Alias: ferrovanadium

 

English name: Ferrovanadium

 

Properties: Ferrovanadium is an iron alloy obtained by reducing vanadium pentoxide in an electric furnace with carbon. It can also be obtained by reduction of vanadium pentoxide by electric furnace silicon thermal method. It is widely used as an elemental additive for smelting vanadium-containing alloy steels and alloy cast irons, and has been used in recent years to make permanent magnets. The ferro-vanadium produced in China has V401, V402 and other varieties, containing about 40% vanadium.

 

 

1) Zircon, lime, fluorite, 75% ferrosilicon and iron oxide skin are mixed and smelted in a carbon brick lining arc furnace. After the temperature of the furnace rises to 1700 ° C, stirring and reduction are started.

 

2) When the reduction is completed, the furnace temperature is raised to 1800 to 1900 °C, and the furnace is discharged, slag, and cast. The zirconium-silicon ferrite composition obtained is: Zr 20% to 40%, Si 45% to 55%, Al < 0.5%, P < 0.1%. The zirconium recovery rate is about 55%. The slag contains ZrO 210% to 15%, and the alkalinity is 0.8 to 1.0.

 

 

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The abundance of vanadium in the earth's crust is 135×10%. There are more than 70 kinds of vanadium minerals, but there are few single vanadium deposits (only Minar Lagra in Peru is a single deposit. It has been harvested.), all of which are symbiotic with other mines. The Raw materials used for the production of vanadium are vanadium-titanium magnetite (including VO. 4% to 1.4%), uranium vanadium ore (including V2O 51.5% to 2.0%), crude oil ash (including V2O 520% ​​to 40%), containing vanadium. Phosphorus iron (containing V 3% to 6%), waste vanadium catalyst, and residue for producing alumina. These Raw materials contain low vanadium and require a hydrometallurgical process. First, vanadium pentoxide is extracted from these Raw materials, and then vanadium pentoxide is smelted into vanadium iron and vanadium additives. Vanadium-titanium magnetite concentrate is the main Raw material for the production of vanadium, and 90% of the world's vanadium production is produced from this Raw material.

(1) Vanadium-titanium magnetite production of vanadium pentoxide

The chemical composition of vanadium-titanium magnetite is: V0.3% to 1.4%, Fe is about 60%, and TiO2 is about 14%. The vanadium-titanium magnetite is reduced by coke in a blast furnace (or electric furnace) to obtain vanadium-containing pig iron. It contains V0.4% to 1.2%, Si<0.5%, and Ti about 0.3%. The vanadium slag obtained by blowing the pig iron in a top-blown oxygen converter (or shaker) with oxygen contains V10%-15%, FeO25%~45%, SiO213%-20%, TiO2 about 10%, Cr2O31%～5.0 %. The slag is interspersed with metallic iron (semi-steel). After being crushed and ball milled to a particle size of <0.1 mm, the metal iron is selected by a wind sorter or a magnetic separator to be used as a Raw material for producing vanadium pentoxide. Vanadium is present in the vanadium slag as a spinel phase. V2O3 is oxidized to V2O5 by oxidation, and then combined with Na2O to form water-soluble sodium vanadate. The sodiuming agent used is soda ash, thenardite or salt. The reaction of sodium oxide roasting is:

4FeO·V2O3+4Na2CO3+5O2 ⇀8NaVO3+2Fe2O3+4CO2↑

(2) Aluminothermic method

The earliest method of producing ferrovanadium is still in use today. Aluminum is the strongest reducing agent. The reduction of the heat generated by the reduction of vanadium pentoxide with aluminum is quite large (4577kJ/kg mixture), not only can the aluminum thermal smelting process be completed, but also the ferro-vanadium crumb can be added to reduce the reaction temperature; lime, magnesia, firefly are added. The stone reduces the viscosity of the slag; adjusts the particle size of the aluminum particles and vanadium pentoxide foil to reduce the reaction speed, reduce the splash loss, and increase the yield of vanadium. A smelting magnesia lining, or a circular reaction furnace knotted with vanadium iron slag. Smelting by the lower ignition method. Vanadium pentoxide crude is required to contain V2O5 ≥ 98%. The block size is <20 mm×20 mm, and the sheet thickness is 3 to 5 mm. Aluminum is aluminum particles containing Al > 98%, particle size < 3 mm and aluminum bubbles 3 - 10 mm. The steel scrap is a carbon steel scrap and the coil length is <15mm. After the smelting reaction is completed, it is naturally cooled for 16 to 24 hours. Remove the furnace tube, take out the vanadium iron ingot, and clean it and pack it. The composition of vanadium and iron obtained by smelting is: V75% to 80%, Al1% to 4%, Si 1.0% to 1.5%, CO. 13% to 0.2%, S≤0.05%, P≤0.075%. The slag component contains 55% to 6% of V2O, and about 85% (CaO+MgO) of Al2O3 is about 10%. Production of 1t80% V vanadium iron consumption: vanadium oxide foil (V2O598%) 1500 ~ 1600kg, aluminum (Al98%) 810 ~ 860kg. The smelting recovery rate of vanadium is 90% to 95%. In order to reduce the vanadium content in the slag, the slag is electrified immediately after the end of the reaction, the metal particles suspended in the slag are sunk, and the vanadium oxide and residual aluminum in the slag are continuously reacted to increase the recovery rate of vanadium.

