Common wire belts will start to fall apart eight weeks after being

operated because ofnitrogenization and carbonization. Taking the traditional 314 metal modular conveyor belt as an example, firstly it willexperience the quenched-tempered heat treatment, which means to operate under870 ℃ and normal conditions in flowing air for 28 hours.Then we switch to N2- 3℃H2 and continue for 2hours. After that, we increase the temperature continuously for 14 hours untilit reaches 1120℃.We maintain this temperature for 8 hours. Finallyit’s time to sinter parts.At this time, there is oxygen in the air and thevapour amounts to 20 pmm.

But belts willstart to fall apart 8 weeks later. This is because the thin chromic oxide layeron the surface of stainless steel is on the state of oxidation in thepreheating zone. It turns to be on the reducing state as soon as being putunder high temperature. But it returns to the oxidation state once being put inthe cooling zone, making belts be oxidated again. Thus materials are seriouslydamaged in this process. Besides, the graphite and lubricant in the parts willresolve and produce CO when stainless steel is put in high temperature,resulting in carburization. As a result, life time of the stainless modular conveyorbelt will be cut as both Crc produced by reaction of CO and Cr in the belt andCrN produced by reaction of Cr and N in the air are hard brittle components.The solution is: to make sure the oxide on the surface not return to theoriginal condition by turning up the dew point temperature to 34℃ (the vapour is 260 ppm). In this way the metal modular conveyor belt canremain on the state of oxidation under high temperature.