Study On Emissivity Characteristics Of Several Aluminum Alloys

With the wide application of aluminum alloy materials and the continuous improvement of china's manufacturing level,different industries have higher and higher requirements on aluminum alloy quality.In the smelting process of aluminum alloy,temperature is a very important parameter,the precise measurement and control of temperature are indispensable for the manufacture of high performance aluminum alloy materials.The precise temperature control plays a key role in the quality control and energy saving of aluminum alloy devices.Traditional temperature measurement methods(such as thermocouple contact temperature measurement)have been unable to meet the needs of mobile production of aluminum alloy devices.As a new temperature measurement method,radiation temperature measurement has been widely used in the production and processing of aluminum alloy devices in modern metallurgical industry.However,radiometric temperature measuring instruments often need to manually input the emissivity value of the object to be measured,the inaccuracy of the input emissivity will lead to the deviation of the temperature measurement results.Due to the changes of temperature,surface oxidation and surface morphology of de device in the actual production and processing process,the surface emissivity of the material will change.Therefore,in order to improve the smelting quality of aluminum alloy materials,it is urgent to accurately measure the emissivity data of aluminum alloy oxidation in the air at high temperature and explore its changing rules.The first chapter of this paper introduces the background and practical significance of emissivity research,describes the characteristics of material emissivity and its research status,summarize the characteristics of several materials emissivity measurement methods and the main research content of this paper.In chapter two,the basic theory of thermal radiation,the basic measuring instruments and the principle of common emissivity measuring devices are introduced in detail.In chapter 3,the emissivity measuring device used in this study is introduced in detail,and the calculating method of emissivity used in this study is described in detail.The normal spectral emissivity of aluminum alloy 6061 before and after oxidation was measured in the range of 5-14 ?m at temperature points 623,673,723,773,and 823 K in the fourth chapter.The influence of temperature,oxidation,wavelength and roughness on the emissivity distribution of the sample was investigated.The experimental results shows that the normal spectral emissivity of aluminum alloy 6061 increases with the increase of surface temperature and decreases with the increase of measured wavelength,the influence of temperature on emissivity is different at different wavelength.The surface oxidation of samples leads to an increase in roughness,which in turn leads to an increase in absorptivity and emissivity.The effects of oxidation effect on emissivity vary in different temperatures and wavelengths.At 723 K,surface oxidation can increase the maximum emissivity by 0.05.The spectral emissivity of aluminum 6061 increases with the increase of the oxidation time,and the change of the spectral emissivity with the oxidation time at the temperature of 823 K can be well fitted by the parabolic model.In chapter 5 of this paper,7 series aluminum alloy 7075 and 7150 are taken as the research objects.The emissivity data of two aluminum alloys in the range of 5-20 ?m wavelength between 523 and 823 K are measured by the emissivity measurement device set up by the experimental group.The influence of temperature,wavelength and oxidation time on the emissivity of the two aluminum alloys is systematically analyzed.The experiment results shows that aluminum alloy,7075 and 7150,two kinds of aluminum alloy spectral emissivity decreases with the increase of the wavelength,but on the same wavelength under two kinds of alloy of spectral emissivity trends have very big difference,along with the change of temperature aluminum 7075 without oxidation emissivity of the volatility increases with temperature,and aluminum alloy 7150 launch the oxidation of the rate increases with the rise of temperature,into a positive relationship,show material components has large influence on the emissivity.The values of emissivity of the two aluminum alloys increased with the increase of oxidation time.When the surface oxide film of the sample became stable,the values of emissivity hardly changed,indicating that the thickness of the oxide film no longer increased and the thermal radiation characteristics of the sample surface became stable.