ELASTIC BEHAVIOR AND CREEP OF REFRACTORY BRICK UNDER TENSILE AND COMPRESSIVE LOADS*

Specimens cut from 9-in, brick of nine brands of firebrick, including two high-alumina, four fire-clay, two siliceous fire-clay, and one silica, were subjected to tensile and compressive creep tests at eleven temperatures from 25° to 950°C., inclusive. The duration of each test was approximately 240 days. Small length changes, independent of stress direction (that is, compressive or tensile), occurred at the lower temperatures. The lowest temperatures at which creep was significant were (a) high-alumina brick, 700° to 850°C.; (b) fire-clay brick, 600° to 700°C.; and (c) siliceous and silica brick, 950°C. Creep results under compressive stress could not be correlated with results under tensile stress. Specimens of different brands, at 950° C. showed greatly different capacities to carry load. Repeated heatings caused growth of silica brick of approximately 0.27%. Moduli of elasticity at room temperature were determined before and after the various heat-treatments and resultant changes were recorded. The changes in moduli were 15% or greater for silica and siliceous brick and 4% or less for the fire-clay brick. The moduli of elasticity at room temperature were approximately 2.7–4.3 × 10⁶ for high-alumina brick, 0.6–1.9 × 10⁶ for fire-clay brick, 0.3–1.7 × 10⁶ for siliceous fire-clay brick, and 0.4 × 10⁶ for silica brick.     

活化煤矸石基免烧砖胶凝性能的研究

对六盘水矿区煤矸石原粉组成进行分析,测定了煤矸石原粉和活化煤矸石粉制备免烧砖的胶凝性能,系统地研究了机械、热、化学及复合活化方式对原状煤矸石活性激发作用。研究表明,六盘水矿区煤矸石属于高铁高砂型煤矸石,活化煤矸石能够显著提高煤矸石基免烧砖的胶凝性能,复合活化效果优于单一活化方式,复合活化的煤矸石能够大幅度地提高免烧砖的胶凝性能,达到JC/T422-91(96)《非烧结普通黏土砖》MU15的标准。     

不同激发剂对煤矸石基免烧砖性能的影响

以六盘水矿区煤矸石为主要原料制备煤矸石基免烧砖.为进一步提高免烧砖的强度,研究了不同激发剂( CaO 、CaO-Na SO4、CaO-CaCl2)对免烧砖性能的影响.研究结果表明,煤矸石基免烧砖强度在激发剂CaO-Na2 SO4的激发作用下有显著提高,最佳掺量为8％ CaO、2％ NaSO4.免烧砖各项性能满足JC/T422-91 (96)《非烧结普通粘土砖》MU15标准要求.这为六盘水煤矸石的开发利用提供了一种技术途径.     

HIGH TEMPERATURE LOAD AND FUSION TESTS OF FIRE BRICK FROM THE PACIFIC NORTHWEST IN COMPARISON WITH OTHER WELL-KNOWN FIRE BRICK1

Seventeen samples of fire-clay brick from the Pacific Northwest have been tested with twenty-seven other commercial brands of fire clay, silica, magnesia, chromite, zirconia, diaspore, silicon carbide and crystalline alumina, as well as china clay and crystalline sillimanite products made at the University of Washington. The tests show that the fire-clay brick of the Pacific Northwest vary considerably in quality. According to the high temperature load test, the majority of the local brick are among the upper grades, some are to be classed with the best fire-clay brick and one equal to the best diaspore brick. The brick tested is not the best which can be made from Pacific Northwest materials, for the kaolins in eastern Washington and northwestern Idaho give opportunity for the production of an all-kaolin fire brick. A method is suggested for testing super-refractory materials under load at high temperatures similar to the standard load test for fire clay and silica brick except that the temperatures are measured by cones, and are raised until 10% linear deformation of the brick is obtained. The rate of heating and soaking varies with the brick under test, and the principles learned from the cone fusion test are used in the application of heat. A numerical value, expressing the area under the cone-shrinkage curve, affords an easy method for comparing the high temperature load resistance of various refractories. The brick which are best able to resist deformation at high temperatures are composed of crystalline materials which have developed a recrystallized bond of the same composition. These are crystalline silica, silicon carbide, corundum and sillimanite, and they resist deformation at temperatures close to their melting points. Amorphous materials like fire clay, diaspore, bauxite or even the very refractory crystalline materials lie chromite and periclase, which depend on amorphous silicates for a bond or are contaminated with silicate impurities. will fail with the softening of the bond of the amorphous impurities. The cone fusion of the brick as a whole can not be depended upon to indicate the resistance to load at high temperatures.     

