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.     

STRENGTH OF BRICK IN TENSION1

A self-aligning grip for use in testing brick in tension is described. Values for the tensile strength of several types of brick are given. Comparison is made between the transverse and tensile strength of the brick. The conclusion is that the tensile strength is closely related to the transverse strength.     

THE RELATION OF BRINELL HARDNESS AND TRANSVERSE STRENGTH TO THE COMPRESSIVE STRENGTH OF BUILDING BRICK1

This paper reports the results of Brinell hardness determinations on twenty-five makes of brick together with their transverse and flat compressive strengths. These data indicate that though there is somewhat better correlation between Brinell numbers and flat compressive strength than exists between transverse strength and flat compressive strength, yet the relation is not sufficiently exact to permit the accurate estimation of flat compressive strength from a measured Brinell number.     

OUTLINE OF REFRACTORY REQUIREMENTS FOR THE IRON AND STEEL INDUSTRY1

One of the greatest obstacles to the development of better refractories for the iron and steel industry has been the failure of the iron and steel men to give refractory manufacturers accurate detailed analysis of chemical, physical and thermal conditions to which the refractories are to be subjected. This paper summarizes briefly some of the conditions to be encountered in the major processes. Blast furnace refractories may be divided according to requirements as follows: Hearth and Bosh brick should withstand the scouring action of molten iron and acid slag at temperatures around 1800°C. Inwall brick should be impervious to hot, reducing gases, should resist the sand blast action of the from particles of ore carried by the gas, should have a low coefficient of thermal expansion and should possess sufficient compressive strength to support the weight of the upper part of the furnace. Top brick should be as dense and resistant to abrasion as possible. Downcomer, Dustcatcher and Gas Line brick should be dense and resist sand blast action of gas heavily laden by particles of charge. Hot Blast Main and Bustle Pipe brick should be of low heat conductivity. Hot Blast Stove brick should not vitrify at 900°C, should have maximum capacity for absorbing and giving off heat, and be of high compressive strength. The by-product coke oven is becoming a big factor in the refractory fields and has major requirements as follows: Canals and Ovens require brick of high thermal conductivity which will resist sudden changes in temperature and will not be affected by reducing gases at high temperatures. Checker brick should have great capacity for absorbing heat. Bessemer converters require brick resistant to slag at temperatures from 1600° to 1700°C, the nature of the slag being determined by whether the process is acid or basic. Requirements for open hearth furnaces are as follows: Roof brick (both acid and basic furnaces) must not only be capable of maintaining an arch but should withstand as much as possible the action of iron oxides at temperatures of 1800°C. Checker brick (both acid and basic furnaces) should possess a maximum capacity for absorbing and giving off heat, and a minimum chemical affinity for oxides from charge. Ports (both acid and basic) must withstand the action of slag splashes, also direct action of flame. The hearth of the furnace consists of several courses of brick (acid or basic depending on the process) upon which is built the hearth proper by means of many layers of crushed refractory of the same nature. This crushed material must frit together at high temperatures without excessive softening.     

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.     

THE COMPRESSIVE AND TRANSVERSE STRENGTH OF BRICK1

This paper reports the compressive strength flat and on edge and the transverse strength of twenty-seven makes of brick covering a range of conditions in method of manufacture and degree of firing. The attempt is made to correlate the variation in ratios of these different measures of strength with the various structural features of the check.     

EFFECT OF WEATHER UPON THE STRENGTH OF REFRACTORY BRICK1

Magnesia and silica brick should be protected from the action of the weather. Open textured fireclay brick (usually having end cold crushing strengths of less than 1500 pounds per square inch) should be afforded protection from the action of the weather. Finely ground, dense, hard-burned firebrick , especially those of medium or low refractoriness. may be exposed to the action of weather with a reasonable amount of safety. These are usually made from one clay which is shaped on a dry press or auger machine and have an end cold crushing strength approximating 5000 pounds per square inch.     

