The manufacturing process of ferroniobium involves multiple links, mainly including raw material selection, smelting, casting and heat treatment. The following are detailed manufacturing steps.
1.Raw material selection
The main raw materials of ferroniobium alloy are niobium and iron, among which the purity of niobium has an important influence on the performance of the final alloy. When selecting niobium, it is necessary to ensure that its purity meets certain requirements, and take into account the chemical reaction between niobium and iron to ensure that the two elements can be fully alloyed.
In addition to niobium and iron, other elements can be added to change the properties of the alloy according to production needs. For example, ferroniobium produced using pure Nb2O5 as raw material has a low impurity content and high purity, which is called high-grade ferroniobium, and is mainly used for refining high-temperature alloys. Niobium iron produced using niobium concentrate as raw material is called standard grade ferroniobium, containing 60%~65% niobium, and is mainly used as an additive for steelmaking.
2.Smelting
Smelting is a key link in the production process of ferroniobium. Common smelting methods include arc furnace smelting and aluminothermic reduction.
Arc furnace smelting: Put the raw materials into the arc furnace, melt and mix the raw materials through the high temperature heat of the arc to form the required alloy. The arc furnace can provide high temperature conditions to melt and mix the raw materials evenly, so as to obtain a uniform alloy liquid.
Aluminothermic reduction method: The process of reducing niobium concentrate or niobium oxide with metallic aluminum to produce niobium-iron master alloy. According to the equipment used for reduction smelting, it can be divided into off-furnace aluminothermic reduction method and electric furnace aluminothermic reduction method.
Electric energy compensation heating can also be used in the aluminothermic reduction process, that is, electric furnace aluminothermic reduction method. This method can easily control the speed of the reduction reaction, obtain higher quality products, and save aluminum powder.
Aluminothermic reduction method outside the furnace: The process of realizing the reduction smelting reaction in a furnace without external heating. After the reaction is completed, the smelting furnace is disassembled, the reaction product is taken out, and the alloy and slag are separated outside the furnace. This method is relatively simple, but it is difficult to obtain high technical and economic indicators, and there are problems such as high consumption of raw materials and refractory materials.
Electric furnace aluminothermic reduction method: A production method using electric energy compensation heating during aluminothermic reduction. This method includes a one-stage method and a two-stage method. The first stage method is that the material completes the reduction reaction at one time under the action of the electric arc to produce ferroniobium. The second stage method is to melt the material in an electric arc furnace first, and then perform aluminothermic reduction smelting
3.Casting
Casting is the process of casting molten ferroniobium alloy into a specific shape. Casting can be done by sand casting, metal casting and precision casting.
Sand casting: The most common method, by casting molten ferroniobium alloy in a sand mold, and taking out the casting after cooling. Its advantages are low cost and wide applicability.
Metal casting: Pour the ferroniobium molten liquid directly into the metal mold to form the required casting, which is suitable for the production of large quantities of ferroniobium alloy products.
Precision casting: Suitable for manufacturing alloy parts of complex shapes.
Choosing a suitable casting method can improve the quality and shape accuracy of ferroniobium alloy products.
4.Heat treatment
Heat treatment is to improve the performance and organizational structure of ferroniobium alloy. Commonly used heat treatment methods include solution treatment, aging treatment and normalizing treatment.
Solution treatment: Heat the alloy to a high temperature zone to dissolve the solute in the solid solution into the matrix lattice to improve the strength and hardness of the alloy.
Aging treatment: After solution treatment, the alloy is heated and cooled for an appropriate time to obtain good mechanical properties.
Normalizing treatment: Heat the alloy to a high temperature zone and keep it warm continuously, and then change the structure and properties of the alloy by rapid cooling.
Appropriate heat treatment methods can improve the strength, hardness and corrosion resistance of ferroniobium alloys.
V. Other precautions
Throughout the production process, attention should also be paid to details such as storage, stirring and inspection of raw materials.
Raw material storage: requires sealing and moisture-proof to avoid oxidation and impurity contamination.
Stirring process: Ensure uniform mixing to ensure uniform distribution of alloy components.
Inspection process: Use chemical analysis, physical property testing and microstructure analysis to check whether the quality and performance of the alloy meet the requirements.