According to a report by the European Glass Association, global flat glass production in 2014 was 52 million tons, or about 10,000 tons per week. China's production accounts for 50% of the world output, and other major producers are located in Europe, North America, ASEAN, Japan, CIS, South Africa and other countries and regions.
Since the reform and opening up, China's raw material industry has developed rapidly, with rapid growth in the output of steel, cement and flat glass industries. around 2012, overcapacity problems emerged in steel, cement and glass industries one after another. After 2012, flat glass, cement, steel production is no longer increased or even reduced, into the "new normal".
Steel, cement and glass industries are the main users of refractory materials. Due to the steel, cement and glass enterprises repeatedly price pressures, default payments, many refractory enterprises in a difficult situation. Therefore, refractory enterprises need to make efforts to innovate, improve the quality of existing products, improve after-sales service and develop new products in order to win the leadership in negotiations and sales discourse.
On the one hand, the traditional market is no longer growing; on the other hand, the traditional technology is difficult to improve. For the traditional materials with less opportunities, there is still room for improvement. Through market segmentation, in-depth analysis and precise positioning, we can open up a promising "blue ocean" in the highly competitive "red ocean" of refractories for glass kilns.
Due to the differences in raw materials, fuel, power and labor costs, the price of refractories in China is only one-third of that in Japan and one-half of that in the United States. If the difference in quality is not significant, domestic refractories can replace foreign ones. Even if the quality is different, foreign materials can be used for key parts of the kiln and domestic materials can be used for other parts, which can greatly reduce the cost without affecting the service life. For this reason, on the one hand, foreign enterprises frequently launched anti-dumping; on the other hand, they strengthened R&D, trying to occupy the high point of science and technology and lead the development of refractory materials.
In the 1980s, some foreign factories achieved a high degree of automation and initial intelligence. For example, a plant with an annual production capacity of 50,000 tons of Refra had only 100 employees and used computer-aided formula design. With the development of information technology, foreign companies increasingly used CAX (CAD computer-aided design, CAE computer-aided engineering analysis, and CAM computer-aided manufacturing) to improve the manufacturing of refractory materials. in the 1990s, the China Building Materials Society analyzed the refractory materials used in Jidong and Handan cement plants. The results showed that: (1) the quality of imported materials was stable and the performance basically met the requirements; the quality of domestic materials was unstable, with some performance meeting the standards and some not; (2) imported materials had accurate dimensions and almost no internal damage; domestic materials had inaccurate dimensions and a few had hidden cracks.
In recent years, the equipment of Chinese refractory enterprises has been greatly improved. In the manufacturing process of refractories, important links such as batching, molding and firing have been gradually automated, and the quality of refractories has been significantly improved. In the future, online inspection and sorting of bricks and brick materials should be strengthened. In addition, Chinese companies need to improve the use of CAX, such as the development of non-standard refractory equipment. General equipment can be purchased in the market, but special equipment needs to be developed on its own. At present, China has made great progress in computer-aided process design, and has not only published several papers but also monographs.
The world's leading manufacturers of electrofused refractories include Saint-Gobain Sirp, RHI A and Asahi Glass. SIP acquired Cohart (USA), Toshiba Monofrax (Japan) and has two subsidiaries, CUMI and SIP Beijing, in India and China. RHI AG has two brands, Monofrax (USA) and Refl (I). With a large number of refractories made in China entering the world market, the profit margins of foreign electrofused refractories are being squeezed. Fused cast AZS materials are the most affected, followed by fused cast Al2O3, and fused cast ZrO2 materials are also affected. On the one hand, fusion casting is less restricted by the mold, conducive to the manufacture of large products, conducive to reducing the brick joints and erosion along the brick joints; on the other hand, the apparent porosity of fusion casting materials is very low, molten glass is difficult to penetrate into the material. Therefore, fusion casting materials have corrosion resistance that cannot be matched by ordinary sintered refractories. However, the corrosion resistance of different electrofused refractory materials is still very different, and the refractory materials should be used reasonably according to the kiln site and material characteristics. 1400℃ or below, the corrosion rate of all casting materials is very small; above 1400℃, the corrosion resistance is in order: Cr2O3-Al2O3, 41#AZS, 36#AZS, 33#AZS, α-Al2O3, α-β- Al2O3. Due to the coloring characteristics of Cr2O3, the melting part of the glass kiln is built with 33", 36" and 41" electrofused AZS bricks. Generally speaking, 41# electrofused AZS is used for harsh parts, 36# electrofused AZS is used for eroded middle parts, 33# electrofused AZS is used for relatively mild parts; the chest wall of the cooling part can be made of β-Al2O3 bricks, and the pool wall and bottom bricks of the cooling part can be made of α-β-Al2O3 electrofused bricks. In recent years, domestic and foreign manufacturers, especially foreign companies, significantly increased the ZrO2 content of corundum materials for fusion casting method, such as 33 # AZS ZrO2 content to 34%-35% (w); 36 # AZS ZrO2 content to 37% ~ 39% (w); 41 * AZS ZrO2 content to 43% -45% (w). Cooling part of the pool wall and pool bottom tile can be made of α-β-Al2O3 electrofusion brick. In recent years, domestic and foreign manufacturers, especially foreign companies, significantly improve the ZrO2 content of molten cast corundum materials, such as 33 # AZS ZrO2 content to 34% -35% (w); 36 # AZS ZrO2 content to 37% ~ 39% (w); 41 * AZS ZrO2 content to 43% -45% (w). Cooling part of the pool wall and pool bottom tile can be made of α-β-Al2O3 electrofusion brick. In recent years, domestic and foreign manufacturers, especially foreign companies, significantly increased the ZrO2 content of fusion-casting corundum materials, such as 33 # AZS ZrO2 content to 34% -35% (w); 36 # AZS ZrO2 content to 37% ~ 39% (w); 41 * AZS ZrO2 content to 43% -45% (w).
