Device and method for determining in real time the oxide
scale formed on the surface of semi-finished casting
products
Field of application
The invention relates to a process and device for
controlling a furnace for reheating the semi-finished steel
products. The device and the process according to the
10 invention make it possible to determine in real time the
total oxide scale formed on the semi-finished steel
products linked to the reheating of a product in the
furnace, by determining the amount of oxide scale that has
fallen into the furnace during the heat process and the
15 amount that has fallen after the descaling machine (or
descaler) . They also make it possible to determine the
amount of oxide scale that has remained attached on the
product after descaling.
This quantification is carried out by means of
20 electromagnetic sensors, the resolution of which makes it
possible to accurately measure the thickness of the oxide
scale and determine in real time the scale loss.
25
Prior art
The invention belongs to the field of furnaces for
reheating the semi-finished steel products.
During the reheating of a semi-finished steel
product such as billet, bloom or slabs in a heat treatment
furnace with a direct flame, the oxidation occurs at the
30 surface of products. The amount, the types and qualities of
oxide scale depend on the composition of the steels, on the
chemical composition of the combustion gases, on the
discharging temperature'?, on the residence times of the
product in the various zones of the furnace, on the various
35 temperatures in the furnace and on the heating curve of the
product along its passage through the furnace. Depending on
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the values of these various parameters, the oxide scale
that is formed at the surface of the product is more or
less significant in terms of quality, quantity and
characteristic.
The oxide scale, for example between 0.5% and 1% of
the weight of the furnace-charged product, leads to a loss
of material (scale loss) that is eliminated before entering
the rolling mill and that is not therefore converted to
finished product (wire, section or sheet), which
10 constitutes an economic loss for the operator of the plant.
15
Heating of the part of the steel lost in the form
of oxide scale leads to a loss of energy, a reduction in
the overall efficiency of the plant and an increase in the
production cost of the finished product.
The oxide scale may detach from the surface of the
products in the furnace during the passage of the products
while they are being heated. The accumulation of oxide
scale in the zones where it detaches may create deposits,
the extent of which disrupts the operation of the furnace
20 and necessitates the shutdown thereof for cleaning. This
shutdown time gives rise to losses of production of the
plant and is detrimental to its mean profitability over the
whole of the year.
The oxide scale that is formed on the surface of
25 the product must be removed before rolling, generally in a
descaler that sprays high-pressure water jets on the
surface of the product in order to detach the oxide scale
by thermal shock and mechanical action of the sprayed water
streams.
30 The oxide scale that is formed on the surface of
the steel product may remain adherent, it means that the
oxide scale may not be detached from the surface of the
steel product, neither in the furnace nor in the descaler,
and may follow the product into the various rolling units.
35 This situation may lead to defect on the surface of the
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finished product or even cause degradations of the rollers
of the rolling units or breakages of these rollers.
It is thus understood that the reheating process of
a steel product rolling line is greatly influenced by the
5 formation of oxide scale which may have a direct impact on
the quality of the finished product and/ or a significant
influence on the efficiency of the furnace, on its
consumption and on the production time between two
shutdowns for maintenance.
10 This situation may be made particularly difficult
for flat product furnaces which reheat a large amount of
products of different dimensions and different steel
grades. The steel products are treated according to heating
curves or settings of identical furnaces, which increases
15 the amounts of oxide scale and is detrimental to the heat
balance and economic balance of the furnace and also of the
whole of the rolling line.
The amount of oxide scale depends on the type of
heating carried out in the furnace. Figure 3 illustrates an
20 example of a heating curve of a product for its total
reheating time t 2 during its passage through the furnace
from charging temperature to the discharge temperature T2 •
Thus, figure 3 presents on the x-axis the heating (useful)
length of the furnace, or in an equivalent manner, the
25 residence time of the product in the furnace that it passes
through at constant speed. The total residence time equal
to t 2-t1 , the temperature of the surface of steel product
is above a temperature T1 , for example of 570°C, starting
from which this surface oxidizes under the action of the
30 oxygen present in the corresponding zone of the furnace.
It is understood that the residence time above the
oxide scale growth temperature and the content of oxygen
present in the combustion gases directly influence the
amount of oxide scale and also the its characteristics.
35 These parameters also influence the amount of oxide scale
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that is detached (or fallen) in the furnace during the
reheating
scale in
of the products,
the descaler and
the
the
detachment of the oxide
amount of oxide scale
remaining on the surface of the products that may give rise
5 to surface defects during the rolling operations.
State of the art
The oxide scale growth is considered to be an
inevitable component of the steel product reheating process
10 and even if it is recovered this recycling masks costs of
forming and treating this oxide scale.
Measuring the oxide scale during the reheating
process is carried out by studying samples deposited on the
product and reheated with it in the furnace. This method is
15 therefore essentially isolated and does not lend itself to
a continuous monitoring of the reheating process for each
of the products treated during this process.
20
Another method for measuring the amount of oxide
scale consists in weighing the removed oxide scale in the
descaler, in settling tanks
collection tanks discharged
of the descaling water or in
at the overhead crane. This
method is not precise since wet oxide scale is weighed and
it does not make it possible to measure the oxide scale
that is deposited in the furnace but only the oxide scale
25 that is removed from the descaler. Thus, there is an
approximation regarding the measurement of the amount of
oxide scale. Moreover, the times between weighings of the
oxide scale
measurements.
are long, around several
Lastly, the amounts of
hours between two
oxide scale weighed
30 may correspond to several batches of products reheated in
the furnace. Thus, the method is global and therefore
approximate.
