U.S. patent application number 13/143024 was filed with the patent office on 2011-11-03 for method for cooling a moving metal belt.
This patent application is currently assigned to FIVES STEIN. Invention is credited to Christian Gaillard, Stephane Mehrain.
Application Number | 20110266725 13/143024 |
Document ID | / |
Family ID | 40909999 |
Filed Date | 2011-11-03 |
United States Patent
Application |
20110266725 |
Kind Code |
A1 |
Mehrain; Stephane ; et
al. |
November 3, 2011 |
METHOD FOR COOLING A MOVING METAL BELT
Abstract
The present invention relates to a method for cooling a moving
metal belt (2) in a continuous processing line by spraying a gas, a
liquid, or a mixture consisting of gas and liquid onto the belt,
the processing line including a cooling section (1) followed by a
downstream section (4), the inlet (4a) of the downstream section
corresponding to the outlet (1b) of the cooling section, wherein
according to said method: the change in the temperature
cross-section of the belt between the inlet (4a) and the outlet
(4b) of the downstream section (4) is evaluated; the temperature
cross-section suitable for the inlet of the downstream section is
deduced, on the basis of a desired temperature cross-section at the
outlet of the downstream section (4), in order to obtain the
desired cross-section at the outlet; and the cooling capacity of
the cooling section (1) is adjusted according to the width of the
belt and over the length of the cooling section, while taking into
the account the temperature cross-section of the belt at the inlet
of the cooling section, so that the cooling makes it possible to
obtain the aforementioned temperature cross-section at the outlet
of the cooling section.
Inventors: |
Mehrain; Stephane; (Longpont
Sur Orge, FR) ; Gaillard; Christian; (Maisons-Alfort,
FR) |
Assignee: |
FIVES STEIN
RIS ORANGIS
FR
|
Family ID: |
40909999 |
Appl. No.: |
13/143024 |
Filed: |
January 7, 2010 |
PCT Filed: |
January 7, 2010 |
PCT NO: |
PCT/IB10/50039 |
371 Date: |
June 30, 2011 |
Current U.S.
Class: |
266/44 |
Current CPC
Class: |
C21D 9/46 20130101; C21D
11/005 20130101; C21D 9/48 20130101; C21D 9/573 20130101; C21D 9/56
20130101; C21D 9/5735 20130101 |
Class at
Publication: |
266/44 |
International
Class: |
C21D 1/667 20060101
C21D001/667 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 9, 2009 |
FR |
0900078 |
Claims
1. A method for cooling a moving metal strip in a continuous
processing line by spraying a gas, a liquid, or a mixture
consisting of gas and liquid onto the strip, the processing line
comprising a cooling section followed by a downstream section
having a thermal effect upon the strip, the inlet of the downstream
section corresponding to the outlet of the cooling section,
wherein: the change in the transverse temperature profile of the
strip between the inlet and the outlet of the downstream section is
determined in real time by means of a computer on the basis of
mathematical models, while taking into account the format of the
strip, the running speed of the strip, the transverse temperature
profile of the strip at the inlet of the downstream section, and
the development of the heat exchanges between the strip and its
environment in the downstream section, on the basis of a desired
transverse temperature profile at exit from the downstream section,
the transverse temperature profile at the inlet of the downstream
section is suitable for obtaining the desired exit profile, the
cooling capacity of the cooling section is regulated according to
the width of the strip and over the length of the cooling section
in real time by a control and operating system of the line, by
means of the computer, on the basis of mathematical models, while
taking into account the transverse temperature profile of the strip
at the inlet of the cooling section and the development of the heat
exchanges between the strip and its environment in the cooling
section, so that the cooling makes it possible to obtain the
aforementioned suitable transverse temperature profile at exit from
the cooling section.
2. The method as claimed in claim 1, wherein the adjustment of the
cooling capacity is obtained by splitting a cooling device into a
plurality of units along the width and along the length of the
cooling section.
3. The method as claimed in claim 2, wherein each unit is provided
with regulating members in order to vary its cooling capacity
independently from the other units.
4. The method as claimed in claim 3, wherein the operation of the
regulating members is carried out from the computer, in which is
installed an appropriate operating program for the cooling
units.
5. The method as claimed in claim 4, wherein the computer receives
data supplied by temperature sensors distributed in the cooling
section and by temperature sensors distributed in the downstream
section, and the computer, on the basis of these data, checks
whether the cooling is effected in the desired manner, and possibly
corrects the execution of the cooling according to the width of the
strip and according to its length in order to obtain the desired
profile.
Description
[0001] The present invention relates to improvements made to the
cooling sections of continuous processing lines for metal strips,
in particular annealing, galvanization or tinplate lines.
[0002] A continuous processing line for metal strips is made up of
a succession of heat treatment sections, in particular heating,
maintenance, cooling, ageing sections, etc.
