U.S. patent application number 14/758393 was filed with the patent office on 2015-12-10 for method, controller and tundish control system for a continuous casting process.
The applicant listed for this patent is ABB TECHNOLOGY LTD. Invention is credited to Jan-Erik Eriksson, Olof Sjoden.
Application Number | 20150352635 14/758393 |
Document ID | / |
Family ID | 47757576 |
Filed Date | 2015-12-10 |
United States Patent
Application |
20150352635 |
Kind Code |
A1 |
Eriksson; Jan-Erik ; et
al. |
December 10, 2015 |
Method, Controller And Tundish Control System For A Continuous
Casting Process
Abstract
A method of controlling the temperature of molten metal in a
tundish during a ladle tapping cycle in a continuous casting
process. The method comprises a) obtaining a measure of a
temperature of molten metal in the tundish; b) comparing the
measured temperature with a desired tundish melt temperature; c)
determining whether the measured temperature is lower than desired;
d) controlling the temperature of the molten metal in the tundish
by with a heating arrangement, and an electromagnetic stirrer which
stirs the molten metal in order to distribute heated molten metal
in the tundish such that the temperature of the molten metal
approaches the desired temperature.
Inventors: |
Eriksson; Jan-Erik;
(Vasteras, SE) ; Sjoden; Olof; (Nykoping,
SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ABB TECHNOLOGY LTD |
Zurich |
|
CH |
|
|
Family ID: |
47757576 |
Appl. No.: |
14/758393 |
Filed: |
February 19, 2013 |
PCT Filed: |
February 19, 2013 |
PCT NO: |
PCT/EP2013/053250 |
371 Date: |
June 29, 2015 |
Current U.S.
Class: |
75/382 ;
266/87 |
Current CPC
Class: |
B22D 11/16 20130101;
B22D 41/015 20130101; F27D 21/0014 20130101; B22D 41/01 20130101;
B22D 1/00 20130101; B22D 11/10 20130101 |
International
Class: |
B22D 41/01 20060101
B22D041/01; B22D 11/16 20060101 B22D011/16; B22D 1/00 20060101
B22D001/00; B22D 11/10 20060101 B22D011/10 |
Claims
1. A method of controlling the temperature of molten metal (M) in a
tundish during a ladle tapping cycle in a continuous casting
process, wherein the method comprises: a) obtaining a measure of a
temperature of molten metal (M) in the tundish, b) comparing the
obtained measure of temperature with a desired a desired tundish
melt temperature, c) determining whether the measure of temperature
is lower than the desired tundish melt temperature and in case the
measure of temperature is lower than the desired tundish melt
temperature, d) controlling the temperature of the molten metal (M)
in the tundish by means of a heating arrangement comprising a set
of one or more oxy-fuel burners which heats the molten metal (M) in
the tundish, and by means of an electromagnetic stirrer which stirs
the molten metal (M) in order to distribute heated molten metal (M)
in the tundish such that the temperature of the molten metal (M) in
the tundish approaches the desired tundish melt temperature.
2. The method as claimed in claim 1, wherein the step a) of
obtaining a measure of a temperature comprises estimating the
temperature of the molten metal based on a model of the continuous
casting process and on a ladle temperature of molten metal (M).
3. The method as claimed in claim 2, wherein the ladle temperature
is obtained from a control loop associated with control of molten
metal temperature in the ladle.
4. The method as claimed in claim 1, wherein the step a) of
obtaining a measure of a temperature comprises obtaining
measurement values of the temperature of molten metal (M) in the
tundish.
5. The method as claimed in claim 1, comprising repeating steps a)
to d) during the ladle tapping cycle.
6. The method as claimed in claim 1, comprising, prior to step b)
of comparing, obtaining the desired tundish melt temperature.
7. The method as claimed in claim 1, wherein the desired tundish
melt temperature is an optimal casting process temperature obtained
from casting experiments.
8. A computer program comprising computer executable components
which causes a controller to perform the steps recited in claim 1
when the computer-executable components are run on a processing
unit included in the controller.
