CA1341247C - Control method of cooling steel - Google Patents
Control method of cooling steelInfo
- Publication number
- CA1341247C CA1341247C CA000603379A CA603379A CA1341247C CA 1341247 C CA1341247 C CA 1341247C CA 000603379 A CA000603379 A CA 000603379A CA 603379 A CA603379 A CA 603379A CA 1341247 C CA1341247 C CA 1341247C
- Authority
- CA
- Canada
- Prior art keywords
- cooling
- transformation
- steel
- temperature
- rate
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21B—ROLLING OF METAL
- B21B37/00—Control devices or methods specially adapted for metal-rolling mills or the work produced thereby
- B21B37/74—Temperature control, e.g. by cooling or heating the rolls or the product
- B21B37/76—Cooling control on the run-out table
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D11/00—Process control or regulation for heat treatments
- C21D11/005—Process control or regulation for heat treatments for cooling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
- C21D9/54—Furnaces for treating strips or wire
- C21D9/56—Continuous furnaces for strip or wire
- C21D9/573—Continuous furnaces for strip or wire with cooling
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Control Of Heat Treatment Processes (AREA)
- Control Of Metal Rolling (AREA)
Abstract
In cooling a steel through cooling zones, the temperature of the steel is estimated by taking the temporal development of the steel due to the transformation of the same (the change in the amount of heat production of the steel produced upon the transformation of the same in response to the temporal change) into consideration to determine the quantity of a coolant, for thereby controlling the steel temperature to a target one at a predetermined position on a line or at a predetermined time.
Description
BACKGROUND OF THE INVENTION
(A) Field of the Invention The present invention relates to a control method of cooling a steel, and more specifically to that suitable for use in accurately controlling a hot rolled steel to a predetermined target temperature.
l0 (B) Description of the Prior Art A hot rolling system forms in general a steel coil by winding a steel sheet being a hot drawn steel after rolling the sheet, with a coiler. To wind up such a steel sheet, the steel sheet should be cooled to a temperature suitable for the winding. In the hot rolling system, the steel sheet is cooled by a cooling system.
The hot rolling system is constructed such that a finishing rolling machine rolls a steel sheet, which sheet 2 0 is then forcedly sent on a run-out table in a predetermined position and wound up by a coiler. There is disposed a cooling system along the run-out table which is to cool the steel sheet to a temperature suitable for the winding. The cooling system includes on the side of an inlet thereof an inlet thermometer for measuring the temperature of the steel sheet to be cooled, and on the side of an outlet thereof an outlet thermometer for measuring the temperature of the ~3~,~ 2~) steel sheet after cooled.
The cooling system is separated into two and disposed across vertically the run-out table. Each the separated portion includes a water cooling section for cooling the steel sheet by pouring water thereon and an air cooling section for cooling the same with air. The air cooling section has the same structure as the water cooling section when the latter stops the pouring of water on the steel sheet. The water cooling section and the air cooling l0 section disposed on the upper and lower sides of the cooling system are divided into cooling banks. Each bank is controllable in its cooling capability to cool the steel sheet.
To control the cooling of the steel sheet by the cooling system, the cooling system is divided into a plurality of cooling zones each including the cooling banks of one or more along the run-out table, the cooling capability of each cooling zone being controlled by controlling the amount of supply of a cooling medium (cooling water) from each bank to the steel sheet in conformity with the travelling of the steel sheet.
It is essential upon controlling the cooling capability of the cooling system as described above to estimate the amount of the cooling for the steel sheet, i.e., the amount of a change in the temperature of the same, in each cooling zone. For this, there have hitherto been proposed varieties of techniques to estimate the temperature of the steel sheet under cooling and execute the cooling control with high accuracy. A technique is known among those techniques described above, wherein learning on heat transfer coefficients and heat emission rates through and from the upper and lower surfaces of the steel sheet in running is determined by means of a Karman filter.
However, steel materials produce some heat in general in their transformation from y to a iron, for example form austenite to martensite. So, by the just-l0 mentioned technique wherein cooling capability of a cooling system is learned to estimate the temperature of the steel sheet for controlling the cooling, a problem causes that it is prevented from controlling the temperature of the steel sheet in due consideration of the heat production caused by the transformation of the steel, resulting in the reduced accurary of the cooling control.
On the contrary, to consider the heat production caused by the transformation of a steel material, technique for controlling the cooling in consideration of transformation start timing and transformation time is disclosed in reference on "Temperature Control in Winding of Hot Drawn High-Carbon Steel" presented at the Sectional Meeting on the filth Hot Strip held at 1987, and other publications and documents.
In this technique a temperature development of the transformation of a steel material is ignored and the amount of heat production in the transformation remains unchanged X341 2~7 without depending on the lapse of time from the initiation of the transformation, and that the total amount of the heat production in the transformation varies in proportion to the lapse of time from the initiation of the transformation. In other words, it is considered in this technique that an amount of the heat production in the transformation changes stepwise from the transformation initiation.
However, it should actually be considered that the rate W of the transformation of a steel material indicative l0 of the temperal development of the transformation of the same under cowling changes by a predetermined curve and the amount of the heat production changes in proportion to the gradient (aw/aT) of the rate W with respect to time T. For example, when the rate W of the transformation changes in a certain way, the gradient (aW/aT) of the rate W changes in a certain way. Hereby, the actual amount of the heat production in the transformation changes in a certain way.
In contrast thereto, the conventional technique just-mentioned above to control the cooling ignores the temporal development of the transformation of a steel. so, estimation accuracy depends on accuracy of pre-measured data, and a measuring error directly causes error in cooling control. Then, it has a drawback of the accuracy of temper-ature estimation being lowered followed by the cooling control with insufficient accuracy.
(A) Field of the Invention The present invention relates to a control method of cooling a steel, and more specifically to that suitable for use in accurately controlling a hot rolled steel to a predetermined target temperature.
l0 (B) Description of the Prior Art A hot rolling system forms in general a steel coil by winding a steel sheet being a hot drawn steel after rolling the sheet, with a coiler. To wind up such a steel sheet, the steel sheet should be cooled to a temperature suitable for the winding. In the hot rolling system, the steel sheet is cooled by a cooling system.
The hot rolling system is constructed such that a finishing rolling machine rolls a steel sheet, which sheet 2 0 is then forcedly sent on a run-out table in a predetermined position and wound up by a coiler. There is disposed a cooling system along the run-out table which is to cool the steel sheet to a temperature suitable for the winding. The cooling system includes on the side of an inlet thereof an inlet thermometer for measuring the temperature of the steel sheet to be cooled, and on the side of an outlet thereof an outlet thermometer for measuring the temperature of the ~3~,~ 2~) steel sheet after cooled.
The cooling system is separated into two and disposed across vertically the run-out table. Each the separated portion includes a water cooling section for cooling the steel sheet by pouring water thereon and an air cooling section for cooling the same with air. The air cooling section has the same structure as the water cooling section when the latter stops the pouring of water on the steel sheet. The water cooling section and the air cooling l0 section disposed on the upper and lower sides of the cooling system are divided into cooling banks. Each bank is controllable in its cooling capability to cool the steel sheet.
To control the cooling of the steel sheet by the cooling system, the cooling system is divided into a plurality of cooling zones each including the cooling banks of one or more along the run-out table, the cooling capability of each cooling zone being controlled by controlling the amount of supply of a cooling medium (cooling water) from each bank to the steel sheet in conformity with the travelling of the steel sheet.
It is essential upon controlling the cooling capability of the cooling system as described above to estimate the amount of the cooling for the steel sheet, i.e., the amount of a change in the temperature of the same, in each cooling zone. For this, there have hitherto been proposed varieties of techniques to estimate the temperature of the steel sheet under cooling and execute the cooling control with high accuracy. A technique is known among those techniques described above, wherein learning on heat transfer coefficients and heat emission rates through and from the upper and lower surfaces of the steel sheet in running is determined by means of a Karman filter.
However, steel materials produce some heat in general in their transformation from y to a iron, for example form austenite to martensite. So, by the just-l0 mentioned technique wherein cooling capability of a cooling system is learned to estimate the temperature of the steel sheet for controlling the cooling, a problem causes that it is prevented from controlling the temperature of the steel sheet in due consideration of the heat production caused by the transformation of the steel, resulting in the reduced accurary of the cooling control.
On the contrary, to consider the heat production caused by the transformation of a steel material, technique for controlling the cooling in consideration of transformation start timing and transformation time is disclosed in reference on "Temperature Control in Winding of Hot Drawn High-Carbon Steel" presented at the Sectional Meeting on the filth Hot Strip held at 1987, and other publications and documents.
