Parameters Controlling the Oxide Reduction during Sintering of Chromium Prealloyed Steel

Abstract

Temperature intervals of oxide reduction processes during sintering of the Fe-3%Cr-0.5%Mo prealloyed powder using continuous monitoring of processing-exhaust gas composition (CO, CO2, and H2O) were identified and interpreted in relation to density (6.5–7.4 g/cm3), sintering temperature (1120 and 1200°C), heating and cooling rates (10 and 50°C/min), carbon addition (0.5/0.6/0.8%), type (10%H2-N2, N2), and purity (5.0 and 6.0) of the sintering atmosphere. The progress in reduction processes was evaluated by oxygen and carbon contents in sintered material and fracture strength values as well. Higher sintering temperature (1200°C) and density <7.0 g/cm3resulted in a relative decrease of oxygen content by more than 80%. The deterioration of microclimate purity of inner microvolumes of compacts shifted the thermodynamic equilibrium towards oxidation. It resulted in a closing of residual oxides inside interparticle necks. The reducing ability of the N2atmosphere can be improved by sintering in a graphite container. High density of 7.4 g/cm3achieved by double pressing indicated a negative effect on reduction processes due to restricted replenishment of the microclimate atmosphere with the processing gas. In terms of strength properties, carbon content should not be higher than ~0.45%.

The Effect of Mn Content on the Structure and Properties of PM Mn Steels

“…Conversely, reduced ductility of Cr and Mn sintered steels has been associated, e.g. by Hryha et al [18] and Hrubovcakova et al [19], with bound-a) b) Fig. 17.…”

Carbon Co-Deposition During Gas Reduction of Water-Atomized Fe-Cr-Mo Powder

“…After atomization, average oxygen content of as-atomized powder was found to be 2.09 wt.%. Pseudo-binary phase diagram of a Fe-3Cr-0.5Mo and H 2 O system showed that three kinds of oxides exist in the high temperature, low H 2 Figure 1 [21]. …”

“…Most iron powder is used in the production of high-strength steel components, which typically rely on alloying elements such as nickel (Ni), copper (Cu) and molybdenum (Mo) for their strength [1][2]. However, the high cost of these traditional alloying elements has created a need for cheap and efficient alternatives in order to reduce overall product costs.…”

“…However, the high cost of these traditional alloying elements has created a need for cheap and efficient alternatives in order to reduce overall product costs. One such alternative is chromium (Cr), which is low in cost, relatively abundant, easy to recycle and offers good resistance to temper softening [1][2][3]. It is also particularly effective in improving sinter-hardenability [4], which is a process of transforming the whole part or some specific region to martensite by controlling the cooling rate during sintering.…”

“…This offers many economic benefits as a onestep manufacturing process for achieving a good combination of strength, toughness and hardness [4]. Yet despite all these benefits associated with Cr, it is not currently being used to its fullest potential because of its very high affinity for oxygen [1][2][3][4][5].…”