MANGANESE GAS-PHASE ALLOYING OF SINTERED STEELS ANALYSED BY DILATOMETRY: EFFECT OF CARBON, BASE POWDERS AND MANGANESE CARRIER

摘要

Dilatometer tests of mixed Fe-Mn-(C) and hybrid Fe-Mo-Mn-(C) and Fe-Cr-Mo-V-Mn steels at 1150 deg C in H_2/N_2 atmosphere with a dew point of-30 deg C were performed. The effect of manganese and carbon content and manganese carrier on the manganese gas-phase alloying of the tested materials was demonstrated by swelling and shrinkage in dilatometer graphs. The measurable start of the swelling of the specimens caused by manganese sublimation was determined at about 600 deg C. The specimens attained the maximum swelling after aborting the preheating period; higher manganese and carbon content resulted in higher swelling. The various effects of sponge and atomized iron powder and of manganese carrier grades were recorded. Shrinkage of the Mn steel specimens during isothermal sintering, caused by demanganisation expressed in manganese loss and by enhancing effect of manganese for sintering, was recorded. The final dimensional changes of Mn steel samples do not characterize the individual manganese steels because of lower final manganese content due to demanganisation.