EP0728847A1 - Verfahren zur Wärmebehandlung von Metallbändern - Google Patents

Verfahren zur Wärmebehandlung von Metallbändern Download PDF

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Publication number
EP0728847A1
EP0728847A1 EP96300898A EP96300898A EP0728847A1 EP 0728847 A1 EP0728847 A1 EP 0728847A1 EP 96300898 A EP96300898 A EP 96300898A EP 96300898 A EP96300898 A EP 96300898A EP 0728847 A1 EP0728847 A1 EP 0728847A1
Authority
EP
European Patent Office
Prior art keywords
metal strip
float
flow rate
nozzle units
heat transfer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
EP96300898A
Other languages
English (en)
French (fr)
Inventor
Kenji Kawate
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Daido Steel Co Ltd
Original Assignee
Daido Steel Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Daido Steel Co Ltd filed Critical Daido Steel Co Ltd
Publication of EP0728847A1 publication Critical patent/EP0728847A1/de
Ceased legal-status Critical Current

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    • 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
    • C21D9/63—Continuous furnaces for strip or wire the strip being supported by a cushion of gas

Definitions

  • This invention relates to a method of heat treatment of a metal strip.
  • a floating-type heat treatment furnace is used to carry out a heat treatment, such as annealing and solution heat treatment, of a metal strip such as an aluminum plate, a stainless steel plate, a copper plate, a plate of a copper alloy or a plate of an iron-nickel alloy, while it is being transported inside the furnace in a floating condition.
  • This invention relates to an improvement in such heat treatment method of a metal strip.
  • a heated infurnace environmental gas is guided to nozzles by means of a gas-circulating fan and emitted out therethrough to heat the metal strip while causing it to float and be transported horizontally inside the furnace at the same time.
  • Two kinds of nozzles are usually provided for this purpose, the socalled float nozzles and heat transfer nozzles.
  • the float nozzles are those which are so structured and positioned as to provide a static pressure for causing the metal strip to float
  • the heat transfer nozzles are those which are so structured and positioned as to provide a dynamic pressure for heating it convectively.
  • the float nozzles do not contribute at all to the heating of the metal strip, or that the heat transfer nozzles do not contribute at all to the flotation of the metal strip, but the float nozzles, because they are primarily for causing the metal strip to float, must be operated such that the gas flow rate therethrough should be sufficiently large to be able to keep the metal strip in the floating condition.
  • float nozzles are sometimes provided both above and below the metal strip, serving as wave-generating nozzles for forming waves on the metal strip.
  • the gas flow rate through the float nozzles cannot be reduced too much because of the requirement that waves must be formed on the metal strip, and the control on the gas flow rate from the heat transfer nozzles becomes even more severely limited. If the extent of control on the gas flow rate is limited, there arise many problems, as will be described below.
  • the flow rate of the gas through the heat transfer nozzles cannot be controlled over a sufficiently wide range, and the furnace temperature can be raised only to the extent allowed by such a limited control. If the desired change in the thickness of a metal strip is relatively small such that the required increase in the furnace temperature is correspondingly small, a furnace operating using this prior art technology may not give rise to any problem. If the desired change in thickness is relatively large and the furnace temperature must be increased beyond the allowed range, however, the prior art method is no longer applicable. In such a situation, the heat treatment will have to be discontinued until the furnace temperature reaches a required level. It now goes without saying that this affects the productivity efficiency adversely in a serious manner.
  • a method of heat treatment of a metal strip according to this invention may be characterized as separately controlling the gas flow rates through float nozzles and through heat transfer nozzles such that the gas flow rate through the float nozzles is kept sufficiently large, even when it is reduced, such that the metal strip can be kept in the floating condition even if the gas flow rate through the heat transfer nozzles is reduced to zero.
