Aluminum DC Research Articles

Design optimization of gate system on high pressure die casting of AlSi13Fe alloy by means of finite element simulations

The diecasting modern industries are moving towards the proof-of-concept methods based on finite element simulation (FEM), abandoning the traditional trial-and-error. Aluminum DC is a very complex process because the mold filling problems. In the new design production system approach, the FEM simulations play an important role, virtually recreating the entire casting phases. In this research, simulations were carried out using a commercial software to optimize the gates and runner’s design of a thin panel component in G-AlSi13Fe aluminum alloy actually realized in AA3004 sheet metal formed. Filling analysis was used to define the gate’s size, its correct positioning and the runner system design.

Growth of Tunnels during Aluminum DC Pulse Current Etching

High-purity aluminum foil was etched with DC pulse current in acids solutions at first time. Experiments indicated that tunnels morphology was influenced by current density, pulse duty-cycle and frequency of DC pulse current, tunnels began to grow when the current density reached to 0.8A cm-2, and tunnels grew along three directions to form a netlike construction in the surface of aluminum foil, which increased effectually surface areas of aluminum foil. In addition, when aluminum was etched in the solution of 1 N HCl +0.8 N HNO3,tunnels morphology shows that tunnel does not grow continually during DC pulse current etching, so it is a method to study the mechanism of tunnel growth, for example period of tunnel growth, velocity of tunnel growth. The experimental results are discussed according to tunnels morphology.

Electrohydrolysis of landfill leachate organics for hydrogen gas production and COD removal

Hydrogen gas production with simultaneous COD removal was realized by application of DC voltages (0.5–5.0 V) to landfill leachate. The rate and the yield of hydrogen gas production were investigated at different DC voltages by using aluminum electrodes and DC power supply. The highest cumulative hydrogen production (5000 mL), hydrogen yield (2400 mL H 2 g −1 COD), daily hydrogen gas formation (1277 mL d −1), and percent hydrogen (99%) in the gas phase were obtained with 4 V DC voltage. Energy conversion efficiency (H 2 energy/electrical energy) reached the highest level (80.6%) with 1 V DC voltage. Hydrogen gas production was mainly realized by electrohydrolysis of leachate organics due to negligible H 2 gas production in water and leachate control experiments. The highest COD removal (77%) was also obtained with 4 V DC voltage. Electrohydrolysis of landfill leachate was proven to be an effective method for hydrogen gas production with simultaneous COD removal.

Development of in-situ measuring methods for mechanical properties on semi-solid aluminum alloy

It is necessary to obtain the mechanical properties of semi-solid alloy in order to predict the occurrence of solidification cracking, one of the serious casting defects of aluminum alloy die-casting and DC casting, by computer simulation. New in-situ measuring method for mechanical properties on semi-solid aluminum alloy by horizontal tensile test, based on that of Oya and Kitaoka et al., was developed. The strain was determined by measuring the displacement between dendrites defined as the makers. Influence of gage length on the fracture strain was clarified. Fracture strain and tensile strength of semi-solid Al–7mass%Si alloy were obtained.

Effect of water cooling conditions on splash break occurance during aluminum DC casting

The cooling water used in vertical aluminum DC casting is generally induced to just under the mold to prevent molten aluminum break out. However, the cooling water leaks into the air gap between the mold and the surface of ingot, so water splashes over the top of the molten aluminum, resulting in uneven cooling. But the quantitative survey on the splash break behavior and the change in the cooling condition has not been conducted. Hence, to quantify the splash break condition and the cooling capability, we have made the “Cooling water simulator” capable of freely controlling the potential splash causing factors such as temperature of cooling water, water flow rate, air gap amount, and angle of the water flow, reproducing the splash, and measuring the heat transfer value. The experimental result reveals that the temperature of cooling water is not a factor highly influencing on heat flux and splash, but the splash behavior highly depends on three factors which are the water flow rate, the angle of water flow, and the distance between the cooling water hit point level and the cooling water exit level. And that the heat flux also increases when splash occurs. In addition, the splash break parameter was drawn based on the above three factors, and the correlation between splash break parameter and heat flux was clarified. Use of splash break parameter enables setting of the casting condition where the maximum heat flux is obtained while preventing splash.