In this technique a temperature development of the transformation of a steel material is ignored and the amount of heat production in the transformation remains unchanged X341 2~7 without depending on the lapse of time from the initiation of the transformation, and that the total amount of the heat production in the transformation varies in proportion to the lapse of time from the initiation of the transformation. In other words, it is considered in this technique that an amount of the heat production in the transformation changes stepwise from the transformation initiation.
However, it should actually be considered that the rate W of the transformation of a steel material indicative l0 of the temperal development of the transformation of the same under cowling changes by a predetermined curve and the amount of the heat production changes in proportion to the gradient (aw/aT) of the rate W with respect to time T. For example, when the rate W of the transformation changes in a certain way, the gradient (aW/aT) of the rate W changes in a certain way. Hereby, the actual amount of the heat production in the transformation changes in a certain way.
In contrast thereto, the conventional technique just-mentioned above to control the cooling ignores the temporal development of the transformation of a steel. so, estimation accuracy depends on accuracy of pre-measured data, and a measuring error directly causes error in cooling control. Then, it has a drawback of the accuracy of temper-ature estimation being lowered followed by the cooling control with insufficient accuracy.
SUMMARY OF THE INVENTION
In view of the drawbacks of the conventional techniques, it is an ob.iect of the present invention to provide a control method of cooling a steel capable of accurate cooling control without causing erroneous estimation of steel temperature by determining the amount of cooling on the basis of steel temperature estimated taking the temporal development of the steel transformation upon cooling into consideration.
To achieve the above ob,iect, a control method of cooling a steel according to the present invention for controlling the temperature of the steel at a predetermined position on a line or at a predetermined time to a desired target temperature comprising: estimating the temperature of the steel taking into consideration the temporal development of transformation of the steel, and determining the amount of cooling on the 1341 2~T-_ basis of the estimated temperature of the steel, the estimation of the steel temperature being performed by correcting steel temperature estimated on the basis of the time of cooling the steel and on the cooling capability of a cooling system in response to the temporal development of the transformation of the steel caused by the cooling.
Preferably, the temporal development of the transformation of the steel is considered for a change in the amount of the heat production upon the transformation of the steel depending on the change in the rate of the transformation of the steel.
More particularly the present invention is directed to a method of cooling a steel in a cooling system by controlled cooling of the steel to a target temperature, the method comprising the steps of:
- determining the temporal development of the steel by calculating the rate W of a phase transformation of the steel or by detecting said rate W by using a transformation rate sensor, and thereafter;
- calculating the heat produced during said transformation;
- estimating the temperature change of the steel for a time period based on cooling time of the steel and cooling capability of the cooling system;
- correcting error in the estimated temperature change by using the calculated heat produced during transformation;
- calculating a cooling bank pattern from parameters including the target temperature, the determined heat produced during transformation, and the corrected temperature change; and I
13 ~r 1 2 ~r 7 - determining a target temperature pattern on the basis of the cooling bank pattern and controlling the cooling system to cool the steel to a target temperature based upon the calculated cooling bank pattern.
Furthermore, in accordance with a preferred embodiment of the present invention, the rate W of the transformation is evaluated by the following formula as a function of the cooling time t:
W = 1 - exp jA ~ (t/B) C~
where A is a parameter for calculating the rate of the transformation, which is defined by the component, temperature, thickness, and geometrical cooling pattern of each steel used. In fact, parameter A is a tuning constant to fix the slope of the exponent curve so that actual values coincide with theoretical values.
B is a cooling time until center of transformation.
Parameter B corresponds to a time from outlet of finishing mill until the transformation rate reachs a predetermined value (50~ for example).
C is a gradient of the transformation curve. This parameter is a power which is theoretically determined from growth rate of metallic structure in view of metallography.
6a I
These parameters are determined by statistically processing results of experiments using actual steel.
Furthermore, preferably, the rate of the transformation is detected by using a transformation rate sensor.
Furthermore, in accordance with yet another preferred embodiment of the present invention, the rate of the transformation is established by learning an output of a transformation rate sensor.
Furthermore, in accordance with yet another preferred embodiment of the present invention, the cooling capability of the cooling system is established by learning the results of the cooling, the speed of carrying the steel and teh detected temperature.
Furthermore, in accordance with yet another preferred embodiment of the present invention, the cooling control is conducted by changing the amount of cooling water of each cooling bank and/or number of working banks according to the amounht of cooling.
Furthermore, in accordance with yet another preferred embodiment of the present invention, the cooling control is conducted by combining a water cooling and an air cooling according to the combination of temperature curves which are based on inlet temperature and outlet te~perature, respectively, the number of water poured banks are changed at the cooling zone where both cooling curves intersect with each other, and cooling is conducted according to a cooling curve which combines both cooling curves.
According to the present invention any erroneous estimation of the steel temperature with respect to an actual steel temperature in cooling can greatly be reduced, assuring accurate control of the amount of cooling followed 13~~ 24T
by the realization of cooling which provides a desired change of the temperature. This establishes the manufac-ture of a steel of stable quality with high productivity.
Additionally, when the temporal development of the transformation of the steel is considered for a change in the amount of heat produced upon the transformation of the steel depending on the change in the rate of the transformation of the steel, the temporal development of the transformation to be expressed in terms of an objective to numerical value, say the amount of heat production of hte steel by the transformation thereby facilitating the estimation of the steel temperature.
According to the present invention, any error of the estimated temperature with respect to actual steel temperature can greatly be reduced, resulting in highly accurate cooling of the steel. The present invention thus assures excellent effects such as manufacture of a steel of a stable quality with satisfactory productivity.
The exact nature of this invention, as well as other object and advantages thereof, will be readily apparent from r. ~:.:
l3~if 2~) consideration of the following specification relating to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof and wherein:
Fig. 1 is a block diagram partly including a cross sectional view, illustrating the whole arrangement of a cooling apparatus associataed with a first embodiment of the present invention:
Fig. 2 is a diagram illustrating an example of a cooling bank output pattern executed in a cooling system associated with the first embodiment:
Fig. 3 is a flow chart illustrating an example of a procedure of determining the cooling bank output pattern:
Fig. 4 is a block diagram partly including a cross sectional view, illustrating the whole arrangement of a second embodiment of the present invention:
Fig. 5 is a cross sectional view illustrating an example of a conventional cooling apparatus: and Fig. 6 is diagrams illustrating an example of a relationship among the conventionally considered amount of heat production caused by transformation, the conventionally considered rate of the transformation, the actual amount of heat production caused by transformation, and the actual change in the rate of the transformation.
[Embodiments]
In what follows, embodiments of the present invention will be described in detail with reference to the accompanying _ g _ 1341 2~7 drawings.
The first embodiment is a control apparatus wherein the control method of the present invention is executed to cool a hot drawn steel with use of a cooling system R in a cooling S apparatus located on a hot drawing line as illustrated in Fig.
1. The cooling system R is of the same construction as that shown in Fig. 5, wherein the steel sheet S rolled through the finishing rolling machine 1 is succesively wound up by the coiler 6 through the cooling system R. The finishing rolling machine 1 disposed on the inlet side of the cooling system R
includes an inlet speed detector 10 for detecting the carrying speed of the steel sheet S carried after rolled by the finishing rolling machine 1. In addtion, the coiler 6 disposed on the outlet side of the cooling system R includes an outlet speed detector 12 for detecting the wind-up speed of the steel sheet S. There are further provided inlet and outlet thermometers 2, 5 on the inlet and outlet sides of the cooling system R. Here, the like symbols shall be applied to the like configurations and operations as those in the conventional cooling system illustrated in Fig. 5, and detailed description is omitted..
The cooling system R, which includes a predetermined number of cooling zones, each zone having at least one cooling bank. The pouring amount of coolant (for example, water) from the cooling bank is controlled to control the cooling of the steel sheet S passing through each cooling zone.
Here, the inlet thermometer 2, inlet speed detector 10 C
and outlet speed detector 12 shown in Fig. 1 transmit respective detection signals to a cooling bank output pattern determining unit 14. The cooling bank output pattern determining unit 14 determines by computation a pattern to control the cooling capability of each cooling bank according to a cooling time t (hereinafter, referred to as a cooling bank pattern) for obtaining the desired temperature decrease of the steel sheet S in response to the cooling time t based upon the inputted inlet side temperature, the carrying speed of the steel sheet S, the wind-up speed, a preset target termperature of the steel sheet S and sheet thickness, etc..
The cooling bank pattern determined as described above is inputted into a cooling bank switching input/output unit 16.
The cooling bank switching input/output unit 16 controls the cooling capability of each cooling bank in response to the inputted cooling bank pattern.
