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.
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Figure 1. The tensile strength-elongation graph of HF steel.
The following table summarizes the current HF steel production grades and corresponding automotive applications:
| HF 340/480 |
As-received room temperature |
| HF 1050/1500 |
Heat treated after forming, A-pillar, B-pillar, cross beam |
| HF 1200/1900 |
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.
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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).