What is Ferro Vanadium?

What is Ferrovanadium?.

Ferrovanadium is an iron alloy that is obtained by reducing vanadium pentoxide with carbon in an electric furnace. It can also be obtained by reducing vanadium pentoxide by the silicon thermal method of an electric furnace. It is widely used as an element additive in smelting vanadium-containing alloy steel and alloy cast iron, and is also used to make permanent magnets. Ferrovanadium produced in China includes V401, V402 and other varieties, containing about 40% vanadium.

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Ferrovanadium is an iron alloy used in the steel industry. Its main components are vanadium and iron, and also contains impurities such as sulfur, phosphorus, silicon, and aluminum. There are three types of ferrovanadium based on vanadium content: FeV40 (V35.0%~50.0%, Si<2.0%, Al<4.0%, C<0.30%, P<0.10%, S<0.10%); FeV60 (V50. 0%~65.0%, Si<2.0%, Al<2.5%, C<0.30%, P<0.06%, S < 0.05%) and FeV80 (V75.0%~85.0%, Si<2.0%, Al<1.5 %, C<0.30%, P<0.06%, S<0.05%).

In addition, there are vanadium additives with trade names, such as Carvan vanadium (V82% ~ 87%, C10.5% ~ 14.5%), Nitrovan vanadium (V78% ~ 82%, C10% ~ 12%, N> 6.0%), Ferovan (V > 40%, Si5.5%~7.0%, Cr5.5%~7.5%, Mn3.6%~4.5%), etc., are used as additives for smelting alloy steel and low alloy steel. Vanadium aluminum alloy is used in titanium alloy production, often called “VQ” VAl.

Properties of Ferrovanadium

The atomic weight of vanadium is 50. 9414, and its outer electronic structure is 3d4s. Melting point 1902℃. Boiling point 3410℃. The density is 6. 1g/cm (20℃). Vanadium is a malleable metal. The binary phase diagram of vanadium and iron is shown in Figure 1. Vanadium forms a continuous solid solution with iron. And when the temperature is lower than 1210°C and in the range of V35% to 55%, the intermetallic compound α (FeV) phase is formed.

ferro vanadium FeV FeV50 FeV80

Application areas of Fervanadium

Mainly used for smelting alloy steel. About 90% of the vanadium consumed in the world is used in the steel industry. In ordinary low-alloy steel, vanadium mainly refines the grains, increases the strength of the steel and inhibits its aging effect; in alloy structural steel, it refines the grains, increasing the strength and toughness of the steel; in spring steel, it interacts with chromium or manganese Used together, it increases the elastic limit of steel and improves its quality.

In tool steel it mainly refines the structure and grains of steel, increases the tempering stability of steel, enhances its secondary hardening effect, improves its wear resistance, and prolongs The service life of the tool; in heat-resistant steel and hydrogen-resistant steel, vanadium also plays a beneficial role; the vanadium added to cast iron promotes the formation of pearlite due to the formation of carbides, stabilizes cementite, and the shape of graphite particles is fine and Uniform and refine the grains of the matrix, thereby improving the hardness, tensile strength and wear resistance of the casting.

Ferro Vanadium Production Process

1) Vanadium titanium magnetite produces vanadium pentoxide

The chemical composition of vanadium-titanium magnetite is: V0.3%~1.4%, Fe about 60%, and TiO2 about 14%. Vanadium-titanium magnetite is reduced with coke in a blast furnace (or electric furnace) to obtain vanadium-containing pig iron. Containing V0.4%~1.2%, Si<0.5%, Ti about 0.3%. The vanadium slag obtained by blowing this kind of pig iron with oxygen in a top-blown oxygen converter (or shaking ladle) contains V10%~15%, FeO25%~45%, SiO213%~20%, TiO2 about 10%, and Cr2O31%~5.0 %.

