Advanced Materials Research Vol. 813

Abstract: A kind of environment-friendly Cr-free insulating coating for grain-oriented electrical steel is exhibited in this paper. The tensile stress and the magnetic properties for both Cr-free and Cr-containing insulating coating were measured. The results showed that the more the coating on the metal, the bigger the tensile stress produced. The contribution of the Cr-free insulating coating to the reduction in P_1.7/50 varies from 0.092 to 0.192 W/kg, while the reduction in P_1.7/50 by the Cr-containing insulating coating is from 0.066 to 0.177 W/kg, with the weight of the coating varies from 4 to 6.5 g/m². In comparison with the traditional Cr-containing insulating coating, the Cr-free coating produces larger tensile stresses in the metal, thus leads to better magnetic properties, especially in the magnetic losses. Keywords: grain-oriented electrical steel, insulating coating, Chromium-free, magnetic property, tensile stress

Abstract: In this study, roll-bonded Al/STS clad was heat-treated at various temperature (200-600 °C) for 1hour and then their mechanical performance and interfacial structure was studied. To estimate the mechanical properties of heat-treated clad materials at various temperatures, the tension tests were performed. For Al/STS clad heat-treated from 200 °C to 500 °C, no interfacial reaction layer was observed. Brittle intermetallic layer was observed between Al and STS, which induced the interface crack due to the large mismatch of the thermal expansion coefficient between two metal plates. XRD peaks from the interface region indicate the presence of Al₂Fe, Al₅Fe and Al₁₃Cr₂ in addition to Fe, Cr, Al and Mn. The UTS of Al/STS sheet was observed to follow the rule of mixture. One noticeable observation from stress-strain responses is that the fracture strain of Al/STS clad sheet increased markedly more than that of Al clad sheet by the increasing heat treatment temperature.

Abstract: The buffer made with polyurethane is widely used in light industry, automotive industry and mechanical industry especially in the electric cylinder of small and medium sizes because of its compact structure, economics and process ability convenient. Firstly, the properties of nonlinear material and the constitutive relation of the polyurethane were analyzed, above on which the compression and shear tests of the polyurethane material were conducted to determine its physics parameters. Then the mechanical tests of polyurethane material were simulated in the finite element simulation software ABAQUS by input the parameters obtained from the mechanical tests. The parameters were proved to be correct by the testimony of the result of the simulation and the mechanical tests. Then buffers of different sizes with practical condition were simulated. During the simulation, this paper researched the maximum deceleration of the mass block in models with different sizes of polyurethane buffers. Lastly, the size of the buffer with minimum volume which is agreed with the request of the maximum deceleration of the mass block is obtained by data handling, above on which a database was built.

Abstract: In this study high temperature deformation and creep behaviors of DS IN738LC were studied. The yield strength and the total elongation decreased gradually with increase of temperature from room temperature to 500°C. The tensile strength and ductility increased rapidly with increase of temperature from 500°C to 660°C. The flow stress of Inconel738LC increases with increasing temperature up to about 600°C in the presence of γ precipitates. For high temperature creep, the stress exponent was observed to increase from 3~9 in the lower stress region to 13~16 in the higher stress region. The significant change of the stress exponent is likely to be attributed to the inverse temperature dependence of flow stress at high temperatures in directionally solidified IN738LC.

Abstract: Here, we introduce the mathematical methods to quantitatively evaluate the change of the tissue to quenching. SAE 52100 sample was repeatedly quenched and the influence of this cyclic heat treatment was investigated. The repeated quenching process increased the retained austenite content and had little influence on the materials hardness. The prior austenite grain size was decreased and consequently, refinement of the martensitic phase in the material occurred. The higher content of the retained austenite (higher fracture toughness) and the refinement of the microstructure accounted for the higher fatigue properties of the repeatedly quenched material. Here we use mathematical homology to quantify these features.

Abstract: Test method for measuring austenite and martensite microscopic grain size of the steel is commonly done. Determination of average crystal density for the specimen is defined by JIS (Japanese Industrial Standards) in Japan. In general, this kind of determination is carried out by engineers. The results may depend on their skill, so automated tool to determine the grain size is needed. In this paper we try to apply homology method to analyze the structures. As the first trial, we apply this method to the figures on JIS. The result of homology is compared with the grain size defined in JIS. We can make sure the correlation between grain size and the homology value.

Abstract: How to achieve leap-forward development under local environmental restrains and how to integrate environmental externalities in economic efficiency are crucial issues for less developed regions and countries. Contrary to most popular opinions that exploring green growth will lower economic growth rate, and even stunt economic growth in less developed regions, this case study shows that less developed regions can realize their leap forward development while exploring green growth. In this case, Jiangxi province, a less developed region of Eastern China, successfully realized its leap forward with a green growth strategy within 3 years, by correctly exploiting its regional distinctive green advantages, restructuring by precisely choosing ten green industries, and overcoming the obstacles. The restructuring and development of Jiangxi province can be a good model for other developing counties to realize their green leap-forward development.

Abstract: In this paper, we study Spray welding technology has been widely used in our country, it is between the spraying and welding process, the workpiece surface after spray welding coating is thin and smooth, dilution rate is extremely low, the deposited layer and base metal metallurgy, high bonding strength, density, and coating no slag inclusion, porosity and oxidation is suitable for occasions with thin coating. In 45Mn parent metal, for example, this paper mainly introduces the application of the technology in production.

Abstract: The SiMo cast iron with 5.45 wt% of Al has been developed for using as an automotive exhaust manifold. Cyclic oxidation test of that alloy and the conventional SiMo cast iron was conducted at 850 oC in 5%CO₂+12%O₂+83%N₂ and 10%CO₂+12%O₂+78%N₂. It was found that oxidation kinetics of the SiMo cast iron alloyed with 5.45 wt% of Al was lower than that of the SiMo cast iron. An X-ray diffraction technique and a scanning electron microscope equipped with energy dispersive spectroscopy were performed for characterisation. Thermal oxide scale on the SiMo cast iron consisted of hematite, magnetite and silica, while it was mainly alumina, additionally with hematite and magnetite, for the SiMo cast iron alloyed with 5.4 wt%. Formation of the alumina promoted oxidation resistance of the later cast alloy.

Abstract: Aluminum rotor prone to have many casting defects especially large amount of gas and shrinkage porosity, which caused eccentricity, loss and noise during motor operation. Many attempts have been made to develop methods of shrinkage porosity control, but still there are some problems to solve. In this research, the process of vacuum squeeze die casting is proposed for limitation of defects. The 6 pin point gated dies which were in capable of local squeeze at the end ring were used. Influences of filling patterns on HPDC were evaluated and the important process control parameters were high injection speed, squeeze length, venting and process conditions. By using local squeeze and vacuum during filling and solidification, air and shrinkage porosity were significantly reduced and the feeding efficiency at the upper end ring was improved 10%. As a result of controlling the defects, the dynamometer test showed improved motor efficiency by more than 4%.