FIELD: metallurgy.
SUBSTANCE: the invention relates to metallurgy, in particular, to steel plates with high expanding endurance suitable for use in construction equipment, for tanks, pressure pipes and pipelines. The steel of the following composition is melted and cast, %: C: 0,02-0,25; Si: 0,01-0,8; Mn: 0,5-2,0; Al: 0,005-0,1; N: от 0,0005 до 0,008; P: 0,02 or less; S: 0,004 or less, preferably S 0,003 or less, and, if needed, one of more elements from Mo: 1 or less, Ti: 0,1 or less, V: 0,5 or less, Ti: 0,1 or less, Cu: 2 or less, Ni: 4 or less, Cr: 2 or less and W: 2 or less, B: 0,003 or less, Ca: 0,01 or less, rare metals: 0,02 or less and Mg: 0,01 or less, rest - Fe and inevitable additives. The steels are protected from cooling down to temperature Ar3 or below; and from heating to the temperature equal or above the conversion temperature Ac3. The steel is hot-rolled to achieve the required steel width, including the rolling of non-recrystallized portions. The steel is rolled with the reduction ratio of 30% or above. The steel is cooled from the temperature equal or above the conversion temperature Ar3 to the temperature equal or below 350°C with cooling rate of 1°C/second or more, and the steel is relieved at the temperature equal or below the conversion temperature Ac1. The average aspect ratio of primary austenite pellets along the plate width is at least three, whereas the portion of cementite deposited on the boundaries of marsentine plate pellets is 50% or less.
EFFECT: steel has high resistance against delayed fracture and expanding endurance limit of at least 600 MPa.
11 cl, 2 dwg, 12 tbl, 2 ex