The methods for measuring the amount of oxide scale
according to the state of the art are therefore isolated
35 and approximate. They cannot carry out a continuous
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monitoring of oxide scale growth in the furnace in order to
act in real time on the operating parameters of the
furnace.
Oxide scale, when it is taken into account by the
5 operator of the furnace, is managed according to standard
settings supposed to provide an average response to this
phenomenon irrespective of the dimensions of the products,
steel grades and heating cycles carried out.
In particular, furnace setting values are often
10 achieved that increase the amount of oxide scale produced
in order to make it possible to be within a comfort zone
for operation of the plant for which the oxide scale
detaches easily from the product during its passage through
the descaler for example, at the expense of the amount of
15 oxide scale produced and of the total cost of formation,
collection and treatment of this oxide scale produced.
The furnaces operate with several types of gas, for
example natural gas, mixed gas (mixture of several gases)
or coke oven gas. These various gases produce different
20 combustion gas compositions, the effects of which on the
oxide scale growth are different. These differences are not
currently taken into account in the control of the
furnaces.
One objective of the invention is to propose a
25 process for controlling a, furnace for reheating semifinished
steel products that resolves all or some of the
aforementioned drawbacks.
One objective of the invention is to overcome all
or some of the drawbacks of the state of the art, and/or to
30 improve the flexibility and simplicity of the control of a
reheating furnace while retaining or improving the
robustness and the cost of this control, of the maintenance
and/or of the operation of the means by which this
reheating furnace is controlled.
35
5
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Summary of the invention
At least one of these objectives is achieved with a
process for controlling a furnace for reheating semifinished
steel products, comprising:
a determination, for all or part of
amount of oxide scale formed by a
a product,
reheating
of the
of the
product part, this determination being carried out
using data measured relative to the part before and
after the reheating,
a correction of operating parameters of the furnace as
a function
determined so
formed by the
of the amount of oxide scale thus
as to modify the amount of oxide scale
reheating.
Thus, the measurement is carried out using data
15 specific to said product part.
Since the determination is carried out using data
measured on said part, the determination of the oxide scale
is simplified, the use of sample insertion and removal
steps and of physical and human means for carrying out this
20 insertion and removal are avoided.
25
Of course, the determination of the amount of oxide
scale may be carried out for the entire product.
Of course, the data measured after said reheating
and relating to said part may be measured after said
reheating or after the descaler.
The determination of the
using data measured on the product
amount of oxide
before and just
scale
after
the furnace, that is to say before the descaler, makes it
possible to deduce the amount of oxide scale which left in
30 the furnace.
The determination of the amount of oxide scale
using data measured on the product before and after the
descaler makes it possible to deduce the amount of oxide
scale produced during the whole of the process.
35 It is also possible to optimize the adhesion
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characteristics of the oxide scale on the product. This
optimization makes it possible to reduce the defects on the
rolled products.
Advantageously, the determination of the amount of
5 oxide scale in real time is carried out periodically or
continuously.
Advantageously, the correction of the operating
parameters of the furnace is carried out periodically or
continuously.
10 Unlike the prior art the process according to the
invention may be carried out easily, without disturbing the
conventional reheating process or rolling process.
Preferably, a determination of the amount of oxide
scale and/or a correction of operating parameters of the
15 furnace is carried out for each of the furnace-charged
products.
It is thus possible to continuously monitor the
oxide scale growth during the heat process in real time.
The determination of the amount of oxide scale may
20 be carried out continuously on all of the products entering
and leaving the furnace.
The correction of one or more parameters of the
furnace may be carried out continuously according to the
information or the data collected by the sensors or devices
25 installed on the furnace.
Thus, the invention provides a solution to the
continuous monitoring of oxide scale growth in the furnace
so as to optimize the quantity and quality thereof
produced. so that it is easily removed the oxide scale from
30 the surface of the products in the descaler and so that
this residual amount arriving at the rolling stands is as
small as possible.
The control process according to the invention may
comprise a determination of the portion of detached oxide
35 scale, for example by the movement of mobile and fixed
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skids or the supports of the products during the transfer
thereof over the entire length
When the portion of
of the furnace.
detached oxide scale
determined is greater than
example when this portion
a predetermined parameter,
is judged to be large,
thus
for
the
control process may carry out a modification of the furnace
parameters so as to modify the characteristics of the oxide
scale at the surface of the product, in particular by
increasing the adhesion to the lower skin of the product.
10 This modification may in particular act on a parameter such
as the excess air, the residual oxygen in the combustion
gases or the injection of steam or by the use of different
fuels in various zones of the furnace.
The measurements carried out on a part of the
15 product are performed on this same part of the product
before and after the reheating.
According to the invention, the data measured are
obtained by measuring the thickness of the product or else
its dimensions.
20 According to a first aspect of the invention, the
data measured are obtained by measuring at least one of the
dimensions of the product, this measurement being carried
out by electromagnetic sensors positioned before and/ or
after the reheating in order to determine the amount of
25 oxide scale formed at the surface of the product before the
descaler.
30
Preferably, the
oriented so as to observe
the product.
