CA1266602A - Method and apparatus for cooling steel strips - Google Patents
Method and apparatus for cooling steel stripsInfo
- Publication number
- CA1266602A CA1266602A CA000514447A CA514447A CA1266602A CA 1266602 A CA1266602 A CA 1266602A CA 000514447 A CA000514447 A CA 000514447A CA 514447 A CA514447 A CA 514447A CA 1266602 A CA1266602 A CA 1266602A
- Authority
- CA
- Canada
- Prior art keywords
- cooling
- steel strip
- cooling liquid
- flow
- steel
- 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.)
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Classifications
-
- 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
-
- 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
-
- 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
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/62—Quenching devices
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Strip Materials And Filament Materials (AREA)
Abstract
METHOD AND APPARATUS FOR COOLING STEEL STRIPS
Abstract of the Disclosure A method and apparatus for cooling steel strips by means of a cooling liquid in a continuous annealing line. The cooling liquid is forced to flow as steady flows along both surfaces of a steel strip in directions opposite to moving directions of the steel strip. An apparatus comprises flow rectifier plates in opposition to both the surfaces of the steel strip to form flow passages between the steel strip and the flow rectifier plates for forcing the cooling liquid through the flow passages, at least one cooling liquid supply port on a downstream side of the moving steel strip and at least one cooling liquid exhaust port on an upstream side of the moving steel strip. In order to control the cooled steel strip temperature, part of the cooling liquid used for cooling the steel strip is mixed with fresh cooling liquid to control temperature of cooling liquid to be used for cooling by adjusting a mixing ratio of the used and fresh cooling liquids, thereby keeping temperature of the cooled steel strip within a predetermined target temperature range.
Abstract of the Disclosure A method and apparatus for cooling steel strips by means of a cooling liquid in a continuous annealing line. The cooling liquid is forced to flow as steady flows along both surfaces of a steel strip in directions opposite to moving directions of the steel strip. An apparatus comprises flow rectifier plates in opposition to both the surfaces of the steel strip to form flow passages between the steel strip and the flow rectifier plates for forcing the cooling liquid through the flow passages, at least one cooling liquid supply port on a downstream side of the moving steel strip and at least one cooling liquid exhaust port on an upstream side of the moving steel strip. In order to control the cooled steel strip temperature, part of the cooling liquid used for cooling the steel strip is mixed with fresh cooling liquid to control temperature of cooling liquid to be used for cooling by adjusting a mixing ratio of the used and fresh cooling liquids, thereby keeping temperature of the cooled steel strip within a predetermined target temperature range.
Description
~2~60Z 60-162,909 comb.
METHOD AND APPARATUS FOR COOL~NG STEEI. _TRIPS
This invention relates to a method of cooling steel strips in continuous annealing lines and an apparatus for carrying out the method, and more particularly to a method and an apparatus for effectively 05 cooling steel strips to target temperatures in controlled manner irrespective of change in amount of the steel strips and change in temperature of supplied cooling water due to seasonal factors.
Steel ~strips to be surface-treated or used for deep-drawing are generally subjected to heat-treatment such as heating, soaking and cooling in succession, so called "continuous annealing" after cold rolling in order to give predetermined mechanical properties to the steel strips.
Recently~ it has been widely used to pass steel strips at higher speeds through the above continuous annealing lines to increase the treating capacity to great extent for reasons such as increased demand of very thin steel strips less than ~.3 mm Accordingly, furnace installations for continuous annealing have been unavoidably elongated and enlarged to give rise to problems such as construction cost and spaces and in operation which will be explained
METHOD AND APPARATUS FOR COOL~NG STEEI. _TRIPS
This invention relates to a method of cooling steel strips in continuous annealing lines and an apparatus for carrying out the method, and more particularly to a method and an apparatus for effectively 05 cooling steel strips to target temperatures in controlled manner irrespective of change in amount of the steel strips and change in temperature of supplied cooling water due to seasonal factors.
Steel ~strips to be surface-treated or used for deep-drawing are generally subjected to heat-treatment such as heating, soaking and cooling in succession, so called "continuous annealing" after cold rolling in order to give predetermined mechanical properties to the steel strips.
Recently~ it has been widely used to pass steel strips at higher speeds through the above continuous annealing lines to increase the treating capacity to great extent for reasons such as increased demand of very thin steel strips less than ~.3 mm Accordingly, furnace installations for continuous annealing have been unavoidably elongated and enlarged to give rise to problems such as construction cost and spaces and in operation which will be explained
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hereinafter.
Namely, as the furnaces become elongated and enlarged, so-called "thermal inertia" of the furnaces increases to take much time for varying heat-treatment 05 conditions, and other various problems arise such as serpentine movements of steel strips and heat-buckle.
This invention intends to effectively solve the problems particularly in the last cooling stage among the vario-ws problems arising with the operation of furnaces at high speeds.
As cooling methods used for the continuous annealing treatment, there have been the gas-jet cooling, roll cooling and immersing cooling, which carry out the cooling by jetting cooled atmosphere gas against steel strips, winding steel strips abowt rolls in which a cooling medium passes, and immersing steel strips in a cooling bath, respectively. The cooling speed increases in order of the gas-jet cooling, roll cooling and immersing cooling.
In case of cooling steel strips in a cooling zone in a continuous annealing line from a recrystalliza-tion temperature to a temperature at which the~ do not oxidize in the air, it is generally considered that the most effective cooling is to use the gas-jet cooling and/or roll cooling on a high temperature side and the immersing cooling on a low temperature side.
Various immersing cooling methods have been iZ6660~
proposed. For example, Japanese Patent Application Publications Nos. 11,931/82 and 11,933/82 disclosed cooling methods wherein a plurality of cooling baths are used controlling supply of the cooling water or 05 spray cooling or mist cooling is combined with immersing cooling to cool steel strips effectively, while furthermore the temperature of the cooling water used for cooling is made as high as possible to use it advantageously as hot water.
The immersing cooling is usually used in cooling steel strips from temperatures of the order of 250-300C at which saturated solid solution carbon scarcely changes to -temperatures at which temper color does not occur in the air. When the cooling speeds in such an immersing treatment are too fast, it encounters a difficulty as to aging due to solid solution carbon.
Recently, non-aging material has been used such as very low-carbon added with Nb whose solid solution carbon is previously fixed by a third element. With such a non-aging material, any high cooling speed does not cause any problem. Therefore, it has been expected to increase the cooling speed in the final cooling in order to achieve higher speed operation, higher productivity and higher efficiency.
However, the immersing cooling methods as disclosed in the Japanese Patent Application Publications Nos. 11,931/82 and 11,933/82 include the folloving : `~
. . ` . .
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problems.
(l) It is necessary to supply the cooling water into the cooling bath in order to prevent the temperature rise of the cooling water. In this case, however, the 05 cooling water flows only in an upper layer in the bath but scarcely flows in a lower layer. As a result, when a hot steel strip is immersed into the cooling water, steam films occur on surfaces of the strip owing to the relatively lower temperature cooling water in the upper layer. As it is difficult to remove or break the steam films, the cooling efficiency has a limitation un-avoidably. In order to increase the cooling speed and efficiency, therefore, immersing cooling apparatus need to be large-sized to disadvantageously increase construction cost and spaces. Moreover, it is almost impossible to modify existing apparatuses for the purpose of increasing the cooling speed.
