| 摘要 |
A bolt-like fastening element (30), which is preferably in the form of a drilling screw shaped by pressing and/or rolling, having a head portion (LK), which has a holding region (LH) and has a starting hardness, and also having an initial portion (LA), which adjoins the head portion (LK) by way of a transition region (LÜ) and is additionally inductively hardened. The fastening element (30) is produced by cold forming from a blank made of a carbon steel having a starting tensile strength of at least 800 N/mm2. The induction hardening of the fastening element extends only to the initial portion thereof, i.e. in the case of a drilling screw to the drill bit (24) and the first turns of the thread (36). After the induction hardening, the drilling screw substantially has the starting tensile strength and is ductile in the head portion (LK). In the initial portion (LA) as far as into the central axis (33), the drilling screw is fully hardened to a hardness which is at least twice the magnitude of the starting hardness in the head portion (LK). The notched-impact energy in the head portion (LK) of the bolt-like fastening element is at least three times that in the initial portion (LA). |
