Low-carbon steel slab producing method

Abstract

A low-carbon steel slab producing method includes: adding Ti to a molten steel decarbonized to have a carbon concentration of 0.05 mass % or less, and subsequently adding at least one of La and Ce to adjust a constitution, and producing a smelted molten steel; and pouring the smelted molten steel into a casting mold via a tundish; wherein at least one of La and Ce in a total amount of 0.2 to 1.2 times an increased amount of oxygen in the smelted molten steel during contained in the tundish is added to the smelted molten steel in the tundish, so as to obtain a steel slab having inclusions which contain oxides of Ti and at least one of La and Ce as chief components, and so as to make a composition of each of the inclusions have a mass ratio of 0.1 to 0.7, in terms of (La 2 O 3 +Ce 2 O 3 )÷TiO n (n=1˜2).

1 . A low-carbon steel slab producing method, comprising:
 adding Ti to a molten steel decarbonized to have a carbon concentration of 0.05 mass % or less, and subsequently adding at least one of La and Ce to adjust a composition, and producing a smelted molten steel used for a low-carbon steel slab, containing, by mass %, more than 0% and equal to or less than 0.05% of carbon, more than 0% and equal to or less than 0.01% of Si, more than 0% and equal to or less than 0.5% of Mn, more than 0% and equal to or less than 0.05% of P, more than 0% and equal to or less than 0.02% of S, more than 0% and equal to or less than 0.01% of Al, more than 0.01% and equal to or less than 0.4% of Ti, and in combination, 0.001% or more and 0.01% or less of at least one of La and Ce, and 0.004% or more and 0.02% or less of oxygen, and iron as a base component; and   pouring the smelted molten steel into a casting mold via a tundish, wherein   at least one of La and Ce in a total amount of 0.2 to 1.2 times an increased amount of oxygen in the smelted molten steel during contained in the tundish is added to the smelted molten steel in the tundish, so as to obtain a steel slab having inclusions which contain oxides of Ti and at least one of La and Ce as chief components, and so as to make a composition of each of the inclusions have a mass ratio of 0.1 to 0.7, in terms of (La 2 O 3 +Ce 2 O 3 )÷TiO n  (n=1˜2).