scholarly journals Research of kind and quantity of chromic oxide addition influence on alumina-chromia-zirconium silicate refractories properties

Author(s):  
V. V. Martynenko ◽  
V. V. Primachenko ◽  
I. G. Shulyk ◽  
Yu. Ye. Mishnyova ◽  
K. I. Kushchenko ◽  
...  

Research of pigment chromic oxide addition influence on properties of alumina-chromia-zirconium silicate refractories simples with a mass part 30 and 15 % Cr2O3 got by the semidry pressing method is carried out. It is set, that in samples made from batch with 30 % Cr2O3 optimal quantity of pigment chromic oxide, which provide achieving close properties indexes compared to indexes of samples without this component should be considered 10 %, and in samples made from batch with 15 % Cr2O3 — 6 %. The properties indexes of samples with 30 % Cr2O3 containing 10 % pigment chromic oxide are: mass part of Al2O3 — 62.7 %, Cr2O3 — 30.3 %, ZrO2 — 5.8 %, open porosity 22.6 %, apparent density 3.27 g/cm3, cold crushing strength 123 N/mm2, thermal shock resistance on the mode 950 оC — water 4 thermal cycles, residual changes of sizes at a temperature 1650 оC, exposition 2 hours 0 %. The properties indexes of samples with 15 % Cr2O3 containing 6 % pigment chromic oxide are: mass part of Al2O3 — 76.4 %, Cr2O3 — 15.2 %, ZrO2 — 6.1 %, open porosity 22.4 %, apparent density 3.17 g/cm3, cold crushing strength 145 N/mm2, thermal shock resistance on the mode 950 оC — water 4 thermal cycles, residual changes of sizes at a temperature 1650 оC, exposition 2 hours 0 %. Obtained results are used at making of products for glass melting furnace of industrial lining for fiberglass production from E glass.

Author(s):  
V. V. Primachenko ◽  
I. G. Shulik ◽  
I. V. Khonchik ◽  
T. G. Tishina

Effect investigation of an addition amount of spherical alumina on the properties of ramming mullite-corundum mixes of the MMK-90 (on a binder of an aqueous solution of orthophosphoric acid) and MMKPBF (with a MgO addition on a borophosphate binder) brands, as well as samples from them, have been carried out. As a result of the carried out studies, it was found that the use of an optimal amount (4 %) of spherical alumina in the composition of ramming mullite-corundum mixes provides an increase in by 30 % in the cold crushing strength of samples made from them, fired at a temperature of 1580 °C, while maintaining at sufficiently high level indicators of their thermal shock resistance and slag resistance. The indicated alumina use in the composition of the MMK-90 mix during high-temperature firing of samples leads to an intensification of the mullite synthesis process. In fired samples from the MMKPBF mix, the spherical alumina forms a dense intergrowth of "felt-like" structure, which reinforces the structure, increasing the strength and thermal shock resistance of the samples. Indicators of physical and chemical properties of ramming mullite-corundum mixes of improved composition and samples made from them (for MMK-90 and MMKPBF mixes, respectively): chemical composition, wt. %: Al2O3 — not less than 90.0 and 85.0; SiO2 — within 3.2-5.0 and no more than 2.5; Fe2O3 — no more than 1.0 and 0.6; P2O5 — in the range of 2.5-3.5 and 0.5-1.0; grain size composition, mm — 3-0; cold crushing strength after firing at a temperature of 1580 °С — 110 and 70 N/mm2; thermal shock resistance — > 20 thermal cycles 950 °С — water. Ramming mullite-corundum mixes of improved composition are recommended for use in various heating units with high specific mechanical loads on the lining.


2011 ◽  
Vol 250-253 ◽  
pp. 588-594 ◽  
Author(s):  
Dong Wang ◽  
Yong Li ◽  
Yang Li ◽  
Rui Li ◽  
Yue Li

Using high pure magnesia and magnesia-spinel as the main raw material, keeping the same quantity of spinel, specimens were made with different spinel size distribution (≤0.044mm, 1-0mm, 2-1mm, 3-2mm and 3-1mm). Dextrin and brine are the binder. Specimens were dried at the temperature of 110°C for 24 hours, sintered at the temperature of 1680°C holding 8 hours in a tunnel kiln. The properties and microstructure of the specimens were analyzed. The results are shown that the addition of spinel with grain size of 3-1mm improves sintering of magnesia-spinel brick, with the thermal shock resistance reaching 18 cycles, the cold crushing strength reaching 54 MPa, improving the comprehensive performance of the magnesia-spinel brick.


