Effects of the surface roughness of rolls on the powder rolling process

Abstract

A study was made of the effects of the surface roughness of rolls on the properties (thickness, density, and forward slip) of roll-compacted strip and of the running-in of rolls in contact with the material being rolled. It was established that the surface condition of rolls has a strong influence on the properties of strip. Increasing the height of roll surface irregularities from 2.8 to 7.0μ increases the strip thickness from 0.38 to 0.65 mm in the rolling of a coarse copper powder and from 0.43 to 0.68 mm in the rolling of an iron powder. Further increase in the height of microirregularities produces very little change in strip thickness and density. The study revealed that, during the running-in of the roll surfaces as a result of contact with the material being rolled, the thickness and density of the strip change, and the rolling process thus takes place under non steady-state conditions. The time required for the stabilization of the process depends on the composition of the mixture being rolled and the hardness of the material of the rolls. The findings of laboratory investigations have been confirmed by data yielded by experiments carried out under industrial conditions. As a method of treatment of roll surfaces, the rolling of electrocorundum abrasive cloths of No. 10–20 grain size, to GOST 3647-71 standard, is recommended. As a result of this treatment, rolls acquire a class 5 surface finish.