The heating rate has a great influence on the location of the phase change critical point, so that the phase change proceeds within a temperature range. Therefore, the heating rate has a great influence on the quenching heating temperature.
Each steel grade has a certain quenching heating temperature range. Only by heating and quenching within a temperature range can satisfactory structure and performance be obtained.
When the heating rate is constant, if the selected quenching temperature is lower than the optimal temperature, because the phase transformation is incomplete, the thermal structure is austenite plus ferrite, or austenite plus pearlite, then the structure after quenching If martensite is added to ferrite or martensite is added to pearlite, the hardness will decrease; if the quenching heating temperature is higher than the optimal temperature, the hot austenite grains will grow, and the medium will be obtained after quenching. Needle or thick needle martensite, if it is high carbon steel, residual austenite will appear, and the surface hardness will decrease.
As the heating rate increases, the quenching heating temperature range moves to a higher temperature region, and the quenching heating temperature range becomes wider.
During production time, if the optimal quenching temperature range for a certain steel grade is determined, but because the heating speed (that is, the specific power when the part is heated) is greater or less than the corresponding heating speed, unreasonable or undesirable results will also occur. Quenching tissue. If the heating rate is less than the corresponding heating rate, and the workpiece is heated to the determined quenching temperature, an overheated structure will be obtained after quenching; if the heating rate is greater than the corresponding heating rate, when the workpiece is heated to the determined quenching temperature, an underheated structure will be obtained after quenching. Quenching structure, therefore, when selecting the quenching temperature for induction heating, not only the composition of the material and the original structure must be considered, but also the influence of the heating speed must be taken into account.
The reasonable selection of quenching heating temperature is mainly determined by metallographic method and Vickers hardness method.
The selection of induction heating temperature is customarily about 50 to 100°C higher than the furnace heating and quenching temperature of the material.
After long-term experiments, the heating temperature ranges of different steel grades at different heating speeds were obtained. If you want to know more, you can contact us freely.
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