Study On The Effect Of Surface Oxidation Of Continuous Casting Billet And Water Mist Medium On Radiation Temperature Measurement

Continuous casting is one of the important processes in iron and steel production.Surface temperature of slab is an important signal for judging secondary cooling system and process index in continuous casting process,and an indispensable basis for dynamic control of secondary cooling in continuous casting process.However,due to the complex temperature measurement environment in the continuous casting area,the radiation temperature measurement of the slab surface is inaccurate.The main factors affecting the radiation temperature measurement that is water mist and surface oxide layer.The purpose of this paper is to explore the errors of radiation temperature measurement to slab;it is caused by water mist in secondary cooling zone of continuous casting and oxide layer on slab surface.The experimental equipment was developed,and it is used to simulate the effects of water mist and oxide layer on radiation temperature measurement in continuous casting area.The following work was done and the corresponding conclusions were obtained.?IF steel,45 steel and T10 steel were used as experimental materials to represent high,medium and low carbon steel respectively.The relationship is researched between the amount and rate of formation of oxide layer on the surface of IF steel,45 steel and T10 steel at different temperatures and different time.It is shown that the oxidation process of 3 kinds of steels follows the parabolic law,which is expressed as follows:?m=Kp · tand obtained the reaction rate constants Kp at different temperatures.Based on establish the isothermal oxidation models of 45 steel,IF steel and T10 steel,and the non.isothermal oxidation model was established based on the isothermal oxidation model.?Surface emissivity of slab will change after oxidation.Proper setting of emissivity of thermometer is the precondition of accurate temperature measurement.In this paper,it is concluded that IF steel,45#steel and T10 steel are not oxidized,and the emissivity should be set as follows:0.90 When the surface temperature of slab is measured by radiation thermometer.the emissivity of the oxidized billet should be set as follows when the surface temperature of the oxidized billet is measured;the emissivity of the oxidized billet should be set as follows:0.85,0.83,and 0.81.?Comparing the surface temperature and the real temperature of the slab during the cooling process,it is known that the surface oxide layer of the slab has a barrier effect on the heat transfer,resulting in the surface temperature measured by the radiation thermometer being lower than the true temperature.In this paper,the error caused by the surface oxide layer of the slab to the radiation temperature measurement is corrected by experiments,and the correction formula can calculate the true temperature,which is Ts=Tf+?Ty,and determine the correction coefficient.The real temperature of slab can obtain by calculating the thickness of oxide layer on the surface of slab with oxidation model.?In this paper,the error of monochromatic temperature measurement and two-color temperature measurement under the condition of water mist interference is studied,and the negative deviation of monochromatic radiation temperature measurement is obtained.The two.color radiation temperature measurement produces positive deviation,and the two.color radiation temperature measurement error is less than and more stable than the monochromatic radiation measurement.The effects of water mist thickness,atomization pressure,water spray volume and true surface temperature of the slab on the temperature measurement of two.color radiation was studied by single factor variable experiment method,which indicated that the influencing factors were positively correlated with the radiation temperature measurement error.After the analysis,the calculation method for the correction of the two-color radiation temperature measurement under the condition of water mist interference is obtained.The formula is TS=Tf-?TW.?Based on the correction of the influence of water mist and oxide layer on the radiation temperature measurement error,the CQUOTM-D on-line temperature measurement system for continuous casting slab surface is designed and developed,It realizes long-term,stable and accurate real-time monitoring of slab surface temperature,and realizes the function of short-range wireless transmission and long-distance wired transmission of temperature data.It has been successfully applied in a steel plant.