Papers by Keyword: Electromagnetic Stirring (EMS)

Abstract: The effect of electromagnetic stirring on the inner quality and solidification microstructure of the GH 3030 superalloy ingots was investigated by casting experiments. As we know from the experiments, the solidification microstructure of GH3030 is the single-phase of austenite. With the electromagnetic stirring (EMS) the grains of the GH3030 ingots become finer significantly and the average grain size decrease as the currents of EMS increase. The results also show that the macrostructure of the ingots was improved significantly. The length of the shrinkage cavity with EMS become smaller and the porosity disappeared while the ingots without EMS have much porosity. And yet the macrosegregation always exists whether with EMS or not, but the chromium in the ingots with EMS is better distributed, and consequently the macrosegregation of chromium is inhibited.

Abstract: Numerical simulation and deposited experiment of MAG welding are carried out on the conditions of Electro-Magnetic Stirring (EMS) in this paper. Based on the research of EMS welding arc action, a simple EMS-MAG welding Gaussian distribution model using whole heat flux density is established, which MAG welding arc and droplet transfer are regarded as one integrated system. The important additional magnetic field parameter in EMS-MAG surfacing deposited welding is considered in this model. The computer-aided arc measurement system is used to analyze the effects of additional magnetic field in MAG welding. Effects of excitation current on welding penetration and width are analyzed by deposited experiments. Many deposited experiments are used to adjust model parameters and verify the simulation results. By defining key parameter and optimizing the model on the basis of experimental data, it can improve the simulation accuracy effectively. The results show that the established Gaussian distribution model can be used to simulate EMS-MAG welding process.

Abstract: The numerical simulation and application experiment are used to research the electromagnetic stirring (EMS) in Angang steel company limited. The results show that the stirring effect in side to side position of EMS rolls is better than that in face to face position. And the stirring effect in triples zero patterns are better than that in the double butterfly patterns. The application effect of EMS in Ansteel is obvious. The equiaxed zone in different steel grade such as low carbon aluminum killed steel, pipe steel, silicon steel and high carbon steel is improved 12-25% with EMS. And the slab center segregation has an obvious decreased after using EMS.

Abstract: Excessive iron in aluminum melt produces needle-shaped beta-AlFeSi intermetallic compounds during solidification. The presence of beta-AlFeSi intermetallic compounds can be harmful in the extrusion process because of the high pressure. As a common process, those compounds change from the needle-shaped to the globular-shaped alpha-AlFeMnSi intermetallic compounds through the addition of manganese to the aluminum melt. Those phases settle down during the solidification process, and then such is cut. Note, however, that the efficiency of iron elimination is very low. Our previous study reported that EMS can help the alpha-AlFeMnSi intermetallic compounds form easier and faster and settle down at the bottom of the aluminum melt through the centrifugal force of EMS. To investigate the effect on the efficiency of iron elimination in aluminum melt scrap, EMS current, holding temperature, and time of melt as well as the ratio of manganese to iron were controlled. As a result of this study, lower holding temperature and longer holding time of aluminum melt make iron elimination in aluminum melt more efficient with induced EMS. The best efficiency of iron elimination in aluminum melt was 65.2%with EMS induced at 923k for 4 minutes.

Abstract: The study on rheocasting has been conducted based on examination for destruction, growth, ripening of solid state in accordance with various changes in cooling. And flow characteristics of slurry for high liquid range rather than practical use has gotten attention. However, the characteristics of existing rheocasting and thixocasting are better mechanical property than competing process die casting but it’s competitiveness as automotive or electric electronic parts which cost of product is important. And productivity also has been decreased. Because die-casting techniques has been advanced such as vacuum, mold auto temperature control etc. Most of the work reported at this conference concerned the semi-solid processing of low melting point alloys, and in particular light alloys of aluminum and magnesium. Therefore, the aim of this study is to devise the original strength of semi-solid process by sequential semi-solid process. The size of primary solid particle and the degree of sphericity as a function of the variation in cooling rate, stirring speed, and holding time were observed. By applying electromagnetic stirring, primary solid particles became finer and rounder relative to as-cast sample. With this background, this research conducted electromagnetic stirring through slurry deliverance of sequential process through A356 alloy electromagnetic stirring pump (30Hz, 130A) with Sequential Semi-Solid Process device to assess the microstructures, primary particle size, degree of sphericity change in A356 alloy in accordance of solid-fraction, stirring speed, and stirring maintenance time.

