The invention relates to an easy-to-weld container plate with the thickness
ranging from 40 millimeters to 60 millimeters and the excellent center low-temperature
toughness, and a making method thereof. The steel plate comprises the
chemical ingredients, by
mass, 0.04% to 0.09% of C, equal to or smaller than 0.40% of Si, 1.00% to 1.60% of Mn, equal to or smaller than 0.008% of P, equal to or smaller than 0.002% of S, 0.12% to 0.30% of Mo, equal to or smaller than 0.10% of the sum of Nb, V and Ti, 0.20% to 0.60% of Ni, 25 ppm to 55 ppm of N, equal to or smaller than 2ppm of H, the balance Fe and unavoidable
impurity elements. Meanwhile, the steel plate meets the conditions that Pcm is equal to or smaller than 0.20%, w(Nb+V) / w(Ti) ranges from 10 to 30, the yield strength of the steel plate is larger than or equal to 490MPa, the tensile strength Rm of the steel plate is larger than or equal to 620MPa, the elongation A is larger than or equal to 21%, the
yield ratio is equal to or
smallerthan 0.88, the side knock power minus 50 DEG C KV2 of the position of one fourth of the thickness of the plate is larger than or equal to 220 J, and the side knock power minus 50 DEG C KV2 of the position of one second of the thickness of the plate is larger than or equal to 100 J. The method comprises the following working steps of molten iron pretreatment, converter
smelting,
ladle furnace refining, vacuum treatment,
continuous casting,
casting blank cover cooling,
casting blank heating, controlled rolling, controlled cooling, stack retarded cooling,
quenching,
tempering, flaw detection andperformance examination. The easy-to-weld container plate with the thickness
ranging from 40 millimeters to 60 millimeters and the excellent center low-temperature
toughness not only has the excellenttoughness matching, but also has the excellent center low-temperature
impact toughness, and thereby meeting the requirements on steel for a large spherical tank.