Carbonization stage:
1. After the temperature of the well furnace reaches the carburizing temperature, record the time to reach the temperature, change the amount of carburizing agent droplets, continue to maintain insulation and exhaust for 30-45 minutes, take gas for analysis, when the CO2 volume fraction of the furnace gas is less than 0.5%, enter the carburizing stage, change the amount of carburizing agent droplets, close the exhaust hole, make the combustion flame length reach 100-150mm, the combustion flame is bright yellow, no bright sparks are emitted, open the U-shaped pressure gauge, and control the furnace pressure at 250-400Pa.
2. Place two outer specimens into the outer specimen hole, with a depth of generally 100-200mm from the furnace. The outer specimen hole should be plugged with asbestos rope to prevent air leakage and heat dissipation.
3. Check the temperature and pressure of the well furnace every 15 minutes and calibrate the drip rate using a gauge. The fluctuation range shall not exceed ± 5 drops/min of the specified value, and the carburizing atmosphere shall be analyzed, and the CO2, H2O, and O2 values in the atmosphere shall be strictly controlled. When using methanol and kerosene as infiltration agents, the composition of the furnace gas should be controlled at:
ФCnH2n+2 ФCnH2n ФCO ФH2 ФCO2 ФO2 ФN2
5~15 ≤ 0.5 15~25 40~60 ≤ 0.5 ≤ 0.5 margin
4. The carbon potential of the well furnace gas during the strong infiltration stage can be 0.2% to 0.4% higher than the required surface carbon mass fraction.

Diffusion stage:
1. The infiltration rate during the strong infiltration stage can be estimated at 0.15-0.25mm/h, with a lower limit for low carbon steel and an upper limit for chromium molybdenum steel. When the carburizing layer in Shenzhen Special Economic Zone meets the technical requirements, an external test rod is produced. Based on the depth of the external test rod layer and the mass fraction of surface carbon, it is determined whether the diffusion stage can be entered and the amount of infiltration agent drops during diffusion. For workpieces that do not require diffusion, cooling can be started.
2. During diffusion, the amount of carburizing gas decreases and the amount of protective gas increases. The diffusion time is generally 1/3 to 1/4 of the strong infiltration time, and for carbon steel it is about 1/4 to 1/5, but the specific situation needs to be analyzed.
3. The furnace pressure during the diffusion period is generally controlled at 50-100Pa.
4. The carbon potential of the furnace gas is slightly higher than the lower limit of the surface carbon concentration (mass fraction) specified in the technical requirements.