Effect of Pouring Process on the Microstructures of Semi-Solid AlSi_7Mg Alloy

The effect of different pouring temperatures and different pouring heights, the distance between the mouth of the pouring ladle and the top of the mold, on the microstructure of AlSi7Mg alloy have been researched in the paper. When the pouring temperature is close to the liquidus temperature, the primary α-Al in the billets of AlSi7Mg alloy solidified into spherical and nodular fine grains distributed homogeneously. The optimum pouring temperature for semi-solid AlSi7Mg billet with spherical or nodular primary α-Al is 615℃. At the same pouring temperature, the higher the pouring ladle, the more easily the spherical and nodular primary α-Al obtained in the semi-solid AlSi7Mg billet. When the pouring temperature is close to the liquidus temperature and the pouring ladle is relatively high, it is the great cooling rate, the flow of the molten alloy caused by pouring and the large simultaneous solidification region induced by the near liquidus temperature, that promote the formation of spherical or nodular primary α-Al.

Refinement of primary Si grains in Al–20%Si alloy slurry through serpentine channel pouring process

In this study, a serpentine channel pouring process was used to prepare the semi-solid A1-20%Si alloy slurry and refine primary Si grains in the alloy. The effects of the pouring temperature, number of curves in the serpentine channel, and material of the serpentine channel on the size of primary Si grains in the semi-solid A1-20%Si alloy slurry were investigated. The results showed that the pouting temperature, number of the curves, and material of the channel strongly affected the size and distribution of the primary Si grains. The pouring tempera- ture exerted the strongest effect, followed by the number of the curves and then the material of the channel. Under experimental conditions of a four-curve copper channel and a pouring temperature of 701℃, primary Si grains in the semi-solid A1-20%Si alloy slurry were refined to the greatest extent, and the lath-like grains were changed into granular grains. Moreover, the equivalent grain diameter and the average shape coefficient of primary Si grains in the satisfactory semi-solid A1-20%Si alloy slurry were 24.4 μm and 0.89, respectively. Finally, the re- finement mechanism and distribution rule of primary Si grains in the slurry prepared through the serpentine channel pouring process were analyzed and discussed.

Refinement of primary Si grains of A390 alloy slurry through serpentine channel pouring process

In this paper, the serpentine channel pouring process for preparing a semi-solid A390 alloy slurry and refining the primary Si grains of the A390 alloy, was used. The effects of the pouring temperature, the cooling water flow and the number of the curves on the size of the primary Si grains in the semi-solid A390 alloy slurry were investigated. The results show that the pouring temperature, the cooling water flow and the number of the curves have a major effect on the size and the distribution of primary Si grains. Under the experimental condition of the four-curve copper channel whose cooling water flow was 500 L·h-1 and the pouring temperature was 690 oC, the primary Si grains of the semi-solid A390 alloy slurry were refined to the greatest extent and the lath-like grains were changed into granular ones. Additionally, the equivalent grain diameter and the average shape factor of the primary Si grains of the satisfactory semi-solid A390 alloy slurry are 18.6 μm and 0.8, respectively. Further, the refinement mechanism of the primary Si grains through the serpentine channel pouring process was analyzed and discussed. In summary, the primary Si nuclei could be easily precipitated due to the chilling effect of the channel inner wall, thus the primary Si grains were greatly refined. Meanwhile, the subsequent alloy melt fluid also promoted the separation of primary Si grains from the inner wall, further refining the primary Si grains.

A Numerical Study of the Effect of Multiple Pouring on Macrosegregation in a 438-Ton Steel Ingot

In present paper, a ladle-tundish-mold CFD model and a macrosegregation model were utilized to investigate the effects of the multiple pouring （MP） process on the macrosegregation in a 438-ton steel ingot. Firstly, the model was partially proved as compared to the measured carbon distributions along the transverse sections in the riser of ingot. Then, the comparison between the single pouring （SP） and MP process has been carried out to study their influences on the macrosegregation in ingot. Besides, the predicted macrosegregation results in MP process which introduced the improved riser fixed with an insulating sleeve were compared with that in traditional MP process. The traditional MP process leads to certain favorable initial carbon distribution in the mold, which has some favorable influence on suppressing the positive segregation in ingot. The holding time of the low carbon in the riser is the main factor to suppress the positive segregation in ingot. Improved insulating sleeve can prolong the holding time of the low carbon in the riser and release the positive segregation in the riser of ingot. Improvement of the insulating effect of the riser is an efficient method to control macrosegregation in large steel ingot.