2017 ◽  
Vol 36 (3) ◽  
pp. 844-848
Author(s):  
FA Ovat ◽  
DE Ewa ◽  
EA Egbe

The characterization of some clay as refractory materials for furnace lining has become relevant to find solutions to the cost involved in the purchase and importation of these refractory materials. This work investigated the refractory properties of clay samples for their suitability for use in the industries. Clay samples were collected from Gakem and Abouchiche areas and analysed for physical and chemical properties to determine the suitability of the clays as refractory materials. The results showed cold crushing strength (21.46MN/m2), thermal shock resistance (27 cycles), bulk density (3.52g/cm3), linear shrinkage(3.80%), apparent porosity (28.84%) and permeability (80%) for Gakem; and cold cold crushing strength (18.40MN/m2), thermal shock resistance (25 cycles), bulk density(2.81g/cm3), linear shrinkage (3.70%), apparent porosity (25.86%) and permeability (77%) for Abouchiche respectively. The chemical compositions of these clay samples were also investigated. The results showed that the samples fall under Aluminosilicate type of clay because of their high values of Aluminium Oxide and Silicon Oxide. Tests showed that clay from these areas can be used to produce refractory materials that can withstand a furnace temperature of about 1600°C. http://dx.doi.org/10.4314/njt.v36i3.26


2013 ◽  
Vol 315 ◽  
pp. 11-14 ◽  
Author(s):  
I.A. Rafukka ◽  
B. Onyekpe ◽  
Y. Tijjani

The investigations centered on how addition of Gezawa clay (GC) affects the refractory properties of the Gezawa stone (GS) (Silica Stone) with a view to finding the optimum percentage of the blend that will give good refractory properties. The samples were crushed, ground, sieved and the chemical compositions were determined. Test samples were produced by blending the Gezawa stone with various proportions of Gezawa clay. The refractoriness of the samples was measured, and the samples were then fired to 1100and standard properties such as thermal shock resistance, cold crushing strength and apparent porosity were determined. The result shows that addition of Gezawa clay to Gezawa stone improves its thermal shock resistance but reduces the refractoriness, while the porosity was found to be within the specified range for fire clay and the cold crushing strength of the samples was high. Compromise could be made in selecting the percentage that would suit certain application.


2011 ◽  
Vol 295-297 ◽  
pp. 2309-2313
Author(s):  
Xin Liu ◽  
Dian Li Qu ◽  
Zhi Jian Li

This paper deeply studied the limitation of evaluating the thermal shock resistance of Al2O3-SiO2 refractory by measuring Strength Loss Rate (SLR). By means of supersonic, X-ray diffraction (XRD), the results were drawn as followed.1)After the thermal shock experiment for mullite based A-S refractory, which were composed by mullite and corundum, the supersonic velocity slowed down as it going through the sample while the cold crushing strength abnormally increased at initial state.2) The strength increased remarkably with the ascending of mullite fraction.3)It is inadequate to evaluate the thermal shock resistance of mullite based A-S refractory by strength loss rate.


Author(s):  
P. O. Kushchenko ◽  
V. V. Primachenko ◽  
I. G. Shulyk ◽  
Yu. Ye. Mishnyova ◽  
K. I. Kushchenko ◽  
...  

