. Transactions . E MANUFACTURE OF STEEL CASTINGS. 123 is only true to a very limited extent, especially where the steel con-tains per cent, or more of silicon. Herein lies the cause of themany failures connected with the manufacture of steel manufacturers had been led to believe that it was only neces-sary to add a few pounds of ferro-silicon to their steel, and presto!all the castings would be solid. Practical experience has proved thefallacy of this idea. Blow-holes in steel which has been properly melted, and to whichhas been added sufficient ferro-silicon, are almost entir
. Transactions . E MANUFACTURE OF STEEL CASTINGS. 123 is only true to a very limited extent, especially where the steel con-tains per cent, or more of silicon. Herein lies the cause of themany failures connected with the manufacture of steel manufacturers had been led to believe that it was only neces-sary to add a few pounds of ferro-silicon to their steel, and presto!all the castings would be solid. Practical experience has proved thefallacy of this idea. Blow-holes in steel which has been properly melted, and to whichhas been added sufficient ferro-silicon, are almost entirely due to thehigh melting-point of low-carbon steel, or rather to the rapidity withwhich the metal chills. This is proved by the fact that the lowerends of castings which have been fed from the bottom by means ofa runner are always solid, while the blow-holes, when such exist,are always on top. Out of the thousands of castings we have made,I have never yet seen a single one with blow-holes where the gate Fig. Mould for Casting a Plain Roll. joined the casting. The metal does not remain fluid long enoughto allow the air and other gases, that are mechanically carried intothe mould, to escape. This is best illustrated by reference to the accompanying sketch,Fig. 1, which represents the manner of casting a plain roll. A isthe fountain-head or basin where the metal passes from the ladle intothe mould; By the rising-head; C, the point where the runner joins 124 THE MANUFACTURE OF STEEL CASTINGS. the roll; D, the point where the casting is liable to defects fromblow-holes. The reason for this is obvious. If water from a faucetpasses through a tube it carries the air along with it. If we couldinstantly congeal the water, the resulting ice would be full of it is with steel, only more so, since the molten metal is not nearlyas fluid as water. As a consequence of the metal meeting the rela-tively cold mould, by the time the metal reaches the top of themould it is very much l
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