Recrystallization-based formation of uniform fine-grained austenite structure before polymorphic transition in high-strength steels for Arctic applications

Abstract

Background: Growing demand for materials suitable for Arctic marine constructions necessitates the development of lowcost steels with excellent low-temperature properties. One way of addressing this issue is to obtain a finegrained structure by careful control of the recrystallization process. Methods: The research methods used in this paper includes conducting experiments and making observations. The study investigates mechanisms of grain structure formation in low-carbon cold-resistant F620 steels additionally alloyed with Nb or V during hot plastic deformation. Results: The obtained results evidence that static recrystallization is the most effective means to refine the austenite structure under conditions of industrial rolling. On this basis, a temperature-strain scheme of fractional hot rolling is proposed that provides the most refined uniform structures of bainite and/or martensite after quenching. Additionally, the results show that substitution of the alloying element V by Nb makes the structure of the hot-rolled austenite more finely dispersed. Conclusions: New cold-resistant F620 steels for Arctic applications alloyed with Nb of 50-mm thickness were produced utilizing the research results. These grades of steels have reduced alloying content and exhibit improved properties, in particular, cold resistance down to −60°С and high fracture toughness at −50°С.

Texture Analysis of Hot Rolled Martensitic and Bainitic Steels by Electron Backscatter Diffraction to Quantify Parent Austenite States

“…At the same time, apart from hot rolling modes leading to the deformed parent phase, other modes which result in its recrystallization in numerous pauses between sequential passes are sometimes applied to refine prior grains. [31,32] In this case, it is advisable to make use of an alternative parameter derived from recrystallization rather than deformation contributions to the parent texture.…”

Numerical Investigations on Residual Stress in Laser Penetration Welding Process of Ultrafine‐Grained Steel

“…where q is the intensity of the laser heating source, T is the temperature, t is the time, Δ is the point spatial vector (x, y, z), and ρ, c, and k are the density, specific heat, and thermal conductivity, respectively. e HAZ in the ultrafine-grained steel was a major concern in many studies [21,22]. In the HAZ, the microstructure of the ultrafine-grained steel undergoes severe transformations due to the influence of the welding thermal cycle, and the structure of the overheated zone changes significantly under the influence of the welding heat [21].…”