1. The inspection methods and contents are basically tested in accordance with the provisions of BG11354-89 "Determination of nitriding layer depth and metallographic structure inspection of Steel parts" and ZBJ17001-88 "Gear nitriding, nitrogen carburizing process and quality control"
2. Generally, HV1~5 is used to detect the surface hardness, and the hardened layer depth (DN) is measured from the surface to about 3 times the depth of the penetration layer, and the hardness value can be used at 30HV higher than the matrix for 45 steel. When metallography is used, the sample is tempered at 300ºC for 1h, γ 'phase (Fe4N) is precipitated from the alpha phase, and the post-infiltration depth can be tested
3. Nitrocarburizing parts do not carry out brittleness test, when the hardness is higher than the upper limit of the pattern 300HV, only check brittleness, but it must be porous test, 1 to 3 grades qualified.
Furnace loading, exhaust, heating:
1. After the well furnace reaches the temperature, the heat preservation is 0.5~1h, so that the temperature is uniform, the parts are loaded, and the gap between the hanging parts should be more than 10mm to ensure that the gas is smooth
2. Parts should be placed in the effective heating area of the furnace tank, the upper end should not exceed the exhaust pipe, and the lower end should be kept at a distance from the intake pipe. The exhaust time after loading the furnace is about 20 to 60 minutes
3. The sample should be placed in three different positions: top, middle and bottom
4. After loading the furnace, the infiltration agent exhaust (ethanol drops) should be sent immediately. When the furnace temperature reaches the specified temperature, the exhaust gas should be ignited at the outlet. If the flame does not point, the amount of infiltration agent drops should be increased or the pipe pile plugs should be cleaned in time
5. The new furnace and new fixture should be pre-nitriding treatment for 3~5h
Insulation stage:
1. Check whether the ammonia decomposition rate and flow rate are normal at any time, when the furnace temperature meets the requirements and the ammonia decomposition rate is unstable, the ammonia flow rate can be adjusted, the flow rate increases, the decomposition rate decreases, the flow rate decreases, the decomposition rate increases
2. Some nitrification tanks in the long-term use of ammonia decomposition rate increased phenomenon, in order to make the ammonia decomposition rate stable, it is necessary to stop the furnace for 800~960ºC 2~4h denitrification treatment
Pit furnace cooling:
Parts with high fatigue strength requirements are oil-cooled, and parts with silver-gray surfaces can be cooled to 200ºC under the protection of ammonia or cracking gas before opening the tank to take the workpiece