Cu CU-CONTAINING LOW ALLOY COPPER HAVING EXCELLENT BALANCE BETWEEN STRENGTH AND LOW-TEMPERATURE TOUGHNESS AND METHOD FOR PRODUCING SAME

강도와 저온 인성의 밸런스가 우수한 Cu 함유 저합금강을 제공한다. Cu 함유 저합금강은 질량%로 C:0.01∼0.08%, Si:0.10∼0.40%, Mn:0.80∼1.80%, Ni:0.80∼2.50%, Cr:0.50∼1.00%, Cu:0.80∼1.50%, Mo:0.20∼0.60%, Al:0.010∼0.050%, Nb:0.030∼0.080%, N:0.005∼0.020%를 함유하고, 소망에 의해 Ca:0.010% 이하를 더 함유하고, 잔부가 Fe 및 불가피 불순물로 이루어지는 화학조성을 갖고, 0.2% 내력이 525㎫ 이상이며, 또한 2㎜ V노치 샤르피 충격시험에서 측정된 연성 취성 파면 천이온도(FATT)가 -70℃ 이하를 갖는다. Provided is a Cu-containing low alloy steel having excellent balance between strength and low-temperature toughness. The Cu-containing low alloy steel has a chemical composition comprising, by mass%, C: 0.01 to 0.08%, Si: 0.10 to 0.40%, Mn: 0.80 to 1.80%, Ni: 0.80 to 2.50%, Cr: 0.50 to 1.00%, Cu: 0.80 to 1.50%, Mo: 0.20 to 0.60%, Al: 0.010 to 0.050%, Nb: 0.030 to 0.080%, and N: 0.005 to 0.020%, and further comprising Ca: 0.010% or less as needed, and consisting of Fe and inevitable impurities as the balance; has a 0.2% yield strength of 525 MPa or higher. The Cu-containing low alloy steel has a ductile-brittle fracture appearance transition temperature (FATT) as measured by the 2 mm V-notch Charpy impact test of -70°C or less.