Cooling results of pouring water by each bank of the cooling system R controlled by the bank switching input/output unit 16 are fed into a learning control unit 18. The learning control unit 18 receives detection signals from the inlet speed detector 10, the output speed detector 12, the inlet thermometer 2, and the outlet thermometer 5, and learns the - cooling capability of the cooling system R on the basis of the inputted aforesaid cooling results and the detection signals.
In succession, operation of the first embodiment will be described.
In the first embodiment, the change in the temperature of the steel sheet S after the lapse of predetermined time is estimated on the basis of the cooling time of the steel sheet S and of the cooling capability of the cooling system R. At the same time, the amount of heat production of the steel sheet S, for example, due to the transformation of the same is calculated in the response to the temporal development of the transformation caused by the cooling of the steel sheet S. Then, the error of the estimated change in the temperature of the steel sheet S is corrected by the to calculated amount of heat production of the steel sheet s due to the transformation of the same. Then the cooling bank pattern of the cooling system R is determined for cooling control so as to provide the corrected amount of the change in the temperature of the steel sheet S.
It will first be described how the temporal development of the transformation of the steel sheet S is obtained.
The rate W of the transformation of the steel sheet S under cooling can be calculated from the following 2o equation (1) as a function of the cooling time t.
W = 1 - exp [A~(t/B)~] ... (1) Here, A, B, and C are parameters determined by the component, temperature, thickness, and cooling pattern of each steel sheet S. More specifically, A is a parameter for calculating the rate of the transformation, which is defined by the component, temperature, thickness, and geometrical cooling pattern of each steel used.
B is a cooling time until center of transformation (when the transformation rate reach 50~).
C is a gradient of the transformation curve.
These parameters are determined by statistically processing results of experiments using actual steel.
The accuracy of estimating the rate W of the C
transformation can be increased by correcting the coeffi-cients for learning according to the learning results based on signals from a plurality of sensors for detecting the transformation rate, disposed in the cooling system.
The transformation rate sensor comprises by a combination of an exiting coil and magnetic detecting element, for example, and the transformation rate is detected by measuring phase transformation through a change in magnetic permeability. Such a sensor is disclosed in Canadian Patent 1,260,064.
It is possible to know the temporal development of the transformation of the steel sheet S with respect to time by the equation (1). In addition, the means to know the temporal development of the transformation of the steel sheet S is not limited to the one which utilizes the relationship of the equation (1). Instead, the transformation rate sensor to directly detect the rate of the transformation can be used.
On the assumption that in the cooling system R
including the cooling zones of the predetermined number, the cooling time from the inlet side to the ith cooling zone is ti, the amount of the change in the rate of the transformation ~ Wi - (Wi - Wi-1) in the ith cooling zone can be calculated on the basis of the cooling time ti ~ (ti - ti-1) in the ith cooling zone and the equation (1).
The amount of heat production QTi of the steel sheet S due to the transformation in the ith cooling zone when the amount of the change in the rate of the transformation D Wi, is given by the following equation (2).
QTi - H * OWi...(2) Here, H is latent heat of the steel sheet S upon the transformation (a physical quantity which can be determined from the component of the steel sheet S, the kind of the same, and the temperature of the same).
Therefore, the amount of heat production QT upon the transformation in each cooling zone when the steel sheet S is cooled from the inlet temperature FDT (Finished Derivery Temperature) to the target temperature CT (Cooling Temperature) is calculated by using the equation (2). Then the temperature change of the steel sheet S estimated from the cooling time of the steel sheet S and the capability of the cooling system R is corrected by the amount of heat production QTi upon the transformation so calculated. In consequence, the accurate temperature change of the steel sheet S as the sheet passes through each cooling zone can be estimated.
To realize the temperature change so estimated in each cooling zone, the number of the water pouring banks in each cooling zone is determined with use of the following temperature model equation (3) which shows the temperature change ~Tiw in water cooling in the ith cooling zone and the following temperature model equation (4) which shows the temperature change ~Tia in air cooling in the ith cooling C
zone. By using the above relations, cooling can be controlled so as to give desired temperature change to the steel sheet S
considering the amount of heat production QT upon the transformation, namely the temporal development of the transformation.
D T ; w = ( 1 /C p . p . h , t~
a ~ ;
t~-~
X ( T i - T w ) dt ~
i 1 / C p ~ ,~ ~ f1 - f t~ a d j tl-Z' j - T w ) dt y T j % ( C p ~ p ) ... ( 3 ) D T ; a - 1 / C p ~ p ~ h C ' C ( T Q i r -'- 2 7 ~ ) 4 / 1 0 0 4 + ( T j + 2 7 3 ) - a R 0 L L ' ( T j -- T W ) at + ~ T I / ( C P ~ p ) ... ( ,~ ) Here, Cp is the specific heat, j~ the specific gravity, plui the coefficient of cooling capacity of each upper cooling bank, d di the coefficient of cooling capacity of each lower cooling bank, Ti the temperature of the steel sheet S at the inlet of the ith cooling zone, Tw the temperature of the cooling water, C the emission constant, pL ROLL the heat transfer coefficient (for the associated roll), and Tair is air temperature.
Here, Fig. 2 illustrates the cooling bank pattern. The ~.' N ,~'."s 1341 2~7 ' cooling bank pattern is a target of the temperature change to be realized for the steel sheet S in each cooling bank when the steel sheet S is cooled by the cooling system R from the inlet temperature FDT to the target temperature CT. In the figure, a symbol A denotes a temperature change curve by air cooling (hereinafter, referred to as an air cooling curve A), and a symbol B denotes a temperature change curve by water cooling (hereinafter, referred to as a water cooling curve B).
In the first embodiment, the cooling system R shares the cooling between the cooling zones to a predetermined one located in the vicinity of the inlet for the water cooling and those located in the vicinity of the outlet for the air cooling. For this, the water cooling curve B passes through the inlet temperature FDT, while the air cooling curve A
passing through the target temperature CT.
The water cooling curve B is obtained by calculating the temperature change G1 Tiw using the equation (3) when water pouring valves are opened in succession from the first cooling bank to actuate the respective cooling zones to the ith cooling zone. In this situation, to take the amount of the heat production QTi due to the transformation into consideration, the calculated temperature change d Tiw is corrected by the amount of the heat production aTi due to the transformation calculated by the equation (2). In the same manner, the air cooling curve A is obtainable by correcting 1341 2~~
the temperature change d Tiacalculated using the equation (4) by the aforementioned amount of the heat production QTi due to the transformation. Here, a hatched portion designated at a symbol QT in the figure corresponds to the temperature rise of the steel sheet S which might be caused by the amount of the heat production QT in the transformation, for correction the cooling curves A, B.
It should be noted here that in a cooling zone at an intersection between the water and air cooling curves B and A
lU
(hereinafter, the zone is assumed to be a mth one), a cooling curve designated at C in the figure (hereinafter, referred to as a water cooling curve C) is required for changing smoothly the temperature of the steel sheet S from Tm to Tm+1. For this, the cooling capacity of the cooling banks in the aforementioned mth cooling zone is ad,iusted. The ad.iustment of the cooling capacity is done by changing the number of the water pouring cooling banks in the zone.
In succession, a procedure of determining the cooling bank pattern illustrated in Fig. 2, which is to be done in the cooling bank output pattern determining unit 14, will be described with reference to a flow chart shown in Fig. 3.
After starting the apparatus, the various parameters are first inputted into the cooling bank output pattern determining unit 14 in Step 105. The parameters include the target temperature CT, the cooling pattern of each bank, the inlet temperature FDT, the inlet speed, the outlet speed, and the thickness of the steel sheet S, etc. Then, the amount of heat production QTi of the steel sheet S under cooling is calculated by the equation (2) in Step 110.
In Step 120, the temperature change D Tia by the air cooling by each cooling bank is calculated by the equation (4) for determining the cooling curve A which passes through the target temperature CT.
In Step 130, the temperature change d Tiw by the water cooling by each cooling bank is calculated for determining the water cooling curve B. The calculation is done in succession starting from the lst cooling zone until the water cooling curve B resulting from the present calculation becomes less than the air cooling curve A calculated in Step 120. The details are as follows.
That is, in Step 131 cooling zones, for which the temperature changes Q 'fiw have been calculated, are set in succession. In Step 132 the total of the temperature changes 2~ d Tiw up to the finally set cooling bank is calculated. And in Step 133. it is judged whether or not a value of the total temperature change substracted from the inlet side temperature FD'f, i.e., the water cooling curve B is smaller than the air cooling curve A. If the result is negative, i.e., the value of the water cooling curve B is larger than the value of the air cooling curve A, then the operation advances to Step 134 1 3 41 ,~ ~ ) .
to increment by 1 the number of the associated cooling zone (i - i + 1), and returns to Step 132 for calculating the total of the temperature changes d Tiw of the cooling zones up to the incremented number by l, i.e., of the (i + 1)th cooling zone to calculate the value of the water cooling curve B in the cooling zone for the ,judgement in Step 133.
