| 摘要 |
PURPOSE:To distribute uniformly lead into a steel and to produce a homogeneous leaded free-cutting steel in the stage of adding lead by a bottom pouring ingot forming method from a pouring pipe for a molten steel by adjusting the relation between the length of a runner and the flow rate ofthe molten steel in the runner part. CONSTITUTION:The molten steel M poured from a ladle nozzle 1 into a pouring pipe 2 is admitted through a runner 3 and a mold nozzle 4 into a casting mold 5. Granular lead is added into the steel M in the upper part of the pipe 2 and while the lead particles are dispersed and melted into the steel M by the molten steel flow, the molten steel is fed into the mold 5 in the stage of producing a leaded free-cutting steel. The pouring speed of the molten steel is adjusted in this stage in such a way that the flow rate V(m/min) of the molten steel in the runner 3 and the length L(m) of the runner 3 satisfy the conditions expressed by V<=14L+16. The ground flaw defect owing to segregation of lead is thus almost thoroughly eliminated, by which the quality of the leaded free-cutting steel is made uniform and the yield is improved. |
