468 



NATURE 



{Sept. 27, 1877 



sulpliur, and silicon, and that, if freed from its adherent slaj, it 

 furnishes a material superior in quality and comnercial \alue to 

 the ordinary iron of commerce. 



The practical objections to the direct process, as practised in 

 former days, and as still used to a limited extent in the United 

 States of America and in some European countries, are that — • 



1. Very rich ores only are applicable, of which about one-half 

 is converted into iron, the r^moinder being lost in forming slag. 



2. The fuel used is cliarcoal, of which between three and four 

 tons are used in producing one ton of hammered blooms. 



3. Expenditure of labour is great, beinij at the rate of thiity- 

 Ihree men, working twelve hours, in producing one ton of metal 

 (see Percy). Iron produced by direct process in the Catelon 

 forge is therefore expensive iron, and could not compete with 

 iron produced by modern processes except for special purposes, 

 such as furnishing melting material for the tool steel melter. 



But, it may be asked, could the advantages of the direct 

 process not be combined with those of modern appliances for the 

 production of pure and intense heats, and for dealing with 

 materials in large masses, without expenditure of manual labour, 

 and cannot chemistry help us to larger yields and the faculty of 

 using comparatively poor and impure ores ? 



A careful consideration of these questions led me to the con- 

 clusion, some years ago, that here was a promising field for the 

 experimental metallurgist, and that I possessed some advantage 

 over others in the use of the regenerative gas furnace as a means 

 of producing the requisite quality of heat without the use of 

 charcoal and blowing apparatus. I engaged, accordingly, upon 

 a series of experimental researches at my sample steel works, at 

 Birmingham, and, in 1S73, I had the honour of submitting the 

 first fiuits of these inquiries to the Iron and Steel Institute, in a 

 paper entitled " On the Manufacture of Iron and Steel by Direct 

 Process." Encouraged by the results I had then obtained, I 

 ventured with some others upon some larger applications, the 

 principal one of which has been one at Towcester, in 

 Northamptonshire. 



Viewed by the light of present experience, it would have 

 been wiser to have fixed upon another locality with fuel, skilled 

 labour, and better ores within easy reach ; but in extenuation of 

 the error committed, it may be urged that' the site was fixed by 

 force of circumstances rather than by selection, the chief tempta- 

 tion being an ample supply of small Northamptonshire ore at a 

 very low cost. It was, however, soon discovered that this ore, 

 although capable of producing iron of good quality, was too 

 poor and irregular in quality to yield commercial results unless it 

 was mixed with an equal weight of rich ore, such as pottery 

 mine, Spanish ore, or Rollscale, all of which, as well as the 

 fuel, are expensive at Towcester, owing to high rates of carriage. 

 It IS in crinsequence of these untoward circumstances that the 

 works at Towcester have not been completed by the addition of 

 roUmg mills, the intention being to transfer the special machinery 

 ultimately to existing ironworks when the process has been 

 sufficiently matured for that purpose. 



The Towcester Works were vi>i!ed, in the autumn of last year, 

 by two eminent met illurgists. Professors von Tunner, of Leoban, 

 and Akermmn, of Sweden, who have published the results of their 

 observations in separate reports ' The results noted down by Mr. 

 von Tunner are relerret to by our past-presidvint, Mr. I. Lowthian 

 Bell in hi~ paper on the " Separation of Carbon, &c.," which was 

 read in March l)St, and will be discussed at the Newcastle meet- 

 ing. The criti-i.-ms contained in these publications are conceived 

 in the fairest possible spirit, and form indeed a most valuable 

 record of the progress achieved up to that time, but they furnish 

 me with an inducement to break silence sooner than I had in- 

 tended, reg.irdrng the further progress which has been effected, 

 and the conclusions I am risposed to draw from past experience 

 regarding the direct process of the future. 



The lealing idea which (.uidcd me in these was to operate 

 upon such ndxture^ ol ore-, fluxe^, and reducing agents as would, 

 under the ii fluence of intense heat, resolve themselves forthwith 

 into metallic iron and a fluid cinder, differing es^eitially from the 

 methods pursued by Chenat, Guilt, Blair, and others, who pre- 

 pare spongy metal in the hrst place by a slow proce^s which is 

 condensed into malleable iron or steel by after-processes, but 

 assimilating to some extent to the process fir.-t proposed by Mr. 

 Wm. Clay. In n.y pai er of 1873 I described two moi-es of 

 effecting mv purpo-.c, the one by means of a stationary, and the 

 other by means ..( a rotative furnace chamber, the foiniei being 

 applicalde chiefly wheie compaiativcly rich ores are available, 

 and the latter for sucii poorer ores as o^cur near Towcester. 

 * Das Eisenhuttenwesen von L. Ritter von Tunner, Wien. 1870. 



