In modern industrial production, the operating environment of high-temperature equipment is increasingly complex, which puts forward higher requirements for the performance of refractories. As a new type of high-performance refractory, steel fiber reinforced refractory castable has been widely used in many fields because of its excellent mechanical properties and thermal shock resistance. This paper will introduce the composition, properties, application and future development trend of steel fiber reinforced refractory castable in detail.

I. Composition and preparation of steel fiber reinforced refractory castable

Steel fiber reinforced refractory castable is mainly composed of refractory aggregate, powder, binder, admixture and steel fiber. Among them, high alumina, corundum and mullite are usually used as refractory aggregates, which have high refractoriness and good corrosion resistance; Powder is used to fill the pores between aggregates to improve the compactness of castable; Binders are generally aluminate cement, phosphate or sodium silicate, which are used to make the castable have a certain strength at room temperature and further sinter at high temperature. Admixtures such as water reducer and retarder are used to improve the workability of castable. Steel fiber is the reinforcing phase, and its addition can significantly improve the tensile strength, flexural strength and impact resistance of castable.

The preparation process of steel fiber reinforced refractory castable mainly includes weighing, mixing, stirring, forming and curing of raw materials. Firstly, all kinds of raw materials are accurately weighed according to the designed formula, and then dry materials such as refractory aggregate, powder and binder are evenly mixed, and then a proper amount of water and additives are added for stirring, so that they are fully wetted and form a uniform slurry. In the process of mixing, steel fibers are evenly dispersed into the slurry to ensure that steel fibers can play a good reinforcement role in the castable. Finally, the stirred castable is poured into the mold and molded by vibration or ramming. After the molded castable is cured at room temperature for a certain period of time, it can be used for subsequent heat treatment.

II. Performance characteristics of steel fiber reinforced refractory castable

(1) Mechanical properties

The addition of steel fiber significantly improves the mechanical properties of refractory castable. Compared with ordinary refractory castable, the tensile strength, flexural strength and impact strength of steel fiber reinforced refractory castable have been greatly improved. For example, the flexural strength of ordinary refractory castable after curing at 110°C×24h is generally about 5 ~ 10～15MPa, while the flexural strength of steel fiber reinforced refractory castable can reach 10 ~ 15 MPa or even higher. At high temperature, the strength retention rate of steel fiber reinforced refractory castable is also high, which can maintain good structural stability at high temperature, effectively resist stress at high temperature, and reduce cracking and spalling caused by thermal expansion and mechanical stress.

(2) Thermal stability

Steel fiber reinforced refractory castable has excellent thermal shock resistance. When the temperature of high-temperature equipment changes sharply during operation, ordinary refractories are prone to crack or even spalling due to thermal stress, while steel fiber reinforced refractory castable can effectively disperse thermal stress and reduce crack propagation due to the reinforcement of steel fiber, thus improving the thermal shock resistance of materials. Experiments show that the strength retention rate of steel fiber reinforced refractory castable can still reach more than 80% after repeated thermal shock tests (such as 1000°C water cooling cycle), while the strength retention rate of ordinary refractory castable may be less than 50%. This good thermal shock resistance makes steel fiber reinforced refractory castable especially suitable for lining of high-temperature equipment with frequent temperature fluctuation, such as heating furnace, hot blast stove and circulating fluidized bed boiler.

(3) Wear resistance

The wear resistance of steel fiber reinforced refractory castable has also been significantly improved. In high temperature environment, the surface of materials is easily eroded by airflow and particles, and the reinforcement of steel fibers can improve the hardness and toughness of materials, making them perform well in wear resistance. For example, in a circulating fluidized bed boiler, due to the high-speed circulation and scouring of solid particles, the wear resistance of lining materials is extremely demanding. Steel fiber reinforced refractory castable can effectively resist the erosion and wear of particles and prolong the service life of equipment. The research shows that the wear resistance of steel fiber reinforced refractory castable is 30% ~ 50% higher than that of ordinary refractory castable, and its service life can even reach more than twice that of ordinary refractory castable in some harsh wear environments.

(4) Construction performance

The construction performance of steel fiber reinforced refractory castable is also excellent. Due to the addition of steel fiber, the fluidity of castable will be affected to some extent, but by reasonably adjusting the dosage of admixture and mixing process, it can still have good fluidity and operability on the premise of ensuring the uniform dispersion of steel fiber. During construction, only the stirred castable is poured into the mold, and it can be molded by vibration or ramming. The construction process is simple and fast, and the molded castable has good integrity and compactness, which can meet the construction requirements of high-temperature equipment linings with different shapes and sizes.

