Patent ID: 9149867
Filing Date: 2015-10-06
Classification: B22D,C21C,C22C

Abstract:
1. A low-carbon steel slab producing method, comprising: adding Ti without carrying out Al pre-deoxidation to a decarbonized molten steel having a carbon concentration of 0.0013 mass % or less; subsequently adding at least one of La and Ce to adjust a composition; producing a smelted molten steel, used for a low-carbon steel slab, containing, by mass %, more than 0% and equal to or less than 0.0013% 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% Mn, more than 0% and equal to or less than 0.05% P, equal to or more than 0% and equal to or less than 0.02% of S, 0.01% or more 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; pouring the smelted molten steel into a casting mold via a tundish, wherein after producing smelted molten steel having inclusions which contain oxides of Ti and at least one of La and Ce as chief components, measuring the oxygen concentration of the molten steel at a downstream of the tundish with an oxygen sensor and determining an increased amount of oxygen in the smelted molten steel picked up during the time the smelted molten steel was contained in the tundish, and continuously adding at least one of La and Ce to the smelted molten steel in the tundish, in wire form, in a total amount of 0.2 to 1.2 times the determined increased amount of oxygen, 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 with a mass ratio of 0.1 to 0.7, in terms of (La