STEEL. 



587 



crucibles are emptied into one large ladle. Krupp 

 casts ingots weighing 20 tons, using 70-lb. crucibles, 

 the mixture in the crucibles being puddled steel, | 

 wrought iron, and carbonaceous matter. The melt- ' 

 ing hole or furnace is a rectangular cavity about 2 

 feet square and 3 feet deep, lined with tire-brick, 

 with the top on a level with the floor, and the grate 

 bars and ash-pit readily accessible from below, with , 

 a square fire-tile for a cover. A short rectangular 

 flue is below, communicating with the chimney. A 

 number of such furnaces are arranged in parallel 

 lines, with spaces between for moulds. The cruci- 

 bles are made of a mixture of refractory clay and coke 

 dust and are 16 to 18 inches high, and 6 to 7 inches 

 in diameter. Two crucibles are usually put in a j 

 furnace with charges from 35 to 80 Ibs. The cruci- 1 

 bis is annealed by heating to redness in an open I 

 fire, and is then put in the furnace, and the charge 

 of blister steel or such mixture as may be desired, 

 the cover is put on, and the full heat of the furnace 

 kept up for four or five hours. To tell when the charge 

 has been thoroughly fused the cover is taken off 

 and the inside felt with a rod, and when fused it is 

 left at rest for a time depending upon the desired 

 temper. Tlie slag is skimmed from the surface and 

 the crucible lifted out by a pair of tongs and the ; 

 contents poured into a cast-iron mould, the mouth ; 

 of the mould when full being covered by a shovelful 

 of sand or a plate of sheet iron. The fuel consumed 

 is from three to four times the weight of metal pro- [ 

 duced. The fractured surfaces of the softer crucible \ 

 tteel ingots are bright and finely granular ; the 

 harder varieties exhibit distinct crystalline plates ar- 

 ranged in parallel bands. The ingots are nearly 

 always unsound, and the vesicular cavities can only ' 

 be removed by reheating and hammering at a low ', 

 temperature. 



Mnshet was granted a patent in England, in 1800, 

 for a process of manufacturing cast steel by firing 

 malleable iron in crucibles with carbonaceous mat- 

 ter, and in 1839 a patent was granted William Vick- 

 ers for the production of cast steel by melting 100 

 parts of iron borings witli 3 parts of black oxide of 

 manganese and 3 parts of ground charcoal. 



Caxe-hrirUeniny is a rapid process of cementation 

 by which the surface of wrought iron is converted 

 into steel. The piece to be case-hardened is em- 

 bedded in animal charcoal in a chest, and this is 

 placed for a short time in a smith's forge or a fur- 

 nace, and whon taken from the fire the object is 

 hardened by heating it to redness and plunging it 

 while still red hot into cold water. Small articles ! 

 may be so hardened externally as to resist a file, by j 

 sprinkling a little ferrocyanide of potassium on the 

 surfaces while red hot. "As soon as the powder has 

 disappeared the article is quenched in cold water. 



Instead of producing the steel by causing a cer- 

 tain amount of carbon to combine with wrought iron, | 

 carbon may be taken from the cast iron. The first 

 way that this was done was in the open hearth, ; 

 though improved methods have about done away 

 with this process ; but the term open-hearth steel is 

 still used to distinguish the product of the Siemens- 

 Martin furnace. The hearth is filled with burning 

 charcoal and a number of plates or slabs of lamellar 

 cast iron are melted in the blast of the tuyere, a 

 quantity of rich slag and iron scale being added to i 

 assist in the oxidation of the carbon. About thirty j 

 cubic feet of charcoal are used per cwt. of steel pro- ; 

 duced. 



Puddled steel was prodiiced in Carinthia as early 

 as 1835, and by 1845 it had become a staple product. 

