Development of New Steel Grades and Products - 'Casting and Rolling of API X70 Grades for Arctic Applications in Thin Slab Rolling Plant'

摘要

Hot band is becoming more and more attractive in the steel market for the most demanding applications, once achievable only from heavy plates. The Danieli Wean United (DWU) flexible thin slab rolling technology has proven to be a reliable tool to produce API steel grades for line pipes applications, starting from a thin slab caster instead of a conventional route. In such way, HSLA steel strip products have proven to be highly compatible with thin slab casting and direct charging process. Several heats of the said HSLA steels have been cast and rolled in cooperation with Ezz Flat Steel who runs one of the most modern and competitive hot strip mill plants, completely supplied by Danieli & C, on which the process has been successfully developed. The main facilities of the said plant consist of an Electric Arc Furnace (EAF), a Ladle Furnace (LF), a 90-70 mm Thin Slab Caster (TSC) and a Hot Strip Mill (HSM) composed by one roughing stand, a heated transfer table and six finishing stands. Purpose of the trial production was to check the industrial conditions suitable to produce, cast and roll high strength low alloy steel grades, particularly the API X70 for arctic applications, which requires severe mechanical properties and parameters. It is necessary to underline that this has been the very first time in the world that an arctic API X70 has ever been cast and rolled in a flexible Thin Slab Rolling (fTSR) plant. As a final result, we have confirmed that the thin s lab casting operations are particularly suited to produce hot rolled coils of HSLA steels, even for applications in severe environmental conditions, having achieved characteristics above standards, since the first trial heats.