Fatigue and mechanical characteristics of nano-structured tool steel by ultrasonic cold forging technology

Ultrasonic cold forging technology (UCFr) utilizing ultrasonic vibration energy is a method to induce severe plastic deformation to a material surface, therefore, the structure of the material surface becomes a nano-crystal structure from the surface to a certain depth. It improves the mechanical properties; hardness, compressive residual stress, wear and fatigue characteristics. Applying UCFr to a rolling process in the steel industry is introduced in this study. First, the UCFr specimens of a tool steel (SKD-61/equivalent H13) are prepared and tested to verify the effects of the UCFr in a variety of mechanical properties, the UCFr is applied to the trimming knives in a cold rolling process. It has been determined that UCFT improves the mechanical properties effectively and becomes a practical method to improve productivity and reliability by about two times compared with the conventionally treated tooling in the trimming process in a cold rolling line. (c) 2006 Elsevier B.V. All rights reserved.