Experimental Research For Heat Transfer Coefficient Of A356/H13Steel Interface With Thermal-mechanical Coupling Effects Using Steady-State Method

In the casting process, the cooling speed of casting to a great extent determine thequality of castings, and casting cooling process is heat transfer by casting-mould andeventually to transfer to the surrounding process, so the casting-mould interface of theheat transfer in a great extent determined casting cooling speed. And in the numericalsimulation software, in order to simulate the mathematical model of the castings, wemust set right physical parameters, the initial condition and boundary conditions, heattransfer coefficient as the important boundary conditions coefficient, its setting corrector not directly related to the precision of the numerical simulation. Casting-mouldinterface heat transfer coefficient definition for the reciprocal of the thermal resistanceof casting-mould interface, it is the integrated embodiment of factors influence heatinterface. And casting-mould interface can be divided into casting-casting externalsurface and the casting-mould interface when exist mold cores, as the two interface indifferent heat transfer conditions lead to the two interfaces is not the same. The outsidesurface produces small gaps as solidification, and the interface in casting bag tensionforce by casting contraction and be in thermal-mechanical coupling conditions.In order to have a comprehensive understanding of the casting-mould interfaceheat mechanism, it is necessary to research the interface heat transfer coefficient ofcasting-mould. Adopted steady state method and the electrical measuring combiningexperimental methods, to casting-mold at the interface by the thermal-mechanicalcoupling as a starting point, based on the familiar with heat exchange theory,wedesigned a new experimental device which have good increase force and canmeasurement thermal-mechanical coupling interface heat transfer coefficient. Based onthis, we study the interface heat transfer coefficient influence factors and the influencelaw under thermal-mechanical coupling of A356and H13steel. Discuss the heattransfer mechanism under the condition of thermal-mechanical coupling interface. Thistopic research work mainly in the following aspects:①The article review the domestic and foreign heat transfer research condition,and summarize some basic viewpoints as well as the research methods in this area.Detailed analysis the heat transfer mechanism of the internal interface.②study the casting in the solidification state of the casting-mold interface heattransfer coefficient change rule. ③designed and a set ofcan be used for measuring casting-casting under thecondition of the interface coupled heat transfer coefficient experiment device on thebasis of a certain understanding in the heat transfer of the interface factors andmechanism, emphasizes on the temperature (including temperature difference)、interface loads and related factors of the interface heat transfer mechanism.④Study interface heat transfer coefficient underthe conditions of unilateralheating, found temperature difference have great influence on interfacial heat transfer,in order to eliminate the influence of the temperature difference factors, proposed anddesigned bilateral heating experiment, control the mold and casting temperature Toachieve control the effect of solidification process.⑤In bilateral heating condition, studytemperature (including temperaturedifference), interface loading etc to influence of the interface heat transfer coefficient,and probes into the interface of the heat transfer mechanism.Study heat transfer coefficient of casting-mold Interface with thermal-mechanicalcoupling effects get the following conclusion:①The influence of temperature to the castings-casting interface heat transfercoefficient is not only reflected in the temperature, but also reflect in the size of thetemperature difference in interface.Temperature difference when certain, interface heattransfer coefficient with the increase of interface temperature increase, but not a linearrelationship; Casting temperature when certain, interface heat transfer coefficient withthe increase of interface temperature difference decreases, both into inverse proportion.②The interfacial heat transfer coefficient increases with the increase of theinterface load, but the two are not a linear relationship; in the low load region, theinterfacial heat transfer coefficient with higher sensitivity of the load changes, as theload increases, decline in sensitivity between the two. There is a clear “turning point”phenomenon; with the increase interface temperature, the" turning point "to the left andto reach the" turning point "interface load is reduced.③To test the surfaceroughness of the samples after testing, found that the castingspecimens surface Ra value decreases with the increase of temperature and interfaceloads, and indicating that the roughness of the interface heat exchanger is influential.