Effect of Heat-Insulating Layer Thickness on Melting Rate of Ice Fixed Abrasives Polishing Pad

The formula of the thickness of the heat-insulating layer is deduced via heat transfer analysis,according to the principle of heat transfer in limited space.Polishing experiments are carried out using the same technological parameters.Compared with the polishing experimental results,the heat transfer model is proved to be correct.As validated by the experimental results,polyurethane heat-insulating layer can effectively improve the service life of the ice fixed abrasive pad and alleviate the melting rate in the polishing process to improve the polishing quality proposed.The heat transfer model provides theoretical basis for research of temperature field of ice fixed abrasive polishing.

A Study on Impervious and Heat-Insulating Performance of Geomembrane Composites Within Breakwater

This paper investigates the performance of geomembrane composites used as impervious and heat-insulating lining within a breakwater for a power station. The seepage field, distribution of stress-strain contour and seepage discharge of hot water which has been treated as the inner thermal source in the calculation of heat-insulation, have been given by three-dimensional calculation method coupling seepage with stress. The results indicate that the impervious and heat-insulation effect of geomembrane composites is significant.

Effects of ZrO_2 Nanoparticles on the Microstructure and Thermal-protective Properties of PEO Coating on Al-12.5%Si Alloy

PEO ceramic coatings including ZrO_2-Al_2O_3-SiO_2 in three phases were prepared on an Al-12.5%Si alloy in electrolyte solutions containing ZrO_2 nanoparticles. The microstructures and phases of the coatings were analyzed by SEM and XRD, and the heat insulation performance and the thermal shock resistance of the coatings were investigated. The compactness of the coating increased significantly and the hindrance of the Si element on plasma electrolytic oxidation process was effectively weakened. The growth rate of the coating was improved substantially with the addition of ZrO_2 nanoparticles. The PEO ceramic coatings are primarily composed of SiO_2 and high temperature steady phases such as a-Al_2O_3 and c-ZrO_2. Both the content of c-ZrO_2 and the heat-insulating property of the coating increased significantly. The ceramic coatings with special microstructure and composition formed in the solutions containing ZrO_2 nanoparticles possess excellent heat insulation performance and thermal shock resistance.

Prediction of the Melting Paths of Wollastonite-Containing Compositions

The article analyzed the main groups of thermal insulation(TIM)and slag-forming(SFM)mixtures produced by leading foreign companies:acidic ones based on the SiO2–Al2O3 system,basic ones based on the CaO–MgO–Al2O3 system and medium basic ones based on the CaO(MgO)system–Al2O3–SiO2.It is shown that achieving the necessary properties of the SFM and TIM requires strict observance of the mass content of the components of mixtures produced on the basis of synthetic materials in granular form with a given dispersion.Compliance with a given composition and dispersion is associated with the need to provide a given melting temperature(for intermediate ladles 1250–1450℃,for molds 950–1150℃),neutrality to the cast metal,protection of the melt from secondary oxidation,minimization of heat loss from the melt mirror,absorption of non-metallic inclusions of various natures(Al2O3,CaO,SiO2,TiO2,less often MgO-containing)and sizes;as well as a number of specific requirements:compatibility with the working layer of the lining of the bucket,maintaining the work of the stoppers,minimizing harmful gaseous emissions,etc.It is known that Al2O3,TixOy,and CaO refractory inclusions in steel cause the majority of defects on the surface of a cold-rolled sheet,therefore,the aim of the work was to analyze the physicochemical regularities and melting paths of the wollastonite-containing compositions during the assimilation of nonmetallic inclusions by them.To analyze the melting paths of the wollastonite-containing compositions in the CaO–Al2O3–SiO2 system,a diagram of the primary crystallization field of anorthite and the adjacent boundary curves is shown,indicating the directions of temperature drop and designating invariant points.The presented scheme adequately reflects the topological regularities of the state diagram of the CaO–Al2O3–SiO2 system.To analyze the melting paths of the wollastonite-containing SFM compositions during the assimilation of TiOx impurities from steel melts,a diagram of the primary crystallization field of CaTiSiO5 sphene with adjacent boundary curves,the direction of temperature drop,and the designation of invariant points is presented.It is shown that steric and kinetic factors have a predominant effect on the formation of the three-layer layer in the SFM(molten,partially molten and unmelted layers).The more uniform the thickness of the entire SFM layer(when it is heated from the melt mirror),the smaller the influence,and the competing processes of solid-phase interaction will start,which provide a gradual accumulation of more refractory compounds and increase the melting temperature of the SFM.