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
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F27—FURNACES; KILNS; OVENS; RETORTS
  • F27B—FURNACES, KILNS, OVENS, OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS
  • F27B9/00—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity
  • F27B9/28—Furnaces through which the charge is moved mechanically, e.g. of tunnel type; Similar furnaces in which the charge moves by gravity for treating continuous lengths of work

Definitions

• the present invention relates to a method, a device and a system for heat treatment of a moving metal strip.
• annealing One type of heat treatment process is called annealing.
• the metal is heated to reach temperatures ranging, for example, from 500 0 C to 1100 0 C and then cooled in order to modify the crystal structure of the metal.
• a disadvantage of such a process, as well as other heat treatment processes, is its high energy consumption.
• the heating of the sheet is obtained by running it in front of radiant tubes in which flue gases from the combustion of a fuel and air circulate. In these installations, it has already been planned to recover heat from the flue gases leaving the radiant tubes to preheat the combustion air.
• the heat consumed is worth, in spite of this recovery, of the order of 1, 7 times the heat found in the sheet, which corresponds to a yield of 60%.
• Such a regenerative process comprises a heating of the strip, a cooling of the heated strip, and a heat transfer of at least one a segment of the web being cooled to at least one segment of the web being heated so as to perform at least a portion of each of said web cooling and heating.
• the problem to be solved is the reduction of energy consumption in a heat treatment process of a moving metal strip.
• this problem is solved by performing said heat transfer mainly by conduction. In this way, the heat is transmitted very efficiently without the need for an important additional energy supply in the form of work.
• Conduction heat transfer is the most efficient form of heat transfer.
• said heat transfer is performed from a plurality of segments of the band being heated to a plurality of segments of the band being cooled in reverse order in the tape running direction.
• said heat transfer is performed from a plurality of segments of the band being heated to a plurality of segments of the band being cooled in reverse order in the tape running direction.
• the strip is further heated by a heat source external to the strip.
• a thermal differential for driving said heat transfer is created between the band being cooled and the band being heated.
• said heat transfer is effected via at least one heat conducting solid element in contact with a segment of the strip being heated and a segment of the strip being cooled.
• said at least one heat-conducting solid element is in the form of a roll, preferably a metal one. Such a roller can ensure continuous contact, and therefore good heat conduction, with the two segments of the moving strip.
• the segment of the web being cooled is in contact with said roll at a contact angle of at least 20 °, preferably at least 30 °.
• a contact angle of at least 20 °, preferably at least 30 °.
• the segment of the web being heated is in contact with said roll at a contact angle of at least 20 °, preferably at least 30 °.
• the temperature difference between a metal strip segment during cooling and a strip segment during heating between which at least a part of said conduction heat transfer takes place is at least 200 ° C. and / or or below 500 0 C.
• Such a difference in temperature would allow a efficient heat transfer, without causing excessive heat shock in the metal strip.
• the present invention also relates to a heat transmission device for simultaneously heating a metal strip moving upstream of an additional heating zone and cooling downstream of said additional heating zone.
• the device comprises at least one heat-conducting solid element intended to be in contact with the said metal strip both upstream and downstream of the main heating zone, so as to transfer heat by conduction between at least one segment of the downstream metal strip and at least one segment of the upstream metal strip.
• the device comprises a series of several heat-conducting solid elements, for example five, for successively contacting said metal strip both upstream and in reverse order in the running direction of the strip, downstream of the heating zone. principal, so as to transfer heat by conduction between segments of the metal strip downstream and segments of the metal strip upstream. In this way it is possible to ensure a progressive heating of the band during heating and equally progressive cooling of the band during cooling, in order to avoid thermal shocks while ensuring a significant heat transfer.
• the device further comprises at least one baffle roll for defining a contact angle, preferably at least 20 °, between said metal strip upstream and / or downstream of the furnace and said heat-conducting solid element. in the form of a roll.
• the present invention also relates to a heat treatment system, in particular annealing, continuously a strip scroll metal having a main heating zone and a heat transmission device according to the invention.
• FIG. 1 shows a diagram of an earlier method
• FIG. 2 shows a diagram of a method according to an embodiment of the invention
• FIG. 3 shows a heat treatment system according to an embodiment of the invention.
• FIG. 4 shows a heat treatment system according to an alternative embodiment of the invention
• FIG. 5 shows a heat transmission device according to one embodiment of the invention
• FIG. 6 shows heating curves. and cooling the metal strip which can be obtained with the heat transmission device of Figure 5.
