Estimation of the temperature of a steel product
A method for estimating the temperature of a steel product including 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.
1 . A method for cooling a steel product, having a temperature from 300° C. to 1600° C., the method comprising:
performing a cooling treatment during or following:
a hot rolling and the steel product has a temperature from 300° C. to 1100° C. and wherein in step B, TJ ranges from 300° C. to 1100° C., or
a continuous casting and said steel product has a temperature from 800° C. to 1600° C. and wherein in step B, TJ ranges from 800° C. to 1600° C.;
A. a calibration step including the steps of
i. measuring intensities (I),
at 5 wavelengths (λ) ranging from 0.9 to 2.1 μm, wherein one is from 0.9 μm to 1.35 μm, one is from 1.35 μm to 1.55 μm, one is from 1.55 μm to 1.85 μm, one is from 1.85 μm to 2.05 μm and one is from 2.05 μm to 2.1 μm, by a hyperspectral camera,
of the radiation emitted by the steel product having a known temperature (T REF ) in measurement conditions characterized by an emissivity of the reference (ε REF ) and a transmittance of a medium between the steel product and the hyperspectral camera (α REF ),
ii. computing a spectral attenuation coefficient C CALIB using the measured intensities (I) at the 5 wavelengths,
C
CALIB
=
I
P
(
λ
,
T
REF
)
=
ε
REF
·
α
REF
where P(λ, T REF ) is the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium, based on the Planck Law, at a wavelength (λ) and at a temperature (T REF ),
iii. repeating the steps i. and ii. for N CALIB different combination of reference emissivity (ε REF ) and transmittance of a medium between the reference and said sensor hyperspectral camera (α REF ) to obtain N CALIB spectral attenuation coefficients, N CALIB being an integer greater than 2,
B. a measurement step including the steps of
i. measuring, by the hyperspectral camera, intensities of the radiation emitted by the steel product, I, at the 5 wavelengths (λ) ranging from 0.9 to 2.1 μm,
ii. computing N T spectral attenuation coefficients C COMPUTE Tj, for N T temperatures (Tj) ranging from 300 to 1600° C. and for the 5 wavelengths, N T being an integer from 2 to 1300,
C
COMPUTE
T
j
=
1
P
(
λ
,
Tj
)
=
ε
COMPUTE
×
α
COMPUTE
where
P(λ, T J ) is the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium, based on the Planck Law, at a wavelength of λ and at a temperature T J , and
C. a comparison step including the steps of
i. performing a probability test for finding a most likely C COMPUTE Tj among the C CALIB
ii. estimating a temperature of the steel product, T REAL as being equal to the temperature T J of the most likely C COMPUTE T J ; and
adjusting the cooling treatment as a function of the estimated the temperature of the steel product, T REAL .
2 . The method as recited in claim 1 wherein the cooling treatment is performed during or following a hot rolling and the steel product has a temperature from 300° C. to 1100° C. and wherein in step B, T J ranges from 300° C. to 1100° C.
3 . The method as recited in claim 1 wherein the cooling treatment is performed during or following a continuous casting and said steel product has a temperature from 800° C. to 1600° C. and wherein in step B, T J ranges from 800° C. to 1600° C.
4 . The method as recited in claim 1 wherein in steps A)i. and B)i., the radiation intensities of 8 wavelengths (λ) ranging from 0.9 to 2.1 μm, wherein one is from 0.9 μm to 1.11 μm, one is from 1.11 μm to 1.15 μm, one is from 1.15 μm to 1.35 μm, one is from 1.35 μm to 1.55 μm, one is from 1.55 μm to 1.85 μm, one is from 1.85 μm to 2.05 μm, one is from 2.05 μm to 2.07 μm and one is from 2.07 μm to 2.1 μm are measured and in steps A)ii. and B)ii., spectral attenuation coefficients for the 8 wavelengths are computed.
5 . The method as recited in claim 4 wherein in steps A)i. and B)i., the radiation intensities at 5 additional wavelengths ranging from 0.9 to 2.1 μm are measured and in steps A)ii. and B)ii., spectral attenuation coefficients for the 8 wavelengths and the 5 additional wavelengths are computed.
6 . The method as recited in claim 4 wherein in steps A)i. and B)i., the radiation intensities at 42 additional wavelengths ranging from 0.9 to 2.1 μm are measured and in steps A)ii. and B)ii., spectral attenuation coefficients for the 8 wavelengths and the 42 additional wavelengths are computed.
7 . The method as recited in claim 4 wherein in steps A)i. and B)i., the radiation intensities at 92 additional wavelengths ranging from 0.9 to 2.1 μm are measured and in steps A)ii. and B)ii., spectral attenuation coefficients for the 8 wavelengths and the 92 additional wavelengths are computed.
8 . The method as recited in claim 1 wherein N CALIB is an integer from 2 to 1000.
9 . The method as recited in claim 8 wherein N CALIB is an integer from 20 to 1000.
10 . The method as recited in claim 1 wherein in step C)i., the probability test includes a dimensionality reduction on said C CALIB defining main components.
11 . The method as recited in claim 10 wherein in step C)i., the dimensionality reduction is performed with a principal component analysis.
12 . The method as recited in claim 1 wherein in step C)i., the probability test includes a projection of the C CALIB in a probabilistic model.
13 . The method as recited in claim 12 wherein in step C)i., said probabilistic model is a Gaussian mixture model.