(2) As above described, the cooling water does not flow uniformly everywhere in the bath, so that the temperature distribution is not uniform, adversely affecting the steel strips to be cooled.
,....................... . :
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hereinafter.
Namely, as the furnaces become elongated and enlarged, so-called "thermal inertia" of the furnaces increases to take much time for varying heat-treatment 05 conditions, and other various problems arise such as serpentine movements of steel strips and heat-buckle.
This invention intends to effectively solve the problems particularly in the last cooling stage among the vario-ws problems arising with the operation of furnaces at high speeds.
As cooling methods used for the continuous annealing treatment, there have been the gas-jet cooling, roll cooling and immersing cooling, which carry out the cooling by jetting cooled atmosphere gas against steel strips, winding steel strips abowt rolls in which a cooling medium passes, and immersing steel strips in a cooling bath, respectively. The cooling speed increases in order of the gas-jet cooling, roll cooling and immersing cooling.
In case of cooling steel strips in a cooling zone in a continuous annealing line from a recrystalliza-tion temperature to a temperature at which the~ do not oxidize in the air, it is generally considered that the most effective cooling is to use the gas-jet cooling and/or roll cooling on a high temperature side and the immersing cooling on a low temperature side.
Various immersing cooling methods have been iZ6660~
proposed. For example, Japanese Patent Application Publications Nos. 11,931/82 and 11,933/82 disclosed cooling methods wherein a plurality of cooling baths are used controlling supply of the cooling water or 05 spray cooling or mist cooling is combined with immersing cooling to cool steel strips effectively, while furthermore the temperature of the cooling water used for cooling is made as high as possible to use it advantageously as hot water.
The immersing cooling is usually used in cooling steel strips from temperatures of the order of 250-300C at which saturated solid solution carbon scarcely changes to -temperatures at which temper color does not occur in the air. When the cooling speeds in such an immersing treatment are too fast, it encounters a difficulty as to aging due to solid solution carbon.
Recently, non-aging material has been used such as very low-carbon added with Nb whose solid solution carbon is previously fixed by a third element. With such a non-aging material, any high cooling speed does not cause any problem. Therefore, it has been expected to increase the cooling speed in the final cooling in order to achieve higher speed operation, higher productivity and higher efficiency.
However, the immersing cooling methods as disclosed in the Japanese Patent Application Publications Nos. 11,931/82 and 11,933/82 include the folloving : `~
. . ` . .
- . - ~- .. . .
. ~ .. ..
- . . ; , ~216660~
problems.
(l) It is necessary to supply the cooling water into the cooling bath in order to prevent the temperature rise of the cooling water. In this case, however, the 05 cooling water flows only in an upper layer in the bath but scarcely flows in a lower layer. As a result, when a hot steel strip is immersed into the cooling water, steam films occur on surfaces of the strip owing to the relatively lower temperature cooling water in the upper layer. As it is difficult to remove or break the steam films, the cooling efficiency has a limitation un-avoidably. In order to increase the cooling speed and efficiency, therefore, immersing cooling apparatus need to be large-sized to disadvantageously increase construction cost and spaces. Moreover, it is almost impossible to modify existing apparatuses for the purpose of increasing the cooling speed.
(2) As above described, the cooling water does not flow uniformly everywhere in the bath, so that the temperature distribution is not uniform, adversely affecting the steel strips to be cooled.
(3) In case of using the cooling water exhausted from the immersing cooling bath as hot water, at least two immersing baths are needed which make the apparatus large-sized, and complicated controlling such as cascade controlling is required.
Fig. l illustrates variations in heat transfer . .
.
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.
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~ ~ 6 6 ~ ~
coefficient when steel strips are cooled in the mannerof the prior art. The ordinate indicates the heat transfer coefficient and the abscissa denotes temperature difference between the steel strips and the cooling 05 water. Black points and black triangular points indicate data when the steel strips are fed in parallel directions and vertical directions relative to surfaces of the cooling water.
Within the range in which the temperature 0 difference between the strips and cooling water is small~ the heat transfer coefficient increases as the tempera-ture difference increases, because steam films scarcely occur on the surfaces of the strips. As the temperature difference further increases, steam films occur violently to separate the cooling water and steel strips by thick steam films which would adversely affect the cooling effect. This tendency is acute in the zone where the temperature difference is larger.
As a result, the heat transfer coefficient is lowered as shown in the right hand of Fig. l.
As seen from Fig. l, the heat transfer coefficient in case of the horizontal feeding of the strips is somewhat larger than that of the vertical feeding. It is considered that the steam escapes upward easier in the latter case than in the former case.
There is a~ upper limitation of the heat : - .. :
:. . ; ; . :
" - - "
.: . .... . .
," ., 1 ~ 6~ ~
transfer coefficient, at the most 5,000 Kcal/m2 h C in the cooling methods of the prior art.
It is an object of the invention to provide a method and appara-tus for cooling steel strips, which 05 eliminate all the disadvantages of the prior art and carry out the cooling treatment of steel strips with high efficiency.
In order to achieve this object, according to the invention said cooling liquid is forced to f]ow as steady flows along both surfaces of a steel strip in directions opposite to moving directions of the steel strips.
According to the invention, the apparatus for cooling steel strips by means of a cooling liquid, comprises flow rectifier plates in opposition -to both surfaces of a steel strip to form flow passages between the steel strip and the flow rectifier plates for forcing the cooling liquid through said flow passages, at least one cooling liquid supply port on a downsteam side of the moving steel strip and at least one cooling liquid exhaust port on an upstream side of the moving steel strip.
It is another object of the invention to provide a method and apparatus for cooling steel strips, which control temperatures of cooled steel strips at an exit to alway stably cool the steel strips to temperatures of a predetermined range without being ~ . ~ : ,- -~2~ii60~
affected by the normally expected factors such as amount of steel strips to be cooled, cooling water temperature and the like.
In order to achieve this object 3 according to 05 the invention, part of the cooling liquid used for cooling the steel strip is mixed with fresh cooling liquid to control temperature of cooling liquid to be used for cooling by adjusting a mixing ratio of -the used and fresh cooling liquids, thereby keeping temperature of the cooled steel strip within a pre-determined target temperature range.
To carrying out this feature, the apparatus according to the invention comprises a control system which comprises a thermometer, a flow adjusting valve and a flow meter respectively for the cooling water exhausted from the flow passages, a thermometer, a flow adjusting valve and a flow meter respectively for the cooling water newly supplied to the flow passage, a thermometer for detecting temperature of the steel strip leaving the flow passages, an arithmetic unit for calculating amounts of the exhaust and new cooling waters to be mixed, fIow controllers for con-trolling the flow adjusting valves in response to signals from the arithmetic unit, and a mixer for mixing the exhaust and new cooling waters through the flow adjusting valves.
In order that the invention may be more .. ........ .. . . . .
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.
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clearly understood, preferred embodiments will be described, by way of example, with reference to the accompanying drawings.
