STEEL.—Bessemer Plant. Casting Ladles, &c.
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found that the wear of the twyers is due far moreto the following action than to mere fusion. Onturning up the vessel, if the blast is weak, some ofthe metal runs part way down the holes in thetwyers and there forms solid plugs, which cannot beblown out, but which gradually get oxidised in thetvvyer by the blast, the oxide so formed slaggingaway the siliceous material of the twyer; so that,looking into a vessel after a “ blow,” large blackholes will be seen in many of the twyers, oftentimesrendering it necessary to replace them before thebottom is worn out. The number of blows obtainedfrom one “bottom” varies much, in some worksaveraging only six, in others fourteen or fifteen:occasionally from twenty to thirty are obtained.The heavier the charge of metal, other things beingequal, the shorter the life of the bottom. The blastis brought through one of the trunnions of the vesselinto a box termed the blast-box, and the twyers arefitted into a cast-iron plate, forming the top part ofthis box. The box is closed at the bottom by awrought-iron disc, which is fixed to the box by boltsand cotters, the joint being made air-tight by a ringof spun yarn steeped in clay wash. This bottomplate is thus easily removed for examining thetwyers. The blast for the convertor is raised by astrong blowing engine, of a somewhat similar typeto those used for blast furnaces, but proportionatelystronger. The valves of the blast cylinders areusually of metal, and frequently of the piston type.
Casting Ladle. —When the steel has been made,it is poured into a large ladle, which is lined upwith strong loam. This is carried by its trunnions,which are placed pretty near the centre of gravityof the full ladle, upon the end of a strong wrought-iron crane jib, the jib being carried upon the topof a.hydraulic crane post. The top of this post istaper, and enters a corresponding cavity in a strongcast-iron centre-piece, to which the wrought-ironsides are bolted. A steel pin fixed into the top ofthe post enters a small steel cup in this casting, andcentres and takes the weight of the frame, &e.About a dozen small steel rollers, fixed in a circularframe, run around the crane post and between itand the centre casting, thus enabling the top toturn freely on the post. Thus one man is enabled,by means of simple gearing, to turn the crane topand ladle around the post. The ladle has a holein the bottom, and a small cast-iron ring is fastenedto the bottom of the ladle, from the outside, by acouple of studs and cotters. In this ring is placeda fire-brick seat, having a hole through the middleabout 1 inch to lj inch in diameter. In using aladle for the first time, the seat is carefully lutedup to the rest of the lining of the ladle; but as aseat only suffices for one cast, and the ladle liningmay last ten or more, a new seat is put into theonce-used ladle, thus:—The iron ring is taken off,and the new seat carefully fixed into it; ganister isthen plastered around the top part of the seat, andit is forced up through the hole in the ladle andcottered into its place. The hole in the seat isclosed by a plug on the end of a wrought-ironVOL. II.
stopper rod. The rod is covered by loam or bystringer bricks , made in a pipe-making machine.This protects the iron stopper rod from the heat ofthe steel. The stopper rod is fixed to a slide, whichworks up and down in a guide attached to the out-side of the ladle. By this moans the aperture atthe bottom of the ladle can be opened or shut atpleasure, the whole arrangement forming an ingeniousvalve. In England the stopper is set in its placeby forcibly bending the rod; but Holley has de-signed a neat arrangement for adjusting the stoppermechanically—Fig. 16 is a front elevation; Fig. 17 is
Fig. 16. Fig. 17.
a side elevation; C is rivetted to the ladle. Theswinging frame, a, that holds the stopper slide, b, ishinged at d. The pins, pp, are moved over thesetrunnions to hold them down in place when theframe is in use. When it is out of use the pins,pp, are slipped back, and the frame, A, and slide, b,are lifted bodily out and set into a fresh ladle. Thestopper is adjusted by the set screw, a a.
When the steel has been poured into the ladle,the slag floats on the top; and on opening thestopper a stream of clear steel is allowed to runinto the moulds.
The Moulds are usually of cast iron, and taperfrom bottom to top; so that when the steel hassolidified, the iron “ moulds ” or “ chills ” can belifted off, and the ingot of steel remains behind.The moulds stand upon a slab of cast iron, and avery rough joint between the mould and the ironslab or “ bottom plate,” upon which it stands, issufficient to prevent the steel running out. Atmany works the steel is now run ascensionally, asit is termed. A number of moulds are fixed upona bottom plate, in which are placed perforatedbricks, connecting each mould to a central runneror “ sprue.” The steel is teemed down the central“sprue,” and is distributed by the runner bricks toeach mould, gradually rising in each till full. Bythis means cleaner ingots are formed, and the mouldslast longer.
The movement of most of the apparatus of aBessemer pit is produced by hydraulic power. Thisis found to be so much more steady than steam,and the apparatus generally is so simple, that directdriven gearing has entirely given place to it.
Ingot Cranes. — The moulds, ingots, and ladles109