Permeability of Blast-Furnace Refractories

The permeability of refractories is a governing factor in the deterioration of blast-furnace linings by liquids and gases. Permeability tests there fore were performed on 17 carbon, 11 mullite, 85 castable, and 7 super-duty and 11 high-duty fire-clay brands. The rate of gas flow was measured through a 2-in. cube in three directions by using an improved laboratory permeameter. The range and mean of permeability in centidarcys for each class of refractory were as follows: carbon, 0.3 to 42 (20); mullite, 7 to 158 (48); castable, 0.2 to 43 (4.5); super-duty fire-clay, 28 to 207 (76); and high-duty fire-clay, 33 to 147 (72). The permeability of the different axes of the brick usually varied widely, with the face axis usually exhibiting the lowest values. The improved permeameter should prove to be especially valuable for determining resistance to gas flow and for controlling the quality of refractories.     

Effect of Fused MgO-ZrO_2 Clinker Addition on Thermal Shock Resistance of MgO-ZrO_2 Unfired Bricks

MgO-ZrO2 unfired bricks with ZrO2 content up to 8% at the interval of 2% were prepared,using fused magnesia(MgO:97%)and fused MgO-ZrO2 clinker(ZrO2:14.33%)as starting materials and phenolic resin as binder.The effects of ZrO2 content on thermal shock resistance(TSR)and other properties such as cold and hot modulus of rupture have been investigated.Residual cold modulus of rupture ratio after heating at 1 000 ℃ and quenching by air blowing was adopted to characterize TSR.Addition of the MgO-ZrO2 clinker impr...     

THE WATER SMOKING OF CLAYS1

Experimental Method. —The water smoking behaviors of two plastic brick clays, one shale and one fire-clay were studied by heating 4-in. cubes at different rates, two thermo-elements being buried in the brick and two others placed against the exterior surface. Results of Conclusions. —To save time in water smoking, the ware should be previously dried not far from 100°C, good circulation should be provided in the kiln and the temp. of the interior of the product should not lag appreciably behind that of the kiln. It should be possible to water smoke heavy clay products in 15 hours with heating rate of 20°C per hour.     

COMPARISON OF HOT AND COLD MODULUS OF RUPTURE FOR SILICA BRICK

Purpose of the Investigation .—(1) To obtain relative values for the cross-breaking strength of silica brick at temperatures encountered in coke oven practice. (2) To correlate the hot modulus of rupture test, if possible, with the cold modulus of rupture, or cold crushing test, either of which is cheaper and more easily conducted. This report gives the method of making the test, difficulties encountered and results obtained. The report shows a comparison of cold crushing, cold modulus of rupture and hot modulus of rupture on a series of silica brick made from special mixes, commercially burned. Conclusions .—The modulus of rupture of a silica brick at 1350°C is approximately one-third the strength at atmospheric temperature. For this series it averaged from 130 to 189 lbs. per square inch. Too rapid or eccentric heating up to red heat may cause such weakening of the structure or bond that the brick will break under very low pressure. Cross-breaking strength decreases as the temperature increases. Hot modulus of rupture test appears to give results, in most respects, comparable to the cold test, and for routine testing it would seem advisable to use the cold test since it can be made in much shorter time.     

Mechanical Properties of Chemically Strengthened Glasses at High Temperatures

Young's modulus, shear modulus, and modulus of rapture for two chemically strengthened glasses were determined at high temperatures. The Young's modulus and shear modulus decreased with increasing temperature, with a sharp inflection slightly above room temperature. The region of inflection indicated an internal friction peak. For comparison Young's modulus and shear modulus were determined as a function of temperature on a thermally tempered soda-lime-silica glass and on a semitempered borosilicate glass. Curves of these moduli, in contrast to those for the chemically strengthened glasses, did not reveal regions of inflection. The modulus of rupture is not affected by short exposure to heat up to 260°C., but decreases appreciably when exposed to temperatures above 204°C for 200 hr or more. Deflection measurements at room temperature showed that the two chemically strengthened glasses had about five times as much delayed elasticity as did thermally tempered soda-lime-silica glass.     

Effect of Temperature on Modulus of Elasticity of Porcelain Enameled Steel

The modulus of elasticity of porcelain enameled steel specimens was measured at different temperatures. A dynamic test (the sonic method) was used for the determination of the modulus of the metal and of the metal-enamel composites. Equations and constants are presented by which the elastic constant can be calculated for any enamel thickness in the temperature range from room temperature to 500° C. Graphs are also presented to show the relationship of the modulus of elasticity, temperature, and enamel-metal thickness ratio for ground-coated, white cover-coated, and direct white enameled steel specimens.     