  • a wind tunnel with partitioning guide plates is connected to the float nozzles, and a gas-circulating fan for directing the environmental gas towards the float nozzles is provided on the upstream side of the wind tunnel.
  • another wind tunnel with partitioning guide plates is connected to the heat transfer nozzles, and another gas-circulating fan for directing the environmental gas towards the heat transfer nozzles is provided on the upstream side of this wind tunnel.
  • the flow rate through the heat transfer nozzles may be controlled by adjusting the number of rotation of the gas-circulating fan or the opening of the dampers in the wind tunnel, or both, by using as control parameters the measured nozzle pressure value or the measured flow rate value inside the wind tunnel. More in detail, the number of rotation of the motor for driving the gas-circulating fan may be controlled through a rotation control means by inputting the measured nozzle pressure value into a calculating device and using a signal outputted therefrom according to the difference between a pre-set value and the measured value.
  • Figs. 1 and 2 show an example of heat treatment fumace 11 adapted to use a method according to this invention, provided with a plurality of float nozzle units 21 and a plurality of heat transfer nozzle units 22.
  • the float nozzle units 21, each provided with a plurality of float nozzles are primarily for causing flotation of the metal strip A by providing static pressure
  • the heat transfer nozzle units 22, each provided with a plurality of heat transfer nozzles are primarily for heating the metal strip A by providing dynamic pressure, as explained above. Since the metal strip A must be kept in a floating condition while it is being transported horizontally inside the furnace 11, as shown by a horizontal arrow in Fig.
  • the float nozzle units 21 are characterized wherein the flow rate of gas therethrough is not reduced to zero but only to the extent that the metal strip A can still be kept in a floating condition even if the gas flow rate through the heat transfer nozzles is reduced to zero. Since the heat transfer nozzles are not expected to significantly contribute to the flotation of the metal strip A, by contrast, the gas flow rate therethrough may be reduced by 100%, or to zero, depending on the kind of heat treatment being carried out.
  • the plurality of float nozzle units 21 may be arranged all on the underside of the metal strip A at uniform intervals longitudinally in the direction of motion of the metal strip A, and the heat transfer nozzle units 23 are provided both on the upper side and the underside of the metal strip A, some of them being provided on the underside between mutually adjacent pairs of the float nozzle units 21, the others of the heat transfer nozzle units 22 being above the metal strip A, each opposite one of the float nozzle units 21 or the heat transfer nozzle units 22 disposed on the underside of the metal strip A.
  • the float nozzle units 21 are each connected through a header 21a to a wind tunnel 31a which is formed by guide boards 31 and has a gas-circulating fan 41 on the upstream side of the wind tunnel 31a.
  • the heat transfer nozzle units 22 are each connected through another header 22a to another wind tunnel 32a which is formed by guide boards 32 and has another gas-circulating fan 42 on the upstream side of the wind tunnel 32a.
  • the gas-circulating fan 41 serves to circulate the environmental gas heated by a heater 51 to the float nozzle units 21 through the wind tunnel 31a and the headers 21a, causing it to flow upward out through the float nozzle units 21 toward the metal strip A and thereby keeping the metal strip A in a floating condition.
  • the gas-circulating fan 42 serves to circulate the environmental gas heated by the heater 51 to the heat transfer nozzle units 22 through the wind tunnel 32a and the headers 22a, causing it to flow out upward or downward through the heat transfer nozzle units 22 to thereby heat the metal strip A.
  • Motors 61 and 62 are connected to the gas-circulating fans 41 and 42, respectively.
  • Rotation control devices 71 and 72 are connected to the motors 61 and 62, respectively.
  • Calculating devices 81 and 82 are connected to the rotation control devices 71 and 72, respectively.
