Chamotte Brick Research Articles

SHS-Aided Joining of Ceramic Materials with the Ta Substrate

Experiments on evaluating the possibility of joining ceramic materials with a Ta substrate under conditions of self-propagating high-temperature synthesis (SHS) are explored. The sample consists of tantalum foils and pellets Ti + 0.65C and 5T + 3Si, between which a Ti + 2B igniting tape is laid. The sample is installed on a boron nitride support. A chamotte brick plate (SiO2 + Al2O3) with a load of 3360 g placed on its top is placed on a sample to decrease the heat sink. The experiments are performed in a reaction chamber in argon under a pressure of 1 atm. The samples are preheated from the bottom, and the reaction is initiated from their butt. The sample temperature is measured using W–Re thermocouples. The temperature gradient over the sample thickness, depending on the heating rate, is 50–150 K/mm. The samples with strong joining of the tantalum foil with Ti + 0.65C, as well as between two pellets, are formed. The top foil is not welded to the 5Ti + 3Si pellet, which is explained by a rather low temperature (1600°C) at the interface. When studying the interface of the tantalum foil with titanium carbide, the formation of Ti–Ta and (Ta,Ti)C interlayers is found. The possibility of joining the tantalum foil with ceramic materials during SHS is shown by investigations. The main conditions of such joining are the presence of the liquid phase and correspondence of the combustion temperature of the Ti + 0.65C composition to the melting point of the tantalum substrate. These results can be useful when fabricating multilayered functional coatings and functionally graded materials.

SHS-aided joining of ceramics with Ta substrate

The possibility of joining ceramic materials with a Ta substrate was explored in the conditions of self-propagating high-temperature synthesis (SHS). The sample used in experiments consisted of Ta foils, Ti + 0,65C pellet, 5Ti + 3Si pellet, and a Ti + 2B igniting tape laid between them. The sample was installed onto a BN base and covered by a chamotte brick (SiO2+ Al2O3) plate with a weight of 3,36 kg placed on top in order to reduce heat sink. Experiments were performed in a closed reactor under 1 atm of Ar. Samples were preheated from the bottom, after which SHS reaction was initiated from the butt. Temperature was monitored with three W/Re thermocouples. Depending on heating rate, temperature gradient along the sample depth had a value of 50–150 deg/mm. The samples obtained exhibited strong joining between Ta foil and Ti + 0,65C and also between the two pellets. The upper foil did not stick to the 5Ti + 3Si pellet, which can be explained by low temperature at the interface (1600 °C). At the Ta–TiC interface, the formation of Ti–Ta and (Ti, Ta)C interlayers was observed. The studies conducted demonstrate the possibility of Ta foil joining with ceramic materials under SHS conditions. Main conditions for this joint are the presence of a liquid phase and Ti + 0,65C combustion temperature matching the Ta substrate melting temperature. The results may be useful for deposition of multilayer functional coatings and functionally graded materials.

Study of Alkali Resistance of Refractory Materials Used in Boilers Operating on Wood Fuel

Using the ASTM C 454–83 method alkali resistance is studied for various refractories (chamotte brick, traditional and medium-cement chamotte concrete) used most often in power generation boilers operating on wood fuel. Resistance to alkali of medium-cement concrete developed by the authors with a filler prepared from sinter grade Gorkal-50 (produced by the Gorka Plant, Poland) is also studied. It is established that use of milled quartz sand additive improves resistance of the test cement significantly towards the action of alkaline salt (K2CO3 is used in the work) at 1100°C. It is shown that the test additive during action of alkali facilitates formation of a protective layer that prevents penetration of K2CO3 decomposition products into the material structure.

Investigation of the efficiency of a high temperature heat storage charging

The article presents the results of the test of a heat storage filled with chamotte brick. The air parameters were used as the basis for determining the heat stream represented by a working medium, which was then compared with the stream accumulated in the material filling the deposit. Additionally, heat streams were shown for individual segments of the deposit. The efficiency of heat accumulation was determined for each of them. They showed that the efficiency of accumulation process was highest in the deposit’s first segments and the lowest in the last segments, where the air was the coldest. The dynamics of the efficiency’s shift was different for each of the observed segments. In the area closest to the inlet of hot air, the dynamics of the process of heat accumulation decreased the fastest and after one hour only a slight increase of efficiency was visible in the function of time. In the accumulation material placed closest to the outlet, the process of absorbing heat was very fast, starting from the 20th minute before the tests were completed. The smallest changes in the process’ character, throughout the whole time of testing, were recorded in the middle layer.

INVESTIGATION OF LINING PARAMETERS IMPACT ONTO METAL AIR-COOLING PROCESS IN CHAMBER FURNACE

The appropriate mathematical model was created for the investigation of lining parameters impact onto metal air-cooling process in chamber furnace. Numerical computing for various lining composition was conducted: fully dense refractory material, made from chamotte brick; refractory ceramic fi bers on the wall and arch with fully dense refractory of hearth; conceptual lining of entire chamber furnace with refractory ceramic fi bers. Processing of the results allowed to illustrate the impact of the lining type on the length of aircooling process, thereby showing possible reserves for accelerating of this process step.