[0003] The present invention relates to cooling sections of
continuous processing lines and more particularly to the rapid
cooling sections, whatever the cooling method used, for example
radiation, convection or any other cooling method.
[0004] The cooling of the metal strip can be obtained by blowing a
gas, for example air, but more generally a mixture of nitrogen and
hydrogen, onto the strip. The hydrogen content of the mixture is
generally at least equal to 5%, so as to limit the oxidation of the
strip. Higher hydrogen contents are frequently used to improve
cooling performances, by virtue of the gain in exchange coefficient
resulting from the physical properties of the hydrogen.
[0005] In order to obtain even greater cooling gradients for the
strip, the cooling can equally be obtained by spraying a liquid
onto the strip. This liquid is frequently water, which can be
pretreated, for example in order to extract dissolved oxygen or
mineral salts therefrom, and which can contain additives in order
to improve the heat exchange or limit the oxidation of the
strip.
[0006] The cooling of the strip can equally be obtained by spraying
a mixture consisting of gas and liquid onto the strip. The gas
which is used is generally nitrogen, but can equally be composed of
a mixture of nitrogen and hydrogen, or any other gas. The cooling
liquid is frequently water, possibly treated as previously
described.
[0007] The quality of the cooling has a substantial impact on the
mechanical properties of the strip and on its surface finish.
According to the starting and end cooling temperatures and the
cooling gradients, the cooling of a metal strip is generally
accompanied by metallurgical transformations with phase changes so
as to obtain the sought mechanical properties, for example in terms
mechanical resistance or drawability. The nature of the formed
phases, their proportion and their morphology depend on the
temperatures and the cooling gradients. Good temperature
homogeneity over the length of the strip along the cooling section
is thus crucial to ensuring that the obtained metallurgical
transformations are those which are sought.
[0008] The continuous processing lines have high strip running
speeds for the strip, for example from 100 to 800 m/min, the strip
circulating on transport rollers. The guidance of the moving strip
in the different sections of the line is crucial to avoiding
contact between the strip and the walls. Differences in length over
the width of the strip, with, for example, long or short edges
relative to the center of the strip, influence the quality of
guidance of the strip. It will be appreciated that a difference in
cooling intensity over the width of the strip leads to a difference
in temperature and hence a difference in contraction of the strip
over its width, which impacts on the guidance of the strip.
[0009] Following its exit from the cooling section, the strip
circulates in the downstream-situated sections, where the thermal
path of the strip continues. It can, for example, cross an ageing
section, with the latter being maintained at an appropriate
temperature for a period of several seconds to several minutes.
[0010] In the course of its passage into the section of the furnace
situated downstream of the cooling section, the strip will see its
average temperature develop with a temperature rise in the case of
a warming section, or a temperature drop in the case of a cooling
section. The average temperature of the strip will likewise be able
to be kept constant in respect of a maintenance section. According
to the nature, the geometry, the means used for the warming or
cooling and the method of control of the section situated
downstream of the cooling section, the transverse temperature
profile of the strip will be able to develop between the inlet and
outlet of this section by virtue of a different heat exchange over
the strip width. Thus, a strip which is perfectly homogeneous in
temperature at exit from the cooling section will be able to have
warmer or cooler edges than the center at the outlet of the
downstream chamber. It will be readily appreciated that the
temperature profile of the strip at the outlet of the section
situated downstream of the cooling section will equally be linked
to the temperature profile of the strip at exit from the cooling
section. It is hence possible to influence the temperature profile
of the strip at exit from the downstream section according to the
temperature profile of the strip at exit from the cooling
section.
[0011] It is evident that the control of the cooling over the strip
width, over the entire length of the cooling section, is critical
to obtaining homogeneous mechanical properties over the strip
width, to avoiding strip guidance defects and to anticipating the
development of the temperature profile of the strip in the
downstream-situated section. This control is particularly crucial
for wide and relatively thin strips.
[0012] The object of the invention is, above all, to improve the
control of the cooling over the strip width in order to meet these
requirements, so that the cooling curve at any point on the width
of the strip along the cooling section is that which is sought.
[0013] The invention thus relates to a method for cooling a moving
metal strip in a continuous processing line by spraying a gas, a
liquid, or a mixture consisting of gas and liquid onto the strip,
the processing line comprising a cooling section followed by a
downstream section having a thermal effect upon the strip, the
inlet of the downstream section corresponding to the outlet of the
cooling section.
