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
  • 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
  • C21D11/00—Process control or regulation for heat treatments
  • C21D11/005—Process control or regulation for heat treatments for cooling

Definitions

• the present invention relates to a method and a cooling control device necessary for a forced cooling of a continuous circulating steel strip in an installation suitable for continuous annealing or continuous dipping according to the preambles of the claims. .
• the invention relates to continuous annealing furnaces for the heat treatment of cold rolled steel strips, particularly rapid cooling of said strips.
• the cold rolling of the steel causes hardening by hardening of the steel which causes a fragility making problematic or prohibiting the subsequent shaping of the rolled strips.
• such a continuous annealing line is shown schematically in FIG. 1, and typically comprises:
• an input section comprising one or two belt unrollers (1), a guillotine shear (2), a splicing welder (3) for connecting a tail of a strip from one of the unwinding machines to the d next strip from the other unwinder and thus ensuring a continuous operation of the line, a tape accumulator (4) which, on its downstream, restores the previously accumulated tape when the flow upstream of the accumulator is fixed to perform the splicing weld; • a furnace (5) with a preheating section (6), • a holding section at the annealing temperature (7), a quenching section (8), a section of several units on aging (9) followed by a cooling section under protective gas (10); An outlet section with an outlet accumulator (11), a "Skin-Pass” type strip lamination assembly (12), a shear (13) and one or two alternately working strip reels (14).
• the furnace must be able to provide, for tape speeds of several hundred meters per minute, heating and cooling rates and holding times adapted to the metallurgy of the treated steel. While the heating and maintenance times essentially affect the length of the furnaces and thus the investment costs, the cooling rate poses real technological problems.
• the water is treated according to evaporative cooling techniques such as cooling towers or air-cooling devices.
• evaporative cooling techniques such as cooling towers or air-cooling devices.
• the efficiency of these cooling processes is limited to minimum temperatures of approximately 30 ° C. at 35 ° C.
• An object of the present invention is therefore to provide a cooling control method and a device for its implementation, both adapted to a forced cooling of a continuous circulating steel strip in an installation adapted to continuous annealing. or a continuous dipping galvanization allowing advantageous cooling dynamics for any type of band under various annealing or galvanizing conditions.
• the method and the device according to the invention should have several advantages over existing processes or devices, in that: ⁇ they ensure efficient recovery of the energy yielded by the rolled steel strips during their cooling in the cooling sections of continuous annealing or galvanizing furnaces and their immediate reuse of this energy with maximum efficiency; • they allow to lower the temperature of the cooling water to values below 10 0 C;
• the invention thus proposes a cooling regulation method and a device for implementing it according to claims 1 and 6.
• a set of subclaims also has advantages of the invention as described later in the document.
• FIG. 3a, 3b Schematic diagrams of the device according to the invention, 8 001132
• FIG. 4 General flow diagram of fluids concerned by the device according to the invention in a continuous annealing installation
• Figure 5 Schematic diagram of the device according to the invention adapted to a gradual cooling of the strip by blowing
• FIG. 6 Schematic diagram of the device according to the invention adapted to cooling by immersion in a tank
• FIG. 2a schematically depicts a rapid cooling by gas jet (or blowing) in a continuous annealing furnace: a steel strip (B) scrolls vertically in a furnace - (5) while passing through at least one cell blowing (51).
• Each cell (51) comprises a fan motor unit (511) supplying a blow box (513) via a sheath (512).
• Each blow box (513) surrounds the strip and each of its two faces parallel to the strip is equipped with fresh gas diffusers (5131).
• the heated gas in contact with the strip is cooled in at least one cooling unit (514), each of which comprises a sheath (5141) ensuring the capture of the hot gas in the furnace chamber to bring it into an exchange device constituted by a gas / water exchanger (5142).
• a circulation of cold water between inlets and outlets (51421, 51422) lowers the temperature of the gas, which, thus cooled, returns to the suction inlet of the motor-fan (511).
• Figure 2b schematically describes a rapid cooling by cooled rolls:
• the steel strip (B) winds between a lower layer (RI) and an upper layer (RS) of several rollers arranged side by side and having parallel main axes, said rollers being cooled by circulation of water under low pressure.
• At least one of the two plies is able to move vertically in order to adjust the nesting of the rollers and, consequently, the arc of contact of the strip with the surface of the rollers in order to adjust the heat exchange between the two.