9. A controller for controlling the temperature of molten metal (M)
in a tundish during a ladle tapping cycle in a continuous casting
process, wherein the controller comprises: a processing unit, an
I/O unit arranged to communicate with an electromagnetic stirrer
and a heating arrangement comprising a set of one or more
oxy-burners, and a memory comprising computer executable components
which when run on the processing unit causes the controller to
perform the method as claimed in claim 1.
10. A tundish control system comprising: a controller as claimed in
claim 9, a heating arrangement comprising an oxy-fuel burner, and
an electromagnetic stirrer.
Description
FIELD OF THE INVENTION
[0001] The present disclosure generally relates to metallurgy, and
in particular it relates to a method and controller for controlling
the temperature of molten metal in a continuous casting
process.
BACKGROUND OF THE INVENTION
[0002] In continuous casting of metallic material, such as steel,
solid material is smelted and treated in a furnace. The molten
metal obtained from the solid material is tapped or poured into
ladles. The molten metal is normally further treated in the ladles.
After ladle treatment, the molten metal is sequentially poured from
the ladles into a tundish which is a container from which the
molten metal is tapped into one or more moulds for casting of the
material. The period during which a ladle pours its molten metal
into a tundish is herein termed a ladle tapping cycle. The tundish
thus acts as a buffer which provides a continuous flow of molten
metal into the mould(s) also during ladle change.
[0003] The quality of the finished metallic material is dependent
of the temperature of the molten metal during the continuous
casting process. The optimal ladle treatment temperature of molten
metal is normally lower than the temperature of the molten metal
obtained from the furnace. In order to attain an optimal ladle
treatment temperature of molten metal, the temperature of the
molten metal in the ladle is typically reduced under controlled
conditions.
[0004] If there is a large ladle tonnage combined with a relatively
slow casting speed, the temperature of the molten metal in the
tundish gradually decreases as molten metal is tapped from the
ladle into the tundish. Moreover, the temperature in the molten
metal in the tundish is normally not evenly distributed because
molten metal flowing from the ladle is hotter than the molten metal
already in the tundish which has walls acting as cooling elements
lowering the temperature in the vicinity of the walls.
SUMMARY OF THE INVENTION
[0005] The inventors have realised that, by controlling the
temperature of the molten melt in the tundish, an optimal
temperature of the molten metal can be obtained also in the
tundish. Moreover, it has also been realised that it is not
sufficient to merely control a heating arrangement to heat molten
metal in the tundish to obtain a satisfying result.
[0006] In view of the above, a general object of the present
disclosure is to improve the quality of metallic material produced
in a continuous casting process. In particular, it would be
desirable to be able to provide solidified metallic material of
constant high quality.
[0007] Hence, according to a first aspect of the present disclosure
there is provided a method of controlling the temperature of molten
metal in a tundish during a ladle tapping cycle in a continuous
casting process, wherein the method comprises: [0008] a) obtaining
a measure of a temperature of molten metal in the tundish, [0009]
b) comparing the obtained measure of temperature with a desired
tundish melt temperature, [0010] c) determining whether the measure
of temperature is lower than the desired tundish melt temperature,
and in case the measure of temperature is lower than the desired
tundish melt temperature, [0011] d) controlling the temperature of
the molten metal in the tundish by means of a heating arrangement
which heats the molten metal in the tundish, and by means of an
electromagnetic stirrer which stirs the molten metal in order to
distribute heated molten metal in the tundish such that the
temperature of the molten metal in the tundish approaches the
desired tundish melt temperature.
[0012] An effect which may be obtainable thereby is that the cast
material, i.e. the metallic material produced in the continuous
casting process, can be produced at a constantly higher quality
than has previously been possible. In particular, by controlling
the temperature of the molten metal in the tundish, the temperature
of the molten metal can be kept at a beneficial level throughout
the casting process and by the provision of stirring the heated
molten metal is evenly distributed in the tundish such that a
homogenous or essentially homogenous melt temperature can be
obtained in the tundish. The desired tundish melt temperature is an
optimal tundish melt or molten metal temperature which is known
from for example casting experiments, empirical tests or previous
casting experience.
