Effect of manganese source powders on microstructure and mechanical properties of Fe-Mn-C sintered steel

Using the electrolytic manganese powders and Fe-76%Mn powders (mass fraction) as the raw materials, the antioxidative nitrogen-manganese source powders (Mn-3%N, Mn-5%N, and FeMn-3%N, mass fraction) were prepared in the tube furnace with 70%N₂ + 30%H₂ gas (volume fraction) at 600 ℃, the effects of the manganese mass fraction and the type of manganese source powders on the microstructure and mechanical properties of the Fe-Mn-C sintered steels were investigated. In the results, the mechanical properties of the Fe-Mn-C sintered steels prepared by the nitrogen-manganese source powders are obviously better than those prepared by the electrolytic manganese powders. With the increase of the nitrogen mass fraction in the manganese source powders, the sintering expansion rate of the sintered steels decreases, and the strengthening of the Fe-Mn-C alloy is increased. The tensile strength of the Fe-2Mn-0.5C sintered steels prepared by Mn-5%N powders is 576 MPa, and the fracture elongation is 3.8%, which is improved by 29% and 123%, respectively, compared with those prepared by the electrolytic manganese powders. The number of pores in the sintered steels prepared by the nitrogen-manganese source powders decreases, the pearlite increases, and the lamellar spacing decreases.