In the electrofused zirconia corundum material, zirconia has the role of improving corrosion resistance; the glass phase has the role of fluxing during melting, moderating thermal stress, and reducing the hazard of zirconia phase change during cooling. The key to the melting and casting process of zirconium corundum refractories is to uniformly distribute the primary zirconia of suitable size and shape in the glass phase of suitable composition and quantity, so that the primary zirconia and the glass phase cooperate with each other. And protect each other; this can make fused cast corundum refractories with higher zirconia content, lower glass phase content and higher manufacturing qualification rate.
With the promotion of oxygen-rich combustion technology, the concentration of alkali vapor in the flame space of the glass melting furnace has increased greatly, seriously corroding the refractories in the upper space of the glass melting furnace. Corrosion of refractory materials into the kiln molten glass, producing stones, streaks and bubbles, affecting the quality of glass. Therefore, low exudate electrofusion refractories were developed.
The glass phase content was reduced from 21% to 14% (w) in the low exudate electrofused refractories. As a result, more expensive desiliconized zirconium needs to be added to the ingredients, the melting temperature is increased during melting, and the cooling rate of the bricks is controlled during cooling. These measures significantly increased the production cost, but the glass phase exudation was only reduced from 1.5% to 0.7% (w). ER2001, on the other hand, adopted the opposite technical route, significantly reducing the ZrO2 content and increasing the A12O3 content, especially the Na20 content. As the content of ZrO2 was reduced from 33% to 17% (w), the manufacturing cost was greatly reduced; the glass phase exudation was reduced from 1.5% (w) to 0, which greatly improved the anti-exudation performance. According to the Al2O3-SiO2-ZrO2 ternary phase diagram, ER 2001 precipitates corundum firstly on cooling, followed by corundum and mullite at the corundum-mullite junction; however, due to the relatively large content of Na2O3. only corundum precipitates; finally, corundum and plagioclase zircon precipitates at the lowest eutectic point. Due to the incomplete crystallization of zirconia, the remaining zirconia increases the viscosity of the glass phase; the flow of the glass phase is restricted due to the distribution of fine zirconia in the glass phase. Therefore, the glass phase exudation is zero. Corundum and mullite precipitate at the corundum-mullite junction; however, due to the relatively large Na2O3. content, only corundum precipitates; finally, corundum and plagioclase precipitate at the lowest eutectic point. Due to the incomplete crystallization of zirconia, the remaining zirconia increases the viscosity of the glass phase; the flow of the glass phase is restricted due to the distribution of fine zirconia in the glass phase. Therefore, the glass phase exudation is zero. Corundum and mullite precipitate at the corundum-mullite junction; however, due to the relatively large Na2O3. content, only corundum precipitates; finally, corundum and plagioclase precipitate at the lowest eutectic point. Due to the incomplete crystallization of zirconia, the remaining zirconia increases the viscosity of the glass phase; the flow of the glass phase is restricted due to the distribution of fine zirconia in the glass phase. Therefore, the glass phase exudation is zero. The remaining zirconia increases the viscosity of the glass phase; the flow of the glass phase is restricted due to the distribution of the fine zirconia in the glass phase. Therefore, the amount of glass phase exudation is zero. The remaining zirconia increases the viscosity of the glass phase; the flow of the glass phase is restricted due to the distribution of the fine zirconia in the glass phase. Therefore, the amount of glass phase exudation is zero.
Recently, domestic electric fusion refractory manufacturers have been transplanted to the casting industry to improve the manufacturing level of resin sand, fusion mold, disappearing mold, V method casting and other electric fusion refractories.