Numerical simulation and combination optimization of aluminum holding furnace linings based on simulated annealing

To reduce heat loss and save cost, a combination decision model of reverb aluminum holding furnace linings in aluminum casting industry was established based on economic thickness method, and was resolved using simulated annealing. Meanwhile, a three-dimensional mathematical model of aluminum holding furnace linings was developed and integrated with user-defined heat load distribution regime model. The optimal combination was as follows: side wall with 80mm alumino-silicate fiber felts, 232mm diatomite brick and 116mm chamotte brick; top wall with 50mm clay castables, 110mm alumino-silicate fiber felts and 200mm refractory concrete; and bottom wall with 232mm high-alumina brick, 60mm clay castables and 68mm diatomite brick. Lining temperature from high to low was successively bottom wall, side wall, and top wall. Lining temperature gradient in increasing order of magnitude was refractory layer and insulation layer. It was indicated that the results of combination optimization of aluminum holding furnace linings were valid and feasible, and its thermo-physical mechanism and cost characteristics were reasonably revealed.

Synthesis of the mullite refractory ceramic coating under local heating

The possibility of performing the thermochemical synthesis in the M1 oxide ceramic coating under surface heating in order to produce mullite structures is considered with the aim of extending the field of application of protective oxide ceramic coatings and decreasing the power consumption. The coating is applied to a ShA chamotte brick. Then, the synthesis of mullite and mullite-like structures is provided with the use of surface heating by thermochemical compositions and the thermal insulation prepared from the refractory cellular concrete for the control of the heat removal.

Petrographic investigation of the pore structure of alumina-silica refractory concretes

The results of a petrographic study of the pore structure of chamotte filler, the binder of alumina-silica refractory concretes, and stamped chamotte brick are presented. It is established that the pore structure of vibrationally cast alumina-silica concretes produced at the Semiluki Refractory Works consists mainly of round, closed pores.

Solubility of TiO 2, Fe 2O 3 and MgO in mullite

The temperature dependent solubility of titanium, iron and magnesium in mullites coexisting with SiO 2-rich partial melts in a used chamotte brick was studied with a high-resolving microprobe. The mullites of the starting material have relatively high mean Fe 2O 3 (≈2.4 wt%), but lower TiO 2 (≈1.4 wt%), and very low MgO contents (≈0.5 wt%). Cation removal from mullite to coexisting glass phase is observed at high temperature: the onset of exsolution is about 1300°C for magnesium, 1350°C for iron, and 1400°C for titanium. Sample specimens annealed at 1650°C have mullites with about 0·5wt% Fe 2O 3, 0·9 wt% TiO 2, and traces of MgO. Cation exsolution curves follow exponential laws, the exsolution rate being considerably higher for Fe 2O 3 than for TiO 2 and MgO. The study documents a much higher mobility of the iron ion as compared to that of titanium.

Selection of the optimum composition of production binder in unfired graphite-chamotte parts with an increased carbon content

The density and strength of graphite-chamotte parts depend upon the character of the structure of the compact, which is dependent upon the amount of applied pressing pressure and also the content and form of the production binder. With the use of the generalized function of desirability the optimum composition of production binder was found. In testing in the connecting channel of a unit for superheating cupola iron with natural gas the experimental parts produced showed a life double that of high-alumina blocks and many times greater than that of chamotte brick.

Phase transformations of the chamotte lining of a tubular furnace in reduction firing of iron-ore pellets

In reduction firing of iron-ore pellets with a solid fuel in tubular furnaces lined with chamotte brick intense mechanical and chemical failure of the refractory lining and the formation of a crust on its surface are observed.

Refractory concrete parts for edging the walls of soaking pits

The technicoeconomic desirability of replacing chamotte brick in the edge of soaking pits with concrete parts of bauxite or of a mixture of commercial grade chamotte and silicon carbide part scrap using high-alumina cement was shown. The life of the upper structure of the soaking pit doubled, the time for repair of this element of the lining was reduced by more than 10 times, and the heavy bricklaying work was replaced by less laborious assembly work.

