HIGH STRENGTH HOT-GALVANISED STEEL SHEET AND HIGH STRENGTH ANNEALED AFTER GALVANISING STEEL SHEET WITH EXCELLENT MOULDABILITY AND ABILITY TO APPLICATION OF ELECTRO-DEPOSIT; PROCEDURES AND DEVICES FOR FABRICATION OF SUCH SHEETS

摘要

FIELD: metallurgy.;SUBSTANCE: procedure for fabrication of said steel sheet or steel sheet annealed upon galvanising consists in continuous hot-galvanising high strength steel sheet containing Si and Mn or C, Si and Mn. During galvanising there is ensured presence of oxides of Si of at least one type chosen from FeSiO₃, FeSiO₄, MnSiO₃ and Mn₂SiO₄ on surface of steel or surface of division of steel sheet and electro-deposit. Also, oxides of SiO₂ type should be present on internal side of steel sheet surface to form a zinc coated layer or a layer of electro-deposit out of alloy of zinc on high strength steel sheet; after zinc coating steel sheet is annealed. Steel sheet contains in wt %, C from 0.05 to 0.25 %, Si from 0.3 to 2.5 %, Mn from 1.5 to 2.8 %, P 0.03 % or less, S 0.2 % or less, Al from 0.005 to 0.5 %, N 0.0060 % or less, the rest is Fe and unavoidable impurities. At fabrication of the said steel sheet in a reduction furnace there is implemented equipment including a device for introduction of generation of gas containing CO₂ at amount from 1 to 100 vol. %, the rest is N₂, H₂O, O₂, CO₂ and unavoidable impurities. The equipment controls potential of oxygen on surface of steel sheet in furnace.;EFFECT: production of high strength hot-galvanised sheet and high strength annealed after galvanising steel sheet of required appearance with excellent adhesion of electro-deposit, mouldability and resistance to corrosion.;22 cl, 6 dwg, 18 tbl, 10 ex