Study On Interfacial Contact Heat Transfer Coefficient Of AZ31B And 9Cr2Mo

As the lightest new structural metal materials,magnesium and magnesium alloys are widely used in the automotive industry,electric bicycles,air transport,mobile electronics and other civilian areas,and the trend is growing.Magnesium alloy has a small sliding hexagonal crystal structure(HCP).Temperature has a great impact on the magnesium alloy microstructure changes,surface cracks and edge fissures in the magnesium alloy rolling process.Therefore,temperature control during magnesium alloy rolling temperature control during rolling is necessary to obtain the magnesium alloy sheet with high yield and good stability.The contact heat transfer coefficient is the most crucial factor of heat transfer between magnesium alloy sheets and rolls during rolling,directly determines the temperature control and temperature prediction of rolling process,It is of great significance for the industrial production of magnesium alloy sheet.In this paper,the related knowledge and basic theory of contact heat transfer coefficient were introduced firstly,the advantages and disadvantages of steady heat flow method and transient inverse heat transfer method were compared,a set of feasible experimental device for the contact heat transfer coefficient of AZ31 B magnesium alloy and 9Cr2 Mo alloy steel was designed based on the steady-state heat flow method;Secondly,according to the multiple sample,by changing the interface average temperature,load size,surface morphology and the direction of heat flow and other factors,the heat transfer coefficient of contact interface between magnesium alloy and roller was multiple combination experimentally measured,the data were collected and the experimental results were manipulated and analyzed in the use of computer software;Finally,the finite element software was used to simulate the inverse heat transfer,and the micro model of the roller and strip was established to analyze the heat transfer mechanismfrom the aspects of load and roughness.The analysis of the experimental results shows that: the contact heat transfer coefficient is not a simple linear relationship with the compressive stress;theinterfacial contact heat transfer coefficient approximately presented a power exponent increasing with temperature;the more smooth the surface of the specimen is,the larger the contact heat transfer coefficient is;when the direction of heat transfer is changed,the heat transfer coefficient of interface contact changes.It can be seen from the results of numerical analysis: when the two solid contact,temperature beating appears on both sides of the contact interface,and it is very obvious.When the compressive stress reaches a certain value,the asperity on the contact interface is deformed.At the same average contact interface temperature,the contact stress is bigger and the asperity becomes more obvious.When the applied load is constant,and the number of asperity bodies in the interface is small,the degree of deformation of the asperities obtained by simulation is more obvious.According to the results of inverse heat transfer simulation,the temperature curve predicted by the inverse heat transfer model is in good agreement with the measured temperature curve,among that the temperature predicted by the inverse heat transfer model at low temperature is higher than the measured one.