At the Towcester Works three rotative furnaces have been 

 erected, two of them with working drums seven feet in diameter 

 and nine feet in length, and the third of smaller dimensions. 

 The gas flame both enters and passes away from the back end 

 of the furnace, leaving the front end available for the furnace 

 door, which is stationary. The ends of the furnace chamber are 

 lined with Bauxite bricks, and the circumference with ferrous 

 oxides, resulting from a mixture tif furnace cinder enriched with 

 roll scale or calcined blackband in lumps. About 30 cwt. of 

 ore mixed with about 9 cwt. of smiU coal having been charged 

 into the furnace, it is made to rotate slowly for about two and a 

 half hours, by which time the re^iuction ol the metal should be 

 completed, and a fluxed slag be formed of the earthy constituents 

 containing a considerable percentage of ferrous oxide. The slag 

 having been tappeif, the heat of the furnace and the speed of 

 rotation are incrca-e 1 to facilitate the formation of balls, which 

 are in due course taken and treated in the manner to be presently 

 described. 



These balls contain on an average seventy per cent, metallic 

 iron and thirty per cent, of cinder, and upon careful analysis it 

 is found that the particles of iri'ir, if entirely separated from the 

 slag, are pure metal, although the slag may contain as much as 

 six per cent, and more of phosphoric acid, and iioai one to two 

 per cent, of sulphur. In shingling those balls in the usual man- 

 ner the bulk ot the cinder is removed, but a sufficient residue 

 remains to impart to the fracture a dark appearance without a 

 sign of crystalline fracture. The metal shows in being worked 

 what appears to be red shortness, but what should be termed 

 slag shortness. In repiling and reheating this iron several times 

 this defective appearance is gradually removed, and crystalline 

 iron of great purity and toughness is produced, but a more ready 

 mode of treatment was suggested by Mr. Samuel Lloyd, one of 

 my co-directors in the Towcester Company, in reverting to the 

 ancient refinery or charcoal hearth. The balls as they came 

 from the rotator are placed under the shingling hammer and 

 beaten out into flat cakes not exceeding an inch in thickness. 

 These are cut by shears into pieces of suitable size and formed 

 into blooms of about 2 cwt. each, which are consolidated under 

 a shingling hammer and rolled into bars. 



The bars have been sold in Staffordshire and Sheffield at prices 

 varying from 7/. to 9/. per ton, being deemed equal to Swedish 

 bar as regards toughness and purity. 



It may therefore be asst-rted as a matter of fact that iron and 

 steel of very high quality may be produced from ores not supe- 

 rior than Cleveland ores by direct process, but the question 

 remains at what cost this conversion can be effected. The ex- 

 perimental works at Towcester aie, iinf irtunalely, not sufficiently 

 complete to funish more than the elements upon which the 

 question of cost may be deiermined, the principal reasons being 

 that the one reheating furnace and a 30 cwt. hammer at the 

 works are not sufficient to deal with the iron produced by the 

 three rotators, that the iron has to be finished at a rolling-mill 

 elsewhere, and that transports weigh heavily upon the cost of 

 production. The principal factor in the calculation of cost is 

 unquestionably the rotator. [A table furnishes the working 

 result of eighteen consecutive charges as taken from the charge- 

 book.] The mixture of ore consisted for each charge ol 12 cwt. 

 of Towcester ore (containing about 38 per cent, metallic iron) 

 mixed with 8 cwt. of calcined Great Fenton ore, i cwt. of tap 

 cinder, I cwt. of limestone, and 6J cwt. of small coal. The 

 time occupied for each charge was three hours fifiy-seven minutes, 

 or say four hours, and the yield of hammered blooms was on an 

 average 6 cwt. 2qrs. 13 lbs., whereas the metal contained in each 

 charge amounted (by estimate) to 9 cwt., showing a loss of 25 

 per cwt. Tnis loss is, however, partially recovered in using a 

 portion of the cinder again in succeeding charges, but the pro- 

 portion of cinder that may be used again with impunity depends 

 upon the amount of impurities, namely, ol phosphorus, sulphur, 

 and alumina Contained m the ore. The coal used in the pro- 

 ducers amounted to two tons per ton of hammered blooms 

 produced, and in pricing the materials used and labour enga"cd 

 upon the work, the table — prepared by the manager at the 

 works — gives 3/. Sj. as the cost per ton of hammered bloon.s. 

 To this must be added for re|iairs and general expenses, and the 

 cost of rolling the hammered blooms into bars, which in the case 

 of Towcester practice are very heavy, but of which an experienced 

 iron-master would form his own estimate. The cost of working 

 the metal in the hollow fires is also not included, and this may 

 be taken to add Irom 25J. to 30J. to the ton. The refined iron 

 so produced will, therefore, cost from 5/. 5^. to 5/. lOs. per ton. 



Other tables give tlie analysis of irons produced from various 



