| 摘要 |
<p>Molten steel, normally exposed to an air atmosphere, is protected against impurities by means of the provision of a gas containing a greater part of carbon dioxide in such amounts and so close to the surface that it gives rise to the dissociation of the carbon dioxide at a rate which provides a barrier or shield of gas which insulates (isolates) the steel from the surrounding atmosphere. This method may be applied in order to protect certain molten steels which are transferred from a casting ladle to a mould or from a casting ladle to a receiving container and from the latter to a continuous-casting mould. In a method in which a number of protection operations are carried out in series, the pressurized gas is extracted, in increments, from a storage container which contains a mass of liquid carbon dioxide in a superposed shrinkage (ullage) space which contains vapour. Each increment is finally expanded and dispersed at ambient temperature in order to form the shield. As each vapour increment is extracted from the container, it is replaced by means of the withdrawal of liquid carbon dioxide, its evaporation and its return to the shrinkage space.</p> |
