Abstract: A process for producing a barrel for a twin-screw extruder with intermeshing screws from a steel block, wherein the barrel has a wear resistant inner surface, includes producing two partially intersecting bores passing completely through the steel block, the two intersecting bores forming a spectacle-shaped bore having narrowed regions where the two intersecting bores intersect, and hardening an inner surface of the spectacle-shaped bore with essentially constant depth of penetration by passing an inductor through the spectacle-shaped bore from one end to the other, the inductor is smaller than but having approximately the same shape as the inner contour of the spectacle-shaped bore and is configured such that less energy for heating the inner surface of the spectacle-shaped bore is delivered in the vicinity of the two narrowed regions of the spectacle-shaped bore by the longitudinal sections on the periphery of the inductor than in regions on the inner contour remote from the narrowed regions.

Abstract: The invention relates to a method and a device for inductive hardening of the interior surface of a spectacle shaped bore (2) in a cylinder housing (1) made of steel for a double screw extruder. According to the invention, the outer form of the electric inductor (3) corresponds approximately to the reduced interior contour of the spectacle shaped bore (2). Said inductor (3) is configured in such a manner that in the vicinity of the narrowing elements of the spectacle shaped bore (2) less energy is required for heating the inner surface in relation to the longitudinal section on the periphery of the inductor (3) than that is required for the areas of the inner surface which are remote from the narrowing elements (4a, 4b).