Impact of Local Cathode Electrical Cut-Off on Bath–Metal Two-Phase Flow in an Aluminum Reduction Cell

Many researchers have investigated the impact factors of the bath–metal flow in an aluminum reduction cell using the simulation method. However, only a few have coupled their models with transient electromagnetic force, which makes the model closer to realistic conditions. In this work, coupling with the transient electromagnetic force, a three dimensional bath–metal two-phase quasi-steady flow model for a full 500 kA cell was built, and the model was validated with the metal velocity and the bath–metal interface deformation measurement in industrial cells. The impacts of local cathode electrical cut-off (LCEC) on the melt flow field were simulated according to six industrial cases. We found that the LCEC has little impact on the general pattern of the melt flow field, but the local metal velocity and the interface deformation would be changed to a certain extent. LCEC at positions A2A3 and A10A11 (as introduced in the full text) could suppress the interface hump at the central downstream area of the cell, with the anode cathode distance (ACD) increased by 3% and 7.5%, respectively. LCEC at positions A18A19 and A22A23 would deteriorate the interface hump condition, with the ACD decreased by 4% and 3%, respectively. The solution given in this paper is to cut the cathode flexes partially at abnormal positions to stabilize the melt flow field.

Measurement of Metal Velocity in Sand Casting during Mold Filling

Melt turbulence during mold filling is detrimental to the quality of sand castings. In this research study, the authors present a novel method of embedding Internet of Things (IoT) sensors to monitor real-time melt flow velocity in sand molds during metal casting. Cavities are incorporated in sand molds to position the sensors with precise registration. Capacitive and magnetic sensors are embedded in the cavities where melt flow velocity is calculated by using an oscillator, the frequency of which is sensitive to changes in the close field permittivity, and change in magnetic flux, respectively. Their efficiency is investigated by integrating the sensors into 3D sand-printing (3DSP) molds for conical-helix and straight sprue configurations to measure flow velocities for aluminum alloy 319. Experimental melt flow velocities are within 5% of estimations from computational simulations. A major benefit of 3DSP is the geometrical freedom for complex gating systems necessary to reduce turbulence and access to mold volume for sensor integration during 3DSP processing. Findings from this study establish the opportunity of embedding IoT sensors in sand molds to monitor metal velocity in order to validate simulation results (2–5% error), compare gating systems performance, and improve foundry practice of manual pouring as a quality control system.

Study on Refining Mechanism of Primary Si in Semi-Solid Al-25%Si Alloy Slurry Prepared by Rotating-Rod Induced Nucleation

In this paper, a new method for preparing semi-solid Al-25%Si alloy slurry named as Rotating-Rod Induced Nucleation (RRIN) was adopted. In this method, liquid metal (velocity 0.66 kg/s) flew toward a vertical stainless steel rod (45 mm in diameter) which was self-revolving on its axis. Molten alloy was spread around the rod surface under the effect of rotating, which caused supercooling and induced nucleation of primary Si in the molten metal. After spread around the rod, molten alloy flew off the rod and down to a graphite crucible. The influence of rotating speed on the microstructures in the semi-solid slurry was studied. The refining mechanism of primary Si was also analyzed according to the change of the spreading state, the number of primary Si particles (PSPs) in per unit area (N), and the distribution of PSPs size under a series of different rotating speeds (from 100 r/min to 1000 r/min, and at intervals of 100 r/min). The results showed that, under the lower rotating speeds such as 100 and 200 r/min, the molten alloy flew downward along the rod. With the rotating speed increasing, a molten alloy film around the rod was formed under the effect of the tangential force caused by the rotating rod, and the film thickness thinning, the spreading area and the N was increased. The uniform supercooling in the whole molten metal film was obtained under the condition of higher rotating speeds such as 500 and 600 r/min, which promoted nucleation of the PSPs significantly. It is called Rotating-Rod Induced Nucleation (RRIN). After spreading around the rod during short time, the molten metal film was thrown away the rod rapidly under the effect of centrifugal force, which prevented further supercooling and growth of PSPs. Under the condition of too higher rotating speed of the rod such as up to 700 r/min, the molten melt flew off from the rod apparently before spreading around the rod surface, molten metal film as mentioned above was destroyed, RRIN was weakened. The microstructure with fine PSPs (27 μm) was distributed uniformly in the semi-solid slab obtained under the condition of rotating speed of 600 r/min and pouring temperature of 785 °C in this experiment. Keyword: high silicon aluminum alloy; Rotating-Rod Induced Nucleation; Si phase; refinement.

Experiments on Eurofer Steel Corrosion by Pb-16Li

Corrosion samples of the EUROFER 97 steel were exposed to Pb-16Li in the LIFUS II loop at 480°C and 550°C, with a liquid metal velocity of about 0,01 m/s in agreement with the foreseen operative conditions of the HCLL (Helium Cooled Lithium Lead) blanket concept. The specimens were extracted after 1500, 3000 and 4500 hours exposure at the lower temperature, while a further time step of 6000 hours was added at the higher temperature. After extraction, weight change measurements and metallurgical analysis were performed on the corrosion specimens. The experimental results demonstrated a linear corrosion mechanism, together with no preferential elemental depletion of the steel in contact with the liquid alloy. In this paper the results are reported and discussed with reference to previous similar works.