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灰铸铁干砂消失模铸造充型特性研究
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摘要
研究灰铸铁消失模铸造法金属液充型过程的规律,对于消失模铸造工艺设计、铸件质量控制及流场和温度场的数值模拟具有重要意义。
     本文利用自行研制的32通道开关量/32通道温度模拟量计算机数据采集系统,用正交试验设计方法研究了工艺参数对灰铸铁消失模铸造充型速度的影响。通过线性回归,建立了线性回归方程,对影响充型速度的诸多因素——负压度、模样密度、涂料透气性、浇注温度、金属液静压头、内浇道尺寸、模样厚度进行了筛选。在正交试验的基础上,对所确定的主要工艺因素对于充型速度的影响进行了系统的测试,通过改变负压度、模型密度、浇注温度、金属液静压头、涂料透气性、浇注方案、模型几何形状等参数,研究了各工艺因素对充型过程的影响,获得了在各种条件下金属液充型的等时曲线图,通过对其进行分析,找出了金属液充型形态的规律,定量地确立了主要工艺因素对充型速度影响的规律。另外,研究了消失模铸造法铸型表面硬度、界面换热系数的变化规律。最后,对比分析了开关量采集到的流场数据与热电偶测温技术所获得的流场数据。结果表明:
     1灰铸铁消失模铸造充型过程中流动金属前沿呈放射弧线状向前充填。
     2试验条件下,工艺因素对充型速度影响作用由大到小的顺序为:负压度、模样
    
     西安理工大学硕士学位论文
    密度、浇注温度、金属液静压头、模样厚度、涂层透气性、内浇道面积。
     3 负压度是影响充型形态和充型速度的关键因素。用消失模铸造法得到健全灰
    铸铁件的基本条件是在-200mmhg~400nunhg的负压度范围内浇注。
     4金属液充型速度随模样密度增加而降低。
     5金属液充型速度随着浇注温度的升高,开始时增加,超过一定值后随着浇注温
    度的进一步提高,充型速度反而降低。试验条件下,在 1370oC左右金属液充型速度
    达到最大值。
It is important to investigate the mold filling behaviour of gray iron in EPC process for the proper design of casting technology, the quality control of cast and the simulation of flowing field and temperature field.
    The effect extent of processing parameters on mold filling velocity of gray cast iron EPC castings was studied at first using statistical experimental techniques with computer data acquisition system consisting of 32 channel on-off signal/32 channel temperature analogue signal developed by us. The effective linear regression equation was set up with regression analysis. Such factors as vacuum degree, pattern density, coating permeability, pouring temperature , metallostatic head, ingate area, foam thickness which effected mold filling velocity were filtrated preliminarily. On the base of statistical experiment, the influence of the main processing parameters on mold filling velocity were tested more systemetically . The influence of vacuum degree , pattern density , pouring temperature, metallostatic head , coating permeability ,pouring project, pattern shape on filling behaviour were studied ,and the filling law and characteristics were obtained by
    
    
    
    analyzing the isochronal contour maps of filling molten metal, then the effect law of main processing parameters on mold filling velocity can be grasped quantitatively. Moreover, the variation law of mold surface hardness and interface heat transfer coefficient were studied. At last ,the flowing field data acquisited by on-off signal and that acquisited by thermocouples using testing temperature technique were contrasted. The results indicate that:
    1. The metal front flows forward with radiation circular arc shape in the mold filling behaviour of gray iron EPC.
    2. In the case of this experiment , he influence of technology factors on the filling velocity in gray iron EPC is in the order of vacuum degree, foam density, pouring temperature, metallostatic head, foam thickness, coating permeability, ingate area.
    3. Vacuum degree is the major factor which influences the mold filling characteristics and the mold filling velocity.The vacuum degree should be controlled between -200mmhg and -400mmhg in gray iron EPC in order to produce a sound casting by EPC.
    4.The filling velocity of the molten metal at different pouring methods is in the order of side-, middle-and bottom gating system from fast to slow. The filling velocity of the molten metal at side-gating system is far higher than that at bottom-gating system.
    5.The filling velocity of the molten metal increases with pouring temperature at first, then decreases after pouring temperature is more than 1370癈 or so.
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