EP0086331A1 - Ligne de traitement thermique en continu pour bandes ou tôles en acier doux en acier à haute résistance - Google Patents

Ligne de traitement thermique en continu pour bandes ou tôles en acier doux en acier à haute résistance Download PDF

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Publication number
EP0086331A1
EP0086331A1 EP83100217A EP83100217A EP0086331A1 EP 0086331 A1 EP0086331 A1 EP 0086331A1 EP 83100217 A EP83100217 A EP 83100217A EP 83100217 A EP83100217 A EP 83100217A EP 0086331 A1 EP0086331 A1 EP 0086331A1
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Prior art keywords
cooling
strip
zone
tanks
tank
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EP83100217A
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German (de)
English (en)
Inventor
Masao c/o Nippon Steel Corp. Morimoto
Ichiro c/o Nippon Steel Corp. Shimbashi
Kozaburo Yawata Works Nippon Steel Corp. Ichida
Koichi Yawata Works Nippon Steel Corp. Sakurai
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Nippon Steel Corp
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Nippon Steel Corp
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Publication of EP0086331A1 publication Critical patent/EP0086331A1/fr
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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
    • C21D9/573—Continuous furnaces for strip or wire with cooling

Definitions

  • This invention relates to a continuous heat treating line for a cold rolled steel strip or sheet. More particularly, it is concerned with a continuous heat treating line for strips or sheets of various types of steels, including both mild steel (e.g., for deep drawing quality) .and high tensile strength steel.
  • Continuous annealing has recently been replacing inefficient batch annealing for the production of a cold rolled steel strip or sheet.
  • Different continuous annealing processes are available, and classified by the method for primary cooling which is performed after heating and soaking. Two methods are presently in use for primary cooling, i.e., gas jet cooling and water quenching.
  • a typical annealing cycle including gas jet cooling is shown at b 1 in FIGURE 1 for a mild steel strip or sheet, and at b 1 in FIGURE 2 for a high tensile strength steel strip or sheet.
  • a typical annealing cycle including water quenching is shown at b in FIGURE 1 for a mild steel strip or sheet, and at b 2 in FIGURE 2 for a high tensile strength steel strip or sheet.
  • the annealing process including gas jet cooling is disclosed, for example, in Japanese Patent Publication No. 5335/1976, and the annealing process including water quenching in Unexamined Japanese Patent Publication No. 18415/1977.
  • the process employing gas jet cooling gives a strip or sheet cooling rate in the order of 10°C per second, and enables the terminal cooling temperature control in which the cooling of a strip or sheet is stopped at a desired temperature, for example, an overaging temperature. No reheating zone is required before an overaging zone.
  • This process is, therefore, economical from the standpoint of cost for both equipment and energy consumption.
  • the lower cooling rate makes it necessary to employ steel containing larger quantities of alloying elements in order to produce a high tensile strength steel strip or sheet of, particularly, the type having a dual-phase structure for which the demand has recently been increasing. This means a considerable increase in the cost of production.
  • This warm still water dip cooling method is intended for producing a mild steel strip or sheet without reheating it by stopping the cooling of the strip at its overaging temperature (about- 400°C), or producing a high tensile strength steel strip or sheet from steel containing smaller quantities of alloying elements by cooling the strip rapidly at a mild rapid cooling rate.
  • This method presents a problem in connection with the production of a high tensile strength steel strip or sheet.
  • the inflection point of the two-stage cooling according to this method usually resides at a strip temperature of about 300°C. The strip is cooled to that temperature at a relatively slow rate of, say, 40°C per second. During the production of a high tensile strength steel strip or sheet .
  • the warm still water dip cooling method it is essential to employ a bath of warm water having a temperature very close to its boiling point (for example, higher than 90°C) in order to maintain the proper shape of strip.
  • the cooling curve for a strip is determined solely by its thickness, and therefore, its cooling rate and the inflection point of its two-stage cooling are also invariable. This lack of flexibility is undesirable in view of the future requirements expected. to be directed to various types of high tensile strength steel strips or sheets.