Preferably, the
electromagnetic
the lower and/or
electromagnetic
sensors are
upper faces of
sensors are
positioned so as to observe two parts of one and the same
surface of the product, one of the parts of this surface
bearing the oxide scale to be measured, the other part of
this surface having been cleaned, for example by partial
35 descaling.
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Advantageously the electromagnetic sensors are blue
laser sensors, i.e. the wavelength of which is between 405
and 473 nrn. Blue lasers are specifically well-suited to the
temperature level of the products and to the environment in
5 which the sensors are found. Tests carried out with red
lasers have shown that these are less accurate when the
product is at high temperature levels, for example, around
1250°C. Similarly, tests with white light sensors were less
conclusive, the measurements being disturbed by radiations
10 reflected on the product.
The sensors used emit an electromagnetic radiation
which scans a sector of the space on a plane P with an
angle of view and at a defined frequency. At a time t, they
thus see the surface of a transverse edge of the product.
15 The sensors are advantageously protected by thermal
insulation. They are for example placed in heat-insulated
and air-conditioned housings, a glass-ceramic window of
which allows the passage of the electromagnetic radiation.
According to another aspect of the invention, a
20 step that takes into account the expansion of the product
follows a measurement of the thickness of the product.
The determining step of the process according to
the invention may use a process for determining the scale
loss of at least one part of a steel product, referred to
25 as product, during the passage thereof through a reheating
furnace.
According to a second aspect of the invention, a
process is proposed for determining the scale loss of at
least one part of a steel product, referred to as product,
30 during the passage thereof through a reheating furnace.
The process according to the second aspect of the
invention uses a device according to the invention which is
described below. The oxide scale fallen from a surface
scanned by a sensor is determined by analysis of the relief
35 of the surface obtained by the sensor of the device.
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Preferably, the oxide scale present on a surface
scanned by a device is determined by analysis of the relief
of said surface obtained by said device.
According to a third aspect of the invention, a
5 process is proposed for determining the scale loss of at
least one part of a steel product, referred to as product,
during the passage thereof through a reheating furnace
which can optionally be combined with any other aspect of
the invention or one or more of the improvements thereof.
10 The process according to the third aspect of the
invention uses a device according to the invention which is
described below. An amount of oxide scale fallen into the
descaler is determined by the height difference of the
product between upstream and downstream of the descaler
15 determined by the processing of the data provided by the
sensors of the device.
Preferably, for each set of two electromagnetic
sensors, in order to determine the height of the product,
the height between the upper face of the product and the
20 generatrix of the roller determined by the sensor is
subtracted from the height of the product determined by the
sensor.
According to another aspect of the invention, which
can optionally be combined with all or some of the previous
25 aspects, the modification of an operating parameter of the
furnace comprises a use of a controlled injection of steam
into the furnace. The objective of this modification is to
act on oxide scale growth at the surface of the products.
According to another aspect of the invention, which
30 can optionally be combined with all or some of the previous
aspects, the modification of an operating parameter of the
furnace comprises an increase of the amount of combustion
air and/or oxidant injected into the furnace. The objective
of this modification is to act on the oxide scale growth at
35 the surface of the products.
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According to another aspect of the invention, which
can optionally be combined with all or some of the previous
aspects, the modification of an operating parameter of the
furnace comprises a use of particular atmospheres in
5 various zones of the furnace, in particular of atmospheres
having controlled oxygen contents. It is thus possible to
obtain residual values of oxygen that correspond to the
desired degree of oxidation. The objective of this
modification is to modify the quality and quantity of oxide
10 scale.
According to another aspect of the invention, which
can optionally be combined with all or some of the previous
aspects, the amount of products in the furnace lS adjusted
as a function of the desired production.
15 According to another aspect of the invention, which
20
can optionally be combined with all or some of the previous
aspects, the modification of an operating parameter of the
furnace comprises a use of several types of fuels for
supplying the burners
different atmospheres.
of the furnace and producing
The objective of this modification
is to reduce the amount of oxide scale.
According to another aspect of the invention, which
can optionally be combined with all or some of the previous
aspects, an operating parameter of the furnace comprises a
25 use of product heating curves.
According to another aspect of the invention, which
can optionally be combined with all or some of the previous
aspects, the process according to the invention comprises
an optimization of the amount of scale loss in and outside
30 of the furnace during the product reheating process.
According to another aspect of the invention, a
device is proposed for determining the scale loss in real
time of at least one part of a steel product, referred to
as product, during the passage thereof through a reheating
35 furnace located upstream of a descaler, the product
5
10
15
20
25
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preferably moving on roller tables, the device comprising a
set of electromagnetic sensors, which set comprises:
at least one electromagnetic sensor of said set being
arranged in order to scan, along a scanning plane, at
least in part, the face of the product in the vicinity
of the outlet of the furnace, said electromagnetic
sensor being oriented so that said scanning plane of
the electromagnetic radiation of said sensor is
perpendicular to a
a set of at least
upstream of the
run direction of the product,
two electromagnetic sensors placed
descaler and oriented so that the
scanning planes of the electromagnetic radiations
thereof are substantially on one and the same plane
perpendicular to the run direction of said at least
one part of the product passing through the generatrix
of a roller of a roller table, and a set of at least
two electromagnetic sensors placed downstream of the
descaler and oriented so that the scanning planes of
the electromagnetic radiations thereof are
substantially on one and the same plane perpendicular
to the run direction of the product passing through
the generatrix of a roller of a roller table, said
sensors being arranged in order to determine the
height of the product upstream and downstream of the
descaler.