CORRECTION OF AN EXTREME CASE OF CRACKING IN THE DRYING OF BRICK1

I. In the manufacture of stiff-mud brick from a highly colloidal clay of low permeability to water, drying breakage was extremely high even though the drying was conducted at a very slow rate under high humidity conditions. Laboratory investigation yielded two methods of correcting the faults: (1) Preheating the clay for half an hour at a temperature between 400 °C and 500 °C increased the permeability to such an extent that brick made from the preheated clay could be dried rapidly without cracking. (2) Coagulating chemicals, such as aluminium chloride, ferric chloride, sodium chloride, and hydrochloric acid, in conjunction with moderate additions of grog, increased the permeability and thus improved the drying properties of the clay. II. Plant scale tests using ferric chloride, sodium chloride, and grog resulted in the production of brick which could be dried safely in a reasonable time. The fired brick were improved in quality as to strength and color. III. The chemical treatment of the clay using 1% ferric chloride and 0.5% sodium chloride with 10 to 15% grog was adopted for plant operation and resulted in increased production, lower cost of manufacture, and improved quality of product.     

A STUDY OF THE FACTORS INVOLVED IN THE SPALLING OF FIRE CLAY REFRACTORIES WITH SOME NOTES ON THE LOAD AND REHEATING TESTS AND THE EFFECT OF GRIND ON SHRINKAGE1

Of the three factors, elasticity, coefficient of expansion and rate of temperature change, which affect spalling, the former is by far the most important. Only small differences are found between fire clay mixtures of widely varying structure and composition in the rate at which they change in temperature under like conditions of heating. The coefficient of expansion varies directly with the silica content and differences in this respect of large order were found. However, the spalling on the particular mixtures tested varied almost inversely as the coefficient of expansion. This apparent discrepancy is explained on the basis of greater elastic properties of the brick which had high expansions. The elasticity may be varied between wide limits and is sufficiently important as to overbalance the effect of greater expansion. This property is accordingly the one upon which efforts directed toward the development of non-spalling brick should be centered. It was discovered that a plastic deformation could be obtained at as low a temperature as 635°C. This gives the effect of elasticity and undoubtedly has considerable influence on spalling at the higher temperature ranges. Results are given for a number of load tests which show clearly the importance of hard firing. The secondary expansion of brick made from Pennsylvania flint clay is shown to be influenced by the temperature of reheating, as well as its rate. Detailed results showing the effect of grind and firing on the finished size of the brick included in the investigation are also given.     

THE EFFECT OF DRYING TEMPERATURE ON THE QUALITY OF PAPER

The effect of drying temperature on the optical properties of various papers was investigated. For paper from mechanical pulp, it was found that as drying temperature increased, light scattering coefficient decreased leading to lower brightness. The decrease in light scattering was associated with improved strength properties even at constant sheet density, and was attributed to increased bonding. These effects were not observed for chemical pulp furnishes.     

USE OF ALUMINUM METAL IN THE CERAMIC INDUSTRY I,PROPERTIES OF REFRACTORIES PRODUCED WITH MIXTURES OF ALUMINUM,FIRE CLAY,AND GROG*

The addition of aluminum metal powder to fire-clay-grog mixtures greatly increased the strength of the fired brick as a result of an aluminothermic reaction between the metal and the silica in the clay and grog. Because the reaction takes place at 930°C. and causes the temperature to rise rapidly, it is necessary to heat these refractories only to 930°C. to produce hard, well-fired brick. Such products have a high load-carrying capacity at furnace temperatures and also a fair spalling resistance.     

TRANSVERSE TESTING FURNACE*

An electric furnace is described, designed for determining the transverse strength of 9-in. brick to temperatures as high as 1500°C. It is especially useful when a large number of brick are to be tested because the samples, which have been preheated in a second furnace, may he easily introduced and withdrawn while the furnace is held at breaking temperature.     

RELATION OF CRUSHING STRENGTH OF SILICA BRICK AT VARIOUS TEMPERATURES TO OTHER PHYSICAL PROPERTIES*

The failure at elevated temperatures under constant load for silica brick is reported using the Iupuy load test apparatus. The crushing strength at 1500°F, 1800°F. 2100°F, and 2400°F is recorded, as well as the crushing strength at room temperature. The size of test piece utilized normally was 1 by 1 by 2′/2 inches. A definite relationship is shown to exist between the strength at room temperature and that at elevated temperatures. The effect of variation in lime content, bats content, and fluxes is also reported. Data were obtained on brick made from three different quartzites. Additional physical data are reported to give information concerning the properties of the brick tested.     

