科研之友
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摘要
This paper presents a systematic approach to study the effect of manufacturing variables on the mechanical properties of sintered Fe-3Mb-0.8C steel. Tensile and 3 point bending tests have been performed on specimens made of three different iron powders with variations of sintering conditions. Ferro-manganese and graphite powders were admixed to Hoganas sponge, NC100 24. and water atomised, ABC 100.30 and ASC 100.29, iron powders - to produce three variants of Fe-3Mn-0.8C mixtures. The powders were pressed into specimens at 660 MPa, sintered in semi-closed containers for 1 h in dry nitrogen or hydrogen at 1120 or 1250 degrees C, and cooled at 64 degrees C/min. Green and sintered densities were expectedly highest for ABC 100.30 powder at similar to 7.1 g/cm(3). They were >0.2 g/cm(3) higher than for the sponge powder based specimens. Similarly, Young's modulus in the former material attained similar to 130 GPa, being similar to 117 GPa in the latter. Yield siren-the were higher for the atomised powder based alloys and for 1250 degrees C and nitrogen sintering. Tensile and bend strengths were somewhat higher for specimens sintered in nitrogen and, generally by similar to 10%, higher for specimens pressed from sponge iron powder, resulting in similar to 730 MPa tensile strength for sintering? in nitrogen at 1250 degrees C. The strongest ABC 100.30 powder based specimens attained tensile strength similar to 650 MPa. The higher plasticity of the sponge powder based steel and hence strengths arc associated with the increased surface area available to the Mn vapour for alloying. This ensures also cleaner. snore cohesive prior powder particle boundaries the favoured microcracking paths. The study of fracture Stress is based on a statistical Strength theory suggested by Weibull. It enables fracture probability to he calculated as a function of applied stress. The paper shows that Weibull distribution is mole applicable to the strength evaluation and failure statistics of PM steels half the more commonly used normal distribution.
- 出版日期2008
