COMPARISON OF REPEATED REHEAT TESTS OF VARIOUS GRADES OF FIREBRICK WITH SERVICE RESULTS

Representative brands of Navy-approved class A brick (60% alumina), class B brick (superduty), and special firebrick (in a price group above the 60% alumina brick) were installed in a naval boiler operating continuously at the Naval Boiler and Turbine Laboratory. The permanent volume change of the various brands, subjected to repeated reheat tests at 2912°F., is compared with their service life.     

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.     

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.     

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 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.     

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.     

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.     

PROGRESS REPORT ON SPECIFICATIONS FOR REFRACTORIES1

Following a conference with producers and consumers of refractories, a series of proposed laboratory tests were conducted on forty-one commercial brands of brick. The work included reheating at 1450° and 1400°C, quenching, load test, fusion point determination, chemical analyses and petrographic examination. Results of tests are presented, They will be more fully discussed when correlated with service tests now under way.     

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.     

THE EFFECT OF RED HEARTS IN FIRE CLAY BRICK1

Laboratory tests made on two brands of fire clay brick indicate that red hearts, which are normally considered as being detrimental, add to both the hot and cold strength and would not be objectionable except in furnaces operated at a low temperature, and in which spalling is an important item. Results of load, reheating and spalling tests are given, together with porosity and iron oxide determinations. A short discussion of the causes of red hearts is also included.     

Refractory Castables: II, Some Properties, and Effects of Heat-Treatments

Differential thermal analyses were made and weight losses were determined up to 1000°C. for a domestic and an imported high-alumina hydraulic cement after hydrating. Refractory castables were prepared in the laboratory with these two cements and fire-clay brick and flintclay aggregates. Compressive, transverse, and tensile strengths of these castables were obtained after heating 4,8, and 12 months at 300°C. and at other temperatures up to 1350°C. for shorter periods of time. Sixteen commercial brands of castables were tested for sieve analysis, P.C.E., and flow, on the material "as received". The three types of strengths of the sixteen castables also were determined after treatments at 95% relative humidity and after heating at temperatures up to 1350°C. Some information on porosity and structural and linear changes after the heat-treatments was obtained.     

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.     

用后镁碳砖的再生研究

以用后的废镁碳砖为原料,经过拣选、除渣、破碎、除铁、均化和水化等处理后,制成再生镁碳砖。以97%的用后镁碳砖料再生的镁碳砖的各项性能接近或达到新镁碳砖的水平;以80%的用后镁碳砖料再生的镁碳砖用在300t钢包渣线上,在有20炉次LF处理的情况下,其使用寿命达到82炉次,渣线侵蚀速度为每炉1.28mm。使用结果证明,这种再生镁碳砖达到了同期使用的由电熔镁砂和石墨为原料而生产的新镁碳砖的水平。     

高温炭黑反应炉炉衬选材分析

从抵抗高温气流冲蚀、抗炭黑粒子化学侵蚀和抵抗炉气杂质化学侵蚀等三个方面对高纯刚玉砖、刚玉莫来石砖、铬刚玉砖、高铬砖和氧化锆砖作了分析比较。分析认为,在燃烧室和喉管采用高纯刚玉砖和铬刚玉砖,反应段和急冷段采用高纯刚玉砖较好;而氧化锆砖在整个反应炉各段使用都是可行的。高铬砖因抗炭黑粒子化学侵蚀性差,不适合使用于高温炭黑反应炉     

Production of ladle and checker brick from Arkalyk raw material

Conclusions Ladle brick with a considerably longer life than conventional chamotte ladle brick is manufactured from Arkalyk rock without clay additions.Checker brick made of high-alumina chamotte and Latnaya clay is recommended for the checker work of regenerators; less melting dust was noted than in chrome-magnesite brick checkers.The basic variety of Arkalyk rock is suitable for the production of chamotte ladle brick without clay additions; the life of this ladle brick is as long as that of conventional brick used at Borovichi Combine. Increased compression would allow the production of higher-strength brick.     

Properties of Magnesia-Hercynite Brick

Properties of magnesia-hercynite brick were studied. The coatability, thermal shock resistance, corrosion resistance to cement clinker and thermal conductivity were compared with those of magnesia-chrome brick and magnesia-spinel brick used widely in sintering zone of cement rotary kiln. The result shows that magnesia-hercynite brick is better than magnesia-chrome brick in thermal chock resistance and corrosion resistance to cement clinker, is similar to magnesia-chrome brick and is better than magnesia-spinel brick in coatability and thermal conductivity.     

Determination of the Diffusion Coefficient of Water in Brick with a Simple Mass Distribution Technique

A method is presented for the determination of the diffusion coefficient of water in brick. A brick is sealed on five sides to ensure one-dimensional water transport. The wet brick is hung with the utmost ends each from a balance. This way, not only the mass of the water in the brick is measured, but some information is obtained about the mass distribution inside the brick. The brick used in this study appears to be quite inhomogeneous. This is incorporated in the model with an inhomogeneity constant. It needs further research if this parameter depends on the water concentration in the brick.     

炼钢电炉顶用硅线石砖的生产与使用

以硅线石为主要原料生产的硅线石砖抗渣侵蚀平均速度2．639mm／炉，比电炉顶高铝砖降低31．8％；单位损耗厚度承受的急冷急热次数平均值：硅线石砖为1．216次／mm，电炉顶高铝砖为0．827次／mm。该砖可明显提高电炉盖的使用寿命。     

基于砖含量的再生砖混粗骨料分类研究

针对目前我国再生骨料分类标准适用范围窄,难以指导高砖含量再生骨料综合利用的问题,探究了砖含量对再生砖混骨料吸水率、表观密度和压碎指标等方面的影响规律,并结合现有文献资料统计分析,建立了砖含量与吸水率和压碎指标之间的一般线性关系公式。提出将砖含量作为主要分类控制指标,表观密度、吸水率和压碎指标作为技术控制指标的砖混骨料分级分类新方法。这种方法能够有效完善现有技术标准,使之与再生砖混骨料性质相适应,更加有效地指导砖混骨料在混凝土工程中的资源化利用。