On the contrary, if the result in Step 133 is positive, i.e., if the value of the cooling curve B is ,fudged to be smaller than the value of the cooling curve A, then the operation advances to Step 140. Here, a cooling zone, which first gives the positive result, is assumed to be a mth one.
Thus, values giving the water cooling curve B are evaluated in succession up to the ,lust-mentioned mth cooling zone.
In the above Step 140, in order to achieve the cooling control in the mth cooling zone such that the steel sheet S is changed in its temperature following the water cooling curve C, the number of the water pouring banks, is determined by calculation, The number of the water pouring banks is determined such that the temperature Tm of the steel sheet S
on the entrance side of the present cooling zone becomes a temperature Tm+1 of the air cooling curve A on the exit side of the same. The completion of the calculation in this Step 140 gives the cooling bank output pattern.
The cooling bank output pattern such as illustrated in Fig. 2 as determined by the cooling bank output pattern determining unit 14 as described above is inputted into a cooling bank switching input/output unit 16. The cooling bank 13~i 2~7 switching input/output unit 16 controls the pouring of water in each cooling bank according to the inputted cooling bank output pattern while inputting results of the pouring in each cooling bank into the learning control unit 18.
The learning control section 18 learns the inputted pouring results, the inlet speed of the steel sheet S, the output speed of the same, and the inlet and outlet temperature, etc., and supplies to the bank output pattern determining unit 14 data for determination of the optimum cooling bank output pattern for the successive cooling control based upon the learned values.
Fig. 4 shows the second embodiment of the present invention.
In the second embodiment, a plurality of transformation rate sensor 20 are disposed in the cooling system R. Learning coefficient for calculatins the actual rate of the transformation is calculated in a transformation rate calculating unit 22 based on output signal from the respective transformation rate sensors 20 and inputted into the learning control unit 18 as is the first embodiment. Then, the learning coefficient used in the equation (1) is corrected.
Namely, when the actual rates Wi, W,j of the transf-ormation under cooling are obtained from the transformation rate sensors 20 disposed in the cooling system R~ the learning coefficients B, C in the equation (1) are expressed as follows:
C~ - ~n (,QnWi/~nW~)/ ~Qn (ti/t,i) ... (5) 134 2~r7.:
B~ _ t, ( (1/A) pnWi} -~ic~ . . . (6) where, Wi is a transformation rate at sensor i ti is a cooling time until sensor i B' , C' are learning coefficients calculated from actual values.
Wj is a transformation rate at sensor j, and tj is a cooling time until sensor j.
Then, the learning coefficients B and C are calculated by the following arithmetic assignment statements (7) and (8).
Bi = (1 - G) * B;_~ + G * B' ... (7) C~ _ (1 - G) * C~_~ + G * C' ... (8) wherein:
G is a smoothing coefficient for (weighning) shifhing average, B;_~, Ci_~ show old values of learning coefficients B and C before calculation and B~, Ci show new values of the learning coefficients B and C after the calculation.
By using the learning coefficients B, C and the equation (1), the temporal development of transformation can be corrected by learning.
The optimum cooling control of the steel sheet S is thus assured by taking the temporal development of the transformation into consideration using the heat production of the steel sheet S caused by the transforma-tion of the same.
Here, although in the above embodiment such a cooling bank output pattern as illustrated in Fig. 2, i.e., a cooling pattern for water cooling from the inlet side of the cooling apparatus was described, another cooling bank output pattern is possible according to the present invention without limitation to the cooling where the illustrated cooling bank output pattern is persued.
That is, such modifications are acheivable in response to cooling condition. For example, a cooling bank output pattern, where the first half of the cooling system R performs the air cooling while the second half of the same performing the water cooling, can be obtained by constructing the cooling bank output pattern such that the water cooling curve B reaches the target temperature CT and the air cooling curve A reaches the inlet temperature FDT. In addition, other arbitrary cooling patterns can be obtained in the cooling control by each cooling zone by continuously controlling the poured water from each bank and the degree of the air cooling by each bank without limitation to the above-described procedure where any cooling pattern was determined by the pouring the water from each cooling bank and by the interruption of the pouring.
Furthermore, although in the above embodiments the cooling apparatus for a steel sheet transferred on the hot rolling line was described as illustrated examples, the present invention may be applied for lines and steels without limitation thereto. For example, the present invention can be applied to steels such as thick steel, line steel, rod steel when they are cooled after hot processing.
In a hot rolling system, the steel sheet is cooled by a cooling system R illustrated in Fig. 5, for example.
As illustrated in figure 5 and 6, the hot rolling system is constructed such that a finishing rolling machine 1 rolls the steel sheet S, which sheet is then forcedly sent on a run-out table (not shown) in the direction of an arrow A in the figure and wound up by a coiler 6. There is disposed a cooling system R along the run-out table which is to cool the steel sheet S to a temperature suitable for the winding. The cooling system R includes on the side of an inlet thereof an inlet thermometer 2 for measuring the temperature of the steel sheet S to be cooled, and on the ~3~1247 side of an outlet thereof an outlet thermometer 5 for measuring the temperature of the steel sheet S after cooled.
The cooling system R is separated into two and dlSposed across vertically the run-out table. Each the separated portion includes a water cooling section 3 for cooling the steel sheet S by pouring water thereon and an air coolln$
section 4 for cooling the same with air. The air cooling section 4 has the same structure as thg water cooling section 3 when the latter stops the pouring of water on the steel sheet S. The water cooling section 3 and the air coolins section 4 disposed on the upper and lower sides of the coolins system R are divided into N coolin8 banks as designated at numerals 1 through H in the figure, respectively. Each bank is controllable in !ts cooling capability to cool the steel sheet S.
To control the cooling of the steel sheet S by the coolins system R, the cooling systes~ R is divided into a plurality of cooling zones each including the cooling banks of one or more along the run-out table, the cooling capability of each cooling zone being controlled by controlling the areount of supply of a cooling medium (cooling water) from each bank to the steel sheet S in conformity with the travelling of the steel sheet S, It is essential upon controlling the cooling capability ~~4~ 247 of the cooling system R as described above to estimate the amount of the cooling for the steel sheet S, i.e., the amount of a chance in the temperature of the same, in eaclr cooling Tone. For this, there have hitherto been proposed verletSe:~
of techniques tv estimate the temperature of the steel sheet S
under cooling and execute the cooling control pith high accuracy. A technique is knoxn among those techniques described above, as disclosed in Japanese Laid-Open Publication No. B1°199580. Wherein learning on heat transfer coefficients and treat emission rates through and from the upper and lower surfaces of the steel sheet S in running is determined by means of a Karman filter.
Hovever, steal materials produce some heat in general in their transformation from ~ to oc iron, for exempla form austenite to martenslte. So, by the just-mentioned technique wherein cooling capability of a covlins system is learnEd to estimate the temperature of the steel sheet for~ controlling the cooling, a problem causes that it is nrevnntrrd from corrtroll~ng the termperature of the steel sheet in due consideration of the heat production caused by the transformation of the steel, resulting in the reduced aeCUrarY
of the cooling control, On the oontrary, to consider the heat production caused by the transformation of a steel material. techniaue for controlling the coolln8 in consideration of transformation start timing end transformation time is disclosed In Reference on "Temperature Control In Winding of Hot Drawn High-Carbon ~34~ 2~7 Steel" presented at the.Sectfonal fleeting on the filth Hot Strip held at 1987, Japanese Patent Laid-Open Publication Nos.
57-7312, 58-199613 and 58r125312, etc.
In this technfque a temperature deveLoQment of the tr$nsfornation of s steel naterial is ignored and the amount of heat production in the transformation remains unchanged without depending on the lapse of time from the initiation of the transformation, and that the total amount of the heat production in the transformation caries in proPortfon to the lapse of time from the initiation of the transformation. In other xords, It Is considered in this technl~ue that the amount t1T of the heat production In the transformation changes stepwise from the transfomation initiation as shown in fig. 5 (A) .
However, it should actually be considered that the rate ~J
of the transformation of a steel material indicative of the temporal development of the transformation of the same under cooling chanses by a curve as illustrated in Fig. B tB), and the amount Q~. of the heat production chanses in prouortfon to the gradient ( 2W /'~T) of the rate W xith respect to time 'f.