  • the inflection point of the two-stage cooling according to the warm still water dip cooling method which corresponds to the transition point from film boiling to nuclear boiling, creates a great difference in cooling rate which is likely to destroy the shape of strip ("Development of Water Quenching Techniques for Cold Rolled Steel Strip", TETSU-TO-HAGANE, Journal of The Iron and Steel Institute of Japan, No. 6, Vol. 62, 1976).
  • the warm still water dip cooling method is not only very advantageous for the production of a high tensile strength steel strip or sheet as compared with the method employing gas jet cooling or water quenching, but also is even likely to result in the failure to obtain a product having a satisfactory shape.
  • the inventors of this invention have thought of the following primary cooling arrangements for the production of both mild and high tensile strength steel strips or sheets:
  • the second stage of cooling for the production of a high tensile strength steel strip or sheet is effected by a kind of warm water cooling system which may also be used for warm still water dip cooling method.
  • a jet is, however, blown against the strip in warm water in order to remove a vapor film uniformly from the strip surface so as to cool the strip in a good shape. If the water in which the strip is dipped has excessively low temperature, it is cooled too rapidly, and must be reheated for tempering as hereinbefore pointed out. It is, therefore, recommended that the strip be cooled under the conditions which will hereinafter be described.
  • the strip may be cooled at a rate of 100°C to 500°C per second, and if cooling is started at a strip temperature of at least 400°C, the strip may be cooled in accordance with a continuous cooling curve not crossing the nose'of the CCT diagram (see curve c in FIGURE 3), and it is possible to produce the strip from steel containing smaller quantities of alloying elements.
  • the cooling curve for the strip is flexible, since the temperature at which the cooling of the strip is started is variable.
  • the first stage of cooling for the production of a high tensile strength steel strip or sheet is effected by dipping the strip in a still bath of warm water having a temperature close to its boiling point so as to maintain the proper shape of strip.
  • the strip is cooled at a not high rate of, say, 20°C to 90°C per second. This cooling rate promotes the diffusion and concentration of carbon, and alloying elements in the austenitic phase of the strip, and thereby facilitates the-martensitic transformation of the strip structure during the second stage of rapid cooling by a jet of warm water.
  • an inflection point of at least 450°C, or preferably at least 550°C for the two-stage cooling in order to achieve a greater reduction in the quantity of alloying elements in the steel. If the temperature is too high, however, the solubility limit of carbon and alloying elements imposes limitations on their diffusion and concentration. Therefore, the inflection point should not be higher than 710°C.
  • FIGURE 1 An approximate annealing cycle for the operation of the equipment according to this invention is shown at a in FIGURE 1 for a mild steel strip or sheet, and at a in FIGURE 2 for a high tensile strength steel strip or sheet.
  • a mild steel strip or sheet can be subjected to overaging treatment - without reheating by the control of the temperature at which the cooling of the strip is stopped, while it is possible to economize the alloying elements in the production of a high tensile strength steel strip or sheet without reheating it by cooling it rapidly at a mild rate to a temperature below the M point.
  • the strip is soaked at a temperature between A 1 and A3 transformation temperatures in a time between 20 seconds and 2 minutes, for recrystallization and grain growth in FIGURE 1 and for initial dual phase formation, in FIGURE 2.
  • the strip During the second-stage of cooling by a jet of warm water, it is necessary to cool the strip so that its temperature may drop below the M s point, as shown by curve c in FIGURE 3.
  • the M point of a high tensile strength steel is usually in the vicinity of 300°C, though it depends on the steel composition. In order to be completely lower than that temperature, the strip must be cooled to a temperature not higher than 200°C.
  • a vertical tank is employed for both the first and the second stages of cooling in order to cool the strip uniformly to ensure its proper shape.
  • a mild steel strip or sheet does not present the problem of an improper shape even if the nozzle may not be used for cooling it, since its cooling is stopped before the strip reaches the inflection transition point of about 300°C from film boiling to nucleate boiling, so that it may later be overaged at a temperature of about 400°C.