According to another aspect of the invention, which
can optionally be combined with all or some of the previous
aspects, the sensors are arranged in order to scan the
upper face of the product and the sensors are arranged in
30 order to scan a side face of the product.
According to another aspect of the invention, which
can optionally be combined with all or some of the previous
aspects, the scanning planes of the electromagnetic
radiations of the sensors are inclined at an angle, denoted
35 a, with respect to the longitudinal axis of the rollers of
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the roller tables.
According to another aspect of the invention, a
device is proposed for controlling a furnace for reheating
semi-finished steel products, the device being configured
5 in order to implement a control process according to the
10
15
invention and comprising:
determination means configured in order to determine,
for a part of a product, an amount of oxide scale
formed by a reheating of said product part, these
means being used before and after said reheating,
means for correcting an operating parameter of the
furnace as a function of the amount of oxide scale
formed on the products thus determined, these
correction means being configured so as to reduce the
amount of oxide scale formed on the products by the
reheating.
According to another aspect of the invention, a
computer program product is proposed comprising program
code instructions for executing the steps of the process
20 according to any one of the claims according to the
invention when the program is executed on a computer.
The invention thus makes it possible to optimize,
continuously and for each reheated product or periodically
on a selection of reheated products, the operation of the
25 furnace by measuring the amount of oxide scale during the
passage of the products through the furnace and, from this
indication of quality and quantity, to deduce therefrom the
optimal settings to be applied to the reheating process in
order to reduce the amount of oxide scale and/or to control
30 the oxide scale growth thereof in the furnace to reduce the
energy consumption of the plant or reduce the rolling
problems of the products after the reheating thereof.
Description of the figures
Other distinctive features and advantages of the
35 invention will become apparent on reading the detailed
5
10
15
20
25
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description of uses and embodiments that are in no way
limiting, with respect to the appended figures in which:
FIGURE 1 presents a schematic view of a plant for
reheating a steel product;
FIGURE 2 presents a schematic view
descaling and rolling the product
reheating plant;
of a plant
reheated by
for
the
FIGURE 3 illustrates an example of a temperature curve
of the product during the heating time thereof in the
reheating plant;
FIGURE 4 schematically illustrates the implantation of
an electromagnetic sensor that will scan the surface
of a product according to the invention;
FIGURE 5 schematically illustrates the implantation of
an electromagnetic sensor that will scan the lower
surface of a product according to the invention;
FIGURE 6 schematically illustrates the implantation of
sensors that will measure the height of a product
according to the invention;
FIGURE 7 schematically illustrates the implantation of
a sensor according to the invention that will measure
the distance between the edge of a product and the
roller on which it rests;
FIGURE 8 schematically illustrates the implantation of
a sensor according to the invention that will estimate
the height of a product.
Description of the invention
Since these embodiments are in no way limiting,
30 variants of the invention could in particular be carried
out that comprise only a selection of features described
subsequently, as described or generalized, isolated from
the other features described, if this selection of features
is sufficient to confer a technical advantage or to
35 differentiate the invention with respect to the state of
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the art.
FIGURE 1 presents the principle of a steel product
rolling plant. A furnace charging machine 1, for example of
finger type, grasps a steel product 2 transported by a
5 roller table 3. The roller table 3 transports the product 2
in front of a furnace 4 for reheating semi-finished steel
products. The grasped product 2 is placed by the furnace
charging machine 1 in the furnace 4 on transfer frames (not
represented) .
10 During its passage through the furnace, the product
2 to be loaded into the furnace is gradually reheated
according to a predetermined heating curve, for example in
order to be brought from the ambient temperature outside of
the furnace 4 typically to a furnace discharge temperature,
15 on leaving the furnace, of between 1100°C and 1300°C.
A reheated product 5 is removed from the furnace by
a finger machine 7 and placed on another roller table 6
which discharges it to a rolling mill (not represented).
FIGURE 2 shows the roller table 6 for discharging
2 0 the reheated product 5 after it has left the furnace 4.
This product is moved by the roller table 6 to a deoxide
scaler 8. In FIGURE 2, the product within the de oxide scaler
8 is numbered 5'. The product 5' is exposed, in the deoxide
scaler 8, to high-pressure water jets 9, 10. The high-
25 pressure water jets 9, 10 are respectively oriented on an
upper and lower part of the product 5'. These water jets 9,
10 are arranged
at the surface
in order to detach the oxide scale formed
of the product 5' and to discharge the
detached oxide scale along a circuit 11 to settling tanks
30 (not represented) for the recovery thereof.
After descaling by the deoxide scaler 8, the
product is transported to the inlet of a rolling mill. In
the rolling mill, the product is referenced 5". The product
5" passes through various rolling sections 12a, 12b. The
35 rolling sections 12a, 12b are arranged in order to obtain a
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desired wire, section or sheet from the product 5".
In the state-of-the-art plants, the oxide scale
recovered in the circuit 11 is weighed in order to define
overall the mass recovered and the loss on ignition, that
5 is to say the relative amount of oxide scale produced
during the product reheating operation.
10
According to the invention,
continuously measuring the oxide scale
reheating is positioned at the outlet
optionally after the deoxide scaler.
a device for
produced by the
of the furnace 4,
This measurement
device is arranged in order to compare the amount of oxide
scale to limits set according to the heating method and to
the nature of the steel reheated in the furnace.
