S/X WILLIAM SIEMENS, /.A'..s. 339 



!v._rarling steels in which the proportions of different mate- 

 rials miclu-.l tlu-ir limits on the one side or on the other. It had 

 been said that steel containing a considerable percentage of carbon, 

 i>- 1 per rent., was very soft. That might be partly owing to the 

 tempering, for if the steel had been slowly cooled it would be soft, 

 but it might also be owing to the manner in which the carbon was 

 combined. Carbon was not always chemically combined even in 

 steel. In the process of mixing spiegeleisen with the blown metal 

 at the last moment in the Bessemer process there was hardly time 

 to form a chemical combination, and hence metal might be pro- 

 duced which contained a considerable proportion of carbon, and 

 yi't was essentially soft metal because the carbon was not chemi- 

 cally combined. He had observed, in boring a large cylinder of 

 steel cast from metal of that description, that at one point the 

 boring tool went deeply into the metal, and at another point there 

 was a resistance as though the metal were hard. In such a case 

 no effect of temperature, of sudden cooling, was involved, because 

 of the particular form of the metal. The phenomena showed 

 clearly that steel was not always homogeneous unless special care 

 had been used to make the mixture perfect. Mr. Cowper had 

 attributed to manganese the quality of making the metal tough, 

 whereas carbon made it hard. That was not universally the case. 

 In the case of steel containing as much as 0'4 or 0*5 per cent, of 

 carbon, little manganese was desirable or necessary to make the 

 metal forge properly ; but in the case of very soft metal, and metal 

 containing phosphorus, the manganese was an essential condition. 

 For instance, 0*2 per cent, of phosphorus, which was about the 

 maximum amount admissible, necessitated about 0*4 per cent, of 

 manganese to make the metal at all workable and to prevent its 

 extreme brittleness when hard ; but in metal containing hardly 

 any carbon, less than 01 per cent, manganese was of the utmost 

 importance, and without it the metal could not be got to work or 

 stand against the grinding axle. The manganese seemed to bind 

 the particles of metal together, and to make it more homogeneous. 

 Mr. Riley had mentioned the difficulty of determining such a slight 

 amount of carbon by the ordinary colour test. No doubt the diffi- 

 culty was great, but Mr. Willis, of the Landore "Works, had intro- 

 duced a test for determining a very slight proportion of carbon, 

 sufficiently accurate for all practical purposes, by dissolving the 



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