Kenneth J Schnettler

US Patent:

62351311, May 22, 2001

Filed:

Jul 9, 1999

Appl. No.:

9/349984

Inventors:

Scott C. Keihle - Monticello IN
Ronald D. Orr - Logansport IN
Daniel R. Sebastian - Peru IN
Kenneth J. Schnettler - Peru IN

Assignee:

Mathew Warren Industries, Inc. - Logansport IN

International Classification:

C21D 902
C22C 3818

US Classification:

148580

Abstract:

Steel springs are cold coiled, then hardened by electrical resistance heating, and then quenched. The invention may be used to produce hardened springs with uniform mechanical and physical characteristics, fine grain microstructures, and high fatigue resistance. The heat hardening process may be individually controlled for each spring, and it may be performed in a very short period of time. The process time may be so short as to preclude decarburization, making it unnecessary to use a controlled endothermic atmosphere. The free lengths of the finished springs may be controlled by applying axial forces during heat hardening. According to one aspect of the invention, the coiled central section of the spring is made harder than its ends. The equipment for practicing the invention may have a compact, uncomplicated construction.