EP0195473A1 - Wärmebehandlung von Stahlgegenständen in Wirbelbetten - Google Patents

Wärmebehandlung von Stahlgegenständen in Wirbelbetten Download PDF

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Publication number
EP0195473A1
EP0195473A1 EP86200330A EP86200330A EP0195473A1 EP 0195473 A1 EP0195473 A1 EP 0195473A1 EP 86200330 A EP86200330 A EP 86200330A EP 86200330 A EP86200330 A EP 86200330A EP 0195473 A1 EP0195473 A1 EP 0195473A1
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Prior art keywords
temperature
zone
bed
fluidized
gas
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French (fr)
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EP0195473B1 (de
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Michel Neirynck
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Bekaert NV SA
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Bekaert NV SA
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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
    • C21D9/64—Patenting furnaces
    • 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
    • C21D9/567—Continuous furnaces for strip or wire with heating in fluidised beds

Definitions

  • the present invention relates to the heat treatment of steel in fluidized beds, and particularly but not exclusively to the quenching and subsequent isothermal transformation of wires in a patenting operation.
  • Patenting involves heating carbon steel wires into the austenitic phase, generally above 800°C, and then quenching the wires to a chosen temperature at which the wires are held for a sufficient period for generally isothermal decomposition of the austenite to be completed.
  • the temperature is usually in the region of 550°C, with the intention being generally to provide a fine pearlitic structure.
  • the wires will subsequently be drawn.
  • the wires will be of a plain or alloyed steel with a carbon content of from about 0.1% to more than 1% and preferably in the range of about 0.25% to 1.25%.
  • the wires may be of any cross-section, e.g. square or rectangular, but are preferably common wires with a circular cross-section whose area preferably exceeds 0.15 mm.
  • the term "wire” is intended to extend to e.g. rods, strips and other elongate members.
  • a typical fluidized bed installation comprises a refractory furnace construction with two compartments separated by a fixed horizontal plate.
  • the upper compartment forms a long U-shaped vessel in which inert sand particles (silica, alumina, zirconia, and the like) are fluidized and heated by blowing a hot gas through its horizontal bottom plate which for that purpose possesses a plurality of apertues (i.e. being of perforated or slitted metal) or is made of a porous ceramic material such as asbestos sheets or ceramic plate.
  • the lower compartment below the separating gas distribution plate is the gas plenum chamber from which the fluidizing gas is admitted under pressure to the particle container.
  • the fluidized particulate medium formed of solid particles suspended in a fluidizing gas of adequate velocity (usually between 8 and 15 cm per second for an average particle dimension ranging from 150 to 500 micrometer), behaves nearly like a liquid heat transfer medium and possesses an elevated heat transfer coefficient which is situated between that of forced air cooling and molten lead.
  • the temperature band over which fine pearlite structures can be obtained reliably is relatively narrow and for the optimum microstructures is narrower still.
  • the temperature variations may extend over a range comparable with or larger than these preferred bands. If the temperature of the fluidized bed is set sufficiently low for the soaking temperature to be acceptable, taking into account the exothermic nature of the transformation, then there will be a risk of under- cooling during the quenching stage and undesirable formation of bainite. If the bed temperature is increased to avoid this problem, then there is a risk of overheating during the transformation stage and undesirable formation of coarse pearlite.
  • the present invention aims to solve at least some of the problems associated with known fluidized bed techniques.
  • Apparatus in accordance with the invention is characterized by means for supplying heated fluidizing gas to the first fluidized bed zone and means for controlling independently the temperatures of the first and second zones.
  • the temperature of the second zone can be chosen, and the heat input controlled, to provide the desired microstructure without interfering with the quenching temperature in the first zone, and vice-versa.
  • the provision of a heated fluidizing gas will make it possible to ensure that the total heat input, including that from the wires being treated, is such that the temperature of the wires does not drop below a critical level at which formation of bainite is promoted.
  • This will be of particular advantage in the case of thin wires where the heat stored by the wires is not as great as with thicker wires.
  • lamellar microstructures are desired but it may be necessary to ensure that the wire temperature does not rise to a level at which coarse pearlitic structures are obtained in preference to fine structures. This can be achieved by providing separately controllable cooling means in the first fluidized bed zone. The balance obtained between the heat input and cooling means makes it easier to maintain a desired temperature.
  • These cooling means could comprise immersed cooling tubes with a fixed or preferably regulated water flow rate, or a regulatable water spray, or more preferably air cooling of the fluidized bed surface.
