DEPHOSPHORIZATION OF IRON. 



209 



the ordinary refractory lining of the converter 

 of silicious materials with a basic lining. The 

 first successful blow, after considerable trou- 

 ble had been found in obtaining a good lining 

 by burning magnesian limestone in a kiln, 

 was made April 4, 18V9, the news of which 

 awakened the intensest interest of metallur- 

 gists all over the world. Thomas and Gil- 

 christ explained their invention in a paper 

 read at the next convention of the Iron and 

 Steel Institute. Massenez and Pink, of the 

 Hoerde Company, in Westphalia, and Brown, 

 Bayley, and Dixon, of Sheffield, were the next 

 to adopt the process. At first, charges of lime 

 and oxide of iron, varying from 15 to 25 per 

 cent, of the pig, were placed in the converter 

 before the molten metal was poured in. After- 

 ward the oxide of iron was discovered to be 

 superfluous. 



The material used in the lining of the old 

 converter, called ganister, is nearly pure silica, 

 which is an acid (SiaCX), being the oxide of 

 the metalloid silicon. When lime is roasted 

 with iron in the converter, the phosphorus is 

 removed ; but it is necessary, apparently, not 

 only that the lime should be properly mingled 

 and blown together with the metal, but that 

 the converter should be entirely lined with 

 lime or some alkali. The use of the acid lin- 

 ing would be fatal to the process, because the 

 silica and lime would eagerly combine and 

 form a kind of glass, which would go into the 

 slag, leaving the phosphorus as it was. The 

 silicic acid is the great enemy of the basic lin- 

 ing, causing the lining, and especially the bot- 

 tom, to rapidly alter and degenerate. After 

 many costly experiments, a practicable basic 

 lining was obtained by wetting and molding 

 magnesian limestone ground into powder, and 

 then burning the dolomite bricks thus made at 

 the highest attainable temperature. Another 

 mode of forming the lining is, to ram into 

 the converter hard-burned pulverized dolomite, 

 mixed with ten per cent, of coal-tar. The tu- 

 yeres used in lime-lined converters are either 

 of the ordinary fire-brick kind, or the lime- 

 bottoms are rammed around rods which form 

 tuyere-holes. The lime-bricks as they are 

 made are exceedingly expensive, and not al- 

 ways trustworthy, and yet are subject to rapid 

 and certain destruction. The dolomite bricks 

 are built up to form the lining with mortar ot 

 similar composition. The only material which 

 has produced satisfactory basic bricks so far 

 is magnesian limestone or dolomite. It was 

 hoped that the afterblow that is, the con- 

 tinuance of the blast for two or three min- 

 utes after the decarbonization has been com- 

 pletedcould be avoided, and the wear on 

 the bricks, which takes place chiefly at this 

 period, be greatly reduced ; but when the 

 chemistry of the process was better under- 

 stood through the revelations of the spectro- 

 scope, it was seen that the afterblow was the 

 necessary and characteristic condition of de- 

 phosphorization. The phosphorus at the high 

 VOL. xx. 14 A 



temperature of the Bessemer converter is 

 converted into phosphoric acid, which will 

 combine with the lime or other base only after 

 the carbon and silicon and a large proportion 

 of the sulphur have been eliminated. The 

 preservation of the basic lining depends large- 

 ly on shortening the period of the overblow as 

 much as possible. Yet in Cleveland it is found 

 necessary to continue it three or four minutes, 

 producing a most destructive wear and tear. 

 The corrosive action of the silicic acid is di- 

 rectly proportional to the amount of silicon 

 contained in the iron; and the pig which is 

 lowest in silicon can consequently be made in- 

 to steel by the basic process the most econo- 

 mically. According to A. L. Holley, iron is best 

 adapted for the basic process which contains 

 under 1 per cent, of silicon, 2 per cent, of 

 phosphorus, and from ^ to 2 per cent, of man- 

 ganese, which is useful as a heat-giver as well 

 as a valuable ingredient in steel. The ferro- 

 manganese or spiegeleisen is added to the 

 blown metal; and, before it is poured in, the 

 slag is run out of the converter, to prevent the 

 manganese from taking the phosphorus out of 

 the slag again, and carrying it back into the 

 iron. The basic process is, in other respects, 

 conducted precisely like the ordinary process, 

 except the afterblow. 



The absence of any indication when the 

 dephosphorization was completed, such as the 

 drop of the carbon-flame in the ordinary pro- 

 cess, necessitated the troublesome and time- 

 losing proceeding of taking out samples to test 

 during the afterblow. If the blast were con- 

 tinued too long, the quality of the product 

 would be impaired by oxygenation. The in- 

 convenient accumulation of slag and metal, 

 clogging the nose of the converter, while the 

 samples were being taken out, was only par- 

 tially avoided by reducing the size of the aper- 

 ture and lining the nose with fire-brick. With 

 increased experience it was possible to stop 

 blowing at the right stage by timing the blast, 

 without the necessity of sampling. The wear 

 of the lining was much more uniform after 

 this, as many as six hundred and thirty tons 

 of steel having been made in one lining with- 

 out repairs. J. Massenez has observed closely 

 the chemical changes which take place during 

 the basic process, in the works at Hoerde, in 

 Westphalia. The silicon is reduced to a mere 

 trace in about two minutes, a portion of the car- 

 bon burning out at the same time. While the 

 silicon is in combustion the phosphorus not only 

 is not attacked, but increases proportionately 

 to the bulk of the mass while the silicon and 

 carbon are being reduced. After the silicon 

 is expelled, the carbon commences to burn on 

 rapidly. The manganese oxidizes slowly and 

 regularly during the whole blow. The trace 

 of copper disappears at the commencement. 

 The sulphur-curve rises until the beginning of 

 the afterblow, and descends only slowly and 

 partially at its end. The phosphorus is ener- 

 getically attacked after decarbonization has 



