Fine grain mechanism of ultrasonic vibration depth in large diameter aluminum ingot hot-top casting
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摘要: 在直徑為650 mm的鋁合金熱頂半連續鑄造過程中施加雙源超聲振動系統, 研究3種超聲輻射桿浸入深度對鑄錠宏觀凝固組織的影響.基于鋁合金鑄錠凝固組織形貌的檢測結果以及ANSYS等有限元軟件對鑄造過程中聲場的仿真結果, 深入探討了超聲輻射桿在不同的施振深度下對鋁合金鑄錠凝固組織細化機制的影響.結果表明: 隨著超聲輻射桿施振深度的增加, 鑄錠截面組織整體進一步細化, 晶粒形狀由發達的枝晶變為等軸枝晶; 由于超聲輻射桿端面以及柱面存在幾個固定位置處振動波峰, 在鋁熔體中不同的超聲施振深度下存在不同的超聲空化范圍, 進而導致凝固組織的細化機制也不同.Abstract: With the development of the aerospace industry and the need for industrialized production, the casting processes of large diameter aluminum alloy ingot have come into focus in the industry. Among them, ultrasonic-assisted casting technology is widely used. Ultrasonic-assisted casting technology has the advantages of improving solute segregation of ingot and refining solidification organization. Other advantages have been widely reported. At present, most of the aluminum ingots used in the non-hot top ultrasonic casting process with very shallow liquid cavities, while the casting process does not involve the issue of ultrasonic vibration depth. With the use of a hot-top mold for ultrasound in the casting and casting process of large diameter ingot, the liquid level of aluminum melt is very high. The ultrasonic vibration depth will affect the cavitation range and finally affect the fine grain effect of the ingot. In the present study, a double source ultrasonic vibration system was applied in the process of semi-continuous casting of aluminum alloy with a diameter of 650 mm, and the influence of ultrasonic immersion depth on the macroscopic solidification structure of ingot was studied. Based on the test results of the solidified microstructure of aluminum alloy ingot and the simulation results of the sound field of the finite element software such as ANSYS, the mechanism of the microstructure refinement of the aluminum alloy ingot under different vibration depths was discussed at length. Study results show that, with increasing vibrational depth of the supersonic radiation rod, the whole cross section of the ingot is further refined, and grain shape changs from developed dendrites to equiaxed dendrites. Because of the end faces of the ultrasonic radiation rod, there is a vibrational peak at the fixed position, which leads to different ultrasonic cavities under different ultrasonic vibrational depths in the aluminum melt. This leads to different refinement mechanisms of the solidified structure.
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圖 1 鑄造及檢測示意圖(a)雙源超聲熱頂式鑄造；(b)凝固組織取樣位置
Figure 1. Casting and testing schematic: (a) hot-top dual-source ultrasonic casting; (b) solidified tissue sampling position
圖 3 不同施振深度的鑄錠顯微組織(Ⅰ—未施加；Ⅱ—110 mm；Ⅲ—190 mm；Ⅳ—280 mm；A—中心處；B—1/2半徑附近；C—邊部)
Figure 3. Different casting depths of ingot microstructure(Ⅰ— not working; Ⅱ—110 mm; Ⅲ—190 mm; Ⅳ—280 mm; A—center; B—near 1/2 radius; C—edge)
圖 5 不同施振深度下的聲場分布. (a)H=110 mm；(b)H=190 mm；(c)H=280 mm
Figure 5. Distribution of sound field under different vibration depths: (a)H=110 mm; (b)H=190 mm; (c)H=280 mm
圖 6 輻射桿柱面的聲場分布
Figure 6. Distribution of the sound field of the cylinder of the radiation rod
圖 7 不同施振深度的超聲作用機制圖.(a)H=110 mm；(b)H=190 mm；(c)H=280 mm
Figure 7. Different vibration mechanisms at the depths of the ultrasound mechanism: (a)H=110 mm; (b)H=190 mm; (c)H=280 mm
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圖 8 不同施振深度的輻射桿腐蝕形貌. (a) 未施加; (b) 110 mm; (c) 190 mm; (d) 280 mm
Figure 8. Radiation rod with different depths of shock corrosion morphology: (a) not working; (b) 110 mm; (c) 190 mm; (d) 280 mm
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參考文獻
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