PROCEDURE FOR PRODUCTION OF PLATE IRON LOW-ALLOYED STRIP Russian patent published in 2010 - IPC C21D8/02 C22C38/58 

FIELD: metallurgy.

SUBSTANCE: work-piece in strips of 20-40 mm thickness is produced out of steel with following contents of elements, wt %: 0.03-0.06 C; 1.5-1.7 Mn; 0.15-0.35 Si; 0.15-0.3 Ni; 0.04-0.06 Nb; Cr≤0.2; 0.08-0.15 Mo; 0.15-0.3 Cu; 0.02-0.04 V; 0.005-0.02 Ti; 0.02-0.05 Al, iron and impurities, where contents of each element of impurity is less 0.03%, - the rest. Also carbon equivalent is C_equiv≤0.4. Further the work-piece is subject to roughing at temperature 1000-920°C and shrinkage not less, than 9 % per one pass in the first two passes, and not less, than 12 % per pass in the following passes from thickness of a breakdown bar, depending on thickness of a finished strip, determined from the following ratio: H_{breakdown bar}=(161.5+0.0955·h_str ²-4.6191·h_str)±5 mm. The breakdown bar is cooled to 760-800°C and is finish rolled at shrinkage ratio not less, than 12% per pass excluding three last passes. Successively the finished strip is cooled with acceleration to temperature, depending on its thickness, determined from the ratio: T_{coeff. of cooling}=(422-0.1364*h_str ²+3,6273*h_str)±15°C and is cooled with delay.

EFFECT: high durability combined with high processability, plasticity and cold resistance.

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