With the rapid development of smelting technology and the steel industry, metallurgical refractory materials have also achieved new changes in technology, getting rid of their high dependence on natural raw materials and original products, and gradually moving towards fine products based on artificial synthetic materials. . Unshaped refractory materials have obvious advantages over shaped refractory materials because they are easy to mechanize and automate production and can be repaired to extend their service life. They have gradually become an element in the production of the metallurgical industry. In overseas industrialized countries, the metallurgical industry The usage rate of unshaped refractory materials is as high as more than 50%. At present, countries around the world are continuing to conduct in-depth research on the new generation of amorphous refractory materials, which has greatly promoted the sustainable development of the entire metallurgical industry. This article analyzes and explores the application and development of unshaped refractory materials in the metallurgical industry, which is of certain significance.
Definition and characteristics of unshaped refractory materials
Unshaped refractory materials are also called bulk refractory materials. They are composed of aggregates, fine powders, binders and admixtures mixed in a certain proportion. They are a new type of refractory material that has an indefinite shape, is not fired, and can be used directly. Generally, aggregates are particles larger than 0.088mm, which constitute the skeleton of the entire unshaped refractory material. The dosage accounts for 60% to 73%, including coarse aggregates (>5mm) and fine aggregates (<5mm); fine powders are less than 0.088mm. mm particles are the matrix part of the entire material. They play the role of linking or cementing refractory aggregates at high temperatures, accounting for 15% to 40%. The binder, under certain conditions, uses hydration, chemistry, polymerization, cohesion, etc. The compound gains strength; admixtures are materials that strengthen the binding agent and improve the matrix properties, including coagulants, retarders, water reducing agents, inhibitors, quick-drying agents, etc.
Compared with shaped refractory materials, unshaped refractory materials do not have complicated firing processes. The raw materials required for production are easy to obtain, low in price, and the production process is simple. The plasticity is very strong, and the refractory resistance and chemical stability of unshaped refractory materials can reach similar levels. The level of refractory bricks facilitates pre-making into blocks, making it easy to produce various complex-shaped products in smelting production, and is conducive to the mechanization of furnace construction; it is also more convenient to use and can be used directly or after deployment. However, due to its shortcomings such as long time consumption in low-temperature environments, low medium-temperature strength, and easy peeling after long-term use at high temperatures, it requires higher baking technology during use. At the same time, its volume stability is not good enough, its porosity is high, its corrosion resistance is average, and its quality may fluctuate. Although it is easy to use, it is not convenient to disassemble after use, and special construction equipment must be equipped on site.
Application advantages of unshaped refractory materials in the metallurgical industry
As the main refractory material in today’s metallurgical industry, amorphous refractory materials have their own unique application advantages, which are mainly reflected in the following aspects:
2.1 Higher refractoriness
The basic property of refractory materials is that they do not soften or deform under high temperatures. Different refractory materials have different temperature conditions for softening under load. In order to ensure that the structural strength of thermal equipment is not destroyed at the highest operating temperature and maintain a long service life, Materials must be selected whose refractoriness is higher than the maximum temperature of the thermal equipment. High-temperature kilns are commonly used equipment in the metallurgical industry. In smelting operations, there are high requirements for the refractoriness of the lining of high-temperature kilns. The refractory resistance of unshaped refractory materials is generally above 1500°C, which can well meet the requirements of blast furnaces. The use of working conditions can extend its service life and improve the performance of smelted products.
2.2 Small energy consumption
General shaped refractory materials need to be processed through a special firing process. This firing process is very complex and consumes a lot of energy, resulting in large production costs. The biggest advantage of unshaped refractory materials is that it eliminates the firing process, which can avoid a lot of energy waste. Under the same working conditions, its energy consumption is about 15 to 20 times lower than traditional refractory bricks on average, and it can achieve better economics. , which is also an important reason for its widespread use in the modern metallurgical industry.
2.3 Higher metallurgical efficiency
Removing the amorphous refractory materials in the firing process can not only reduce the consumption of energy resources, but also simplify the smelting process, which can greatly save smelting time and improve metallurgical production efficiency. From the perspective of production operation practice, the production efficiency of using unshaped refractory materials is generally 3 to 5 times higher than that of refractory bricks.
2.4 Better integrity
Since the volume of amorphous refractory materials is much smaller than that of ordinary refractory materials, it is easier to transport, meets the conditions for large-volume transshipment, and can reduce transportation costs. In addition, the extremely strong plasticity of amorphous refractory materials can be constructed into any shape, and the internal structure is tight and the condensation performance is strong. The high-temperature kiln lining using amorphous refractory materials is an integral structure, so it is not susceptible to damage during the smelting process. High temperature damage can greatly extend the service life of high-temperature kilns, which can generally be increased by 30% to 150% compared with traditional refractory bricks. Moreover, due to its integrity, the sealing performance of high-temperature furnaces is also much better than that of qualitative refractory materials. This reduces overall energy consumption.
Application
3.1 Application of unshaped refractory materials in blast furnaces
As an important equipment in the metallurgical industry, traditional blast furnaces use steel plates as the furnace shell, and the shell is lined with refractory bricks. It is generally built with high-alumina cement, phosphate high-alumina refractory castables and prefabricated blocks. Modern blast furnaces are mainly used Resin bonded aluminum carbon does not burn bricks for masonry. The water-cooled walls of large blast furnaces are made of SiC castables. The furnace bottom cushion and surrounding brick joints are filled with silicon nitride materials. It has become a common feature of the industry to use castable refractory materials for the furnace walls, which can achieve better results. For example, Japan’s Fukuyama Steel Pipe Factory The Al₂O₃ material used in the No. 2 blast furnace has not seen large-scale spalling for six consecutive years. Currently, Al₂O₃-SiC-C (ASC) and mullite SiC-C are unshaped refractory materials commonly used in blast furnace tap channels at home and abroad. Japanese blast furnaces mostly use “ASC” castables, Western industrial powers generally use SiC-C ramming materials, and our domestic metallurgical industry mainly uses SiC steel jade.
