INFLUENCE OF PROCESS PARAMETERS ON DELUBRICATION OF PM STEELS

Artikel i vetenskaplig tidskrift, 2011

A systematic study of the effect of various process parameters on lubricant removal in the processing of chromium prealloyed PM steels has been conducted. Improper delubrication affects the densification process and can also lead to blistering, sooting and deposition of decomposition products inside the furnace and on the PM compacts. Current work is focused on defining optimum conditions for efficient delubrication with minimum effect on PM compact properties at lowest processing cost. Effect of temperature, holding time, heating rate, process gas composition (inert, reducing and oxygen containing atmospheres), purity (wet and dry gases) and flow rate was evaluated based on in-situ continuous monitoring of the dew-point, carbon dioxide and oxygen content using industrial sensors. For ethylenebissteramide based lubricants, delubrication at temperature around 450°C with a low heating rate in an inert processing atmosphere with rather low flow rates (enough to provide weak dynamic gas conditions) is recommended.