Fig. 1 is a graph illustrating a relationship 05 between heat transfer coefficient and temperature difference between steel strip and cooling water in immersing cooling according to the prior art;
Fig. 2 is a schematic perspective view illustrating the principle of cooling according to the invention;
Fig. 3 is a graph illustrating a relation between relative speed vr cooling water to steel strips and heat transfer coefficient ~;
Fig. ~ is a sectional view illustrating -a cooling apparatus according to the invention;
Fig. 5 is a perspective view of the apparatus shown in Fig. 4;
Figs. 6, 7 and 8 are schematic views illustrat-ing other embodiments of the invention;
Fig. 9 is a schematic view illustrating another embodiment of the invention;
Fig. 10 is a sectional view of a principal part of the apparatus shown in Fig. 9;
Fig. 11 is a graph illustrating a relation between cooling water temperature at entry and steel strip temperature at water cooling jacket exit with constant amount of steel strips;
g ... .
,.................. . ~ , . ~
:, :. .. .-.. : , .
- ~ , ~ .......... , Fig. 12 is a graph illustrating a relation between amount of steel strips and steel strip tempera-ture at water cooling jacket exit with cooling water temperature at entry being substantially constant;
05 Fig. 13 is a schematic view illustrating the cooling apparatus with a control system for maintaining the cooled steel strip temperature according to the inventlon;
Fig. 14 is a flow chart for the control system shown in Fig. 13;
Fig. 15 is a graph illustrating a relation between amount of steel strips and steel strip tempera-ture at water cooling jacket exit when cooled steel strip temperature is controlled according to the invention; and Fig. 16 is a graph illustrating a relation between amount of steel strips and steel strip tempera-ture at water cooling jacket exit when cooled steel strip temperature is controlled in actual operation according to the invention.
Fig. 2 illustrates symbolically the cooling method according to the invention wherein a steel strip S is raised upward. A cooling water W conditioned in a steady flow is supplied onto one side of tXe steel strip S. The cooling water W is turned downward at a location where it is in contact with the strip to flow in a direction opposite to a moving direction of ' ~_ .
:
, the strip.
As above described, the cooling water as a whole is forced to flow opposing to the movement of the steel strip S, thereby eliminating any staying of the cooling water which would occur in the prior art cooling method and rapidly removing or breaking steam films produced on the surfaces of the steel strip.
Accordingly, high efficiency cooling of the steel strip can be accomplished.
Assuming that the moving speed of the steel strip S is vS(m/s), the flowing speed of the cooling water is vW(m/s), and the downward direction is positive, the relative speed vr(m/s) of the cooling water W with respect to the steel strip S is indicated by the following equation.
Vr ~ Vw ~ VS (1) The inventors investigated the relation between such relative speed vr and heat transfer coefficient ~ (Kcal/m2 h C). Results of the investiga-tion are shown in Fig. 3. As seen from Fig. 3, the heat transfer coefficient ~ becomes larger in proportion to the relative speed vr. It has been found that the relation therebetween is approximately indicated by an equation ~2).
. ~
- - , .. . . .
- , . . . .
,: :
.
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~6~8~
~ = 5600 vr0'68 -- (2) In this case, when the relative speed vr is for example 10 m/s, the heat transfer coefficient ~ is 26,800 Kcal/m2 h C.
Referring back to Fig. 3, the heat transfer coefficient is at the most 5,000 Kcal/m2 h C in the cooling method of the prior art which is only less than a fraction of those in the present invention.
Fig. 4 illustrates in section a preferred embodiment of the invention whose principal part is shown in the perspective view of Fig. 5. Flow rectifier plates la and lb are arranged on both side of and in parallel with a steel strip S to form a cooling water jacket for introducing a cooling water along both surfaces of the steel strip under rectified or steady condition. Sealing rolls 2a, 2b and 3a and 3b serve to prevent the cooling water from escaping at front and rear ends of the flow rectifier plates. Reference numeral 4b denotes sealing plates provided on both sides of the rectifier plates. These sealing plates are jointed to form sealings at the sides of the rectifier plates, which prevent the cooling water from escaping at the sides of the rectifier plates and at the same time serve -to position the rectifier plates in assembling.
The rectifier plates are provided with :
-:~- ~ :. . . - -- ~Z66~i0~
cooling water inlets 5a and 5b and cooling water outlets 6a and 6b. Pressure pumps 7a and 7b supply the cooling water into the water cooling jacket formed by the rectifier plates. Deflector rolls 8 and 9 serve to 05 turn the moving direction of the steel strip S.
The cooling water introduced through the inlets 5a and 5b into the jacket formed by the rectifier plates flows in clearances or flow passages formed by the steel strip S and the flow rectifier plates la and 0 lb in directions opposite to the moving direction of the strip S and leaves through the outlets 6a and 6b provided at the other end of the jacket. In this manner, the effective cooling is achieved by forcing the cooling water through the relatively narrow clearances between the steel strip S and the fl.ow rectifier plates la and lb.
Figs. 6-8 illustrate modifications of the cooling apparatus according to the invention. The apparatus shown in Fig. 6 comprises three sets of flow rectifier plates along the moving line of the steel strip S. Apparatuses shown in Figs. 7 and 8 comprlse flow rectifier plates arranged in U and W shapes, respectively.
Final cooling of steel strips was effected using the cooling apparatus shown in Fig. 4 under the following conditions.
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Dimension of steel strip Thickness: 0.3 mm, Widthness: 900 mm Treated strip 60 Tfh Temperature of strip at commencement of cooling 150~C
Temperature of supplied cooling water 30C
Temperature of strip after cooled 60C
Thickness of cooling water flow passage about 6 mm The cooling water used for the above treatment was approximately 40 T/h. The temperature of the cooling water on the exit side was about 70C.
The steel strips were uniformly cooled in their width direction by the above cooling trea-tment.
Ununiform cooling and troubles caused by steam films were completely prevented.
According to the method of the prior art, cooling water of about 60 T/h was required for treating the same amount of steel strips as the above. Therefore, considerable saving of cooling water was accomplished according to the invention.
As can be seen from the above description, according to the invention steel strips are cooled with remarkably high efficiency in comparison with the prior art. Accordingly, the treating faculty in the continuous annealing treatment is considerably increased.
Moreover, the invention can provide a small-sized ... . ...
~ ~ . . .. .. .
~ ~ 6 cooling apparatus.
Referring to Fig. 9 illustrating another embodiment of the invention, if a water cooling jacket is formed in a ~-shape, a leg portion 31c of the U-shaped jacket into which a steel strip is introduced tends to obstruct the flow of the cooling water. In order to obtain a large cooling faculty, therefore, it is required -to consider the resistance of the leg portion 31c to the water flow. This resistance ~h can be calculated by the following equation according to the theory of weir.
Qh=( 3Q ) xlO3=683X(~)/ ... (3) 2xCxBx~g where ~h is difference in water head (mm), Q is flow rate (m3/s), C is coefficient of resistance (-0.6), B is width of jacket (width of weir) and g is accelera-tion of gravity.
Accordingly, the cooling water flows smoothly without obstructing the cooling effect, if the dif-ference h in level between surfaces of water in the legs 31a and 31c is determined to fulfil the following equation.
h > 683 x (Q)~ ... (4) :_i ,: .. ~ . .: ~ - , . - - -.. . . .. ....
.. ..
~26~6~
In the present invention, the clearances between the steel strip and the flow rectifier plates are very small, so that the pressure loss tends to be large. Accordingly, it is required to increase the 05 capacity of the cooling water supply pumps and power required for driving the pumps. In order to solve this problem, nozzles 36 are preferably provided for assisting the flow of cooling water as shown in Figs. 9 and 10.
