HOT ROLL FOR USE IN PIPELINE AND METHOD OF ITS MANUFACTURING Russian patent published in 2015 - IPC C22C38/14 C22C38/58 C21D8/02 

FIELD: metallurgy.

SUBSTANCE: chemical composition of steel includes in wt %: C from 0.03 to 0.10, Si from 0.01 to 0.50, Mn from 0.5 to 2.5, P from 0.001 to 0.03, S from 0.0001 to 0.0030, Nb from 0.0001 to 0.2, Al from 0.0001 to 0.05, Ti from 0.0001 to 0.030, B from 0.0001 to 0.0005, and iron and inevitable impurities are the rest. Steel plates are held for pre-set time period between rolling runs within recrystallization temperature range, and cooling after hot rolling is performed by two stages. Steel structure in central part through strap thickness has effective size of crystal grains from 3 to 10 microns. Sum of areas of beinite and needle ferrite is from 60 to 99%. Strap thickness is from 7 to 25 mm, and absolute difference A-B of sums of areas of beinite and needle ferrite at any two sections of the strap is from 0 to 30%, where sums of areas of the beinite and needle ferrite at these two sections are designated as A and B, respectively.

EFFECT: reduced strength deviation at common temperature and increased low temperature impact toughness.

7 cl, 2 dwg, 6 tbl, 1 ex