910 



STEEL 



then treated in the bath of pig-iron, producing steel directly by the oxidising action of 

 the magnetic oxide in the carbon in the melted metal. The above process has since 

 been abandoned in favour of the rotatory furnace described under the article IRON. 



In a lecture delivered by Dr. C. Wm. Siemens before the Chemical Society, he thus 

 described his process of producing cast steel upon the open hearth of a regenerative 

 furnace. Two processes are employed at the Landore works : the Siemens-Martin pro- 

 cess, which consists, as already stated, in dissolving scrap-metal or steel in a bath of 

 pig-metal, to which spiegeleisen is finally added ; and the ore-reducing process, in which 

 pig-metal and ore in a more or less reduced condition is employed. 



The process chiefly employed at the Landore works consists of introducing on the 

 bed of an intensely -heated regenerative gas-furnace, as shown in figs. 1911 and 1912, 

 about 6 tons of pig-metal, which may be No. 3 or 4 haematite pig. When a fluid-bath 

 has been formed, oxide of iron, which should by preference have been smelted before- 

 hand with such proportions of ]jme or other fluxing materials as to form with the 

 silica in the ore and in the pig-metal, a convenient slag, is added ; or natural ores may 

 be used in their raw condition if they contain lime and manganese, as for example, 



the African Mokta ore. When about 30 cwts. of this ore have been dissolved (with 

 ebullition,) in the metallic bath, it is found that a sample taken from it contains only 

 about 1 per cent, of carbon : a point which can easily be detected by the eye of the 

 workman by a peculiar bright appearance of the sample when chilled in water and 

 broken by the hammer. 



Considerable difficulty was experienced to find a material to resist the excessive 

 heats necessary for carrying out this process : ordinary Dinas bricks, which are con- 

 sidered the most refractory material in general use, would be rapidly melted ; but a 

 brick specially prepared by crushing pure quartz-rock, and mixing it with no more 

 than 2 per cent, of quick-lime to give cohesion, answers well. The hearth of the fur- 

 nace is made of white sand with a small admixture of more fusible fine sand, which 

 mixture sets exceedingly hard at a steel melting-heat, and possesses the advantage of 

 combining into a solid mass with fresh materials introduced between the charges to 

 make up for wear and tear. The hearth and the furnace-roof, if of the materials just 

 specified, are very little attacked when the Siemens-Martin process is used, although 

 the heat must be sufficient to maintain wrought iron containing only a trace of carbon 

 in a perfectly fluid condition. If pig-metal and ore (fused together with the necessary 

 amount of flux) is used, the furnace also stands well, but the use of raw ore entails the 

 disadvantage of a more rapid destruction of the furnace ; even magnetic oxide of the 

 purest description necessitates the addition of raw lime for the formation of a fusible 

 slag, and the dust arising from the lime and sand through the decrepitation of the ore, 

 causes the silica-bricks to melt away rapidly, so that, after perhaps two months' usage, 



