Low Density Steel having Good Drawability

摘要

A cold-rolled and annealed ferritic steel sheet is provided. The steel has a composition comprising, expressed by weight:
0.001≦C≦0.15%;Mn≦1%;Si≦1.5%;7.5%≦AI≦10%;0.020%≦Ti≦0.5%;S≦0.050%; andP≦0.1%.;A balance of the composition includes iron and inevitable impurities resulting from the smelting. The structure includes kappa (κ) precipitates and equiaxed ferrite, an average grain size dα of the equiaxed ferrite is less than 50 microns, and a linear fraction f of intergranular κ precipitates is less than 30%. The linear fraction f is defined by;f=Σ(A)diΣ(A)Li.;Σ(A)di denotes the total length of grain boundaries containing κ precipitates relative to an area (A) and Σ(A)Li denotes the total length of the grain boundaries relative to the area (A). A content of carbon in solid solution is less than 0.005% by weight, and the cold-rolled and annealed ferritic steel sheet has a thickness between 0.6 mm and 1.5 mm. A skin part or structural part for the automotive field is also provided.

主权项

1: A cold-rolled and annealed ferritic steel sheet, the steel has a composition comprising, expressed by weight:
0.001≦C≦0.15%; Mn≦1%; Si≦1.5%; 7.5%≦Al≦10%; 0.020%≦Ti≦0.5%; S≦0.050%; and P≦0.1%; a balance of the composition being iron and inevitable impurities resulting from the smelting; a structure of the steel comprises kappa (κ) precipitates and equiaxed ferrite, an average grain size dα of the equiaxed ferrite is less than 50 microns, and a linear fraction f of intergranular κ precipitates is less than 30%, the linear fraction f being defined byf=Σ(A)diΣ(A)LiΣ(A)di denoting the total length of grain boundaries containing κ precipitates relative to an area (A) and Σ(A)Li denoting the total length of the grain boundaries relative to the area (A);
a content of carbon in solid solution is less than 0.005% by weight, and the cold-rolled and annealed ferritic steel sheet has a thickness from 0.6 mm to 1.5 mm.