HOT-ROLLED STEEL SHEET AND METHOD OF ITS PRODUCTION Russian patent published in 2014 - IPC C21D8/02 C22C38/14 C21D9/46 

FIELD: metallurgy.

SUBSTANCE: hot-rolled steel sheet is produced to meet the preset requirements and to satisfy the terms 0<S/Ca<0.8, N-14/48×Ti≥"0" (zero), wt %. Note here that fraction of proeutectoid ferrite makes 3% or larger and 20% or less, the rest represents the low-temperature conversion in microstructure at half the sheet depth over sheet depth from steel sheet surface. Mean-size of crystalline grain of the entire microstructure makes 2.5 mcm or less. Grain size averaged over the area makes 9 mcm or less. Mean square deviation from grain size averaged over the area makes 2.3 mcm or less. Relation of X-ray reflex intensities {211}/{111} in directions {211} and {111} relative to plane parallel about steel sheet surface at half the sheet depth over sheet thickness from sheet surface makes 1.1 or more.

EFFECT: higher toughness and strength relative to standard API5L-X80 or larger.

13 cl, 4 tbl, 14 dwg