3.2 Application of unshaped refractory materials on ladles
Refractory materials used in ladles Due to the increase in tapping temperature and the prolongation of the retention time of molten steel in the ladle, the originally used shaped refractory materials began to be gradually replaced by unshaped refractory materials. Based on the amorphous characteristics of the ladle, production automation can be realized, which helps to improve production capacity and production efficiency. Practical experience shows that the unshaped side walls of the ladle can save about 40% of maintenance man-hours; when the ladle is completely unshaped, the labor saving effect can reach 70% or more. At present, many steel companies use Al₂O₃-spinel castable as refractory material in their ladles. This material has good corrosion resistance, has little structural impact at high temperatures, and can extend the service life of thermal equipment. However, its performance will still be affected by the tapping temperature and the residence time of molten steel. In order to solve this technical problem, the Al₂O₃-MgO castables, aluminum-magnesium carbon refractory castables and magnesium refractory materials developed in Japan were successively born. These new The strength and permeability resistance of the material have been greatly improved, and the use effect on ladles is also better.
3.3 Application of unshaped refractory materials on heating furnaces
The heating furnace is used to heat steel billets at high temperatures. Since the maximum temperature is as high as about 1400°C, the furnace roof and furnace lining can be constructed with castables or plastics. Generally, the lining of large-scale walking heating furnaces can be made of plastic refractory materials, and the average service life can reach about 12 to 15 years. However, the walking heating furnaces in high-speed wire rod workshops have larger refractory requirements due to their larger furnace bodies. High, clay structural castables can be used. This material is not only convenient for mechanical construction, but also has no honeycomb shape after demoulding. It has good fluidity and can well meet the operating environment requirements of thermal equipment.
Development trend
The proportion of amorphous refractory materials in the entire refractory materials has become an important symbol to measure the technological development level of a country’s refractory industry. Today’s industrial powers in the world attach great importance to the research and development of new amorphous refractory materials, promoting the development of refractory materials in the metallurgical industry in the direction of high-performance castables, fully dry vibrating materials, and flame spraying materials, indicating that amorphous refractory materials will have a bright future in the future. The market has broader application prospects.
4.1 Material development direction
First of all, in the past, amorphous refractory products were mainly made of materials such as neutral and acidic oxides. The heat resistance and corrosion resistance of the amorphous refractory materials can no longer meet the higher requirements of metallurgical processes, and alkaline oxide materials are used. Unshaped refractory materials based on , oxide and non-oxide composite materials can solve this problem well. This is also a development trend of current unshaped refractory materials for metallurgy. For example, the slurry-like coating material mainly composed of high-grade alumina fiber and refractory filler has stronger wind erosion resistance, high temperature resistance, anti-cracking performance, ablation resistance and alkali chemical corrosion resistance; the highest resistance to With a hot air flow of 80m/s, it can withstand high temperatures of 1700°C and has no cracks after long-term use in high temperature environments. It can be hot repaired and does not need to be cooled down during use, making it suitable for large-area spraying.
Secondly, modern unshaped refractory products use more high-quality synthetic refractory materials. At present, unshaped refractory materials have gradually developed from single refractory castables to refractory pressure castables, and new materials such as castables and gunning materials have appeared on traditional types such as plastics, ramming materials, and projection materials. For example, lightweight castables formulated with high-quality lightweight aggregates, refractory powders, binders, and admixtures have lower thermal conductivity, stronger thermal insulation, and better thermal shock resistance, and can be widely used in industry Thermal insulation parts of kilns and thermal equipment. The continuous research and development and innovation of refractory materials have further improved the efficiency of metallurgical operations and industrial economy.
4.2 Development direction of combined methods
Unshaped refractory materials are usually composed of a continuous bonded phase and a discontinuous aggregate phase. Since the strength of the aggregate phase particles is greater than that of the bonded phase, the bonded phase is a key factor affecting the structural strength of amorphous refractory materials. It directly Reflected in the performance of the binder. First of all, the bonding methods of amorphous refractory materials in the metallurgical industry have experienced from water and bonding, chemical bonding, water and bonding + coagulation bonding, to polymerization bonding, and have developed in the direction of agglomeration and aggregation, following the high impurity-low Impurities-the impurity-free development route, the purity of the binding agent is getting higher and higher [6]. Secondly, with the advancement of blast furnace technology in recent years, higher technical requirements have been put forward for the performance of amorphous refractory materials. In order to reduce blast furnace damage and improve metallurgical benefits, the combination method of amorphous refractory materials has also begun to change from high moisture to low The moisture content turns to moisture-free and gradually develops towards high density, further improving the overall performance of amorphous refractory materials in the metallurgical industry.
Conclusion
Unshaped refractory materials have special advantages that shaped refractory materials do not have, and are an important basis for the high-quality development of the modern metallurgical industry. Although there are still certain shortcomings, its overall development is on an upward trend. With the continuous advancement and improvement of technology, new amorphous refractory materials will surely promote the in-depth development of the entire metallurgical industry through development and innovation.
