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Low carbon ferrochrome Source: Inner Mongolia pusheng Iron& steel Co,.ltd

There are two main smelting methods of low-carbon ferrochromium (containing 0.15% ~ 0.50% carbon): high-carbon ferrochromium refining method and electro silicothermic method.

There are two methods of refining high carbon ferrochrome: refining high carbon ferrochrome with chrome ore and refining high carbon ferrochrome with oxygen. Using high-carbon ferrochrome concentrate, the refining slag has high viscosity and high melting point, and the smelting temperature must be high. Therefore, the power consumption is high, the service life of furnace lining is short, and the carbon content is not easy to reduce. Converting high carbon ferrochromium with oxygen has great advantages, such as high productivity, low cost and high recovery rate.

The traditional production method is electro silicothermic method. Electro silicothermic method is to reduce the oxides of chromium and iron with silicon in silicon chromium alloy under the condition of making alkaline slag in electric furnace, so as to prepare medium and low carbon ferrochromium.

Oxygen blowing low carbon ferrochrome

The equipment used in the production of low carbon ferrochrome by oxygen blowing is converter, so it is called converter method. According to the different way of oxygen supply, oxygen blowing can be divided into side blowing, top blowing, bottom blowing and top bottom blowing. The top blown converter method is adopted in China.

Oxygen blowing method is to blow oxygen directly into the liquid high carbon ferrochrome to decarbonize and make low carbon ferrochrome.

The main elements in high carbon ferrochrome are chromium, iron, silicon and carbon, which can be oxidized. The main task of oxidation and smelting of high carbon ferrochrome is to decarburize and preserve chromium. When oxygen is blown into liquid high carbon ferrochrome, chromium and iron make up more than 90% of the total alloy, so the 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 molten pool temperature increases rapidly, the rapid development of decarbonization reaction, the higher the temperature, the more conducive to decarbonization reaction, and can inhibit the oxidation of chromium, the carbon in the alloy can drop lower.

The raw materials for oxygen top blowing refining of medium and low carbon ferrochrome are high carbon ferrochrome, chrome ore, lime and silicon chromium alloy.

The temperature of high carbon ferrochromium liquid in converter is high, usually between 1723℃ - 1873℃. 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 slag making material. It is required that the content of SiO3 in chrome ore should be low, the content of MgO and Al2O3 can be appropriately higher, and its viscosity should not be too large. Lime is also used as slagging material, and its requirements are the same as those of electro silicothermic method. Silicon chromium alloy is used to reduce high chromium slag in the later stage of blowing, generally using Si-Cr alloy powder under the sieve after crushing.