| The surface temperature of continuous casting slab is am important parameter of production control, but its value can't be measured accurately for the execrable environment at the secondary cooling zone. Under conditions of the secondary cooling zone of continuous casting, the accuracy of surface temperature measurement of high temperature casting slab is frequently and greatly reduced by radiation characteristic of the water vapor, spray, water film and other participational media. This is the porblem that appears in secondary cooling zone of continuous casting and rolling mill which are modern metallurgy production units. Based on the theory and mechanism of radiation, absorption, scattering radiation characteristics of the participational media, this article studied the radiation characteristics of water vapor, spray and water film and the infection to temperature measurement of high temperature casting slab. Designed the on-line temperature measurement system of straightening section of casting slab for 4# CCM of Jinan Iron & Steel Group Corporation.The characteristic of water vapor is spectra selectivity. Generally described different kinds of spectral band model and approximate treatment for parameter of radiation characteristic. Studied the Edwards Indices broadband model and narrow spectrum band model.With the indices broad band model, calculated the emissivity at different temperatures and distances. At the same time, based on the high-temperature spectra line spectrum database (Hitemp), got the parameter database of narrow spectrum band model of water vapor. With these parameters and the principle of monochrome thermometers, Colorimetric Thermometer, calculated the errors under each operating wavelength. Pointed out that in the high temperature environment full of moist steam. It's suitable using thermodetector operating wavelength bound around 1.6μm, 1.0μm It can avoid the water vapor spectral absorption wave band, They are almost"translucent", nearly no influence. Or looks up the database to look for water vapor wave length its monochromatic emissivity for the amendment of Colorimetric Thermometer temperature measurement.This paper is based on Mie scattering theory, seted up the extinction model of the water spray particles at second cooling zone , analyzed the scattering properties , computed the extinction characteristic in various particle sizes and radiation wavelengths . It indicated the water spray particles were nongray, participant dissemination system. Under each grain-size distribution, it possessed intensely forward scattering properties and consecutively extinctive characteristic. It have influence on accuracy of both single and colorimetric thermometer temperature measurement. By theoretical analysis we got that: the spray particle size distribution and opreating wavelength is important attribute to its extinction characteristic. Its extinction increased with increasing of particle size. In the service wave band of infrared thermoscope, size distribution is the direct factor for extinction influence of water spray particles.Absorption coefficient of water film is only related to wavelength, thickness, with nothing to do with the temperature. Based on massive experimental data from predecessor, used 6 order polynomial to fit absorption coefficient under various wavelengths, obtained transmittance formula group and transmittivity on various wavelength and thickness. Studied errors of monochrome and colorimetric thermometer when there was vater film on the temperature measurement path of rays. Suggested selecting the service wavelength be shorter than the 1.1μm band for surface temperature measurement. And getting the revision.For 4 # continuous casting machine of Jinan Iron and Steel works, designed the temperature on-line analysis system on straightening section of continuous casting. Supplying water distribution optimization at secondary cooling zone... |
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