Papers by Keyword: Electromagnetic Stirring (EMS)

Abstract: For the semi-solid casting process it is very important to make high quality slurry with high speed and low cost. Recently the double-axis-electromagnetic stirrer is developed as the slurry-making tool. This stirrer has rotating magnetic field (RMF) and linear traveling magnetic field (TMF). This new technology shows several advantages in the quality of slurry. The cup design is also important to make uniform quality slurry. In this paper the new stirrer and its advantages from test report and technology of cup design is introduced.

Abstract: The electromagnetic stirring combined with mechanical stirring (EMSCMV) method was developed for preparing the AlSi9Mg alloy semi-solid slurry. The experimental results demonstrate that, the preparation of semi-solid slurry by EMSCMV is sufficient to obtain fine microstructure of billet. The primary -Al particles are small, spherical and uniform throughout the microstructure. When increasing the stirring power and the vibrating power, the size of primary -Al particles decreases while the shape factor increases, and its distribution is more uniform. The fine microstructure of billet prepared by EMSCMV was obtained at the stirring power of 2.0~2.4 kW and vibrating power of 0.8 kW.

Abstract: This work involved an evaluation of a Al-4wt%Si-2.5wtCu alloy to be used as raw materials in the thixoforming process. The alloy was produced by direct casting under electromagnetic stirring to obtain ingots of 250 mm length and 30 mm diameter. The alloy was analyzed to determine their morphology and rheological behavior in the semi-solid range. The tests included characterization of the microstructural evolution by subjecting them to re-heating treatment in two conditions of solid fractions, 45% and 60%, for 0, 30, 90 and 210 s. A compression testing device designed specifically to evaluate semi-solid materials was used to determine the rheological behavior, and the tests were performed at the same heating rate and hold times to determine the apparent viscosity. The use of electromagnetic stirring to produce the raw material was effective in producing alloy with very small grain/primary particle sizes (80 up to 120 µm). Based on the morphological evolution in the semi-solid state, the alloy showed only minor variations in grain/primary particle size and surface factor (SF) as a function of the different globularization heat treatment times, suggesting that all these alloys are suitable for production. The Al-4.0wt%Si-2.5wt%Cu alloy with 45% solid fraction presented apparent viscosity about 1.5 x106 Pa.s.

Abstract: In this study, a mathematical model was developed to simulate 2-D axisymmetric melt flow under magnetic field in a cylindrical container. The modeling of this process required the simultaneous solution of the turbulent Navier-Stokes equations together with Maxwell equations. The flow pattern in liquid bath was obtained using a two-equation κ-є turbulent flow model, which was further used to obtain the solute distribution. The governing differential equations were solved numerically using finite volume based finite difference method. The computed results, were found to be in good agreement with the measurements reported in the literature. The effect of stirring parameters on temperature homogeneity of the melt have been discussed and presented.

Abstract: In this paper, the methods of electromagnetic stirring and isothermal extruding were used to study the semi-solid forming performance of ZA27 alloys. Through summarizing and analyzing the stirring experimental results, the reasonable parameter combination of electromagnetic stirring is that inputting voltage is 180V-200V and stopping stirring temperature is 465°C-475°C and cooling method is quenching. After ZA27 alloys are stirred by using above parameter combination,the spherical microstructures are obtained.Then the billets which were prepared by using above reasonable parameter combination were reheated to semi-solid temperature range for isothermal extruding.The extruding ratio was 4.Because the recrystallization occurs during extruding,the grains of ZA27 alloys become smaller and more uniform after isothermal extruding and per unit extruding force of semi-solid ZA27 alloys decreases by 1/4-1/5 times than that of general casting ZA27 alloys.These results provide a reliable experimental basis for production and application of ZA27 alloys.

Abstract: In this paper, a comprehensive three dimensional mathematical model is built to investigate the effect of electromagnetic stirring (EMS) on continuous casting process of copper round billet. The electromagnetic field is simulated by ANSYS software and the thermal-flow field is simulated by FLUENT software. The coupling between electromagnetic field and thermal-flow field is implemented by user-defined subroutines. The simulation results have good agreement with the experiment ones. The results show that electromagnetic frequency and current intensity have significant influence on the fluid velocity, temperature gradient and sump depth. The optimum current intensity and frequency are found to be 40A and 10Hz respectively.

Abstract: A fine grain size generally leads to improved structural uniformity of magnesium alloys. AlN has been identified as a potential grain refiner and electromagnetic stirring may have great effects on microstructure and grain growth. This study will be focused on the effects of AlN particles and electromagnetic stirring on the as-cast structure of AZ31 alloys.The grain refinement mechanism of both methods on magnesium alloy and their interaction effects are also discussed.

Abstract: Magnetodynamic mixer-batcher is intended for adjustable inductive heating and controlled electromagnetic pouring of cast iron into crystallizers and moulds on automated casting lines, chill-mould casting machines, rotor casting machines. Also, mixer-batcher allows realizing the out-of-furnace treatment of liquid alloys. In comparison with conventional ladle pouring of grey cast iron, application of magnetodynamic mixer-batcher allows to reach more isotropic structure and properties on casting body, to increase 5-10% the mechanical properties of castings, and to refine both the metal matrix structure and dimensions of graphite inclusions. Moreover, using of magneto-dynamic mixers-batchers provides automation of pouring, economy of materials and energy re-sources, increasing productivity, and improvement of ecology.

Abstract: In order to systematically study the influence of surfacing current and magnetic field current on hardness and wear resistance of surfacing layer, longitudinal DC magnetic field was applied during plasma arc surfacing Co-based alloy on low-carbon steel. The hardness, wear resistance, microstructure and phase constitution of the surfacing layer were investigated through the tests of hardness, wear, SEM and XRD analysis. The results show that the surfacing current and magnetic field current must be matched properly to achieve the optimal properties of surfacing layer. The optimal values are obtained when the surfacing current is 160A and the magnetic field current is 3A, where the hardness is 43.7 HRC and the wear loss is 0.5493g. The proper electromagnetic stirring induced by electromagnetic field can not only refine the microstructure but also improve the hardness and wear resistance of the surfacing layer.

Abstract: A coupled numerical simulation of magnetic field and flow field was conducted basing on Φ250mm bloom during continuous casting with electromagnetic stirring.The distribution of the flow field was analyzed in different current and frequency.At the same current,the velocity first decrease and then increase as the frequency increase along the casting direction.At the same frequency, tangential velocity is dominant in the radial of EMS center,velocity increase with the current. Considered the results of numerical simulation,the optimized EMS parameters of Φ250mm bloom are the stirring current of 480A and the stirring frequency of 3Hz.