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Authors: Dong Bok Lee, T.H. Kim, J.H. Ko
Abstract: Stainless steel and Ti metal fibers having a diameter of 3 µm were produced from wires by multiple extrusions. The suitable sheath coating for stainless steel to extrude the core wires to fibers was the Cu coating having ~30 µm thickness. Zinc was not a suitable sheath coating, because Zn of the low melting point had diffused into the stainless steel wires during extrusion. The oxidation of stainless steel fibers produced using the Cu sheath coating oxidized rapidly above 750°C due to the high surface area of fibers. The utilization of the Cu coating as a sheath material to extrude the core Ti wires to fibers was not possible, because the highly reactive Ti wires resisted deforming to fibers.
273
Authors: J.M. Ahn, H.Y. Kim, T.H. Kim
Abstract: The effects of following four factors, which are laser power, assist gas pressure, cooling rate and scanning speed on the quality characteristics of laser cut 316L stainless steel tubes have been studied. 24 full factorial design and central composite design were used to evaluate optimum condition of process parameters. Regression analysis was used to develop empirical models for the combined effects of the independent process parameters on laser cut quality. As the results, it was observed that laser power, assist gas pressure and scanning speeds did the major effects on kerf width. The smallest kerf width was obtained with the condition of low laser power, assist gas pressure, scanning speed and moderate cooling rate. Calculated regression model was kerf width = 64.47 + 0.91W + 1.25P + 0.41S + 0.41C2 - 0.45P2
277
Authors: Changjiang Song, Zhen Ming Xu, Jian Guo Li
Abstract: The Electromagnetic Confinement and Shaping (EMCS) process is a crucibleless melting and mouldless shaping technology by alternating magnetic field. In this paper, stability of the shaping, effect factors of the electromagnetic force and the temperature field and the procedure of the EMCS process are systemically analyzed. The Results indicate that a good coupling of the temperature field and the electromagnetic force is important to stably shape for liquid metal, and the gravity force of liquid metal is more sensitive to change of the temperature (or the current through the inductor) than the electromagnetic force does above the melting point of the sample. Several stainless steel samples were obtained by EMCS process.
281
Authors: Zhen Hua Li, Mei Hong Liu, Jun Ruo Chen, Rong Feng Zhou
Abstract: A new nonlinear constructive model for description of temperature field of carbon steel axisymmetric body during the magnetic field quenching has been established based on thermo-magnetic coupling analysis. Using the model and finite element method, a numerical calculation program is developed with Microsoft FORTRAN 5.0, and cooling curves of center in a carbon steel sample of 30mm in diameter and 60mm in length during magnetic field quenching and common quenching are calculated and tested. Results showed that calculated cooling curves is accordant with corresponded tested cooling curves very well, and the calculated accuracy of temperature field during magnetic field quenching based on the new model is satisfactory.
285
Authors: Young Min Kim, Sung Kyu Kim, Nack J. Kim
Abstract: The yield ratio of various HSLA steels has been correlated with the materials constants of Swift equation. It has been shown that the materials constants, b and N, of Swift equation can be related to microstructural features such as the dislocation density and volume fraction of constituent phases. In particular, the constant b can be expressed as a function of volume fraction of constituent phases. It has also been shown that the yield ratio has a linear relationship with ln(b/N2). Since the microstructural features often have opposing effects on the values of b and N, careful control of microstructure is necessary to optimize the yield ratio and other properties. The possible way of decreasing the yield ratio without sacrificing other properties of HSLA steels is suggested based on the relationship between yield ratio and the materials constants of Swift equations.
