperature for general hypoeutectoid carbon steel is above Ac3 at 30-50 ℃, and the heating temperature for quenching of eutectoid and hypereutectoid carbon steel is above Ac1 at 30-50 ℃. The use of low-temperature rapid short-term heating and quenching for high carbon steel can reduce the carbon content of austenite
It is beneficial to obtain planar martensite with good matching of strength and toughness, which not only improves its toughness, but also shortens the heating time.
For some transmission gears, carbon nitrogen co infiltration is used instead of carburization, which increases wear resistance by 40% to 60%, fatigue strength by 50% to 80%, and co infiltration time by 50% to 80%. However, the co infiltration temperature (850 ℃) is 70 ℃ lower than the carburization temperature (920 ℃),
At the same time, it can also reduce heat treatment deformation.
shorten the heat time
Production practice has shown that the traditional heating time determined based on the effective thickness of the workpiece is conservative, so it is necessary to use the heating and insulation time formula τ=α· Heating coefficient, in K · D α Make corrections. According to traditional process parameters
When heated to 800-900 ℃ in an air furnace, α The recommended value is 1.0~1.8min/mm, which is clearly conservative.
If possible, α A decrease in value can greatly shorten the heating time. The heating time should be determined based on the steel grade, workpiece size, and installation situation
