FR2517039A1 - METHOD AND INSTALLATION FOR PERFORMING COOLING CONTROL OF SHEETS - Google Patents

Abstract

PROCEDURE FOR CONTROLLING THE COOLING OF A SHEET WITH A VIEW OF CONFIRMING IT A PREDETERMINED CRYSTALLINE STRUCTURE, FOLLOWING WHICH THE SHEET TO BE COOLED IS PASSED THROUGH AN ENCLOSURE CONTAINING A MASS OF COOLING FLUID REGULARLY RENEWED IN THIS COMMAND, CARRIED OUT THE FLOW RATE OF THE COOLING FLUID AS A FUNCTION OF THE ARRIVAL TEMPERATURE OF THIS FLUID, ACCORDING TO THE THICKNESS OF THE SHEET TO BE COOLED AND THE DESIRED COOLING SPEED.

Description

The present invention relates to a method for carrying out the

  controlled cooling of sheets to obtain a

  perfectly defined crystalline structure of the metal component.

  It also relates to an installation for the implementation of this process which includes a method of cooling the mills so as to achieve high cooling rates in order to treat sheets of significant thickness. However, this method and the machine for its implementation are described in the patent application No. 2,223,096. In this method, at the end of the not mine, the plate of heated t 61 is presented horizontally

  to the untree of an enclosure in which she is trained by a

  uniformly translational motion by means of rollers Simultaneously, a blade of constant height and high velocity flow circulates on both sides of the plate to dissipate the heat of

prison.

  Thus, each surface element of the metal is in contact with

  within the enclosure, with a regular fluid mass.

  The corresponding heat exchange between the plate e, the water is higher than the flow velocity

  water is more abundant, it is possible thanks to this process of extraction.

  re a thermal flow of o Wdr-e of 3 x 106 2 This value corresponds to

  At the cooling rate at the core of 30 C / s of a thick plate of 30 nim According to the studies and experiments made by the Applicant, the cooling rates achievable according to the process described in the aforementioned patent application, appear quite compatible to achieve, for example, the nmensensit quenching of a manganese carbon steel t3 containing about 0.17% carbon and 1/4%, deanganganese, with no other

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  alloying element It goes without saying that the application of this treatment L to steels containing small amounts of additions, for example, molybdenum, nickel or boron whose presence has the effect of increasing the quenchability , would produce equal martensitic structure. However, the process defined in the aforementioned patent application does not make it possible to obtain directly the desired final structure of a metal, for example a composition steel.

  In fact, the cooling operation is generally translated into

  by the martensitic quenching of the metal and a

  income, characterized for steel by a maintenance of a suitable duration

  at a temperature below 7 O C, shall succeed the

  However, the studies relating to the transfor-

  in cooling show that the cooling speed

  determine the structure of a steel of a given composition.

  Certain phases, in particular bainite, or phase mixing,

  finely grained nite and perlite, characterized by good

  mechanical properties of capacity and ductility can be

  in the case of suitable grades of steel.

  Thus, insofar as it would be possible to

  the speed of cooling of the sheet metal plates, the accelerated cooling at a chosen speed could be substituted for well-defined metal compositions, the quenching treatment and would directly produce the desired metal structures without practicing

additional income.

  The object of the invention is therefore to provide a method and a

  china cooling of the aforementioned type, for adjusting and controlling the cooling rate of the sheet metal plates according to values determined according to the

desired structures.

  For this purpose, the subject of the invention is a process

  to control the cooling of a sheet in order to confer

  rer a predetermined crystalline structure, according to which is passed through the sheet to be cooled through a chamber containing a mass of coolant regularly renewed,

  characterized in that the flow of cooling fluid is controlled

  dissement according to the arrival temperature of this fluid,

  depending on the thickness of the sheet to be cooled and the cooling rate

desired development.

  The invention also relates to an installation for implementing the method defined above, said installation comprising a machine composed of an enclosure comprising means for circulating a cooling fluid which

  moves roughly parallel to the sheet, a cooling tank

  , means for injecting the cooling fluid contained in the tank inside said enclosure and means for discharging the cooling fluid after its passage through the cooling chamber, characterized in that

  comprises means for controlling the flow of cooling fluid

  dissement inside the enclosure depending on the temperature

coolant.

  According to another characteristic the invention comprises

  means for regulating the temperature of the cooling fluid

introduced into the enclosure.

  According to yet another characteristic, the invention

  tion comprises means for regulating the pressure of the fluid at

inside the enclosure.

