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研究减压速度对真空吸铸A356合金充填行为和氧化膜卷入过程的影响。利用粒子图像测速仪通过水模拟方法观察充填行为,并获得速度场的变化规律。结果表明,介质流入型腔后,充型速度首先快速增加,随后随着减压速度的不同,充型速度的变化表现出3种不同情况:减压速度较大时,充型速度继续增加;减压速度合理时,充型速度保持不变;减压速度较低时,充型速度先降低后保持不变。充型速度越大,射流越严重,介质在重力作用下回落至液面时的速度越大,这是导致真空吸铸过程中氧化膜卷入的主要原因。推导了减压速度的设计原则,据此浇注了A356合金铸件。测试了其四点弯曲强度,并利用韦伯统计评价了铸件的可靠性,证明了减压速度设计原则的准确性。
The effect of decompression speed on the filling behavior of vacuum-sucked A356 alloy and the entrainment of oxide film was studied. Using particle image velocimetry, the filling behavior was observed by water simulation and the variation of velocity field was obtained. The results show that after the medium flows into the cavity, the filling speed firstly increases rapidly. Then with the different pressure reduction speed, the filling speed changes show three different situations: the filling speed continues to increase when the decompression speed is large; When the decompression speed is reasonable, the filling speed remains unchanged; when the decompression speed is low, the filling speed first decreases and remains unchanged. Filling the greater the speed, the jet is more serious, the media down to the liquid level under gravity, the greater the speed, which is leading to the process of vacuum absorption of the main reason for the involvement of the oxide film. Derived the decompression speed design principles, casting A356 alloy casting accordingly. The four-point flexural strength was tested, and the reliability of the castings was evaluated by Weber’s statistics. The accuracy of the design principle of the decompression speed was proved.