  • the warm still water dip cooling of the strip is to be started at a temperature which is sufficiently low for a metallurgical reason and for ensuring the proper shape of the strip, especially when the soaking temperature is rather high. It is, therefore, desirable to cool the soaked strip slowly by using a gas jet cooler, if required, before its cooling by warm still water is started.
  • the strip may be cooled at a rate of 5°C to 30°C per second so that it may have a temperature of 600°C to 800°C when it is dipped in the warm still water tank.
  • a cooling rate below 5°C per second is improper as it calls for an excessively large apparatus, while a cooling rate over 30°C per second should also be avoided, as it is not sufficiently slow from a metallurgical standpoint or for ensuring the proper shape of the strip.
  • a single cooling tank may not be sufficient, but a plurality of warm water tanks may be provided for cooling the strip to a predetermined temperature. In such a case, it is most advisable to ensure that the strip be always kept in warm water, since its temperature control is difficult if it is exposed to the atmosphere during, its travel from one tank to another.
  • a bath temperature control system is provided for the warm water jet cooling tank to control the cooling rate of the strip.
  • a dipping length control system is provided for warm still water dip cooling tank so that the terminal cooling temperature of the strip may be controlled by adjusting the time for which the strip stays in warm water according to the production rate (tons per hour).
  • the apparatus of this invention is usable for producing both mild and high tensile strength steel strips or sheets.
  • a high tensile strength steel strip or sheet may be passed through the overaging zone which has been cooled to ordinary room temperature.
  • the upper level of warm water bath is always covered by a protective atmosphere in order to prevent oxidation of the strip in the air.
  • warm water may be water or an aqueous bath, for example, an aqueous solution of sodium hydroxide. If the latter is used, the strip obtains a bright surface which is free from any oxide film.
  • FIGURE 4 is a diagrammatic representation of a continuous annealing line in which the apparatus of this invention is used.
  • the line includes a pay-off reel 1, a welder 2, a cleaning device 3, an entry looper 4, a heating zone 5, a soaking zone 6 and a primary cooling apparatus 7 embodying this invention.
  • a primary slow cooling zone 6a provided with, for example, a gas jet cooler is sometimes employed between the soaking zone 6 and the primary cooling apparatus 7.
  • An overaging zone 8 is provided after the primary cooling apparatus 7. No reheating zone is required between the primary cooling apparatus 7 and the overaging zone 8.
  • the line further includes a secondary cooling zone 9, a posttreatment device 10, a delivery looper 11, a temper rolling mill 12, a finishing and inspecting section 13, a delivery shear 14 and a coiling reel 15.
  • All the furnaces 5, 6, 6a, 8 and 9 as well as tanks 7 and 10 in the line shown in FIGURE 4 are of the vertical type to save the space for installation.
  • the line is, thus, suitable for the continuous heat treatment of a large quantity of steel strip S at a high speed.
  • the line is a general-purpose line used for producing not only a high tensile strength steel strip, but also a mild steel strip, since it includes the overaging zone 8, the temper rolling mill 12 and the delivery looper 11 having a sufficiently large capacity to allow the exchange of rolls in the temper rolling mill. It is, of course, possible to omit the overaging zone 8, the delivery looper 11 and the temper rolling mill 12 and construct a line used exclusively for the heat treatment of a high tensile strength steel strip or sheet.
  • the primary cooling apparatus 7 may, for example, be constructed as specifically shown in FIGURE 5.
  • the cooling apparatus shown in FIGURE 5 essentially comprises a pair of warm water tanks connected to each other, i.e., a first warm water tank 21 and a second warm water tank 21a.
  • the apparatus also includes devices 22 and 22a for reversing the direction of travel of a steel strip S in the tanks 21 and 21a, respectively (for example, sink rolls), an underwater jet header 23 provided in the second tank 21a along a downward path for strip S, and external rolls 24-1 to 24-4 about which strip S travels into or out of the tanks.
  • the first tank 21 contains an aqueous bath W having a temperature close to its boiling point.
