METHOD OF MANUFACTURE OF THE STEEL SHEETS HAVING THE TWO-PHASE STRICTURE Russian patent published in 2007 - IPC C21D8/02 C21D9/48 C23C2/06 

FIELD: metallurgy industry; methods of manufacture of the steel sheets with the two-phase structure.

SUBSTANCE: the invention is pertaining to the field of metallurgy industry, in particular, to the method of manufacture of the hot-galvanized sheets. The technical result of the invention is production of the two-phase ferrite-martensite microstructures at the ratio of the steel yielding limit at tension of no more than 0.5. The steel sheet having the two-phase microstructure is manufactured with utilization of the time/temperature cycle including the steel cementation approximately at 727-774°С and aging at 454-493°С. The steel has the following composition (in mass %): carbon - 0.02-0.20, aluminum - 0.010-0.150, titanium - maximum up to 0.01, silicon - maximum up to0.5, phosphorus - maximum up to 0.060, sulfur - maximum up to 0.030, manganese - 1.5-2.40, chromium - 0.03-1.50, molybdenum - 0.03-1.50; provided that the quantities of manganese, chromium and molybdenum have the ratio: (Mn+6Cr+10Mo) = at least 3.5 %. It is preferable, that the steel sheet is made in the form of the band treated on the production line of the continuous galvanization or the annealing and galvanization, and the product represents predominantly ferrite and martensite.

EFFECT: the invention ensures production of the two-phase ferrite-martensite microstructures of the steel sheet at the ratio of the steel yielding limit at tension of no more than zero point five.

19 cl, 6 dwg, 4 tbl, 5 ex