Boron Containing Low Carbon Deep Drawing Continuous Annealed Steel Sheet with Improved Plastic Anisotropy

Abstract

In current market scenario, cold-rolled steel sheets need high quality requirements to suit the continuous automated forming process for manufacturing components of diverse end applications. Deep drawability, which is one of the crucial property of steel for forming application, is influenced by factors like alloy chemistry, microstructure, texture evolution and precipitation characteristics. All these microstructural factors are in turn affected directly by the annealing process employed. In the present study, specially designed continuous annealing process has been employed to assess the influence of boron to nitrogen (B/N) ratio (0-0.87)on mechanical and drawing properties of low carbon (0.03-0.035 wt %), low manganese (0.15-0.18 wt%) and low sulphur (0.005-0.008 wt%) steel. Steel with B/N ratio of 0.185resulted into best combination of properties in terms of lowest YS/UTS ratio (0.81),high plastic anisotropy (r(m):1.545) along with 310 MPa yield strength, 380 MPa ultimate tensile strength, 20% uniform elongation and 32% total elongation. It has been found that the B/N ratio, rather than the absolute boron, influences the precipitation characteristics of carbides and favorable texture development during continuous annealing process.