  • the second tank 21a contains an aqueous bath W' maintained at a temperature of at least 60°C, or preferably at most 75°C.
  • the level L' of the bath W' may sometimes be lowered to a level below the strip turning device 22a to enable the strip S to pass through the second tank 21a without contacting the bath W.
  • the second tank 21a When the apparatus is used for producing a mild steel strip, the second tank 21a is emptied, and only the still, nearly boiling bath W in the first tank 21 is used for cooling the strip S until it is cooled to a " predetermined temperature. If the production rate (t/h) is so high that the strip fails to stay in the bath for a sufficiently long time, the second tank 21a may be used together.to provide an increased cooling capacity. In this case, the bath W' in the second tank 21a is maintained at a temperature close to its boiling point, the underwater jet header 23 is not operated, and the dip length control system is operated. Even if the level L' of the bath in the second tank 21a may be fixed, it is possible to control the terminal temperature at which the cooling of the strip is stopped, if the level L of the bath in the first tank 21 is raised or lowered.
  • a high tensile strength steel strip or sheet is cooled in two stages.
  • the first stage of its cooling is effected by the still, nearly boiling bath W in the first tank 21, and the second stage is effected by jets of warm water having a temperature of, say, about 70°C, which are created in the bath W' in the second tank 21a by the underwater jet header 23.
  • the inflection point of such two-stage cooling is usually in the range of 450°C to 710°C to satisfy the metallurgical requirement, and preferably in the range of 550°C to 710°C to economize the alloying elements in the steel.
  • the underwater jet header 23 is provided for directing jets of warm water to the surfaces of the strip S travelling from the guide roll 24-3 to the guide roll 22a.
  • the header 23 is supplied by a jet water supply pump 25 with warm water which may, for example, be obtained from the tank 21a.
  • warm water may, for example, be obtained from the tank 21a.
  • they define an internally recirculated jet system, and the operation of the jet system does not give rise to any change in the level of the bath in the tank but ensures continuously stable operation.
  • An air-shielding hood is provided for each tank and a gas-tight tunnel is put between the soaking zone 6, the first tank 21, the second tank 21a and the overaging zone 8, in order to keep the strip portion above bath level in a protective atmosphere.
  • a throat is provided for each tunnel between the soaking zone 6 and the first tank 21 or between the second tank 21a and the overaging zone 8, so as to prevent any back flow of steam from the tanks.
  • the primary slow cooling zone 6a may be provided between the soaking zone 6 and the primary cooling apparatus 7 if required to maintain the proper shape of the strip, whether it may be of mild or high tensile strength steel (see FIGURE 4).
  • FIGURE 6 A different form of the cooling apparatus is shown in FIGURE 6.
  • This apparatus essentially comprises a pair of warm water tanks 31 and 31a connected to each other by a strip transfer zone provided below the levels of the baths in the tanks.
  • the first tank 31 is a warm still water dip cooling tank provided with an external strip guide roll 34 and a pair of immersed strip guide rolls 32 and 37.
  • the second tank 31a is a warm water jet cooling tank provided with an external strip guide roll 34a, a pair of immersed strip guide rolls 32a and 37a, and an underwater jet header 33.
  • the strip transfer zone 38 is provided with a partition 36 which separates the two tanks 31 and 31a from each other in a liquid-tight fashion.
  • the partition 36 is provided with a pair of vertically juxtaposed pinch rolls 34 defining therebetween a path for the transfer of a steel strip S from the first tank 31 to the second tank 31a.
  • the strip S is introduced past the guide roll 34 into the tank 31, and cooled therein while travelling past the guide rolls 32 and 37. Then, it is transferred into the second tank 31a through the path between the pinch rolls 34, cooled while travelling past the guide rolls 37a and 32a, and transferred past the guide roll 34a into the overaging zone.
  • the cooling apparatus of FIGURE 6 is characterized by the transfer of the strip S from the first tank 31 to the second tank 31a without being exposed to the atmosphere above the level of warm water, and the continued cooling of the strip even during its transfer from the tank 31 to the tank 31a. It is possible to eliminate from a strip cooling curve a "shelf" which would substantially lower the total cooling rate.