  Other features and advantages of the invention

  will appear in the course of the description which follows

  annexed drawings, given solely by way of example and in which FIG. 1 represents the installation for effecting the controlled cooling of the sheets; and FIG. 2 represents an embodiment of the control and regulation means according to the invention. The installation shown in FIG. 1 comprises a cooling machine 1, a cooling tank 2, and

  a control and regulating device 3.

  The cooling machine 1 is of the general type -

  This machine is made up of a series of support and guide rollers 4 to 8 8. In a general way, the essential elements of the machine, arranged symmetrically on both sides of the machine. other of the average plane of the sheet will be designated by the same numerals assigned of index a for the upper elements and

b for the lower elements.

  The machine comprises an envelope or enclosure

  9 extends between the guide rollers 10 to 10, a b a b and surrounds these rollers 11, 1, the flat walls 10, 10

  are almost parallel and are separated by a

  less than the thickness of the sheet, so as to delineate with this ab last two chambers or channels 12, 12 of thickness c Water circulation means comprise at least one supply conduit 13 ,, 14, 14 s extending for example over the entire length of the rollers 5, 7, 7 and at least one exhaust duct 15 ab 6 ab 15,1 16,16, 17,117 also extending over a 1, a ba b any the length of the rollers 4, 46, 6b and 8, 8

  The cooling tank 2 contains the cooling water

  dissement; on its flanks are provided openings 18,19 to allow the output of the cooling water to the machine 1 and the water inlet ports 20, 21 to recover

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  the water that comes back from the cooling machine.

  It also has on its upper part

an overflow orifice 22.

  The water outlet orifices 18 and 19 of the tray 2 abab are connected to the supply ducts 13, 13, 14 of the machine via ducts 23, 23 via feed pumps 24. 24 The water inlet orifices 20, 21 of the ababa tank 2 are connected to the discharge ducts 15 * 15 _ 16, 16, 17 baba 17 by conduits 25, 25 through electro-valves 26 b

  An electrovalve 27 mounted on the pipe 28 ensures the

cold water supply of the tank.

  The control and regulation device 3 consists essentially of a calculator which can be

  digital type, analog or hybrid, the latter type being -

  adapted to perform treatments on both sizes

digital and analog.

  The control and regulation device 3 represented is of hybrid type, it provides control and regulation of the flow rate of pumps 24} 24 and electro-valves

26 26 1 2

  26, 26 and 27 It is connected by its inputs I, I to a display board 29 of the set values R relating to the desired cooling rate and e relative to the thickness of the sheet

  entering the cooling machine The values of

  sign R and e are transmitted in a binary coded form to the inputs I and I of the device 3 The input I is connected to a sensor

0 4 5

  the atmospheric pressure P O The I and I transits put the control commands to the pumps 24 and 24 The input I receives, from a thermometric probe 32 arranged inside the

  Tray 2, the value of the coolant temperature.

  This temperature value is received in the form of a signal

  analog and in the form of a binary word of more than one bit.

  The outputs I 7 to I provide the respective commands of the

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  b a 10 solenoid valves 27, 26 and 26 Finally, the inlet I receives the value of the relative pressure P of the water at the inlet of the enclosure 9

  of the machine and transmitted by a pressure sensor 33.

  The details of embodiment of the control and control device 3 are shown in FIG. 2. This device comprises a member 34 for calculating the value of the heat flux Pb exchanged between the sheet T and the cooling water, a computing member 35. the speed of the cooling fluid necessary to cool the sheet under the desired conditions, a member 36 for controlling the flow rate of the pumps 24 and 24, a member 37 for regulating the temperature of water in the tank 2

  and a body 38 for regulating the pressure inside the body

girdle 9 cooling.

  The member 34 is constituted by a programmable read only memory which contains a table A 1 giving the values

  of the heat flux P corresponding to different values of

  sign R and e This table A 1 can be determined from a theoretical calculation taking into account the thickness c of the cooling water plate circulating above and below the sheet to be cooled, and the conditions thermal limits,

  in particular the heat flux exchanged on the surface of the sheet.

  These calculations involve the equations of heat, resulting in

  complicated formulas and it is preferable to

  the table A 1 directly from tests carried out on several thicknesses of sheet metal and for speeds of

different cooling.

