Wear and fatigue characteristics of new stamping die material for ultra-high-strength steel sheet

High-strength steel sheets, which are considerably cheaper than aluminum alloy sheets, are useful in reducing the weight of automobiles. The superior mechanical properties of these steel sheets, however, make stamping operations more difficult by reducing formability and tool life. An ultra-high-strength steel sheet has an even higher surface hardness and yield strength than the highstrength sheets, that further increase the forming force, die wear/galling and springback, resulting in an even greater reduction in die life during stamping. Given the clear need for a more durable die material, in this study, we evaluate the wear and fatigue characteristics of a new die material that has been developed for stamping ultra-high-strength steel. Through pin-on-disk wear testing and rotating bending fatigue testing, it is found that both the wear and fatigue characteristics of the die are improved by using this new material. And die wear is evaluated by FE analysis and experiment for ultra-high-strength steel stamping.