[0014] The method of the invention is characterized in that: [0015]
the change in the transverse temperature profile of the strip
between the inlet and the outlet of the downstream section is
evaluated in real time by means of a computer on the basis of
mathematical models as a function of the format of the strip, the
running speed and the transverse temperature profile of the strip
at the inlet of the downstream section, [0016] from a desired
transverse temperature profile at exit from the downstream section
is deduced that transverse temperature profile at the inlet of the
downstream section which is suitable for obtaining the desired exit
profile, [0017] and the cooling capacity of the cooling section is
adjusted according to the width of the strip and over the length of
the cooling section in real time by a control and operating system
of the line, by means of the computer, on the basis of mathematical
models, while taking into account the transverse temperature
profile of the strip at the inlet of the cooling section and the
development of the heat exchanges between the strip and its
environment in the cooling section, so that the cooling makes it
possible to obtain the aforementioned suitable transverse
temperature profile at exit from the cooling section.
[0018] According to the invention, the cooling capacity is thus
adjusted, while taking into account, in advance, the future
development of the transverse temperature profile of the strip
during its stay in that section of the line situated downstream of
the cooling section.
[0019] The control of the temperature profile over the width of the
strip resulting from the adjustment of the cooling capacity over
the strip width is designed to allow the guidance of the strip on
the transport rollers to be improved by the obtention of long or
short edges relative to the center of the strip.
[0020] The adjustment of the cooling capacity can be obtained by
splitting the cooling device into a plurality of units along the
width and along the length of the cooling section. Each unit can be
provided with regulating members in order to vary its cooling
capacity independently from the other units.
[0021] The operation of the regulating members can be carried out
from a computer, in which is installed an appropriate control
program for the cooling units. Advantageously, the computer
receives data supplied by temperature sensors distributed in the
cooling section and by temperature sensors distributed in the
downstream section, and the computer, on the basis of these data,
checks whether the cooling is effected in the desired manner, and
possibly corrects the execution of the cooling according to the
width of the strip and according to its length in order to obtain
the desired profile.
[0022] Aside from the arrangements set out above, the invention
consists in a certain number of other arrangements which will be
discussed more explicitly below in connection with an illustrative
embodiment described with reference to the appended drawing, but
which is by no means restrictive. In this drawing:
[0023] FIG. 1 is a schematic vertical section of a cooling section
and of a downstream section of a continuous processing line for a
metal strip.
[0024] FIG. 2 is a horizontal section of the cooling section along
the line II-II of FIG. 1, and
[0025] FIG. 3 is a graph illustrating the variations in the
transverse temperature profile of the strip (y-axis) plotted
against the width of the strip (y-axis).
[0026] Referring to FIGS. 1 and 2 of the drawing, a cooling section
1 of a continuous processing line for a moving metal strip 2 can be
seen. According to the represented example, the cooling section 1
is vertical, but it could also be horizontal, or inclined relative
to the vertical. In the top portion of the section 1, the strip 2
passes over return rollers 3 so as to engage in a downstream
section 4 likewise shown vertical in the example, but which can be
arranged otherwise, especially horizontally. The width (FIG. 2) of
the strip 2 is perpendicular to the plane of FIG. 1.
[0027] The cooling of the strip 2 is carried out by spraying a gas,
a liquid, or a mixture consisting of gas and liquid, onto each of
the faces of the strip, with the aid of nozzles 5 distributed in
the walls of the section 1 which stand parallel to the strip 2 on
each side of this strip. The nozzles 5 are oriented in such a way
as to direct at least one jet of cooling fluid against the strip 2,
especially in a direction substantially at right angles to this
strip. The nozzles 5 are fed with cooling fluid through the pipes
6.
[0028] The inlet 4a of the downstream section corresponds to the
outlet 1b of the cooling section. The strip 2 has a transverse
temperature profile P (FIG. 3) which is dependent on the considered
zone of the strip 2. The profile P represents the variation in
temperature of a point of the strip according to its width, which
corresponds to a direction at right angles to the direction of
displacement of the strip.
[0029] According to the invention, the change in transverse
temperature profile between the inlet 4a and the outlet 4b of the
downstream section is evaluated as a function of the format of the
strip 2, in particular according to its width, its thickness and
its nature, and as a function of the transverse temperature profile
of the strip at the inlet 4a of the downstream section.
[0030] This change in transverse profile can be evaluated on the
basis of mathematical models by which the heat exchanges between
the strip 2 and the section 4 can be calculated, possibly
supplemented by prior measures.
[0031] Next, by a reverse step, on the basis of a desired
transverse temperature profile P4b (FIG. 3) at exit 4b from the
downstream section, the transverse temperature profile P4a, at the
inlet 4a of the downstream section, which is suitable for obtaining
the desired exit profile P4b, is deduced.
[0032] In the schematic example of FIG. 3, the desired exit profile
P4b is a homogeneous profile according to width, that is to say
that the temperature of the strip is constant from one edge to the
other. In this example, the downstream section 4 subjects the strip
to a warming which is more pronounced on the left-hand edge than at
the center and on the other edge. The profile P4a at the inlet of
the section, suitable for giving the profile P4b, will have an
upwardly convex shape on the left edge, corresponding to a lesser
strip temperature on the left edge.
