To provide a steel pipe blank improving low temp. toughness in the position at the initial stage of casting in a continuously cast slab and having uniform low temp. toughness in the casting direction by improving a continuous casting method.
Additive 1 of ferro-nickel alloy or ferro-titanium alloy, etc., is beforehand laid in a tundish 2 and thereafter, molten steel 8 is poured into the tundish 2, and after melting the additive 1 into the molten steel, the casting is executed. By this method, the low temp. toughness in the position at the initial stage of casting in the continuously cast slab. The additive 1 is desirably beforehand-laid in the range arranged with a weir 6 for beforehand-laying between pouring holes 3 into molds 7 in the tundish 2.
KOSEKI TOMOYA
HASUNUMA JUNICHI