  • the warm still water dip cooling tank 31 can employ either adjustable bath level method or movable'sink roll method,, for dip length control system.
  • FIGURE 7 Still another form of the cooling apparatus according to this invention is shown in FIGURE 7.
  • the apparatus essentially comprises three warm water tanks connected to one another.
  • Each of the tanks 41a and 41b is a warm still water dip cooling tank, while the tank 41c is a warm water jet cooling tank.
  • the apparatus of FIGURE 7 is also characterized by the .elimination of any region where the strip is exposed above the warm water, as is the case with the apparatus of FIGURE 6.
  • the tanks are separated from one another only by partitions 46-1 and 46-2, and disposed in close proximity to one another. Only one strip turning roll (deflector roll) 47-1 or 47-2 is provided between every two adjoining tanks. Another roll 48-1 or 48-2 is disposed above each deflector roll, so that they may form a pair of pinch rolls.
  • the strip S is, therefore, cooled in water without being exposed in the atmosphere. It is also possible to eliminate the "shelf" on the cooling curve which would substantially lower the total cooling rate.
  • warm still water dip cooling tanks 41a and 41b can employ movable sink roll method only for dip length control system.
  • the cooling tanks are of the vertical type.
  • the horizontal tanks would not only give rise to an increase in the line length and thereby the cost of equipment, but also be likely to create different cooling results, including formation and removal of bubbles, between the upper and lower surfaces of the strip, resulting in the improper shape of the strip.
  • the control of the terminal temperature to which a mild steel strip or sheet is cooled makes it necessary to adjust the length of the strip portion staying below the level of the bath in the warm still water dip cooling tank.
  • This adjustment may, for example, be achieved by adjusting the level of the bath in the tank, or the position of the underwater strip turning devices, such as sink rolls. If the control of the sink roll position is chosen, there is no change in the length of the strip portion staying above the bath level.
  • FIGURE 8 shows a warm still water dip cooling tank 51, a reservoir 56 disposed below the tank 51, a head tank 52 disposed above the tank 51, a pump 53, and valves 54 and 55.
  • the dip cooling tank 51 has a bath level L which can be lowered if the valve 54 is opened to allow water to fall rapidly by gravity from the tank 51 into the reservoir 56.
  • the water received in the reservoir 56 is raised by the pump 53 into the head tank 52, while the dip cooling tank 51 is still operating with a low bath level.
  • the valve 55 is opened to allow warm water to drop from the head tank 52 into the cooling tank 51 rapidly by gravity.
  • the method utilizing gravity makes it possible to control the length of the dipped strip portion with a high response required for the strip S to travel at a high speed.
  • the jet cooling tank When the jet cooling tank is used for cooling a high tensile strength steel strip or sheet, it is necessary to regulate the bath temperature at a constant level between, say, 60°C and 75°C, as hereinbefore pointed out.
  • FIGURE 9 shows an indirect cooling method.
  • FIGURE 9 shows a warm water dip cooling tank 61, a recirculating pump 62, a heat exchanger 65, an external cooling water line 66, a bath temperature detector 64 and a three-way valve 67.
  • Water is drawn from the tank 61 by the pump 62, delivered to the heat exchanger 65 where it is cooled by the cooling water 66 r and returned into the tank 61.
  • the bath temperature is detected by the detector 64, and the three-way valve 67 is adjusted accordingly to control the quantity of cooling water supplied to the heat exchanger 65.
  • the bath W discharges the heat brought by the strip S thereinto, and maintains a constant temperature.
  • FIGURE 10 shows a warm still water dip cooling tank 71 and a gas jet cooler 72.
  • a strip S is first cooled slowly by the gas jet cooler 72, and then cooled at a predetermined rate by the tank 71.
  • a hood 73 is provided between the gas jet cooler 72 and the first tank 71 so that the strip S may be kept from the open air until it is cooled in the bath W.
  • a throat 74 is provided for preventing any back flow of steam from the tank 71 to the gas jet cooler 72.
