50 A method of manufacturing steel in the 50Kgf/mm2 grade for shipbuilding

摘要

PURPOSE: A preparation method of the steel for shipbuilding in a class of the tensile strength of 50 kgf/mm¬2 is provided to satisfy the properties of AH36 and DH36 steel materials by only the recrystallization range high temperature rolling without the accelerated cooling and apply to the high temperature processing owing to the high thermal stability. CONSTITUTION: The preparation method of the steel for shipbuilding in a class of the tensile strength of 50 kgf/mm¬2 comprises heating the ingots obtained by casting the low alloy steel molten metal composed of 0.12 to 0.17 wt.% of C, not more than 0.5 wt.% of Si, 1.1 to 1.6 wt.% of Mn, 0.01 to 0.06 wt.% of sol. Al, 0.005 to 0.02 wt.% of Ti, not more than 170 ppm of N, 0.05 to 0.10 wt.% of V, not more than 0.03 wt.% of P, not more than 0.02 wt.% of S, and the rest of Fe and the other inevitable impurities, and satisfying the Ti/N of 0.29 to 3.42 in a cooling rate of at least 10 deg.C/min from the solidifying point to 1100 deg.C, in the temperature of 1100 to 1300 deg.C, then strong pressing with the mean pressing ratio of at least 20%, rolling in the finishing rolling temperature condition of 850 to 1000 deg.C, and then air cooling to the room temperature.