[0013] According to one embodiment step a) of obtaining a measure
of a temperature comprises estimating the temperature of the molten
metal based on a model of the continuous casting process and on a
ladle temperature of molten metal. The ladle temperature is the
temperature of the molten metal when it is tapped from the ladle to
the tundish.
[0014] According to one embodiment the ladle temperature is
obtained from a control loop associated with control of molten
metal temperature in the ladle.
[0015] According to one embodiment step a) of obtaining a measure
of a temperature comprises obtaining measurement values of the
temperature of molten metal in the tundish. By stirring the molten
metal in the tundish and thereby obtaining a homogeneous
temperature, measurements of the temperature of the molten metal
become more accurate. Thus, the stirring provides a homogenous melt
temperature resulting in a higher quality final product as well as
more accurate melt temperature measurements which facilitates the
control of the melt temperature in the tundish.
[0016] The measure of the molten metal temperature in the tundish
can be obtained either by estimation or via direct measurements,
for example by means of consumable thermocouples. As an
alternative, a combination of melt temperature estimation and
direct measurement is also contemplated.
[0017] One embodiment comprises repeating steps a) to d) during the
ladle tapping cycle.
[0018] One embodiment comprises, prior to step b) of comparing,
obtaining the desired tundish melt temperature.
[0019] The desired tundish melt temperature may be an optimal
casting process temperature obtained from casting experiments.
Thus, data obtained from previously performed casting experiments,
empirical tests or casting experience may be utilised to set the
desired tundish melt temperature.
[0020] According to one embodiment the step of obtaining the ladle
temperature involves obtaining the ladle temperature from a control
loop associated with control of molten metal temperature in the
ladle.
[0021] According to one embodiment the desired tundish melt
temperature is an optimal casting process temperature in the
tundish.
[0022] According to a second aspect of the present disclosure there
is provided a computer program comprising computer executable
components which causes a controller to perform the method
according to the first aspect when the computer-executable
components are run on a processing unit included in the
controller.
[0023] According to a third aspect of the present disclosure there
is provided a controller for controlling the temperature of molten
metal in a tundish during a ladle tapping cycle in a continuous
casting process, wherein the controller comprises: a processing
unit, and a memory comprising computer executable components which
when run on the processing unit causes the controller to perform
the method of the first aspect.
[0024] The controller may advantageously be utilised in a tundish
control system. Thus, according to a fourth aspect of the present
disclosure there is provided a tundish control system comprising: a
controller according to the third aspect, a heating arrangement,
and an electromagnetic stirrer. The controller may thus control the
heating arrangement and the stirrer such that the molten metal
obtains the desired tundish melt temperature in the tundish.
[0025] According to one embodiment the heating arrangement
comprises an oxy-fuel burner.
[0026] Generally, all terms used in the claims are to be
interpreted according to their ordinary meaning in the technical
field, unless explicitly defined otherwise herein. All references
to "a/an/the element, apparatus, component, means, etc. are to be
interpreted openly as referring to at least one instance of the
element, apparatus, component, means, etc., unless explicitly
stated otherwise.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The specific embodiments of the inventive concept will now
be described, by way of example, with reference to the accompanying
drawings, in which:
[0028] FIG. 1 depicts a longitudinal section of a part of a
continuous caster;
[0029] FIG. 2a is an elevated view of a tundish and electromagnetic
stirrers;
[0030] FIG. 2b is a longitudinal section of a tundish and a heating
arrangement;
[0031] FIG. 3 is a schematic diagram of a controller for
controlling the temperature of molten metal in a tundish during a
ladle tapping cycle in a continuous casting process;
[0032] FIG. 4 is a schematic view of a tundish control system;
[0033] FIGS. 5a-b illustrate molten metal temperature control in a
tundish; and
[0034] FIG. 6 is a flowchart of a method of controlling the
temperature of molten metal in a tundish during a ladle tapping
cycle in a continuous casting process.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The inventive concept will now be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplifying embodiments are shown. The inventive concept may,
however, be embodied in many different forms and should not be
construed as limited to the embodiments set forth herein; rather,
these embodiments are provided by way of example, so that this
disclosure will be thorough and complete, and will fully convey the
scope of the inventive concept to those skilled in the art. Like
numbers refer to like elements throughout the description.