THE INFLUENCE OF GRIND AND BURN ON THE CHARACTERISTICS OF SILICA BRICK1

Finer grinding improves the appearance of the brick and increases their strength somewhat but not in any marked degree, within the commercial limits of grinding. A grinding of from 15 to 20 minutes seems most desirable. The time of grinding does not affect the porosity appreciably. The firing temperature is the principal factor governing the final strength and also the permanent residual expansion. The maximum temperature cone 19, yielded the highest strength and the lowest expansion.     

USE OF ALUMINUM METAL IN THE CERAMIC INDUSTRY: II,EFFECT OF COATING INSULATING FIREBRICK WITH ALUMINUM-FIRE-CLAY MIXTURES*

After insulating firebrick are reheated in service, many of them contract too much and develop large open shrinkage cracks. By first applying to the surfaces a 0.035-in. coating composed of aluminum and fire clay, these brick usually remain intact and constant in size when they are reheated. The coating also becomes hard, causing the brick to become more resistant to abrasion, slag action, permeability of gases, load at high temperatures, and sudden temperature changes. Coatings composed of 60 to 70% of fire clay and 30 to 40% of aluminum powder were found to overcome most of these deficiencies in insulating firebrick.     

Durability of Deaired Brick

The applicability to deaired brick of the durability gradings in the current American Society for Testing Materials Specifications C 62 and C 216 was questioned because of the lack of data on the properties and weathering resistance of de-aired brick. The production of 14 plants producing deaired brick was accordingly sampled, and determinations were made on representative subsamples of such properties as transverse and compressive strength, water absorptions by 24-hr, cold immersion and by 5-hr, boiling, and the derived saturation coefficients. Representative subsamples were also subjected to the action of weather in the exposure test plot maintained at the National Bureau of Standards and relations between measured properties and the effect of weathering for five years were considered. The effect of lamination and other types of nonhomo-geneity on weathering was also noted. It was concluded that the current specifications apply to both deaired and nondeaired brick.     

Some observations on calcium silicate brick specimens in the autoclave

An autoclave with an externally generated steam supply and fitted with windows has been used to observe calcium silicate brick specimens with varying initial moisture contents during the autoclaving cycle. In particular, gains and losses in weight due to condensation and evaporation of water were recorded. Tests on the autoclaved specimens indicated that bulk density, compressive and transverse strength varied with initial water contents of the mix within the range 4 to 14%. Specimens with high water contents expanded and cracked during autoclaving. C₂SH(A) rather than C? S? H(II) was formed in mixes with low water contents at short autoclaving times.     

THE EFFECT OF DRYING TEMPERATURE ON THE QUALITY OF PAPER

ABSTRACT

The effect of drying temperature on the optical properties of various papers was investigated. For paper from mechanical pulp, it was found that as drying temperature increased, light scattering coefficient decreased leading to lower brightness. The decrease in light scattering was associated with improved strength properties even at constant sheet density, and was attributed to increased bonding. These effects were not observed for chemical pulp furnishes.     

FACTORS INFLUENCING THE STAINING OF SILICA BRICK*

The staining of silica brick was found to occur in a critical temperature range of 900°‘ to 1000°C. Concurrently the brick had to be “soaked“ in this temperature range and exposed to an oxidizing atmosphere. Stained brick could be “cleaned up” or staining prevented by manipulation of the foregoing set of conditions as well as by additions of 4.5% or more of lime. The experimental data examined in the light of the system CaO-Fe₂O₃-SiO₂ suggest that the colorant is the mineral dicalcium ferrite.     

煤热解特性研究

对大雁、协庄和昔阳3个不同煤化程度的煤样，在N2，CO2和水蒸气3种不同气氛及不同温度下进行了热解研究，考察了煤化程度、热解气氛和热解温度对煤热解产物产率和热解气性质的影响规律．研究表明，对上述3个煤样，随煤化程度加深，焦产率增加，油和气产率一般随煤中挥发分增加而增加，但又与煤的大分子结构、热解温度和加热速率等有密切关系；干馏气组成H2和CH4含量协庄煤样最高，而(CO CO2)含量因煤中氧含量的降低而下降．与N2气氛相比，CO2和水蒸气气氛中半焦产率下降，气产率增加；油产率水蒸气气氛下最高．H2组分含量在水蒸气气氛下最高，而CO，CH4和烃类C2～C5组分则最低．LHV在N2，CO2和水蒸气气氛下逐次降低．