Control of delubrication process for PM components based on prealloyed steel powders
Paper in proceedings, 2012
Reliable in-situ monitoring system for the on-line control of the processing parameters during delubrication of PM steel compacts is presented. The monitoring system is build utilizing sensors (dew-point, CO2 and O2) commonly used in industry. Delubrication of PM steel compacts, based on Cr-alloyed steel powder, was monitored in a number of process gases (inert, reducing and oxygen containing atmospheres) of the different purity (wet and dry gases). Effects of temperature, holding time, heating rate, flow rate and component density were studied. Optimum conditions for efficient delubrication with minimum effect on PM compact properties at lowest processing cost were established. Based on the specimens analysis and gas monitoring profiles in the case of ethylenbisstearamide-based lubricants it is recommended to perform delubrication with low heating rate at temperature around 450°C in nitrogen atmosphere in order to facilitate efficient delubrication and avoid surface oxide during sintering. Rather low flow rate is needed – enough to provide even weak dynamic gas conditions around every component surface.
processing atmosphere control