A wide range of intermediate rare earth alloy, including an intermediate iron-based rare earth alloy of silicon, aluminum rare earth alloy, magnesium alloy and the like. The rare earth intermediate alloys prepared by the thermal reduction method mainly include rare earth ferrosilicon alloys, rare earth silicon iron magnesium alloys, rare earth silicon iron lanthanum (calcium, titanium, etc.) alloys. At present, its output (based on rare earth oxides) accounts for about 1/3 to 1/4 of China's rare earth production.
In 1956, the Shanghai Institute of Metallurgy, Chinese Academy of Sciences, creatively researched the process of recovering rare earth from the iron-making blast furnace slag of Baotou Iron and Steel Co., Ltd. containing 45% to 6% of REO in the electric arc furnace with 75 ferrosilicon as the reducing agent. . Baotou Steel Rare Earth First Plant first adopted this process to start production of rare earth ferrosilicon alloy.
In 1966, the Baotou Rare Earth Research Institute of the Ministry of Metallurgy succeeded in the development of rare earth iron ore containing rare earths in order to meet the national demand for rare earth ferrosilicon alloys and break the view that the middle and lean iron ore into the blast furnace could not go straight and explode easily. low-grade rare earth concentrate pellets directly into the blast furnace iron to phosphorus removal, preparation REO> 10% enriched residue, and then the smelting process using rare earth ferrosilicon alloy of silicon thermal power, so that the production of the rare earth ferrosilicon alloy into a new At the stage, the cost of alloys is much lower than that of foreign similar products. This not only creates conditions for the large-scale popularization and application of rare earths in steel production in China, but also promotes the export of rare earth master alloys to Vietnam and the United States in the late 1960s. welcome.
In the 1980s, with the breakthrough of Baiyun Obo mining technology, the industrialized production of medium and high grade rare earth concentrates was successively launched, providing fine materials for the production of rare earth intermediate alloys. New intensified smelting technologies and marketable alloy varieties appeared constantly. The rare earth intermediate alloy industry has made great progress and development.
The development of theory and practice of metamorphism of cast iron, steel and special alloys, especially the promotion of rare earth treatment technology for ductile iron, petroleum pipelines and steels resistant to seawater and atmospheric corrosion, promotes the further development of rare earth intermediate alloy industry, using metal Both the thermal reduction method and the carbothermal reduction method successfully and efficiently produce a plurality of rare earth intermediate alloys. Especially in the 1990s, Zhang Chengxiang and Tu Yufeng from Northeastern University invented a one-step method for the production of rare earth silicide alloys in a submerged arc furnace, and successfully carried out industrial production in a submerged arc furnace with different capacities of 3600-6300 kVA.
Rare earth intermediate alloys are now widely used in steel, machine building and military industries. At present, most of the additives used in steel are the main functions in steel, such as deoxidation, desulfurization, neutralization and low-melting impurities, refining grains and improving the mechanical properties of steel. In cast iron, it is mainly used as a spheroidizing agent for ductile iron, a creeping agent for vermicular graphite iron, and an additive for alloy cast iron, which greatly improves the mechanical properties of various cast irons.
China's rare earth intermediate alloy industry has the characteristics of large output, variety, low cost and comprehensive utilization of products. Its raw materials, processes and application fields are unique in the world, and have attracted widespread attention from people at home and abroad.
China's rare earth resources are abundant. In addition to the light rare earth resources of Baotou rare earth minerals, there are also fluorocarbon strontium mines in Suining, Sichuan, heavy rare earth resources such as Jiangxi, and fluorocarbon strontium resources in Shandong Weishan Lake. They have been used for the production of intermediate alloys, which have created favorable conditions for China to participate in international competition.
This chapter mainly introduces the principle and process of producing rare earth ferrosilicon alloy by silicon thermal reduction method and carbothermal reduction method.
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