Basic principles of low carbon ferrochrome

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1. Low carbon ferrochromium is used to produce medium and low carbon structural steel, chromium steel, and alloy structural steel. Chromium steel is often used to make gears, gear shafts, etc. Chromium manganese silicon steel is often used to manufacture blades, valve plates, etc. of high-pressure fans.
2. Smelting methods There are two main smelting methods for low-carbon ferrochromium: high-carbon ferrochrome refining method and electrosilicothermal method.
The refining method of high-carbon ferrochromium is divided into refining carbon steel parts ferrochromium using chromium ore and refining high-carbon ferrochromium using oxygen. When using high-carbon ferrochromium from chromium ore concentrate, the refining slag has a larger viscosity and a higher melting point, and the smelting process temperature must be higher. Therefore, the power consumption is high, the furnace lining life is short, and the carbon content is not easy to reduce. Using oxygen to blow high-carbon ferrochrome has great advantages, such as high productivity, low cost, and high recovery rate. At present, the traditional production method is still the silicon thermal method. The electrosilicothermal method is to use the silicon in the silicon-chromium alloy to reduce the oxides of medium chromium and iron under the condition of making alkaline slag in the electric furnace, thereby producing medium and low carbon ferrochrome.
3. Oxygen blowing of medium and low carbon ferrochromium The equipment used for refining medium and low carbon ferrochromium by oxygen blowing is a converter, so it is called the converter method. According to different oxygen supply methods, oxygen blowing can be divided into four types: side blowing, top blowing, bottom blowing and top and bottom blowing. Our country adopts the top-blown converter method.
The oxygen blowing method is to blow oxygen directly into liquid high-carbon ferrochromium to decarburize it to produce carbon steel parts ferrochrome. The main elements in high-carbon ferrochrome are chromium, iron, silicon, and carbon, all of which can be oxidized. The main task of oxidation blowing high carbon ferrochromium is to decarburize and preserve chromium. When oxygen is blown into liquid high-carbon ferrochromium, since the content of chromium and iron accounts for more than 90% of the total alloy, chromium and iron are oxidized first, and then these oxides oxidize the silicon in the alloy. Due to the oxidation of chromium, iron, and silicon, the temperature of the molten pool increases rapidly, and the decarburization reaction develops rapidly. The higher the temperature, the more conducive to the decarburization reaction, and can inhibit the oxidation reaction of chromium, and the lower the carbon in the alloy can be reduced. .
Raw materials: The raw materials for low-carbon ferrochromium refining by oxygen top blowing are high-carbon ferrochromium, chromium ore, lime and silicon-chromium alloy. The high-carbon ferrochromium liquid in the converter requires a high temperature, usually between 1723 and 1873K. The chromium content of molten iron should be higher than 60%, the silicon content should not exceed 1.5%, and the sulfur content should be less than 0.036%. Chrome ore is used as a slag-making material. It is required that the SiO3 content in the chromium ore should be low, the MgO and Al2O3 content should be appropriately high, and its viscosity should not be too high. Lime is also used as a slag-making material, and its requirements are the same as those of the electrosilicothermal method. Silicon-chromium alloy is used to reduce high-chromium slag in the later stage of blowing. Generally, the silicon-chromium alloy powder sieved after crushing can be used.
4. Smelting low-carbon ferrochromium by electrosilicothermic method. laser cutting carbon fiber ferrochromium by electrosilicothermic method is carried out in a fixed three-phase electric arc furnace. Self-baking electrodes can be used, and the furnace lining is made of magnesia bricks (dry masonry). Short furnace lining life is an important problem in the production of medium and low carbon ferrochrome. Due to the high smelting temperature (up to 1650 degrees Celsius), the life of the furnace lining is generally shorter. The raw materials for smelting medium-low carbon ferrochrome include chromium ore, silicon-chromium alloy and lime. Chrome ore should be dry and pure lump ore or concentrate powder, in which the higher the Cr2O3 content, the better, and the lower the impurity content, the better. The phosphorus content in chrome ore should not be greater than 0.03%, and the particle size should be less than 60mm. The silicon-chromium alloy should be crushed, with a particle size less than 30mm and no slag. The lime should be freshly burned and its CaO content should be no less than 85%.