864 STEEL.— Bessemer
moment the exact charge of iron can be poured intothe converter. This is a very useful addition to theordinary Bessemer plant, as it saves much loss oftime, and insures greater regularity in the weight ofthe charge. In America the channels for the pigiron, or “runners,” are made of iron grouted withclay wash, and are much steeper than in the usualEnglish practice. This saves scrap, and gets the ironmore quickly into the vessels.
Convertors .-—These are pear-shaped vessels ofboiler plate, generally about 8 feet diameter by 15high, carried on trunnions, and capable of beingturned up or down by a strong rack and pinionwheel, the rack being fixed to the end of a pistonrod working into a hydraulic cylinder. The con-vertors are lined with gauister, which is a siliceousrock of a peculiar nature. It appears to have beendeposited in shallow seas just after the millstonegrit, and before the permanent land surfaceswere formed upon which the bulk of the coal-measure plants grew. Professor Hull has endea-voured to identify this bed over a very large area,and there is little doubt that it will ultimately befound in many districts in which at present it issupposed to be absent. It occurs very largely inthe Yorkshire coal-field, and also in Lancashire ,Shropshire , South Wales, and has lately been dis-covered in the Newcastle coal-field; but the finestquality of ganister stone is found around Sheffield,at Penistone and other places. It there forms theunderclay of a thin coal seam, and is very largelyworked, particularly by Mr. LOWOOD, for exportationto all parts of England, and even to Austria andRussia . The following analysis will show its chemi-cal composition:—
ANALYSIS OF GANISTER STONE.
99-93
Analysis is, however, only a partial guide to thevalue of a material of this kind, for it is found thatthe peculiar value of this Sheffield ganister dependsmore upon its physical characters than its chemicalcomposition. It appears to have been formed bythe aggregation of extremely fine particles (producedfrom the wearing away of quartz rocks) of sili-ceous matter with a little alumina, which havethen been subject to great pressure. It has aglassy or waxy fracture, quite different from allsandstones, and is extremely hard and tough. Itcontains numerous remains of plants, and oftenlarge masses of pyrites. It is not only highlyrefractory, but possesses the valuable quality ofbinding together like clay when ground, fine andmoistened. Sandstones, under these circumstances,are crumbly. It is the joint possession of thesetwo properties that renders ganister so valuable forlining Bessemer convertors, cupolas, &c.
In lining the convertors a core of the shape ofthe interior is placed inside the casing, leaving anannular space, into which the ground ganister is
Plant. Convertors.
rammed hard. To facilitate this work the con-verters are made in two or more parts, which arefirst rammed up with ganister, and then joinedtogether by bolts and nuts. After making good thejoints and inserting the bottom plug with its twyers,a small fire is lighted to dry it slightly, and then thevessel is half filled with coke and the blast kept ongently for about twelve hours. At the end of thistime some rock salt is thrown in to assist in glazingthe lining, and the vessel is then ready for use.With careful repairs at the end of each week onelining has lasted fifteen months of constant work,during which time about 15,000 tons of steel wouldbe made in the vessel. The bottom of the vessel inwhich the twyers are set wears out very rapidly,lasting only on an average from eight to ten blows,and therefore requires to be constantly renewed.Formerly this was done by leaving the cast-ironframe in its place in the blast box, fixing the twyersin their places, and then ramming the semiplasticganister around them from the inside of the vessel.This necessitated cooling down the vessel for eachnew bottom, and caused great delay, much wearand tear, and considerable expense in reheatingthe vessel again. Hence Holley designed thearrangement by which the bottom is made inde-pendently, dried in a stove, lifted into its place inthe vessel, and the joint between it and the oldlining made good from the outside by rammingganister into the space. This plan answers admir-ably, and is used universally in America , but hasnever been fairly tried at any works in England,except the West Cumberland Iron and SteelCompany’s. At these works it has been in usefor the last four years with very satisfactoryresults. Many attempts were made in England toinsert a dry bottom in its place, and fill up the spacebetween it and the vessel lining from the inside, bypouring into it a thin wash of ganister, or “slurry,”as the workmen term it. For some time the planfailed to answer, but now it succeeds fairly well, andis in pretty general use in England. It has the dis-advantage of being less secure than Holley’s plan,and cools the vessel more. The plugs are, however,generally smaller, and a trifle more handy, thanHolley’s; but this is a matter of no consequencewhen proper facilities are provided for dealing withthe latter. The twyers for carrying blast into thevessel are cylindrical plugs, of a mixture of three-fourths fire-clay, one-fourth ganister, perforatedwith a number of small holes about three-sixteenthsdiameter. The size of twyer, number per bottom,and number of holes, differ much in various works.In England the twyers have generally about thirteenholes, are from 18 to 22 inches long, 5 to 7 inchesdiameter at small end, and 6 to 8 inches at large end.From thirteen to sixteen are used in each bottom.They wear very irregularly; but a great deal dependsupon the pressure of blast employed, and the columnof metal which is worked upon them. It is verydesirable to keep the pressure of blast up to 25 oreven 30 lbs. per square inch. This keeps the metalout of the twyers and saves them much, for it is