As shown in Fig. 10, slit nozzles 36 are arranged in o the cooling jacket in the moving direction of the strip or somewhat inclined to the strip for jettin~g cooling water, which will compensate for the pressure loss due to the cooling water jacket. The nozzles 36 are supplied with cooling water through p,iping 37 by means of a supply pump 8. Although the nozzles 36 are arranged one on each side of the steel strip, a plurality of nozzles may be provided on each side of the strip.
Moreover, the steel strip between deflector rolls 32 in the horizontal portion 31b of the water cooling jacket tends to deform in catenary to cause difference in cooling effect between upper and lower sides of the strip. In this case, it is considered to increase the tensile force acting upon the strip to reduce the catenary deformation of the strip. However, such a tensile force has a limitation because too high tensile force causes breakage of the strip. In order to prevent this, it is effective to incline the horizontal ~. ., ~ , ... .- . .. .
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portion of the cooling water jacket as shown in Fig. 9.
It is preferable to locate the end of the horizontal portion 31b on the side of the leg 31a higher than the other end on the side of the leg 31b in consideration 05 of the flowing direction of the cooling water.
According to the above embodiments, steel strips can be cooled with higher efficiency in comparison with the prior art, thereby enabling the treating capacity of the continuous annealing to be remarkably improved.
In the above embodiments, however, the temperatwre of steel strips subjected to the cooling treatment is sometimes changed out of a predetermined temperature with variation in amount or weight of steel lS strips to be treated and with variation in supplied cooling water temperature, for example, due to seasonal variation.
Fig. 11 illustrates the relation between the supplied cooling water temperature and the temperature of cooled steel strips in case of the amount or weight of the steel strips 40 T/h passed through the cooling apparatus. As seen from Fig. 11, the -temperature of the cooled steel strips becomes out of the predetermined temperature range when the supplied cooling water temperature is too high or low.
Fig. 12 illustrates the result of investigating the relation between the amount or weight of steel . , .... ,. i ;- .
'~Z 6 ~
strips and the temperature of cooled steel strips in two cases of the cooling water temperature of 40C and 30C. It is clearly evident that as the amount of the steel strips increases, the temperature of the cooled 05 steel strips becomes higher and frequently out of the predetermined temperature range.
Following embodiments have for their objects to provide a method of controlling temperatures of cooled steel strips at an exit of the cooling apparatus o to always stably cool the steel strips to temperatures within a predetermined range without being affected by the normally expected factors such as amount of steel strips to be cooled, cooling water temperature and the like.
Fig. 13 schematically illustrates a control system together with a cooling apparatus with a cooling jacket. Flow rectifier plates lla and llb form a water cooling jacket 11 for forcedly introducing a cooling water along both surfaces of steel strips under a steady condition. Deflector rolls 12 turn the steel strip in the water cooling jacket 11 which is supplied with the cooling water through a cooling water supply pipe 13.
A reservoir 14 for storing the used cooling water is provided with a pump 15.
With the cooling apparatus constructed as above described, the cooling water is introduced into the water cooling jacket at a supply port provided : - . : . - - ....................... .. . .
. . - ................... . , .-. .
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~ ~ 6 ~ 6~ ~
on a downstream side of a moving passage of the steel strip S and is forced through the water cooling jacket 11 in a direction opposite to a moving direction of the steel strip during which the cooling water cools the 05 steel strip with high efficiency until the cooling water leaves an exhaust port. According to the embodiment, a part of the cooling water exhausted from the apparatus is circulated to use again for adjusting the temperature of the cooling water.
0 The cooling system comprises a retwrn pipe 16 for circulating the exhausted cooling water, a thermo-meter 17 for detecting the temperature of the exhausted cooling water, a flow adjusting valve 18 for the circulating water, a flow meter 19 for the circulating water, a fresh cooling water supply pipe 20 including a thermometer 21, a flow adjusting valve 22 and a flow meter 23 Eor the fresh cooling water, and a thermometer 2~ for detecting the temperature of steel strips leaving the cooling apparatus.
An arithmetic unit 25 calculates amounts of the circulating and fresh cooling waters to be mixed with each other to obtain cooling water at a pre-determined temperature on the basis of data detected by the respective detectors. The calculated results are inputted into flow controllers 26 and 27 whose output adjust openings of the flow adjusting valves 18 and 22, respectively. In this manner, the circulating and ~ , -': ~
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fresh waters adjusted in their required amounts are mixed in a mixer 28 to obtain cooling water at a predetermined temperature which is supplied through the supply pipe 13 into the cooling jacket 11. Reference numeral 29 denotes wringer rolls for removing water from steel strips leaving the water jacket.
I'he arithmetic operation in the arithmetic unit 25 will be explained hereinafter.
It is assumed that an allowable temperature range of a target cooling temperature Tso is as indicated by the following formula (5).
Tsol ~ Tso ~ TsO2 ,.. (5) An amount Q of cooling water to be supplied is indicated by amounts QC and QN of the circulating and fresh cooling waters as follows.
Q QC QN - ( ) There is a relation (7) between a set cooling water temperature Tw, circulating water temperature TWc and fresh cooling water temperature TWN.
':_ .~2666~Z
, _ Tw TWN rwc Tw Qc QN Twc-TWN Twc T~N
Namely, (TW-TwN)QN = (TWc-Tw)Qc From the equa-tions (6) and (7), valwes of Qc and QN are calculated.
Q = w lWN Q . . . (8) wc W2J
QN T ~ T ~ Q ( 9 ) First, whether the steel strip temperature T~o~ detected b~ the thermometer 24 is in the range of the equation (5) is judged. When it fulfills the equation (5), values of QC and QN are calculated on the basis of the detected temperature TWN and TWc by means of the equations (8) and (9).
On the other hand, if the steel s-trip temperature Tso, is above an upper limit, the set cooling water temperature Tw is lowered by a constant value.
;
: T = T - a ~,, (10) ' . ..... : - .- . ~
666~Z
On the contrary, if the steel strip temperature Tso, is below a lower limit, the set cooling water temperature Tw is raised by a constant value.
Tw = Tw + a ... (11) Next, amounts of circula-ting and fresh cooling water Qc and`QN are calculated on the basis of a newly set water temperature Tw by the use of the equations (8) and (9). In this case, the water temperatures TWc and TWN detected by the thermometers 17 and 21 are used.
The above operation is summarized as a flow chart shown in Fig. 14.
Fig. 15 illustrates the relation between the steel strip temperature at exit and amount or weight of steel strips when the cooling water temperature is controlled in the manner above described.
Steel strips were cooled by the use of the cooling apparatus and the control system shown in Fig. 13 under the following conditions.
Dimension of steel strips: 1 mm thickness, 2000 mm width Amount of cooling water : 13.2 T/h (Fresh cooling water: 3.3 T/h, Circulating cooling water: 9.9 T/h) :
:,~ . . .. .
- ;12~
Cooling water temperature: ~Fresh cooling water: 10C, Circulating cooling water: 50C) Target temperature after cooled : 50-60C
Initial amount of steel strips : 20 T/h Under the above conditions, the amount or weight of the steel strips to be passed was progressively increased. When the amount became 40 T/h, the tempera-ture of the steel strips at the exit was about to exceed the upper limit of the target temperature 6QC.