  • devices for measuring gas pressure at nozzle positions are provided, and a measured nozzle pressure value at the float nozzles 21 is inputted to the calculating device 81 and measured nozzle pressure value at the heat transfer nozzle units 22 is inputted to the calculating device 82.
  • the calculating devices 81 and 82 compare these measured values with a pre-set value and output signals, according to which the rotary motion of the motors 61 and 62 is controlled independently through the rotation control devices 71 and 72.
  • a thin, belt-like elongated aluminum strip of thickness 2.5mm and width 1500mm was subjected to an annealing process.
  • the furnace temperature was 580°C
  • the temperature of the metal strip was 500°C
  • the transfer speed of the metal strip was 50m/minute.
  • the furnace temperature was increased to 650°C at a rate of 100°C/hour while the flow rate through the float nozzle units was reduced to 90% and the flow rate through the heat transfer nozzle units was reduced to 30% at a rate of about 1.7%/minute.
  • the furnace temperature rose to 650°C in about 42 minutes after the control of the flow rates was started. No problem was encountered regarding the quality of the heat-treated strip.
  • the furnace temperature is made higher for the heat treatment of a thicker metal strip than for the heat treatment of a thinner metal strip.
  • the temperature of the metal strip is affected by the furnace temperature (that is, the temperature of the environmental gas inside the furnace) through radiative heating, but it is more strongly influenced by the flow rate of the gas convectively transferring heat. If a thicker metal strip being subjected to a heat treatment is replaced by a thinner metal strip with the same gas flow rate through the heat transfer nozzles kept the same, for example, the thin metal strip will undergo a thermal deformation and may even break because the furnace temperature is still too high when the thinner metal strip is first introduced into the furnace.
  • the flow rate of the gas through the heat transfer nozzle units may have to be reduced to zero. Since this thinner metal strip must also be kept in a floating condition, however, the flow rate of the gas through the float nozzle units cannot be reduced to zero. In other words, if the flow rate through the float nozzle units is to be varied between a maximum value and a minimum value, this minimum value cannot be zero but depends on the weight of the metal strip to be kept in the floating condition. If the flow rate through the heat transfer nozzle units is reduced to zero, as described above, the furnace temperature becomes lower gradually. When it becomes impossible to keep the metal strip at a desired temperature merely through the environmental gas, the flow rate through the heat transfer nozzle units is gradually increased to maintain the temperature of the metal strip at the desired level.
  • Fig. 3 shows another furnace using a method according to this invention, similar to the one described above with reference to Figs. 1 and 2 but different therefrom in that both float nozzle units 23 and 23' and heat transfer nozzle units 24 are disposed not only on the underside of the metal strip B but also thereabove. As shown in Fig.
  • float nozzle units 23 and heat transfer nozzle units 24 are alternately disposed on the underside of the metal strip B in the direction of motion of the metal strip B, and float nozzle units 23' and heat transfer nozzle units 24 are also alternately disposed above the metal strip B in the direction of motion of the metal strip B such that the float nozzle units 23' above the metal strip B are exactly above different ones of the float nozzle units below the metal strip B and those of the heat transfer nozzle units 24 above the metal strip B are exactly above different ones of the heat transfer nozzle units 24 below the metal strip B. As also shown schematically in Fig. 3, those of the float nozzle units 23' above the metal strip B are smaller than those of the float nozzles 23 below the metal strip B.
  • a furnace with float nozzle units arranged thus is particularly useful for the heat treatment of a thinner metal strip because thin metal strips are more strongly influenced by the upward force from the float nozzle units 23, tending be vibrate if there were no float nozzles above the metal strip B to stabilize its horizontal motion.
EP96300898A 1995-02-21 1996-02-09 Verfahren zur Wärmebehandlung von Metallbändern Ceased EP0728847A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP57888/95 1995-02-21
JP5788895A JPH08225858A (ja) 1995-02-21 1995-02-21 金属ストリップの熱処理方法

