Abstract
The prescence of sulphur in carbon edges on cold-rolled annealed steel sheet from the Domnarvets Jernverk plant, and the apparent insensitivity of the carbon-edge frequency to changes in the composition of the DX-type protective atmosphere are taken as starting points for the identification of a new mechanism for the formation of carbon edges on cold-rolled steel strip during annealing. This mechanism involves the decomposition and subsequent reactions of iron sulphates with oil shown to be present on the strip at the outset of the annealing cycle,. it accounts for the carbonaceous deposit andfor the clean, bright region at the edge of the strip. Experimental evidence for the reaction mechanism as well as for the transport of iron sulphates through the tandem mill is presented. The literature on carbon edges and several possible improvements in the production line, including those which, at the Domnarvets Jernverk plant, have turned out to be extremely successful, are discussed in the light of the present findings.
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