A refractory solution for attaching the thermal insulation of glass-melting furnaces

the optimal composition of the refractory solution based on the ShT-2 aluminosilicate mortar (State Standard 6137-61) with various phosphate binders: orthophosphoric acid (H3P04); aluminophosphate (APB); and chrome aluminophosphate (ACPB) binders. The use of the ShT-2 mortar as the subject of the study is because it is widely used in practice in furnace lining. The choice of the phosphate binders was determined on the basis of well-known studies indicating that they are most effective in a composite material with acid, in particular with aluminosilicate, fillers [i, 2]. Table 1 shows the characteristics of the phosphate binders. The choice of optimal composition of the refractory solution was based on a determination of the strength of adhesion of the compound as a function of the concentration of binders. For this purpose we prepared aqueous solutions of each of the phosphate binders with a density of i.i; 1.2; 1.3; 1.4; 1.45; 1.5; and 1.6 g/cm 3. The concentration of binders in the solutions corresponded to the values given in Table 2. Table 3 gives the data on the concentration of P20s in the binders and solutions. The strength of the adhesive compounds, i.e., the binding capacity of the solutions, was determined for specimens measuring 20  40  60 mm sawn from a chamotte brick and stuck in pairs using the experimental solutions. After sticking the specimens together, we kept them at room temperature for not less than 20 h and then heated them to 300~ at a rate of 150~ after which they were again kept at the specified temperature for 2 h before being cooled along with the furnace. The heat treatment temperature of 300~ was chosen because the interaction between the phosphate binders and oxides which predominate in the ShT-2 mortar (Si02 and A1203) occurs in the 150-300~ interval [3]. The specimens prepared in this way were tested for shear under compression and from the value of the latter we evaluated the adhesive properties of the solutions.

Durability of the lining of mixer-type transfer ladles

A method has been developed and tested for increasing the durability of the lining of 420-ton mixer type transfer ladles for cast iron by the impregnation of the active layer with tar. At a tar temperature of 100°C the active layer is fully impregnated in 65 h. The result is a decrease in the porosity and increase in the coldcrushing strength of the chamotte brick. For a good-quality impregnation use must be made of a steam coil which will heat the tar evenly throughout the ladle volume to 100–120°C.

Efficient charge settings for mechanizing the unloading of chamotte brick from tunnel-kiln trucks

Efficient charge settings for mechanizing the unloading of chamotte brick from tunnel-kiln trucks

Ultra-light perlite-sillimanite-chamotte refractories

The change from the production of ultra-light refractories from waste paper, sawdust and dust from electric filters to the production of perlite—sillimanite ultra-light brick permitted the drying time of the green product in tunnel driers to be reduced by a factor of 1.7 in addition to which the brick can be fired in tunnel kilns at the temperature for ordinary chamotte brick (1380°C), spoilage is reduced, the production process can be carried out on existing floor space, product quality is better, and costs are lower.

Refractories for powerful blast furnaces abroad

Abroad, the linings of the shafts of powerful blast furnaces are made from dense chamotte brick of high purity with the minimum content of iron oxides and other contaminating impurities. Impregnation of the fired chamotte brick with phosphates substantially increases the alkali resistance, and consequently the resistance of the blast furnace lining. The bosh and well are lined with carbon refractories. Speedy mechanized laying of the wells is done with large blocks up to 6.4 m long, and with cross sectional measurements of up to 0.8-0.6 m. In particularly severe service conditions in the absence of a protective skin layer in the lower part of the shaft and shoulders successful use is being made of carbon linings using electrographitic and semigraphitic products.

The search for internal isotopic tracers in metallurgical materials

In a search for internal isotopic tracers in metallurgical materials a group of elements has been chosen which can be determined by the neutron activation method with the highest sensitivity. A method has been developed for the determination of W, As, Au, La, In, Sc, Re and Ir in metallurgical materials. The separation of the elements was carried out using extraction and precipitation. The determination of the elements was carried out in samples of chamotte brick and washed ores. The limits of the determination of the elements are of the order of 10 -11 g for Au, 10 -l~ g for In and La and 10 -9 g for As, W, Sc, Re and Ir. The large scatter of the results indicates the inhomogeneity of the materials analyzed.

Chamotte and semiacid ladle brick from Barzassk clays

The Barzassk (basic O1 and O2, and semiacid PK1) clays are suitable for making chamotte and semiacid ladle brick. The production of refractories from these clays can be organized using the technological production scheme for chamotte articles made by semidry pressing. In order to increase the strength of the green products made from semiacid clays it is necessary to reprocess the bodies with an addition of sulfite lye on runner mixers with rollers.

Service of chamotte and high-alumina brick in blast-furnace stack

Destruction of refractory brickwork in the top of the blast furnace stacks at the Magnitogorsk Metal Works is restricted on account of the relatively low temperatures of the medium and occurs mainly through the abrasive effect of the blast charge and the gas stream. The absence of hardened slag on the brickwork in the middle of the stack and the high temperature of the medium have an effect on the extensive wear and tear of the lining subjected to the abrasive gas stream. The wear becomes worse on account of the deposition of zinc, alkalies and carbon soot on the brickwork. Reasons for cracking and striation of refractory brick should be studied. In the bottom area of the stack the high-alumina brick showed the same strength as other types of lining materials. However, since the properties of this brick after service (density, strength, etc.) were practically the same, further tests should be carried out in the middle section of blast-furnace stacks.