Far example, xhen the rate W of the transformation changes as i 1 tustrated to the same f i$ure (B) , the gradient ( a W /~ 'f) of the rate W ohanges as illustrated in the same figure (C).
Hereby. the actual amount O1. of the heat production in the transformation chap&es as illustrated in the same fisure (D).
In contrast thereto, the conventional technique .iust-mentioned above'to control the cooling ignores the temporal developoent of the transformation of g steel but supposing the gmount 4T of tho heat production in the transformation being as Illustrated In the sang figure (A), without taking the actual aaount QT of the heat production in the transformation Which chances as lllustreted In the sama fignur~ (U), for example, at the Initiation and completion of thc~
transformation. So, estimation accuracy depends on accuracy of pre-mQasured data, and a measuring error directly caus~ss error in cooling control. Then, It has a dravback of the ac:curaey of tomparatura estimation being lovered folloved by the cooling control with Insufficient accuracy,
In view of the drawbacks of the conventional techniques, it is an ob.iect of the present invention to provide a control method of cooling a steel capable of accurate cooling control without causing erroneous estimation of steel temperature by determining the amount of cooling on the basis of steel temperature estimated taking the temporal development of the steel transformation upon cooling into consideration.
To achieve the above ob,iect, a control method of cooling a steel according to the present invention for controlling the temperature of the steel at a predetermined position on a line or at a predetermined time to a desired target temperature comprising: estimating the temperature of the steel taking into consideration the temporal development of transformation of the steel, and determining the amount of cooling on the 1341 2~T-_ basis of the estimated temperature of the steel, the estimation of the steel temperature being performed by correcting steel temperature estimated on the basis of the time of cooling the steel and on the cooling capability of a cooling system in response to the temporal development of the transformation of the steel caused by the cooling.
Preferably, the temporal development of the transformation of the steel is considered for a change in the amount of the heat production upon the transformation of the steel depending on the change in the rate of the transformation of the steel.
More particularly the present invention is directed to a method of cooling a steel in a cooling system by controlled cooling of the steel to a target temperature, the method comprising the steps of:
- determining the temporal development of the steel by calculating the rate W of a phase transformation of the steel or by detecting said rate W by using a transformation rate sensor, and thereafter;
- calculating the heat produced during said transformation;
- estimating the temperature change of the steel for a time period based on cooling time of the steel and cooling capability of the cooling system;
- correcting error in the estimated temperature change by using the calculated heat produced during transformation;
- calculating a cooling bank pattern from parameters including the target temperature, the determined heat produced during transformation, and the corrected temperature change; and I
13 ~r 1 2 ~r 7 - determining a target temperature pattern on the basis of the cooling bank pattern and controlling the cooling system to cool the steel to a target temperature based upon the calculated cooling bank pattern.
Furthermore, in accordance with a preferred embodiment of the present invention, the rate W of the transformation is evaluated by the following formula as a function of the cooling time t:
W = 1 - exp jA ~ (t/B) C~
where A is a parameter for calculating the rate of the transformation, which is defined by the component, temperature, thickness, and geometrical cooling pattern of each steel used. In fact, parameter A is a tuning constant to fix the slope of the exponent curve so that actual values coincide with theoretical values.
B is a cooling time until center of transformation.
Parameter B corresponds to a time from outlet of finishing mill until the transformation rate reachs a predetermined value (50~ for example).
C is a gradient of the transformation curve. This parameter is a power which is theoretically determined from growth rate of metallic structure in view of metallography.
6a I
These parameters are determined by statistically processing results of experiments using actual steel.
Furthermore, preferably, the rate of the transformation is detected by using a transformation rate sensor.
Furthermore, in accordance with yet another preferred embodiment of the present invention, the rate of the transformation is established by learning an output of a transformation rate sensor.
Furthermore, in accordance with yet another preferred embodiment of the present invention, the cooling capability of the cooling system is established by learning the results of the cooling, the speed of carrying the steel and teh detected temperature.
Furthermore, in accordance with yet another preferred embodiment of the present invention, the cooling control is conducted by changing the amount of cooling water of each cooling bank and/or number of working banks according to the amounht of cooling.
Furthermore, in accordance with yet another preferred embodiment of the present invention, the cooling control is conducted by combining a water cooling and an air cooling according to the combination of temperature curves which are based on inlet temperature and outlet te~perature, respectively, the number of water poured banks are changed at the cooling zone where both cooling curves intersect with each other, and cooling is conducted according to a cooling curve which combines both cooling curves.
According to the present invention any erroneous estimation of the steel temperature with respect to an actual steel temperature in cooling can greatly be reduced, assuring accurate control of the amount of cooling followed 13~~ 24T
by the realization of cooling which provides a desired change of the temperature. This establishes the manufac-ture of a steel of stable quality with high productivity.
Additionally, when the temporal development of the transformation of the steel is considered for a change in the amount of heat produced upon the transformation of the steel depending on the change in the rate of the transformation of the steel, the temporal development of the transformation to be expressed in terms of an objective to numerical value, say the amount of heat production of hte steel by the transformation thereby facilitating the estimation of the steel temperature.
According to the present invention, any error of the estimated temperature with respect to actual steel temperature can greatly be reduced, resulting in highly accurate cooling of the steel. The present invention thus assures excellent effects such as manufacture of a steel of a stable quality with satisfactory productivity.
The exact nature of this invention, as well as other object and advantages thereof, will be readily apparent from r. ~:.:
l3~if 2~) consideration of the following specification relating to the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof and wherein:
Fig. 1 is a block diagram partly including a cross sectional view, illustrating the whole arrangement of a cooling apparatus associataed with a first embodiment of the present invention:
Fig. 2 is a diagram illustrating an example of a cooling bank output pattern executed in a cooling system associated with the first embodiment:
Fig. 3 is a flow chart illustrating an example of a procedure of determining the cooling bank output pattern:
Fig. 4 is a block diagram partly including a cross sectional view, illustrating the whole arrangement of a second embodiment of the present invention:
Fig. 5 is a cross sectional view illustrating an example of a conventional cooling apparatus: and Fig. 6 is diagrams illustrating an example of a relationship among the conventionally considered amount of heat production caused by transformation, the conventionally considered rate of the transformation, the actual amount of heat production caused by transformation, and the actual change in the rate of the transformation.
[Embodiments]
In what follows, embodiments of the present invention will be described in detail with reference to the accompanying _ g _ 1341 2~7 drawings.
The first embodiment is a control apparatus wherein the control method of the present invention is executed to cool a hot drawn steel with use of a cooling system R in a cooling S apparatus located on a hot drawing line as illustrated in Fig.
1. The cooling system R is of the same construction as that shown in Fig. 5, wherein the steel sheet S rolled through the finishing rolling machine 1 is succesively wound up by the coiler 6 through the cooling system R. The finishing rolling machine 1 disposed on the inlet side of the cooling system R
includes an inlet speed detector 10 for detecting the carrying speed of the steel sheet S carried after rolled by the finishing rolling machine 1. In addtion, the coiler 6 disposed on the outlet side of the cooling system R includes an outlet speed detector 12 for detecting the wind-up speed of the steel sheet S. There are further provided inlet and outlet thermometers 2, 5 on the inlet and outlet sides of the cooling system R. Here, the like symbols shall be applied to the like configurations and operations as those in the conventional cooling system illustrated in Fig. 5, and detailed description is omitted..
The cooling system R, which includes a predetermined number of cooling zones, each zone having at least one cooling bank. The pouring amount of coolant (for example, water) from the cooling bank is controlled to control the cooling of the steel sheet S passing through each cooling zone.
Here, the inlet thermometer 2, inlet speed detector 10 C
and outlet speed detector 12 shown in Fig. 1 transmit respective detection signals to a cooling bank output pattern determining unit 14. The cooling bank output pattern determining unit 14 determines by computation a pattern to control the cooling capability of each cooling bank according to a cooling time t (hereinafter, referred to as a cooling bank pattern) for obtaining the desired temperature decrease of the steel sheet S in response to the cooling time t based upon the inputted inlet side temperature, the carrying speed of the steel sheet S, the wind-up speed, a preset target termperature of the steel sheet S and sheet thickness, etc..
The cooling bank pattern determined as described above is inputted into a cooling bank switching input/output unit 16.
The cooling bank switching input/output unit 16 controls the cooling capability of each cooling bank in response to the inputted cooling bank pattern.
Cooling results of pouring water by each bank of the cooling system R controlled by the bank switching input/output unit 16 are fed into a learning control unit 18. The learning control unit 18 receives detection signals from the inlet speed detector 10, the output speed detector 12, the inlet thermometer 2, and the outlet thermometer 5, and learns the - cooling capability of the cooling system R on the basis of the inputted aforesaid cooling results and the detection signals.
