HIGH STRENGTH AND HIGH TOUGHNESS QUENCHED AND TEMPERED LOW-CARBON STEEL PLATE FOR BOILER OR PRESSURE VESSEL HAVING SUPERIOR RESISTANCE TO WELD CRACK, EROSION AND CREEP

摘要

PURPOSE:To obtain a high strength and high toughness quenched and tempered low-C steel plate for a boiler or a pressure vessel having superior resistance to weld crack, erosion and creep by remarkably reducing the amount of C and adding Cu, Ni, and Cr as well as B. CONSTITUTION:The composition of a steel plate is composed of, by weight, 0.02-0.12% C, 0.05-1% Si, 0.3-1.5% Mn, 0.05-0.19% Cu, 0.05-0.39% Ni, 0.05-0.4% Cr, 0.03-0.45% Mo, 0.005-0.1% Cu, 0.05-0.39% Ni, 0.05-0.4% Cr, 0.03-0.45% Mo, 0.005-0.1% acid-sol. Al, 0.0003-0.002% B, 0.005% N and the balance Fe with inevitable impurities. In the composition, conditions represented by equation I are satisfied, and the value PCM calculated by equation II is restricted to =0.23%. The percentage of bainite in the structure after normalizing is regulated to 20-85%.