Applied Mechanics and Materials Vols. 291-294

Abstract: The 45 steel was processed by laser remelting after the carbonitriding heat treatment in this study. The microstructure morphology and microhardness of the laser-remelting layer at different laser powers were investigated by scanning electron microscope (SEM) and microhardness tester, respectively. The results show that a compact microstructure and a homogeneous element distribution can be achieved at the laser power of 1.2 kW under the given other laser parameters, and the microhardness was enhanced greatly.

Abstract: The viscosity of CaO-MgO-Al₂O₃-SiO₂-TiO₂ system blast furnace slag had been measured in present study. And the effect of TiO2 and Comprehensive Alkalinity on the viscosity and activation energy was analyzed. The results showed that TiO₂ exhibits amphoteric behaviour. Higher comprehensive basicity is helpful to change complex silicate structures into simple structures.

Abstract: In order to promote the rational utilization of high-phosphorus iron ore in western Hubei of China, the effect of process parameters on desilication rate of the high-phosphorus hot metal was investigated. The results show that the desilication rate increases slightly with indistinctive effect with the increasing of desilication agent addition. The oxygen efficiency is over 50% when desilication agent addition is about 30kg/t. Desilication rate is higher when the stirring gas flow is about 0.4l/min. Strengthening stirring of bath at the beginning period can improve kinetics condition of desilication reaction.

Abstract: Decomposition of the low-grade mixed Scheelite and Wolframite concentrate in sodium hydroxide was carried out under microwave and isothermal conditions. Experimental results showed that the leaching rate of tungsten was mainly affected by reaction temperature, reaction time, and tungsten grain size. The experiment was carried out at a temperature of 105 °C, 550 g•L^-1 sodium hydroxide concentration, liquid to solid ratio of 30:1, the holding time of 150min, stirring speed of 600rpm, particle size of 0.040-0.054mm, intensified by microwave. As a result, tungsten leaching rate can reach 99.53%. Compared with ordinary electric heating, microwave heating alkali decomposition of tungsten concentrate can save time.

Abstract: The 3D model of a large chamber, which is designed for vacuum electron beam welding machine, is established. Then using Ansys software analyzes the vacuum chamber under the condition of vacuum. According to the analysis, the strength of chamber is checked and the structure is optimized. The results support the design of large chamber used for vacuum electron beam welding machine, also provide a theoretical basis for further studying how the deformation of vacuum chamber influence the internal bench accuracy.

Abstract: (Na0.8K0.2)0.5Bi0.5TiO3 (NKBT20) lead free environmental protection thin films were deposited on Si(100), Pt/Ti/SiO2/Si(100), LaNiO3/SiO2/Si(100) and SrTiO3(STO)/Pt/Ti/SiO2/Si(100) by metal organic decomposition, and the effects of mismatch induced by different seed layers on microstructures, leakage current density, ferroelectric and dielectric properties of these thin films were investigated in detail. The NKBT20/STO thin film with single perovskite phase is of the largest grain size, dielectric constant, remnant polarization and the smallest leakage current density. This could be attributed to the fact that the optimum seed layers can lower the lattice and thermal mismatch between the seed layers and the thin film. The improved electric properties may make NKBT20/STO thin film a promising candidate in micro-electro-mechanical system.

Abstract: The effective stress principle for soil is inspected by examining the original concept and derivation of the principle from the perspective of the ultra-soft soil engineering applications; and the existing problems of the principle were discussed in accordance with the general methodology of mechanics, and relative engineering phenomena observed. The changes of pore water pressure and soil pressure with time were obtained based on series of long term in-situ test in a large ultra-soft ground treatment works directed by the first author; and then an important conclusion has acquired from the test, i.e. the effective stress principle is not a self-contained principle and it’s related to the medium constitutive characteristics and loading action mode.

Abstract: According to the properties request of energy storage flywheels running in high speed, chemical composition of a new ultra-high-strength steel has been designed. The designed steel specimen was prepared using intermediate frequency induction furnace and its transformation point, which had been simulated and calculated through J-Mat software in advance together with cooling curves, was investigated using by thermal dilatometer. Then the microstructure and mechanical properties of the designed steel have been evaluated by means of OM, SEM, durometer and universal material tensile tester. Simulation results showed that the pearlitic transformation of designed steel occurred at 687-453°C and bainite transformation at 453-340°C. Martensitic transformation started at 340°C and terminated at 220°C. The experimental results indicated that the casting microstructure of the designed steel was a duplex structure consisting of martensite and acicular bainite with a small amount of retained austenite. The austenization temperature ranged from 698°C to 790°C. The superior comprehensive mechanical properties of tensile strength of 1900MPa and elongation of 6.65% as well as the microstructure of tempered martensite was obtained after heat treatment.

Abstract: As one of the popular material used in the mould industry, Cr12 is always used as cold working steel. Although Cr12 has excellent hardenability, the hardened depth is definite.During the mould manufacturing, the following phenomena have always been met: the mould blank cracks in the forging process; capillary crack appears when the mould is still in its initial service stage which can lead to the mould discarding; tool heavily wear out or tool tipping in the rough cutting mould blank after preheat treatment. In the light of these problems,analysis of forging properties, heat treatment process performance and cutting performance of the mold steel Cr12 is done and the corresponding solutions is put forward in the manufacturing in order to keep mould quality, reduce reject rate, improve mould life and optimize process performance totally.Favorite application results were obtained and they can give guidance in the mould industry.

Abstract: The blends of thermoplastic polyurethane (TPU) with natural rubber (NR) were prepared via melt mixing technique, at four different blending temperature at range 180°C - 210°C and mixing times of 8, 10, 12, 14 min. The effects of both mixing parameters on tensile strength of the blends were investigated. The blend of 85TPU15NR shows the maximum tensile strength at 180°C and 10 min mixing. The viscosity of the polymer blends will decrease as the temperature increased. The movements of molecules are more worthy because of the poor molecules interaction. The increasing of mixing time will increase the compatibility of the blends and also increase in mechanical properties. Mixing time and mixing temperature are important parameters in acquiring blends having optimum mechanical properties.