Papers by Keyword: Thermal Shock Resistance

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Authors: Alida Brentari, Martino Labanti, Francesca Mazzanti, Claudio Mingazzini, Sergio Sangiorgi, Matteo Villa, Stefano Martelli, Daniela Olevano
Abstract: Alumina-mullite refractory tiles are used as liners in gas turbines for power production, for the thermal insulation of the combustion chambers. The typical microstructure is characterized by a coarse fraction, in order to increase porosity (and hence thermal insulation) and improve thermal shock resistance (by grain bridging mechanism). A mixture of alumina and ceramic wastes was optimized to manufacture prototypal components, by cold isostatic press (CIP). On sintering at 1600°C, a final composition of 40% mullite and 60% alumina was obtained. For the production of refractory tiles with dimensions similar to the commercial ones, an appropriate mould was CAD-CAM designed and produced, using aluminium and silicone. 115 x 95 x 30 mm3 tiles were obtained and utilized for thermal shock tests. Samples were heated up to 1000°C and quenched to 20°C: this cycle was repeated 30 times before inspecting the macroscopic cracks. The results were compared with those obtained with a standard test for advanced technical ceramics based on MOR measurements. Two different pressing conditions were tested (60 and 150 MPa) in order to get data about a possible industrial production by uniaxial pressing.
Authors: Xue Hua Ren, Ping Zhao, Qi Hui Lai, Xuan Qin
Abstract: We chose a purging plug with good performance to analyze its insert plate. By X ray fluorescence analysis method, the main chemical composition is alumina and the small amount is silica. XRD analysis shows its phase compositions, main crystal phase is corundum, the secondary phase is mullite. SEM analysis is for the microstructure, grains are packed closely. They are sintered tabular corundums with smooth shape, which means there is liquid phase in sintering process to help mass transfer. As a conclusion, this product is designed from the point of material selection and structure control to improve its thermal shock resistance. Compacted microstructure combining with good thermal shock-resistance mineral phases improve the service life of purging plug.
Authors: Frank L. Riley
Authors: Chong Hai Xu, Chuan Zhen Huang, Xing Ai
Abstract: Thermal shock resistance is one of the primary properties for the ceramic cutting tool materials with perspectives in high speed machining. An optimum model for the compositional design of the composite ceramic tool materials is built based on the thermal shock resistance. The thermal stress fracture resistance factor R is used to characterize the thermal shock resistance of the ceramic material. Results show that the developed (W,Ti)C/SiC/Al2O3 multiphase ceramic tool material can be expected to achieve the highest thermal shock resistance when the volume fraction of (W,Ti)C and SiC is about 15.8% and 24.8%, respectively. Thermal fracture resistance of the (W,Ti)C/SiC/Al2O3 ceramic tool material is approximately 81-88% higher than that of the pure alumina ceramic when machining the hardened carbon steel, which coincides well with the theoretical prediction from the optimum model. It suggests that the method used here is feasible for the development of ceramic tool materials with designed thermal shock resistance.
Authors: S. Begum, Halina Misran, A. Aminuddin
Abstract: Cordierite ceramic of chemical composition 2MgO-2Al2O3-5SiO2 has low value of thermal expansion, excellent thermal shock resistance, high porosity and high strength. The exhibited properties resulted wide range of industrial applications, especially in the catalytic converter, kiln furniture, diesel particulate filter and high frequency insulator. It occurs rarely in nature and its formulation from the indigenous raw materials is sensitive to the peak sintering temperature and holding time. Both the parameters are again affected on the source of raw materials. Hence optimization of peak temperature and holding time is crucial for each source of raw materials. In this paper three indigenous raw materials, clay, kaolin and talc were taken and mixed with different dopants. The prepared powder batch was sintered at different peak temperature and holding time. Among the three indigenous raw materials kaolin was found to be most suitable to formulate cordierite. The peak temperature was varied within the range of 1340°C -1400°C and the holding time was considered from 30 minutes to 90 minutes. Both the parameters had significant influence on the production of cordierite. The percent of cordierite formation was affected with both the variation of holding time and peak temperature. Tough thermal shock resistance was not influenced by any of the parameters, but the influence on the porosity was quite significant. The green body was also prepared from calcined powder batch and was sintered at different peak temperature. Calcination did not exhibit any affect on cordierite formulation.
Authors: Wei Li, Hou Xing Zhang, Ze Ming Tong, Yan Ming Li
Abstract: Slide gates are installed at the bottom of a ladle or tundish to control the flow of molten steel. It plays an important role in ladle refining process and continuous casting. Al2O3-ZrO2-C refractories are widely used as slide gate materials due to its excellent corrosion and thermal shock resistance. At the start of casting, molten steel almost 1600°C passes through the bore of slide gate, the plate is rapidly heated up, the temperature difference between the bore and edge part, the slide gates are subject to large thermal gradients, so there is large thermal stress in the plate. This paper will show the results of our improved slide gates with good thermal shock resistance.
Authors: Zheng Wei, Guo Qi Liu, Jin Song Yang
Abstract: Spinel-C material is important for monolithic stopper and submerged nozzle, which usually determine the application effects. Spinel-C specimens with 8% flake graphite is characterized by good corrosion resistance but poor thermal shock resistance. The effects of additives (Al-Si alloy, silicon powder, B4C and SiC), flake graphite (+199/-199), ultrafine flake graphite, expanded graphite and nickel nitrate + pitch powder on thermal shock resistance of spinel-C material were investigated by using water-quenching method. The results show that: (1) The addition of Al-Si alloy and B4C can significantly decrease the residual strength ratios (RSR) of the specimens. The addition of SiC and silicon powder can improve the RSR obviously. (2) The flake graphite of different particle sizes has little effect on the RSR of the specimens. With the increasing of the expanded graphite content, the RSR of the specimens increases. (3) The addition of mesophase pitch and Carboresâ P can receive the RSR rise of 74% and 59% respectively.
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