  • the temperatures of the two zones will be similar although the respective heat inputs will be controlled independently to take into account the different conditions and requirements.
  • the improved control over the second zone which is thus made possible, permits the soaking temperature to be maintained at a more constant level and this further improves the microstructures which can be obtained.
  • Another problem with prior art fluidized bed systems is reduced. Coupled with the possibilities of controlling the wire cooling and the transformation start conditions, significant improvements are obtained.
  • the two fluidized bed zones could be provided by two separate fluidized beds with independently controlled fluidization.
  • a single fluidized bed could be divided into two zones. Whilst these two zones would be fluidized by a single source of hot gas, at least one zone would be provided with independently controlled auxiliary heating and/or cooling means.
  • the quenching zone could be provided with cooling means such as those mentioned above and/or the soaking zone could be provided with heating means, depending on the basic temperature of the hot gas.
  • a process for heat treating steel elements by passing them through a single fluidized bed which is fluidized and heated by a source of hot gas is characterized in that the temperatures of separate zones of the bed are controlled by independently controlled auxiliary heating and/or cooling means.
  • a hot gas heated fluidized bed is characterized by the provision of independently controlled auxiliary heating and/or cooling means for controlling the temperatures of separate zones of the bed.
  • auxiliary cooling means In the context of the two zone fluidized bed used e.g. in patenting as described above, it is not generally necessary for the soaking zone to have auxiliary cooling means, whilst it may be advantageous to have auxiliary heating means.
  • electric resistance heaters are immersed in successive soaking bed sections. These could be replaced by immersed radiant tube heaters. With such arrangements, the base heat input from fluidizing gas, i.e. its inlet temperature, is set fairly low and the auxiliary heaters relied upon to bring the bed to the required tempo rature.
  • regulation of the inlet tempera ture of the fluidizing gas for either zone can use lean to extra lean mixtures, mix cooling air with the combustion gas, or provide a regulate heat exchanger between the plenum and the conbustor.
  • a fluidized bed soaking zone contains, in its longitudinal direction, a number of distinct heat transfer and control compartments, making it possible to adapt locally the energy balance resulting from work load heat, from the heat input by primary fluidization and by auxiliary heaters and from cooling and ambient heat losses, thereby enabling momentarily an improved accuracy of local bed temperature, which temperature can be kept constant over the entire soaking bed length or can be programmed to impose and maintain a predetermined profile from soaking zone entry to exit.
  • step patenting could be undertaken.
  • the quench temperature is lower, e.g. 400°C, whilst still above Ms, and this is followed by rapid heating to the selected transformation temperature.
  • Gradient patenting could also be undertaken by quenching and then transforming through a chosen temperature gradient using separate temperature control of various zones of a fluidized bed.
  • the apparatus could also be used in other processes altogether, such as the formation and subsequent tempering of martensite to produce hard structures. In such processes, the quench temperature will be below Ms. Other possible processes are precipitation hardening, quench hardening and so forth.
  • the pearlite reaction commences at a low temperature level such as 540-560°C and continues to a given degree. This initiates formation of fine sorbite. Thereafter, and e.g. after 10-20% transformation the remaining austenite is decomposed at a higher temperature level such as 600-650°C or more. Thus, the cementite growth rate is significantly slower. It is therefore possible to create fine structures, with a small interlamellar distance, without the growth defects encountered with fine pearlites reacted isothermally at higher rates (i.e. at constant lower temperatures).
  • Wires produced in this manner have improved drawability and strength properties.
  • the fluidized bed apparatus and method of the preferred embodiments allow the selection of any convenient cooling-transformation curve in the T.T.T-diagram or the carrying out of a patenting treatment according to a specific curve, e.g. to obtain special effects or particular wire properties. This is not known with common fluidized bed plants nor with lead baths.
  • reaction could start at 580 to 600°C and the wires could be allowed to increase in temperature by the effects of the transformation heat (with temperature rises up to 60-8D°C). Although the wire strength is less, the wire has good deformation properties.
  • the invention provides an improvement in a process for heat treating of steel in which steel from an austenitizing furnace is quenched in a fluidized bed, the improvement being characterized in that the bed is fluidized by substantially non-oxidising exhaust gases from the austenitizing furnace.
  • Apparatus for heat treating steel in accordance with this aspect of the invention comprises an austenitizing furnace and a quenching fluidized bed, and is characterized in that means are provided for supplying exhaust gases from the furnace to the bed so as to fluidize the bed.
