Before the hot stamping process, the blanks for the components are cut from coiled material—an aluminum-silicon (AlSi)-coated boron steel with initial yield strength of 500MPa. In the first part of ...
Before the hot stamping process, the blanks for the components are cut from coiled material—an aluminum-silicon (AlSi)-coated boron steel with initial yield strength of 500MPa. In the first part of the heating process, the blanks then are heated to approximately 1200°F to allow the AlSi coating to bond to the boron steel base. In the second part, they are further heated to approximately 1740°F. The bright-red glowing parts are placed in the press dies, followed by forming and quenching within the die. Within a short period of time, the parts are cooled to about 400°F using rapid controlling. The result is an austenitic grain structure, which gives the parts a yield strength of around 1500MPa. While the process is often referred to as hot forming, the description of press hardening is actually more precise, as the entire process is a heat treatment. The forming alone could be done without the parts being heated.
With the parts formed, they need to be trimmed into their final shape and openings or holes need to be added. The high strength of the parts requires a different method than commonly used on other stamped sheet-metal parts. Trimming die material is not hard enough to allow its use for trimming or cutting hot-stamped parts. Even if this process could be used, it would still pose risks like deformation of the edges and micro-cracking due to the high forces involved. In addition, the cost of those tools would be too high to be economically viable, as they would require repair or replacement within several hundred hits. The downtime for the tooling changeover and its associated cost further reduce the usefulness of this process.
The solid-state laser—with a wavelength of approximately 1μm—has been proven to be the best solution. When used as a cutting tool, the laser's high-energy beam melts the material and a high-pressure processing gas blows the molten material away from the cut.