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.     

COMPARATIVE TESTS OF SOME AMERICAN AND GERMAN FIRECLAY BRICK1

The Bureau of Standards has recently completed a short investigation comprising comparative tests of five brands of German-made brick and six brands of American-made brick. The results indicate that the Ge man-made brick are practically the equal of the American brick.     

INVESTIGATION OF ABRASION RESISTANCE OF VARIOUS REFRACTORIES*

This paper describes a new abrasion test for re-fractories consisting of a controlled sandblasting operation wherein various brands of brick were tested. Graphs show correlations for abrasion loss per hour against other properties for the brands tested. Data and charts which compare this abrasion test with the A.S.T.M. rattler test for paving brick are also included.     

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.     

冲击参数对氧化铝基耐火材料常温耐磨性的影响

参照GB/T18301《耐火材料常温耐磨性试验方法》,分别以标准碳化硅砂(36#)、电熔白刚玉砂(36#)和石油支撑剂用陶粒为磨损介质,采用不同压力(300kPa、448kPa和600kPa)的压缩空气和不同量(1kg、2kg)的磨损介质对普通高铝砖(LZ-65和LZ-75)、高炉用高铝砖、磷酸盐结合高铝砖、高纯刚玉砖、刚玉莫来石砖、铬刚玉砖、赛隆结合刚玉砖、微孔刚玉砖和塑性相复合刚玉砖等10种氧化铝基耐火材料进行了磨损实验。结果表明:(1)随着冲击气体压力的增大,10种材料的磨损量都增加,但由于这些材料在组成和结构上的差异,其磨损量增加的幅度存在明显差异。(2)由于磨损介质的颗粒形状和体积密度不同,在相同的冲击气体压力下,磨损介质的流动速度不同,对材料的磨损量也不同,其中,采用碳化硅时磨损量最大,采用白刚玉时次之,采用陶粒时最小。(3)当磨损介质碳化硅砂用量增加1倍时,材料的磨损量增加,但不同材料的磨损量增加幅度不同,其中微孔刚玉砖和磷酸盐结合高铝砖分别增加了1.84倍和1.26倍,而高纯刚玉砖和高炉用高铝砖增加的不足0.4倍。(4)耐火材料的常温耐磨性能取决于其强度和结构的致密性,强度和致密度较高的材料耐磨性能较好。     

EFFECT OF REDUCING GASES ON THE TRANSVERSE STRENGTH OF FIRECLAY BRICKS1

It was reported that fireclay brick, when heated in the presence of carbon monoxide, were disintegrated by the progressive deposition of finely divided carbon at the “iron spots” in the brick. The conditions necessary for the occurrence of this phenomenon were not definitely known, although the known reversibility of the catalytic reaction around 650°C and the outcome of small scale experiments indicated that disintegration would not occur above this temperature. To obtain more definite information on this score, the effect of city gas at 550°C and 1100°C on the transverse strength of three brands of fireclay brick was determined. No significant changes in strength occurred at 1100°C. At 550°C two of the brands suffered very significant decreases in strength, but the other brand was unaffected, although it had the highest iron content.     

A Highly Active Ag/Alumina Catalytic Converter for Continuous HC-SCR During Lean-Burn Conditions: From Laboratory to Full-Scale Vehicle Tests

A common-rail diesel vehicle was equipped with a full-scale Ag/alumina catalytic converter. The converter consisted of several Ag/alumina bricks, with free space in between each brick to fulfil important gas phase reactions. An oxidation catalyst was placed at the end of the converter to remove formed CO and unburned HC. High conversion levels of NO _x , around 60%, were recorded at several speeds and loads using additional HC (diesel) injection corresponding to 2–5% fuel penalty.     

AN X-RAY STUDY OF THE TOUGHNESS OF PAVING BRICK*

X-ray diffraction photographs of paving brick were compared with those of pure materials. The most important result obtained in this work is the discovery of a line in the X-ray diffraction pattern of paving brick which is characteristic of high-grade shale paving brick. This line, produced by an undetermined crystal, is more intense in the tougher than in the weaker brick. The line falls at 2.03 ± 0.01 Ångström units. A further result of this investigation is the proof that cristobalite, mullite, sillimanite, alumina, and cyanite are not present in the paving brick studied. This also shows that mullite is not produced in ceramic materials at the relatively low temperature at which paving brick are fired.     

