New vanadium-microalloyed bainitic 700 MPa strip steel product

Abstract

Hot rolled strips having a minimum yield stress of 700 MPa have been produced in full scale processing. Alloy additions (1?5%Mn, 1%Cr and 0?3%Mo) together with rapid cooling on the runout table produce fully bainitic microstructures which confer strength and toughness. Microalloying with 0?08%V has been shown to be essential for achieving stable strength levels that are independent of the coiling temperature since the necessary low coiling temperatures are difficult to reproduce accurately under steelworks conditions. The products have excellent bendability and HAZ toughness. Typical microstructures and textures of the hot rolled strips are also presented.

Comparative Effect of Mo and Cr on Microstructure and Mechanical Properties in NbV-Microalloyed Bainitic Steels

“…In 0.042C-0.3Mo-1.0Cr-0.08V steel coiled in the temperature range of 180-530 • C, Hutchinson et al [38] observed bainitic microstructures with average ferrite grain size of 3 µm. Increased to 640-770 MPa proof stress was suggested to originate mainly from high dislocation density in bainite and, in particular, dislocation pinning by V(C,N) precipitates.…”

Modeling and Composition Design of Low-Alloy Steel’s Mechanical Properties Based on Neural Networks and Genetic Algorithms

“…Molybdenum: Mo increases the strength by increasing the hardenability of steel. The addition of Mo can inhibit the formation of eutectoid ferrite and pearlite during the hardening process [ 63 , 64 ], forming a small amount of overaged martensite islands and promoting the formation of hardened phases, such as bainite and martensite [ 64 , 65 ], to increase the steel yield strength. Mo is a strong carbide-forming element that is mainly present in solid solutions and carbides in alloy steel.…”

Effect of Alloying and Coiling Temperature on the Microstructure and Bending Performance of Ultra-High-Strength Strip Steel

“…Photographs of typical bend tested samples are illustrated in Fig. 2a and the average values of inner-bend-angle and minimum bend-radius to thickness ratio (Rmin/t) are listed in to Hutchinson et al [30] and Datsko et al [31] the smaller the Rmin/t ratio the better the bending performance of a material. Hutchinson et al suggested Rmin/t ratio to be maintained below 2.5…”

“…for ensuring satisfactory bending performance [30] . Although the best bending ratio obtained in the present study for Ti-460 sample is 3.7, this value may not be directly comparable with the earlier studies due to the difference in specimen size.…”