Random glass mat reinforced thermoplastic composites. Part I: Phenomenology of tensile modulus variations

The mechanical properties of random continuous glass mat reinforced composites, as determined by standard tensile tests, are known to have a very large scatter. To understand this scatter, new test procedures were developed to map the local tensile elastic moduli in a large plaque at 12.7-mm (½-in) intervals. Surprisingly, the tensile modulus in these materials can vary by a factor of two over the 12.7-mm distance. The elastic modulus is shown to vary by a factor of three in a 150 × 305-mm (6 × 12 in) plaque. Expressions have been obtained for the average moduli measured by tensile and bend tests. These expressions have been used to compare measured flexural moduli with values predicted by using measured tensile moduli.     

Correlation between the dimensionality and the constants of elasticity of rare-earth doped borate glasses

This work was devoted to explore the correlation between the dimensionality and the computed theoretically constants of elasticity of borate based glasses doped with rare-earth oxides. The dimensionality of the glassy network has been calculated in terms of the d ratio which is equal to 4 C ₄₄/K _e and discussed in terms of the cross-link density and number of network bonds per unit volume of these glasses. Constants of elasticity were calculated in terms of the bond compression model and the Makishima-Mackenzie model. The average cross-link density, the number of network bonds per unit volume, the average stretching-force constant, and the ratio of the estimated bulk modulus (K _bc) to the experimentally determined (K _e) have been calculated and discussed in terms of the bond-compression model. Young??s modulus, the packing density, and the dissociation energy have been calculated and analyzed in terms of the Makishima-Mackenzie model. The results showed that the computed elastic moduli and the dimensionality of the borate glasses containing La₂O₃ or Gd₂O₃ are strongly dependent on the concentration of the structural units of the constituent oxides and types of bonds between these units.     

Reaction Between K2O and Al2O3-SiO2 Refractories as Related to Blast-Furnace Linings

An examination was conducted to determine the mechanism of peeling of fire-clay brick in the low-temperature region of a blast furnace where 3 to 10% K₂O is the principal contaminant. In laboratory tests, as-received high-duty and superduty fire-clay brick and 70% alumina brick treated with KCl-K₂CO₃ mixtures showed no peeling at a temperature of 1600°F. Cracks were found in high-duty brick that were treated with KCN at 1500°F. under partially reducing conditions. X-ray diffraction studies of mixtures of crushed brick and K₂CO₃ indicated the formation of leucite (K₂O.Al₂O₃.4SiO₂) and kaliophilite (K₂O.-Al₂O₃.2SiO₂) at temperatures below 1700°F. These latter data, confirmed by specimens from used blast-furnace linings, showed that silica is the first constituent attacked by alkali. Since the formation of leucite and kaliophilite in fire-clay brick is the probable cause of peeling, the increased reaction of silica, in a dense Al₂O₃.SiO₂ refractory of higher silica content than fire-clay brick, should confine the alkali attack to the surface of the brick in low-temperature applications.     

PROGRESS REPORT ON INVESTIGATION OF FIRECLAY BRICK AND THE CLAYS USED IN THEIR PREPARATION1

This is a progress report of an extensive study of fire clays and fireclay brick. It includes the results of a preliminary study of clays representative of those used in the manufacture of refractories throughout the United States. Chemical analyses and a summary of physical tests are given of both fire clays and the brick manufactured from them. The thermal expansion behavior of the fire clays fired at 1400°C and those of the fire brick “as received” from the manufacturer and also after firing at 1400°C, 1500°C, and 1600°C were studied and the materials classified into groups having characteristic thermal expansions. The moduli of elasticity and rupture were determined at 20°C, 550°C, and 1000°C. The resistance of the brick to spalling in a water-quenching test is expressed in an empirical relation correlating the elasticity, strength, coefficient of expansion, and percentage of grog used in compounding the brick batches. Data are presented on individual bricks made by the same manufacturer showing probable reasons for great differences in the number of quenchings required to cause spalling in the water-dip test.     

Elastic Properties of Polycrystalline Yttrium Oxide, Holmium Oxide, and Erbium Oxide: High-Temperature Measurements

The Young's and shear moduli of polycrystalline yttrium oxide, holmium oxide, and erbium oxide were determined from room temperature to 1000°C using the sonic resonance technique. The bulk modulus and Poisson's ratio were computed as functions of temperature for each oxide. The Young's, shear, and bulk moduli decreased linearly with increasing temperature, whereas Poisson's ratio remained constant. The first and second Grüneisen constants, γ and δ, were calculated from the bulk modulus data and shown to be virtually independent of temperature. The Soga-Anderson equation adequately described the bulk modulus data for each oxide.     

