Low alloy third generation advanced high strength steel
A high strength steel comprises, during intercritical annealing, about 20-80% volume ferrite and 20-80% austenite, and wherein the Ms temperature calculated for the austenite phase during intercritical anneal ≤100° C. The high strength steel exhibits a tensile elongation of at least 20% and an ultimate tensile strength of at least 880 MPa. The high strength steel may comprise 0.20-0.30 wt % C, 3.0-5.0 wt % Mn, with Al and Si additions such that the optimum intercritical temperature is above 700° C.
1. A high strength steel comprising 0.20-0.3 wt % C, 3.5-4.5 wt % Mn, with the sum of the Al and Si additions of 2.6 to 3.6% such that an optimum intercritical temperature is above 700° C., wherein, during intercritical annealing, the high strength steel includes about 20-80% volume ferrite and 20-80% austenite, and wherein the Ms temperature calculated for the austenite phase during intercritical anneal ≤100° C.
2. The high strength steel of claim 1 , wherein the intercritical annealing occurs in a batch process.
3. The high strength steel of claim 1 , wherein the intercritical annealing occurs in a continuous process.
4. The high strength steel of claim 1 , having a tensile elongation of at least 20% and an ultimate tensile strength of at least 880 MPa.
5. The high strength steel of claim 1 further comprising 0.8-1.3 wt % Al, 1.8-2.3 wt % Si, and the balance of Fe, and impurities.
6. The high strength steel of claim 1 further comprising 0.8-1.3 wt % Al, 1.8-2.3 wt % Si, 0.030-0.050 wt % Nb, and the balance of Fe, and impurities.
7. The high strength steel of claim 1 , wherein after hot rolling, said steel has a tensile strength of at least 1000 MPa, and a total elongation of at least 15%.
8. The high strength steel of claim 1 , wherein after hot rolling, said steel has a tensile strength of at least 1300 MPa, and a total elongation of at least 10%.
9. The high strength steel of claim 1 , wherein after hot rolling and continuous annealing, said steel has a tensile strength of at least 1000 MPa and a total elongation of at least 20%.