908 STEEL 



disappearance may be accounted for by the diminution in the amount of the metal 

 volatilised until the quantity present in the flame is reduced below that necessary to 

 produce them, it having been found that for the detection of manganese by the spectro- 

 scope much larger quantities must be employed than are sufficient to produce the 

 ordinary reaction with soda on platinum-foil before the blowpipe. 



Another indication of the progress of the operation is that afforded by the character 

 of the slag. This has been employed in Austria and Sweden. An iron rod is inserted 

 into the converter, and when brought out a portion of the slag adheres to the point. 

 So long as any carbon remains unconsumed a peculiar brownish tint is observed ; but 

 as soon as the point of total decarbonisation is reached, the slag assumes a dead black 

 colour, with a peculiar metallic lustre, characteristic of the presence of protoxide of 

 iron, in considerable quantity. This test is said to be capable of great precision in the 

 hands of experienced workmen. 



The largest series of Bessemer converters hitherto erected are those at Barrow-in- 

 Furness. They are arranged in two groups, of which one has four converters, taking 

 T^-ton charges, and the other a similar number of a smaller size, holding 6 tons each. 

 The former are 9 feet in greatest diameter, and 14|- feet high. In all cases the pro- 

 portion occupied by the melted metal is very small as compared with the entire 

 capacity of the converter, a large empty space being required in order to prevent the 

 ejection of the fluid contents when the boiling is at the highest point. 



In Sheffield the loss of weight on the pig-iron employed is about 15 per cent, in 

 addition to 7.per cent, in the reverberatory melting furnace, or 22 per cent, in all. 

 With 3-ton converters the lining has to be renewed after blowing 250 tons ; but the 

 tuyeres wear out much quicker, and must be replaced after making 10 tons, that is, 

 after every third or fourth operation. 



The number of charges made daily is not more than four for each converter, as 

 although the actual blowing does not require more than fifteen or twenty minutes, a 

 considerable time is required for .the accessory operations of melting the pig-iron, the 

 solidification and removal of the castings, and the arrangements of the moulds. 



The ingots, when drawn from the moulds, like those obtained from steel melted in 

 crucibles, are always more or less unsound, and require to be compacted by hammer- 

 ing. For this purpose, they are raised to a bright red heat in a reheating furnace, 

 care being taken to keep the hearth filled with smoking flamo in order to prevent the 

 carbon from burning away. They are then hammered, and at a second heat swaged 

 clown to the form of the first groove of the rolling mill, when intended for bars or rails. 

 The length of the ingot is extended from 4 to 8 feet under the hammer. In rolling 

 rails two heats are required in addition. Spherical shots are cast a little larger than 

 the size required, and afterwards reduced to the proper figure and dimensions by a 

 steam-hammer with hemispherical swages. 



Most metals, it must be observed, on losing their fluidity, lose for the moment their 

 power of cohesion. Malleable iron, however, passes from the fluid into the pasty state, 

 in which it possesses the property of welding, which forms so well-known and remark- 

 able a peculiarity of that metal. Taking advantage of this fact, Mr. Bessemer tried 

 an experiment on manufacturing iron, direct from the fluid metal, into endless sheets, 

 in a manner analogous to that by which paper is now made of any length ; this has 

 not, however, been much used. 



Considerable discussion has arisen respecting the introduction of manganese in the 

 Bessemer steel, both .as to its value in producing a superior metal, and as to the dis- 

 covery of its value in the process. These questions were satisfactorily answered in 

 a communication read before the British Association at Birmingham in 1865, to which 

 those who are interested in the process are referred. 



Siemens-Martin Process. The production of cast steel in the reverberatory furnace, 

 by dissolving malleable scrap in molten cast iron according to the method proposed 

 by Heath, Price, and Nicholson, and others, has of late been brought to a considerable 

 degree of perfection by the use of the regenerative gas-furnace, which gives an intense 

 heat without requiring an oxidising or cutting draught; as is the case with ordinary 

 stack-draught furnaces. The process was first carried out on a working scale by Martin 

 of Sireuil, near Paris, who has given his name jointly with that of Siemens to the 

 process. The furnace is represented in longitudinal and transverse section in Jigs. 1911 

 and 1912. The regenerators A A and GG are placed below the bed in the usual manner, 

 the former being employed for heating air and the latter for gas. The bed B is made 

 of finely-ground quartz sand, consolidated by pressure, with strong heating, and is 

 supported on cast-iron plates, which are kept cool by a circulation of air. The surfai-o 

 of the bed is flat, with a slight inclination towards the top hole, which is placed below 

 the middle working-door, on the front of the furnace. The ladle, which has a 

 similar arrangement for running out the steel through a hole in the bottom, to 