Researches of a branch composition and firing atmosphere influence on structure and properties of pressed alumina-chromia-zirconium silicate refractories with 60 % Cr2O3 content were carried out. The optimal branch composition which after firing in oxidizing atmosphere provides obtaining of samples with open porosity 24.8 %, apparent density 3.46 g/cm3, cold crushing strength 78 N/mm2 and thermal shock resistance by 950 ºС — water — 7 thermal cycles was established. The phase composition of samples was determined. It has been shown that, firing in a reducing atmosphere, as well as titanium oxide addition, have no significant effect on samples properties. Corrosion resistance comparative researches of alumina-chromia-zirconium silicate refractories with 60 % Cr2O3 content and refractory brand KHTSS-30 with 30 % Cr2O3 content to glass «E» and basalt melts by crucible method at a temperature of 1580 °C with an exposure time of 8 hours were carried out. It has been established that, glass «E» and basalt impregnate refractories, moreover for samples with the developed optimal composition the impregnation depth was the smallest in comparison with samples of other compositions. The corrosion mechanism has been established, which consists in the penetration of glass «E» and basalt melts into refractory with further dissolution of corundum grains in them. Sintered Cr2O3 and solid solutions based on it in the composition of samples prevent corrosion, reducing the interaction area of melts with corundum grains, and when exposed to basalt melt, also forming spinelid with its components, which slows down further penetration of melt into refractory structure, thereby reducing its corrosive effect on the refractory. Based on the obtained results, a technology of a new domestic type of product (alumina-chromia-zirconium silicate refractories with 60 % Cr2O3 content manufactured by semi-dry pressing method) was developed.


2020 ◽  
Vol 94 (2) ◽  
pp. 414-453
Author(s):  
Małgorzata Daszkiewicz ◽  
Piotr Łuczkiewicz ◽  
Jörg Kleemann ◽  
Aneta Kuzioła

AbstractThe necropolis at Malbork-Wielbark was excavated from 1927 to 1936 and 2008 to 2019. This burial ground is the eponymous site of the Wielbark culture. To date, over 2000 burials, both inhumation and cremation (pit and urn graves), have been recorded at this site, attesting to its continuous use from the Early Pre-Roman Iron Age (phase A1) to the early Migration Period (phase D1), with particular emphasis on the Roman Period. The cemetery site partially overlies and damages an earlier Iron Age settlement of the Pomeranian culture.Laboratory analyses were carried out on 113 pottery sherds. The series of samples chosen for analysis reflected, as far as was possible, all relative chronological phases and vessel shapes. The pottery was analysed using a step by step strategy built on the results of MGR-analysis (i. e. the classification of samples based on their matrix type) and on a macroscopic assessment of clastic material. In addition, an estimation of chemical composition by portable energy-dispersive X-ray fluorescence (pXRF) was available for each sample. After they had been classified, samples were selected for chemical analysis by wavelength-dispersive X-ray fluorescence (WD-XRF), estimation of physical ceramic properties (open porosity, water absorption and apparent density), Kilb-Hennike analysis (K-H analysis), thin-section studies using a polarising microscope, a study of surface phenomena by RTI (Reflectance Transformation Imaging), thermal analysis (TG-DTG-DTA), X-ray diffraction analysis and functional properties analysis (water permeability and thermal shock resistance), as well as experimental estimation of magnetic properties.The results of MGR-analysis carried out on ceramic samples taken from 113 potsherds revealed that all of the pottery was made from various non-calcareous clays with fine-grained iron compounds homogeneously distributed in the matrix. It was decided not to carry on determining/using MGR-groups, as nearly every sherd represents a different MGR-group. This means that these vessels were made during different production cycles. The differences in thermal behaviour between samples were attributed only to matrix-type groups. It can be concluded that 85 % of the total sherds were made from plastic raw materials of the same provenance, and that the same matrix-type groups occurred in all chronological phases. The percentage of vessels made of particular raw materials indicates a significant difference in the preferences of Pomeranian Culture potters and those of Pre-Roman Iron Age, Early Roman Period and those of the Late Roman Period, when one type of raw material disappears from use. This last period is also characterized by an increase in the number of vessels fired in a reducing atmosphere. Standardization is also evident in vessel-wall thickness, which falls within a narrow range of values, on the other hand combined with a large variety in grain sizes up to very large ones and with a wide range of open porosity values, which in turn points to a lack of care in the preparation of the ceramic body. Vessels that may have been non-local origin are noted in all chronological phases. Analysis of functional properties (water permeability and thermal shock resistance) revealed that the pottery deposited in graves included fully functional wares, such as cooking pots, as well as vessels intended solely as grave goods.More than a few samples evidence the use of a slow-rotating potter’s wheel, and it is also possible that a template was used for forming vessel rims. However, there are very few examples of truly technologically advanced vessels. The technology is generally tailored to the desired type or form of vessel.