The ratio of the fresh cooling water to the circulating water was changed to 7.1 T/h to 6.1 T/h to lower the cooling water temperature to 30C. As a result, the temperature of the cooled steel strips lowered to 50C.
The cooling operation was continued. However, when the amount of steel strips became 65 T/h, there was again a tendency of the cooled steel strip tempera-ture to exceed 60C. The ratio of the fresh cooling water to the circulating water was changed to 11 T/h to 2.2 T~h to lower the cooling water temperature to 20C.
As a result, the cooled steel strip temperature lowered to 50C. Thereafter, the cooled steel strip temperature did not exceed 60C even when the amount of steel strips was increased to 80 T/h. Even when the amount of steel strips was changed from 20 T/h to 80 T/h, the cooled steel strip temperature at the exit was kept ... . .
. .
:: , . .. ~ . , : ., ~LZ6~i60~
within the target temperature within 50-60C.
According to the invention, the temperature of cooled steel strips in cooling treatment in continuous annealing line can be kept in a predetermined target Os temperature range without being affected by varying factors such as variation in amount of steel strips.
It is further understood by those skilled in the art that the foregoing description is that of preferred embodiments of the disclosed method and apparatus and that various changes and modifications may be made in the invention without departing from the spirit and scope thereof.
- ., ., ,:, , ~ :
,, , -
Fig. l illustrates variations in heat transfer . .
.
:,., , :-~, .
.
.. ~ ,.
~ ~ 6 6 ~ ~
coefficient when steel strips are cooled in the mannerof the prior art. The ordinate indicates the heat transfer coefficient and the abscissa denotes temperature difference between the steel strips and the cooling 05 water. Black points and black triangular points indicate data when the steel strips are fed in parallel directions and vertical directions relative to surfaces of the cooling water.
Within the range in which the temperature 0 difference between the strips and cooling water is small~ the heat transfer coefficient increases as the tempera-ture difference increases, because steam films scarcely occur on the surfaces of the strips. As the temperature difference further increases, steam films occur violently to separate the cooling water and steel strips by thick steam films which would adversely affect the cooling effect. This tendency is acute in the zone where the temperature difference is larger.
As a result, the heat transfer coefficient is lowered as shown in the right hand of Fig. l.
As seen from Fig. l, the heat transfer coefficient in case of the horizontal feeding of the strips is somewhat larger than that of the vertical feeding. It is considered that the steam escapes upward easier in the latter case than in the former case.
There is a~ upper limitation of the heat : - .. :
:. . ; ; . :
" - - "
.: . .... . .
," ., 1 ~ 6~ ~
transfer coefficient, at the most 5,000 Kcal/m2 h C in the cooling methods of the prior art.
It is an object of the invention to provide a method and appara-tus for cooling steel strips, which 05 eliminate all the disadvantages of the prior art and carry out the cooling treatment of steel strips with high efficiency.
In order to achieve this object, according to the invention said cooling liquid is forced to f]ow as steady flows along both surfaces of a steel strip in directions opposite to moving directions of the steel strips.
According to the invention, the apparatus for cooling steel strips by means of a cooling liquid, comprises flow rectifier plates in opposition -to both surfaces of a steel strip to form flow passages between the steel strip and the flow rectifier plates for forcing the cooling liquid through said flow passages, at least one cooling liquid supply port on a downsteam side of the moving steel strip and at least one cooling liquid exhaust port on an upstream side of the moving steel strip.
It is another object of the invention to provide a method and apparatus for cooling steel strips, which control temperatures of cooled steel strips at an exit to alway stably cool the steel strips to temperatures of a predetermined range without being ~ . ~ : ,- -~2~ii60~
affected by the normally expected factors such as amount of steel strips to be cooled, cooling water temperature and the like.
In order to achieve this object 3 according to 05 the invention, part of the cooling liquid used for cooling the steel strip is mixed with fresh cooling liquid to control temperature of cooling liquid to be used for cooling by adjusting a mixing ratio of -the used and fresh cooling liquids, thereby keeping temperature of the cooled steel strip within a pre-determined target temperature range.
To carrying out this feature, the apparatus according to the invention comprises a control system which comprises a thermometer, a flow adjusting valve and a flow meter respectively for the cooling water exhausted from the flow passages, a thermometer, a flow adjusting valve and a flow meter respectively for the cooling water newly supplied to the flow passage, a thermometer for detecting temperature of the steel strip leaving the flow passages, an arithmetic unit for calculating amounts of the exhaust and new cooling waters to be mixed, fIow controllers for con-trolling the flow adjusting valves in response to signals from the arithmetic unit, and a mixer for mixing the exhaust and new cooling waters through the flow adjusting valves.
In order that the invention may be more .. ........ .. . . . .
: -- - ~ ,. - -- ~.; --- : ... . .
.
.
~ 2 ~ Z
clearly understood, preferred embodiments will be described, by way of example, with reference to the accompanying drawings.
Fig. 1 is a graph illustrating a relationship 05 between heat transfer coefficient and temperature difference between steel strip and cooling water in immersing cooling according to the prior art;
Fig. 2 is a schematic perspective view illustrating the principle of cooling according to the invention;
Fig. 3 is a graph illustrating a relation between relative speed vr cooling water to steel strips and heat transfer coefficient ~;
Fig. ~ is a sectional view illustrating -a cooling apparatus according to the invention;
Fig. 5 is a perspective view of the apparatus shown in Fig. 4;
Figs. 6, 7 and 8 are schematic views illustrat-ing other embodiments of the invention;
Fig. 9 is a schematic view illustrating another embodiment of the invention;
Fig. 10 is a sectional view of a principal part of the apparatus shown in Fig. 9;
Fig. 11 is a graph illustrating a relation between cooling water temperature at entry and steel strip temperature at water cooling jacket exit with constant amount of steel strips;
g ... .
,.................. . ~ , . ~
:, :. .. .-.. : , .
- ~ , ~ .......... , Fig. 12 is a graph illustrating a relation between amount of steel strips and steel strip tempera-ture at water cooling jacket exit with cooling water temperature at entry being substantially constant;
05 Fig. 13 is a schematic view illustrating the cooling apparatus with a control system for maintaining the cooled steel strip temperature according to the inventlon;
Fig. 14 is a flow chart for the control system shown in Fig. 13;
Fig. 15 is a graph illustrating a relation between amount of steel strips and steel strip tempera-ture at water cooling jacket exit when cooled steel strip temperature is controlled according to the invention; and Fig. 16 is a graph illustrating a relation between amount of steel strips and steel strip tempera-ture at water cooling jacket exit when cooled steel strip temperature is controlled in actual operation according to the invention.
Fig. 2 illustrates symbolically the cooling method according to the invention wherein a steel strip S is raised upward. A cooling water W conditioned in a steady flow is supplied onto one side of tXe steel strip S. The cooling water W is turned downward at a location where it is in contact with the strip to flow in a direction opposite to a moving direction of ' ~_ .
:
, the strip.
As above described, the cooling water as a whole is forced to flow opposing to the movement of the steel strip S, thereby eliminating any staying of the cooling water which would occur in the prior art cooling method and rapidly removing or breaking steam films produced on the surfaces of the steel strip.
Accordingly, high efficiency cooling of the steel strip can be accomplished.
