IN-LINE PROCESS FOR THE RECRYSTALLIZATION OF SOLIDIFIED COARSE STRIPS IN CARBON STEEL AND IN LOW-ALLOYED STEEL

摘要

The invention refers to an in-line process for the making of strips in carbon steel and in low-alloyed steel by a recrystallization (rolling and annealing) treatment of solidified coarse strips, having a coarse structure, aimed at inducing an advanced recrystallization of the material with homogenizing, refining and checking of the end microstructure, and the entailed improvement of the mechanical properties, in terms of a mix of strength and ductility/cold formability, and of the reproducibility thereof. This process comprises the following steps: casting, in a twin-roll continuous casting machine (A) of strips having a thickness ranging from 1 to 6 mm and a composition, expressed as percent by mass, comprising the following components: 0.02-0.20 C; 0.1-1.6 Mn; 0.02-2.00 Si; 0.05 A1; 0.03 S; 0.1 P; 0.01-1.5 Cr; 0.01-0.5 Ni; 0.5 Mo; 0.003-0.012 N, with substantially Fe q.s. to 100; controlled cooling of the strip in the section comprised between the casting rolls and a rolling system (E); holding the strip at a controlled temperature in an insulated system (F) comprised between an outlet of the rolling system (E) and an inlet in a heating system (G); heating the strip with said heating system (G) at temperatures ranging from 670 to 1150 °C for times ranging from 5 to 40 s, so as to attain a 95% b/v strip recrystallization; ▪ controlled cooling in the section comprised between an outlet of said heating system (G) and a wrapping system.