1 Introduction Generally, high temperature insulation slag wool (HTIW) is used in various industrial high temperature fields. In recent years, high temperature glass slag cotton based on alkaline earth silicate (AES) has been produced. Instead of different thermal analysis of refractory ceramic fibers, RCF recrystallization begins at 980T with an exothermic reaction and mullite formation. The grain size varies between 0.02 pm and 0.1 μm relative to the low alumina content (30%) and the high alumina content. The desulfurization phenomenon leads to the enrichment of residual metals containing SiO 2 , and above I050T, the cristobalite begins to deposit. The CaO-MgO-SiO2 system shows different crystallization behavior. The data shows the difference between different types of cristobalite. In theory, the type of precipitated cristobalite is cristobalite. Studies have shown that high temperature 3 transitions also occur at room temperature, but are deformed and accumulated by the impurity iron. The rate of crystallization of the fibrous material depends on temperature, atmosphere, heat treatment time and impurity content. Due to the desulfurization phenomenon, the fiber surface becomes rough, mainly due to the formation of cristobalite crystals. Small grain sizes after heat treatment result in better heat resistance of the fibers. The grain grows to the size of the fiber diameter, and the long exposure time leads to cracking of the fiber structure and causes the material to break.
Resilience such as shrinkage and AES is important for industrial applications. Since low bioreactors regulate chemical components, their whiskers are nanometer in diameter, micron in length, and some are dumbbell shaped, and Well distributed in the matrix. Above 1500, (3-SiC whiskers become thicker, the diameter becomes micron, curled and gathered together.
It is not difficult to judge that if straight and dumbbell-shaped nano-sized SiC whiskers and some cristobalite are well distributed in the matrix, the performance can be improved. A more flexible structure and better thermal shock resistance can be envisaged, however the effect of silicon on the quality of the steel is taken into account. Although a large number of dumbbell-shaped p-SiC whiskers are desired, the less silicon added, the better. The low-cost preparation of dumbbell-shaped (-SiC whiskers is based on the processing of conventional carbon-bonded materials, and it is a feasible method to add them to the matrix of high-carbon bonded composite refractories.
The phenomenon observed at high temperatures above 1400 and the shape of dumbbells below 1200T (3 - SiC whiskers, recommended sintering temperature 1300-丨4001, prepared with Al23-ZrO:-C functional materials, such as skateboards, to ensure steel casting Good performance = Table 1 Chemical analysis of HTIW materials / % of materials polycrystalline alkali and alkaline earth oxides Table 2 All HTIW samples were sintered at sintering temperature for 24 h. Sintering program material sintering temperature / t polymorphic classification temperature showed Higher values, higher than normal RCF products. Classified according to the maximum temperature shrinkage of no more than 4%. If AES products are used, in case of furnace failure or nearby burner assembly, these very small thermal overloads may result in Lining masonry failed.
2 Materials based on CaO acid aluminum slag wool (RCF) are represented by materials RCF1260, RCFWOO and RCF1400Z. These materials are mainly composed of alumina and silica, and zirconia is added to RCF1400Z. The third group consists of polycrystalline slag based on mullite. All materials have an industrial source: CMS1, MS and RCF1400Z are supplied by U-nifrax GmbH, CMS2 and CMZS are supplied by European thermal ceramics, RCF1260, RCF1400 and polycrystalline slag are supplied by Rath GmbH. The chemical composition of all materials is listed in Table 1.
According to EU Directive 97/69EC, the last column of data must exceed 18%, and the man-made fiberglass cannot be separated into carcinogens.