Assuming that the moving speed of the steel strip S is vS(m/s), the flowing speed of the cooling water is vW(m/s), and the downward direction is positive, the relative speed vr(m/s) of the cooling water W with respect to the steel strip S is indicated by the following equation.
Vr ~ Vw ~ VS (1) The inventors investigated the relation between such relative speed vr and heat transfer coefficient ~ (Kcal/m2 h C). Results of the investiga-tion are shown in Fig. 3. As seen from Fig. 3, the heat transfer coefficient ~ becomes larger in proportion to the relative speed vr. It has been found that the relation therebetween is approximately indicated by an equation ~2).
. ~
- - , .. . . .
- , . . . .
,: :
.
.. .
.. . ..
~6~8~
~ = 5600 vr0'68 -- (2) In this case, when the relative speed vr is for example 10 m/s, the heat transfer coefficient ~ is 26,800 Kcal/m2 h C.
Referring back to Fig. 3, the heat transfer coefficient is at the most 5,000 Kcal/m2 h C in the cooling method of the prior art which is only less than a fraction of those in the present invention.
Fig. 4 illustrates in section a preferred embodiment of the invention whose principal part is shown in the perspective view of Fig. 5. Flow rectifier plates la and lb are arranged on both side of and in parallel with a steel strip S to form a cooling water jacket for introducing a cooling water along both surfaces of the steel strip under rectified or steady condition. Sealing rolls 2a, 2b and 3a and 3b serve to prevent the cooling water from escaping at front and rear ends of the flow rectifier plates. Reference numeral 4b denotes sealing plates provided on both sides of the rectifier plates. These sealing plates are jointed to form sealings at the sides of the rectifier plates, which prevent the cooling water from escaping at the sides of the rectifier plates and at the same time serve -to position the rectifier plates in assembling.
The rectifier plates are provided with :
-:~- ~ :. . . - -- ~Z66~i0~
cooling water inlets 5a and 5b and cooling water outlets 6a and 6b. Pressure pumps 7a and 7b supply the cooling water into the water cooling jacket formed by the rectifier plates. Deflector rolls 8 and 9 serve to 05 turn the moving direction of the steel strip S.
The cooling water introduced through the inlets 5a and 5b into the jacket formed by the rectifier plates flows in clearances or flow passages formed by the steel strip S and the flow rectifier plates la and 0 lb in directions opposite to the moving direction of the strip S and leaves through the outlets 6a and 6b provided at the other end of the jacket. In this manner, the effective cooling is achieved by forcing the cooling water through the relatively narrow clearances between the steel strip S and the fl.ow rectifier plates la and lb.
Figs. 6-8 illustrate modifications of the cooling apparatus according to the invention. The apparatus shown in Fig. 6 comprises three sets of flow rectifier plates along the moving line of the steel strip S. Apparatuses shown in Figs. 7 and 8 comprlse flow rectifier plates arranged in U and W shapes, respectively.
Final cooling of steel strips was effected using the cooling apparatus shown in Fig. 4 under the following conditions.
. ~
, . . , ,. - -~ ~ ,- .
, - , :.,... , :- , lZ6~
Dimension of steel strip Thickness: 0.3 mm, Widthness: 900 mm Treated strip 60 Tfh Temperature of strip at commencement of cooling 150~C
Temperature of supplied cooling water 30C
Temperature of strip after cooled 60C
Thickness of cooling water flow passage about 6 mm The cooling water used for the above treatment was approximately 40 T/h. The temperature of the cooling water on the exit side was about 70C.
The steel strips were uniformly cooled in their width direction by the above cooling trea-tment.
Ununiform cooling and troubles caused by steam films were completely prevented.
According to the method of the prior art, cooling water of about 60 T/h was required for treating the same amount of steel strips as the above. Therefore, considerable saving of cooling water was accomplished according to the invention.
As can be seen from the above description, according to the invention steel strips are cooled with remarkably high efficiency in comparison with the prior art. Accordingly, the treating faculty in the continuous annealing treatment is considerably increased.
Moreover, the invention can provide a small-sized ... . ...
~ ~ . . .. .. .
~ ~ 6 cooling apparatus.
Referring to Fig. 9 illustrating another embodiment of the invention, if a water cooling jacket is formed in a ~-shape, a leg portion 31c of the U-shaped jacket into which a steel strip is introduced tends to obstruct the flow of the cooling water. In order to obtain a large cooling faculty, therefore, it is required -to consider the resistance of the leg portion 31c to the water flow. This resistance ~h can be calculated by the following equation according to the theory of weir.
Qh=( 3Q ) xlO3=683X(~)/ ... (3) 2xCxBx~g where ~h is difference in water head (mm), Q is flow rate (m3/s), C is coefficient of resistance (-0.6), B is width of jacket (width of weir) and g is accelera-tion of gravity.
Accordingly, the cooling water flows smoothly without obstructing the cooling effect, if the dif-ference h in level between surfaces of water in the legs 31a and 31c is determined to fulfil the following equation.
h > 683 x (Q)~ ... (4) :_i ,: .. ~ . .: ~ - , . - - -.. . . .. ....
.. ..
~26~6~
In the present invention, the clearances between the steel strip and the flow rectifier plates are very small, so that the pressure loss tends to be large. Accordingly, it is required to increase the 05 capacity of the cooling water supply pumps and power required for driving the pumps. In order to solve this problem, nozzles 36 are preferably provided for assisting the flow of cooling water as shown in Figs. 9 and 10.
As shown in Fig. 10, slit nozzles 36 are arranged in o the cooling jacket in the moving direction of the strip or somewhat inclined to the strip for jettin~g cooling water, which will compensate for the pressure loss due to the cooling water jacket. The nozzles 36 are supplied with cooling water through p,iping 37 by means of a supply pump 8. Although the nozzles 36 are arranged one on each side of the steel strip, a plurality of nozzles may be provided on each side of the strip.
Moreover, the steel strip between deflector rolls 32 in the horizontal portion 31b of the water cooling jacket tends to deform in catenary to cause difference in cooling effect between upper and lower sides of the strip. In this case, it is considered to increase the tensile force acting upon the strip to reduce the catenary deformation of the strip. However, such a tensile force has a limitation because too high tensile force causes breakage of the strip. In order to prevent this, it is effective to incline the horizontal ~. ., ~ , ... .- . .. .
- - : : : -- ~ , , ,; :
" ~ ~ , , ,; ~ , -~ Z6 ~ 6~ ~
portion of the cooling water jacket as shown in Fig. 9.
It is preferable to locate the end of the horizontal portion 31b on the side of the leg 31a higher than the other end on the side of the leg 31b in consideration 05 of the flowing direction of the cooling water.
According to the above embodiments, steel strips can be cooled with higher efficiency in comparison with the prior art, thereby enabling the treating capacity of the continuous annealing to be remarkably improved.
In the above embodiments, however, the temperatwre of steel strips subjected to the cooling treatment is sometimes changed out of a predetermined temperature with variation in amount or weight of steel lS strips to be treated and with variation in supplied cooling water temperature, for example, due to seasonal variation.
Fig. 11 illustrates the relation between the supplied cooling water temperature and the temperature of cooled steel strips in case of the amount or weight of the steel strips 40 T/h passed through the cooling apparatus. As seen from Fig. 11, the -temperature of the cooled steel strips becomes out of the predetermined temperature range when the supplied cooling water temperature is too high or low.