COLD CRUSHING STRENGTH OF FIRE BRICK1

Data on cold crushing strength in three directions, viz., flat, edge, and endwise of six brands of fire brick are given. Transverse strength data of all these brands are also given. Porosities of all the brick used in these tests were determined by the air-expansion method. The purpose of the investigation was to find whether it is possible to translate the values obtained for crushing strength of fire brick in one direction (flat) into values for the other directions (end and edge); to determine whether transverse strength data can similarly be transformed to crushing strength data and vice versa and whether porosity and crushing strength of fire brick are correlated. The data herein presented do not show the existence of any such simple mathematical relationship between the different properties of the brick. A new capping material, a mixture of sand and molten sulphur, was used for the crushing tests, and was found to be more satisfactory than the other materials commonly used for the purpose. It is recommended that in reporting crushing strength data of fire brick, the brick be tested on end.     

A COMPARISON OF THE UNIFORMITY OF STRENGTH AND TEXTURE OF FIRE BRICK MADE BY DIFFERENT PROCESSES1

By assuming that the “deviations from the average” of the strengths and permeabilities of individual bricks of any one brand are governed by the laws of chance, a comparison of the uniformity of strength and texture of a number of brands of brick made by different processes is obtained. Of the brands examined, those made by the stiff-mud process are found to be more uniform in strength and less uniform in structure than those made by the dry-press process. The hand-made bricks show quite a variation in both strength and texture, whereas one brand of brick made by a semi-dry process (English type machine) shows good uniformity in both strength and texture.     

Technology of Spinel-Bonded Periclase Brick

This study covers the development of a new basic brick with outstanding resistance to load deformation, slagging, and spalling. This brick is made of 92% high-purity periclase and 8% high-purity alumina. During firing for a ceramically bonded brick or in service for a chemically bonded brick, the fine periclase and alumina react to form a spinel (MgO.Al₂O₃) bond. As the magnesia content of the periclase is increased, the properties of this brick become more outstanding.     

氧化铝微粉加入量对低碳镁碳砖性能的影响

以电熔镁砂、石墨、金属Al和氧化铝微粉为主要原料,热塑性酚醛树脂为结合剂,制备了w(C)5%的低碳镁碳砖试样,研究了氧化铝微粉加入量(其质量分数分别为0、3%、5%、7%、9%)对低碳镁碳砖的常温物理性能、抗热震性和抗氧化性的影响。结果表明:(1)随着氧化铝微粉加入量的增加,低碳镁碳砖试样的体积密度、常温强度和高温强度均先升高后降低,显气孔率则先降低后升高;抗热震性和抗氧化性随微粉加入量的增加呈先改善后变差的趋势;其中,微粉加入量为5%的低碳镁碳试样综合性能最好。(2)低碳镁碳砖试样性能的改善主要是由于加入的氧化铝微粉和MgO在高温下原位反应生成连续分布的尖晶石,增强了基质的陶瓷结合;但氧化铝微粉加入量过大时,由于大量原位反应引起材料产生过大的体积膨胀,会导致基质结构疏松,从而恶化镁碳砖的性能。     

Reaction of Vaporized Sodium Sulfate with Aluminous Refractories

A method was devised and tested whereby the action of an alkali salt, in the vapor or in the liquid state, on refractory materials may be studied under controlled conditions of temperature and pressure. Using Na₂SO₄, the progress of reaction was followed by (1) change of weight, (2) determination of SO₃ by precipitation, and (3) determination of Na₂O by flame photometer. The materials studied were a commercial-grade high-alumina brick (88% Al₂, 11 % SiO₂) * and fused crystalline alumina (99.5% Al₂O₃).
The dissociation of sodium sulfate, reacting in contact with high-alumina refractory materials, is speeded more by the presence of SiO₂, probably as the compound mullite, than by crystalline alpha-alumina. The ultimate product in the commercial brick is probably nephelite, NaAl-SiO₄; in the alumina, sodium alumina, NaAlO₄.
Exposure at 1200°C. in a vacuum of 150 μ of mercury approximately doubles the rate of deposition of sodium sulfate on the brick studied and adds one-third to the rate on fused alumina, as compared with the rate in air at atmospheric pressure.     

