Bessemer (Bessemer Zhang Guohui1813-1898), also translated as Bessemer. British inventor and engineer, one of the inventors of converter steelmaking.
C, 1856, German engineer William Siemens laid the foundation for the structure of open hearth furnace with regenerator. 1864, French engineer Martin used a flame furnace with a regenerator to melt raw materials such as pig iron and scrap steel into molten steel with gas or heavy oil as fuel under the direct heating of combustion flame.
1, puddlingprocess process
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 open hearth furnace, except that there is no lower regenerator. The long flame formed after fuel combustion is sent into the furnace. Pig iron is heated by the reflection of the top of the furnace, and the bottom of the furnace is made of iron oxide. Due to the excess oxygen in the flame, there is a lot of oxygen at the bottom of the furnace, and the carbon and phosphorus in pig iron are oxidized and removed. The furnace temperature of Pudelin is only about 1400℃. After the carbon in pig iron is removed to a certain extent, the melting point exceeds the furnace temperature, and the metal is in a semi-solidified state. Manual stirring is needed to continue smelting. However, because the furnace bottom and slag contain iron oxide with a very high content of 470, 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 squeezed out and made into materials for use. Puddling process is the main production method before the appearance of modern steelmaking process, which has reached a considerable production scale. /kloc-in the middle of the 0/9th century, the railways laid by Pudelin Iron Art in Europe and America reached more than 70,000 kilometers. 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
Method for melting metal material into molten steel in graphite clay crucible. 1742 was first applied by British B.Huntsman, who cut carburized iron into small pieces and put them in a closed clay crucible and heated them outside. Iron continues to absorb carbon from graphite, melts into high carbon steel water, is cast into small ingots, and forged into the required shape. When steel is melted in the crucible, graphite carbon can also be used as a reducing agent, and the following reduction reactions occur:
Carbon+ferrous oxide = cobalt+iron
2C+SiO2=2CO+Si
Oxygen in steel can be removed, and various inclusions in molten steel can also be removed, so the quality of steel (tool steel) is superior to all kinds of metal materials at that time, and it can be used to manufacture tools for processing metal materials. Crucible method is the first method to produce molten steel in human history. But the output is small and the cost is high. 19 was invented at the end of the year, and gradually replaced its position. Only in some experiments, there are people who use crucibles 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 a converter with an acid lining to oxidize impurity elements and generate a large amount of heat, thereby smelting molten steel. Also known as acid bottom-blown converter steelmaking. /kloc-in the middle of the 0/9th century, European capitalist industries flourished. At that time, the existing ancient steelmaking methods, such as Pudelin method and crucible steelmaking method, could not meet the growing demand for steel in society. 1855, British H. Bessemer successfully tested the method of blowing air into molten iron to smelt molten steel, and obtained a patent in 1856. At the same time, American W. Kelly also successfully studied the method of blowing air into molten iron to make steel (Kelly air boiling method), and obtained the American patent in 1857. When Bessemer started the experiment, pig iron with low phosphorus, low sulfur and high manganese was used as raw material, which was initially successful. However, when other pig iron is used, the molten steel produced by smelting will have pores and hot cracks during solidification, which is difficult to use. 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 initiated the mass production of molten steel. High productivity, low cost, steel quality is better than semi-solid Pudelin iron, so it develops rapidly. During the 30 years from 1870 to 1908, Bessemer process became the main steelmaking method in the world. Figure 1 shows the general situation of Bessemer Steelmaking Plant in Sheffield, England. In the United States, Bessemer process also occupied a major position before 1908 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 for converter steelmaking, and the quality of its steel is worse than that of open hearth steel. Therefore, Bessemer steelmaking 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 power 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 high speed is still widely used in various modern oxygen converters.
4. Alkaline open hearth steelmaking
Open hearth operation technology The raw materials used in open hearth steelmaking are: ① pig iron or molten iron, scrap steel and other steel materials; (2) Oxidizers 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 additive. The process of open hearth steelmaking is usually divided into several steps, such as reheating, charging (iron ore, lime and scrap steel), heating, adding molten iron, melting, refining, deoxidation and tapping. Take the 300-ton heavy oil open hearth furnace operated by waste ore method as an example, and the operation time of each stage of steelmaking is shown in table. The specific gravity of slag is only about 1/2 of that of molten steel, and it floats on the surface of molten pool, between furnace gas and molten steel, and is the medium for heat and oxygen transfer from furnace gas to molten pool.