Introduction

ROLL COMPACTING, or powder rolling, refers to the continuous compaction of metal powders by a rolling mill. In this process, metal powders are fed from a hopper to a set of compacting rolls that produce a continuous green (unsintered) strip or sheet. These materials undergo further processing by sintering (heating) and rerolling to produce an end product with the desired material properties. Material can be produced fully dense or with a desired porosity and pore size.

Ideal powder characteristics for roll compaction are comparable to those desired in powders for die compaction; flowability is important to ensure consistency in the final product; softness and irregularity of powder particle shape promote green strength; and particle size and size distribution influence green density. Metal powders suitable for roll compacting include elemental powders, blends of elemental powders or elemental and alloy powders that are homogenized during sintering, blends that contain additives that are nonreactive and that cannot be produced by standard melting and casting processes, and prealloyed atomized powders.

Atomization has the capability to produce powder particles that are individually uniform in composition and unique in internal structure. Strip produced by roll compacting of powders subsequently produces materials that are clean and completely uniform throughout the coil, with a fine grain size.

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