Screws having selected heat treatment and hardening
AssigneeIllinois Tool Works Inc.
InventorsMark D. Bauer, William A. Spring, Michael Starozhitsky, S. Riaz U L Hasan
Life of this patent
Estimating the term…
Abstract
A carbon steel screw has one or more portions which have been selectively hardened by selective heat treatment and quenching. In one embodiment, an upper portion of the screw head is selectively hardened to prevent or reduce damage when torque is applied using a driving tool. In another embodiment, the screw tip is selectively hardened for more effective penetration into a substrate. Preferably, the selectively heated portions are selectively quenched to reduce or avoid distortion.
Claims25
A selectively hardened carbon steel screw comprising a screw head, a shank having a first end adjacent the head and a second end, and a screw tip adjacent the second end of the shank;
- the screw head including a top surface, a bottom, a center region, an outer rim and a recess in the center region for receiving a driving tool;
- the screw head having a martensitic metallurgical structure on the top surface in the center region, and a ferritic perlitic metallurgical structure on the bottom.
A selectively hardened carbon steel screw comprising a screw head, a shank having a first end adjacent the head and a second end, and a screw tip adjacent the second end of the shank;
- the screw head including an upper selectively hardened portion and a lower portion which has not been hardened;
- the shank including an upper portion which has not been hardened;
- wherein the screw tip is also selectively hardened.
A selectively hardened carbon steel screw comprising a screw head, a screw shank having a first end adjacent the head and a second end, and a screw tip adjacent the second end of the shank;
- wherein a portion or portions of the screw are selectively hardened by heat treatment to an elevated temperature of at least about 1400.degree. F., followed by quenching, to yield a Rockwell "C" hardness at least about 10 units higher than a remaining portion or portions of the screw not selectively hardened.
Dependencies are inferred from the claim text.