  • the exhaust gases can be passed through both zones, either by fluidizing a single bed divided into zones, or by being passed through two separate beds. In the latter case, the exhaust gases may pass sequentially through the two beds.
  • the exhaust gas preferably has an oxygen content of 5% by volume or less and preferably no more than 2% with a target of 1% maximum.
  • the content is not more than 0.5% or most preferably 0.1 or 0.2%, with a residual carbon monoxide content of not less than 0.1% and preferably in the range of 0.5 to 2%.
  • the hot exhaust gas is pre- cooled in a recuperator, e.g. a waste heat boiler, to a level not exceeding 150°C and subsequently heated to the desired input temperature.
  • a recuperator e.g. a waste heat boiler
  • the inlet temperatures may vary from 100-150°C to 450-500°C according to the operational stage (i.e. the highest temperature is required at start up) and the wire diameter.
  • a separate fluidizing gas make-up station is preferably located outside of the basic fluidized bed enclosure.
  • a modular and flexible construction as described in U.K. patent application No. 84.26455 although this choice is not essential for putting the various aspects of the invention into effect.
  • a preferred construction comprises a main steel- backed refractory enclosure, forming a tunnel-like space coveed by a removable or liftable roof, in which at least two separate fluidized bed modules (without incorporated burners) are disposed, respectively a quenching module and one or more soaking modules.
  • a distinct module is preferably made in the form of a two-chamber metal assembly comprising an open vessel for containing the particles and an adjacent gas plenum chamber underneath separated from the particle vessel by a gas distribution bottom place (with apertures and/or nozzles for admittance of fluidizing gas) and is further improved in that the module parts are integrated in a distinct one-piece assembly.
  • Such modular design in which combustion heaters are absent, is advantageous in terms of exploitation and maintenance : the individual zone modules are easily mounted in the apparatus enclosure, and if needed, they can be detached from the main frame (such as e.g. for repair) and replaced by other modules.
  • the soaking zone may comprise one fluidized bed module of suitable length, or a number of smaller modules linked together if a soaking zone of considerable length is desired.
  • Admittance of fluidizing gas to the soaking zone with one or more modules can be by means of a central inlet from a soaking gas station to a common plenum duct extending below the adjoining plenum chambers.
  • each zone is equipped with its own fluidization circuit and integrated heat control system. Accordingly the separate quench zone and the soaking zone are individually fluidized by means of suitable gas mixtures prepared (at a regulable base temperature) outside the apparatus in the gas make-up station of each zone, and there are independent heat input regulation and bed temperature control systems.
  • suitable gas mixtures prepared (at a regulable base temperature) outside the apparatus in the gas make-up station of each zone, and there are independent heat input regulation and bed temperature control systems.
  • Such an integrated system per zone is effective in practice with respect to starting and operating a fluidized bed line.
  • it allows the use of an appropriate gas mixture in each zone and preferably a non-oxidizing gas in the quench zone for scale-free cooling the hot wires.
  • a lead (Pb) and a prior art fluidized bed (FB) patenting line whereby a wire material W, after heating in an austenitization furnace 1 enters a lead bath 2', or a FB-apparatus 2 of usual single zone construction, kept at a constant temperature by suitable means (not shown).
  • Figs. lb and 2b depict the changes in wire temperature as a function of time from the austenitizing temperature (Ta) until the patenting holding temperature (Tp) in both cases.
  • Tq schematizes the course of wire temperature during quenching. From a comparison of Figs. lb and 2b it clearly appears that in a conventional FB-apparatus transformation start and real wire transformation temperatures shown by curve T and the shading considerably depart from the preferred temperature (Tp), and that the pearlite reaction may occur over a broad range of temperatures. These tend to rise excessively during reaction progress, due to the combined effect of wire recalescence (heat release by transformation) and of the lower heat transfer and heat capacity of a fluidized bed.
  • Fig.3 the wire cooling-transformation curves (FB) obtained .by conventional fluidized bed patenting are represented in a T.T.T. diagram in comparison with lead patenting (Pb).
  • the dashed curves (TR) and (TR) 100 indicate start and end of austenite transformation, and the shaded area (OTB) illustrates the optimum transformation band for obtaining a fine pearlitic structure.
  • OTB shaded area
  • Fig. 4a a general embodiment of the present invention is schematized.
  • These zones each contain a modular assembly. 3, comprising essentially a particle container 4, a plenum chamber 5, a gas distribution plate 6 (such as a perforated plate, preferably with gas pipes or nozzles) which links the container bottom and the plenum upper part, and a gas admittance duct 5' connected to the plenum bottom.
  • a gas distribution plate 6 such as a perforated plate, preferably with gas pipes or nozzles
  • a (desirably detachable) pipe connection 8 joins each module to the gas supply duct of a fluidizing gas make-up station 7 (not shown here in detail) where the required gas (in terms of volume and composition) is prepared at a regulable base temperature.
  • This base temperature is determined for each zone according to wire type and selected process and is adjusted-during processing according to the prevailing bed conditions related e.g. to start-up or running, change of wire diameter, etc.
  • possible installations are gas generators, suitable make-up burners supplying a (preferably lean) combustion mixture, forced air heaters and combinations thereof.
  • the two zones Q and TR-S are separated by a heat insulating wall suitably apertured to permit the passage of wires.
  • the apparatus is designed to handle a number of wires travelling in straight and parallel paths. The wires may pass through a protective hood or the like from the furnace 1 to the quench zone Q.
  • Fig. 4b there is shown an alternative embodiment of a two-zone fluidized bed, in which austenitizing furnace exhaust gas is employed for fluidizing first the soaking zone and next the quench zone (or vice-versa when using precooled furnace exhaust gas).
  • austenitizing furnace exhaust gas is employed for fluidizing first the soaking zone and next the quench zone (or vice-versa when using precooled furnace exhaust gas).
  • the exhaust gas from austenitization furnace 1 is fed by pipe 8 to the fluidized-bed apparatus 2 by means of an extraction-blower 7 1 .
  • Base temperature adjustment of the gas, before its admittance to the soaking and quench zone modules, is carried out by means of individual appropriate heat exchangers 10 and 10 1 , located at the entry of each zone.
  • Fig. 5a illustrates a preferred embodiment which is particularly advantageous.
  • a gas fired austenitizing heating furnace 1 and a two-zone fluidized bed 2 with separate quench and soaking modules Q and TR-S in which the quench zone is fluidized by means of (preferably non-oxidizing) furnace exhaust gas 8 whereas the soaking zone TR-S is equipped with an independent gas generator 7, for example a suitable combustor (e.g. a make-up burner).
  • the fluidizing base temperature at the quench zone inlet is preferably controlled as follows.
  • the extracted furnace exhaust gas is precooled, preferably to below 150°C, in a furnace heat recuperator 11, and then it is blown to a regulable heat exchanger 12 (for example an electrical gas heater) to adjust actual gas temperature to an instantly required inlet temperature level which may vary according to momentarily prevailing heat conditions inside the quench bed depending on operational regime, heat input from hot wires, throughput speed, etc.
  • a regulable heat exchanger 12 for example an electrical gas heater
  • the primary adjustment of quench gas inlet temperature is supplemented by a secondary control system for accurately regulating the temperature inside the quench bed to maintain any desired present value.
  • the secondary control system takes over completely once full time running operation is fully established, that is when additional heat input from the fluidizing gas is no longer demanded and the quench gas preheating battery can be switched-off. This will be described in more detail below.
  • the soaking zone TR-S is fluidized and heated by means of hot gas derived from station 7, e.g. a make-up combustor, which supplies a gaseous combustion mixture at a given base temperature to the soaking zone module.
  • the gas inlet temperature level needed for heating and holding the soaking bed at a constant present (average) temperature, is automatically adapted as a function of actual soaking bed heat balance (work load, recalescence, heat losses, etc.).
  • both the quench and soaking bed are individually fluidized, heated and temperature controlled in such a way as to maintain a constant bed temperature, which is characteristic for each zone and is adapted according to the wire and desired properties for a given process.
  • the internal quench bed temperature may be varied from 250 to 600°C (to obtain a wire temperature between Ms and a given pearlite reaction temperature), while in the soaking zone the preset temperature can be selected within a range from 450 to 700 °C (to obtain a pearlitic structure of variable fineness).
  • Fig.. 5b shows a set of wire cooling-transformation curves obtained on wire patenting by means of an apparatus and process of preferred embodiments of this invention (curves FB-IN) as compared to prior art fluidized bed patenting using a single zone (curves FB-PA).
  • curves FB-IN correspond to a much more closely controlled patenting treatment than possible with the prior art process, given the better adjustment of wire cooling and transformation start conditions combined with a more precise control of pearlite reaction temperature.
  • the local bed temperature may have a tendency to rise at some places above the optimum level at a given transformation stage owing to the previously mentioned recalescence effect (release of transformation heat). From experiments we have found that the degree of recalescence and the location of its temperature peaking effect in the soaking zone, may vary with wire diameter throughput speed and selected transformation curve.
  • auxiliary heating elements and temperature sensors in the particle bed of the soaking zone module which elements are grouped and operated in a number of distinct zone compartments making up the complete soaking-transformation zone length.
  • the groups are regulated independently by compartment to correct the local soaking zone temperature in combination with the control of primary fluidization heat.
  • the average heat input is divided into a primary and a secondary fraction, with the primary fraction being deliberately chosen below the constant running heating needs.
  • the auxiliary heaters not only deliver the necessary power to compensate for local heat deficiency, but also a part of the primary heat.
  • An additional advantage of this measure is the possibility of having a programmed pearlite reaction, e.g. in steps of different temperature levels and reaction speeds. This has several advantages in practice, such as increased flexibility to carry out patenting right on target (possibly even better than lead patenting), the ability to control the patenting reaction beyond the usually adopted cooling-transformation curves and better productivity in terms of apparatus used due to shorter start-ups and a quicker transition to desired regime operation.
  • Fig. 6 illustrates how the optimum reaction temperature may be precisely adjusted during transformation progress according to the above principles, on a wire W.
  • the soaking bed TR-S has been divided into a number of sections 13 each of which comprises a set of individual heating elements 14 inside the fluidized bed, a suitable temperature sensor 16 and a heating power regulator 17, connected to a control panel 15.
  • the heating elements are operated at a given base power to keep the soaking bed at a preset temperature, in combination with the heat input of the hot fluidizing gas supplied by the soaking bed gas make-up station. They are further actuated in an increasing or decreasing power sense when local bed temperature drops below or exceeds the prescribed soaking temperature.
  • the heating and fluidizing gas make-up station is disposed outside the main apparatus enclosure.
  • the station is here essentially a combustion device, arranged to prepare a combustion gas mixture at desired rate, temperature and pressure, and comprises a combustion chamber 20 and a gas burner 21 with supply of preferably gaseous fuel 23 (e.g. natural gas) and forced air 22 from blower 7.
  • gaseous fuel 23 e.g. natural gas
  • the gas inlet temperature is fed by line 18 to panel 15.
  • the gas for the quench zone Q e.g. pre-cooled from a furnace, passes through a heater 12.
  • Fig. 7 illustrates the effect of additional temperature correction within the soaking zone on the position of the patenting curves in a T.T.T. diagram.
  • wire transformation temperature or pearlite reaction can be forced entirely into the required optimum OTB-region (curve A), by instant correction of local soaking bed temperature whereas otherwise (curve B), i.e. in the absence of individually regulated bed sections, it could escape to a given extent from the optimum transformation band, resulting in a partially annealed (coarser) pearlitic structure.
  • Fig. 8 shows a more detailed view of a preferred embodiment of a fluidized bed plant utilizing the principles of Fig. 6.
  • Wire W austenitized in a gas fired furnace 1, passes successively through a quench compartment Q and a separate cooling zone TR-S of fluidized bed apparatus 2.
  • the soaking zone contains a number of sections 13 with immersed auxiliary bed heaters and related control devices (depicted in Fig. 6 but not again represented here).
  • the combustion air for burner 21 is preferably preheated and for that purpose fed by a blower 7 over a heat recuperator 24 located in the soaking bed exhaust 25.
  • the prepared fluidizing gas is piped to the soaking zone module TR/S, which is essentially a metallic assembly disposed in the U-shaped inner space of the FB-furnace, in which assembly the particle vessel, plenum chamber and gas admittance duct are integrated.
  • the particle bed 4 contained in vessel 3 is fluidized.
  • a gas plenum 5 with gas admittance duct 5' and a gas distribution device 6 between the vessel bottom and the adjacent plenum which is preferably a perforated plate having a large number of fluidizing nozzles 6' at regular, short distance from each other (for example in the range of 3 to 20 cm).
  • the nozzles receive fluidizing gas from a plenum chamber, the gas admittance duct 5' of which is connected to a supply pipe 9 of the soaking bed make-up 20 and make it possible to obtain and maintain an optimum fluidizing velocity (usually around 10-12 cm per second) and stable bed conditions.
  • Control means for the soaking bed comprise a control device (not shown here) for regulating the make-up combustor 21 to establish and adjust the required soaking gas inlet temperature (primary soaking bed heating and holding at base temperature), and secondary control devices, as explained above in connection with Fig. 6, connected to auxiliary heaters of each soaking zone section to correct the local soaking bed temperature and to augment the base heat input of hot fluidizing gas to the soaking zone (especially useful in starting-up the fluidized bed apparatus).
  • the quench zone Q comprises one fluidized bed module of the same type as described above for the soaking zone, but of shorter length, preferably between 50 and 250 cm.
  • the zone can be fluidized in the same way as the soaking zone, that is by means of a separate external combustion gas make-up station connected to the quench module.
  • the quench gas is derived from the exhaust of the preceding gas fired austenitizing furnace.
  • the composition of the exhaust gas is adapted so as to reduce and even avoid oxidation of the hot wires during quenching.
  • the exhaust gas mixture entering the quench module has an oxygen content of max. 2 vo1 X, and preferably not more than 0.5% to slow down or prevent undesirable surface oxidation. More specifically the oxygen content is preferably limited to 0.1% max. for oxidation free quenching, in combination with a small amount of CO of between 0.5 and about 2% to ensure that oxidation free conditions are met. In the latter case, energy consumption is slightly increased due to non- stoichiometric combustion in heating furnace.
  • An extraction-blower 8' supplies exhaust gas which passes through a precooler or exhaust heat recuperator (not shown) to lower the gas temperature, and a regulable electrical gas heater 12 allowing the fluidizing gas to be supplied to the quench zone at any required inlet temperature level.
  • the primary control contains a control device 34 which regulates power supply 36 of preheater 12 as a function of quench bed temperature and inlet temperature supplied by lines 33 and 35.
  • Additional cooling and bed control means are provided to adjust and to maintain a preset temperature inside the quench bed during constant running operation, that is when the heat input of the hot wires largely exceeds the heat removal capacity of the fluidized quench bed with inlet gas preheater switched off.
  • These supplementary cooling means comprise fixed bed cooling means such as immersed water coils (not shown) and regulable bed cooling means.
  • the latter comprises a blower 28 which directs a variable amount of cooling air from a source 29 through pipe 26 onto the surface of the quench bed or even inside the bed.
  • a motorized valve 27 adjusts the rate of cooling air by means of the suitable control system 34 to which it is connected by line 30.
  • the control system 34 measures actual bed temperature by means of sensor 33, compares it with the quench bed temperature and accordingly regulates the motorized valve of the cooling air supply.
  • regulable water cooling may be used with heat exchanging coils (pressurized water or boiling water) located inside the particle bed, a variable water flow rate being obtained by means of a motorized control valve.
  • the quench zone will be adjusted and maintained at a temperature within a range from 250 to 650°C, preferably from 350 to 550°C for a quench length of 0.5 to 2.5 m and the soaking zone temperature will be adjustable within a range from 450 to 700°C, and preferably a range from 500 to 650°C.
  • the controls of the various heating and cooling means described above are preferably automatic.
  • a FB-patenting line of 36 wires was equipped with two-zone fluidized bed apparatus in accordance with the invention comprising a quench zone of 1.5m and a soaking zone of 5.5m length, each with individual temperature settings.
  • the quench zone was fluidized with different gas mixtures.
  • the FB-patented wire results were compared to those of lead patented wire, isothermally transformed at 560 °C.
  • Wire properties are tabulated below : It can be seen that the properties and microstructure of patented wire obtained according to the invention are close to lead patented wire, except in case of (less controled) hot air for quenching. The beneficial effect of using a non-oxidizing quench gas on wire surface oxidation is clearly recognizable.
  • Preset temperature quench zone 550°C soaking zone 520°C
  • Fig. 10 schematically shows a variety of patenting modes which can be selected and carried out correctly when using two-zone fluidized in accordance with the invention including distinct soaking-zone control compartments.
  • curves 1 and 2 illustrate FB-patenting at two different temperature levels
  • curve 3 illustrates FB-patenting with transformation start at a first temperature and transformation progress and finish at a selected higher temperature which can be imposed from any transformation fraction (TR) x onwards (3a, 3b, 3c).
  • Curve 4 is an example of step patenting with austenite undercooling before rapid heating to a suitable temperature for isothermal transformation to pearlite.
  • a special adaptation relates to continuous martensitic hardening of steel wire by means of a two-zone fluidized bed, which for that purpose is provided with an adapted quench zone for deep cooling, making it possible to carry out a soft quench to below Ms (martensite start temperature) without intersecting the pearlite nose of the T.T.T.-curve, the quench zone being long enough or, if needed, there being and additional cold bed module, to ensure complete transformation of austenite to martensite before entering the soaking zone, where martensite is to be tempered at a preset holding temperature.
  • Ms martensite start temperature
  • An arrangement for patenting steel wires may use apparatus with only one common particle immersion bed which is fluidized by a gas mixture (supplied from furnace exhaust or make-up burner) at a de- lierately chosen "low"base temperature.
  • the immersion or module length is then subdivided in a number of separate control sections in which the first section, used for quenching, is further equipped with fixed cooling as well as with regulable cooling means to remove the excess quenching heat.
  • the second and following module sections, forming the proper transformation zone are provided with regulable internal heaters of sufficient power for establishing and maintaining a prescribed transformation temperature.
  • the fluidized bed hardware is integrated in one modular construction whereas the heat control and temperature compensation devices form two independant systems, resp. for quenching and for transformation or soaking.

