Sumitomo Metal Industries, Ltd. (SMI) has developed a new temperature measurement method (Fountain pyrometer) and an associated control system, for hot strip cooled by water in cooling banks.High tensile steel is seeing increasing use in lightweight cars to improve fuel economy and reduce CO2 emissions. Reliable material quality of hot strip products, including high tensile steel, requires good temperature control on the run-out table. The conventional control method is not good enough because the temperature of a hot strip cannot be accurately measured in the cooling banks, where the cooling water interferes with thermal radiation from the hot strip surface.SMI has developed the Fountain pyrometer, which uses a water purge to stabilize the passage of thermal radiation from the hot strip surface. Experiment confirms that Fountain pyrometers can reliably measure hot strip temperatures above 360 degrees Centigrade even in cooling banks with a great deal of cooling water. The response time of Fountain pyrometers is 10 or 20 ms. SMI has also developed a new control system using Fountain pyrometers, a combination that allows very precise temperature control of hot strip on the run-out table.
In order to control organic coating thickness on steel sheet, two types of coating thickness gauges using a new method and the Brewster angle method has been developed for on-line monitoring . The new gauge has an on-line accuracy of +O.2um and the Brewster angle method gauge has an on-line accuracy of A portable oil thickness gauge has been also developed to measure the oil thickness easily in various 2 . INTRODUCTION Some kinds of organic coated steel sheet are widely produced for electrical appliances and automobiles.The coating thickness is one of the important qualities which determines the weldability ,corrosion resistance , and so on. In order to control the coating thickness less than 2um, two types of infrared coating thickness gauges have been developed for on-line coating thickness monitoring. When the infrared ray is applied to the coating film, the ray is absorbed within the coating film. The coating thickness is therefore measured using reflected intensity. However, the reflected ray is affected by not only the absorption but also the interference effect and a pass line variation. In this case, the interference effect occurs because of multiple reflections on air-film and film-steel interfaces. As there are several types of substrate with different surface roughness and reflectance, the degree of interference effect is different. The relative distance between the gauge and steel sheet changes while the steel sheet is moving. The degree of the change in the distance depends on the coating line where the gauge is installed. In the case of large pass line variation, a new method, called the four wavelength method, has be developed and in the case of strong interference effect ,the Brewster angle method1' was adopted.Demand for oil film thickness control has risen recently. So a portable oil thickness gauge using the Brewster angle method has been developed in order to measure the thickness of oil film easily in various places, for example, to adjust the oil coating machine. FOUR WAVELENGTH METHOD .PrincipleThe intensity of infrared ray which is transmitted through a film and at a wavelength equal to the absorption band of the film is given as: aL=log (1) where It denotes transmitted intensity, Ii denotes incident intensity, L denotes film thickness, and a denotes absorptivity. A reflected intensity spectrum of a coated O-8194-0668-6/91/$4.OO SPIE Vol. 1540 Infrared Technology XVII (1991) / 709 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/15/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx
A continuous sinusoidal wave (10 Hz) potential was supplied to the intermediate grid (G2) of a special three-grid Bayard–Alpert (BA) gauge. The ion collector current corresponding to the instant maximum potential of G2 was regarded as Ion and that corresponding to the instant minimum potential was regarded as Ioff. It was confirmed that this peak-to-peak value, Ion−Ioff, was equal to the difference between the two dc currents, ΔI, which was obtained by manual switching modulation. In order to reduce the effect of noise, a low-pass filter was used. Although the waveform of the signal current was deformed by the filter, the error by this deformation was negligible. Corresponding to the modulation, a considerably strong induced current flowed in the collector circuit, and to avoid the effect of this current, two methods were used in conjunction. One was phase-sensitive detection and the other was compensation. The theoretical concept and electronic circuits are shown with some experimental data.
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