In succession, operation of the first embodiment will be described.
In the first embodiment, the change in the temperature of the steel sheet S after the lapse of predetermined time is estimated on the basis of the cooling time of the steel sheet S and of the cooling capability of the cooling system R. At the same time, the amount of heat production of the steel sheet S, for example, due to the transformation of the same is calculated in the response to the temporal development of the transformation caused by the cooling of the steel sheet S. Then, the error of the estimated change in the temperature of the steel sheet S is corrected by the to calculated amount of heat production of the steel sheet s due to the transformation of the same. Then the cooling bank pattern of the cooling system R is determined for cooling control so as to provide the corrected amount of the change in the temperature of the steel sheet S.
It will first be described how the temporal development of the transformation of the steel sheet S is obtained.
The rate W of the transformation of the steel sheet S under cooling can be calculated from the following 2o equation (1) as a function of the cooling time t.
W = 1 - exp [A~(t/B)~] ... (1) Here, A, B, and C are parameters determined by the component, temperature, thickness, and cooling pattern of each steel sheet S. More specifically, A is a parameter for calculating the rate of the transformation, which is defined by the component, temperature, thickness, and geometrical cooling pattern of each steel used.
B is a cooling time until center of transformation (when the transformation rate reach 50~).
C is a gradient of the transformation curve.
These parameters are determined by statistically processing results of experiments using actual steel.
The accuracy of estimating the rate W of the C
transformation can be increased by correcting the coeffi-cients for learning according to the learning results based on signals from a plurality of sensors for detecting the transformation rate, disposed in the cooling system.
The transformation rate sensor comprises by a combination of an exiting coil and magnetic detecting element, for example, and the transformation rate is detected by measuring phase transformation through a change in magnetic permeability. Such a sensor is disclosed in Canadian Patent 1,260,064.
It is possible to know the temporal development of the transformation of the steel sheet S with respect to time by the equation (1). In addition, the means to know the temporal development of the transformation of the steel sheet S is not limited to the one which utilizes the relationship of the equation (1). Instead, the transformation rate sensor to directly detect the rate of the transformation can be used.
On the assumption that in the cooling system R
including the cooling zones of the predetermined number, the cooling time from the inlet side to the ith cooling zone is ti, the amount of the change in the rate of the transformation ~ Wi - (Wi - Wi-1) in the ith cooling zone can be calculated on the basis of the cooling time ti ~ (ti - ti-1) in the ith cooling zone and the equation (1).
The amount of heat production QTi of the steel sheet S due to the transformation in the ith cooling zone when the amount of the change in the rate of the transformation D Wi, is given by the following equation (2).
QTi - H * OWi...(2) Here, H is latent heat of the steel sheet S upon the transformation (a physical quantity which can be determined from the component of the steel sheet S, the kind of the same, and the temperature of the same).
Therefore, the amount of heat production QT upon the transformation in each cooling zone when the steel sheet S is cooled from the inlet temperature FDT (Finished Derivery Temperature) to the target temperature CT (Cooling Temperature) is calculated by using the equation (2). Then the temperature change of the steel sheet S estimated from the cooling time of the steel sheet S and the capability of the cooling system R is corrected by the amount of heat production QTi upon the transformation so calculated. In consequence, the accurate temperature change of the steel sheet S as the sheet passes through each cooling zone can be estimated.
To realize the temperature change so estimated in each cooling zone, the number of the water pouring banks in each cooling zone is determined with use of the following temperature model equation (3) which shows the temperature change ~Tiw in water cooling in the ith cooling zone and the following temperature model equation (4) which shows the temperature change ~Tia in air cooling in the ith cooling C
zone. By using the above relations, cooling can be controlled so as to give desired temperature change to the steel sheet S
considering the amount of heat production QT upon the transformation, namely the temporal development of the transformation.
D T ; w = ( 1 /C p . p . h , t~
a ~ ;
t~-~
X ( T i - T w ) dt ~
i 1 / C p ~ ,~ ~ f1 - f t~ a d j tl-Z' j - T w ) dt y T j % ( C p ~ p ) ... ( 3 ) D T ; a - 1 / C p ~ p ~ h C ' C ( T Q i r -'- 2 7 ~ ) 4 / 1 0 0 4 + ( T j + 2 7 3 ) - a R 0 L L ' ( T j -- T W ) at + ~ T I / ( C P ~ p ) ... ( ,~ ) Here, Cp is the specific heat, j~ the specific gravity, plui the coefficient of cooling capacity of each upper cooling bank, d di the coefficient of cooling capacity of each lower cooling bank, Ti the temperature of the steel sheet S at the inlet of the ith cooling zone, Tw the temperature of the cooling water, C the emission constant, pL ROLL the heat transfer coefficient (for the associated roll), and Tair is air temperature.
Here, Fig. 2 illustrates the cooling bank pattern. The ~.' N ,~'."s 1341 2~7 ' cooling bank pattern is a target of the temperature change to be realized for the steel sheet S in each cooling bank when the steel sheet S is cooled by the cooling system R from the inlet temperature FDT to the target temperature CT. In the figure, a symbol A denotes a temperature change curve by air cooling (hereinafter, referred to as an air cooling curve A), and a symbol B denotes a temperature change curve by water cooling (hereinafter, referred to as a water cooling curve B).
In the first embodiment, the cooling system R shares the cooling between the cooling zones to a predetermined one located in the vicinity of the inlet for the water cooling and those located in the vicinity of the outlet for the air cooling. For this, the water cooling curve B passes through the inlet temperature FDT, while the air cooling curve A
passing through the target temperature CT.
The water cooling curve B is obtained by calculating the temperature change G1 Tiw using the equation (3) when water pouring valves are opened in succession from the first cooling bank to actuate the respective cooling zones to the ith cooling zone. In this situation, to take the amount of the heat production QTi due to the transformation into consideration, the calculated temperature change d Tiw is corrected by the amount of the heat production aTi due to the transformation calculated by the equation (2). In the same manner, the air cooling curve A is obtainable by correcting 1341 2~~
the temperature change d Tiacalculated using the equation (4) by the aforementioned amount of the heat production QTi due to the transformation. Here, a hatched portion designated at a symbol QT in the figure corresponds to the temperature rise of the steel sheet S which might be caused by the amount of the heat production QT in the transformation, for correction the cooling curves A, B.
It should be noted here that in a cooling zone at an intersection between the water and air cooling curves B and A
lU
(hereinafter, the zone is assumed to be a mth one), a cooling curve designated at C in the figure (hereinafter, referred to as a water cooling curve C) is required for changing smoothly the temperature of the steel sheet S from Tm to Tm+1. For this, the cooling capacity of the cooling banks in the aforementioned mth cooling zone is ad,iusted. The ad.iustment of the cooling capacity is done by changing the number of the water pouring cooling banks in the zone.
In succession, a procedure of determining the cooling bank pattern illustrated in Fig. 2, which is to be done in the cooling bank output pattern determining unit 14, will be described with reference to a flow chart shown in Fig. 3.
After starting the apparatus, the various parameters are first inputted into the cooling bank output pattern determining unit 14 in Step 105. The parameters include the target temperature CT, the cooling pattern of each bank, the inlet temperature FDT, the inlet speed, the outlet speed, and the thickness of the steel sheet S, etc. Then, the amount of heat production QTi of the steel sheet S under cooling is calculated by the equation (2) in Step 110.
In Step 120, the temperature change D Tia by the air cooling by each cooling bank is calculated by the equation (4) for determining the cooling curve A which passes through the target temperature CT.
In Step 130, the temperature change d Tiw by the water cooling by each cooling bank is calculated for determining the water cooling curve B. The calculation is done in succession starting from the lst cooling zone until the water cooling curve B resulting from the present calculation becomes less than the air cooling curve A calculated in Step 120. The details are as follows.
That is, in Step 131 cooling zones, for which the temperature changes Q 'fiw have been calculated, are set in succession. In Step 132 the total of the temperature changes 2~ d Tiw up to the finally set cooling bank is calculated. And in Step 133. it is judged whether or not a value of the total temperature change substracted from the inlet side temperature FD'f, i.e., the water cooling curve B is smaller than the air cooling curve A. If the result is negative, i.e., the value of the water cooling curve B is larger than the value of the air cooling curve A, then the operation advances to Step 134 1 3 41 ,~ ~ ) .
to increment by 1 the number of the associated cooling zone (i - i + 1), and returns to Step 132 for calculating the total of the temperature changes d Tiw of the cooling zones up to the incremented number by l, i.e., of the (i + 1)th cooling zone to calculate the value of the water cooling curve B in the cooling zone for the ,judgement in Step 133.