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  • Crucibles And Fluidized-Bed Furnaces (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Heat Treatments In General, Especially Conveying And Cooling (AREA)
  • Coating With Molten Metal (AREA)
  • Furnace Charging Or Discharging (AREA)
EP86200330A 1985-03-04 1986-03-04 Wärmebehandlung von Stahlgegenständen in Wirbelbetten Expired EP0195473B1 (de)

Priority Applications (1)

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AT86200330T ATE48444T1 (de) 1985-03-04 1986-03-04 Waermebehandlung von stahlgegenstaenden in wirbelbetten.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8505491 1985-03-04
GB858505491A GB8505491D0 (en) 1985-03-04 1985-03-04 Heat treatment of steel

Publications (2)

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EP0195473A1 true EP0195473A1 (de) 1986-09-24
EP0195473B1 EP0195473B1 (de) 1989-12-06

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EP (1) EP0195473B1 (de)
JP (1) JPS61276938A (de)
KR (1) KR930009977B1 (de)
CN (1) CN86101334A (de)
AT (1) ATE48444T1 (de)
AU (1) AU591652B2 (de)
BR (1) BR8600916A (de)
CA (1) CA1270427A (de)
CZ (1) CZ281967B6 (de)
DD (1) DD250550A5 (de)
DE (1) DE3667301D1 (de)
ES (1) ES8703528A1 (de)
GB (1) GB8505491D0 (de)
IN (1) IN166412B (de)
SK (1) SK280378B6 (de)
SU (1) SU1500167A3 (de)
TR (1) TR22844A (de)
ZA (1) ZA861595B (de)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0329611A1 (de) * 1988-02-09 1989-08-23 Battelle Memorial Institute Verfahren zum kontinuierlichen Überziehen von strangförmigen Stahlmaterialien beim Hindurchführen durch eine Schmelze aus dem Überzugsmaterial
EP0410501A1 (de) * 1989-07-26 1991-01-30 N.V. Bekaert S.A. Wirbelbett zum Abschrecken von Stahldrähten
GB2246793A (en) * 1990-08-04 1992-02-12 Tyne Tees Trans Tech Limited Deposition employing fluidised bed
EP0620284A2 (de) * 1993-04-12 1994-10-19 The Goodyear Tire & Rubber Company Verfahren zum Herstellen von patentiertes Stahldraht
FR2717825A1 (fr) * 1994-03-22 1995-09-29 Hellio Herve Yves Installation de refroidissement contrôlé pour le traitement thermique de pièces métalliques.
EP1078994A2 (de) * 1999-08-27 2001-02-28 Graf + Cie Ag Verfahren und Vorrichtung zum Herstellen von Feindraht
EP1520741A3 (de) * 2003-10-03 2007-03-07 Nippon Steel Corporation KFZ-Verstärkungselement, insbesondere Seitenaufprallträger
WO2008009009A2 (en) * 2006-07-14 2008-01-17 Thermcraft, Inc. Rod or wire heat treatment system, related methods, and related products
CN113502436A (zh) * 2021-06-30 2021-10-15 江苏省沙钢钢铁研究院有限公司 塑料模具钢板的生产方法及塑料模具钢板
EP4109087A1 (de) * 2021-06-21 2022-12-28 NV Bekaert SA Vorrichtung zur inline-überwachung von bei raumtemperatur mikrostrukturschwankungen

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Publication number Priority date Publication date Assignee Title
CN1311088C (zh) * 2002-01-18 2007-04-18 王新辉 用风对钢丸进行热处理的方法及其流化床装置
KR100591355B1 (ko) * 2002-03-25 2006-06-19 히로히사 타니구치 핫가스 담금질 장치 및 핫가스 열처리방법
US8506878B2 (en) 2006-07-14 2013-08-13 Thermcraft, Incorporated Rod or wire manufacturing system, related methods, and related products
CN101333593B (zh) * 2008-07-25 2010-06-30 张家港市东航机械有限公司 钢帘线钢丝淬火流化粒子炉中的低位返砂器
BR112013015116B1 (pt) * 2010-12-23 2019-03-19 Nv Bekaert Sa Processos para fabricar um fio de aço, uso, e, instalação para fabricar um fio de aço
CN104263899B (zh) * 2014-10-14 2016-06-29 海城正昌工业有限公司 一种细钢丝正火工艺及装置

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FR1541674A (fr) * 1966-05-07 1968-10-11 Schloemann Ag Procédé de réalisation de fil d'acier patenté à partir de la chaleur de laminage et dispositif pour la mise en oeuvre de ce procédé
DE2032643A1 (de) * 1969-07-02 1971-01-14 USS Engineers and Consultants, Inc , Pittsburgh Pa (V St A ) Verfahren und Vorrichtung zum Ab schrecken von Stahldraht und dergl
FR2066203A5 (de) * 1969-10-17 1971-08-06 Centre Nat Rech Metall
US3666253A (en) * 1969-12-26 1972-05-30 Yuri Yoshio Fluidized bed furnace
US3718024A (en) * 1971-02-12 1973-02-27 Morgan Construction Co Apparatus including a fluidized bed for cooling steel rod through transformation
US4168995A (en) * 1973-04-20 1979-09-25 December 4 Drotmuvek Steel wire patenting process

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JPS5135611A (ja) * 1974-09-20 1976-03-26 Nippon Steel Corp Senzainorenzokunetsushorihoho
JPS5137013A (ja) * 1974-09-24 1976-03-29 Nippon Steel Corp Senzainorenzokunetsushorisochi
JPS5835580B2 (ja) * 1979-01-26 1983-08-03 大阪瓦斯株式会社 パテンテング装置
JPS5655238A (en) * 1979-10-11 1981-05-15 Mitsubishi Rayon Co Ltd Manufacture of injection-molded product having pearl-like surface luster
GB8426455D0 (en) * 1984-10-19 1984-11-28 Bekaert Sa Nv Fluidised bed apparatus
KR940001357B1 (ko) * 1991-08-21 1994-02-19 삼성전관 주식회사 평판 표시장치

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1541674A (fr) * 1966-05-07 1968-10-11 Schloemann Ag Procédé de réalisation de fil d'acier patenté à partir de la chaleur de laminage et dispositif pour la mise en oeuvre de ce procédé
DE2032643A1 (de) * 1969-07-02 1971-01-14 USS Engineers and Consultants, Inc , Pittsburgh Pa (V St A ) Verfahren und Vorrichtung zum Ab schrecken von Stahldraht und dergl
FR2066203A5 (de) * 1969-10-17 1971-08-06 Centre Nat Rech Metall
US3666253A (en) * 1969-12-26 1972-05-30 Yuri Yoshio Fluidized bed furnace
US3718024A (en) * 1971-02-12 1973-02-27 Morgan Construction Co Apparatus including a fluidized bed for cooling steel rod through transformation
US4168995A (en) * 1973-04-20 1979-09-25 December 4 Drotmuvek Steel wire patenting process