289
Authors: Youn Bae Kang, In Ho Jung, Hae Geon Lee
Abstract: The MnO-SiO2-TiO2-Ti2O3 system is a key oxide system for well known “Oxide Metallurgy” for HSLA steel. However, the available thermodynamic data for this system are rare and even the available experimental data are often inconsistent with each other. In the present study, experimental and thermodynamic modeling studies have been carried out on the MnO-SiO2-TiO2-Ti2O3 system. High-temperature equilibration and quenching technique followed by EPMA (electron probe X-ray microanalysis) was used to determine liquidus temperatures and solid solubilities of the crystalline phases such as manganosite, rutile, spinel, pyrophanite, pseudobrookite, tridymite, etc. in the temperature range from 1200°C to 1550°C (1473 to 1823 K) under an atmosphere controlled by CO-CO2 gas mixture. These equilibrium data for the MnO-SiO2-TiO2-Ti2O3 system, combined with previously reported data for this system, were used to obtain an self-consistent set of optimized parameters of thermodynamic models for all phases. In addition, the application of the optimized thermodynamic database to oxide metallurgy was discussed.
293
Authors: Raghavan Subasri, Tadashi Shinohara
Abstract: A TiO2 coating when directly applied on copper plate showed an instantaneous ptype behavior, i.e. ennoblement of electrode potential on ultraviolet (UV) illumination though a copper plate when galvanically coupled to an ITO glass coated with TiO2 showed immediate lowering of electrode potential (‘n’-type effect) on illumination under deaerated conditions. The instantaneous p-type effect in the former case was attributed to the presence of a copper oxide layer present between the copper plate and the TiO2 coating. However, a prolonged exposure of the TiO2 coated copper plate showed an n-type effect under illumination after nearly 24 h, following which the electrode potential appeared stable and highly negative. This observation indicated that the photogenerated electrons in TiO2 are capable of reducing the copper oxide layer to ultimately realize the n-type effect of TiO2. The n-type effect could not be observed in aerated electrolyte solutions. The effect of different conditions in the ambience on the photoeffect of copper coated TiO2 will be discussed.
297
Authors: X.J. Hao, H. Ohtsuka
Abstract: The effects of a high magnetic field on phase transformation behaviors and microstructures in Fe-based alloys have been extensively studied. It was found that a magnetic field accelerates ferritic and martensitic transformation, changes the morphology of the transformed microstructures and increases the A3 and A1 temperature. In a magnetic field of 10 Tesla, the A1 temperature increases by about 15°C for Fe-0.8C, the A3 temperature for pure Fe increases by about 8°C and the martensitic transformation temperature Ms in 18Ni maraging steel increases by 20°C. Ferrite grains are elongated and aligned along the direction of magnetic field in Fe-0.4C and Fe-0.6C alloys by ferritic transformation, but elongation was not found in pure Fe, Fe-0.05C alloy and Fe-1.5Mn-0.11C-0.1V alloy. Aligned structure was not found either by pearlitic transformation in Fe-0.8C alloy or by cementite precipitation from martensite.
301
Authors: Yoshitaka Adachi, Fu Xing Yin, Kazunari Hakata, Kaneaki Tsuzaki
Abstract: Variant selection of bcc-Cr at the grain boundaries in a supersaturated fcc matrix was studied using a Ni-43Cr alloy. The preferentially selected variant was examined as a function of the grain boundary misorientation, the tilt angle between the {111}fcc plane and the grain boundary plane, and the orientation relationships with respect to both of the adjacent matrix grains.
305
Authors: Xiao Mu Zhang, Zhi Yong Zhang, Yun Peng, Zhi Ling Tian, Chang Hong He, Hong Jun Xiao, Cheng Yong Ma
Abstract: Aluminum alloy has being widely used in modern automobile and aeronautic industry. However, the welding of aluminum alloy, especially high strength aluminum alloy,is difficult. Porosities are usually brought in the weld metal. In this paper, MIG welding using mixed gas shielding is carried out. The characteristic shapes of porosity in weld metal are described, the mechanism of porosity formation is analyzed, and the factors that influence the tendency of porosity formation are studied. Experiment results indicate that by the use of mixed shielding gas of 38%He+62%Ar, the number of porosity is reduced, the width of HAZ and softened zone is decreased, and the mechanical properties of welded joint is increased.
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