Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
Tham khảo tài liệu 'handbook of extractive metallurgy 1 part 9', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 310 Handbook of Extractive Metallurgy and electric steel processes and ceased operation after a few years. It was developed for melting scrap and was characterized by its great flexibility with respect to the proportions of pig iron and scrap used. The tank-shaped furnaces are heated by fossil fuels such as gas or oil burned in hot air. The regenerative air preheating invented by Siemens takes place in checker chambers that contain refractory bricks heated by the waste gas and are situated under the furnace. The combustion temperatures achieved enable steel scrap to be melted. The capacity of these furnaces is 50-10001. The use of air for the combustion leads to the production of large quantities of waste gas whose purification sometimes including desulfurization is difficult and expensive. Additional oxygen introduced through lances or burners tandem furnaces has been used to improve operation but this leads to severe erosion of the refractory furnace lining. The open hearth process has in general lost its importance as it cannot achieve either the output or flexibility of blowing processes. Ó.3.3.3 Production of Stainless Steels Although world steel production is subject to very severe fluctuations dictated by market conditions the average growth rate of stainless steels i.e. resistant to rust acid and heat between 1950 and 1985 was 6 . In 199Ó total output reached 1071. Special metallurgical processes have been developed for steels with a chromium content 12-28 and low carbon content 65 Figure 6.58 German-American design for a 250 t furnace for gas and oil firing 64 Figure 6.59 The Fe-C-Cr-O system. Temperature C----- - Figure 6.60 Free energy of oxidation of Cr p and c as a function of temperature. Production conditions are determined by the thermodynamic equilibria of the reactions of.oxygen with carbon and chromium Figures 6.59 6.60 . In the first process variation which is mainly used in western countries an electric furnace is used to melt scrap and .