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Vacuum Heat Treatment Furnace

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What Requirements Does the Deep Carburizing Heat Treatment Process Have on the Heat Treatment Equipment?

1. Requirements For Temperature and Carbon Potential Control Methods

1).Temperature control method. The temperature control adopts the main control method inside the furnace (most domestic equipment adopts the main control method outside the furnace). Furnace main control refers to a temperature control method that uses a reasonable mathematical model to automatically adjust the power of each heating zone based on the difference between the temperature detected by the furnace cover thermocouple and the target temperature, thereby controlling the furnace temperature . The advantage is that the furnace temperature can be controlled more accurately, the deviation of the furnace temperature can be reduced, and the reliability of the furnace temperature can be significantly improved.

2).Carbon potential control method. The carbon potential control adopts the method of continuously controlling the carbon potential. It includes two aspects:

①The enrichment agent is continuously dripped in different proportions through the continuous adjustment of the proportional valve.

②The continuous adjustment of the proportional valve is used to realize the continuous injection of air in different proportions.

This continuous control of the carbon potential can effectively avoid the overshoot or undershoot of the carbon potential caused by the on-off control of the carbon potential, and the carbon potential deviation can be controlled within ±0.02%Cp. The conventional carburizing equipment often relies on the on-off of the control solenoid valve to intervene in the dripping or stopping of the enrichment agent to achieve the adjustment of the carburizing potential (It can be called on-off control of the carbon potential). Because the formation of the carbon potential requires a process, and this process often causes a delay in the adjustment of the carbon potential, therefore, it is very easy to cause the carbon potential to overshoot or be too low in a certain period of time, which affects the quality of carburizing.

2. Large-scale Well-type Carburizing Furnace and Carburizing Process

1).Carbon potential control method. Use continuous carbon potential control.

2).Material and carburizing process

Eg: Large gear, the material is 20CrMnMoA

Requirements: The depth of the carburized layer is 6.0mm (550HV). Strong infiltration 930℃×115h, carbon potential 1.20%; diffusion 930℃×35h, carbon potential 0.85%; high temperature tempering 660℃; quenching 850℃; low temperature tempering 200℃.

3. Application of nitrogen-methanol atmosphere in deep carburizing

Compared with other endothermic atmospheres, the nitrogen-methanol atmosphere can not only uniform the carbon potential in the furnace, but also has higher safety and good oxidation ability. Isopropanol is used as the enriching agent, the infrared analyzer detects the percentage of CO in the furnace, and the L-probe controls the carbon potential. Since the CO in the nitrogen-methanol atmosphere is used to participate in the calculation, the percentage of CO in the atmosphere plays a particularly important role in the stability of the carbon potential. Through the steel foil measurement test, by controlling the CO, the fluctuation and deviation of the carbon potential when CO participates in the calculation are small.