3 Test procedure In order to determine the linear shrinkage, resilience and phase composition at high temperature, a 100 mm x 100 mm sample and a certain thickness of the fabric were placed in an electric heating furnace and exposed at a selected temperature for 24 h. Table 2 lists the sintering temperature range. . The heating rate is as follows: test temperature <12501, from 20 to 50K under test temperature, heating rate is 5Kmin and then 2Kmin-1 to test temperature and heat for 24h, then return to 20T at 3K.min-1 cooling rate; The test temperature is between 1250 ~ 1500, from 20 to 1200, the heating rate is 5Kmin-1, then 2Kmin-1 to the test temperature and kept for 24h, then return to 20 feet at 3Kmin-1 cooling rate; test temperature >1500: From 20T to 120 (TC, heating rate is SK.min-1, then min-' to 50K at test temperature, then 2K-min-1 to test temperature and heat for 24h, then 3Kmin-1 cooling rate Back to 20. All samples were heated and cooled in the furnace -7, and the linear shrinkage was determined by an optical measuring instrument. Before the test, the two platinum needles were separated by a certain distance, and the distance between the platinum needles after the test was tested. The change in the thickness of the front sample; to determine the linear shrinkage value.
In 1094-7, in order to test the recovery of the material, a rebound measurement was performed. Compress the sample to 50% of the original thickness and measure the rebound. The compression load is 2mmmin-1. The sample is compressed at 725Pa for 5min, then the load is released. The rebound is defined as follows: For the rebound measurement, the classification temperature does not exist. Comparison criteria.
After the heat treatment, quantitative XRD analysis was performed to determine the phase change caused by the temperature, and the corresponding X-ray diffraction intensity was used to determine the different phases formed.
Results According to the chemical composition, the three sets of samples of AES, RCF and polycrystalline slag cotton were greatly different. High temperature properties such as shrinkage, rebound and meltability vary drastically. For AES and RCF, after the product is crystallized again, it will show an amorphous structure, phase transformation and grain growth, which leads to cracking of the fiber structure and limits the service life of the product. For polycrystalline slag wool, at high temperatures, the transition alumina is converted to ex-alumina, and the added fine silica reacts with the main component alumina to form mullite. The growth of corundum grains is controlled by this. Due to grain growth, the brittle life of polycrystalline slag wool is limited at temperatures above 1600T.
The microstructure of all the samples was studied and then exposed to 1000t~160(n: depending on the phase change, XRD measurements were taken at the following temperatures. The results are summarized in Table 3. Table 5. Microstructural changes at 1000 CMS1 has been strongly recrystallized, and a large amount of diopside and P-wollastonite have precipitated. The XRD results show that P-wollastonite forms a diopside solid dissolved at high temperatures, but does not dissolve significantly at low temperatures. The diopside was measured at high strength between 1000 and 1300. The P form of wollastonite was converted to a-wollastonite at a high temperature above lOOOt, and the strength of a-wollastonite increased with increasing temperature. The melt is enriched in silica, which is due to the precipitation of diopside and wollastonite, which is also precipitated at 120 (Tt final cristobalite.
The chemical composition of the CMS2 and CMS1 samples is similar, showing that diopside is the main crystalline phase, and between 1000,1300, the diopside strength increases. At 1200 and 1300T, the strength of the cristobalite can be detected as weak and medium, respectively.
Table 3 The relationship between the mineral composition of AES material and temperature. The steel is removed from the stone. Note: V-very strong; S-strong; M-medium; weak; VW-very weak; T-mark M to CMZS, diopside Phase, this is due to recrystallization between 1000 弋 and 1300. At the same temperature, the cristobalite precipitates and has moderate strength. Since the amount of zirconia and zircon is very small, it cannot be detected by the XRD test.
Table 4 Relationship between mineral composition and temperature of RCF materials For MS, the measurement results are opposite to those of other AES samples. Since the chemical composition of the MS sample is silicon oxide and magnesium oxide, XRD is shown to be between 100 ° and 1100 T; between the oblique enstatite and the forsterite is a stable phase. At 1200, the phase transition from oblique enstatite to native enstatite is completed. At this temperature, forsterite is dissolved by the melt. Compared to other types of AES samples, precipitation of cristobalite at 1000 T was converted to low temperatures with high intensity. The amount of cristobalite shows no deviation when the temperature reaches 14001.
