Investigation On The Mold Filling Characteristics Of Gray Iron In The Epc Process With Unbonded Sand Molds

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 byanalyzing 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.