Fig. 12 illustrates the result of investigating the relation between the amount or weight of steel . , .... ,. i ;- .
'~Z 6 ~
strips and the temperature of cooled steel strips in two cases of the cooling water temperature of 40C and 30C. It is clearly evident that as the amount of the steel strips increases, the temperature of the cooled 05 steel strips becomes higher and frequently out of the predetermined temperature range.
Following embodiments have for their objects to provide a method of controlling temperatures of cooled steel strips at an exit of the cooling apparatus o to always stably cool the steel strips to temperatures within a predetermined range without being affected by the normally expected factors such as amount of steel strips to be cooled, cooling water temperature and the like.
Fig. 13 schematically illustrates a control system together with a cooling apparatus with a cooling jacket. Flow rectifier plates lla and llb form a water cooling jacket 11 for forcedly introducing a cooling water along both surfaces of steel strips under a steady condition. Deflector rolls 12 turn the steel strip in the water cooling jacket 11 which is supplied with the cooling water through a cooling water supply pipe 13.
A reservoir 14 for storing the used cooling water is provided with a pump 15.
With the cooling apparatus constructed as above described, the cooling water is introduced into the water cooling jacket at a supply port provided : - . : . - - ....................... .. . .
. . - ................... . , .-. .
~, , . ~- ~ .. . .
~ ~ 6 ~ 6~ ~
on a downstream side of a moving passage of the steel strip S and is forced through the water cooling jacket 11 in a direction opposite to a moving direction of the steel strip during which the cooling water cools the 05 steel strip with high efficiency until the cooling water leaves an exhaust port. According to the embodiment, a part of the cooling water exhausted from the apparatus is circulated to use again for adjusting the temperature of the cooling water.
0 The cooling system comprises a retwrn pipe 16 for circulating the exhausted cooling water, a thermo-meter 17 for detecting the temperature of the exhausted cooling water, a flow adjusting valve 18 for the circulating water, a flow meter 19 for the circulating water, a fresh cooling water supply pipe 20 including a thermometer 21, a flow adjusting valve 22 and a flow meter 23 Eor the fresh cooling water, and a thermometer 2~ for detecting the temperature of steel strips leaving the cooling apparatus.
An arithmetic unit 25 calculates amounts of the circulating and fresh cooling waters to be mixed with each other to obtain cooling water at a pre-determined temperature on the basis of data detected by the respective detectors. The calculated results are inputted into flow controllers 26 and 27 whose output adjust openings of the flow adjusting valves 18 and 22, respectively. In this manner, the circulating and ~ , -': ~
~ ~6 ~
fresh waters adjusted in their required amounts are mixed in a mixer 28 to obtain cooling water at a predetermined temperature which is supplied through the supply pipe 13 into the cooling jacket 11. Reference numeral 29 denotes wringer rolls for removing water from steel strips leaving the water jacket.
I'he arithmetic operation in the arithmetic unit 25 will be explained hereinafter.
It is assumed that an allowable temperature range of a target cooling temperature Tso is as indicated by the following formula (5).
Tsol ~ Tso ~ TsO2 ,.. (5) An amount Q of cooling water to be supplied is indicated by amounts QC and QN of the circulating and fresh cooling waters as follows.
Q QC QN - ( ) There is a relation (7) between a set cooling water temperature Tw, circulating water temperature TWc and fresh cooling water temperature TWN.
':_ .~2666~Z
, _ Tw TWN rwc Tw Qc QN Twc-TWN Twc T~N
Namely, (TW-TwN)QN = (TWc-Tw)Qc From the equa-tions (6) and (7), valwes of Qc and QN are calculated.
Q = w lWN Q . . . (8) wc W2J
QN T ~ T ~ Q ( 9 ) First, whether the steel strip temperature T~o~ detected b~ the thermometer 24 is in the range of the equation (5) is judged. When it fulfills the equation (5), values of QC and QN are calculated on the basis of the detected temperature TWN and TWc by means of the equations (8) and (9).
On the other hand, if the steel s-trip temperature Tso, is above an upper limit, the set cooling water temperature Tw is lowered by a constant value.
;
: T = T - a ~,, (10) ' . ..... : - .- . ~
666~Z
On the contrary, if the steel strip temperature Tso, is below a lower limit, the set cooling water temperature Tw is raised by a constant value.
Tw = Tw + a ... (11) Next, amounts of circula-ting and fresh cooling water Qc and`QN are calculated on the basis of a newly set water temperature Tw by the use of the equations (8) and (9). In this case, the water temperatures TWc and TWN detected by the thermometers 17 and 21 are used.
The above operation is summarized as a flow chart shown in Fig. 14.
Fig. 15 illustrates the relation between the steel strip temperature at exit and amount or weight of steel strips when the cooling water temperature is controlled in the manner above described.
Steel strips were cooled by the use of the cooling apparatus and the control system shown in Fig. 13 under the following conditions.
Dimension of steel strips: 1 mm thickness, 2000 mm width Amount of cooling water : 13.2 T/h (Fresh cooling water: 3.3 T/h, Circulating cooling water: 9.9 T/h) :
:,~ . . .. .
- ;12~
Cooling water temperature: ~Fresh cooling water: 10C, Circulating cooling water: 50C) Target temperature after cooled : 50-60C
Initial amount of steel strips : 20 T/h Under the above conditions, the amount or weight of the steel strips to be passed was progressively increased. When the amount became 40 T/h, the tempera-ture of the steel strips at the exit was about to exceed the upper limit of the target temperature 6QC.
The ratio of the fresh cooling water to the circulating water was changed to 7.1 T/h to 6.1 T/h to lower the cooling water temperature to 30C. As a result, the temperature of the cooled steel strips lowered to 50C.
The cooling operation was continued. However, when the amount of steel strips became 65 T/h, there was again a tendency of the cooled steel strip tempera-ture to exceed 60C. The ratio of the fresh cooling water to the circulating water was changed to 11 T/h to 2.2 T~h to lower the cooling water temperature to 20C.
As a result, the cooled steel strip temperature lowered to 50C. Thereafter, the cooled steel strip temperature did not exceed 60C even when the amount of steel strips was increased to 80 T/h. Even when the amount of steel strips was changed from 20 T/h to 80 T/h, the cooled steel strip temperature at the exit was kept ... . .
. .
:: , . .. ~ . , : ., ~LZ6~i60~
within the target temperature within 50-60C.
According to the invention, the temperature of cooled steel strips in cooling treatment in continuous annealing line can be kept in a predetermined target Os temperature range without being affected by varying factors such as variation in amount of steel strips.
It is further understood by those skilled in the art that the foregoing description is that of preferred embodiments of the disclosed method and apparatus and that various changes and modifications may be made in the invention without departing from the spirit and scope thereof.
- ., ., ,:, , ~ :
,, , -
Claims (14)
1. A method of cooling steel strips by means of a cooling liquid in a continuous annealing line, wherein said cooling liquid is forced to flow as steady flows along both surfaces of a steel strip in directions opposite to moving directions of the steel strips.
2. A method as set forth in claim 1, wherein said steel strip is guided through a U-shaped passage in which the steel strip is cooled by the cooling liquid.
3. A method as set forth in claim 1, wherein said steel strip is guided through a W-shaped passage in which the steel strip is cooled by the cooling liquid.
