B. Bessemer (1813-1898) also translated Bessemer. British inventor and engineer, one of the inventors of converter steelmaking
C. In 1856, German engineer William Siemens used regenerator to lay the foundation for the structure of open hearth furnace. In 1864, French engineer Martin used a flame furnace with regenerator to melt and refine raw materials such as pig iron and scrap steel into molten steel with coal gas or heavy oil as fuel under the direct heating of combustion flame.
1. Puddling process
The smelting method of large-scale production of wrought iron in Britain in the early days of industrial revolution. Also known as mixing method. The structure of Pudelin furnace is similar to that of the flat furnace, except that there is no lower regenerator. The long flame formed after fuel combustion is sent into the furnace, and pig iron is heated by the reflection of the top of the furnace, and the bottom of the furnace is built with iron oxides. Because of the excess oxygen in the flame and a large amount of oxygen in the bottom of the furnace, carbon and phosphorus in pig iron are removed by oxidation. However, the furnace temperature of Pudelin is only about 14℃. After the carbon in pig iron is removed to a certain extent, the melting point exceeds the furnace temperature, and the metal is semi-solidified. It is necessary to stir by manpower to continue smelting. However, because the furnace bottom and slag contain iron oxide with a very high content of 47, the carbon can be removed to a very low level and become wrought iron; Then, after repeated forging, the iron oxide slag in the wrought iron is extruded and made into materials for use. Pudelin method is the main production method before the appearance of modern steelmaking method, which once reached a considerable production scale. In the mid-19th century, the railways paved by Pudelin wrought iron in Europe and America reached more than 7, km. However, due to the fundamental weakness of semi-solid smelting-poor working conditions and poor quality of wrought iron, after the birth of Bessemer process, Pudelin process was quickly eliminated.
2. Crucible steelmaking method
A method of melting metal materials into molten steel in a graphite clay crucible. It was first applied by British B.Huntsman in 1742. He cut the carburized iron material into small pieces and put it in a closed clay crucible, and heated it outside the crucible. The iron material continued to absorb carbon in graphite and melted into high carbon steel water, which was cast into small ingots and forged into the required shape. When steel melts in the crucible, graphite carbon can also act as a reducing agent, and the following reduction reactions occur:
C+FeO = Co+Fe
2C+SiO _ 2 = 2C+Si
Oxygen in steel can be removed, and all kinds of inclusions can also be removed from liquid steel, so the quality of steel (tool steel) is better than all kinds of metal materials at that time, and it can be used to manufacture processed metals. Crucible method is the first method to produce liquid steel in human history. But the production is very small and the cost is high. After the invention of electric arc furnace steelmaking at the end of 19th century, it gradually took its place. Only in some experiments, there are people who use crucible to smelt molten steel for research, but this is no longer within the scope of steel production.
3. Bessemer converter steelmaking method
A converter steelmaking method in which air is blown into molten iron from the bottom of the converter with acid lining to oxidize impurity elements and generate a lot of heat, so as to smelt molten steel. Also known as acid bottom blowing converter steelmaking method. In the mid-19th century, Europe's capitalist industry flourished, and the existing ancient steelmaking methods, such as Pudelin method and crucible steelmaking method, could not meet the growing demand of society for steel. In 1855, H. Bessemer, an Englishman, successfully tested the method of blowing air into molten iron to smelt liquid steel, and obtained a patent in 1856. At the same time, American W. Kelly also studied the successful method of blowing air into molten iron to make steel (Kelly's air boiling process), and obtained the American patent in 1857. When Bessemer started the experiment, it happened that pig iron with low phosphorus, low sulfur and high manganese was used as raw material, and it was initially successful. However, when using other pig iron, the molten steel produced by smelting will have pores and hot cracks during solidification, so it is difficult to use. In 1856, British R. Mushet added mirror iron (an alloy containing manganese) to molten steel, which overcame the above difficulties, promoted the development of Bessemer process, and pioneered the mass production of liquid steel. It has high productivity and low cost, and the steel quality is better than that of semi-solid Pudelin iron, so it has developed rapidly. From 187 to 198, Bessemer process became the main steelmaking method in the world. Fig. 1 is an overview of Bessemer's steelmaking plant in Sheffield, England. In the United States, Bessemer process also occupied a major position before 198 until the rise of open hearth steelmaking. With the depletion of low-phosphorus iron ore, the steel scrap accumulated gradually in the world can not be used in Bessemer steelmaking, and the quality of its steel is worse than that of open-hearth steel. Therefore, Bessemer process gradually declined and was replaced by open hearth steelmaking. Although Bessemer steelmaking has disappeared now, it is recognized as the beginning of modern steelmaking. It skillfully uses the dynamic action of blast to make metal, slag and air in a highly emulsified dispersion state, and the principle that metallurgical reaction can be carried out at a high speed is still widely used in various modern oxygen converters.
4. Alkaline open hearth steelmaking
Open hearth operation process The raw materials used for open hearth steelmaking are: ① iron and steel materials such as pig iron or molten iron and scrap steel; (2) oxidants such as iron ore, industrial pure oxygen and artificial rich ore; ③ Slagging agents such as lime (or limestone), fluorite, bauxite, etc. (4) deoxidizer and alloy additives. The process of open hearth steelmaking is usually divided into several steps, such as furnace replenishment, charging (iron ore, lime and scrap steel), heating, adding molten iron, melting, refining, deoxidation and tapping. Take the 3-ton heavy oil open hearth furnace operated by scrap ore method as an example, the operation time of each stage of steel smelting is shown in the table. The role of slag The specific gravity of slag is only about 1/2 of that of molten steel. It floats on the surface of molten pool, between furnace gas and molten steel, and is the medium for heat transfer and oxygen transfer from furnace gas to molten pool.