  The member 35 is also constituted by a programmable read-only memory which contains a table A giving the values of the cooling rate corresponding to the different values of heat flux stored in the memory of the member 34 and at different values of the temperature of the water This table A 2 is determined from

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7-

  the relation which links the heat flux O exchanged, to the speed of

  of the cooling water which is given by the formula ç KW / mm 2 = "((V m / s) (o I" (6) is a coefficient which depends only on the temperature of the water of This formula has been obtained from tests which have made it possible to establish a relation between characteristic numbers.

  heat exchange and flow.

  The member 36 is also constituted by a programmable read-only memory which contains in memory a table A 3 giving

  the pump flow values according to the values of the

  cooling water read in the memory of -the organ 35. This table can easily be built to

  from the technical characteristics of the pumps:

  also holds a digital-to-analog converter, not

  felt, connected to the output of his memory, necessary to deliver the

  analog control signals for pumps 24a and 24b.

  The memory of the organ 34 is connected by its

1 2 -

  two addressing inputs to the inputs I and I of the device 3 and its output, on the one hand, to an address input of the memory of

  the member 35 and, on the other hand, at the input of a multiplication circuit 39.

  located in the regulating member 37 The memory of the member 35

  is connected on its second addressing input to input I of the device

  3 receiving the binary word transmitted by the thermometric probe 32.

  The output of the organ 35 is connected to the input of

  wise of the memory of the member 36 and the output of the member 36 is 4 5 s

  connected to the outputs I and I of the computer 3.

  The regulator 37 is constituted by the multiplication circuit with a constant q, potentiometers 40, 41 and 42 used respectively for the display of a constant p and the ranges + A t and t B for temperature regulation. the water contained in the tank 2 It also consists of summing circuits 43 and 44, a subtraction circuit 45,

  comparators 46 and 47 and a control organ 50 for the electri-

  The constants p and q are defined from the characteristics of the installation by the following formulas: e O o oc (VI) q> M m 5 ecb M dot m (VII) and PM bm o 15 represents the minimum temperature of industrial water o used as coolant

  it is the critical value of the temperature of the cooling water

c

  dissement corresponding to the vapor pressure p = p u 1.

  p being the atmospheric pressure and u 1 the height of the siphons formed by the upper evacuation ducts (15 a,

16 a, 17 a) of the machine.

  During the cooling operation the temperature

  cooling water must of course be understood

between these two values.

  M and t are determined from the formula (I) for the respective values of 9 and 4 and for corresponding speed values V of the water layer, given that the

  velocity V of the water slide must be greater than

  V to cool the cooling fluid

  This critical speed corresponds to a dynamic pressure

  that, expressed in water height, equal to the thickness of the tunnel.

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  The circuit 39 of multiplication by a

  aunt is constituted in known manner by a digital / analog converter composed of a network of resistance cells (R 2 R) in Ir whose power supply voltage is varied as a function of the value of the constant q. The summing circuit 43 is connected by

  an entrance at the exit of circuit 39 and by its other entrance to the cur-

potentiometer 40.

  The summing circuit 44 is connected by an input at the output of circuit 43 and by its other input at

  potentiometer slider 41 The subtraction circuit 45 is con-

  nected by an entrance at the exit of the cricuit 43 and by its other

  input to potentiometer slider 42.

  The comparator 46 has two inputs, one is

  connected to the input terminal I of the device 3 to receive the signal

  analogue signal transmitted by the thermometric probe 32 and the

  is connected to the output of the circuit 44 The comparator 47 is also

  two inputs, one is connected to the input terminal I of the dis-

  positive to receive the analog signal transmitted by the sound.

  32, the other is connected to the output of the circuit The outputs of the comparators 46 and 47 are connected to two

  respective inputs of the organ 50.

  The regulator 38 consists of the

  potentiometer 51, summation circuit 52 and comparator 53.

  The circuit 52 has two inputs one of which is connected to the terminal I

  of organ 3 and the other is connected to the potentiometer slider -

51.

2 5 1 7 0 3 9

  The comparator 53 also has two inputs, one is connected to the output of the circuit 52 and the other is connected to the input terminal I of the device 3 The output of the comparator 53

  is connected to output terminals I and I of device 3.

  Fig 2 also shows the devices

  display of setpoints R and e of the scoreboard 29.

  These devices consist of digital analogue encoders

  54 and 55, the parallel outputs of which are connected

  These I / O encoders may consist of simple switch registers

  whose state represents, for example, the decimal value coded in terms of

  The atmospheric pressure sensor 30 connected to the terminal I of the device 3 and the pressure sensor 33 connected to the terminal I 10 are also shown in FIG.

