STEEL.— Crucible.
856
melted; easy work being preferred for the thirdrounds.
“Abroad, at any rate in the large German worksI have seen, the practice is to use four pots in eachmelting hole, these being of inferior quality andthrown away after each round. This, however,sacrifices the heat due to getting the pot hot andready for work, which makes an hour differencebetween the first and second rounds.
“The consumption of fuel may be taken at about3jr tons of coke to the ton of mild steel, and from2j to 3 tons for other qualities; the general averagebeing about 3 tons per ton of steel.
“ Before altering some of our melting holes tothe Siemens system, we had 336 ordinary meltingholes, and when very busy we used about one-halfnight and day, so that we used more than 1000crucibles daily, each turning out about 1^ cwt. ofsteel, so that the daily production was about 75 tons.In altering to the Siemens system we get the samemelting power in the same space ; i.e., Siemens fur-naces for ninety-six pots occupy the same spaceas forty-eight old melting holes, which number wasour set for one chimney; but, as a matter of course,the Siemens furnaces ordinarily work night and day,so that the turn-out, if fully employed, would nowbe greater; the continuous work being found sodestructive to the ordinary furnaces that it couldonly be used exceptionally.”
The following particulars were supplied by Dr.Siemens, of the working of regenerative gas furnacesfor crucible steel melting:—
“ February 27, 1872.—The Monkbridge Iron Com-pany report that their consumption of coal per tonof steel melted amounts to 29 cwts., which includesthe gas necessary for annealing the pots.
“January 26, 1875—Messrs. Sanderson Brothersreport that their men make sixty-six hours and ahalf each set per week, work being commenced atone a.m. on Monday morning, and ceasing at from1 to 3.30 p.m. on Saturday. The men change shiftsevery twelve hours—viz., 6 a.m. and 6 p.m., thosecoming at 1 a.m. on Monday leaving at 6 a.m. thesame day: three casts of tool steel are made pertwelve hours, and sometimes seven per twenty-fourhours, according to the temper of the steel melted.
“ February 22,1866—Messrs. Verdie et Cie (Fir-miny, Loire) report to M. Boistel that they makeone cast in three and a half to four hours, say six intwenty-four hours. The pots last six casts, insteadof three as in the coke holes. The consumption ofcoal is about 3 tons per twenty-four hours, andthe steel melted 2'7 tons, equal to I’ll ton of coalper ton of steel melted.
“ Statement of the working of a regenerative gassteel-working furnace at the works of Messrs.Anderson, Cook, & Co., Pittsburg, Pa. , from7th to 14th November, 1869:—Twenty-four heats,averaging three hours and a quarter each, produced43,013 lbs. of steel, and consumed 26,448 lbs. ofcoal, or 348 bushels (of 76 lbs. each). Total cost offuel, 348 bushels at 3 cents = 10-44 dols.
“ In the old furnaces at the same establishment, it
takes to melt the same weight of steel 5160 bushelsof selected coke at 10 cents, making the total costfor fuel = 516 dols. Thus the saving effected by thegas furnace, in fuel alone, amounts to 505-56 dols.on 43,013 lbs., or 19 tons English , or 26-50 dols. perton. The melting is done in plumbago pots.”
The general process of manipulation in makingcrucible steel may be described as follows:—Thecrucibles, as stated above, only last for two or threemeltings. They are carefully annealed and graduallyraised to a red heat, ready for the steel-inelter whenhe begins his day’s work. If coke fires are used thestands of fire-clay are placed upon the bars, the firelighted, and when this has burnt up two pots are placedside by side in the furnace with their lids on. Smallpieces of coke, about the size of a hen’s egg, are thenfilled into the furnace around the pots. When thefurnace and pots are at a good white heat the chargeof steel, which may be 60 lbs. to begin with, is putinto the pot thus:—The steel in small pieces is held ina small iron shovel by the assistant. The melter thenrapidly draws the cover (Fig. 9) off the furnace, lifts
Pig. 9.- iV-
the crucible lid, and places the iron funnel (Fig. 10) inthe pot, while the assistant shoots the pieces of metalgently down the funnel into the pot, where they arelevelled by an iron rod and the crucible cover puton. The other pot is served the same way, and thenthe coke-fire is made up, and the grate bars cleared ;more coke is put on from time to time until thecharge is melted, which generally takes from abouttwo to three hours. After the metal has all becomefluid, it is usual to allow it to stand molten in thepot, and keep the heat up for about half an hourto “dead melt” the steel, as the workmen term it.What this dead melting consists in is even yet some-what doubtful, but it is highly probable that Besse-mer’s explanation is correct as far as it goes. Whatis known is that if the metal be poured into a mould assoon as melted, it is very fiery, that is, gives off anumber of sparks while being poured, and producesan unsound or honeycombed ingot; while if themetal be kept molten in the crucible for some time,until the surface shows a brilliant and still face, andit is then poured, it runs quietly into the mouldand the ingot shrinks on cooling, the bulk of itbeing perfectly solid. The top portion is found tobe piped, or has a hole down the centre, but this isbroken off and remelted. Bessemer supposes thatwhen first melted the metal contains no silicon, butthat by keeping it molten the carbon of the metalreduces some of the sand that was put into thecrucible to fill up the hole left in the bottom duringthe process of manufacture, and that silicon is thusset free and alloys with the metal, producing thereby