| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a heat insulting board which makes it possible obtain steel ingots having excellent fatigue characteristics by surely keeping the temperature of molten steel in a mold and inhibiting the aggregation of alumina-based inclusions to finely disperse them.SOLUTION: In a heat insulating board 1 which is used to keep the temperature of a steel ingot riser part 5 of a mold 14 at the time of charging molten steel 11 from below to produce steel ingots 4, the heat insulating board 1 has a two-layer structure comprising an upper layer part 3 and a lower layer part 2. The lower layer part 2 contains CaSi, FeO, and MnO, and the balance including at least one of SiO, C, and AlO. A content of Mt.CaSi (metal CaSi) in the CaSi contained in the lower layer part 2 is 40% (by mass, the same applies hereinafter) or more and 65% or less. Oxygen is contained in the FeO and MnOcontained in the lower layer part 2 in an amount of 4% or more and 13% or less. A content of CaSi having a particle size of 0.6 mm or more and 3.0 mm or less in the CaSi is 30% or more and 95% or less.</p> |