This comparison makes it possible to deduce a
15 heating efficiency of the furnace and to develop a
corrective strategy of the heating sui table for bringing
the oxide scale produced back to within the desired
quantity and quality limits.
FIGURES 4 to 8 present devices for continuously
20 measuring the oxide scale by measuring its thickness by
means of optical distance measurement sensors.
Measurement is carried out by optical analysis on
the width of the product and also on the length of the
product during the movement thereof in front of the sensor.
25 For each point of the zone scanned by a sensor, that is to
say of the surface of the product seen by the sensor, a
distance measurement is carried out with an accuracy of the
order of a micrometer which enables the measurement of the
actual height, that is to say of the thickness of the
30 product.
It is thus easy to calculate the volume of the
product, therefore its weight before and after reheating
with, by comparison, the amount of oxide scale discharged.
The measurement made also makes it possible to
35 evaluate the thickness of oxide scale formed and, thus, to
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compensate for the mass of oxide scale that is detached
from the product and that has fallen into the furnace and
into the de oxide scaler. It is also possible, by
calculation, to compensate for the expansion of the
5 products. These calculations may be carried out with simple
physical algorithms.
Seen schematically represented in Figure 4 is an
electromagnetic sensor 20, the electromagnetic radiation of
which scans the surface of the lower face of a product 5
10 while moving over a plane P20 according to an angle of
view. In this figure, the product 5 is represented in
transverse cross section.
The distance of the sensor with respect to the
product and the angle of view of the sensor make it
15 possible to cover the entire width of the product. When the
distance of the product and/or the angle of view of the
sensor do not make it possible to cover the entire width of
the product, several sensors are advantageously used to
cover the entire width of the product.
20
25
However, in order to limit the cost of the plant,
it is possible to only install a single sensor and to use
the data collected by this sensor in order to transpose
this data onto the surface of the product not covered by
the sensor.
It is thus considered, by approximation, that the
amount and the features of the oxide scale are the same on
the surface covered by the sensor and the surface not
covered by the sensor.
A portion of the amount of oxide scale fallen into
30 the furnace 4 is thus determined by at least one sensor 20
placed underneath the product 5, which scans the lower face
thereof.
Said sensor is placed at the outlet of the furnace
and as close as possible thereto.
35 The sensor produces a map of the relief of the
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lower face of the product while this product is running.
The analysis of the map of the relief of the surface of the
product makes it possible to determine the amount of oxide
scale fallen into the furnace. Specifically, the high
5 points at the surface of the product correspond to the
locations where the oxide scale is still present on the
product. Conversely, the low points correspond to the
locations at the surface of the product where the oxide
scale has detached and has fallen into the furnace.
10 The analysis of the data supplied by the sensor
makes it possible to determine possible singular points,
for example a point substantially higher than the average
of the high points.
scale has greatly
At this point, it is likely that oxide
detached from the product but has
15 remained present thereon. The statistical analysis of the
data supplied by the sensor makes it possible to take into
20
account these singular points, for example in order to
dismiss them during the processing of the data so as not to
disturb the determination of the thickness of the oxide
scale.
Since the sensor 20 is placed underneath the
product, it is necessary to prevent the oxide scale from
falling thereon and hampering its operation. For this, a
screen 15 that is inclined relative to the ground level is
25 placed between the product 5 and the sensor 20.
This screen must be substantially transparent for
the beam so as not to degrade the accuracy of the
measurement. It may for example be a glass-ceramic plate.
The inclination of the screen is selected so that
30 the oxide scale that falls onto the screen slides and does
not remain thereon.
Since the sensor is placed underneath the screen,
it is inclined by the same angle as the screen so as to
avoid any optical disturbance of the laser when passing
35 through the screen.
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For a finer determination of the loss of oxide
scale in the furnace, a sensor is placed on each side of
the product leaving the furnace. Just like the sensor
placed above the product, these sensors produce a map of
5 the relief of the side faces of the product while this
product is running in order to determine the amount of
oxide scale formed on said side faces that has fallen into
the furnace.
In the case where a single sensor is placed on one
10 of the faces of the product, the total amount of oxide
scale lost by the two faces of the product is estimated by
doubling that of the instrumented face of the product.
15
Advantageously according to the invention, a sensor
is also placed above the product leaving the furnace so as
to produce a map of the upper face of the product. As this
oxide scale predominantly remains present on the product
leaving the furnace, this map of the upper face is not
therefore used to determine the amount of oxide scale
fallen into the furnace. This map makes it possible for
20 example to detect a difference in oxidation on the upper
face of the products which may be useful for optimizing the
operating parameters of the furnace.
Seen schematically represented in Figure 5 is a
product 5 traveling on a furnace outlet roller table 6
25 along a longitudinal side view.
30
An electromagnetic sensor 20 is placed underneath
the product. Its electromagnetic radiation scans the
surface of the lower face of the product by moving over a
plane P20.
An inclined screen 15 is placed between the product
5 and the sensor 20. This screen makes it possible to
prevent oxide scale from being deposited on the sensor and
hampering its operation.
The sensor 20 is inclined by the same angle as the
35 inclined screen !.5 so that the scanning plane P20 of the
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sensor is perpendicular to the screen 15.
The amount of oxide scale fallen into the deoxide
scaler 8 is determined by two sets of sensors, the first
set placed upstream of the deoxide scaler, the second S€t
5 downstream of the deoxide scaler.
