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
  • C21D9/562—Details
  • C21D9/563—Rolls; Drums; Roll arrangements
• • 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
  • C21D9/561—Continuous furnaces for strip or wire with a controlled atmosphere or vacuum
• • 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
  • C21D9/562—Details
  • C21D9/564—Tension control

Definitions

• the invention relates to continuous lines for annealing or galvanizing steel strips.
• galvanizing we refer here and thereafter to all dipped coatings, whether they are zinc coatings, aluminum coatings, zinc alloys, aluminum coatings or any other type of coating.
• the invention relates more particularly to the management of the tension of the strip of lines having successive furnaces.
• the one located downstream makes it possible to have a level of limited band traction in the overaging section located after the cooling chamber.
• the strip is reheated and maintained at a moderate temperature, for example 300 ° C.
• a 2 or 3 roll tensioning unit is used at the end of the furnace to significantly increase the tension of the band in the cooling tower.
• the annealing temperature is related to the chemical composition of the steel, its metallurgical state, in particular its level of hardening, as well as the rate of rise at the annealing temperature and the residence time at this temperature.
• the annealing temperature and the holding time thereto depend on the austenite fraction that is desired at the end of the hold. Typically, the annealing temperature is between 700 ° C and 1000 ° C.
• the strip is typically cooled to a temperature between 100 ° C and 300 ° C, depending on the desired metallurgical transformations. It is then again brought to an annealing temperature, and then cooled, before a possible survival section.
• the problem in a line with two consecutive annealing furnaces is that the two furnaces, and the chambers that constitute them, may have unusual operating conditions with respect to the lines containing only one annealing furnace. Indeed, each of the furnaces can operate at high or low temperature, or even be stopped, the tape still scrolling inside.
• the traction control between the annealing furnaces and the different chambers of the two furnaces is therefore a key point in order to avoid, as much as possible, production stoppages caused by bad guiding or breaking of the belt.
• a line comprising two successive annealing furnaces
• the length of strip present on the line is greatly increased compared to a traditional single-oven line, which makes it more difficult to ensure good guidance of the strip all along the line. his journey.
• the thermal transition or band-size transition phases require a particular traction control with a configuration of two consecutive annealing furnaces, since there are potentially several steel coils of different sizes and with different sizes. different thermal cycles which are at the same time in the whole of the thermal part constituted by the two consecutive furnaces.
• traction management is mastered by the state of the art. Is called a line of annealing or conventional galvanization, a line consisting of a single oven.
• the tractions are regulated so as to maintain a low traction in the heating chambers or to reduce progressively and slightly traction between the entrance of this room, colder, and its output, warmer, to avoid plastic deformation of the tape while ensuring its proper scrolling. Then, the traction is gradually increased in the cooling chambers.
• This traction control is conventionally done by the use of a torque control of the support rollers which serve to ensure the routing of the steel strip.
• the state of the art also proposes the use of a stretcher block in an oven upstream of a cooling chamber to maintain a low level of traction in the furnace and significantly increase the band pull in the chamber cooling.
• the first furnace may be composed of a heating section, for example with direct fired burners (NOF section) or radiant tubes (RTF section), or a combination of the two , a temperature holding section, and one or more gas cooling sections, a liquid, a gas and liquid mist, or a combination of a plurality of such means.
• a heating section for example with direct fired burners (NOF section) or radiant tubes (RTF section), or a combination of the two , a temperature holding section, and one or more gas cooling sections, a liquid, a gas and liquid mist, or a combination of a plurality of such means.
• the second furnace may, for example, be composed of a heating section (composed of an RTF), a temperature holding section, one or more gas cooling sections, a liquid, a fog of gas and a liquid or by a combination of several of these means.
• Other sections may be present, for example a post-cooling section after cooling.
• the steel strip is cooled to a temperature close to that of the zinc pot, then it is coated with zinc, or possibly with another type of coating. immersion in the zinc pot. It is then cooled to room temperature, for example by blowing air.
• the first difficulty of having two consecutive furnaces is to be able to control very different levels of traction in each of the two furnaces as a function of the temperature levels in the different chambers. This This difficulty is all the more important since the temperature operating range of the two furnaces is much wider than the current industrial practice. Indeed, between an operation of an oven at annealing temperatures of the order of 700 ° C to 950 ° C in the heating chamber, and operating regimes where the same oven or other oven is low temperature, typically between room temperature and 500 ° C in the heating chamber, there is a large range of traction control. Thus, the optimized operating requirements of a two-furnace line require great flexibility in the traction control of each of the two furnaces in a combined or separate manner.
• a continuous line for annealing or galvanizing metal strips arranged to receive a moving strip, comprising at least two consecutive annealing furnaces, and a tensioning unit consisting of at least two rollers that is arranged between the two ovens.