• the greater the arc of contact (by means of a large gap between the layers, that is to say an increase of the consecutive axis deviations of rollers), the more the cooling is intensified, and vice versa for reduce the cooling.
• FIG. 2c schematically shows the cooling rate range (V Ref ), between 1 and 10,000 ° C./s, of conventional methods for cooling steel strip: a cooled tube process (T), a jet jet process; gas (JG), a cooled-rolled process (RR), a water-spraying process or a water-gas mixture (PE) and finally, for the quickest, a quenching process in a water tank (TE). ).
• V Ref cooling rate range
• FIG. 3a shows a schematic diagram of the device according to the invention in relation to FIG. 2a by way of example, where a method of cooling by gas jet
• blowing cell implements a blowing cell (51) on the strip (B) in continuous scrolling.
• the heated gas is recovered in the enclosure of the furnace (5) and passes through a gas / water heat exchanger (5142) whose inlets and outlets (51421 and 51422), on the water side (to be cooled) , are connected to a vacuum cooling unit (52) associated with said exchanger (5142).
• FIG. 3a shows the cooling regulator according to the invention, which is necessary to 8 001132
• said device for forced cooling of a steel strip (B) circulating continuously in an installation suitable for continuous annealing or continuous dipping galvanization, said device comprising: at least one exchange member (51, 5142 ) providing heat transfer from the steel strip to a cooling water and including an outlet (51422) of the thus reheated cooling water,
• At least one cooling unit (52) consisting of a sealed enclosure (521) connected to the outlet (51422) of the exchange member (5142) and equipped with at least one outlet (5211) on a device a Venturi effect such as an ejector (522) with ( vapor and in which the cooling water is itself subjected to a vacuum vapor cooling,
• the blowing of the cooling gas is provided by blowing cells consisting of a motor-blower blowing into diffusion chambers placed on either side of the strip in order to cool them. two faces.
• the gas reheated in contact with the strip up to about 45 ° C. - 18 ° C. is sucked by the fan into the furnace chamber and passes through an exchange member consisting of a gas / water exchanger from which it exits to 30 0 C - 50 0 C before being reinjected by the fan into the diffusion chambers.
• the cooling is carried out by several cells placed one after the other along the path of the strip. The cooling thereof is progressive between the maximum temperature of 600 to 800 ° C.
• the device according to the invention may comprise several units. each having a cell or a battery of several cells of sulfur flage.
• Each unit can be dimensioned in order to stagger the temperature of the water returned to the exchange member, for example 30 to 100 ° C. in order to stagger the temperature of the cooling gases of the strip in the direction of scrolling of it. The highest water temperature returned upstream of the cooling section and the lowest temperature downstream where the temperature difference between the strip and the cooling gas is the lowest.
• a first cooling unit associated with a first exchange member situated upstream of the fan acts as described above and a second cooling unit associated with a second exchange member located in downstream of the fan ensures very well, with chilled water whose temperature is between 5 and 10 0 C, the cooling of the gas entering the diffusion chambers.
• the same principles can be implemented in a belt cooling system with cooled rollers in which the contact of the surface of the strip with the surface of the rollers acts as an exchange member (51, 5142), being connected to the cooling unit (52).
• This installation is particularly well adapted to an effective staging of the water temperature returned.
• the exchange member (51, 5142) between the strip and the cooling water can thus advantageously be, depending on the type of embodiment, a water / water or gas / water exchanger and applies to the progressive cooling processes of the band as cooling by cooled tubes or by gas jets or by cooled rollers.
• the cooling control device may comprise at least one steam condensing member (523) being disposed at the outlet of the ejector (522) of the sealed enclosure and adapted to replenish the enclosure watertight (521) by booster (5214) of a water level required in and, if necessary, adapted to redirect a surplus of said vaporized water to an external pipe (5233) for reuse or vapor dissipation, ideally for plant-specific or steam rejection purposes.
• at least one steam condensing member (523) being disposed at the outlet of the ejector (522) of the sealed enclosure and adapted to replenish the enclosure watertight (521) by booster (5214) of a water level required in and, if necessary, adapted to redirect a surplus of said vaporized water to an external pipe (5233) for reuse or vapor dissipation, ideally for plant-specific or steam rejection purposes.
