Patent ID: 9340848
Filing Date: 2016-05-17
CPC Classification: C21D,C23C,F16B

Claim Text:
1. A method for producing a screw having a head, an adjoining retaining section and a functional tip, said functional tip having a greater hardness than the retaining section and is made of a hardened, low-alloy carbon steel, which comprises: providing an insulating layer, which functions as a diffusion barrier and extends over the entire head and retaining section of the screw, heating the screw to a temperature above the austenitzing temperature, exposing the screw to a carbon and/or nitrogen-enriched atmosphere, whereby the screw undergoes a carbon or nitrogen enrichment step that is restricted to its functional tip, hardening the screw by quenching and annealing the screw, and exposing the functional tip to a heat treatment following the annealing step in order to increase its hardness whereby the functional tip, due to the presence of the insulating layer, has a higher carbon and/or nitrogen content than that of the retaining section of the screw.