• the line according to the invention may further comprise means for controlling the tensioner block to control a traction of the band exerted by said tensioner block.
• the tensioner unit can be arranged, in the running direction of the strip, after a cooling section of the first furnace and before a heating section of the second furnace.
• the stretcher block may be disposed in an atmospheric separation buffer volume of said line, said volume being disposed between the upstream furnace and the downstream furnace.
• the line according to the invention may further comprise a battery with a strip length, said battery being arranged between the two annealing furnaces.
• a method of annealing or galvanizing metal strips in a line arranged to receive a moving strip comprising at least two consecutive annealing furnaces and a stretcher block consisting of at least two rollers that is arranged between the two ovens.
• a computer program product downloadable from a communication network and / or stored on a computer-readable medium and / or executable by a microprocessor, and loadable in an internal memory.
• a calculation unit characterized in that it comprises program code instructions which, when executed by the calculation unit, implement the steps of the method according to the invention, or one or many of his improvements.
• a 2 or 3 roll tensioning unit is placed between the first annealing furnace and the second furnace, typically between a last cooling chamber of the first furnace and a first heating chamber of the first furnace. second oven.
• This device prevents that the traction control of one oven is linked to the other oven. It controls high pulls in one oven and controls low pulls at the same time in the other oven. It furthermore makes it possible to significantly or immediately amplify or reduce the traction of the strip at the passage of a strip transition, that is to say at the passage of the junction between two format tapes and / or different quality.
• the invention may consist of a continuous line of annealing or galvanizing of metal strips comprising at least two consecutive annealing furnaces, a stretcher block composed of at least two rollers being located between the two ovens.
• the tensioner unit can be located after a cooling section of the first furnace and before a heating section of the second furnace.
• the stretcher block can be placed in an atmospheric separation buffer volume between the upstream furnace and the downstream furnace.
• an accumulator allowing the accumulation of a strip length can be implanted between the two annealing furnaces.
• This accumulator can be placed in a chamber delimited by external walls making it possible to separate the atmosphere present inside said chamber from outside air, the outer walls being thermally insulated in order to limit the thermal losses of the chamber, said chamber further comprising means for heating or maintaining the temperature of the strip.
• the invention may also consist of a system for controlling and optimizing the production of a line according to the invention, using differentiated parameters of tape running speed and / or strip tension in the two annealing furnaces. , in particular for optimizing the control of thermal transitions and band format changes between the two furnaces.
• the tensioner roll block can be placed in a buffer volume used to manage the separation of atmosphere between the two annealing furnaces. Indeed, depending on the thermal cycles and treated steel strips, it may be necessary to control different atmospheres between the two furnaces.
• Another difficulty of a line with two consecutive annealing furnaces is to manage the transitions between the different thermal cycles and the band formats.
• the transitions In a line with a single annealing furnace, the transitions have limited amplitudes and, in most cases, only one steel coil is heat-treated in the furnace.
• several steel coils with different formats, or requiring different thermal cycles, can be found at the same time. time in the line.
• the heating zones although able to operate at various temperature regimes, are still active. However, in a line with a double annealing furnace, the heating zones can be brought to work at temperatures much lower than those of a single oven, at around 500 ° C, or even below. Thus, conventional traction control systems with the support rollers of the chambers are not sufficient to maintain the right levels of traction in both furnaces.
• the tensioning unit between the two furnaces can operate by creating a traction jump, increasing or decreasing traction, at the proper moment of transition transition to allow control of the level. optimum traction for each of the bands at the passage of each of the two furnaces.
• the tensioner unit can also operate during stabilized production phases in order to adjust the good levels of traction in the second furnace with respect to the first furnace, which also makes it possible to resort to, or no longer resort to, slight variations in traction. on baffle baffles, which are technically more difficult and sensitive to control.
• the invention proposes, according to one possibility, the establishment of a zone of accumulation of tape between the two furnaces of annealing, typically between a last cooling chamber of the first furnace and the stretcher block at the inlet of the first heating chamber of the second furnace.
• This device thus makes it possible to completely separate the two consecutive furnaces in terms of speed and traction management. It can make it possible to accumulate a certain strip length during the stabilized operation phases, in order to make it possible to reduce the speed of movement in the first oven without modifying the speed of movement in the second oven.
• the intrafur accumulator may be empty and may make it possible to accelerate the speed of movement in the first furnace while maintaining a stable scrolling speed in the second furnace.
