Some problems of the sintering and densification of rolled powder stock

Summary

• 1. The sintering of strips in continuous production cycle systems is only justified in the case of thoroughly reduced powders, when heat treatment has the single object of raising the mechanical properties, while the refining, oxide reduction, and other processes are regarded as being of secondary importance.

• 2. It was demonstrated experimentally that, for strips of different initial densities, there exists a strictly defined optimum degree of relative reduction, beyond which the intensity of densification decreases. At equal relative reduction, densification is more pronounced during rolling between rolls of large diameter.

• 3. The relative decrease of the pore diameter during densification lags slightly behind the relative reduction of strips. Thus, depending on the mean pore diameter in the starting specimens, different over-all reductions maybe required to secure a nonporous strip microstructure.

• 4. On the basis of phenomenological presentations, the strengthening of rolled porous material during densification within the strain limits investigated may be determined from Frantsevich's formula as modified for porous bodies, allowing for the change in density during deformation by means of Bal'shin's formula.