• the cooling device may be of the "barometric" type, that is to say that the partial vacuum chamber is connected to the exchange member by a water column of height, generally equal or greater than eleven meters. This arrangement is particularly well suited to quenching type exchange sources, an example of application of the invention will be presented later.
• It can also be of closed type, the sealed enclosure under partial vacuum being connected to the exchange member by a closed circuit comprising a circulation pump.
• This arrangement is particularly suitable for exchange sources of the heat exchanger type.
• the steam supplying the ejector comes from a boiler for producing steam heated with the flue gases in the direct flame heating portion of the furnace or with the flue gases from the radiant tubes (see example according to Figure 4).
• the amount of steam thus produced is sufficient to meet both the needs of the ejector and a band degreasing section.
• the increase in the combustion efficiency reduces the amount of gas burned and the steam production capacity may be insufficient to cover the needs of the degreasing alone but remains sufficient for the feeding of the ejectors.
• a heat of condensation of the steam exiting the ejector and a heat recovered in the cooling water can be easily recovered in the condensing member (523) supplying hot water at a temperature of 50.degree. high temperature, close to the vaporization temperature at a pressure considered.
• the condenser member of the steam coming from the ejector may be an exchanger whose steam exchange circuit is supplied with water under low pressure, more or less hot, recovered from the installation, for example from a degreasing section, and reheated in the exchanger at a temperature equal to or slightly less than the vaporization temperature at the pressure in question. It can also be constituted by a direct contact exchanger ensuring a direct exchange between the steam from the ejector and the cooling water to be heated and generally returns a water at a temperature not much lower than the vaporization temperature at a pressure considered.
• a part of the water leaving the condenser element at a temperature can be used, after optional cooling, as deionized water in the continuous annealing or galvanizing plant.
• T VE3 a temperature
• a part of the water leaving the condenser element at a temperature can be used, after optional cooling, as deionized water in the continuous annealing or galvanizing plant.
• Said device according to the invention is thus advantageously adapted to the implementation of a cooling control method necessary for forced cooling of a steel strip (B) flowing in continuous scrolling in an installation suitable for continuous annealing or continuous dipping, characterized in that a cooling energy is transferred to heated water (ER) by the steel strip and then removed by vaporizing said heated water (ER) at a lower pressure (P ER2 ) at atmospheric pressure (P 0 ) and finally restored by condensation at a higher temperature (T VE2 ) after thermomechanical compression by a venturi-type device supplied with steam at a higher pressure (P VEI ) at atmospheric pressure (P 0 ) and comprising the following steps:
• the heated water (ER) from the exchange member (5142) is introduced in the form of a jet into a sealed enclosure (521) equipped with at least one ejector (522) as a venturi-type device said ejector being supplied with water vapor (5221) at an inlet pressure (P VEI ) greater than the atmospheric pressure (P 0 ),
• the ejector provides in the chamber (521) a partial vacuum corresponding to a second pressure (P ER ⁇ ) less than a vaporization pressure of the water at the first temperature (T ERI ), • a cooled water is recovered at an outlet (5213) of the sealed enclosure (521) at a second temperature (T ER2 ) corresponding to a temperature of vaporization of the water at the second pressure (P BR2 ) to be returned to the body of the exchange (5142).
• a complementary cooling circuit can be used at the outlet of the ejector, for which:
• a complementary cooling circuit is used at the ejector outlet, for which: a vapor exiting the ejector (522) and having a thermal energy linked to a decreasing kinetic energy and increased by the heat fraction resulting from cooling water obtained by vaporization, is obtained at an outgoing pressure (P VE2 ) greater than atmospheric pressure (Po),
• Said steam leaves the ejector at an outgoing temperature (T VE2 ) corresponding to a vaporization pressure of the water at the outgoing pressure (P VE2 ) and is put in direct contact in a heat exchanger (direct contact) with water, said water being at an external inlet pressure (P EI ) from an external inlet temperature (T E i) lower than an outgoing temperature (T E2 ) to said outgoing temperature (T E2 ) of the mixture two steam-water fluids able to reach the water vaporization temperature at the external inlet pressure (P EI ) -
• the method according to the invention allows the water leaving the condensing member (523) at the post-condensation temperature (T V E3) to be reintroduced as an addition in the sealed chamber (521).