 There is but little difference between puddling for j 

 steel and puddling for iron (see IRON), except that in 

 the latter case the decarbonization is more thor- 

 oughly effected. The crude irons that are best for 

 this purpose are those that are rich in carbon and ; 



manganese, so that spiegeleisens mixed with mot- 

 tled pigs are very good. The furnace bed is usually 

 smaller than in the iron furnace, to command a 

 higher temperature with the same-sized chimney 

 and fire-place. The charge is so distributed in 

 small fragments that it will all become fused about 

 the same time. The charge is from 3 to 3^ cwts. 

 This must be perfectly fused and covered with, a 

 stratum of liquid slag to regulate the oxidation of 

 the carbon. The melting down, stirring, or rabbling 

 is done at a higher temperature than with the iron 

 puddling and occupies usually from 40 to 50 min- 

 utes ; the steel balls are formed, however, at a lower 

 temperature than those of iron, and at this stage the 

 furnace should be filled with smoke to produce a 

 neutral or non-oxidizing atmosphere by closing the 

 damper. The appearance of the particles of the 

 metal brought above the slag by the stirring tells the 

 progress of the operation and the nature of the pro- 

 duct. When brightly granular it indicates satis- 

 factory progress and the production of steel of fine 

 grain and good quality. When flaky and coarsely 

 granular the steel is likely to be coarse in texture 

 and imperfectly refined. The shingling of the balls 

 is conducted at a lower temperature than with iron, 

 and when not taken immediately to the hammer are 

 rolled in slag to prevent oxidation. The time re- 

 quired under ordinary circumstances to work off a 

 heat of iron and steel will be as follows : 



Iron. Steel. 



Melting down 30 to 40 minutes. 40 to 50 minutes. 



Stirring 30" 35 " 45" 50 



Boiling and fusing... 25 " 30 " 20 " 25 " 



Balling 10 " 10 



Total 95 to 115 



115 to 135 



From 1800 to 2000 Ibs. of shingled steel balls can 

 be obtained from one furnace in 12 hours, in from 

 six to seven charges. In puddling steel, from 30 to 

 35 per cent, more coal will be used than the weight 

 of steel produced. The puddled balls when under 

 the hammer emit a blue flame, due to the com- 

 bustion of carbonic oxide. To draw into bars, the 

 blooms must be reheated before being put under 

 the hammer, or into the rolls. 



Numerous attempts have been made to produce 

 steel cheaply, and to Sir Henry Bessemer is due the 

 credit of discovering a quick way to convert pig-iron 

 into steel. This process was first made public by 

 him at the Cheltenham meeting of the British Asso- 

 ciation in 1856. This is a very simple process, and 

 consists in charging a quantity of about five tons of 

 melted pig-iron into a furnace shaped like a ginger- 

 ale bottle mounted on trunnions, having an open 

 top, and a bottom perforated by a number of holes, 

 through which air is forced in small jets by a 

 powerful blowing-engine. The blast of air, forced 

 up through the molten metal, effects the rapid oxi- 

 dation and consequent combustion of the carbon, sil- 

 icon, and other foreign substances. A very high tem- 

 perature is produced, sufficient to keep liquid the 

 resulting decarburized iron, and if the blast be kept 

 up after the carbon is all burnt out the iron itself 

 will be burnt ; so, before this point is reached, the 

 blast is stopped, and a charge of spiegeleisen con- 

 taining the necessary amount of carbon is intro- 

 duced. Pig-iron of exceptional purity must be \ised, 

 and it should be free from sulphur, phosphorus, and 

 copper. The spiegeleisen is an alloy of carburized 

 iron and manganese. This, containing about 5 pel- 

 cent, of carbon and from 10 to 25 per cent, of man- 

 ganese, is put in to replace the carbon that has been 

 burnt away, and sufficient to give the required 

 proportion of carbon in the finished metal. The 

 'converter consists of a shell of wrought iron, 

 suspended by means of a wrought-iron hoop, B, 

 carrying trunnions, C, supported by cast-iron stand- 



