SPHEROIDAL GRAPHITE CAST IRON TUBE AND METHOD FOR PRODUCING THE SAME

PROBLEM TO BE SOLVED: To provide a spheroidal graphite cast iron tube which has high strength and high toughness. SOLUTION: The spheroidal graphite cast iron tube having high strength and high toughness has a composition containing, by weight, 3.20 to 4.00% C, 1.40 to 3.00% Si, 0.10 to 1.00% Mn, 0.02 to 0.08% Mg and 0.01 to 0.20% Cr, and further containing at least one kind selected from Sn and Cu in the range satisfying 0.050≤Sn (wt.%)+Cu (wt.%)/10≤0.089, and the balance Fe with inevitable impurities, and the spheroidal graphite cast iron tube has constitution in which the area ratio of pearlite with coarse interlayer spacing in the matrix structure is 50 to 90%, the number of grains of graphite crystallized out in the matrix structure is controlled to ≥300 pieces/mm2and the average grain diameter thereof is controlled to ≤15 μm, consequently the high strength and high toughness spheroidal graphite cast iron tube having tensile strength equal to that of FCD600 and elongation equal to or above that of FCD450 is obtained. COPYRIGHT: (C)2011,JPO&INPIT