Each sBt of sensors comprises at least a first
sensor 30, 40 placed on the upper face of the product and
at least a second sBnsor 31, 41 placed on one of th€ sides
of the product.
10 The sensors 30 and 31 are placed upstream of the
deoxid€ scaler and the s€nsors 40 and 41 are placed
downstream of the dBoxide scaler.
Only the s€t of sensors 30 and 31 will subsequBntly
be described knowing that the layout of these sBnsors is
15 identical to that of th€ S€nsors 40 and 41.
The sensor 30 placed above th€ product is
positioned in a vertical line with a roller 14 of the
roller table on which the products move. It makes it
possible to measure the distance between the upper face of
20 th€ product 5 and th€ upper gBneratrix of the roller 14.
For a product resting perfectly on the support roller 14,
this distance corresponds to th€ hBight of the product.
The sensor is placed so that its measuring range
covers, at lBast in part, the upper face of the product and
25 at least one part of the upper generatrix of said roller.
The sensor is advantageously inclined by an angle
alpha relative to the longitudinal axis of said roller, for
example by an angle of 5°. This inclination makes it
possible to guarantee that the beam of the sensor covers,
30 at at least one point 18, the upper generatrix of the
roller. Specifically, if the sensor was positioned with its
measuring range parallel to the axis of the roller, it
would be necessary to have a perfect vertical alignment of
the sensor relative to the roller in order for the sensor
35 to see the upper generatrix of the roller and not a
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21
generatrix placed on a lower plane. This sensor also makes
it possible to measure the relief of the upper face of the
product covered by its measuring range.
The sensor placed on the side of the product is
5 positioned on the same vertical plane as the sensor placed
above the product, that is to say level with the generatrix
of the same support roller. When the sensor placed above
the product does not cover the two sides of the support
roller located on either side of the product, the sensor
10 placed on the side of the product is located on the side of
the roller of which the sensor located on the upper face of
15
the product sees the generatrix.
The sensor placed on the side of the product makes
it possible to correct the height of the product measured
by the sensor placed on the upper face when the product
does not rest exactly on the support roller.
for a deformed product that would not
generatrix of the roller, the height of
Specifically,
rest on the
the product
determined by the upper sensor would correspond to the sum
20 of the actual height of the product to be taken and that of
the gap between the lower face of the product and the
generatrix of the roller.
The combination of these two sensors enables an
accurate measurement of the height of the product. The
25 comparison of the height of the product measured by the
first set
scaler and
positioned
possible to
of sensors positioned upstream of the deoxide
the height measured by the second set of sensors
downstream of the deoxide scaler makes it
determine the loss of height of the product in
30 the deoxide scaler. This loss of height corresponds to most
of the oxide scale fallen into the deoxide scaler.
Sensors placed on the side of the product also make
it possible to produce a map of the relief of the face of
the product that they scan.
35 The analysis of the map of the relief of the face
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22
of the product makes it possible to determine the amount of
oxide scale fallen into the furnace, for the sensor placed
upstream of the deoxide scaler, and the amount fallen into
the deoxide scaler for the sensor placed downstream of the
5 deoxide scaler. Specifically, the high points at the
surface of the product
the oxide scale is
correspond to the locations where
still present on the product.
Conversely, the
the surface of
low points correspond to
the product where the
10 detached and has fallen into the furnace.
the locations at
oxide scale has
When the side sensors are only placed on one of the
faces of the product, the total amount of oxide scale lost
by the two faces of the product is estimated by doubling
that of the instrumented face of the product.
15 Seen represented in transverse view in Figure 6 is
a product 5 traveling on a roller table.
An electromagnetic sensor 30 is placed above the
product and scans a portion of the upper face of the
product and also a portion of the roller 14 of the roller
20 table located in a vertical line with the sensor.
The plane P30 over which the beam of the sensor
moves is perpendicular to the product and substantially
parallel to the axis of the roller 14 while being inclined
by an angle alpha relative to this axis.
25 The sensor 30 makes it possible to carry out a
first estimation of the height of the product 5 by
measuring the distance between the upper face and product
and the high point of the generatrix of the roller 14.
An electromagnetic sensor 31 is placed on the side
30 of the product and scans the side face of the product and
also a portion of the roller 14.
The plane P31 over which the beam of the sensor 31
moves is perpendicular to the roller and passes through the
axis of the roller. The upper generatrix of the roller 14
35 is thus on the plane P31.
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23
The sensor 31 makes it possible to analyze the
relief of the side face of the product and measure a
possible space between the edge of the product 5 and the
generatrix of the roller 6.
5 Seen represented in transverse view in Figure 7 is
an enlargement of figure 6 level with the sensor 31 showing
a deformed product 5, the side edge of which does not rest
on the roller 14. The sensor 31 thus makes it possible to
measure the height 16 of the space between the edge of the
10 product 5 and the generatrix of the roller 14. This height
is subtracted from the height of the product determined by
the sensor 30 in order to obtain the actual height of the
product.
Seen schematically represented in Figure 8 in a top
15 view is a product 5 traveling on a roller table, one roller
14 of which is represented.
An electromagnetic sensor 30 is placed above the
product and scans a portion of the upper face of the
product and also a portion of the roller 14.
