Steven L Wigman

US Patent:

6669789, Dec 30, 2003

Filed:

Aug 31, 2001

Appl. No.:

09/945185

Inventors:

Daniel Geoffrey Edelman - Indianapolis IN
Steven Leonard Wigman - Brownsburg IN

Assignee:

Nucor Corporation - Charlotte NC

International Classification:

C22C 3814

US Classification:

148320, 420126, 420128, 148541, 148546, 148547

Abstract:

A composition and method of making a high-strength low-alloy hot-rolled steel sheet, strip, or plate bearing titanium as the principal or only microalloy strengthening element. The steel is substantially ferritic and has a microstructure that is at least 20% acicular ferrite. The steel has a minimum yield strength of at least 345 MPa (50 ksi) and even over 621 MPa (90 ksi) adding titanium as the lone microalloy element for strengthening, with elongation of 15% and more. Addition of vanadium, niobium, or a combination thereof can result in yield strengths exceeding 621 MPa (90 ksi). Effective titanium content, being the content of titanium in the steel not in the form of nitrides, oxides, or sulfides, is in the range of 0. 01 to 0. 12% by weight. The manufacturing process includes continuously casting a thin slab and reducing the slab thickness using thermomechanical controlled processing, including dynamic recrystallization controlled rolling.