| 摘要 |
PROBLEM TO BE SOLVED: To efficiently produce a bearing steel material of an excellent rolling fatigue life by making the diameter of oxide inclusions small, controlling the composition of sulfide inclusions within a prescribed range, and by controlling the size of the inclusions small, without performing Ca-adding treatment.SOLUTION: A steel material includes 0.0010% or less of O and 0.0040% or less of S, and satisfies a prescribed chemical composition as a high carbon chromium bearing steel material. A ladle refining treatment is carried out in order of steps 1 to 3 to control sulfide inclusions so that a S-containing compound constituting the sulfide inclusions has an average composition comprising CaS: at least 1.0%, and MgS: 0 to 20%, with the total of the three components, i.e., CaS, MgS and MnS being at least 95%. In the step 1, refining flux comprising CaO: 40 to 70% and AlO: 30% or less is blown via a bubbling lance into molten steel tapped into a ladle from a converter or an electric furnace, in an amount of 1.0 to 3.6 kg per ton of the molten steel. In the step 2, a refining agent is added so that the composition of slug on the molten steel upon completing the step 2 includes CaO: 35 to 65%, AlO: 10 to 35%, SiO: 10% or less (excluding 0%), MgO: 0 to 15%, and CaF: 0 to 30%, with CaO/SiObeing 6.0 or higher and CaO/AlObeing 1.8 to 3.5, and that the amount of the slug is 5 to 15 kg per ton of the molten steel, and the molten steel and the slug on the molten steel are stirred together with the refining agent having been added thereinto. In the step 3, the molten steel is circulated for 20 minutes after adjusting the components of the molten steel using a vacuum degassing device of a molten-steel circulation type. |