• FIG. 1 a conventional method of continuously annealing a moving steel strip is schematically illustrated. After cleaning 1 of the strip, it is heated from 30 0 C to 800 0 C in a heating step 2 in a radiant tube furnace. This specifies an energy input of 210 kW per tonne of steel in the form of natural gas, producing 50 kg of CO 2 and 80 mg of NO x per tonne of steel.
• FIG. 2 an embodiment of the method of the present invention is shown schematically.
• the heating is divided into a preheating step 2a wherein the steel strip is preheated to 30 0 C at 450 ° C., and a main heating step 2b in a radiant tube furnace, in which the strip is heated from 450 ° C. to 800 ° C.
• the heat Q 'transferred to the strip in the preheating stage 2a comes from the cooling 3 of the same 800 ° C band at 450 ° C and is transmitted by conduction.
• FIG. 3 represents a system 4 for continuously annealing a moving steel strip 5, according to one embodiment of the invention.
• This system 4 comprises a device 6 for conductive heat transmission for preheating 2a and cooling 3 of the strip 5, and a furnace 7 for radiant tubes 8 for the additional heating 2b of the strip 5.
• the furnace 7 with radiant tubes 8 is of the vertical type.
• the device 6 for heat transmission is illustrated in greater detail in FIG. 5.
• the strip 5 enters the device 6 through the inlet opening 9 and passes through said device 6 in the direction 10 to the oven 7 preheating. After the main heater 2b, the strip 5 spring oven and through the device 6 in the opposite direction 1 1 to the outlet opening 12 while cooling.
• the device 6 comprises an alignment of seven heat conducting rolls 13 and two alignments of six deflector rollers 14, one on each side of the conductive roller alignment 13.
• both the conductive rollers 13 and the rollers deflectors 14 have a diameter of 800 mm.
• alternative diameters for each roll, as well as arrangements with different roll layouts and numbers could be contemplated by those skilled in the art depending on the circumstances.
• the conductive rollers 13 must have a diameter capable of ensuring a good contact surface with the band 5 with a comparatively reduced speed of rotation, while avoiding plastic deformation of the band 5.
• the deflector rollers 14 must also have a diameter that avoids A plastic deformation of the strip 5.
• the conductive rollers 13 and baffles 14 may therefore have diameters lying, for example, in a range between 400 and 1600 mm. Due to the thermal expansion of the band 5, the speed of the band 5 during cooling is normally higher than its speed during heating.
• the conductive roller 13 could have an angularly variable radius for adjusting the effective radius of the conductive roller 13 to the speed of the strip 5 on each side of the conductive roller 13.
• Another possible solution is that the conductive roller 13 is divided into radial segments, having a certain freedom of angular movement relative to each other.
• the baffle rollers 14 hold segments 5a of the strip 5 during preheating and segments 5b of the strip 5 being cooled at the same time. contact with the conductive rollers 13 at contact angles ⁇ . Different contact angles ⁇ can be envisaged by those skilled in the art depending on the circumstances. Each conductive roll 13 thus transfers heat by conduction of a segment 5b of the band 5 during cooling to a segment 5a of the band being heated. As the strip 5 passes through the device 6 in opposite directions 10,11 during preheating and during cooling, the strip 5 contacts the conductive rollers 13 in reverse order in its course during heating and during cooling.
• This heat conduction will therefore be performed between the last segment 5b of the strip 5 during cooling and the first segment 5a of the strip 5 being preheated, between the penultimate segment 5b of the strip 5 during cooling and the second segment 5a of the strip 5 during preheating, and so on.
• the temperatures of the strip 5 during cooling and during preheating follow, respectively, the curves 15 and 16 along the device 6, as illustrated in FIG. 6.
• the bearings 17 correspond to the temperatures of the conductive rollers 13, each of them being intermediate to those of the segments 5a and 5b with which the respective conductive roller 13 is in contact .
• Table 1 presents the parameters of an embodiment of the thermal treatment method of the invention in the device 6 described above with a strip 5 with a thickness of 1 mm, 1500 mm wide and a speed of 150 m / min for a production of 106 tons per hour.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Crystallography & Structural Chemistry (AREA)
• Thermal Sciences (AREA)
• Physics & Mathematics (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• General Engineering & Computer Science (AREA)
• Heat Treatment Of Strip Materials And Filament Materials (AREA)
• Tunnel Furnaces (AREA)
• Heat Treatments In General, Especially Conveying And Cooling (AREA)

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• 2007
  • 2007-07-12 BE BE2007/0348A patent/BE1017683A3/fr not_active IP Right Cessation
• 2008
  • 2008-07-08 CN CN2008800244691A patent/CN101743331B/zh not_active Expired - Fee Related
  • 2008-07-08 AT AT08774880T patent/ATE488608T1/de active
  • 2008-07-08 ES ES08774880T patent/ES2355695T3/es active Active
  • 2008-07-08 PL PL08774880T patent/PL2171105T3/pl unknown
  • 2008-07-08 EP EP08774880A patent/EP2171105B1/de active Active
  • 2008-07-08 US US12/668,534 patent/US20100186940A1/en not_active Abandoned
  • 2008-07-08 DE DE602008003585T patent/DE602008003585D1/de active Active
  • 2008-07-08 WO PCT/EP2008/058835 patent/WO2009007362A1/fr active Application Filing

Non-Patent Citations (1)

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