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The slag is mixed with metallic iron (semi-steel). After crushing and ball milling to a particle size of <0.1 mm, the metallic iron is selected with an air separator or magnetic separator and used as a raw material for the production of vanadium pentoxide. Vanadium exists in the spinel phase in vanadium slag. The oxidation method is used to oxidize V2O3 to V2O5, and then combine with Na2O to form water-soluble sodium vanadate. Sodiumizing agents used include soda ash, Glauber’s salt or table salt. The reaction of sodium oxide roasting is:

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

(2) Thermite method

The earliest method of producing ferrovanadium and still used today. Aluminum is the strongest reducing agent. The heat generated by reducing vanadium pentoxide with aluminum is quite large (4577kJ/kg mixture). Not only can the thermite smelting process be completed, but also recycled ferrovanadium chips must be added to reduce the reaction temperature; lime, magnesia, and fluorescent materials must be added. stone to reduce the viscosity of slag; adjust the particle size of aluminum particles and vanadium pentoxide flakes to reduce the reaction speed, reduce splash loss, and increase the yield of vanadium. Magnesia furnace lining for smelting, or a circular reaction furnace tube knotted with ferrovanadium slag. It is smelted using the lower ignition method. It is required that the vanadium pentoxide fused sheet contains V2O5≥98%. The block size is <20mm×20mm, and the sheet thickness is 3~5mm.

Aluminum is aluminum particles containing Al>98%, particle size <3mm and aluminum bubbles of 3~10mm. The steel chips are ordinary carbon steel turning chips, and the roll length is <15mm. After the smelting reaction is completed, cool naturally for 16 to 24 hours. Unplug the furnace barrel, take out the iron vanadium ingots, clean and package them. The composition of fervanadium obtained by smelting is: V75%~80%, Al1%~4%, Si1.0%~1.5%, CO.13%~0.2%, S≤0.05%, P≤0.075%. The slag composition contains V2O55%~6%, Al2O3 about 85% (CaO+MgO) and about 10%.

The consumption of producing 1t80%V fervanadium is: vanadium oxide fused flake (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 heated by electricity immediately after the reaction is completed, so that the metal particles suspended in the slag sink and continue to react with the vanadium oxide and residual aluminum in the slag to increase the recovery rate of vanadium.

(3) Silicon thermal method

Use 75% ferrosilicon and aluminum as reducing agent. Ferrovanadium containing V40% to 60% is produced in an improved three-phase alkaline electric arc furnace. The transformer capacity of the electric arc furnace is 1800kVA, the operating voltage is 127/220V, and the rated current is 4750A. The graphite electrode diameter is 200mm. Use magnesia bricks as furnace lining.

The furnace cover is made of chrome magnesia bricks. The raw materials used are: vanadium pentoxide fused flakes (V2O5≥98%, Si≤0.25%, Fe≤0.30%, P≤0.05%, S≤0.03%, As≤0.02%, Na2O+K2O≤1.5%, flakes Thickness is about 8.0mm, block size ≤200mm×200mm); ferrosilicon (75% ferrosilicon, block size ≤30mm); aluminum block (machined aluminum ingot into ≤20mm); lime (CaO≥85%, P≤0.015 %, block size 30~50mm) and scrap steel or steel scraps of ordinary carbon steel. The reaction of silicon reduction of vanadium oxide is shown in Figure 3. The reaction produces SiO2. Low-valent vanadium oxides are alkaline compounds, which have a negative impact on the reduction of vanadium. For this purpose, lime needs to be added to increase the alkalinity of the slag and promote the reduction of vanadium oxides.

The smelting process takes place in two steps. The first step is the reduction period, using ferrosilicon and aluminum to reduce vanadium oxide to obtain a vanadium ferrosilicon alloy with high silicon content; the second step is the refining period, using slag with high V2O5 to refine the vanadium ferrosilicon alloy to reduce the silicon and obtain ferrovanadium.

After the previous furnace is discharged and the furnace repair is completed, all the iron materials required to produce ferrovanadium components are added. After the electricity is turned on, the refining slag from the previous furnace is returned to the furnace, and the first batch of reducing raw materials (vanadium pentoxide flakes) are added. , lime and most of the ferrosilicon in the ingredients).

When the molten pool is formed, power is supplied at full load to melt the charge quickly. After full melting, the power supply load is appropriately reduced, and after adding the remaining ferrosilicon, the V2O5 in the aluminum reduction slag is added. Stir the molten pool thoroughly, and when the (V2O5) in the slag is <0.35%, the slag will be discharged. After slag discharging, add the second batch of reducing materials (a mixture of vanadium oxide flakes and lime). Stir thoroughly after complete melting.

Ferrosilicon is added first, and then aluminum blocks are added to reduce the slag. When the content of the slag (V2O5) is less than 0.35%, the slag is released. The amount of feed added and the number of batches during the reduction period are determined by the vanadium content (40% to 60%) of the ferrovanadium produced.

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