• a sheath (5214) and, if necessary, a surplus of said water is redirected to an external pipe (5233) for reuse (if the condenser is a direct contact heat exchanger) or vapor dissipation (if the condensing member is a wall exchanger). Cooling is thus efficiently achieved in a circulation loop / dynamic heat transfer and also has a possibility to provide an excess of heat or energy remaining to other applications in need.
• the cooled water recovered at the outlet (5213) of the sealed enclosure (521) is a so-called ice water at the second temperature (T ER 2) of between 5 and 10 ° C. C.
• T ER 2 the second temperature
• This is simply conveyed to the inlet (51421) of the exchange member (5142), for example via a sheath (5215), in order to effectively cool the flow of gas circulation in the frame of a blowing band cooling.
• the invention according to FIG. 3a in view of the process and the device for its implementation thus very advantageously allows a dynamic recovery of energy stored by the water used for the forced cooling of a steel strip circulating continuously, the same water being reused for cooling purposes of the exchange member (51, 5142).
• the process according to the invention and the device for its implementation have several advantages over existing processes: * They ensure an efficient recovery of the energy yielded by the rolled steel strips when they are cooled in the cooling sections continuous annealing or galvanizing furnaces and its immediate re-use with maximum efficiency. It should be noted here that the targeted energy domain is beyond the Megawatt. Energy recoveries are therefore major and allow among other redistribution cooling loop or to deliver at least a portion of this recovered energy to other points of consumption, such as in the plant itself. The protection of the environment is therefore considerably increased.
• the condenser (523) of the steam actuating the ejector may be a simple wall exchanger; - The condenser (523) of the steam actuating the ejector may alternatively be a simple direct contact exchanger;
• the exchange member (51) between the steel strip and the cooling water may be a simple gas / water heat exchanger; between the sealed enclosure (521) and the exchange member (51, 5142), a water circulation circuit comprising a collection pipe (5212) and a return pipe (5215) ideally constituting a column of water equal to or greater than eleven meters may be arranged. between the sealed enclosure (521) and the exchange member (51,
• a water circulation circuit consisting of a closed circuit comprising at least one circulation pump may be arranged to facilitate the water transfer (for example in case of need for lifting);
• FIG. 3b describes a variant of the device according to FIG. 3a in which a first cooling unit (52a) is associated with a first exchange member (5142a) placed upstream of the fan (511) and fed with water cooled to 30 ° C and a second cooling unit (52b) is associated with a second exchange member (5142b) located between the fan (511) and the blower box (513) and supplied with ice water with a temperature of less than or equal to 10 0 C.
• the cooling is thus even more effectively adjustable while having the same energy recovery properties and other advantages associated with the device according to Figure 3a.
• the exchange member (51) may comprise at least two heat exchangers
• the device provides for example that:
• the exchange member (51) comprises at least one fan (511) feeding via an air duct (512) a blower box (513) in which the steel strip passes and fed by an air duct (5141) sensing the heat in the box (513),
• each of the air ducts. (512, 513) is coupled to one of the two heat exchangers (5142a, 5142b).
• FIG. 4 describes, by way of example and in connection with FIGS. 3a and 3b, the general flow diagram of fluids concerned by a cooling control device according to the invention in a continuous annealing system (B). .
• the annealing furnace (5) is equipped with a water cooling unit (52) associated with a rapid cooling unit of the band according to one of the methods previously described and mentioned in FIG. 2c.
• the device according to the invention also comprises a steam production unit (53) obtained by heating with fumes collected at the entrance of the strip in the oven in the preheating zone by a sheath (531) for collecting the fumes to a boiler
• the steam thus produced in the boiler feeds the ejector (522) of the cooling unit (52) via the sheath (532).
• the water heated by the strip heat is sensed at a suction port (51422), cooled in the sealed chamber (521) and returned to a discharge port
• the condenser (523) receives water at (5231) and discharges heated water at (5232). In this figure, the necessary pumping and winnowing accessories have not been shown for the sake of clarity.
• the ejector has an auxiliary input (5221) at its other input output (5211) of the sealed enclosure (521) through which the ejector is efficiently supplied by at least part up to all the required steam by means of a furnace (53) producing steam heated with flue gas (531) in a direct flame heating section of the furnace or with radiant tube section fumes.