THE LABORATORY TESTING OF ALUMINOUS REFRACTORIES1

Eight brands of high alumina refractories and two brands of fire clay refractories, which are used by the trade under conditions of service requiring resistance to the corrosive action of lime and cement clinker at high temperatures, were subjected to standard and modified laboratory tests for high grade refractories. Data obtained indicate the results which may be expected in the technical examination of this type of product.     

Bonding mechanism and performance of rectorite/ball clay bonded unfired high alumina bricks

In this study, the bonding mechanism and normal/high temperature performance of rectorite clay or ball clay bonded unfired high alumina bricks were investigated by using different techniques (XRD, TG-DSC, SEM, particle size distribution and rheology). The results showed that clay particles are separated into layer structural units in water due to the hydration swelling and electrostatic repulsive force, and rectorite layer structural units have larger aspect ratio than ball clay. Rectorite layer structural units form band-type structure with “face to face” after drying results in better bonding performance than ball clay (card-house structure with “edge to face”). The cold crushing strength of 9% rectorite/ball clay bonded unfired high alumina bricks after firing at the dehydroxylation temperature for 3 h reach 71 MPa and 50 MPa, respectively, and which can satisfy the strength requirement for the transportation and use of most high alumina bricks. The secondary mullitization and lower liquid phase content of ball clay bonded unfired high alumina brick under high temperature cause it has higher refractoriness under load and lower linear shrinkage than rectorite clay bonded brick. The T_0.6 refractoriness under load of 9% rectorite/ball clay bonded unfired high alumina brick are 1262.6 °C and 1580.3 °C, respectively. Thus, the 9% ball clay bonded unfired high alumina bricks have wider service temperature range than 9% rectorite bonded bricks.     

PLANT INVESTIGATION OF VARIABLES AFFECTING COLOR OF SILICA BRICK

The data in this report were obtained during the years of 1923, 1924, and 1925. Among the topics studied were the effects of color in silica brick resulting from the lime, iron oxide, and alumina content of the brick and from varying drying and firing conditions. The effect on color of sulfur gases from coal and the time-temperature relations are also discussed. The lime-alumina ratio, the, iron oxide content of the brick, and setting and firing conditions are concluded to be the most significant factors related to the color of the product.     

USE OF THE SIMULATIVE TEST FURNACE AS A MEANS OF MAKING COMPARATIVE TESTS OF FIRE BRICK1

The Navy Simulative Service Test for refractories is described, specifications for the test and the furnace used being given. The simulative service furnace has found application in making comparative tests of different brands of refractories, development of and improvement of standard fire brick, and as a control test for maintaining quality of the product.     

ARTIFICIAL SILLIMANITE AS A REFRACTORY1

Alumina-silica mixtures were prepared by fusing quartz, china clay, fire clay, and alumina in the electric furnace. When alumina is less than 68%, crystalline sillimanite (3Al₂O₃.2SiO₂) with glass is produced. This material is not very resistant to loads at high temperatures because of the early fusion and internal lubricating action of the glass surrounding the crystals. Above 68% alumina, crystalline corundum appears am1 the glass is practically absent. This latter composition is very resistant to high-temperature loads when ail interlocking, recrystallized bond is developed. This material is not affected materially by acid slags, but it cannot resist basic slags. However, the dense structure of a brick of material above 68% Al₂O₃ causes less slagging in a laboratory bath test than silica brick. The laboratory made sillimanite-corundum brick withstood higher temperatures than the best silica, magnesia, chrome, fire clay, or zirconia brick even though the cone of fusion of the former is less than that of MgO, Cr₂O₃ or ZrO₂. More and better service tests with a large number of brick fired in large kilns is needed to follow up this laboratory work.     

THE RELATION OF STRUCTURE AND COMPOSITION TO THERMAL EFFICIENCY OF REFRACTORIES WHEN USED IN REGENERATORS1

This study shows the relative rates of heat transmission in typical clay, silica, diaspore, fused alumina and silicon carbide refractories, when used as checker brick. It is shown that by lowering the porosity of checker brick an increase in efficiency is obtained by virtue of its greater heat capacity, which is a function of the weight and specific heat of the material. The glazing of a clay brick does not appreciably impair its efficiency in regeneration, as is sometimes thought, as shown by experiment and as explained by the fact that the greatest part of the heat leaves the surface of the brick by convection and this is affected only by the surface area, which is not appreciably changed by glazing.