For optimized geometries of intricately shaped components that are free from springback problems, the combination of press-hardening applications and hardenable steels is a potential substitute. Since the 1990s, boron-based hot-forming steels with a boron content of 0.001% to 0.005% have been employed for body-in-white construction. The process involves maintaining a minimum temperature of 850°C during the forming process (austenitization) and subsequent cooling at a rate of more than 50°C/s to obtain the mechanical properties of interest.
Types of Hot-Forming Applications
Direct Hot-Forming and Indirect Hot-Forming are the two kinds of hot-forming or press-hardening applications available. In the case of Direct Hot-Forming, the blank is completely deformed in the high temperature austenitic range and subsequently quenched. During Indirect Hot-Forming, the blank is preformed at room temperature to a high percentage of the finishing component shape and subsequently treated by high temperature forming and quenching. The resulting HF steel has a final microstructure analogous to martensite. The tensile strength- elongation graph for HF steels is shown in Figure 1.
Figure 1. The tensile strength-elongation graph of HF steel.
The following table summarizes the current HF steel production grades and corresponding automotive applications:
||As-received room temperature
||Heat treated after forming, A-pillar, B-pillar, cross beam
||Heat treated after forming
Download the Advanced High-Strength Steels Applications Guidelines free here, to learn more about the metallurgy, forming and joining of these new steels.
This information has been sourced, reviewed and adapted from materials provided by WorldAutoSteel (World Auto Steel).
For more information on this source, please visit WorldAutoSteel (World Auto Steel).