Abstract: To reduce the thermal loss of molten steel which cannot be reduced from the refractory materials and surfaces of molten steel during the production, a new technique that radiationproof steel plates are welded on the exterior walls of conventional ladle and its lid for forming a cavity shell, was proposed. Based on the thermal insulation principle of vacuum, the relationship of vacuum pressure and temperature drop, combined thermal transfer and the optimum pressure inside chamber were investigated. The results showed that，newtype ladle is therefore better in thermal insulation than conventional ladle.  When the absolute pressure inside the chamber of the ladle and its lid is set to 50 Pa, the temperature drop of molten steel is a mere 8 K, while the steel is held with the combination of the conventional ladle and its lid, the temperature drop reaches 35 K. The chamber at 50－100 Pa will obtain a better effect in the actual production.

Key words: new-type ladle, vacuum chamber, pressure, thermal loss, temperature drop