2017 ◽  
Vol 23 (5) ◽  
pp. 672-678 ◽  
Author(s):  
Valentin ANTONOVIČ ◽  
Jerzy WITEK ◽  
Romualdas MAČIULAITIS ◽  
Renata BORIS ◽  
Rimvydas STONYS

This work investigates medium cement refractory castable with additives of carbon and polypropylene fibers. The peculiarities of microstructure changes in the fiber and castable matrix contact zone, channel formation, and changes of cold crushing strength of fiber additives, which have a refractory castable matrix under temperature treatment, were investigated. The investigation results allowed to predict that using a mix of fibers more effective than using them indi­vidually. The influence of fiber additives on the mechanical characteristics and thermal shock resistance of the refractory castable with fiber additives was tested. It was found that the addition of carbon fiber has a positive impact on the ther­mal shock resistance of the investigated castable, which is confirmed by the results obtained by thermal cycling, as well as by the values calculated for thermal shock resistance R4 and Rst. In addition, the results of the investigation of thermal cycling show that the value of the thermal shock resistance was highest when a mixed fiber additive (CF+PP) was used.


100kg of zircon sand raw material was obtained from Pingell, Toro Local Area of Bauchi State while silica and kaolin were used as the additive materials in different proportions. The materials as received were wet and in large chunks, and was sun dried prior to crushing with Jaw crusher and sieved with the sieve of size 100 µ to obtain fine powder particles. Samples of various compositions were prepared from the powder particles of Zircon sand (X); Zircon sand and silica (Y); zircon sand, silica and kaolin (Z) and mixed together based on the experiment’s program with a predetermined amount of water in the mixer. Refractory brick test specimens were prepared by standard methods from samples A, B and C and subjected to refractory test such as apparent porosity, bulk density, cold crushing strength, linear shrinkage, thermal shock and refractoriness in order to evaluate the effects of adding silica and gypsum to Pingell zircon sand and investigate its suitability as raw material for refractory brick production and furnace linings. From the result obtained, the average porosity of X, Y and Z is 13.5, 18.3 and 21.6 % respectively while the respective bulk density are 3.2, 2.0 and 1.8 g/cm3. The values of the cold crushing strength for samples X, Y and Z are respectively 25.5, 23.4 and 18.8 MN/m2 but the firing shrinkage is 4.5, 5, and 6.5 %. Thermal shock resistance of 26, 20 and 22 cycles were obtained respectively for X, Y and Z. Refractoriness of 1600, 1580 and 1610 0C were obtained respectively for samples X, Y and Z. The porosity, firing shrinkage and refractoriness increased with increase in the addition of silica and kaolin to zircon sand whereas the bulk density, thermal shock resistance and cold crushing strength of zircon sand decreased with the addition of silica and kaolin but the addition of silica reduced the refractoriness of the zircon sand. The addition of silica and kaolin in the appropriate proportions improved the refractory properties of the zircon sand and hence will find applications in the production of refractory bricks and furnace lining.


2011 ◽  
Vol 291-294 ◽  
pp. 1795-1799 ◽  
Author(s):  
Li Jun Zheng ◽  
Guo Dong Zhang ◽  
Dian Li Qu ◽  
Feng Liu

The Al2O3-Cr2O3 slag as raw material was analyzed by scanning electron microscopy (SEM). The effects of different size distribution of MgO-Al2O3 spinel grain on physical properties of refractory bricks made from Al2O3-Cr2O3 slag was studied according to YB/T376.1-1995(water quenching), GB/T 5072-1985, GB/T 2997-1982 criterion. The results show that the main crystal phase of the refractory bricks were chromium corundum, corundum. The refractory bricks containing 10 wt% of the maximum size of 3.0 mm of MgO-Al2O3 spinel grain can significantly improve the thermal shock resistance of this refractory bricks. At the meanwhile, This kind of refractory bricks can be absolutely satisfied with the requirements about cold crushing strength, bulk density and apparent porosity.


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