  • this invention incorporates into the primary cooling zone of a continuous annealing line a cooling system obtained by an excellent combination of dipping in a still bath-of nearly boiling water and subsequently applying jets of.warm water in a bath of warm water. It realizes cooling which is not excessively rapid, and enables the control of the temperature to which the strip is to be cooled, and two-stage cooling having a variable inflection point.
  • the apparatus of this invention is, therefore, useful in a general-purpose line which can produce both mild and high tensile strength steel strips or sheets, and inexpensive to construct as an apparatus which manufactures products having excellent properties at a low cost.
  • the apparatus enables the use of a flexible annealing cycle which provides .a high potential for the development of new products in the future.
  • the steel composition was basically as follows:
  • This steel was hot rolled into a strip having a thickness of 3.0 mm with a coiling temperature of 725°C. It was pickled, and cold rolled into a thickness of 0.8 mm.
  • the cold rolled strips were continuously annealed by the , continuous annealing apparatus of this invention and the conventional continuous annealing apparatus. They were annealed in accordance with the annealing cycles shown in FIGURE 1 in which curves a, b and b 2 represent this invention, gas jet cooling and water quenching, respectively.
  • the conditions of continuous annealing and the results are shown in TABLE 1.
  • a bath for primary cooling had a temperature of about 98°C in accordance with this invention, and about 40°C in accordance with the conventional method #2 (water quenching).
  • the continuous annealing apparatus of this invention enables the control as intended of the temperature to which the strip is to be cooled, thereby eliminating the necessity for reheating to an overaging temperature as required by the conventional method #2 (water quenching), and permitting the production of cold rolled steel strips for drawing having excellent ductility.
  • This invention does not differ from the conventional method #1 (gas jet cooling) with respect to the control of the temperature to which the strip is cooled.
  • This invention gives a higher cooling rate, and enables cold rolled steel strips for drawing having a comparably excellent degree of formability to be produced at a lower cost in a shorter overaging time.
  • This example was directed to the production of highly formable, high tensile strength steel strips having a dual-phase structure, and a tensile strength in the order of 60 kg/mm 2 .
  • the steel composition was basically as follows:
  • the quantity of Mn was varied according to continuous annealing process as shown in TABLE 2 to achieve a tensile strength of 60 kg/mm2.
  • These steels were hot rolled into a thickness of 2.3 mm at a finish rolling temperature of 890°C and a coiling temperature of 610°C.
  • the hot rolled products were pickled, and cold rolled into a thickness of 0.7 mm.
  • the cold rolled strips were continuously annealed by the continuous annealing apparatus of this invention and the conventional apparatus. They were annealed in accordance with the annealing cycles shown in FIGURE 2 in which curves a, b 1 and b represent this invention, gas jet cooling and water quenching, respectively.
  • the conditions of continuous annealing and the results are shown in TABLE 2.
  • a bath for primary cooling had a temperature of 98°C in the first tank and 68°C in the second tank, and about 40°C in accordance with the conventional method #2 (water quenching).
  • the continuous annealing apparatus of this invention provides cooling which is not excessively rapid, and therefore, enables the elimination of the necessity for reheating for tempering despite the somewhat larger quantity of Mn required, and the production of high tensile strength steel strips having an outstandingly high degree of formability, as opposed to the conventional method #2 (water quenching).
  • This invention provides a higher cooling rate particularly during the second stage of cooling, and therefore, enables a great reduction in the quantities of alloying elements in steels, as compared with the conventional method #1 (gas jet cooling).
  • TABLE 3 shows the comparison with respect to the product properties, production cost and equipment cost. The following is obvious from TABLE 3:
  • the process employing the apparatus of this invention enables the production of a product which is comparable to that of the conventional gas jet cooling process, since this invention does not require reheating before overaging for a mild steel strip (see EXAMPLE 1), nor the reheating of a high tensile strength steel strip for tempering after primary rapid cooling (see EXAMPLE 2), as opposed to the conventional water quenching process.
