| 摘要 |
The present invention relates to a method to manufacture a medium-carbon non-normalized steel capable of compensating a nitrogen component capable of preventing a reoxidation of molten steel passed through a vacuum degassing process while preventing a formation of a nonmetallic inclusion by first inserting a nitrogen alloy wire (FeMnN or FeCrN) to the molten steel passed through the vacuum degassing process, and reducing the amount of nitrogen contained in the nitrogen alloy wire to reduce the reactivity of molten steel and a nitrogen alloy. The present invention comprises: (S1) a step of injecting nitrogen gas to the molten steel from a start of an LF refining process to an end of the LF refining process; (S2) a step of performing the vacuum degassing process; (S3) a step of inserting the nitrogen alloy wire to compensate the nitrogen component until the amount of nitrogen contained in the molten steep becomes 140-200 ppm; (S4) a step of steadying the molten steel by softly bottom-stirring; (S5) a step of inserting a calcium-silicon (Ca-Si) alloy wire to the molten steel to compensate a calcium-silicon (Ca-Si) component until the amount of the calcium-silicon (Ca-Si) contained in the molten steel becomes 300-400 ppm; and (S6) a step of inserting a sulfur (S) wire to the molten steel to compensate a sulfur (S) component until the amount of the sulfur contained in the molten steel becomes 400-450 ppm. |
