Classifications

• • C—CHEMISTRY; METALLURGY
  • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
  • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
  • C23C2/00—Hot-dipping or immersion processes for applying the coating material in the molten state without affecting the shape; Apparatus therefor
  • C23C2/14—Removing excess of molten coatings; Controlling or regulating the coating thickness
  • C23C2/24—Removing excess of molten coatings; Controlling or regulating the coating thickness using magnetic or electric fields

Definitions

• process 1 The conventional hot-dip coating of strip (called process 1) with Zn, Zn-Al, Al or Al-Si alloys is described in the coating area in that the strip runs into the melt from an annealing furnace with the exclusion of air and by means of a different arrangement of non-driven rollers are deflected into the vertical and stabilized, cf. Figure 1. This applies to all coating metals / alloys listed for hot-dip coating.
• a disadvantage of method 1 is that the rollers and bearings of the rollers are located in the melt and all materials are exposed to the chemical attack of the melt. The service life of all internals within the melt is limited. Furthermore, a large melting volume with a correspondingly large melting vessel is required in order to accommodate the rolls or the entire bathing equipment. 200 - 400 tons of liquid zinc are common for hot-dip galvanizing. Rapid regulation of the melt with regard to temperature and alloy composition is not possible due to the large volume. Larger fluctuations in the above parameters have to be accepted and may lead to qualitative losses, since alloying measures and the strip quality in the same vessel influence one another. Another disadvantage is that the production speed, particularly in the case of thin strips ⁇ 0.5 mm, cannot be increased in order to achieve an economical system output (approx. 180 m / min). One reason for this is that there is relative movement between the rollers in the bath and the belt. If the trains are raised to avoid this problem, there is a risk of a belt break. The result is the production of scrap and longer plant downtimes.
• a further restriction for the maximum strip speed of a hot-dip galvanizing plant is given by the nozzle stripping system arranged above the zinc melt, cf. Fig. 1.
• the layer thickness is adjusted with air or nitrogen, whereby the minimum coating thickness that can be represented increases with increasing belt speed. This means that thin runs cannot be produced at high belt speeds. But especially thin runs ( ⁇ 25 g / m 2 , one-sided with hot-dip galvanized sheet) are required for certain demanding applications.
• So-called vertical hot-dip galvanizing is known as a further developed process for hot-dip coating of ferritic steel strip made of soft, unalloyed steels and is described in various patents such as EP 0 630 421 B1 and EP 0 630 420 B1 and EP 0 673 444 B1.
• the method 2 is characterized in that, at least in the coating area up to the weld pool, significantly higher belt speeds in the range of 300 m / min can be produced without problems even with thin steel belt, since there are no rollers in the coating vessel.
• the nozzle wiping process comparable to process 1, a in process 2, limits the maximum possible Ba speed in the case of thin coatings.
• the method 2 offers greater degrees of freedom, the galvanizing parameters temperature, viscosity of the melt and alloy composition, which also affect the layer thickness. For this reason, it can be expected that the belt speed in process 2 of the same layer thickness can be chosen to be higher than in process 1.
• method 2 is n on an industrial scale not been tested. So far, only trials with pilot plants with narrow belts have been carried out. These were successful.
• Cooling usually takes place with the aid of several air cooling sections arranged one behind the other.
• the cooling effect and more precisely the cooling rate is limited due to the medium and cannot be increased arbitrarily over a defined distance (e.g. 2 x 15 m) using the cooling medium air.
• a defined distance e.g. 2 x 15 m
• the cooling sections With increasing belt speed or with increasing mass throughput, the cooling sections have to be extended. However, this entails the increase in the upper deflection roller in the cooling tower of a hot-dip coating plant.
• the height of the upper pulley is usually between 30-60 m.
• the cooling sections would have to be correspondingly extended further at high belt speeds, and the cooling tower height could possibly be increased in the direction of 80-90 m. This entails higher investment costs for buildings and foundations.
• the object of the present invention is to avoid the above-mentioned disadvantages of methods 1 and 2 and to create a high-speed hot-dip coating plant without a cooling tower, which combines the least possible construction effort with optimized investment costs and high plant performance with the best production quality.
• Figure 1 shows a conventional coating process for strips
• FIG 4 shows the system according to Figure 3 in the start-up situations
• Figure 5 shows the system according to Figure 3 at a standstill after operation
• volume 1 runs vertically downwards into a container in which the melt pool is located after being deflected in the furnace with the exclusion of air. This weld pool is sealed at the bottom. Forces are required, which are not electromagnetic, but are generated with the help of rotating permanent magnets. Sealing the melt with permanent magnets is known per se. But rectangular channels were used there. This channel shape cannot be changed in distance and shape.
• the present invention proposes two adjacent rotors 5, 5 '.
• the rotors are tubes 6, 6 'made of temperature and melt resistant materials, preferably ceramic.
• the diameter of which can be freely selected, rollers rotate, on the lateral surface of which permanent magnets 4 are arranged.
• the rotors 5, 5 ' can be turned to melt or to the band. It is also possible to close gap 7 when the system is at a standstill or when starting up the system.
• Permanent magnets are considerably less expensive than electromagnetic sealing by means of coils or indectors, and much less energy is required for rotation than for electromagnetic sealing, which is particularly advantageous in the event of a power failure.
• the tape 1 can be clamped much shorter than in the previously known methods 1 and 2, since the tape 1 can be immediately cooled and deflected in a water bath 9 directly below the sealing unit.
• the guy length in the present invention is preferably only about 5000 mm, in process 1 this is approx. 8-10 times higher and in process 2 even higher.
• a further advantage of the method according to the invention is that the surface of the molten metal, preferably the zinc melt, is in the coating area within a protective gas atmosphere, preferably consisting of a nitrogen / hydrogen mixture, and there can be no disruptive oxidation of the liquid zinc.
• a protective gas atmosphere preferably consisting of a nitrogen / hydrogen mixture
• the plant for hot-dip coating a non-ferrous metal strip or a steel strip 1 is in the state of ongoing operation.
• the incoming and to be finished band 1 passes through a tensioning roller 17 in the furnace 2 and then through the lock 18, which the inside of the dip finishing the prevailing protective gas atmosphere hermetically seals off from the atmosphere of the environment.
• the strip 1 is deflected into the vertical against the coating section 19 via guide rollers 13.
• the strip 1 runs vertically from top to bottom through the bath of melt 3 maintained in the gap 7 between the rotors 5, 5 'and thus receives the desired coating.
• This melt pool 3 is prevented in a gap formed between spaced rotors 5, 5 ', at the lower end, from moving downwards with the aid of magnetic forces from magnetic fields or traveling magnetic fields of the rotating permanent magnets 4.
• the rotors 5, 5 ' are located within the pipes 6, 6' surrounding them in the coating section 19 which is surrounded on the outside by a channel-shaped housing and which accommodates the rotors 5, 5 in a variable manner. They are surrounded by the tubes 6, 6 'made of temperature and melt-resistant, in particular non-magnetic material, preferably ceramic.
• the permanent magnets 4 rotate within these tubes 6, 6 ′.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Coating With Molten Metal (AREA)
• Application Of Or Painting With Fluid Materials (AREA)

