Influence of fines and particle size distribution on density and performance of sintered steel components
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Experiments were performed with five different fine powders and ASC 100.29 iron powder to investigate the effect of small sized particles on compaction and sintering characteristics. The results show that fines additives reduce the green density by compaction and increase the sintering densification. The former is a consequence of larger inter-particle friction and earlier hardening of particles under low load. The latter is caused by increased total contact area during sintering. Particle with smallest size exhibits a very fast sintering due to its high specific surface area and so induced fast surface diffusion rate. Spring back value gets enlarged by smaller particle size, shape irregularity and impurities. A homogeneous stress condition reduces the spring back significantly. High speed shear mixer has proved to be effective for deagglomertion and beneficial to improve the mechanical properties. The profits mainly originate from the high shear stress along the vessel walls and the continuous powder flow that promises a very good packing structure. In presence of fines, it is recommended to conduct a sufficient mixing to fit the small particles into the interstices between large particles before compaction. There exists an optimum range of particle size distribution for best process behavior. In this work several particle size distributions with a same median particle size are designed, the second narrowest one presents the best performance.
Place, publisher, year, edition, pages
Fine particle size, irregular particle shape, inclusions, agglomeration, high speed shear mixer, particle size distribution
IdentifiersURN: urn:nbn:se:kth:diva-103264OAI: oai:DiVA.org:kth-103264DiVA: diva2:559352
Frykholm, Robert, PhD
Eliasson, Anders, PhD