[0036] FIG. 1 depicts a longitudinal section of an example of
continuous caster 1. Continuous caster 1 comprises a ladle 3, a
tundish 5, and moulds 7. The ladle 3 has a pipe 3a through which
molten metal M may be tapped into the tundish 5. The exemplified
tundish 5 has a lid 5a with an opening 5c through which the pipe 3a
of the ladle 3 may discharge molten metal M. The tundish 3 further
comprises nozzles 5b, e.g. submerged entry nozzles (SEN), through
which molten metal M in the tundish 3 may be discharged to
respective moulds 7. The flow direction of the continuous casting
process is indicated by arrows A.
[0037] Ladle 3 is arranged in a fixed position during a ladle
tapping cycle. Upon a ladle change the ladle 3 may be moved in one
of the directions B, wherein ladle 3 is exchanged with another
ladle filled with molten metal to be discharged into the tundish 5.
Molten metal M can thereby continuously be tapped or discharged
from the tundish 5 into the moulds 7.
[0038] It should be noted that the number of tundish nozzles,
whether the tundish has a lid or not and the number of openings in
the lid is not important for the purpose of the method presented
herein.
[0039] A method and controller for controlling the molten metal
temperature in a tundish, such as tundish 3, during a ladle tapping
cycle will now be described with reference to FIGS. 2-6.
[0040] FIG. 2a schematically shows an elevated view of a tundish 5
and electromagnetic stirrers 9. The electromagnetic stirrers 9 may
be moved towards and from the tundish side walls as shown by the
arrows. It is envisaged that according to a variation hereof, at
least one of the electromagnetic stirrers could be fixed to a
tundish side wall. It is also contemplated that only one
electromagnetic stirrer could be used, either attached to a tundish
side wall or moveable towards and from the tundish side wall. The
electromagnetic stirrer(s) 9 is/are arranged to stir molten metal M
in the tundish 5 as will be elaborated herebelow.
[0041] FIG. 2b is a longitudinal section of a tundish 5 and a
portion of a heating arrangement 11 arranged to heat molten metal
in the tundish 5. The heating arrangement 11 can for example
comprise a set of one or more oxy-fuel burners to provide heat.
According to one variation, the heating arrangement 11 is arranged
to indirectly heat molten metal in the tundish 5, i.e. heat is
provided to a heat transfer interface such as the lid 5a as shown
in FIG. 2b, or to a side wall of the tundish. The heating
arrangement 11 may for example be arranged on the lid. The heating
arrangement 11 may thus for example be arranged on the inside of
the lid or on the outside of the lid. Alternatively, the heating
arrangement may be an independent structure, i.e. an arrangement
detached from the tundish lid or tundish side wall. According to
one variation, the heating arrangement may be arranged to heat the
molten metal directly in the tundish, i.e. by providing heat
directly to the molten metal without utilisation of a heat transfer
interface.
[0042] It may be advantageous to heat the molten metal via a heat
transfer interface instead of direct heating of the molten metal.
If for example the heating arrangement comprises oxy-fuel burners,
heating of a heat transfer interface instead of direct heating of
the molten metal eliminates oxide contamination of molten metal in
the tundish.
[0043] FIG. 3 shows a schematic block diagram of a controller 13
for controlling the temperature of molten metal in a tundish during
a ladle tapping cycle. The controller 13, which for example may be
a programmable logic controller (PLC), comprises an input/output
(I/O) unit 13a, a processing unit 13b and a memory 13c. The I/O
unit 13a is arranged to communicate with an electromagnetic stirrer
9 and a heating arrangement 11. According to one variation the I/O
unit 13a may be arranged to receive a measure of the temperature of
molten metal in a tundish in the form of process variable values
obtained by one or more heat sensing means. The processing unit 13b
is arranged to communicate with the I/O unit 13a and with the
memory 13b. The memory 13c comprises computer-executable components
which can be loaded into the processing unit 13b. When the
computer-executable components are run on the processing unit 13b
the controller 13 controls the temperature of molten metal in a
tundish according to the method presented herein.