On the contrary, if the result in Step 133 is positive, i.e., if the value of the cooling curve B is ,fudged to be smaller than the value of the cooling curve A, then the operation advances to Step 140. Here, a cooling zone, which first gives the positive result, is assumed to be a mth one.
Thus, values giving the water cooling curve B are evaluated in succession up to the ,lust-mentioned mth cooling zone.
In the above Step 140, in order to achieve the cooling control in the mth cooling zone such that the steel sheet S is changed in its temperature following the water cooling curve C, the number of the water pouring banks, is determined by calculation, The number of the water pouring banks is determined such that the temperature Tm of the steel sheet S
on the entrance side of the present cooling zone becomes a temperature Tm+1 of the air cooling curve A on the exit side of the same. The completion of the calculation in this Step 140 gives the cooling bank output pattern.
The cooling bank output pattern such as illustrated in Fig. 2 as determined by the cooling bank output pattern determining unit 14 as described above is inputted into a cooling bank switching input/output unit 16. The cooling bank 13~i 2~7 switching input/output unit 16 controls the pouring of water in each cooling bank according to the inputted cooling bank output pattern while inputting results of the pouring in each cooling bank into the learning control unit 18.
The learning control section 18 learns the inputted pouring results, the inlet speed of the steel sheet S, the output speed of the same, and the inlet and outlet temperature, etc., and supplies to the bank output pattern determining unit 14 data for determination of the optimum cooling bank output pattern for the successive cooling control based upon the learned values.
Fig. 4 shows the second embodiment of the present invention.
In the second embodiment, a plurality of transformation rate sensor 20 are disposed in the cooling system R. Learning coefficient for calculatins the actual rate of the transformation is calculated in a transformation rate calculating unit 22 based on output signal from the respective transformation rate sensors 20 and inputted into the learning control unit 18 as is the first embodiment. Then, the learning coefficient used in the equation (1) is corrected.
Namely, when the actual rates Wi, W,j of the transf-ormation under cooling are obtained from the transformation rate sensors 20 disposed in the cooling system R~ the learning coefficients B, C in the equation (1) are expressed as follows:
C~ - ~n (,QnWi/~nW~)/ ~Qn (ti/t,i) ... (5) 134 2~r7.:
B~ _ t, ( (1/A) pnWi} -~ic~ . . . (6) where, Wi is a transformation rate at sensor i ti is a cooling time until sensor i B' , C' are learning coefficients calculated from actual values.
Wj is a transformation rate at sensor j, and tj is a cooling time until sensor j.
Then, the learning coefficients B and C are calculated by the following arithmetic assignment statements (7) and (8).
Bi = (1 - G) * B;_~ + G * B' ... (7) C~ _ (1 - G) * C~_~ + G * C' ... (8) wherein:
G is a smoothing coefficient for (weighning) shifhing average, B;_~, Ci_~ show old values of learning coefficients B and C before calculation and B~, Ci show new values of the learning coefficients B and C after the calculation.
By using the learning coefficients B, C and the equation (1), the temporal development of transformation can be corrected by learning.
The optimum cooling control of the steel sheet S is thus assured by taking the temporal development of the transformation into consideration using the heat production of the steel sheet S caused by the transforma-tion of the same.
Here, although in the above embodiment such a cooling bank output pattern as illustrated in Fig. 2, i.e., a cooling pattern for water cooling from the inlet side of the cooling apparatus was described, another cooling bank output pattern is possible according to the present invention without limitation to the cooling where the illustrated cooling bank output pattern is persued.
That is, such modifications are acheivable in response to cooling condition. For example, a cooling bank output pattern, where the first half of the cooling system R performs the air cooling while the second half of the same performing the water cooling, can be obtained by constructing the cooling bank output pattern such that the water cooling curve B reaches the target temperature CT and the air cooling curve A reaches the inlet temperature FDT. In addition, other arbitrary cooling patterns can be obtained in the cooling control by each cooling zone by continuously controlling the poured water from each bank and the degree of the air cooling by each bank without limitation to the above-described procedure where any cooling pattern was determined by the pouring the water from each cooling bank and by the interruption of the pouring.
Furthermore, although in the above embodiments the cooling apparatus for a steel sheet transferred on the hot rolling line was described as illustrated examples, the present invention may be applied for lines and steels without limitation thereto. For example, the present invention can be applied to steels such as thick steel, line steel, rod steel when they are cooled after hot processing.
In a hot rolling system, the steel sheet is cooled by a cooling system R illustrated in Fig. 5, for example.
As illustrated in figure 5 and 6, the hot rolling system is constructed such that a finishing rolling machine 1 rolls the steel sheet S, which sheet is then forcedly sent on a run-out table (not shown) in the direction of an arrow A in the figure and wound up by a coiler 6. There is disposed a cooling system R along the run-out table which is to cool the steel sheet S to a temperature suitable for the winding. The cooling system R includes on the side of an inlet thereof an inlet thermometer 2 for measuring the temperature of the steel sheet S to be cooled, and on the ~3~1247 side of an outlet thereof an outlet thermometer 5 for measuring the temperature of the steel sheet S after cooled.
The cooling system R is separated into two and dlSposed across vertically the run-out table. Each the separated portion includes a water cooling section 3 for cooling the steel sheet S by pouring water thereon and an air coolln$
section 4 for cooling the same with air. The air cooling section 4 has the same structure as thg water cooling section 3 when the latter stops the pouring of water on the steel sheet S. The water cooling section 3 and the air coolins section 4 disposed on the upper and lower sides of the coolins system R are divided into N coolin8 banks as designated at numerals 1 through H in the figure, respectively. Each bank is controllable in !ts cooling capability to cool the steel sheet S.
To control the cooling of the steel sheet S by the coolins system R, the cooling systes~ R is divided into a plurality of cooling zones each including the cooling banks of one or more along the run-out table, the cooling capability of each cooling zone being controlled by controlling the areount of supply of a cooling medium (cooling water) from each bank to the steel sheet S in conformity with the travelling of the steel sheet S, It is essential upon controlling the cooling capability ~~4~ 247 of the cooling system R as described above to estimate the amount of the cooling for the steel sheet S, i.e., the amount of a chance in the temperature of the same, in eaclr cooling Tone. For this, there have hitherto been proposed verletSe:~
of techniques tv estimate the temperature of the steel sheet S
under cooling and execute the cooling control pith high accuracy. A technique is knoxn among those techniques described above, as disclosed in Japanese Laid-Open Publication No. B1°199580. Wherein learning on heat transfer coefficients and treat emission rates through and from the upper and lower surfaces of the steel sheet S in running is determined by means of a Karman filter.
Hovever, steal materials produce some heat in general in their transformation from ~ to oc iron, for exempla form austenite to martenslte. So, by the just-mentioned technique wherein cooling capability of a covlins system is learnEd to estimate the temperature of the steel sheet for~ controlling the cooling, a problem causes that it is nrevnntrrd from corrtroll~ng the termperature of the steel sheet in due consideration of the heat production caused by the transformation of the steel, resulting in the reduced aeCUrarY
of the cooling control, On the oontrary, to consider the heat production caused by the transformation of a steel material. techniaue for controlling the coolln8 in consideration of transformation start timing end transformation time is disclosed In Reference on "Temperature Control In Winding of Hot Drawn High-Carbon ~34~ 2~7 Steel" presented at the.Sectfonal fleeting on the filth Hot Strip held at 1987, Japanese Patent Laid-Open Publication Nos.
57-7312, 58-199613 and 58r125312, etc.
In this technfque a temperature deveLoQment of the tr$nsfornation of s steel naterial is ignored and the amount of heat production in the transformation remains unchanged without depending on the lapse of time from the initiation of the transformation, and that the total amount of the heat production in the transformation caries in proPortfon to the lapse of time from the initiation of the transformation. In other xords, It Is considered in this technl~ue that the amount t1T of the heat production In the transformation changes stepwise from the transfomation initiation as shown in fig. 5 (A) .
However, it should actually be considered that the rate ~J
of the transformation of a steel material indicative of the temporal development of the transformation of the same under cooling chanses by a curve as illustrated in Fig. B tB), and the amount Q~. of the heat production chanses in prouortfon to the gradient ( 2W /'~T) of the rate W xith respect to time 'f.
Far example, xhen the rate W of the transformation changes as i 1 tustrated to the same f i$ure (B) , the gradient ( a W /~ 'f) of the rate W ohanges as illustrated in the same figure (C).
Hereby. the actual amount O1. of the heat production in the transformation chap&es as illustrated in the same fisure (D).