  • the process employing the apparatus of this invention enables a drastic reduction in the cost of fuel for the production of mild steel strips, since it does,not require reheating prior to overaging, as opposed to the conventional water quenching process.
  • the invention requires a lower cost of electricity than the conventional gas jet cooling process, since it does not require any gaseous coolant recirculating system.
  • the process employing the apparatus of this invention is less expensive than both of the conventional processes when they are compared in the production cost which is the sum of the costs of materials and utilities required for .the continuous annealing line.
  • the process employing the apparatus of this invention enables a reduction in the cost of materials owing to a reduction in the quantities of alloying elements required in steels, and thereby in the cost of production for a high tensile strength steel strip, as compared with the conventional gas jet cooling process.
  • this invention enables a reduction in the cost of fuel as it does not require reheating, but is sometimes likely to be somewhat more costly, since it requires somewhat larger quantities of alloying elements in steels, depending on the grade of the product required, as shown in TABLE 3.
  • the use of the apparatus.according to this invention enables a lower production cost in total than the conventional gas jet cooling process in the production of both mild and high tensile strength steel strips or sheets.
  • the use of this invention is less expensive for the production of mild steel strips or sheets than the conventional water quenching process, but is sometimes likely to be more expensive for the production of high tensile strength steel strips or sheets.
  • This invention is, however, quite often less expensive in total than the water quenching process since high tensile strength steel strips or sheets do not usually occupy a very large proportion in all the steel grades involved.
  • the continuous annealing line according to this invention is considerably less expensive than the equipment required for the water quenching process, since it does not have a costly reheating zone, though its overaging zone is slightly greater in length.
  • the line is substantially equal in equipment cost to the equipment required for the conventional gas jet cooling process, depending on the production capacity, since it includes the posttreating section not required for the conventional process, though it has a shorter overaging zone.
  • this invention provides an apparatus which is useful for carrying out a process which is superior to the conventional gas jet cooling and water quenching processes in any of the product properties, production cost and equipment cost.

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  • Engineering & Computer Science (AREA)
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EP83100217A 1982-01-13 1983-01-12 Ligne de traitement thermique en continu pour bandes ou tôles en acier doux en acier à haute résistance Withdrawn EP0086331A1 (fr)

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JP272982A JPS58120748A (ja) 1982-01-13 1982-01-13 加工用冷延鋼帯および高張力冷延鋼帯の連続熱処理設備
JP2729/82 1982-01-13

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EP0111985A2 (fr) * 1982-12-21 1984-06-27 CENTRE DE RECHERCHES METALLURGIQUES CENTRUM VOOR RESEARCH IN DE METALLURGIE Association sans but lucratif Procédé de refroidissement de bandes métalliques minces
EP0195659A2 (fr) * 1985-03-22 1986-09-24 Kawasaki Steel Corporation Procédé et dispositif pour le refroidissement d'un ruban d'acier dans une installation de recuit en continu
US4729800A (en) * 1985-03-22 1988-03-08 Kawasaki Steel Corporation Method for cooling steel strip
EP0992593A1 (fr) * 1998-10-01 2000-04-12 CENTRE DE RECHERCHES METALLURGIQUES - CENTRUM VOOR RESEARCH IN DE METALLURGIE Ass. sans but lucratif Ver. zonder winstoogmerk Procédé de refroidissement en continu d'une tôle en acier et dispositif pour sa mise en oeuvre
EP1538228A1 (fr) * 2003-12-01 2005-06-08 R & D du groupe Cockerill-Sambre Procédé et Dispositif de refroidissement d'une bande d'acier
WO2010049600A1 (fr) * 2008-10-31 2010-05-06 Siemens Vai Metals Technologies Sas Four pour une installation de traitement thermique d'une bande d'acier en défilement continu et procédé associé

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BE880587A (fr) * 1979-12-12 1980-06-12 Centre Rech Metallurgique Installation de traitement thermique en continu de toles d'acier
GB2054661A (en) * 1979-06-28 1981-02-18 Nippon Kokan Kk Cooling Steel Strip in Continuous Annealing
BE884856A (fr) * 1980-08-20 1981-02-20 Centre Rech Metallurgique Procede et installation de traitement thermique en continu de toles d'acier.
