Study On The Relationship Between Casting Structures And Pressurization Parameter Of Counter Gravity Casting

The anti-gravity casting technology has the advantages of stable filling and is considered as an effective technical means to solve the problem of the inclusion of oxide film and inclusions.However,in actual production,for the aluminum(magnesium)alloy castings with complex structures,defects such as gas entrainment and inclusions will still occur when anti-gravity casting is used,which will affect the metallurgical quality and mechanical properties of the castings.In-depth disclosure of the formation and evolution of entrapment defects in anti-gravity casting has important theoretical and practical values for the preparation of high-quality castings and optimization of the casting process.Based on this,using the method of combining hydraulics calculation,similar physical simulation and production verification,the hydraulic characteristics of the anti-gravity casting mold filling process are studied to study the influence of the pressure and cavity section change on the gate speed.,And the effect of gate speed on the filling shape and mold filling stability,and the influence of the casting structure and the pressure process on the mold filling process.This paper establishes the physical model of anti-gravity casting that is close to the actual working conditions,and designs four typical cavity structures according to the degree of change of the cavity section.The VOF two-phase flow method was used to study the changes in equipment parameters,process parameters,and cavity sections.Effect on the speed of the gate.The results show that according to the variation of the gate speed,the filling process of the sudden expansion structure can be divided into the spreading stage and the filling stage.In the spreading stage,the gate speed rapidly increases first;in the filling stage,the gate speed shows three kinds of inconsistencies with different pressurization speeds: When the pressure is high,the gate speed continues to increase;When the speed is reasonable,the gate speed remains the same;when the pressurization speed is low,the gate speed first decreases and then remains unchanged.The time required for the spreading stage of the progressively-expanded structure is shorter and the gate speed is slightly increased.In the filling stage,the gate speed is always increasing.The higher the pressurizing speed is,the faster the gate speed increases.The rate of increase of the gate speed is always lower than the spreading stage.The filling feature of the collapsed structure is that when the molten metal flows into the small section,the speed of the gate decreases rapidly and then begins to have the characteristic of damping oscillation.During filling of the tapered structure,the gate speed slowly decreases.The greater the pressurization speed,the faster the gate speed drops and the smaller the speed amplitude.During the filling process of anti-gravity casting,the influence of the change of the pressurizing speed and the section of the cavity on the gate speed is equally important.