Table 5 Relationship between mineral composition and temperature of polycrystalline slag cotton Mineral-recognized mullite corundum s-alumina 0-alumina Note: VS-very strong; S-strong; M-medium; W-weak; VW- Very weak; T-trace amount was measured by scanning electron microscopy (SEM) at the classification temperature range and below 100K. One of the analysis results showed that the AES material showed a large amount of recrystallization and strong crystal growth. Up to the classification temperature (1250T), grain growth continues to increase. MS showed a small amount of recrystallization compared to CMS1, CMS2 and CMZS. The amount of recrystallization of CMS1 was found to be the highest. The SEM material was used to show changes in microstructure at different temperatures, as shown by ~. Due to the strong growth of the crystal grains, the fiber surfaces of CMS1 and CMS2 become rough. The grains on the surface reach a size of 50 to 65% of the initial fiber diameter. The increased brittleness is primarily based on grain growth. The grain boundaries between the grains result in a final rupture of the fiber structure. The grain growth of MS and CMZS is small, and the surface of the fiber has no surface roughness of CMS1 and CMS2.
1250X: After sintering for 24h, the SEM micrograph of AES slag type CMS1 is sintered for 12h after 12h, AES slag type 98 (TC, accompanied by exothermic reaction and mullite formation. For low alumina content (30%) And high alumina content, grain size varies from 0.02xm~0.l (xm. Desulfurization results in the accumulation of residual melt and SiO2, starting at 1050 above the spar, depending on the type of material. Due to desulfurization, the surface of the fiber becomes rough, mainly due to the formation of crystallite grains. The small grain size after heat treatment leads to better heat resistance of the fiber. Table 4 summarizes the phase formation of RCF1260 and RCFOO, at 1000- Heat treatment between 1600 and maintenance for 24 h showed improvement, shrinking at 1400 T to 7.8%. For practical applications, CMS1, CMS2 and CMZS showed a very safe limit of about 50K.
Shrinkage tests for RCF and polycrystalline samples are shown. The classification temperature of the RCF group is between 1290 and MOOT, and the increase in shrinkage in the range above the classification temperature is not so sharp. When the temperature rises, the shrinkage increases significantly, but a short thermal overload does not cause shrinkage that can cause material breakage.
The relationship between shrinkage and temperature of RCF and polycrystalline slag cotton showed the lowest value of polycrystalline slag cotton in all test materials, and the shrinkage was 1.5% at 1600T. Therefore, according to DIN EN1094-3, the classification temperature of polycrystalline slag cotton is 1600. 4.3 Rebound At room temperature, the AES material shows a very small dispersion in the rebound value, as shown. Chemical composition, fiber structure, solid impurity content and production process have little effect on the resilience at room temperature. For RCF, the rebound value is between 80% (RCF1260) and 88% (RCF1400Z). For polycrystalline slag wool, rebound is up to 93%, which is the best of all materials, as shown.
Slightly reduced. Microstructural examination showed that the crystalline phase in AES increased rapidly at this temperature, and the precipitated grains still have a small size and are buried in the melt, and the grown grains do not cause cracks on the surface. Between 1200 and 1250, the CMS1 type shows reduced elasticity and grain size up to fiber size, resulting in low strength values. For the CMS2 type, the rebound value is very close to 1100, and the rebound value of 1200 is slightly increased. This is caused by small-sized grains that are still buried in the melt. After exposure at 12,500 and 1300, the recovery was reduced to 65% and 59%, respectively, due to grain growth. For CMZS, up to 12001, the rebound value is very close to the CMS2 type. At 1300, the rebound drops to 62%. The MS type shows the best resilience, with rebound values ​​of 75% and 71% at 1250 and 1300, respectively. At 1400T: a rebound value of 55%, recrystallization and grain growth lead to a brittle surface.
