Steel and Iron 445 



the purpose, fuel oil, which is vaporized by a blast of air or by 

 steam, and producer gas made from bituminous coal. 



The furnace is kept in operation constantly. A charge which 

 is put into the basin consists of molten iron, scrap steel, lime- 

 stone, ferromanganese, and iron ore to furnish oxidizing and 

 other necessary materials. The checker chambers, which re- 

 main hot from the previous operation, pre-heat the air and gas 

 passing through them. After leaving the ports A A', the gas 

 and air combine in combustion. The flame produced is like that 

 of a blowpipe. It passes over the surface of the charge, oxidizing 

 it. The burned gases pass out through the opposite ports and 

 chambers B B', which they heat, and from which they are 

 conducted to the stack. After fifteen to twenty minutes the 

 air and gas currents, which are controlled by valves, are reversed, 

 entering now through ports B B' and leaving through A A'. 

 The temperature of the checkers rises with each reversal so 

 that the charge is subjected to a constantly rising temperature. 

 Reversals are made throughout the heat which continues until 

 tests show the desired composition of the product. The charge 

 may be kept molten at a given temperature as long as needed. 

 The control of the process is complete at every stage. 



Chemical changes in the process. The process is similar to 

 that of the Bessemer converter. The flame and oxidized ore 

 bring about the change of phosphorus into phosphoric acid, 

 which unites with lime to form lime phosphate. This is drawn 

 off in the slag. The sulfur combines, under the influence 

 of the heat and oxidizing materials, with manganese to form 

 manganese sulfid, and with lime to form lime sulfate, both of 

 which are removed in the slag. Silicon and carbon are oxidized 

 and pass off as gases or enter the slag. 



Duplex process. Where factories had already installed 

 Bessemer converters, it was found that both processes could be 

 advantageously employed. Molten metal may be first 

 " blown " in the Bessemer converter, then transferred to the 

 open-hearth furnace ; or the two processes may be operated 



