How to Properly Operate a Nitriding Furnace?
Nitriding is a thermochemical heat treatment process in which nitrogen atoms are diffused into the surface layer of a workpiece at a specific temperature within a specific medium. Components treated via nitriding exhibit excellent resistance to wear, fatigue, corrosion, high temperatures.
During the process, ammonia gas is introduced into a vacuum-sealed stainless steel retort housed within the nitriding furnace. The furnace is then heated to 520°C held at this temperature for a specific duration—ranging 3 to 90 hours, depending on the workpiece material the required nitriding depth. This process creates a nitrogen-enriched hardened layer on the workpiece surface, resulting in high hardness, superior wear resistance, a high fatigue limit, excellent durability.
Operating Procedures:
1.  Prior to nitriding, the molds workpieces must have already undergone normalizing quenching tempering treatments.
2.  Thoroughly clean the surface of the workpiece using gasoline alcohol; the surface must be free of rust spots, oil stains, dirt.
3.  Once the workpiece is loaded into the furnace, symmetrically tighten the clamping bolts on the furnace lid to ensure a secure seal.
4.  Connect the cooling water supply to the inlet ports on both the furnace retort the furnace lid to establish a circulating water-cooling system. For the piping on the furnace lid, the lower port serves as the water inlet the upper port as the outlet; the furnace retort requires its own independent water inlet outlet. Alternatively, all water pipes on the furnace lid may be connected in series—following the principle of "low-in, high-out"—so that the entire lid system utilizes a single water inlet a single water outlet.
5.  Before raising the furnace temperature, introduce nitrogen gas to purge the system. During this purging phase, the gas flow rate should be set to more than double the rate used during the actual nitriding process. After purging for 10 minutes, set the temperature controller to 150°C switch the automatic heating toggle to the "ON" position. Continue purging while heating to 150°C, maintaining this temperature for 2 hours. Next, set the temperature controller to 530°C reduce the ammonia gas flow rate to maintain a positive pressure within the furnace, ensuring a slight upward flow of gas at the exhaust port. Once the furnace temperature reaches 530°C, perform constant-temperature, constant-flow nitriding for 3 to 20 hours. Then, slightly increase the ammonia gas pressure to maintain a moderate pressure at the exhaust, continue nitriding for another 4 to 70 hours. Subsequently, reduce the ammonia gas pressure again perform a denitriding step for 1 to 2 hours. Finally, cut off the power supply to stop heating, continue supplying a small amount of ammonia gas to maintain a positive pressure within the furnace; the ammonia supply may be stopped the workpiece removed the furnace only after the furnace temperature has dropped below 150°C.