Screw made of low-alloy carbon steel and method for producing such a screw

Abstract

The invention relates to a screw having a head, an adjoining retaining section and a functional tip for use as a self-tapping screw. The functional tip is of greater hardness than the retaining section. The entire screw is made of hardened low-alloy carbon steel. The special feature of this screw is that its functional tip has a higher carbon and/or nitrogen content than its retaining section

1 . A screw having a head, an adjoining retaining section and a functional tip which is of greater hardness than the retaining section and is made of hardened, low-alloy carbon steel, wherein the functional tip has a higher carbon and/or nitrogen content than the retaining section. 
     
     
         2 . The screw of  claim 1 , wherein the functional tip is further enriched with carbon and/or nitrogen content. 
     
     
         3 . The screw of  claim 1 , wherein additional hardening is achieved above the austenitizing temperature whereby the functional tip has a higher carbon content. 
     
     
         4 . A screw having a head, and an adjoining retaining section and a functional tip, said functional tip being enriched by penetration with carbon and/or nitrogen, to provide the functional tip with a greater hardness than the retaining section, said functional tip comprising a hardened, martensitic structure with a higher carbon content than the retaining section. 
     
     
         5 . The screw of  claim 4 , wherein the functional tip possesses additional hardness due to heating above the austenitizing temperature.