Steel Temperature Estimation Using Spectral Segmentation
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Solution Overview
Problem
Existing methods for measuring the temperature of a steel product during cooling operations, especially when water is present, suffer from significant measurement errors due to the absorption or scattering of radiation by water, leading to inaccuracies of up to 200°C.
Innovation Solution
A method involving a calibration step to compute spectral attenuation coefficients using radiation intensities measured at specific wavelengths, and a measurement step to estimate the steel product's temperature by comparing computed spectral attenuation coefficients with those obtained during calibration, thereby accounting for the influence of water on temperature measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pyrometer is used to measure steel product temperature, then temperature measurement is enabled, but measurement precision deteriorates when water is present on the steel surface
Solution Approach 1:
The measurement spectrum is segmented into multiple wavelength bands (0.7-0.9 μm, 1.0-1.2 μm, 1.6-1.8 μm) to identify regions where water absorption is minimal. By measuring radiation intensity across these segmented spectral regions and selecting bands with lower water absorption coefficients, the method isolates the steel's thermal radiation signal from water interference, thereby maintaining measurement precision in the presence of water.
Solution Approach 2:
An optical glass is introduced as an intermediary element positioned between the pyrometer and the steel surface. This optical glass creates a controlled gap that allows radiation to pass through while minimizing the direct path of water vapor and droplets between the measurement target and sensor. The intermediary structure stabilizes the measurement environment and reduces the harmful effects of water on radiation-based temperature measurement.
2Temperature
If water spraying is applied for cooling operations, then cooling effectiveness is improved, but temperature measurement accuracy deteriorates
Solution Approach 1:
The cooling operation continues uninterrupted with water spraying applied to the steel surface, while the measurement system segments the spectral information to distinguish between radiation from the steel and radiation absorbed or scattered by water. This allows simultaneous achievement of effective cooling and accurate temperature measurement by separating the cooling function from the measurement function spectrally.
Solution Approach 2:
The water present on the steel surface, which normally causes measurement errors through absorption and scattering, is instead used as a diagnostic indicator. By analyzing the spectral characteristics of the measured radiation and identifying water absorption features, the system can compensate for water interference and even use the water's presence to infer additional information about the cooling process and surface conditions.
3Device complexity
If radiation intensity measurement is performed without compensation, then measurement process is simple, but measurement precision deteriorates due to water absorption and scattering
Solution Approach 1:
A calibration step is performed in advance to establish reference radiation intensity values for the steel at known temperatures and water conditions. These pre-determined compensation factors are then applied during actual measurements to correct for water absorption and scattering effects. This preliminary calibration approach enables accurate temperature measurement without requiring complex real-time calculations during the measurement process itself.
Solution Approach 2:
The measurement system incorporates feedback by comparing the measured radiation intensity across multiple wavelength bands against expected values based on the steel's emissivity and temperature. The discrepancy between measured and expected values provides feedback about water interference, which is then used to adjust the temperature calculation and compensate for absorption and scattering effects, improving measurement precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method improves the accuracy of temperature estimation for steel products during cooling operations, even in the presence of water, by reducing measurement errors and providing a reliable temperature reading.
Implementation Method 1
measuring the intensity, I, of the radiation emitted by the steel product
Implementation Method 2
P(λ, Tj) is the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium, based on the Planck Law
Implementation Method 3
absorption or scattering of the radian energy by water
Implementation Method 4
absorption or scattering of the radian energy by water
Data Source
Figure 1
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Figure 3~4
AI summary
The invention relates to a method for estimating the temperature of a steel product comprising a calibration step wherein the intensities at 5 wavelengths ranging from 0.9 to 2.1 μm are recorded for several measurement condition and spectral attenuation coefficients are computed, a measurement step wherein the intensities at said 5 wavelengths are recorded and spectral attenuation coefficients are computed for several temperatures and a comparison step wherein a probability test is performed to estimate the steel product temperature.