Classification of ferro silicon nitride
Ferro silicon nitride can be divided into two categories according to its use:
ferrosilicon nitride for refractory materials and ferro silicon nitride for steelmaking. Powdery ferro silicon nitride is mainly used in the plug mud of large blast furnaces, and a small amount is used in iron groove material or other amorphous refractories.
Granular ferro silicon nitride is mainly used for oriented silicon steel or other steels that use nitride to increase strength (such as HRB400 rebar). According to its characteristics, ferro silicon nitride for steelmaking can be divided into ordinary ferro silicon nitride for steelmaking and high purity ferro silicon nitride for steelmaking. According to its characteristics, ferro silicon nitride for refractory materials can be divided into: ordinary ferro silicon nitride for refractory materials and high purity ferrosilicon nitride for refractory materials.
| Product | Element content% | |||
| Ferro Silicon Nitride | N | Si | Fe | AI+Ca |
| 30-32 | 48-50 | 13-16 | ≦2.5 | |
Application of ferro silicon nitride in refractory materials
①Al2O3-SiC-C series refractory material
Ferric silicon nitride is widely used in Al2O3-SiC-C clay, iron hook material and refractory brick. Especially, it is widely used in blast furnace blast mud in developed countries, so that the plugging performance of the blast mud has been significantly improved, to meet the needs of blast furnace iron production, and to become an indispensable part of the modern blast furnace blast mud. Adding a small amount of ferro silicon nitride to the iron trench can greatly improve the iron flow of the iron trench, and Japan began to use this method in the 1970s.
②Fe-Si3N4-SiC composite material
Si3N4-SiC material has good physical and chemical properties, especially high temperature properties, and is widely used in high temperature fields such as blast furnaces and aluminum electrolyzers, and has a good use effect. Compared with pure silicon nitride, ferric silicon nitride has better sintering properties and can be used as high temperature bonding phase. Fe-si3n4-sic composites not only contain high temperature reinforcement phase SiC and silicon nitride, but also contain metal plastic phase (Fe, FeSi or Fe3Si), which can improve the thermal shock resistance of the material, and has a good application prospect in the field of high temperature.
③ Other refractory materials
Ferro silicon nitride contains high temperature reinforced phase silicon nitride and metal plastic phase Fe, which has a series of excellent properties such as good high temperature performance, small thermal expansion coefficient, good thermal shock resistance and not easy to be penetrated by slag, etc., and has also been used in other refractory materials. For example, the University of Science and Technology Beijing uses corundum and spinel as raw materials, adding ferro silicon nitride in the form of fine powder, and preparing low-cost chromium-free non-burning refractory with good oxidation resistance and erosion resistance according to the transition plasticity theory. The refractory has excellent physical properties, good oxidation resistance and corrosion resistance of molten steel, and can be used in RH refining furnace instead of magnesium-chromium brick.
Application of ferro silicon nitride in steelmaking field
In the field of steelmaking, granular ferric silicon nitride was initially used in the production of oriented silicon steel, which can add a certain amount of nitrogen to molten steel stably. The amount of ferro silicon nitride currently used amounts to several hundred tons a year. In recent years, the progress of smelting technology has made the production of high-strength microalloyed steel develop rapidly in China, and the strengthening microalloyed elements of steel mainly include vanadium, niobium, titanium and so on. By calculation and comparison and practical application, the production of HRB400 steel bars using FeV50+ ferric silicon nitride microalloying scheme, alloying cost is reduced by 127.61 yuan compared with the single use of FeV50 tons of steel, compared with the production of VN12 microalloying tons of steel cost is reduced by 44.21 yuan. The use of ferro silicon nitride is of great significance for the production of construction steel enterprises to reduce costs and increase efficiency.
Production process of ferro silicon nitride
Ferro silicon nitride is a commonly used refractory material. Widely used in metallurgical, chemical, building materials and other industries. In the production process of ferric silicon nitride, it mainly includes the selection of raw materials, mixing, forming, baking, sintering and other links.
Selection of raw materials
The main raw materials of ferro silicon nitride are silicon nitride and metallic iron. Among them, silicon nitride is an inorganic compound with high hardness, high melting point, excellent corrosion resistance and high temperature resistance, and is the key raw material for the preparation of ferro silicon nitride. The metal iron is the carrier of ferro silicon nitride, so that the silicon nitride can be evenly distributed in the iron matrix, so as to improve the physical properties of ferro silicon nitride.
matching
After the selection of raw materials, the ratio needs to be carried out. Normally, the ratio of silicon nitride to metallic iron is 1:3-5. Different proportions have different effects on the properties of ferro silicon nitride, such as hardness, strength, wear resistance of ferro silicon nitride are related to the proportions.
mixed
Mixing is the process of thoroughly mixing silicon nitride and metallic iron. Generally speaking, there are two kinds of mixing methods: manual mixing and mechanical mixing. Manual mixing requires a certain level of technology, while mechanical mixing can improve production efficiency and mixing uniformity.
molding
Molding is the process of forming a mixture into the desired shape. Under normal circumstances, the molding methods are pressing, molding, injection molding and so on. Among these molding methods, pressing is the most commonly used one. Pressing the mixture can be pressed into the desired shape by a die, allowing the ferro silicon nitride to maintain a stable structure during the sintering process.
drying
After forming, ferro silicon nitride needs to be dried. The purpose of drying is to remove water from the mixture, thus avoiding bubbles and cracks during the sintering process. Under normal circumstances, the drying temperature is 100-200°C, and the time is a few hours to about a day.
sintering
Sintering is the last step in the production of ferro silicon nitride. At high temperatures, the metal iron in the mixture reacts with silicon nitride to form ferric silicon nitride. The sintering temperature is generally between 1500-1800°C, and the time varies from a few hours to more than ten hours. In the sintering process, it is necessary to pay attention to control the temperature and maintain a certain atmosphere to ensure the quality of ferro silicon nitride.
In general, the production process of ferro silicon nitride requires strict control of each link, to ensure the quality of raw materials and the accuracy of the ratio, as well as the process control of molding, drying and sintering. Only by doing this can we produce high-quality ferro silicon nitride to meet the needs of different industries.
