| 摘要 |
FIELD: metallurgy; production of the plate steel f0r pipelines. SUBSTANCE: invention relates to production of a pipeline plate steel, that has tensile strength of at least 930 MPa, an impact energy measured in the test of the product samples with a V-shaped inspection by Sharpy at 40 C - at least 120 J, and a microstructure, that contains at least 90 vol.% of a mixture of a fine-grained inferior bainite and fine-grained mesh martensite, and where at least 2/3 of indicated mixtures is the fine-grained inferior bainite formed from non-recrystallized austenite, having average size of grains less than 10 microns and containing (in weight %): carbon - 0.05-0.1, manganese - 1.7-2.1, nickel - 0.2-1.0, niobium - 0.01-0.1, titanium - 0.005-0.03, sulfur - less than 0.003, phosphorus - less than 0.015, molybdenum 0.25-0.6, iron - the rest. The steel is produced by heating of a steel block up to 1050-1250 C, then reduce the steel block thickness producing a steel sheet by one or several its passes on the hot rollers in the interval of temperatures of austenite recrystallization. Then the thickness of the steel sheet is additionally reduced and the indicated steel sheet is hardened, then they give a sheet to be cooled by cool air down to the ambient temperature. EFFECT: increased strength of the steel at the ratio of its yield stress to its limit tensile strength less than 0.93. 40 cl, 10 dwg, 4 tbl
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