III. Application of steel fiber reinforced refractory castable

(1) Metallurgical industry

In metallurgical industry, steel fiber reinforced refractory castable is widely used in lining of various high-temperature furnaces, such as ladle, tundish, ladle, heating furnace and soaking furnace. These equipments need to withstand high temperature, thermal shock and corrosion of molten metal and slag during operation. The high strength, wear resistance and thermal shock resistance of steel fiber reinforced refractory castable can effectively improve the service life of equipment, reduce the shutdown maintenance time and improve production efficiency. For example, using steel fiber reinforced refractory castable in ladle lining can effectively prevent molten steel from eroding the lining, prolong the service life of ladle and reduce the production cost.

(2) Electric power industry

In the power industry, circulating fluidized bed boiler is a common combustion equipment, and its lining material needs to have good wear resistance and thermal shock resistance. Steel fiber reinforced refractory castable can meet these requirements and is widely used in the lining of combustion chamber, separator and feeder of circulating fluidized bed boiler. In addition, steel fiber reinforced refractory castable is often used to protect the high-temperature parts of boilers, steam turbines and other equipment in some large thermal power plants to improve the safety and reliability of the equipment.

(3) Petrochemical industry

The high-temperature reaction furnace, cracking furnace, reforming furnace and other equipment in petrochemical industry need to operate in high temperature, high pressure and strong corrosion environment. The high temperature resistance, corrosion resistance and thermal shock resistance of steel fiber reinforced refractory castable make it an ideal lining material for these equipment. For example, in the ethylene cracking furnace, the surface temperature of the furnace tube is as high as 1000°C, and it is eroded by high-temperature flue gas and chemical reaction products. Using steel fiber reinforced refractory castable as the furnace tube lining can effectively protect the furnace tube, prolong the service life of the equipment and ensure the normal production.

(4) Building materials industry

In the building materials industry, the lining materials of high-temperature kilns such as glass kilns and ceramic kilns also need to have good fire resistance and corrosion resistance. The steel fiber reinforced refractory castable can be used as the lining of the breast wall, vault and pool wall of these kilns, which can effectively resist the erosion of high temperature flame, glass melt and ceramic melt, and improve the service life and production efficiency of the kilns. In addition, in some cement rotary kiln, lime kiln and other equipment, steel fiber reinforced refractory castable has also been widely used, providing a reliable guarantee for the production of building materials industry.

IV. Development trend of steel fiber reinforced refractory castable

(1) high performance

With the continuous improvement of the performance requirements of high-temperature equipment in industrial production, steel fiber reinforced refractory castable is also developing towards high performance. In the future, researchers will devote themselves to further improving the refractoriness, corrosion resistance, thermal shock resistance and wear resistance of steel fiber reinforced refractory castable. For example, by optimizing the composition and particle size distribution of raw materials, developing new binders and additives, and adopting advanced preparation techniques, such as spray deposition and gel injection molding, steel fiber reinforced refractory castable with higher strength, lower thermal expansion coefficient and better thermal shock resistance is prepared to meet the more demanding requirements of high temperature environment.

(2) Multifunctional

In addition to the traditional functions of fire resistance, wear resistance and thermal shock resistance, steel fiber reinforced refractory castable will also develop in the direction of multi-function. For example, develop steel fiber reinforced refractory castable with heat insulation function to reduce heat loss of high-temperature equipment and improve energy utilization efficiency; Develop steel fiber reinforced refractory castable with impermeability to prevent equipment from being corroded by high temperature melt or liquid; The development of steel fiber reinforced refractory castable with self-healing function can automatically repair micro-cracks and prolong the service life of the material. In addition, by adding specific functional materials, steel fiber reinforced refractory castable can have special properties such as alkali resistance, acid resistance and sulfur resistance to adapt to different chemical environments.

V. Conclusion

As a high-performance refractory, steel fiber reinforced castable has been widely used in metallurgy, electric power, petrochemical industry, building materials and other fields because of its excellent mechanical properties, thermal stability, wear resistance and construction performance. With the continuous development of industrial production technology and the increasingly strict requirements of environmental protection, steel fiber reinforced refractory castable will develop in the direction of high performance, multifunction, green and intelligence. In the future, researchers need to explore and innovate constantly to develop more high-quality steel fiber reinforced refractory castable products to meet the higher requirements of industrial production for lining materials of high-temperature equipment and provide a strong guarantee for the sustainable development of industrial production.