  The operation of the cooling system

  The operator has the manufacturer's data.

  which are the thickness e of the sheet and the cooling speed

  These two data are displayed on the switch registers.

  and 54 of the billboard 29 They are introduced on the borders

  I and I input numbers of the control and regulating device 3

  towards the addressing inputs of the memory of the organ 34.

  Input quantities e and R address the contents of an area of the memory of the calculator member 34 in which the corresponding magnitude δ) is found. The theoretical thermal flow exchanged between the sheet metal plate and the water cooling, following the

relation 1 A (R, e).

  The calculating member 35 determines the speed V = A (6 e) of the water blade flowing on the sheet metal plate,

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  it is a function of the heat flow previously calculated by the member 34, and the temperature in the tank 2 This calculation is made by addressing the memory of the member 34 by the binairxes e values and respectively transmitted by the body 34 and the temperature probe 32. When the speed V of the flow of water in the channels 12a, 12b is obtained from the member 35, the control member 36bb acts on the flow rate of the pumps 24 and 24 It is apparent from the foregoing that the control and regulating device 3 controls the flow rate of the pumps to achieve the cooling rate of the cooling water in the ducts 13 14a and 14b. desired according to

  setpoint data e = sheet thickness, R = speed of recovery

  coldness and t = temperature of the water contained in the tank 2.

  The regulating device 37 ensures the regulation

  the temperature of the water in the tank 2 The operating temperature relative to the cooling water is determined by the summation circuit 43 and the multiplication circuit by a constant 39 The circuit 39 delivers an output quantity q (

  which is proportional to the magnitude (of the heat flux

  between the sheet metal plate and the cooling water This large

  deur q çb is added to the above-mentioned constant p displayed in

  The output of the summator 43 thus delivers a signal of amplitude lf = q + p.

  The permitted limits of temperature variation f are

  on the potentiometers 41 and 42, the potentiometer 41 delivering

  a value + A and and the potentiometer 42 delivering a value -

  The value + A & is added to the operating temperature O f in the summing circuit 44 which outputs a value Of + 4 t This value O f + to θ is compared with the temperature of the water measured in the tank 2, by the comparator 46

  whose output controls the control member 50 of the electro-

  water supply valve 27 when the measured water temperature V is greater than the calculated value D f + té In a similar way the subtraction circuit 45 subtracts from the calculated value t, the value & transmitted by the potentiometer 42 The result obtained is compared with the value G of the water measured in the tank 2 using the comparator 47 to close the solenoid valve -27 when the temperature of the water measured is less than the calculated value The control circuit 38 makes it possible to act against the pressure losses occurring in the return circuit and which are due to the reduction of the injection rate of the cooling water by the pumps. The summing circuit 52 adds the value of the atmospheric pressure Po sensed by the pressure sensor 30 to a value t displayed on the potentiometer 51 and

  transmits the result of the Po + E summation to the entry of the

  rator 53 which compares this value with the pressure value P measu-

  by the pressure sensor 33 inside the enclosure of

  When the pressure P appears for the comparison

  In contrast, if the pressure P is equal to or smaller than the pressure Po + the comparator 53 controls the closing of the electrodes. valves of

  return 26 and 26, so as to increase the pressure P at the

  the cooling chamber.

  The set of temperature and pressure regulating devices which have just been described provide

the following advantages.

  * First of all, the temperature control device keeps the water in the tank at a constant temperature, which firstly makes it possible to maintain the heat flux exchanged between the sheet and the cooling water at a constant level and secondly , to keep at a constant level the tension of

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  a a vapor in the siphon formed by the exhaust ducts 16, 17 thus avoiding the defusing of the latter and the flow of water

by the ends of the machine.

  In the second place, the presence of the electro-valves 26a and 26b in each of the evacuation circuits, and whose opening is slaved to the flow rate of the feed pumps, makes it possible to avoid the effects of loss of pressure in the machine Le-gr action in the return circuit, maintaining the pressure at the rear of the enclosure slightly higher than the atmospheric pressure, makes it possible to avoid air intakes into the machine which would be detrimental to

its good functioning.

  The exemplary embodiment of the invention which has just been described has been given in a digital analog hybrid version of the control and regulation member 3.

  obvious that we could arrive at the same result with a calcula-

  programmed digital transmitter In this case it is sufficient to store the setpoint data e and R as well as the tables A 1, A 2 and A 3

  in the calculator memory and calculate the theoretical values

  heat flow 9 and flow velocity V, for example,

  corresponding programs.