In contrast thereto, the conventional technique .iust-mentioned above'to control the cooling ignores the temporal developoent of the transformation of g steel but supposing the gmount 4T of tho heat production in the transformation being as Illustrated In the sang figure (A), without taking the actual aaount QT of the heat production in the transformation Which chances as lllustreted In the sama fignur~ (U), for example, at the Initiation and completion of thc~
transformation. So, estimation accuracy depends on accuracy of pre-mQasured data, and a measuring error directly caus~ss error in cooling control. Then, It has a dravback of the ac:curaey of tomparatura estimation being lovered folloved by the cooling control with Insufficient accuracy,
Claims (9)
1. A method of cooling a steel in a cooling system by controlled cooling of the steel to a target temperature, the method comprising the steps of:
- determining the temporal development of the steel by calculating the rate W of a phase transformation of the steel or by detecting said rate W by using a transformation rate sensor, and thereafter;
- calculating the heat produced during said transformation;
- estimating the temperature change of the steel for a time period based on cooling time of the steel and cooling capability of the cooling system;
- correcting error in the estimated temperature change by using the calculated heat produced during transformation;
- calculating a cooling bank pattern from parameters including the target temperature, the determined heat produced during transformation, and the corrected temperature change; and - determining a target temperature pattern on the basis of the cooling bank pattern and controlling the cooling system to cool the steel to a target temperature based upon the calculated cooling bank pattern.
- determining the temporal development of the steel by calculating the rate W of a phase transformation of the steel or by detecting said rate W by using a transformation rate sensor, and thereafter;
- calculating the heat produced during said transformation;
- estimating the temperature change of the steel for a time period based on cooling time of the steel and cooling capability of the cooling system;
- correcting error in the estimated temperature change by using the calculated heat produced during transformation;
- calculating a cooling bank pattern from parameters including the target temperature, the determined heat produced during transformation, and the corrected temperature change; and - determining a target temperature pattern on the basis of the cooling bank pattern and controlling the cooling system to cool the steel to a target temperature based upon the calculated cooling bank pattern.
2. A method of cooling a steel according to claim 1, characterized in that said rate W of phase transformation is evaluated by the following formula as a function of the cooling time t:
W = 1 - exp [A~(t/B)C]
where A is a parameter for calculating the rate of the transformation, which is defined by the component, temperature, thickness, and geometrical cooling pattern of each steel used, B is a cooling time until center of transforma-tion, and C is a gradient of the transformation curve.
W = 1 - exp [A~(t/B)C]
where A is a parameter for calculating the rate of the transformation, which is defined by the component, temperature, thickness, and geometrical cooling pattern of each steel used, B is a cooling time until center of transforma-tion, and C is a gradient of the transformation curve.
3. A method of cooling a steel according to claim 1, characterized in that said rate W of phase transformation is detected by using a transformation rate sensor.
4. A method of cooling a steel according to claim 2, characterized in that said rate W phase of transformation is established by learning an output of a transformation rate sensor.
5. A method of cooling a steel according to claim 1, characterized in that said cooling capability of the cooling system is established by learning the results of the cooling, the speed of carrying the steel and the detected temperature.
6. A method of cooling a steel according to claim 1, characterized in that said cooling control is conducted by changing an amount of cooling water of each cooling bank and/or number of working banks according to the amount of cooling.
7. A method of cooling a steel according to claim 6, characterized in that said cooling control is conducted by combining water cooling and air cooling according to a combination of separate temperature curves which are based on an inlet temperature and an outlet temperature, respectively, a number of water poured banks are changed at a cooling zone where both cooling curves intersect with each other, and cooling is conducted according to a cooling curve which combines both cooling curves.
8. A method of cooling a steel sheet according to claim 2, wherein parameters in a control model are tuned based upon results of control so as to increase the accuracy of the control model.
9. A method of cooling a steel according to claim 4, wherein the rate of phase transformation W is corrected by the following equations in response to an output from transformation rate sensors, C' = ln (ln~i/ln~j)/ln(ti/tj), B' - ti{(1/A)ln~i}-1/C' Bi = (1 - G)*Bi-1+G*B', and Ci = (1-G) Ci-1 + G*C', where ~ i, ~ j are measured rates of the transformation by sensors i and j;
t i, t j are the cooling time from an inlet side to an ith or jth cooling zone, and G is a smoothing coefficient for shifting average, Bi-1 and Ci-1 are values of the learning coefficient B and C respectively before calculation and Bi and Ci are values of the learning coefficient B
and C respectively, after calculation.
t i, t j are the cooling time from an inlet side to an ith or jth cooling zone, and G is a smoothing coefficient for shifting average, Bi-1 and Ci-1 are values of the learning coefficient B and C respectively before calculation and Bi and Ci are values of the learning coefficient B
and C respectively, after calculation.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP1989/000603 WO1990015885A1 (en) | 1989-06-16 | 1989-06-16 | Steel material cooling control method |
| EP89907279A EP0453566B1 (en) | 1989-06-16 | 1989-06-16 | Steel material cooling control method |
| DE68928639T DE68928639T2 (en) | 1989-06-16 | 1989-06-16 | METHOD FOR CONTROLLING THE COOLING OF STEEL MATERIAL |
| CA000603379A CA1341247C (en) | 1989-06-16 | 1989-06-20 | Control method of cooling steel |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/JP1989/000603 WO1990015885A1 (en) | 1989-06-16 | 1989-06-16 | Steel material cooling control method |
| CA000603379A CA1341247C (en) | 1989-06-16 | 1989-06-20 | Control method of cooling steel |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1341247C true CA1341247C (en) | 2001-06-05 |
Family
ID=25672819
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000603379A Expired - Fee Related CA1341247C (en) | 1989-06-16 | 1989-06-20 | Control method of cooling steel |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1341247C (en) |
| WO (1) | WO1990015885A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2731116C1 (en) * | 2016-12-20 | 2020-08-28 | Арселормиттал | Method for dynamic control of thermally treated steel sheet production process |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61110723A (en) * | 1984-11-02 | 1986-05-29 | Kawasaki Steel Corp | Cooling controlling method of hot-rolled steel plate |
| JPS61266524A (en) * | 1985-05-20 | 1986-11-26 | Kawasaki Steel Corp | Method for controlling cooling of steel product |
-
1989
- 1989-06-16 WO PCT/JP1989/000603 patent/WO1990015885A1/en active IP Right Grant
- 1989-06-20 CA CA000603379A patent/CA1341247C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| WO1990015885A1 (en) | 1990-12-27 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP4287740B2 (en) | Cooling method for hot-rolled material and corresponding cooling section model | |
| CN101056721B (en) | Method for producing metal | |
| CN103920717B (en) | Preset value calculation device and preset value calculation method | |
| CN101519735B (en) | Method for controlling strip-steel head and tail temperature | |
| JP2783124B2 (en) | Temperature control method for hot rolled steel | |
| KR100643373B1 (en) | Method of controlling longitudinal direction temperature of thick hot-rolled steel plate | |
| CA1341247C (en) | Control method of cooling steel | |
| CN101633004B (en) | Method for designing generalized observer in controlled cooling of thick plate after rolling | |
| EP0453566B1 (en) | Steel material cooling control method | |
| KR900006692B1 (en) | Method of controlling of hot rolled steel sheet and system therefor | |
| KR100306147B1 (en) | Method for controlling cooling of hot rolled steel sheet | |
| JP2786386B2 (en) | Cooling control method and cooling control device for hot rolled steel | |
| CN109772896A (en) | Hot continuous rolling based on Smith Prediction Control becomes target flatness degree control method | |
| KR100568358B1 (en) | Hot strip cooling control mothode for chage target temperature | |
| JPH01162508A (en) | Cooling control method for steel material | |
| JPH0275409A (en) | Method for controlling winding temperature of hot rolled steel sheet | |
| JP3054031B2 (en) | Method of controlling winding temperature of hot-rolled steel strip | |
| JP3450108B2 (en) | Hot rolled sheet cooling control device | |
| JP4256558B2 (en) | Steel plate shape determination apparatus, method, and computer-readable storage medium | |
| JPS63317208A (en) | Control device for cooling hot rolled steel strip | |
| JPH08252622A (en) | Method for learning correction in temperature calculation of material on outlet side of hot rolling mill | |
| KR950007469B1 (en) | Steel material cooling control method | |
| KR100757193B1 (en) | cooling control method of high carbon hot-rolled strip taken phase transformation into account | |
| JPH03287720A (en) | Method for controlling hot finish rolling temperature of strip | |
| JPH0688060B2 (en) | Temperature control method for hot rolled steel |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |