US3294596A - Process and apparatus for annealing thin steel plates - Google Patents

Process and apparatus for annealing thin steel plates Download PDF

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Publication number
US3294596A
US3294596A US448033A US44803365A US3294596A US 3294596 A US3294596 A US 3294596A US 448033 A US448033 A US 448033A US 44803365 A US44803365 A US 44803365A US 3294596 A US3294596 A US 3294596A
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gas
furnace
hydrogen
circulation
steel
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US448033A
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English (en)
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Daubersy Jean
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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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/767—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material with forced gas circulation; Reheating thereof
    • 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
    • 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
    • C21D9/60—Continuous furnaces for strip or wire with induction heating
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the process according to the invention relates to the fabrication of thin steel plates or sheets of mild steel which are specially provided for stamping; this quality is obtained by wet hydrogen by extracting during an annealing operation carbon and nitrogen which render steel aging.
  • Their use for a decarburizing-denitrifying annealing operation comprises in principle a period of heating under a neutral protective gas (such as the known HNX. gas which is a dry mixture of nitrogen and3 to 10% in volume of hydrogen), a period of soaking (maintenance at constant temperature) in an atmosphere of moist or wet H gas 3,294,596 Patented Dec. 27, 1966 and a period of cooling under a protective gas such as said dry HNX gas.
  • a neutral protective gas such as the known HNX. gas which is a dry mixture of nitrogen and3 to 10% in volume of hydrogen
  • This circulation internal to the furnace comprises the successive flowing of the gases through the turbine, along the heated walls of the bell and through the spirals of the coils, according to a cycle beginning again endlessly with a rate of flow resulting from the motive power due to the fan and the internal'resistance of the circuit.
  • an external circulation comprising the injection in the furnace of a certain quantity of fresh gases and the extraction of an approximately equal volume of gas contaminated by the impurities coming from the chemical reactions which take place in the furnace.
  • the fan has without doubt an appreciable effect on the time of heating in a relatively dense atmosphere of HNX gas (more than ofN but when the gases become heated and especially when the protective atmosphere is replaced by moist hydrogen considerably lighter and carried to temperatures of the order of 700 C. the rate of flow shuts down considerably.
  • the rate of flow of the gas circulating in the coils when measured in normal cubic meters (that is in cubic meters (m3) .at a pressure of 760 mm. of Hg and rat a temperature of 0 C.), was in the period of soaking with moist hydrogen reduced to less than of the rate of'flow of gas realized at the beginning of the heating under HNX gas.
  • the type of laminar circulation has this in particular, that the loss of charge is independent of-the density of the gas but is proportional to the absolute viscosity.
  • the loss of charge is on the contrary proportional to the. density and independent of the viscosity.
  • the motive pressure created by the ven- 3 tilator is, on the other hand, proportional to the density of the fluid.
  • the fresh gas injected when the fan delivers on the internal circuit, the fresh gas injected must necessarily be differently from the speeds realized in a circut comprising 5 mixed with the contaminated gas in circulation and the a ventilator and charges of any kind (turbulent flow) high degrees of purity necessary for denitrification are when one passes from HNX gas (heavy and cold) to H only very slowly attained. To obtain a non-ageing steel gas (very light and hot).
  • the meihod l the Invention charaqtensed m at the two circulations are malntained during the period The 1055 of Charge P unit of length undergone by of heating, whereas during the period of soaking, which a fluid Circulating in laminar fashion at a means Speed U is the period of the reactions of decarbonisation and of between two Plates distant y E ff 0m 0116 another is given denitration by humid hydrogen, the internal circulation y the formula: is stopped and at the same time the external circulation U is considerably increased.
  • the reactive gases then pass 11:18 HE- through the furnace and its change under the eifect only of the pressure existing in the feed system, and pass only in which is the absolute viscosity of the fluid and K once through the spirals of the coil thus carrying off a cofifiicient of proportionality
  • This cotifhcieht after I111- directly the impurities occurring through the reactions; merous measurements, was determined experimentally by among these impurities which retard the reactions, amthe applicant and found to be equal to 12.
  • the formula mania gas is by far the most injurious.
  • the blocking means for the fan or of the turbine can, in accordance with the invention, be placed optionally over the entry or outlet orifice of the turbine, and can be operated externally by a device passing through the base of the bell.
  • the present invention also aims at a device for carrying outthe method described above.