  It should also be noted that most of the opera-

  described above could also be carried out

  In this case, the pumps could be controlled by reading the charts corresponding to the AL tables.

  A 2 and A 3 previously described.

Claims (12)

CLAIMS -   1 Method for controlling the cooling of a   sheet to give it a predetermined crystalline structure   born, according to which is passed through the sheet to cool through an enclosure containing a mass of coolant regularly renewed, characterized in that one controls   the flow rate of the coolant according to the temperature   the arrival of this fluid, depending on the thickness of the cooling plate   dir and the desired cooling rate.   Process according to Claim 1, characterized in   that we adjust the flow of the cooling fluid according to   tion of the theoretical heat flux exchanged between the sheet and the fluid.   Process according to any one of the claims   1 and 2, characterized in that a theoretical cooling water temperature is determined as a function of the calculated flow.   and the temperature of arrival of the cooling fluid is controlled   according to this theoretical cooling temperature. than calculated.   Process according to any one of the claims   preceding es, characterized in that one maintains the pressure at the ends of the enclosure to a value greater than the atmospheric pressure. Process according to Claim 1, characterized in that a theoretical heat flux exchanged between the sheet and the cooling fluid is calculated as a function of the thickness of the sheet and the desired cooling rate; a theoretical flow velocity of the fluid on the sheet is calculated as a function of the inlet temperature of the cooling fluid and the calculated heat flow; the flow rate of the cooling fluid is controlled as a function of the speed of the theoretical cooling fluid obtained;   a temperature of the cooling fluid is calculated   theoretically according to the theoretical heat flux obtained, the temperature of the fluid is regulated as a function of the   theoretical cooling temperature obtained.   Process according to Claim 5, characterized in that the pressure at the ends of the enclosure is regulated in such a way   to maintain it at a value higher than the atmospheric pressure   than. Plant for carrying out the process according to claim 1, comprising a machine (1) composed of   an enclosure having means (10, 10) for cir-   a cooling fluid that moves roughly   an extension to the sheet metal, a cooling tank (2), means   (13a, 13b 23a, 23b) for injecting the cooling fluid   held in the tank inside said enclosure and means a b a b (17,17 25 25) for discharging the cooling fluid   after passing through the cooling chamber,   in that it comprises means for controlling the de-   bit of coolant inside the enclosure in   depending on the temperature of the coolant.   8 Installation according to claim 8, characterized   in that it comprises means (37) for regulating the temperature   the temperature of the cooling fluid introduced into the chamber,   9 Installation according to any one of the claims   7 and 8, characterized in that it comprises means   (38) for regulating the fluid pressure at the ends of the girded.   Installation according to claim 7, characterized in that the control means (24 to 24) of the fluid flow   are connected to means of calculation (35,36) of the speed diécou-   coolant on the plate.   11 Apparatus according to claim 10, characterized in that the means for calculating the flow velocity   are constituted by a calculation unit (35) of the theoretical speed   that cooperating with a calculator (34) of the theoretical heat flow. 12 Installation according to claim 11, characterized in that the means for calculating the flow velocity consist of a calculator (35) of the theoretical velocity   cooperating with a calculator (34) of the theo- America.   13 Installation according to any one of the claims   7 to 12, characterized in that the means (37) for regulating the temperature of the cooling fluid consist of means for calculating (39, 43) the desired cooling temperature as a function of the heat flux calculated by the computing unit (34); a probe (32) for measuring the temperature of the cooling fluid entering said chamber;   a comparator (46, 47) of the temperature of   calculated by the calculating means (37,43) at the time   26 measured by the measuring probe 32 and, at least one solenoid valve (27) inserted in the   supply circuit (28) in cold water of said cooling tank   connected to the comparator (46, 47).   Installation according to any of the claims   cations 7 to 13, characterized in that the control means 2-51 703-9   pressure (38) of the fluid inside the enclosure are con- staked by   a first sensor (33) for measuring the pressure   sion at the ends of said enclosure (9); a second sensor (30) for measuring the atmospheric pressure; a comparator (53) connected to said sensors for   compare the pressure measured in the enclosure to the pressure   mospheric measured by the second sensor-; at least one electrovalve (26,26) inserted in   said means for discharging the fluid and controlled by the result of   the state of comparison made by said comparator (53) such that the solenoid valves are closed when the   pressure measured by the first sensor is lower or equal at atmospheric pressure.