COLLKCTIOXS IN KfONOMK' ( ;i;< )I,<)(;Y A.M> MIlTAIJJ'K'fiY. Hf) 



iipriji lit position, and at tlu'sanu' tiuic tin* l>iast,iintlt'ra prcssnrfot JO to 

 ."io ponnds, is tnrncd on in ord«'r to Ui'cp tlio nu'tal fron> llowmj; into the 

 tnycres. Innncdialcly the silicon of tin* pi^^-iron oxidizes, and, as a re 

 sidt, tlu' •graphitic carbon of (ho pi;;-iron is clianj,nMl to (M)Md)incd cirbon. 

 In from .'{ to "> niinntes most of tin* silicon lias been oxidi/cd to silica, 

 wliicli unites with the oxides of iron and maa«;anese formed at the 

 same time, prodncinj; a slaj;. This is known as the lirst peiiod, and 

 is chaiacteri/,ed by a short feeble llann', with an abnmlant shower of 

 si)arks from the tlnoatot' the converter, and a pecubar roar; towards 

 the end of the ]>eiiod the llame ;;rows lonj,M'r, the sparks tinei- and less 

 abundant, and the second period bej^ins, in which the llame ;;iows mu(;h 

 longer, and a lar^je amount td' (!arbon is oxidized, while there is a re- 

 markable chan«ie in the sound from the thioat of the converter. This 

 period lasts from i to 1() minutes, and corresponds to the boilinj; perio«l 

 in the pnddlinj]^ ]>rocess; it fjradiially merges into the third periixl, in 

 which the roar increases, while the llame dinunishes, but grows very 

 bright : this continues from 3 too minutes, when the tlame an<l sonmls 

 almost entirely cease, anil the decarburizing is (H)mplete. At tliis 

 l>oint the converter must be turned down and the blast of air turned <tlf, 

 or the iron will l»e rai>idly oxidized and considerable loss incurred, 

 while the <inality of the metal may be conii)letely ruined. 



A certain amount of an alloy of iron and manganese, spiegeleisen, or 

 the licher ferroinauganese, high in carbon, is now a<lde«l to the con- 

 verter in order to introdiu'c the necessary amount of carbon to give the 

 grade of steel re<piired, and also to insure sounder castings by the in- 

 troduction of the manganese. Formerly it was tlie practice to turn the 

 eonvi'rter up again and continue the blow for a fi*w seconds, but now 

 the charge is allowed to stand a few moments for the i>roper mixing 

 of the si>iegel with the iron ;iiid the separation of the slag. The charge 

 has now been ctiinerted into steel, and the juocess has takt'ii IVom 10 

 to L'(» minntt's. 



Insteail of burning out all the (%irbon and then adding it again in the 

 Spiegel, the decarburizing might be stopped Just at lln^ point when the 

 carbon has reached the right percentage, and this was formerly doiu', 

 especially at some Swedish w<»rks, but it lias been found more pricti- 

 cable to Intin out ;ill the carbon possibh-, and then :idd the ie(|iiired 

 amount. 



The steel is now ponied into :i ladle. The converter is lepaiieil. if 

 necessary, and is then ready for a new charge, while the steel in the 

 ladle is cast into ingots. The ingots are removed as soon as they liav>^ 

 solidified and taken to the rolling mill, where the are rolh'd into rails. 



Tin' handling «i( such masses of metal re»|uires vt-ry powerful hydranliir 

 machinery, but this, as well as the blast, is all controlled by one man, 

 who stands on a platform in a commanding jiosition, and b> the iiiove- 

 nientof a few levers, conveniently placed to his hands, directs and con- 

 trols the whole process. 



0110— N(.. 11' 10 