20 The plane P30 over which the beam of the sensor
moves is perpendicular to the product and substantially
parallel to the axis of the roller 14 while being inclined
by an angle alpha relative to this axis. This inclination
of the sensor makes it possible to guarantee that the plane
25 P30 passes through the upper generatrix of the roller 14 at
a point 18. The sensor 30 thus makes it possible to carry
out a first estimation of the height of the product 5 by
measuring the distance between the upper face and product
and this high point 18 of the generatrix of the roller.
30 These various devices according to FIGURES 4 to 8
may be used at various steps of the manufacturing process,
in particular for demonstrating a difference in the
dimensions of the products or in the weight thereof which
is representative of the production of oxide scale in terms
35 of amount or behavior thereof.
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24
It is thus possible to demonstrate the amount that
may be deposited in the furnace during the reheating or
after the furnace during the uptake of the product by the
furnace discharging machine or at each step of the process
5 after the furnace, for example during the transfer of the
product to the roller tables, in the deoxide scaler or in
the various units of the rolling mill.
A person skilled in the art specifically knows how
to place such sensors around the furnace. The sensor is
10 protected in a water-cooled housing and aims through a
viewing window swept with cold air that maintains it at
temperature despite the radiation that it receives from the
furnace or from the product.
15
In particular, the advantage is understood
placing a device for measuring the product before
of
the
charging thereof into the furnace and also another after
the discharging thereof from the furnace or after the
deoxide scaler in order to obtain, from the difference
between these measurements, an image of the amount of oxide
20 scale produced and its behavior. It is also possible to
carry out several measurements, for example before the
furnace, on leaving the furnace and after the deoxide
scaler in order to better evaluate the various steps of the
life of the oxide scale.
25 The device described by FIGURES 4 to 8 may be
installed at the furnace inlet in order to define a volume
model of the product at
may be installed at the
the furnace charging thereof,
outlet of the furnace or at
it.
the
outlet of the deoxide scaler in order to produce a volume
30 model of the product after reheating and descaling.
The comparison of the models makes it possible to
learn lessons regarding the result of the heating. This
teaching may be used in particular to act on the settings
of the furnace in order to thereby modify the heating curve
35 and/or the control of the burners and/or the atmosphere in
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25
the chamber of the furnace and in particular the excess air
and/or a possible injection of steam into certain zones of
the furnace and/or to operate the furnace with reducing
zones and oxidizing zones and/or to modify the setting
5 parameters of the deoxide scaler such as water pressure,
number of descaling ramps used, feed speed of the product.
The capture of this information on the product,
before and after reheating, is processed by a computer
according to simple or elaborate physical model, for
10 example in order to take into account the behavior of the
oxide scale, an evaluation of the portion of the weight of
oxide scale that is deposited in the furnace during the
reheating, an evaluation of the oxide scale formed at the
upper surface of the product and at the lower surface
15 thereof. It is thus possible to take into account the
dropping of a portion of the oxide scale formed on the
lower face of the product during the transfer thereof on
the frames of the furnace or on the discharge roller tables
or else an evaluation of the residual portion of oxide
20 scale at the surface of the product after the descaling.
The invention thus proposes a computer program
product comprising program code instructions for executing
the steps of the process according to any one of the claims
according to the invention when the program is executed on
25 a computer.
It is also possible to envisage the use of a
computer program product, for example of fuzzy logic or
self-adapting type, for continuously analyzing the
formation of oxide scale on the product in order to
30 validate the action performed on the operation of the
furnace or to evaluate the changes in the oxide scale (in
terms of quantity and quality) over time according to the
process modifications performed.
It is seen that by means of the continuous
35 measurement of the amount of oxide scale formed at the
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26
surface of the product and of the operating system of the
furnace by computer, it is possible to continuously adapt
the operating parameters of the furnace according to a
predefined strategy or predefined objectives, for example
5 to reduce the amount of oxide scale provided, to stabilize
the amount of oxide scale produced at a predefined value as
a function of the nature of the product to be treated and
its treatment process, to modify the amount of oxide scale
produced in order to obtain a oxide scale quality suitable
10 for the process, for example for its discharging
characteristics in the deoxide scaler.
This process for continuously controlling the
furnace according to the measurement of the oxide scale
produced makes it possible to optimize the complete rolling
15 process and to optimize the energy consumption by reducing
the amount of oxide scale produced.
Of course, the invention is not limited to the
examples that have just been described and many adjustments
may be made to these examples without departing from the
20 scope of the invention. Furthermore, the various features,
forms, variants and embodiments of the invention may be
combined with one another in various combinations as long
as they are not mutually exclusive or incompatible.
