High-strength multi-phase steel and method for producing strip from such multi-phase steel

Abstract

The invention relates to a high-strength multi-phase steel with a minimum tensile strength of 980 MPa, which contains (by weight percentage): C≥0.075~≤0.115; Si≥0.400~≤0.500; Mn≥1.900~≤2.350; Cr≥0.250 ~≤0.400; Al≥0.010~≤0.060; N≥0.0020~≤0.0120; P≤0.020; S≤0.0020; Ti≥0.005~≤0.060; Nb≥0.005~≤0.060; V≥0.005~≤0.020; ~≤0.0010; Mo≥0.200~≤0.300; Ca≥0.0010~≤0.0060; Cu≤0.050; Ni≤0.050; Sn≤0.040; Including impurities, wherein the total content of Mn-Si+Cr is ≥ 1.750% by weight to ≤ 2.250% with respect to the widest possible processing window during annealing, especially continuous annealing, of cold-rolled strip composed of this steel (weight).

Description

technical field [0001] The invention relates to a method for producing a steel strip from a multiphase steel having a minimum tensile strength of 980 MPa in the unquenched state according to the preamble of claim 1 . [0002] The invention also relates to a steel strip produced by the method according to claim 9 . [0003] The invention relates in particular to steels for the production of components having a tensile strength in the unquenched state of at least in the region of 980 MPa, which components have improved formability, for example with regard to hole expansion, and have improved bonding Properties such as soldering characteristics. Background technique [0004] The fiercely competitive automotive market is constantly forcing manufacturers to find solutions to reduce fleet fuel consumption and CO2-emissions while maintaining maximum comfort and passenger protection. Here, on the one hand, the weight reduction of all vehicle components plays a key role, but on the...

AI Technical Summary

Problems solved by technology

[0085] In summary, the problem with the known steel grades is that in terms of the minimum rolling rate required in cold rolling for complete recrystallization after continuous annealing, in a given roughing strip thickness after hot rolling in order to produce the main hot strip thickness In the case of steel thicknesses, there is no longer manufacturing flexibility in terms of the different cold-rolled strip thicknesses to be achieved (see figure 1 , so process steps 6, 8 and 9 are required)

In particular, the process window is too small to produce different cold strip thicknesses with similar material properties on the resulting cold strip while the main hot strip thickness is constant

Additionally, setting a constant pre-strip thickness in order to produce a defined constant main hot strip thickness additionally limits manufacturing flexibility

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