| 摘要 |
<p>A method of manufacturing a steel exhibiting the favourable properties of half-calmed steel. The heads of calmed steel ingots have a more or less pronounced pipe which leads to the dead head, the size of which can be reduced only by expensive means, such as feeding and/or reheating. In contrast, half-calmed steels give off, during their solidification in the ingot mould, quantities of gases which can compensate for the space which would be caused by a pipe at the head of the ingot, by the formation of a multitude of cavities or blowholes. Attempts have been made to adjust the quantities of gases given off during solidification by adding specific quantities of calming agents to the steel. However, it has proved imposssible to control the evolution of gases in a totally reproducible manner. The object of the invention is to propose a method of manufacturing a steel exhibiting the favourable properties of half-calmed steel, while avoiding the disadvantages normally inherent in half-calmed steel. This object is achieved by the method which provides for casting, in an ingot mould, a totally calmed steel and treating the said steel by allowing a gas, capable of creating a multitude of cavities within the body of the ingot, to act inside the ingot mould during or after casting. This gas is preferably a neutral gas or a reducing gas which is top-blown or bottom-blown into the still unsolidified metal. It is also possible to blow in vapours of metals or solid materials which give off gases at high temperatures. The result is an ingot which exhibits a skin of excellent quality and a uniform internal condition having a multitude of mini-cavities which are uniformly distributed through the body of the ingot.</p> |
