Homogeneous
The Encyclopedia of Founding (1892)
Of the same kind or nature; having similar parts; or, of elements of the like nature; as, homogeneous particles, elements, or principles; homogeneous bodies. Honeycombing is the peculiar phenomena present in the upper portion of cast-steel ingots and steel castings, as well as those of brass and cast iron. In some instances this is supposed to be due to the liberation of imprisoned gases which, for the lack of pressure, remain within the mass of metal and form the honeycombing structure seen. Many schemes have been tried to prevent this, such as regulating the speed of pouring, temperature of metal for pouring with, covering the top with sand, molten slag, etc.; also by the introduction of some alloy, as aluminum; but none of these seem to be as effective for this purpose as the method pursued by Sir Joseph Whitworth, which consists of submitting the fluid metal to an enormous hydraulic pressure, which is maintained until the ingot has solidified. Some of the aluminum alloys have been credited with the ability to render steel castings perfectly sound, besides making the resultant steel tougher. Some claim that by using this alloy manganese can be discarded and time and fuel saved. See PRESSING FLUID STEEL; INGOTS; BLISTERS; BLOW-HOLES; ALUMINUM; SILICON. Hood is all that portion of the cupola shell which extends above the charging-hole. It is best to contract the hood in size somewhat, and carry it up sufficiently high to induce a good draught, which not only serves a good purpose in lighting up the first charges of fuel, but is a considerable auxiliary to the blower. See CUPOLA; LIGHTING THE CUPOLA.
What Has Changed in the Last Century
The 1892 entry hedges that honeycombing is "supposed to be due to the liberation of imprisoned gases" — a good guess, now settled: as steel freezes its solubility for hydrogen, nitrogen and oxygen collapses, and the last two also react with carbon to make carbon monoxide bubbles, while separate shrinkage forms the central pipe. The writer's tentative note that aluminium alloys "render steel castings perfectly sound" became standard practice: aluminium- and silicon-killed steel is routine, and since the 1950s vacuum degassing and argon stirring have removed the gas before pouring, while continuous casting largely eliminates the ingot top where the trouble collected. Sir Joseph Whitworth's method of holding fluid metal under enormous hydraulic pressure until solid, ranked here as the most effective cure, is a museum piece. The cupola hood survives in name, but on the few cupolas still running it is now an emission-capture stack feeding a baghouse rather than simply a draught-inducer, most iron foundries having moved to electric induction melting.
Written for this edition, 2026.