Abstract: Effects of shape and distribution of the hard phases (Fe, Cr)7C3 and Cr7C3 on wear resistance of Fe5 deposited metal obtained by plasma arc welding with electromagnetic stirring were investigated. The deposited layers were subsequently characterized by SEM observation, wear tests and hardness measurements. The hardness of the deposited layers was increased and then decreased with increasing the applied current. With the current of 3 A and the electromagnetic frequency of 10 Hz, the hardness of deposited metal reached maximum value of about HRC 68, which was increased about 19% compared with that of the deposited metal without electromagnetic stirring. The wear weight loss of the deposited metal with 3 A and 10 Hz is greatly decreased. It is confirmed that the shape and the distribution of hard phase significantly affect wear resistance of the deposited metal. The slag M7C3 is transformed into hexagon during electromagnetic stirring with 3 A and 10 Hz. And the regular distribution of hexagon M7C3 in the deposited metal resulted in the excellent wear resistance.

Abstract: Al-Si alloy was melted by using vacuum induction melting furnace heated with medium-frequency induction and stirred simultaneously under Lorentz force. The experimental results were discussed with respect to the theoretical analysis of the Lorentz force on the molten alloy. It was found that Si phase tends to homogenize and aggregate along the direction of axis in the alloy under the effect of Lorentz force. With increasing stirring duration, Rod-shaped Si phase has a tendency to break and passivate on the edge. Vickers hardness measurement indicated that the microhardness of Al-Si alloy was improved after electromagnetic stirring. This result can be mainly attributed to the improvement in spheroidization of Si phase and aluminum phase.

Abstract: Through more than three decades of development, a semi-solid metal processing has been successfully established as a unique casting technique to produce a structural component for an automobile industry with high integrity and improved mechanical properties. A slurry-on-demand process to make the semi-solid slurry having a fine and globular microstructure has been very important in the semi-solid metal process. In the present study, the orientation distribution functions (ODFs) calculated from the pole figure data were examined and tried to characterize the bulky morphology of primary solid phase of the semi-solid slurry of Al-Cu alloy produced with various magnetic flux density of 100 to 300Gauss in the specially designed electromagnetic (EM) stirrer. Columnar dendritic structure of primary α phase was turned into a rosette and globular structure by EM stirring during solidification. The primary α phase was refined and globularized with increasing a magnetic flux density of EM stirring. Also, due to the EM stirring the tendency to random orientation was appeared. In the case of unstirred Al-Cu alloy the <110>//ND texture was developed strongly and <100>//ND and <111>//ND texture was weakly developed. But with the increase of the EM stirring strength, <100>//ND and <111>//ND texture were more strongly advanced. Due to EM stirring the texture was almost completely randomized.

Abstract: This paper focuses on fabricated slurry by electromagnetic stirring (EMS) with A6061 and A7075 wrought aluminum alloys. For this EMS process, it is important to find the optimal electromagnetic stirring conditions such as pouring temperature, stirring current and stirring time. After electromagnetic stirring according to each condition, the billets fabricated by EMS were investigated, as was the microstructure and cooling temperature of molten alloy which was directly cooled from liquid state to the semi-solid state during EMS. In use of cooling time and temperature data, it is possible to determine the forming time and stirring time required, respectively.

Abstract: Recently, a rheocasting process has been interested to produce a structural part for an automobile industry and so the slurry-on-demand process to make the semi-solid slurry having a fine and globular microstructure has been very important to produce a high quality and cost effective part in the rheocasting process. An electromagnetic (EM) stirrer employing for a slurry making process was designed and prepared to induce simultaneously both a circumferential and vertical fluid flow of a melt in order to control a rotation angle of EM stirring of a poured melt. In the present study, the semi-solid slurry of Al-15%Cu alloy was produced in the EM stirrer and its microstructure and the orientation distribution function calculated from the pole figure data was examined in accordance with a various rotation angle of EM stirring between 0˚ (circumferential flow) and 90˚ (vertical flow). The size and morphology of primary α phase was affected with a rotation angle of EM stirring and the finest and the most globular primary α phase could be obtained at a rotation angle of EM stirring of 45˚ and 60˚. Also, due to the EM stirring the tendency to random orientation was appeared. Also, the tendency of random orientation was the most at a rotation angle of 45˚ and 60˚. Therefore, it was considered that the rotation angle of EM stirring of 45˚ and 60˚ was the most effective to induce the non-dendritic growth of primary solid phase of EM stirred Al-Cu alloy.