ON THE THERMAL EFFECT OF HOT AND COLD METAL PROCESS IN OPEN-HEARTH FURNACE.

Abstract

As Asano Zosen has blown down his unique blast furnace about 3 months for the timely repair last year, his steel work has been compelled to adopt, during this interval, the cold metal process instead of the conventional hot metal one.
The experiences with cold metal have proved, contrary to our expectations, so favorable, for cold one, that the preoccupation, which prevailed there up to that time, the hot metal process should surpass the cold one exceedingly, has faded.
Why not the hot metal process so superior to cold one, as considered generally, or as calculated. only thermally? The author found, after his several experiments, the answers.
Primary the hot metal process is less of cold materials than the cold metal process just by the amount of its molten pig. The decrease of cold materials charged in the furnace means directly the drop of the thermal efficiency of the furnace. (second experiment)
Secondary the cold materials below the surface of molten pig form one pasty huge block together with molten pig, which sticks all over the hearth bottom of the furnace, and this sticky block becomes thermally inactive zone (first experiment)
Therefore the thermal superiority of the hot metal process to that of cold metal ought to be the surplus of the advantage of heat amount brought from the outside of furnace by molten pig over the disadvantage caused by the forgoing two reasons. This is why not the hot metal process so advantageous as considered or calculated on desk.
Further the author assumed that the thermal efficiency should be proportional to the surface area of the heap which form the cold materials in the furnace, and found that the inductions derived from this assumption go well with practice.