Abstract

Disclosed is a new internally heated calendering roll capable of finishing paper satisfactorily at the temperatures, heat loads and pressures required for substrata thermal molding. The roll is internally heated and has a circumferential wall at least 4 inches thick. It includes means to provide heat into the interior of the circumferential wall to be conducted through the wall to the outer surface for heating the paper web being calendered by the roll. The roll is constructed of a first material with a thin circumferential surface layer of a second, cermet or ceramic containing material. The surface layer material has a hardness of at least 530 Vickers and a thickness of between .003 inch and .030 inches. It is capable of being polished to a roughness of less than 6 micro inches Ra. The roll has uniformly spaced conduits for passing heated fluid located no more than 2 inches from the outer edge of the conduits to the circumferential surface. The roll is capable of conducting at least 8,500 BTU/Sq. Ft./Hr. heat through the roll without creating tensile hoop stress in excess of 1/2 of the yield strength of the first material.

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