STEEL.— Crucible.

854

considerable extent. Indeed, it is known that withmechanical puddling even very impure pig iron canbe purified to a far greater extent than was possibleby band-puddling, and that practically all the sul-phur and phosphorus can be eliminated.

Sample of the West Cumberland Company’s No. 1Hematite Pig made from Best Cumberland Ores :—

Iron...

r, , f Combined,....

Carbon - 1 Graphitic,’.

Silicon,.

Sulphur,.

_ *032

•331

Copper,.

100-000

Crucible Steel .—The art of melting steel in cruciblesis due to the industry and acumen of a memberof the Society of Friends , Benjamin Hunstjian, of

Handsworth, near Sheffield , who perfected the in-vention about the year 1740. It is stated on goodauthority that IIunstman was a mechanician of nomean order, and well versed in other kindred sub-jects. Some accounts state that he was a watch-maker, and that the trouble he met with from theirregularity of the metal of which watch springswere then made, induced him to look about for ameans of improving the steel. Whatever may haveinduced him to turn his attention to the subject,it is certain that he succeeded in a wonderful wayin building up a new industry under very unfavour-able circumstances; for before his time there wasneither furnace that would melt steel, crucible thatwould hold the molten metal, nor ingot moulds intowhich to pour it, and he succeeded in so perfectingthe manufacture as to leave it very much in thestate in which it is at present practised in many

Fig- 2. Pig. a.

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Pig. 4.

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Sheffield works. He carried on the manufactureas a secret process for a number of years, and IIunst-man’s steel became of world-wide reputation. It ispopularly believed that the secret of its manufacturewas gained by stealth, and the story is well told ina very able article on steel in the work entitled“ Useful Metals and their Alloys.”

The material formerly employed for crucible steelwas invariably the cemented steel just described.The bars were nicked and broken into small pieces,which were then placed in a crucible already heatedto a bright white heat in a small coke furnace. Nowit is not at all uncommon to use unconverted bariron, and also scrap of all kinds from the Bessemerprocess, but all carefully broken and assorted in a“mixing house” under skilled control; the dearerSwedish iron being used only for the very fineststeel.

The crucibles were formerly made from the highly

refractory Stourbridge clay alone, or mixed onlywith a small quantity of coke dust. Afterwardsmore local clays were found that answered equallywell, and for many years past still more refractory(although more tender) crucibles have come intoextensive use, made of a mixture of clay andplumbago. The apparatus for making crucibles isshown in Figs. 2, 3, and 4, and the general methodof manufacture will be easily understood. Thewell tempered clay is weighed out in lumps of thesize to make one pot. The lump is rolled up andthrown into the well-greased mould (Fig. 2), whichhas a close iron bottom with a small hole in it. Ahard wood plug (Fig. 3), of the shape of the interiorof the pot, having an iron pin in the bottom and aniron knob on top, is then driven into the clay untilthe pin centres itself in the hole of the false bottomof the mould. This keeps the plug in the centre,and spreads the clay evenly around to the shape of