Abstract
Water-atomized high speed steel powder was pressed into a component with high aspect ratio by repetitive compaction process using electric drive CNC press and the uniformity of green density along the compacting axis was investigated. For the dimensional accuracy the uniform density distribution is very important because of large linear shrinkage ratio of about 10% during vacuum sintering. The CNC compacting press has superior versatility of compaction sequences and makes it possible to minimize the difference of local green density by repetitive compaction which consists of several sets of powder filling and compaction.
The green compact(φ14×45) by repetitive compaction showed fairly uniform density distribution and smaller local density variation compared with green compact by conventional single compaction. The measured profile curves along a side wall of sintered parts were in good agreement with the predicted density distribution and the dimensional variation in radial direction was reduced. Tensile strength was equivalent to that of conventional part and the breakage didn't occur at the joining point. The experimental results shows the possibility of near-net-shape production of P/M high speed steel parts with large height.
