Contact Heat Transfer Coefficient Measurement And Research On Rolling Heat Transfer Mechanism Of AZ31B

This paper focuses on the study of the heat transfer mechanism and the change law of the contact heat transfer coefficient during the magnesium strip rolling process,and analyzes the relationship between the temperature of the magnesium strip rolling deformation zone and the rolling process parameters.Through the combination of experiment and numerical simulation,it is determined the optimal rolling process of the thinner gauge magnesium strip is proposed to control the rolling temperature of the magnesium strip.First,based on the steady-state heat flow method,a device for measuring the contact heat transfer coefficient suitable for magnesium alloys is built.The contact heat transfer coefficient of AZ31 B magnesium alloy was measured under multiple conditions,and the change of the contact heat transfer coefficient between the interfaces with the surface roughness,the interface pressure and the average temperature of the interface was mainly studied.Through COMSOL multiphysics modeling,the change law of contact heat transfer coefficient under high pressure is analyzed.Secondly,based on the rolling temperature measurement platform,the heat transfer process of magnesium strip rolling was measured,and the influence of variable working conditions parameters on the rolling heat transfer mechanism during the rolling process was deeply analyzed.The heat transfer process in the warm rolling of magnesium strips of different thicknesses is analyzed: the temperature of the magnesium strip after rolling is combined with air convection,radiation heat exchange,contact heat exchange with the roll,friction heat generation,plastic deformation heat,and internal heat transfer.The relationship between the temperature drop of the magnesium strip in the rolling deformation zone and the single pass reduction rate,inlet temperature,and magnesium strip thickness is analyzed:the temperature drop in the rolling deformation zone is basically proportional to the reduction rate.That is,the greater the reduction rate,the lower the exit temperature after rolling;the temperature drop in the rolling deformation zone is positively correlated with the rolling inlet temperature,that is,the higher the inlet temperature,the greater the temperature drop;as the thickness increases,the rolling The temperature drop in the deformation zone gradually decreases.Finally,based on the thermo mechanical coupled elastic-plastic finite element model of magnesium strip rolling,combined with the warm rolling experiment of magnesium strip and the variation of contact heat transfer coefficient,the value of contact heat transfer coefficient in the simulation model is determined;The effects of rolling speed and roll preheating temperature on rolling heat transfer were studied,and the optimal temperature system for different specifications of magnesium strip was established.When the roll preheating temperature is 150 ? and the rolling speed is 25 mm / s,the magnesium strip with 2 mm thickness should be preheated to 350 ? and the single pass reduction rate should be controlled at 10% ? 15%;1 mm thick magnesium strip: preheating temperature is 400 ?,single pass reduction rate is less than 5%.For 0.5mm thick magnesium foil,the rolling speed should be increased to 50 mm / s for rolling.At this time,the preheating temperature of magnesium strip is 400 ?,the roll is preheated to 150 ?,the reduction rate is less than 5%,and the temperature of rolling deformation zone meets the rolling requirements.Through the measurement of the contact heat transfer coefficient of AZ31 B and the study of the rolling heat transfer mechanism in this paper,it can provide theoretical support and experimental basis for the setting of multi-standard magnesium strip and magnesium foil rolling process.