Resin sand uses phenolic resin or vulcanized resin as the binding agent. For example, the original sand is mixed with thermoplastic phenolic resin, urotropine, calcium stearate, etc. to make laminated sand, and the model is formed by molding and heat treatment. The advantages of resin sand modeling are: high productivity, high model strength, high model accuracy, and few defects on the casting surface; disadvantages: high resin prices and environmental pollution.
Investment casting and disappearing mold casting are suitable for manufacturing shaped casting materials. Investment casting is also called "lost wax casting": the wax is made into a casting, coated with refractory material, solidified, heated and poured, and then formed into a model by heat treatment. In the case of lost mold casting, the mold is made with foam and the refractory material is immersed in a sandbox that can be vacuumed. The foam is filled with model sand and compacted, then covered with plastic film and vacuumed. During casting, the foam is heated and vaporized rapidly, the steam is evacuated, and the melt cools to form the refractory. Because the melt is in contact with the plastic during the casting process, the vanishing mold is not applicable to the manufacture of zirconia corundum materials.
The V method is a molding method named after the initials of Vacuum, i.e. the vacuum sealing molding method. the V method was born in Japan in the late 1960's and was introduced to China in 1974. At present, hundreds of foundries in China have adopted the V method for production. the advantages of the V method are:
1) High surface accuracy of castings.
2) Small machining allowance for castings, which helps to save machining hours, electricity and material consumption.
3）Saving raw material and labor cost, sand recovery rate can reach 95%, power and labor consumption is about 60% of wet molding.
4) As the gas produced during molding and casting is pumped out by vacuum pump, the pollution is small and the working environment is improved.
In the 1980s, China introduced advanced manufacturing technology U.S. silica bricks for glass kilns. In order to distinguish it from the original product, the product manufactured with the imported technology is called high quality silica bricks. With the adoption of oxygen-rich combustion technology, the service life of silica bricks was drastically reduced from 5 to 10 years to 2 to 3 years. Rat holes and erosion are the main causes of damage. Rat holes are caused by alkali condensation in the kiln leakage eroding the silicon bricks at the joints of the bricks. Methods to improve the life of silica bricks are as follows.
(1) improve the size of the brick precision. Cracks between bricks become narrower, kiln leakage less, erosion light, and small rat holes.
(2) Reasonable design of kiln lining structure, so that the condensation temperature section of alkali moved to the sealing layer behind the silicon brick.
(3) the use of good corrosion resistance of low-calcium silica bricks or high purity silica bricks.
General heat storage chamber lattice body uppermost layer using high-grade magnesium brick, w (MgO) > 97%; upper layer using mid-grade magnesium brick, w (MgO) about 95%-96%; middle layer directly combined with magnesium brick; lower layer using low porosity clay brick.
The important properties of the lattice are corrosion resistance and creep resistance. To improve creep resistance, it is necessary to use raw materials with high purity, low iron, low porosity and large grain size, and high temperature and full sintering. The stability and heat exchange of cylindrical lattice bricks are superior to that of strip lattice bricks. For example, the specific heat transfer area of cylindrical bricks is 16 m", while that of strip bricks is only 10.4 to 12.7 m".
Both the glass industry and the refractory industry are traditional industries, but neither is a sunset industry. Therefore, the research and development of refractory materials for glass kilns should be carried out in the following aspects.
► Market segmentation. Electrofused refractories are divided into pool bottom, pool wall and superstructure materials, and the lack of previous research on superstructure materials was found, and low permeation electrofused corundum refractories were developed °
►In-depth analysis. Analyzed the damage mechanism of the silica bricks at the top of the road, found out the mechanism of rat hole formation, and laid an amorphous refractory layer and insulation layer behind the silica bricks, thus greatly improving the service life of the road top.
►Precise positioning. Improve the purity of the matrix, introduce a small amount of CaO and Fe2O3 for mineralization, and prepare high purity and high performance silica bricks.
►Transplantation hybridization. The vacuum seal molding method in metal casting was introduced into the manufacture of electrofused refractories, and good results were achieved.
►Use of new technologies. Using information technology, through continuous efforts, we have developed computer-aided process optimization methods, which have greatly improved quality management and R&D.
►Capture the opportunity. In response to the fact that glass enterprises adopt petroleum coke as an alternative fuel, which leads to a significant decrease in the service life of refractories for glass kilns, we developed new refractories for heat storage chambers.
In short, we should seize all opportunities and take all methods to strive to improve technology, enhance product quality, improve R&D efficiency, perfect after-sales service, gradually build up product awareness and reputation, establish a strong brand, and finally realize the transformation and upgrading of the Chinese chemical refractories industry.
