The main application of ferrosilicon
Ferrosilicon is an iron alloy composed of iron and silicon. Ferrosilicon is mainly used as a deoxidizer and alloy additive in steelmaking and is also used in casting, mineral processing, welding rod, the light metal industry, and as a reducing agent for smelting certain metals. The main raw material for smelting ferrosilicon is silica ore (quartz, silica). The SiO2 in the ore is generally required to be higher than 96%, and higher than 98% when smelting high-silicon ferrosilicon. The P2O5 in the ore should generally not exceed 0.02%. Al2O3 should not exceed 1.5%. The commonly used varieties of ferrosilicon contain 45%, 75%, and 90% silicon.
Smelting method of ferrosilicon
Low-silicon ferrosilicon (containing 10-15% silicon) can be smelted with iron ore and silica in a blast furnace. A higher coke ratio and air temperature are required. During operation, the temperature of the furnace top is high, the gas contains a lot of dust, and the production operation is difficult. In the 1970s, almost all of them were converted to electric furnaces for production. High-silicon ferrosilicon is smelted in a reduction electric furnace with carbonaceous lining, using silica, steel shavings (or iron scale), and coke as raw materials. Electric furnace ferrosilicon is smelted without slag. The raw materials must be clean and must not be mixed with mud, sand, and other impurities. Adding wood chips and coal to the charge can improve its performance of the charge. During the smelting process, the surface of the material is easy to crust and “fire” (the surface of the material sprays fire), so it must be “punched” frequently. The furnace produces ferrosilicon every 2 to 4 hours and casts it into an ingot with a thickness of less than 100 mm in the ingot mold. Refining ferrosilicon generally adopts an open electric furnace. In recent years, in order to prevent environmental pollution, “short fume hood” or “semi-closed” electric furnaces are often used to facilitate heat recovery and smoke and dust removal; to produce high-silicon ferrosilicon (containing more than 75% silicon), most of them use rotary electric furnaces to reduce Pound the furnace. The capacity of a large-scale ferrosilicon electric furnace is 10,000-96,000 kVA, and the power consumption of ferrosilicon production is about: 45% ferrosilicon, 5,000 kwh/ton; 75% ferrosilicon, 9,000 kwh/ton; 90% ferrosilicon, 14000 kWh/ton. In order to meet the requirement that the aluminum content of ferrosilicon should not be too high for electrical steel, refining methods such as oxygen blowing or chlorine blowing have been developed in recent years.
Ferrosilicon is easy to pulverize under certain conditions during storage and transportation. This is because the volume expansion is caused by the phase transformation of FeSi and FeSi2 containing about 34% silicon and 50-60% silicon. Phosphorus, sulfur, calcium, aluminum, and a humid atmosphere in impurities will promote ferrosilicon pulverization, and ferrosilicon ingots are easily pulverized due to segregation during slow cooling. Gases such as hydrogen, phosphine, and arsine are released when ferrosilicon is pulverized, which can cause an explosion. The latter two gases are poisonous, so the storage and transportation of ferrosilicon must be well-ventilated to prevent moisture.
Ferrosilicon is widely used in the steel industry, foundry industry, and other industrial production. Ferrosilicon is an essential deoxidizer in the steelmaking industry. In steelmaking, ferrosilicon is used for precipitation deoxidation and diffusion deoxidation. Brick iron is also used as an alloying agent in steelmaking. Adding a certain amount of silicon to steel can significantly increase the strength, hardness, and elasticity of steel, increase the magnetic permeability of steel, and reduce the hysteresis loss of transformer steel. Low-aluminum ferrosilicon is a special-purpose ferrosilicon variety that has appeared in recent years. Its smelting process is complicated and the product has high added value. It is an area actively explored by various ferrosilicon manufacturers.
Examples of ferrosilicon applications are as follows:
1. Add ferrosilicon powder to reduce the ferrochrome powder rate. The method includes the following steps: select ferrosilicon powder with a particle size of 5-10mm produced during the crushing process of ferrosilicon alloy as a raw material; The amount of iron powder and ferrosilicon powder is 0.5-1.0kg/t. When adding, add 1/3 of the total amount of ferrosilicon powder when the ferrochrome alloy is baked to 1/4, add ferrosilicon powder when the ferrochrome alloy is baked to 1/2 1/3 of the total amount, and then add 1/3 of the total amount of ferrosilicon powder when the ferrochrome alloy is baked to 3/4. On the one hand, the invention can prevent the generation of air bubbles, thereby obtaining dense iron ingots, can effectively reduce the powder rate of ferrochrome alloy, improve the production technical and economic indicators of ferroalloy enterprises, and greatly reduce the production cost of ferrochrome alloy. On the other hand, ferrosilicon powder is produced during the crushing process of ferrosilicon alloy, which realizes the recycling of resources, meets the requirements of energy saving and environmental protection, does not cause environmental pollution and energy waste, and the method is easy to implement, simple and convenient.
2. Prepare a ferrosilicon ball, which is made of ferrosilicon raw material and binder. The ferrosilicon raw material is a mixture of ferrosilicon powder or ferrosilicon powder and metal silicon powder; the silicon content in ferrosilicon powder is 72- 75%, the content of silicon in metal silicon powder is 72-85%; the adhesive is made of water, quartz sand, alkali, fluorite, sodium sulfate, and micro-silica powder, and its modulus is 3-3.7. The diameter of the ferrosilicon powder ball is 10-80mm. This product is ferrosilicon raw material, mixed with a binder specially used for the manufacture of this product, and then made by ball making machine, there is no need to return them to the furnace for smelting, and the composition of each substance will not change during the manufacturing process, so It is convenient to control the silicon content of the product; the ferrosilicon powder and metal silicon powder used in the manufacture can be the remaining powder after the export product is crushed, so the existing resources in our country are saved, and it is also very convenient to use.