BE887507A (fr) * 1981-02-12 1981-06-01 Centre Rech Metallurgique Perfectionnements aux procedes de traitement thermique en continu de toles d'acier

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US4065329A (en) * 1975-01-17 1977-12-27 Centre De Recherches Metallurgiques-Centrum Voor Research In De Metallurgie Continuous heat treatment of cold rolled steel strip
GB2054661A (en) * 1979-06-28 1981-02-18 Nippon Kokan Kk Cooling Steel Strip in Continuous Annealing
BE880587A (fr) * 1979-12-12 1980-06-12 Centre Rech Metallurgique Installation de traitement thermique en continu de toles d'acier
BE884856A (fr) * 1980-08-20 1981-02-20 Centre Rech Metallurgique Procede et installation de traitement thermique en continu de toles d'acier.
BE887507A (fr) * 1981-02-12 1981-06-01 Centre Rech Metallurgique Perfectionnements aux procedes de traitement thermique en continu de toles d'acier

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Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0111985A2 (fr) * 1982-12-21 1984-06-27 CENTRE DE RECHERCHES METALLURGIQUES CENTRUM VOOR RESEARCH IN DE METALLURGIE Association sans but lucratif Procédé de refroidissement de bandes métalliques minces
EP0111985B1 (fr) * 1982-12-21 1989-03-29 CENTRE DE RECHERCHES METALLURGIQUES CENTRUM VOOR RESEARCH IN DE METALLURGIE Association sans but lucratif Procédé de refroidissement de bandes métalliques minces
EP0195659A2 (fr) * 1985-03-22 1986-09-24 Kawasaki Steel Corporation Procédé et dispositif pour le refroidissement d'un ruban d'acier dans une installation de recuit en continu
EP0195659A3 (en) * 1985-03-22 1987-10-21 Kawasaki Steel Corporation Method and apparatus of cooling steel strip in continuous heat treating line
US4713125A (en) * 1985-03-22 1987-12-15 Kawasaki Steel Corporation Method of cooling steel strip in continuous heat treating line
US4729800A (en) * 1985-03-22 1988-03-08 Kawasaki Steel Corporation Method for cooling steel strip
US4798367A (en) * 1985-03-22 1989-01-17 Kawasaki Steel Corporation Apparatus of cooling steel strip in continuous heat treating line
US4838526A (en) * 1985-03-22 1989-06-13 Kawasaki Steel Corporation Apparatus of cooling steel strip
EP0992593A1 (fr) * 1998-10-01 2000-04-12 CENTRE DE RECHERCHES METALLURGIQUES - CENTRUM VOOR RESEARCH IN DE METALLURGIE Ass. sans but lucratif Ver. zonder winstoogmerk Procédé de refroidissement en continu d'une tôle en acier et dispositif pour sa mise en oeuvre
BE1012215A3 (fr) * 1998-10-01 2000-07-04 Centre Rech Metallurgique Procede de refroidissement en continu d'une tole en acier et dispositif pour sa mise en oeuvre.
EP1538228A1 (fr) * 2003-12-01 2005-06-08 R & D du groupe Cockerill-Sambre Procédé et Dispositif de refroidissement d'une bande d'acier
WO2005054524A1 (fr) * 2003-12-01 2005-06-16 Usinor S.A. Procede et dispositif de refroidissement d'une bande d'acier
CN100465303C (zh) * 2003-12-01 2009-03-04 阿塞洛法国公司 用于对钢带进行冷却的方法和装置
AU2004294469B2 (en) * 2003-12-01 2009-07-16 Arcelor France Method and device for cooling a steel strip
US7645417B2 (en) 2003-12-01 2010-01-12 Arcelor France Method and device for cooling a steel strip
WO2010049600A1 (fr) * 2008-10-31 2010-05-06 Siemens Vai Metals Technologies Sas Four pour une installation de traitement thermique d'une bande d'acier en défilement continu et procédé associé

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