Effect of Sintering Parameters on the Microstructure and Mechanical Properties of Fe-2.2Mn-1.5Cr- 0.2Mo-0.3C Steel

摘要

In an attempt to study the sinterability of potential high-strength ferrous alloy, compacts of Fe-2.2Mn-1.5Cr-0.2Mo-0.3C were prepared based on water atomised pre-alloyed iron powder Hoeganaes Astaloy CrL (Fe-l.5Cr-0.2Mo), To this was admixed low-carbon ferro-manganese of weight % composition 77Mn-1.3C-0.2O-balance Fe and CU-F graphite. The samples were sintered in the temperature 1120 and 1250 ℃ in laboratory tube furnaces in nitrogen or 95% nitrogen 5% hydrogen atmospheres with dew points better than -70 ℃ and cooled with cooling rate 10 Kmin~(-1). Generally resultant microstructures were homogeneous, consisted of bainite and martensite and were characterised by the absence of oxide networks. Mechanical properties were measured in the as-sintered condition. This alloy transformed to a bainite/martensite structure with good combination of strength and ductility. Sintered densities were in the range of 6.8-7.0 g/cm~3. Mean fracture strengths of the specimens were 730 MPa in tension and 1170 MPa in bending. The fracture data were analysed using Weibull statistics. This method is often used when evaluating the mechanical properties of "flaw-sensitive" materials, primarily sintered materials. By using the Weibull probabilistic relations the resulting variability in the data can be quantified. Weibull module, m, were generally in the range 8-13 for tensile strength and 13-15 for transverse rupture strength.