| 摘要 |
PURPOSE:To enhance a denitrifying effect when steel for a low nitrogen steel plate is manufactured, by reducing the amts. of C, S and free oxygen in molten steel and denitrifying the molten steel with a rare earth metal. CONSTITUTION:In order to improve the toughness of the weld zone of a steel plate, the N2 content in the steel plate is reduced to about 10ppm with low nitrogen steel. When this low nitrogen steel is manufactured, molten steel is decarburized to 0.01wt.% C content by RH degassing, the free oxygen content is reduced to <=10ppm with Al as a deoxidizer and the S content is reduced to <0.01wt.% by refining. A substance contg. a rare earth element such as La, Ce, Pr or Nd is then added to the resulting low carbon molten steel by 0.1-3.0kg (expressed in terms of the rare earth metal) per 1ton molten steel to remove nitrogen in the molten steel as the nitride of the rare earth element. Low nitrogen steel having <10ppm N2 content can be easily manufactured.
|