RCF1260 and RCF1400 in RCF have the lowest rebound, close to 80%. Among all the test materials, polycrystalline fiber showed the best rebound, 93%. For RCF and polycrystalline fiber materials, the temperature rises, back The bomb value is slowly reduced. RCF1260 at 1400, RCF1400 and RCF1400Z at 1500, polycrystalline slag at 150 (Tt, can see a significant reduction in rebound.
XRD measurements and shrinkage and resilience showed consistency with the desulfurization of the fibers used in the study. Since recrystallization has different effects on thermophysical and thermomechanical properties, the relationship between them must be considered, and the classification temperature and the maximum application temperature must be considered.
The temperature range of the crystalline phase changes, such as wollastonite, diopside and cristobalite, is between 1050-1100 for CMS1, CMS2 and CMZS, but the temperature is higher but also reasonable.
When the temperature rises, CMS1 produces a large amount of cristobalite, but since wollastonite has a relatively high strength, the formation of cristobalite is limited. Due to the low silica content, the cristobalite of CMS2 and CMZS forms a lower strength. The fact that the chemical composition results in a lower classification temperature can also be seen as a result of the formation of crystals on the surface of the fiber, which is very noticeable at high temperatures.
For MS, high temperatures result in a high amount of cristobalite. In contrast to CMS1, CMS2 and CMZS, MS may produce a large amount of cristobalite due to its chemical composition.
The main factors affecting the properties of the material are shrinkage and rebound. At 900; recrystallization with crystal phase formation is predominantly silica, and grain growth reduces these properties.
RCF1260 and RCF1400 contain a large amount of alumina, which forms mullite at 1000 hours and overlaps with the formed cristobalite. At 1350T, the cristobalite of RCF1260 has high strength and the cristobalite of RCF1400 has medium strength.
In the -SiO 2 system, 120 (n: can form cristobalite after 24 h of incubation, and the decomposition of zirconia is accompanied by the formation of cristobalite.
For RCF materials, the grain growth is significant and the temperature required for desulfurization results is higher.
The difference in the mineralogical composition of polycrystalline fibers is due to different production processes. From room temperature to 1600T, mullite is the main phase.
The classification temperature of AES resulted in a classification temperature of 1250 for all AES tests. Above this classification temperature, the AES shrinkage value increased dramatically. Even when the furnace is malfunctioning, there is a very small thermal overload above 1250 ft. When the lining uses CMS1, CMS2 and CMZS type fibers, it may cause serious damage to the lining.
Good shrinkage results in a classification temperature of 1600. A rise in temperature over a short period of time above the classification temperature may result in greater shrinkage but will not break the fibers.
Conclusion The solubility of AES slag in the system CaO-MgO-SiO2 (-ZrO and the lower bio-residues (CMS1, CMS2, CMZS) show a small safety margin, which is limited by the increase in classification temperature. Between 50K and 85K. A sharp increase in shrinkage at elevated temperatures results in material breakage. In practical applications, MS type fibers have a wide temperature range with very high shrinkage values.
RCF samples based on alumina and silica have a wide safety margin of 430K (RCF1260, RCF1400). Considering the increase in shrinkage value above 1500, the addition of zirconia results in a lower safety margin for RCF1400Z. In summary, the RCF group has a smaller shrinkage value and slowly increases above the classification temperature.
For polycrystalline slag wool, the safest limit can be seen and the shrinkage value is lowest in all test materials.
The rebound value can be considered to approximate the contraction. Due to recrystallization, above 1000, the AES material shows brittleness, and the recovery of AES given by the rebound resilience value is limited above 1200.
For RCF materials, this value decreases at temperatures >1400:.
All experiments were carried out in an oxidizing atmosphere. The atmosphere contains steam and corrosive components, resulting in lower temperatures for use of high temperature slag, especially AES slag.
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