[0033] On the one hand, the transverse profile P4a at the inlet of
the downstream section 4a, which is also the profile P1b at the
outlet 1b of the cooling section, is at hand, and, on the other
hand, the transverse temperature profile P1a at the inlet of the
cooling section is known. According to the example of FIG. 3, the
profile P1a is upwardly concave, corresponding to strip edges
warmer than the center. The cooling capacity of the cooling section
1 is then adjusted according to the width of the strip 2 and
according to the length of the cooling section, in order to obtain,
from the entry profile P1a, the exit profile P1b=P4a. The
transverse temperature profile P1a at the inlet is known with the
aid of temperature sensors distributed over the width of the strip,
at the inlet 1a.
[0034] The adjustment of the cooling capacity over the width of the
strip can be obtained by numerous known means.
[0035] Advantageously, this adjustment of the cooling capacity is
obtained by splitting a cooling device R into a plurality of units
Ryz along the width and along the length of the cooling section 1,
that is to say in the vertical direction according to the
considered example. The value y of Ryz can vary from 1 to m, m
being the number of units according to the width of the strip,
while the value z can vary from 1 to n, n being the number of units
according to the length of the cooling section 1.
[0036] Generally speaking, each unit Ryz is equipped with a member,
for example a regulator valve 7, by which the flow of the cooling
means, gas, liquid, or gas/liquid mixture can be varied. In the
case of a gas/liquid mixture, a regulator valve can be necessary in
respect of each fluid. Each unit is thus provided with the
equipment necessary to vary its cooling capacity independently from
the other units.
[0037] In the example illustrated in FIG. 1, each cooling unit Ryz
comprises two nozzles 5, having the same position according to
width, but vertically staggered according to length. The nozzles 5
of a same unit are fed in parallel from a same pipe 6, on which is
disposed a regulator valve 7 controlling the flow of gas or the
flow of the cooling liquid.
[0038] The operation of the regulating members, such as the valves
7, is carried out from a computer A, in which is installed an
appropriate operating program for the cooling units. The computer A
additionally receives data supplied by temperature sensors 8
distributed in the cooling section and by temperature sensors 9
distributed in the downstream section. On the basis of these data,
the computer A checks whether the cooling is effected in the
desired manner, and possibly corrects the execution of the cooling,
according to the width of the strip and according to its length, in
order to obtain the desired profile.
[0039] Where cooling is effected by a mixture consisting of a gas
and a liquid, each unit will be able to be equipped, for example,
with a flow control member solely in relation to the gas, the flow
of the liquid being constant, or with a flow control member solely
in relation to the liquid, the flow of the gas being constant, or
with two control members, by which the flow of gas and the flow of
the liquid can be varied. Each unit can equally be equipped with a
device G, by which the temperature of the gas, of the liquid, or of
the mixture consisting of gas and liquid can be varied, so as to
vary its cooling capacity. This variation of the temperature of the
cooling means will be able to be realized for a constant flow of
the cooling means, or combined with a variation of the flow of the
cooling means so as to increase the regulating flexibility of the
installation.
[0040] By way of example: [0041] if the section 4 situated
downstream of the cooling section 1 is a warming section which
leads to a higher temperature of one of the edges of the strip of
5.degree. C., for example the left edge, whereas a homogeneous
temperature at exit 4b from said section is sought, [0042] and if
the strip 2 enters into the cooling section 1 with perfect
homogeneity of temperature over its width,
[0043] then, according to the invention, the cooling parameters are
adjusted such that a greater cooling capacity on the considered
edge, the left edge in the example, leads to a supplementary
cooling of this latter of 5.degree. C. relative to the rest of the
width of the strip.
[0044] According to a variant of this example: [0045] if the strip
2 enters at present into the cooling section 1 with the considered
edge 10.degree. C. cooler than the rest of the strip,
[0046] then, according to the invention, the cooling parameters are
adjusted so that a weaker cooling capacity on the considered edge
leads to a lesser cooling of this latter of 10.degree. C. relative
to the rest of the strip width.
[0047] The program or programs installed in the computer A are
established with mathematical means, utilizing models based on the
physical laws of heat exchanges, and allow good simulation of the
temperature variations of a strip 2, when passing into a section of
a continuous line, according to the nature of said strip and its
thermal state. It is hence possible to predict the development of
the temperature profile of the strip along this section and
consequently to adjust the working parameters of each unit of the
cooling section.
[0048] Tests conducted at the time of the start-up of the
continuous line are likewise put to use to refine the thermal model
and increase the precision of the device, by improving the program
installed in the computer.
* * * * *