Advanced High Strength Steels for Automobile Body Structures

Abstract:

There has been a big demand for increased vehicle safety and weight reduction of auto-bodies. An extensive use of high strength steels is one of the ways to answer the requirement. Since the crashworthiness is improved by applications of higher strength steels to crashworthiness conscious structural components, various types of advanced high strength steels have been developed. The crash energy during frontal collisions is absorbed by the buckling and bending deformations of thin wall tube structures of the crushable zone of auto-bodies. In the case of side collision, on the other hand, a limited length of crushable zone requires the components to minimize the deformation during the collision. The lower the strength during press forming, the better the press formability is expected. However, the higher the strength at a collision event, the better the crashworthiness can be obtained. It can, therefore, be concluded that steels with higher strain rate sensitivities are desired. Combinations of soft ferrite phase and other hard phases were found to improve the strain rate sensitivity of flow stresses. Bake hardening is also one of the ways to improve the strain rate sensitivity of flow stresses.

• Periodical: Materials Science Forum (Volumes 539-543)
• Pages: 4386-4390
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.539-543.4386
• Online since: March 2007
• Authors: M. Takahashi, A. Uenishi, H. Yoshida, H. Kuriyama
• Keywords: Bake Hardenability, Crashworthiness, High Speed Deformation, High Strength Steel (HSS), TRIP

References

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[20] [40] [60] [80] 100 120 0 200 400 600 800 Static TS (MPa) ∆σ∆σ∆σ∆σs{5-10%, WH+BH} and ∆σ∆σ∆σ∆σd{5-10%, WH+BH} (MPa) ∆σ∆σ∆σ∆σs{5-10%} ∆σ∆σ∆σ∆σd{5-10%} TRIP & DP Conventional steels 5% pre-strain Fig. 11 Increases in static and dynamic flow stresses due to 5% of Pre-deformation and baking.

DOI: 10.1201/9780203021262-58

[8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] 20 30 40 50 Total elongation (%) Calculated absorbed energy (kJ) 348MPa Mild steel 487MPa Solution hardened TS/636MPa HSLA 618MPa-DP 644MPa-TRIP.

[8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] 20 30 40 50 Total elongation (%) Calculated absorbed energy (kJ) 348MPa Mild steel 487MPa Solution hardened TS/636MPa HSLA 618MPa-DP 644MPa-TRIP Fig. 12 Relation between total elongation and calculated absorbed energy for axial crash of a square tube.