3-D Laser Cutting of Hot-Stamped Steels

Driven by the automotive industry’s need to improve safety, reduce vehicle weight and increase fuel economy, the steel industry has developed numerous advanced-high-strength steels and hot-formable steels. Hot stamping with die quenching of boron steels appeared at the end of the 1990s, and since then, the process—also called press hardening or hot forming—has become popular for forming complex, high-strength automotive components. With so many advantages and very few drawbacks, it is easy to predict that the use of hot-formed steels in the automotive industry, and possibly in other industries, will dramatically increase in the coming years.

This new type of metalforming requires a new generation of 3D processing equipment for trimming and piercing. While traditional mechanical equipment used to trim and pierce formed parts results in extremely high tool wear, laser-beam cutting, according to Antonio Rotunno, director of technical services for Prima North America, Chicopee, MA, offers manufacturers a to easily and accurately adjust trim lines and feature size or location. And, the thermal reaction required for laser cutting is unaffected by steel strength.

In 1995, Rotunno says, hot-formed parts were laser-cut using oxygen as the assist gas. Cutting speeds were around 100 in./min. Today, lasers with higher beam quality and power to 5000 W allow cutting with an inert assist gas such as nitrogen, with speeds in excess of 780 in./min. The cut edges are free from oxide and therefore are weld- and paint-ready with no secondary operations required.

Prima has deployed 3-D laser-cutting systems in hot-stamping applications throughout Europe and North America, including automotive supplier SSAB HardTech, a manufacturer of safety components (acquired by Gestamp in 2005).