  • the deviceforming the object of the present invention is essentially characterised in that the open coil annealing furnace has a device making it possible to block the entry or the outlet of the turbine, and also the forced circulation of gases through the spirals of the coils using only the feed pressure.
  • the open coil annealing furnace has a device making it possible to block the entry or the outlet of the turbine, and also the forced circulation of gases through the spirals of the coils using only the feed pressure.
  • a heat exchanger between the entry and the outlet of the gases.
  • device can also have a circuit for the recovery of the protective gas used during the cooling period with means for. recycling theseagases after having cooled' them.
  • decarbonising, 'denitrifying and annealing of the method of the invention is carried out as follows:
  • the open coils use-d weigh 10 to 20 tons and have spirals separated by a distance of 2.5 mm. by twisted metal wires.
  • a first open coil 5a is disposed on the base 6 of the furnace 1, with its axis 1a vertical, and care being taken that the circular crown formed by the coil coincides with the perforated crown of the base.
  • a second coil 50 is placed on the first coil 5a .
  • the two coils being separated by a wire netting 5b placed above the first coil. It is even possible, the case arising, to arrange a third coil in the same way.
  • the spirals 10 of the coils are not in contact.
  • the content in hydrogen in this gas HNX may be from 5 to 10% and that of nitrogen from 95 to 90%.
  • This HNX gas accumulated in the tank 18 under a pressure of at least 200 mm. water column, is introduced at the rate of 50 m. /hour by opening the valve 15 on the conduit 15a and the valve 17 on the conduit 9; the valves 23 and 16 on the conduits 15b and 16a remain closed.
  • the fan 7 is then set in motion and the furnace heating is set in operation by known means not shown, the flow of the heating flames being shown by the arrows 2 of the'exterior of the bell 3.
  • the gases surrounding the coils, located in the sealing bell 3, arethus put in circulation by the fan 7 and contribute to accelerate theheating of the coils.
  • the gases coming from the fan 7 ascend along the wall of the sealing bell 3, becoming heated, and descend by means of the fan through the spaces between the non-contacting spirals 10, cooling on contact with these.
  • this internal circulation there is imposed the external circulation created bythe supply at 50 mfi/hours of cold HNX gas through the conduit 9 and the outlet of an equivalent amountof hot gases through the outlet pipe 11 and the exchanger 14. At thebeginning of the heating, these gases comprise oil vapours coming from the distilling of the rolling oil covering the coils charged in the furnace.
  • valve 16 is opened and the valve 17 closed, which makes it possible to recover a part of the sensible heat of the gases 14 and heat the gas coming from the tank 18 and passing via the conduits 15a, 16a, 16b and 9 into the furnace.
  • the conduits 9 and 11 have a diameter of approximately 80 mm. in the case where the furnace has a capacity of 50 tons i.e. it is advantageous to have a section of approximately 1.5 cm per ton of coil treated.
  • the exchanger 14 has a heat exchanger surface between 25 and m Then the heating operation proceeds until the coil is at approximately 700 C.
  • the' valve '12 is closed, by actuating the device 13, which interrupts the internal circulation.
  • the supply of HNX gas isstopped, by closing the valve 15, and hydrogen H is introduced from the tank 19 by opening the valve 23 on the conduit 1512.
  • the hydrogen is under a pressure of approximately 300 mm. water column; the rate of flowof'hydrogen is controlled preferably, by means of the valve 16, at 10 mfi/ hour per ton of sheet treated.
  • the total soaking time necessary to obtain the sheet contents of carbon and of nitrogen such that the steel, is no longer ageing (0.003% C and 0.005% N is under these conditions less than the time necessitated by the annealing itself, i.e. for obtaining a grain size of 6 ASTM. In actual fact, this soaking time is generally less than 10 hours. It is, moreover, possible by analysis of the content in NH of the issuing gas to determine the moment when there is no longer denitrification.
  • the rate of flow of HNX gas in the heating can be from 30 to 100 m. /hour
  • the soaking period can be between 6 and 12 hours with a flow of hydrogen of 300 to 1,000 m. /hour, having an amount of steam such that the dew point is between C. and 70 C. whilst the cooling can be carried out by the HNX gas at a flow rate reaching 3,000 mfi/hour.
  • the advantages of the method result from the decrease in the operating time and in the outlay in hydrogen necessary for annealing a ton of sheet. While keeping unchanged the time necessary for the heating, the time necessary for the decarbonisation and denitrification is reduced by more than half, because larger amounts of humid hydrogen can be passed between the spirals of the open coils and because the reactions are facilitated by the rapid removal of the reaction'products. The cooling times are also reduced by half. Concerning the hydrogen its consumption drops from 300 in. per ton, necessary in the open coil furnaces known up to the present,
  • Process of annealing steel plates in open coils as deep drawing plates of mild steel comprising the steps of annealing the plates in a bell furnace at a temperature of about 700 C. during which there is admitted and extracted therefrom a relatively slight flow of protective gas having a base of dry nitrogen admixed with 5 to 10% of hydrogen, the said flows being established between 0.6 and 2 m. per ton of steel treated, there being established both an external circulation and an internal circulation during this step of heating and thereafter soaking said steel at about 700 C.