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Citations (10)

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• 2001
  • 2001-09-28 DE DE10148158A patent/DE10148158A1/de not_active Withdrawn
• 2002
  • 2002-09-25 PL PL02367442A patent/PL367442A1/xx unknown
  • 2002-09-25 ES ES02800118T patent/ES2264738T3/es not_active Expired - Lifetime
  • 2002-09-25 RU RU2004113102/02A patent/RU2300577C2/ru not_active IP Right Cessation
  • 2002-09-25 MX MXPA04002746A patent/MXPA04002746A/es active IP Right Grant
  • 2002-09-25 EP EP02800118A patent/EP1430162B1/de not_active Expired - Lifetime
  • 2002-09-25 HU HU0401759A patent/HUP0401759A2/hu unknown
  • 2002-09-25 CA CA002461912A patent/CA2461912A1/en not_active Abandoned
  • 2002-09-25 DE DE50206923T patent/DE50206923D1/de not_active Expired - Lifetime
  • 2002-09-25 CN CNB028191188A patent/CN1295373C/zh not_active Expired - Fee Related
  • 2002-09-25 JP JP2003532718A patent/JP2005504177A/ja not_active Withdrawn
  • 2002-09-25 WO PCT/EP2002/010741 patent/WO2003029507A1/de active IP Right Grant
  • 2002-09-25 BR BR0212938-8A patent/BR0212938A/pt not_active IP Right Cessation
  • 2002-09-25 AT AT02800118T patent/ATE327352T1/de not_active IP Right Cessation
  • 2002-09-25 KR KR10-2004-7004546A patent/KR20040045011A/ko not_active Application Discontinuation
  • 2002-09-25 YU YU25704A patent/YU25704A/sh unknown
  • 2002-09-25 US US10/490,780 patent/US20050048216A1/en not_active Abandoned
  • 2002-09-25 UA UA20040403187A patent/UA78722C2/uk unknown
• 2004
  • 2004-02-26 ZA ZA200401565A patent/ZA200401565B/en unknown

Patent Citations (10)

Non-Patent Citations (5)

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