复合抗氧化剂对Al2O3-SiC-C砖性能的影响

以均化矾土、板状刚玉、碳化硅、石墨为主要原料,利用酚醛树脂作为结合剂,研究了复合抗氧化剂(硅粉、铝粉、碳化硼)的引入形式及加入量对Al2O3-SiC-C砖的性能影响.结果表明:添加复合抗氧化剂可提高Al2O3-SiC-C砖的高温抗折强度,随铝含量的增加,对提高高温抗折强度的提高越明显;抗氧化效果从强到弱依次为:添加碳化硼的复合抗氧化剂>复合铝硅抗氧化剂>金属铝>金属硅;在复合抗氧化剂中引入碳化硼能够有效的提高Al2O3-SiC-C砖的抗渣侵蚀性能及热震稳定性.     

Characterization of Porosity in Porcelain-Bonded Porous Alumina Ceramics

A water removal method was used to determine pore sizes in highly porous large-pore-size specimens. The maximum, minimum, and equivalent pore sizes, as well as complete size distributions (number of pores vs pore sizes), were obtained. The results agree with those obtained using a mercury porosimeter. Characterizing parameters such as permeable porosity, labyrinth factor, and structure factor were estimated from the water removal porosimeter data. Electrolytic resistance was measured to determine the tortuosity and inert porosity. A physical meaning of Archie's law which correlates the formation resistivity factor with porosity is also given. Sonic Young's and shear moduli depended on both the porosity and particle sizes. The Young's modulus was linearly related to the modulus of rupture.     

纤蛇纹石纤维增强轻质多孔硅藻砖

以硅藻土、纤蛇纹石、高岭土为原料,通过压力成型和高温煅烧制备了轻质多孔的硅藻砖.继而系统研究了这种硅藻砖的容重、吸水率、显气孔率、断裂模数、吸放湿等物理性能,并采用X射线衍射和扫描电镜对硅藻砖的结构与形貌进行了表征分析.结果表明:随着纤蛇纹石含量以及煅烧温度的增加,硅藻砖的吸水率、孔隙率逐渐下降,但是断裂模数显著增加.当纤蛇纹石含量为10wt%、煅烧温度为900 ℃时,硅藻砖的断裂模数超过10 MPa,容重仅为1.18 g/cm3,显气孔率高达47.97%,具有高强、轻质、多孔特点,并兼具良好的吸放湿性能.     

Manufacture and testing of tar-bonded dolomite-magnesite brick

Conclusion The use of calcined dolomite powder without supplementary grinding, preprocessed with fused coal-tar pitch, for making unfired goods with a tar bond makes it possible to produce refractories with a high resistance to hydration and with other satisfactory properties.The testing of dolomite-magnesite brick with a tar bond in the lining of a ladle, imitating a converter with oxygen blow, showed that it had a high wear resistance; the wear intensity is no different from that of periclasespinel brick.Tarred dolomite-magnesite goods with metal cladding showing certain advantages in service over unclad products, need to be tested in large quantities, especially in the charging side and in the throat of the lining of the converter.To obtain data more reliably reflecting the life of dolomite-magnesite brick with a tar bond in converters working with oxygen, the authors should carry out repeat tests of these refractories in conditions excluding the long intermelting downtime-Editors.     

Dynamic and Static Tests for Mechanical Properties of Fired Plastic Refractories and Other More Resilient Materials

An apparatus for loading brick-sized specimens and a sensitive deflectometer are described. For a resilient material, the dynamic test, the static shear-free transverse test, and the static shear-corrected transverse test gave the same modulus of elasticity. The resilient materials were dense firebrick, glass, steel, and plaster. The elementary shear correction was satisfactory for the correction of the deflections of transverse test specimens having length-to-depth ratios ranging from 3.2 to 7.2. The dynamic modulus of elasticity, the static secant modulus of elasticity, and the static modulus of rupture were obtained for nine brands of heat-treated plastic refractories. The load-deflection curves obtained from static tests on these materials indicated plastic deformations ranging from nil to 19% of the truly elastic deformations calculated from the results obtained by the dynamic method of test. The differences in the extensibilities calculated from the static and dynamic methods of test were equivalent to these plastic deformations. For studies of thermal spalling, the static extensibilities were preferred because they approximated the strain at rupture.