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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)
US448033A 1961-02-24 1965-04-14 Process and apparatus for annealing thin steel plates Expired - Lifetime US3294596A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
BE600643A BE600643A (fr) 1961-02-24 1961-02-24 Procédé et dispositif pour recuire les tôles fines.

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US (1) US3294596A (de)
AT (1) AT242727B (de)
BE (1) BE600643A (de)
GB (1) GB1011562A (de)
LU (1) LU41089A1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3424444A (en) * 1965-05-06 1969-01-28 Heurtey Sa Bell furnaces for heat-treating coiled strip metal and the like
US4210469A (en) * 1974-07-11 1980-07-01 Nippon Steel Corp. Process of annealing for preventing temper colors on a steel sheet

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2360868A (en) * 1943-01-02 1944-10-24 Carnegie Illinois Steel Corp Manufacture of nonaging steel
GB585921A (en) * 1943-11-22 1947-02-28 Birmingham Electr Furnaces Ltd Improvements in, or relating to, the decarburisation of iron or iron alloy castings
US2746742A (en) * 1949-03-24 1956-05-22 Int Nickel Co Apparatus for producing porous metal plates
US2752148A (en) * 1948-09-08 1956-06-26 Westinghouse Electric Corp Electronic heat treating device
US2998303A (en) * 1958-08-26 1961-08-29 Midland Ross Corp Method for purifying hydrogen contaminated with methane
US3105780A (en) * 1960-09-19 1963-10-01 Gen Electric Method of decarburizing ferrous materials
US3109877A (en) * 1960-07-01 1963-11-05 Wilson Lee Apparatus for modifying the composition of strip metal
US3127289A (en) * 1964-03-31 hoursx

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3127289A (en) * 1964-03-31 hoursx
US2360868A (en) * 1943-01-02 1944-10-24 Carnegie Illinois Steel Corp Manufacture of nonaging steel
GB585921A (en) * 1943-11-22 1947-02-28 Birmingham Electr Furnaces Ltd Improvements in, or relating to, the decarburisation of iron or iron alloy castings
US2752148A (en) * 1948-09-08 1956-06-26 Westinghouse Electric Corp Electronic heat treating device
US2746742A (en) * 1949-03-24 1956-05-22 Int Nickel Co Apparatus for producing porous metal plates
US2998303A (en) * 1958-08-26 1961-08-29 Midland Ross Corp Method for purifying hydrogen contaminated with methane
US3109877A (en) * 1960-07-01 1963-11-05 Wilson Lee Apparatus for modifying the composition of strip metal
US3105780A (en) * 1960-09-19 1963-10-01 Gen Electric Method of decarburizing ferrous materials

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3424444A (en) * 1965-05-06 1969-01-28 Heurtey Sa Bell furnaces for heat-treating coiled strip metal and the like
US4210469A (en) * 1974-07-11 1980-07-01 Nippon Steel Corp. Process of annealing for preventing temper colors on a steel sheet

Also Published As

Publication number Publication date
AT242727B (de) 1965-10-11
BE600643A (fr) 1961-08-24
GB1011562A (en) 1965-12-01
LU41089A1 (de) 1962-03-12

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