[0044] FIG. 4 shows a tundish control system 15 comprising a
controller 13, a heating arrangement 11 and an electromagnetic
stirrer 9. According to the example shown in FIG. 4, the heating
arrangement 11 and the electromagnetic stirrer 9 are in position to
influence the temperature of molten metal M in tundish 5 via the
controller 13.
[0045] The operation of the tundish control system 15 will now be
described with reference being made to FIGS. 5a-c and FIG. 6.
[0046] In FIG. 5a molten metal M having a ladle temperature T1 is
discharged from the ladle 3 into the tundish 5. In a step a) the
processing unit 13b of the controller 13 obtains a measure of a
temperature T2 of molten metal M in the tundish 5. The obtained
measure of temperature may for example be a measure of an average
temperature of the molten metal M in the tundish 5. The measure of
the temperature T2 can according to one variation of the method be
obtained by estimating the temperature T2 of the molten metal M in
the tundish 5. The estimation can for example be based on a model
of the continuous casting process and on the ladle temperature T1
of molten metal M. By means of the model, approximate temperature
values of molten metal at various points in time of a ladle tipping
cycle may be obtained with the ladle temperature T1 as initial
condition. The ladle temperature can for example be obtained from a
control loop associated with control of molten metal temperature in
the ladle 3. Alternatively, step a) may comprise obtaining
measurement values of the temperature T2 of molten metal in the
tundish. Temperature measurements may in this case for example be
obtained from several locations in the molten metal to obtain a
mean molten metal temperature in the tundish. After stirring of the
molten metal, the temperature of molten metal in the tundish is
more evenly distributed, facilitating temperature measurements of
the molten metal.
[0047] In a step b) the obtained measure of temperature T2 is
compared with a desired tundish melt temperature by the processing
unit 13b. As earlier mentioned the desired tundish melt temperature
can be determined in casting experiments, empirical tests or
through extensive casting experience. The desired tundish melt
temperature depends, among other things, on the desired quality of
the casted product. In a step c) it is determined whether the
measure of temperature T2 is lower than the desired tundish melt
temperature.
[0048] According to one variation, the desired tundish melt
temperature is obtained prior to step b). The desired tundish melt
temperature may be higher than the ladle temperature, essentially
equal to the ladle temperature, or lower than the ladle
temperature, depending on the desired final product quality. If the
desired tundish temperature is lower than the ladle temperature,
then stirring may be performed without utilising the heating
arrangement until the desired tundish melt temperature has been
obtained. At that time, the heating arrangement may be controlled
to heat the molten metal in the tundish to obtain the desired
tundish melt temperature.
[0049] If the measure of temperature T2 is lower than the desired
tundish melt temperature the controller 13 controls the temperature
of the molten metal M in the tundish 5 in a step d) by means of a
heating arrangement 11 which heats the molten metal in the tundish,
and by means of electromagnetic stirrer 9 which stirs the molten
metal in the tundish 5. As mentioned earlier, the heating
arrangement may for example comprise oxy-fuel burners. This is
depicted in FIG. 5b where oxy-fuel burners provide heat via flames
F.
[0050] By stirring, the heated molten metal is distributed in the
tundish 5 such that the temperature of the molten metal M in the
tundish 5 approaches the desired tundish melt temperature T3, as
shown in FIG. 5b.
[0051] The present disclosure hence provides a method, a controller
and tundish control system adapted for molten metal temperature
control in a tundish in a continuous casting process for the
production of for example billets, blooms or slabs of steel,
aluminium or copper.
[0052] The inventive concept has mainly been described above with
reference to a few examples. However, as is readily appreciated by
a person skilled in the art, other embodiments than the ones
disclosed above are equally possible within the scope of the
inventive concept, as defined by the appended claims.
* * * * *