FIELD: process engineering.
SUBSTANCE: invention relates to production of multiphase-structure hot-rolled strip from steel with TRIP-effect. Foundry-mill plant is used to produce thin slab from steel melt with preset chemical composition. Strip is subjected to hot finishing rolling and adjusted cooling after deformation at final mill stand. Note here that thin slab is produced from steel comprising in wt %: C-0.12-0.25, Si-0.05-1.8, manganese -1.0-2.0, iron and unavoidable impurities making the rest. Rolling and cooling conditions are varies to produce multiphase structure consisting of ferrite 40-70%, bainite 15-45% and retained austenite 5-20%. Note here that deformation of strip 7 at final mill stand is carried out at 770°C to 830°C, exceeding a bit Ar3 in the region of metastable austenite, austenite grain size making d<8 mcm, while immediately after said final mill stand 6', controlled two-step cooling of hot-rolled strip 7 is performed to temperature of 320°C to 480°C, in the region of bainite formation, with flashoff at approximately 650-730°C, flashoff beginning being defined by transition of cooling curve in ferrite region and flashoff duration being defined by time required for austenite to get converted into at least 40%-ferrite.
EFFECT: higher quality.
4 cl, 3 dwg