Publications (1)

Publication Number Publication Date
EP0728847A1 true EP0728847A1 (de) 1996-08-28

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EP96300898A Ceased EP0728847A1 (de) 1995-02-21 1996-02-09 Verfahren zur Wärmebehandlung von Metallbändern

Country Status (2)

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EP (1) EP0728847A1 (de)
JP (1) JPH08225858A (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2213754A1 (de) * 2009-01-13 2010-08-04 Chugai Ro Co., Ltd. Streifenmaterialbehandlungsvorrichtung
CN113454246A (zh) * 2019-02-28 2021-09-28 艾伯纳工业炉公司 浮动带式炉
WO2022110166A1 (zh) * 2020-11-30 2022-06-02 苏州中门子工业炉科技有限公司 一种铝卷带材连续固溶热处理炉的气垫发生器

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1068059A (en) * 1964-09-02 1967-05-10 British Furnaces Ltd A method and apparatus for stabilizing strip work
GB2068417A (en) * 1980-01-18 1981-08-12 Sumitomo Light Metal Ind Method for heat treatment of metal strips
JPS57158329A (en) * 1981-03-25 1982-09-30 Daido Steel Co Ltd Working method
DE3318861C1 (de) * 1983-05-25 1984-11-08 Vits-Maschinenbau Gmbh, 4018 Langenfeld Vorrichtung zum schwebenden Fuehren von Materialbahnen,insbesondere mit einer Heizeinrichtung zum Gluehen von Aluminiumbaendern
JPH03277727A (ja) * 1990-03-27 1991-12-09 Kawasaki Steel Corp 接続部でサイズを異にする連続走行金属ストリップの非接触支持制御方法
JPH05255763A (ja) * 1992-03-13 1993-10-05 Chugai Ro Co Ltd 連続式炉の生産条件変更方法
JPH05255761A (ja) * 1992-03-10 1993-10-05 Chugai Ro Co Ltd 連続式炉の処理条件調整方法およびその装置

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1068059A (en) * 1964-09-02 1967-05-10 British Furnaces Ltd A method and apparatus for stabilizing strip work
GB2068417A (en) * 1980-01-18 1981-08-12 Sumitomo Light Metal Ind Method for heat treatment of metal strips
JPS57158329A (en) * 1981-03-25 1982-09-30 Daido Steel Co Ltd Working method
DE3318861C1 (de) * 1983-05-25 1984-11-08 Vits-Maschinenbau Gmbh, 4018 Langenfeld Vorrichtung zum schwebenden Fuehren von Materialbahnen,insbesondere mit einer Heizeinrichtung zum Gluehen von Aluminiumbaendern
JPH03277727A (ja) * 1990-03-27 1991-12-09 Kawasaki Steel Corp 接続部でサイズを異にする連続走行金属ストリップの非接触支持制御方法
JPH05255761A (ja) * 1992-03-10 1993-10-05 Chugai Ro Co Ltd 連続式炉の処理条件調整方法およびその装置
JPH05255763A (ja) * 1992-03-13 1993-10-05 Chugai Ro Co Ltd 連続式炉の生産条件変更方法

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 006, no. 266 (C - 142) 25 December 1982 (1982-12-25) *
PATENT ABSTRACTS OF JAPAN vol. 016, no. 098 (C - 0918) 11 March 1992 (1992-03-11) *
PATENT ABSTRACTS OF JAPAN vol. 018, no. 030 (C - 1153) 17 January 1994 (1994-01-17) *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2213754A1 (de) * 2009-01-13 2010-08-04 Chugai Ro Co., Ltd. Streifenmaterialbehandlungsvorrichtung
CN101775481B (zh) * 2009-01-13 2012-10-17 中外炉工业株式会社 带材处理装置
CN113454246A (zh) * 2019-02-28 2021-09-28 艾伯纳工业炉公司 浮动带式炉
US20220162719A1 (en) * 2019-02-28 2022-05-26 Ebner Industrieofenbau Gmbh Strip flotation furnace
US11708621B2 (en) 2019-02-28 2023-07-25 Ebner Industrieofenbau Gmbh Strip flotation furnace
WO2022110166A1 (zh) * 2020-11-30 2022-06-02 苏州中门子工业炉科技有限公司 一种铝卷带材连续固溶热处理炉的气垫发生器

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