真空压铸过程中不同工艺条件对界面换热行为的影响

摘要

真空压铸可减小铸造过程中的"气隙"现象.基于不同压铸条件,如低速速度(VL)、高速速度(VH)、浇注温度(Tp)和模具初始温度(Tm),通过实验测量金属与模具界面的温度,采用反算法获得真空条件下界面换热系数.结果表明,真空系统的应用使铸件与模具更加紧密接触,明显提高界面换热系数值并减小铸件的晶粒尺寸;当浇注温度由680℃提高到720℃或低速速度由0.1 m/s提高到0.4 m/s时,界面换热系数峰值随之提高,而高速速度和模具初始温度对界面换热系数的影响可以忽略.%Vacuum die casting can reduce the "air entrapment" phenomenon during casting process. Based on the temperature measurements at metal?die interface with different processing parameters, such as slow shot speed (VL), high shot speed (VH), pouring temperature (Tp) and initial die temperature (Tm), inverse method was developed to determine the interfacial heat transfer coefficient (IHTC). The results indicate that a closer contact between the casting and die could be achieved when the vacuum system is used. It is found that the vacuum could strongly increase the values of IHTC and decrease the grain size in castings. The IHTC could have a higher peak value with increasing theTp from 680 to 720 ℃ or theVL from 0.1 to 0.4 m/s. In addition, the influence of theVH andTm on IHTC could be negligible.