PRODUCTION OF SUPERFINE STRUCTURE STEEL

摘要

PROBLEM TO BE SOLVED: To form a superfine structure having not more than a specified average grain diameter by repeating forging many times at the temperature of the austenitic zone or the metastable austenitic zone after heating a steel to not lower than Ac3, austenizing and thereafter executing rolling of not lower than a specified reduction of area at the temperature range between temperatures not lower than a specified temperature and not higher than Ac3. SOLUTION: Repeated forging is executed and thereafter the rolling is executed in >=70% reduction of area at the temperature range of >=550 deg.C to <=Ac3 to form the superfine structure having <=2μm average grain diameter. The forging is preferably be changed so as to be >=30% reduction of thickness at the first forging and be in the range of 45 deg.-90 deg. of the reducing direction relative to the reducing direction just before forging at and after the second forging. A superfine structure steel plate having fine finish texture from the steel plate having >=5 mm thickness and >=10 times width of the thickness can be produced by specifying individual working conditions while continuing the forging and the rolling.