Patent ID: 6881934

Claim:
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, the process comprising the steps of: 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 comprising an electrical conductor through the spectacle-shaped bore from one end to the other, the electrical conductor being smaller than but having approximately the same shape as the inner contour of the spectacle-shape bore and being configured such that less energy for heating the inner surface of the spectacle-shaped bore is delivered in the vicinity of the narrowed regions of the spectacle-shaped bore by the longitudinal sections on the periphery of the electrical conductor than in regions on the inner contour remote from the narrowed regions.