188 



STEEL. 



ards, D, one solid carrying a pinion, E, gearing into 

 a rack, F, worked by a small engine, fur turning tbe 

 converter to a horizontal position. Tbe other trun- 

 nion in hollow, and forms a passage for the blast. 

 The lining, A, ia the moat refractory material that can 



Fio. 1. Bessemer Converter. 



be obtained. It is made from fine-grain silicious 

 sandstone known as ganuister. It is finely ground, 

 and then sometimes mixed with powdered fire-brick, 

 then incorporated with a small quantity of water, 

 and then lightly rammed between the outside casing 

 of wrought-iron and an inside wooden corn, which 

 is afterward withdrawn. The bottom consists of a 

 plug of the same refractory material, with a number 

 of holes or tuyeres, T, T, opening below into an iron 

 box, G, which communicates with the hollow trun- 

 nion by means of a pipe, H, so that air can be blown 

 up through the molten mass in the converter. The 

 operation is as follows : 



The charge is melted in a cupola or rnn direct 

 from the blast furnace, and the converter, which has 

 been previously heated to redness by filling it with 

 ignited coal, is reversed to remove any unconsumed 



Fio. 2. Betnemer Converter. 



fuel, and then brought to a horizontal position (Fig. 2) 

 to receive the charge of molten metal, which is ran in 

 through an iron gutter lined with sand. The con- 

 verter is then slowly turned back into the vertical 

 position, the Must being at the. same time turned 

 on. The flame which first issues is yellowish red. 

 Graphitic carbon passes into the combined state; 

 the silicon becomes oxidized, and silicates of iron 

 and manganese are formed. This first stage, which 

 takes about five minutes, is followed by a ]>eriod of 

 violent boiling, during which the combined carbon 

 ii rapidly oxidized by the blast. Carbonic oxide be- 

 ing evolved in large quantities, the flame increases in 

 brilliancy, and showers of xparks and fragments of 

 burning iron are thrown off. This lasts for about 



seven minutes, when the intensity of the action be- 

 gins to diminish. Fewer s|. u,'iven off and 

 the flame acquires a bluish-violet tint, marking tho 

 commencement of the last stage. As soon as the 

 carbon is all consumed the Haunt ceases, being im- 

 mediately succeeded, however, by a (lame of while- 

 hot gas, principally nitrogen. As soon as it is seen 

 that tho carbon is about burnt out, the converter is 

 again turned back to a horizontal ]H>sition and the 

 spiegeleiseu run in from a furnace by means of a 

 sand- lined gutter. When very mild metal is m-eiie.l, 

 the tempering is done with ferro-manga- 

 nese, made hot and shovelled into tho 

 ladle while pouring. The steel is decant. -d 

 from the converter by turning the top 

 down and letting it run out into cast- 

 iron moulds open at both ends, and a lit- 

 tle larger at one end than the ot! 

 that the ingots can be easily turned from 

 them when cooL 



In the Bessemer process, as desciili. .1 

 above, it is necessary to employ pig-iron 

 containing a very minute quantity of 

 phorus, as but little of that element is 

 eliminated during conversion. This means 

 very costly and scarcer ores ; but steel can 

 now be made by the btigic method from 

 iron smelted from cheap ores, the pig to 

 be sufficiently free from sulphur, not to 

 contain more than one per cent, of silicon, whil 

 the phosphorus should not be less than '2 to 2i 

 per cent. This process is called the basic pro- 

 cess, to distinguish it from the aciil process of 

 Bessemer. The terms refer to tho lining of tho 

 converter, acid-signifying quartz or gaunister, and 

 basic lime and magnesia as existing in calcint d 

 dolomite. Tho chemical fact involve.! is that the re- 

 tention of phosphorus in the blown metal is ma- 

 terially influenced by the character of the slap, 

 which is a silicate of iron and manganese, and if re- 

 duced to a lower silicate by the addition of other 

 bases phosphorus can be removed by oxidation. 

 Lime is tised for dephosphorizing after tho carbon 

 of tho metal lias been oxidized. \Vhen the converter 

 is ready for charging it is made hot by a coke fire, 

 and a quantity of quick-limp, from one-seventh to 

 one-fifth of the weight of the charge of metal, is intro- 

 duced, mado as hot as possible. The metal is then 

 charged in tho usual way and the blow ing conducted 

 us already described. In about ten minutes tho car- 

 bon is burnt out and the dephosphorizing period 

 commences. This is maike.l by a great increase iu 

 the temperature of the bath and a thickening of tho 

 converter smoke from the burning of tho iron, the 

 flame showing peculiar bright patches which are 

 not seen in the old process. The length of the after- 

 blow is regulated by breaking small test-ingots, 

 which should show a close, silky fracture, entirely fron 

 from bright crystalline particles. When the desired 

 metal has been obtained, the converter is lipped to 

 run off the slag, after which tho metal is brought to 

 the final temper by the addition of the piopi r 

 amount of spiegel and ferro-manganese, the former 

 in the converter and tho latter in the ladle after 

 pouring. The slag must be removed, as a portion of 

 th<! phosphorus may be reabsorbed if left in contact 



with the metal. 



There are diverse opinions as to the relative values 

 i !r:nle by the acid and basic processes. The 

 latter, utilizing the cheap ores, is remarkable for its 

 purity and mildness, and this is likely to bring about 

 its use on a large scale in the construction of boilers, 

 ships, bridges, and other structures requiring tough- 

 ness. The basic process is used both with the Bes- 

 semer converter and the Siemens-Martin furnace or 

 open-hearth process. 



The grandest application of the Bessemer process 



