HIGH-STRENGTH STEEL PLATE, STEEL PLATE WITH PROTECTIVE COATING APPLIED BY MELT DIPPING, AND STEEL PLATE WITH ALLOYED PROTECTIVE COATING, WHICH HAVE EXCELLENT FATIGUE PROPERTIES, ELONGATION CHARACTERISTICS AND IMPACT PROPERTIES, AND METHOD FOR OBTAINING ABOVE DESCRIBED STEEL PLATES Russian patent published in 2013 - IPC C22C38/14 C21D8/02 C21D9/46 

FIELD: metallurgy.

SUBSTANCE: steel slab contains the following, wt %: 0.03 - 0.10% C; 0.01 - 1.5% Si; 1.0 - 2.5% Mn; 0.1% or less P; 0.02% or less S; 0.01 -1.2% Al; 0.06 - 0.15% Ti and 0.01% or less N; iron and inevitable impurities are the rest, heated to the temperature of 1150 to 1280°C and hot rolling is performed under conditions when finish rolling is ended at the temperature in the range of not less than point Ar₃, thus obtaining hot-rolled material. Hot-rolled material is wound in the temperature range of 600°C or less for obtaining hot-rolled steel plate. Acid etching is performed and the first rolling of the etched steel plate is performed with elongation degree in the range of 0.1 to 5.0%. Steel plate is annealed with further second rolling. Protective alloying coating can be applied to the plate. Tensile strength is 590 MPa or more; relationship between tensile strength and yield point is 0.80 or more, and microstructure contains bainite on the portion of the surface area of 40% or more, ferrite and/or martensite is the rest, and density of inclusions Ti(C,N) having the size of 10 nm or less is 10¹⁰ inclusions per mm³ or more, and ratio (Hvs/Hvc) of hardness (Hvs) at the depth of 20 mcm from the surface to hardness (Hvc) in centre of the plate thickness is 0.85 or more.

EFFECT: produced plates have the required set of strength, fatigue and impact properties, as well as elongation.

14 cl, 14 dwg, 16 tbl