• This stable running speed in the second furnace is particularly important in the case of galvanizing lines, because a stable running speed is required, as much as possible, for the passage of the strip in a galvanizing bath which is directly at the exit of the second oven.
• Fig. 1 is a schematic view of a continuous line comprising two annealing furnaces according to the state of the art
• Fig. 2 is a schematic view of a continuous line comprising two annealing furnaces according to a first embodiment of the invention
• Fig. 3 is a schematic view of a continuous line comprising two annealing furnaces according to a second embodiment of the invention
• FIG. 4 is a schematic longitudinal view of an exemplary embodiment of an accumulation chamber placed between two annealing furnaces of a continuous line
• Fig. 5 is a schematic transverse view of the exemplary embodiment of an accumulation chamber placed between two annealing furnaces of FIG. 4.
• FIG. 1 there can be seen schematically represented processing sections of a continuous galvanizing line comprising two annealing furnaces 30, 40 according to the state of the art.
• the sections of the line located upstream and downstream are not shown in this figure.
• the band 1 transported by rollers 2 first enters a preheating section 3, for example direct fire, in which it is preheated to a temperature of, for example 500 ° C. It then passes into heating section 4 in which an annealing is carried out at a temperature of, for example, 800 ° C. The strip then passes into a cooling section in which the strip is cooled, for example to 250 ° C.
• a second heating section 6 in which a second annealing is carried out at a temperature of, for example, 700 ° C.
• the strip then passes into a second cooling section 7 in which the strip is cooled, for example up to 460 ° C. It then passes through a tensioner block 9 before entering a coating section 8 where it is immersed in a zinc bath 10.
• the configuration of the line is here simplified to facilitate the description of the invention.
• a real line would include a greater diversity of its sections, with for example rooms for heating, holding, slow cooling, rapid cooling, aging, etc.
• FIG. 2 shows schematically the process sections of a galvanizing line with two annealing furnaces according to a first embodiment of the invention.
• This figure shows the process sections of FIG. 1 previously described.
• a tensioning unit 1 1 with two rollers is placed after the cooling section 5 of the first furnace and before the heating section 6 of the second furnace. oven.
• the tensioner unit 1 1 is placed in a buffer volume 12 for managing the separation of atmosphere between the two furnaces.
• a section 14 of tape accumulation between the two annealing furnaces comprises a chamber 15 in which a strip 1 enters through the left side of the figure and leaves the right side through an airlock chamber 16 of atmospheres.
• the belt is conveyed by rollers 17, 18.
• the position of the set of seven rollers 17 placed at the bottom of the chamber 15 is fixed relative to the chamber.
• the six rollers 18, placed above all the rollers 17, move vertically between a low position A and a high position B in order to adjust the length of band present in the chamber.
• the rollers 18 are mounted on a mobile frame connected to a lifting device, not shown in this figure.
• the chamber 15 is maintained under a protective atmosphere composed of a mixture of nitrogen and hydrogen, for example 5% hydrogen.
• the atmosphere is, for example, injected into the chamber by injection points 19 and escapes from the chamber through vents 20.
• the walls 21 of the chamber are sealed and thermally insulated by refractory materials, for example the ceramic fiber, in order to limit the thermal losses of the chamber.
• the chamber 15 shown in FIG. 4 is shown schematically in transverse view.
• the rollers 17, whose position is fixed in the chamber 15, are rotated by motors 23.
• the rollers 18, whose position in the chamber is adjustable, are not motorized in this embodiment. They are rotated by the traction exerted by the band.
• the rollers 18 move vertically from a level A, in the lower part of the chamber, to a level B, in the upper part of the chamber, by means of a lifting device 24, comprising, for example, two non-represented electric winches, placed on either side of the chamber 15. Slots in the walls of the chamber allow the shafts of the rollers 18 to pass.
• the lifting device is kept under the same atmosphere as the chamber 15 by injection of gas at the injection points 25 and 26, in a volume delimited by leaktight walls 27.
• the combination of the sealed walls 21, 27 and the locks 16 separation of atmospheres makes it possible to maintain the chamber under a protective, non-oxidizing atmosphere for the strip.
• the system for controlling and optimizing the production of a continuous line for annealing or galvanizing metal strips with two annealing furnaces makes it possible to differentially control the speeds of travel of the strip and its level of traction. in both furnaces by acting on the tensioning unit 1 1 and, when present, the accumulation section 14.

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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)
• Tunnel Furnaces (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=58707832

Family Applications (1)

Country Status (7)

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Family Cites Families (10)

• 2017
  • 2017-03-13 FR FR1752021A patent/FR3063737B1/fr active Active
• 2018
  • 2018-03-13 WO PCT/FR2018/050594 patent/WO2018172658A1/fr unknown
  • 2018-03-13 US US16/493,466 patent/US20200131598A1/en not_active Abandoned
  • 2018-03-13 JP JP2019550238A patent/JP2020512483A/ja active Pending
  • 2018-03-13 CN CN201880018013.8A patent/CN110799657A/zh active Pending
  • 2018-03-13 KR KR1020197026836A patent/KR102512125B1/ko active IP Right Grant
  • 2018-03-13 EP EP18714303.7A patent/EP3596240A1/fr active Pending

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