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENTS ABSTRACTS OF JAPAN, vol. 1, no. 54 (C-77) [497], 25th May 1977, page 497 C 77; & JP - A - 52 16 414 (SHIN NIPPON SEITETSU K.K.) 02-07-1977 *

Cited By (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0329611A1 (de) * 1988-02-09 1989-08-23 Battelle Memorial Institute Verfahren zum kontinuierlichen Überziehen von strangförmigen Stahlmaterialien beim Hindurchführen durch eine Schmelze aus dem Überzugsmaterial
CH675257A5 (de) * 1988-02-09 1990-09-14 Battelle Memorial Institute
US5705228A (en) * 1988-02-09 1998-01-06 Battelle Memorial Institute Method for the continuous coating of a filiform steel substrate by immersion of the substrate in a bath of molten coating metal
EP0410501A1 (de) * 1989-07-26 1991-01-30 N.V. Bekaert S.A. Wirbelbett zum Abschrecken von Stahldrähten
BE1004383A3 (nl) * 1989-07-26 1992-11-10 Bekaert Sa Nv Wervelbed voor het afschrikken van staaldraad.
GB2246793B (en) * 1990-08-04 1994-09-21 Tyne Tees Trans Tech Limited Deposition employing fluidised bed
GB2246793A (en) * 1990-08-04 1992-02-12 Tyne Tees Trans Tech Limited Deposition employing fluidised bed
KR100312438B1 (ko) * 1993-04-12 2001-12-28 스위셔 케드린 엠 패턴팅된강선의제조방법
EP0620284A3 (de) * 1993-04-12 1995-05-17 Goodyear Tire & Rubber Verfahren zum Herstellen von patentiertes Stahldraht.
TR27825A (tr) * 1993-04-12 1995-08-29 Goodyear Tire & Rubber Dönüstürülmüs celik tel üretimi icin bir islem.
EP0620284A2 (de) * 1993-04-12 1994-10-19 The Goodyear Tire & Rubber Company Verfahren zum Herstellen von patentiertes Stahldraht
FR2717825A1 (fr) * 1994-03-22 1995-09-29 Hellio Herve Yves Installation de refroidissement contrôlé pour le traitement thermique de pièces métalliques.
EP1078994A2 (de) * 1999-08-27 2001-02-28 Graf + Cie Ag Verfahren und Vorrichtung zum Herstellen von Feindraht
EP1078994A3 (de) * 1999-08-27 2003-05-28 Graf + Cie Ag Verfahren und Vorrichtung zum Herstellen von Feindraht
EP1520741A3 (de) * 2003-10-03 2007-03-07 Nippon Steel Corporation KFZ-Verstärkungselement, insbesondere Seitenaufprallträger
US7648191B2 (en) 2003-10-03 2010-01-19 Nippon Steel Corporation Automobile strength member
WO2008009009A2 (en) * 2006-07-14 2008-01-17 Thermcraft, Inc. Rod or wire heat treatment system, related methods, and related products
WO2008009009A3 (en) * 2006-07-14 2008-05-15 Thermcraft Inc Rod or wire heat treatment system, related methods, and related products
EP4109087A1 (de) * 2021-06-21 2022-12-28 NV Bekaert SA Vorrichtung zur inline-überwachung von bei raumtemperatur mikrostrukturschwankungen
WO2022268507A1 (en) * 2021-06-21 2022-12-29 Nv Bekaert Sa Device for in-line monitoring the room temperature microstructure variations
CN113502436A (zh) * 2021-06-30 2021-10-15 江苏省沙钢钢铁研究院有限公司 塑料模具钢板的生产方法及塑料模具钢板

Also Published As

Publication number Publication date
GB8505491D0 (en) 1985-04-03
EP0195473B1 (de) 1989-12-06
DD250550A5 (de) 1987-10-14
SK280378B6 (sk) 1999-12-10
CN86101334A (zh) 1986-11-19
AU591652B2 (en) 1989-12-14
KR860007391A (ko) 1986-10-10
TR22844A (tr) 1988-08-22
KR930009977B1 (ko) 1993-10-13
BR8600916A (pt) 1986-11-11
ATE48444T1 (de) 1989-12-15
AU5389686A (en) 1986-09-11
ZA861595B (en) 1986-10-29
SU1500167A3 (ru) 1989-08-07
JPS61276938A (ja) 1986-12-06
CZ281967B6 (cs) 1997-04-16
CZ149186A3 (en) 1993-02-17
ES8703528A1 (es) 1987-02-16
IN166412B (de) 1990-05-05
CA1270427A (en) 1990-06-19
DE3667301D1 (de) 1990-01-11
ES552641A0 (es) 1987-02-16

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