(3) Electrothermal method

75% ferrosilicon and aluminum were used as reducing agents. V40-60% ferro-vanadium is produced in an improved three-phase alkaline arc furnace. The electric arc furnace has a transformer capacity of 1800kVA, an operating voltage of 127/220V and a rated current of 4750A. The GRAPHITE ELECTRODE has a diameter of 200 mm. Use magnesium brick as the lining. The furnace cover is made of chrome-magnesium brick. The Raw materials used are: vanadium pentoxide crude (V2O5≥98%, Si≤0.25%, Fe≤0.30%, P≤0.05%, S≤0.03%, As≤0.02%, Na2O+K2O≤1.5%, tablets Thickness of about 8.0mm, block degree ≤200mm×200mm); ferrosilicon (75% ferrosilicon, block degree ≤30mm); aluminum block (machined aluminum ingot to ≤20mm); lime (CaO≥85%, P≤0.015 %, block size 30 ~ 50mm) and carbon steel scrap or steel scrap. The reaction of silicon to reduce vanadium oxide is shown in Figure 3. The reaction produces SiO2. The low-valent vanadium oxide is a basic compound, which adversely affects the reduction of vanadium. To this end, it is necessary to add lime to increase the alkalinity of the slag and promote the reduction of vanadium oxide.

 

 

The smelting process is carried out in two steps. The first step is a reduction period, the vanadium oxide is reduced by ferrosilicon and aluminum to obtain a vanadium-silicon-iron alloy having a high silicon content; the second step is a refining period in which a vanadium-silicon-iron alloy is refined by using a slag having a high V2O5, and silicon is reduced to obtain vanadium iron. After the last furnace is discharged, the furnace is completed, that is, all the iron materials required for the production of ferrovanadium are added. After the electricity is turned on, the refining slag of the furnace is returned to the furnace, and the first batch of Raw materials (vanadium pentoxide crumb) is added. , lime and most of the iron and iron in the ingredients). When the molten pool is formed, the power is supplied at full load to rapidly melt the charge. After the full melting, the power supply load is appropriately reduced, and after the remaining ferrosilicon is added, the V2O5 in the aluminum reduction slag is added. The molten pool is sufficiently stirred, and when the (V2O5) in the slag is <0.35%, slag is discharged. After the slag is discharged, the second batch of Raw material (mixture of vanadium oxide foil and lime) is added. After full melting, stir well. First add ferrosilicon, then add aluminum block to reduce slag. The slag is discharged when the slag (V2O5) is <0.35%. The amount of feed and the number of batches during the reduction period are determined by the vanadium content of the ferrovanadium produced (40% to 60%).

 

    Mainly used for smelting alloy steel. About 90% of the vanadium consumed in the world is used in the steel industry. Vanadium is mainly used to refine grains in ordinary low-alloy steels, increase the strength of steel and inhibit its aging effect; in alloy structural steels, it refines grains and increases the strength and toughness of steel; in spring steel with chromium or manganese In combination, it increases the elastic limit of steel and improves its quality; it mainly refines the microstructure and grain of steel in tool steel, increases the tempering stability of steel, enhances its secondary hardening effect, improves its wear resistance, and prolongs The service life of the tool; vanadium also plays a beneficial role in heat-resistant steel and hydrogen-resistant steel; vanadium added to the cast iron promotes the formation of pearlite due to the formation of carbides, which stabilizes the cementite and the shape of the graphite particles is fine. Uniformly refining the grains of the matrix, thereby increasing the hardness, tensile strength and wear resistance of the casting. use

 

 

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