Press hardened steel with extremely high strength and method for production
Press hardened steels exhibit increased strength in the press hardened steel parts without a corresponding decrease in elongation. Substitutional elements are included in the steel composition to increase the strength of martensite through a combination of substitutional solute strengthening and a reduction in softening that results from autotempering. Softening as a result of autotempering is minimized by suppression of the martensite start (Ms) temperature through the alloying. As a result of the increased hardenability in the proposed compositions that results from various additions of manganese, chromium, molybdenum, and niobium, the steel compositions permit a boron-free press hardening steel.
1. A press hardenable steel comprising, by weight percent, 0.22-0.25% carbon, 2.0 to 3.0% manganese, 0.2-0.3% silicon, 0.2 to 6.0% chromium, no more than 0.004% aluminum, and at least one of 0.1 to 0.6% molybdenum, 0.01 to 0.1% niobium, or 0.01 to 0.15% vanadium, the balance comprising iron and incidental impurities, wherein the ultimate tensile strength of such steel is greater than 1800 MPa, and a total elongation of such steel is at least 6%.
2. The press hardenable steel of claim 1 comprising 0.4 to 0.6% molybdenum.
3. The press hardenable steel of claim 1 comprising 2.0 to 6.0% chromium.
4. The press hardenable steel of claim 1 having two outer surfaces, and further comprising an aluminum-based coating or a zinc-based coating applied to at least one outer surface.
5. The press hardenable steel of claim 1 , wherein the press hardenable steel can be fully austenitized at a PMT of less than 850° C.
6. The press hardenable steel of claim 1 comprising 0.4-6.0% chromium.
7. The press hardenable steel of claim 1 , without the intentional addition of titanium.
8. The press hardenable steel of claim 1 , without the intentional addition of antimony.
9. The press hardenable steel of claim 1 , wherein vanadium is 0.01 to 0.1%.
10. The press hardenable steel of claim 1 , without the intentional addition of boron.
11. The press hardenable steel of claim 1 , without the intentional addition of antimony and boron.
12. The press hardenable steel of claim 1 , without the intentional addition of antimony and boron, and where vanadium is 0.01 to 0.1%.
13. The press hardenable steel of claim 1 , wherein chromium is 0.2 to less than 3.0%.