| abstract |
(57) [Summary] [Problem] An average ferrite particle size is 1 μm or less, and Provided is a method for producing a high-strength steel material having excellent low-temperature toughness and crack propagation arresting characteristics by having a fine-grained ultrafine-grained ferrite structure having a small mixed grain size. SOLUTION: After heating a steel slab having limited components and an ideal quenching critical diameter to a temperature not lower than the Ac 3 transformation point and not higher than 1150 ° C., the cumulative rolling reduction is 55 to 80%, and the rolling start temperature is 8 After performing the first rolling at 50 ° C. or less and the finishing temperature at 750 ° C. or more, rolling includes rolling at a rolling reduction of 30 to 70% per pass in one or more passes, cumulative rolling reduction of 50 to 95%, and rolling. Second temperature with start temperature of 700 ° C or less and end temperature of 600 ° C or more A method for producing a high-tensile steel excellent in low-temperature toughness, characterized by rolling. Addition of pretreatment for refining prestructure, It is preferable to appropriately add further elements such as Ti, V, and Nb. |