4. A method as set forth in claim l, wherein part of the cooling liquid is jetted into the cooling liquid cooling and flowing along the surfaces of the steel strip.
5. A method as set forth in claim 1, wherein part of the cooling liquid used for cooling the steel strip is mixed with fresh cooling liquid to control temperature of cooling liquid to be used for cooling by adjusting a mixing ratio of the used and fresh cooling liquids, thereby keeping temperature of the cooled steel strip within a predetermined target temperature range.
6. A method as set forth in claim 1, wherein the steel strip is cooled in a final cooling stage in the continuous annealing line.
7. An apparatus for cooling steel strips by means of a cooling liquid, comprising flow rectifier plates in opposition to both surfaces of a steel strip to form flow passages between the steel strip and the flow rectifier plates for forcing the cooling liquid through said flow passages, at least one cooling liquid supply port on a downstream side of the moving steel strip and at least one cooling liquid exhaust port on an upstream side of the moving steel strip.
8. An apparatus for cooling steel strips as set forth in claim 7, wherein said flow rectifier plates are provided on both sides with sealing plates jointed thereto to prevent the cooling water from escaping at the sides of the rectifier plates.
9, An apparatus for cooling steel strips as set forth in claim 7, wherein said flow passages are formed in U-shaped passages.
10. An apparatus for cooling steel strips as set forth in claim 7, wherein said flow passages are formed in W-shaped passages.
11. An apparatus for cooling steel strips as set forth in claim 9, wherein a cooling liquid surface level on a side of the cooling liquid supply port is higher than that on a side of the cooling liquid exhaust port by a distance h calculated by the following formula where Q is flow rate (m3/s) of the cooling liquid in the flow passages and B is width of the flow passages.
12. An apparatus for cooling steel strips as set forth in claim 9, wherein a connecting portion for connecting two vertical portions of the U-shaped flow passages is inclined such that one end of the connecting portion on a side of the vertical portion having the cooling liquid supply port is higher than the other end of the connecting portion on a side of the vertical portion having the cooling liquid exhaust port.
13. An apparatus for cooling steel strips as set forth in claim 7, wherein at least one pair of cooling liquid jetting nozzles is provided one on each side of the steel strip in the flow passages, a jetting direction of each the cooling liquid jetting nozzle being directed in parallel with a moving direction of the steel strip or inclined toward the steel strip at some angles.
14. An apparatus for cooling steel strips as set forth in claim 7, wherein said apparatus comprises a control system which comprises a thermometer, a flow adjusting valve and a flow meter respectively for the cooling water exhausted from the flow passages, a thermometer, a flow adjusting valve and a flow meter respectively for the cooling water newly supplied to the flow passage, a thermometer for detecting temperature of the steel strip leaving the flow passages, an arithmetic unit for calculating amounts of the exhaust and new cooling waters to be mixed, flow controllers for controlling said flow adjusting valves in response to signals from the arithmetic unit, and a mixer for mixing the exhaust and new cooling waters through said flow adjusting valves.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60162909A JPS6223937A (en) | 1985-07-25 | 1985-07-25 | Method and apparatus for cooling steel strip in continuous annealing treatment |
| JP162,909/85 | 1985-07-25 | ||
| JP139,115/86 | 1986-06-17 | ||
| JP13911586A JPH0229732B2 (en) | 1986-06-17 | 1986-06-17 | RENZOKUSHODONRAINNIOKERUKOTAINOREIKYAKUSOCHISHUTSUGAWAITAONSEIGYOHOHO |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1266602A true CA1266602A (en) | 1990-03-13 |
Family
ID=26472021
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000514447A Expired - Lifetime CA1266602A (en) | 1985-07-25 | 1986-07-23 | Method and apparatus for cooling steel strips |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0210847A3 (en) |
| KR (1) | KR900006694B1 (en) |
| AU (1) | AU571786B2 (en) |
| BR (1) | BR8603527A (en) |
| CA (1) | CA1266602A (en) |
| ES (1) | ES2000758A6 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE10215118C1 (en) * | 2002-04-05 | 2003-06-12 | Rainer Menge | Device for cooling heat-treated wires comprises a cooling nozzle having a nozzle body in the form of a central part containing a wire feeding channel, the nozzle and coolant feeding channels and removing channels |
| EP1538228A1 (en) | 2003-12-01 | 2005-06-08 | R & D du groupe Cockerill-Sambre | Cooling process and device for a steel sheet |
| CN101660039B (en) * | 2008-08-25 | 2011-03-16 | 鞍钢股份有限公司 | Method for eliminating annealing punch marks of cold-rolled steel sheets |
| BE1020401A5 (en) * | 2012-09-19 | 2013-09-03 | Duvel Moortgat Nv | METHOD AND DEVICE FOR ADJUSTABLE SETTING THE TEMPERATURE OF A FERMENTING LIQUID. |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3000109A (en) * | 1957-12-31 | 1961-09-19 | James B Shaver | Cooling tunnel for hot sheet or strip |
| US3410734A (en) * | 1965-01-18 | 1968-11-12 | Inland Steel Co | Quench system |
| US3358980A (en) * | 1965-01-21 | 1967-12-19 | Inland Steel Co | Apparatus for quenching web material |
| FR2261816B1 (en) * | 1974-02-21 | 1976-12-03 | Pechiney Aluminium | |
| JPS5362713A (en) * | 1976-11-18 | 1978-06-05 | Nippon Kokan Kk <Nkk> | Method and apparatus for cooling steel belt |
| JPS5944367B2 (en) * | 1978-06-15 | 1984-10-29 | 日本鋼管株式会社 | Water quenching continuous annealing method |
| JPS5792141A (en) * | 1980-11-27 | 1982-06-08 | Kawasaki Steel Corp | Continuous hardening device for steel plate |
| FR2503187A1 (en) * | 1981-03-31 | 1982-10-08 | Cables De Lyon Geoffroy Delore | METHOD AND DEVICE FOR ANNEALING AND SCRAPING FOR EXTENDED METAL ELEMENTS INTO FINE OR SPECIAL STEELS |
| JPS61217531A (en) * | 1985-03-22 | 1986-09-27 | Kawasaki Steel Corp | Cooling method for steel strip |
| JPS61217530A (en) * | 1985-03-22 | 1986-09-27 | Kawasaki Steel Corp | Cooling method for steel plate in continuous heat treatment |
-
1986
- 1986-07-23 CA CA000514447A patent/CA1266602A/en not_active Expired - Lifetime
- 1986-07-24 AU AU60501/86A patent/AU571786B2/en not_active Ceased
- 1986-07-24 ES ES868600603A patent/ES2000758A6/en not_active Expired
- 1986-07-25 BR BR8603527A patent/BR8603527A/en not_active IP Right Cessation
- 1986-07-25 EP EP86305721A patent/EP0210847A3/en not_active Withdrawn
- 1986-07-25 KR KR1019860006082A patent/KR900006694B1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| BR8603527A (en) | 1987-03-04 |
| ES2000758A6 (en) | 1988-03-16 |
| KR900006694B1 (en) | 1990-09-17 |
| KR870001317A (en) | 1987-03-13 |
| AU571786B2 (en) | 1988-04-21 |
| EP0210847A3 (en) | 1989-05-10 |
| AU6050186A (en) | 1987-01-29 |
| EP0210847A2 (en) | 1987-02-04 |
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