• FIG. 5 depicts the block diagram of the device according to the invention adapted to a progressive cooling process (as in FIG. 2a), for example by gas jet using four blast cells (51a, 51b, 51c, 5Id ) each having one of four exchangers (or exchange members) assigned (5142a, 5142b, 5142c, 5142d) and being successively placed in the reverse direction of the strip (B) and two cooling units (52a, 52b) each with a sealed enclosure.
• the cells (51) are connected in parallel pairs, ie the first two cells (51a, 51b) associated with the first cooling unit (52a) and the two second cells (51c, 5Id) associated with the second cooling unit (52b).
• Water cooled by the second cooling unit (52b) is discharged at its output (5213b) at a first outlet temperature (T ER2b ) sealed chamber partly in the battery of the first two (in the direction of the band) exchangers (5142c, 5142d) by the tubing (5142Id) and partly in the first cooling unit (52a) by a booster tubing (5214a).
• the water cooled by the first cooling unit (52a) is then discharged at its outlet (5213a) at a second outlet temperature (T E R2a) lower than the first outlet temperature (T ER2b ) in the battery of the last two (depending on the direction of the band) exchangers (5142a, 5142b) by a pipe (51421b).
• T E R2a second outlet temperature
• a high dynamic cooling device such that at least one cooling unit (52a, 52b) is coupled to a plurality of heat exchange members (51a, 51b, 51c, 51d) distributed in the direction of travel of the band (B).
• Each exchange member or group of exchange members (5142a, 5142b) connected in parallel can thus advantageously be equipped with at least two cooling units connected in series.
• FIG. 6 depicts the block diagram of the device according to the invention adapted to strip cooling by immersion in a quenching tank.
• the strip (B) is immersed in a cooling water tank (54) by winding on two guide rollers (541, 542).
• the cooling unit (52) according to the invention is connected to the tank (54) by two pipes (5214, 5215) of height (H) above the level of the water contained in the tank, thus constituting a column of water at least once the atmospheric pressure and allowing the circulation of water without pumps of the "barometer" type.
• the exchange member (51) between the steel strip (B) and the cooling water is, for example, a simple quenching cooling tank containing water maintained at a constant temperature.
• the water of the final quenching tank of a continuous annealing or galvanizing plant is maintained at a temperature of between 5 and 10 ° C. and provides cooling of the so-called
• the partial vacuum allows, among other things, the degassing of the water tanks and removal of dissolved oxygen, which significantly reduces the oxidation of the hot band.
• a water circulation circuit consisting of a closed circuit including, if necessary for example for a lifting, at least one circulation pump.
• FIGS. 7a and 7b illustrate means for bringing devices according to the invention or certain of their elements into series in order to allow a more efficient / dynamic control of the cooling.
• FIG. 7a describes the series connection connection of two ejectors adapted to equip a sealed cooling enclosure such as that described from FIG. 3a, in that each cooling unit (52) is equipped with at least two ejectors (522a, 522b) connected in series.
• a steam outlet of the first ejector (522a) is directly disposed at one of the inputs of the second ejector (522b) connectable to a condensing member.
• the two ejectors are for example commonly supplied with steam by a boiler (5221).
• the two final and common inputs (5221) of the ejectors are connected to the partial evacuation output of a sealed enclosure.
• FIG. 7b describes (on the basis of the preceding example according to FIG. 5) the serialization of three cooling units.
• Tubes (514a, 5214b) successively connect a pregnant "water” outlet to a nearby "water” auxiliary entrance. Partial voids are thus formed in the enclosures, for which each of the outputs of their ejectors can be connected to a common condensing member (523).
• cooling units can be coupled to an exchange member (51) in order to advantageously stagger a decrease in the temperature of the cooling water.
• At least one of these cooling units (52a, 52b, 52c) may also be equipped with at least two ejectors connected in series.

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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)
• Coating With Molten Metal (AREA)

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• 2008
  • 2008-07-29 BR BRPI0822984-8A patent/BRPI0822984B1/pt not_active IP Right Cessation
  • 2008-07-29 EP EP08875607.7A patent/EP2304060B1/de not_active Not-in-force
  • 2008-07-29 US US13/056,691 patent/US8506877B2/en not_active Expired - Fee Related
  • 2008-07-29 WO PCT/FR2008/001132 patent/WO2010012869A1/fr active Application Filing

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