Prediction method of crack sensitivity during DC casting of Al–Mn and Al–Mg series aluminum alloys

Since it has been difficult to predict a crack sensitivity depending on alloy composition during aluminum DC casting, a new prediction method based on a relation between calculated solid fraction and temperature was developed concerning Al–Mn and Al–Mg series aluminum alloys. In order to understand that the surface crack is located at ingot surface, two cracking modes were considered. They were due to “difference in strain between water chilling surface and mushy surface (crack mode Z)” and “difference in strain rate between surface and just inner surface (crack mode Y)”. It's common knowledge that the material is cracked at high solid fraction region since melt cannot go into a crack gap and ductility is very low. Therefore we assumed the high solid fraction region was from 0.75 to 0.95 (Region II) and set up two indexes which are calculated from temperature difference (ΔTII) and difference in a temperature drop per unit solid fraction (ΔRII/ΔTII) within the Region II. By using the both indexes, which were called “Brittle temperature range” and “Parameter of the strain rate difference” respectively, the crack sensitivities through DC casting experiments were suitably represented.

Modeling of plasma process data using a multi-parameterized generalized regression neural network

For characterization or optimization process, a computer prediction model is in demand. A new technique, to improve the prediction performance of conventional generalized regression neural network (GRNN) of plasma process data was presented. Genetic algorithm (GA) was applied to optimize multi-parameterized training factors of GRNN. To evaluate the technique, two data sets were collected from the etchings of silica and silicon carbide (SiC) thin films in inductively coupled plasmas. Both data sets called Data I and Data II were statistically characterized by means of 2 3 and 2 4 full factorial experiment plus one center point. The GRNN models trained with these data were tested with additional six and 16 experiments. A total of eight etch outputs were modeled and compared with conventional GRNN and statistical regression models. The five etch outputs comprising Data I include silica etch rate, aluminum (Al) etch rate, Al selectivity, profile angle, and DC bias. Data II consisted of three etch outputs, including SiC etch rate, surface roughness, and profile angle. Compared to GRNN models, GA-GRNN models yielded more than 40% and 15% improvements for all etch outputs comprising Data I and Data II, respectively. Similar improvements were also demonstrated with respect to statistical regression models. All these results reveal that a multi-parameterization of training factors and GA optimization is an effective technique to considerably improve the prediction performance of conventional GRNN model.

アルミニウム鋳塊のバットカール現象に対する熱・非弾性シミュレーション

In an aluminum DC casting slab, butt curl phenomena are recognized at the short side of its bottom region and they are prone to decrease the productivity through fatal defects such as hot cracking or metal bleeding. In order to evaluate the mechanism of butt curl growth, a thermo-mechanical finite element model has been developed, in which thermally induced strains and stresses associated with phase transformation (solidification phenomena) are simulated using an elasto-plastic constitutive equation based on an isotropic hardening rule and the Mises yield condition. Comparison of butt curls shows a good agreement between calculations and measurements within tolerance of ±20%. As a driving force of butt curl, it is found that a torque moment due to tensile stresses distributing along a mushy region makes the solidified bottom shell bent rapidly when the whole slab surface is covered with secondary coolant. The study on influence of casting condition on butt curl growth reveals that resultant variations of butt curl are almost consistent with practical experiences in the cast house.

アルミニウム連続鋳造鋳塊の冷却特性に及ぼす各種冷却因子の影響

Optimization of the secondary cooling conditions for aluminum DC slab casting is very important because they have a strong effect on the castability and the quality of slabs. The cooling capacities were evaluated by measuring the aluminum block temperature under various cooling conditions. The heat transfer coefficients were calculated with various factors changed. Those factors are the quality of block alloys, cooling surface conditions, amount of water fluxes, water temperatures, water impingement angles, mold lubricant mixing content, and CO2 gas mixing content. On the basis of the experimental data, the effects of above factors on heat transfer coefficients were quantified. For example, as the water temperature increased every one degree, heat transfer coefficient decreased about 1%, and as the mold lubricant mixing content to cooling water increased every 50 ppm, the coefficient decreased about 1%. It became clear that all cooling factors studied in the present work had a seriously influence on cooling capacities.

Mathematical modelling of surface segregation in aluminum DC casting caused by exudation

A mathematical model for the development of a segregated layer of exudated droplets during DC casting of aluminum ingots is established. The model accounts for the metallostatic pressure driven interdendritic melt flow through the mushy zone by a Darcy type equation, the surface segregation due to this melt flow, and the decrease of the total solute concentration in different positions of the mush as a result of the exudation. The solution domain for the governing differential equations is constituted by the mushy zone of the cast. The main physical phenomena included in the model have been studied in a simple one dimensional case study.