Rolling procedures for alligator defect elimination

A method of reducing the thickness of a slab of metal in a rolling mill without causing alligatoring in the end of the slab entering the mill, alligatoring being the result of certain combinations of entry thickness and reduction of thickness, the reduction process requiring multiple reductions in thickness of the slab during respective multiple passes of the slab through the mill, the method comprising the steps of:

• determining before each pass of a slab a combination of entry thickness and thickness reduction therefor that is not subject to alligatoring,
• providing the slab with an end portion that has such a combination, the combination being effected by tapering the end portion before each pass,
• leaving the remaining portion of the slab untapered,
• directing each tapered portion into the mill for each reduction in thickness,
• reducing the thickness of each slab in a manner such that the tapered portion passes though the mill before a combination of entry and reduction thickness occurs that can cause alligatoring,
• reducing in thickness the remaining untapered portion of the slab with each pass, and
• completing each pass without the occurrence of alligatoring and until the combination of entry and reduction thickness is not subject to alligatoring, at which time the tapering of the slab end for each pass becomes unnecessary.