wo 2016/125096
1
2
3
4
5
5'
5"
6
7
8
9
10
11
12a,
14
15
16
18
20
30
31
40
41
P20
P30
12b
27
Nomenclature
furnace charging machine
steel product
furnace inlet roller table
reheating furnace
steel product
product in the descaler
product in a rolling mill
furnace outlet roller table
furnace discharging machine
de scaler
upper high-pressure water jet
lower high-pressure water jet
discharge circuit
rolling sections
support roller
inclined screen
PCT/1B2016/050567
distance between the edge of the product
and a support roller
intersection between a plane P30 and the
upper generatrix of a roller
electromagnetic sensor scanning the lower
face of a product
electromagnetic sensor scanning the upper
face of a product upstream of the descaler
electromagnetic sensor scanning a side
face of a product upstream of the descaler
electromagnetic sensor scanning the upper
face of a product downstream of the
descaler
electromagnetic sensor scanning a side
face of a product downstream of the
de scaler
scanning plane of the laser of a sensor 20
scanning plane of the laser of a sensor 30
wo 2016/125096
P40
P41
P42
PCT/1B2016/050567
28
scanning plane of the laser of a sensor 40
scanning plane of the laser of a sensor 41
scanning plane of the laser of a sensor 42

CLAIMS
1. A device for determining the scale loss of at
least one part of a steel product (5), referred to as
product, during the passage thereof through a reheating
5 furnace (4) located upstream of a descaler 8), the product
preferably moving on roller tables (3, 6), said device
comprising a set of electromagnetic sensors (20, 30, 31,
40, 41), which set comprises:
10
15
20
25
30
at least one electromagnetic sensor (20) of said set
being arranged in order to scan, along a scanning
plane, at least in part, the lower face (50) of the
product ( 5) in the vicinity of the outlet of the
furnace ( 4) , said electromagnetic
oriented so that said scanning plane
electromagnetic radiation of said
sensor being
(P20) of the
sensor is
perpendicular to a run direction of the product,
a set of at least two electromagnetic sensors (30, 31)
placed upstream of the de scaler ( 8) and oriented so
that the scanning planes (P30, P31) of the
electromagnetic radiations thereof are substantially
on one and the same plane (P32) perpendicular to the
run direction of said at least one part of the product
passing through the generatrix of a roller of a roller
table (3), and a set of at least two electromagnetic
sensors (40, 41) placed downstream of the descaler (8)
and oriented so that the scanning planes (P40, P41) of
the electromagnetic radiations thereof are
substantially on one and the same plane (P42)
perpendicular to the run direction of the product
passing through the generatrix of a roller of a roller
table (6), said sensors (30, 31, 40, 41) being
arranged in order to determine the height of the
product upstream and downstream of the descaler
2. The device as claimed in claim 1, wherein the
35 sensors ( 30, 4 0) are arranged in order to scan the upper
face (51) of the product (5) and the sensors (31, 41) are
wo 2016/125096 PCTIIB2016/050567
30
arranged in order to scan a side face (52, 53) of the
product ( 5) .
3. The device as claimed in one or other of the
preceding claims, wherein the scanning planes (P30, P40) of
5 the electromagnetic radiations of the sensors ( 30, 4 0) are
inclined at an angle, denoted a, with respect to the
longitudinal axis of the rollers of the roller tables (3,
6) .
4. A process for determining the scale loss of at
10 least one part of a steel product, referred to as product,
during the passage thereof through a reheating furnace (4)
using a device as described in the preceding claims,
characterized in that the oxide scale fallen from a surface
scanned by a sensor (20, 31, 41) is determined by analysis
15 of the relief of said surface obtained by the sensor (20,
31, 41).
5 . The process as claimed ln claim 4,
characterized in that the oxide scale present on a surface
scanned by a sensor (20, 31, 41) is determined by analysis
20 of the relief of said surface obtained by said sensor (20,
31, 41).
6. A process for determining the scale loss of at
least one part of a steel product ( 5) , referred to as
product, during the passage thereof through a reheating
25 furnace ( 4) using a device as described in claims 1 to 3,
characterized in that an amount of oxide scale fallen into
the descaler (8) is determined by the height difference of
the product ( 5) between upstream and downstream of the
descaler determined by the processing of the data provided
30 by the sensors (30, 31, 40, 41).
7. The process as claimed in claim 6,
characterized in that, for each set of two electromagnetic
sensors (30, 31), (40, 41), in order to determine the
height of the product ( 5) , the height between the lower
35 face of the product and the generatrix of the roller
determined by the sensor (31, 41) is subtracted from the
5
10
wo 2016/125096 PCT!IB2016/050567
31
height of the product (5) determined by the sensor (30,
40) .
8. A process for controlling a furnace ( 4) for
reheating semi-finished steel products (5), comprising:
a determination, for at
(5), of an amount of
least one part of a product
oxide scale formed on the
products by a reheating of
determination being carried
said product part, this
out by the use of the
process described in claims 4 to 7,
a correction of operating parameters of the furnace as
a function of the amount of oxide scale thus
determined so as to modify the amount of oxide scale
formed by the reheating.
9. The process as claimed in claim 8, wherein the
15 modification of an operating parameter of the furnace
comprises a use of a controlled injection of steam into the
furnace.
10. The process as claimed in claim 8 or 9,
wherein the modification of an operating parameter of the
20 furnace comprises an increase of the amount of combustion
air and/or oxidant injected into the furnace.
11. The process as claimed in one of claims 8 to
10' wherein the modification of an operating parameter of
the furnace comprises a use of particular atmospheres in
25 various zones of the furnace, in particular of atmospheres
having controlled oxygen contents.
30
12. The process as claimed in one of claims 8 to
11, wherein the modification of an operating parameter of
the furnace comprises a use
supplying the burners of
of several types of fuels for
the furnace and producing
different atmospheres with a view to reduce the amount of
oxide scale.
13. The process as claimed in one of claims 8 to
12, wherein an operating parameter of the furnace comprises
35 a use of product heating curves.
14. The process as claimed in one of claims 8 to
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32
13, characterized in that it comprises an optimization of
the amount of metal lost in and outside of the furnace
during the product reheating process.