JP4662828B2 - Cooling zone of horizontal continuous processing furnace and steel strip threading method in the cooling zone - Google Patents

Description

  The present invention relates to a steel strip threading technique in a cooling zone of a horizontal continuous processing furnace equipped with a gas jet cooler that cools by blowing high-speed gas on both sides of the steel strip.

  In horizontal continuous processing furnaces such as continuous annealing furnaces for steel strips and continuous hot dipping plating equipment, when the furnace is started up or when the steel strip breaks, new threading is required to pass the steel strip through the furnace. Become. The threading of the steel strip into the furnace is performed by transporting the threading bar by a hearth roll as a steel strip transport means and connecting the steel strip to the rear end of the threading bar.

  When the hearth rolls are provided at a pitch of about 3 m, the length of the threading bar is about 10 m when straddling the three hearth rolls so as not to fall between the hearth rolls. Further, the threading bar is chamfered at the lower end of the tip so that it does not hit the hearth roll during threading, but the cross-sectional height may exceed 100 mm.

  The steel strip horizontal continuous processing furnace includes a step of continuously heating, soaking and cooling the steel strip, and over-aging as necessary. And in order to make the properties of the steel strip desired, it is important to uniformly and rapidly cool the steel strip in addition to the heating temperature and the soaking time. The cooling method using a gas as a cooling medium for the steel strip is capable of uniform cooling in the width direction of the steel strip as compared with other cooling methods such as water cooling and roll cooling, but the cooling rate is inferior. There is. Therefore, as measures for improving the cooling rate, measures are taken such as bringing the tip of the nozzle for injecting gas closer to the steel strip or increasing the heat transfer coefficient of the cooling medium. However, when measures are taken to bring the tip of the nozzle for injecting gas closer to the steel strip, the threading bar cannot pass through the gas jet cooler during threading.

  On the other hand, in Patent Document 1, a wind box (plenum chamber) integrated with a nozzle for injecting a gas is disposed opposite to a steel strip conveyance path, and the wind box is arranged in a direction to be in contact with or separated from the steel sheet conveyance path. A device that can be moved is disclosed. By making the windbox movable in this way, the cooling rate applied to the steel strip can be increased by reducing the distance between the nozzle and the steel strip surface, and the thread can be threaded by increasing the spacing. It can also be facilitated quickly.

Patent Document 2 discloses an invention in which a hearth roll that can be raised and lowered for threading is newly provided in a horizontal continuous heat treatment furnace such as a floating furnace or a catenary furnace that does not have a hearth roll in the furnace. According to this, the contact between the steel strip and the floater can be avoided by raising the hearth roll during threading. Moreover, at the time of normal operation, the contact between the steel strip and the hearth roll can be avoided by lowering the hearth roll.
Japanese Utility Model Publication No.59-40436 JP-A-8-13044

  Even in the horizontal continuous processing furnace, it is conceivable to apply the method of widening the upper and lower windbox gaps as disclosed in Patent Document 1 so that the threading bar can pass through the gas jet cooler during threading. In this case, since the plate passing level (pass line) of the steel strip is fixed to the hearth roll upper surface level, in order to pass the threading bar, as shown in FIG. Box 15 is raised. The elevating mechanism 17 of the upper window box is configured so that, for example, four jacks are connected with a mechanical tie and are moved up and down in synchronization.

  However, according to this method, the upper space of the gas jet cooler is occupied by the lifting mechanism 17 of the upper window box. And, it is necessary to separately attach an accessory device (not shown) such as a heat exchanger / blower of the gas jet cooler near the wind box. The upper window box elevating mechanism 17 has a large upper window box 15 itself, and in order to make the upper window box 15 movable, a gas supply duct 24 for supplying gas to the upper window box 15 and a furnace body 25. In addition, since the bellows 23 for displacing the upper window box 15 is required, the equipment cost is high.

  On the other hand, in the method of Patent Document 2, it is necessary to newly provide a hearth roll that is used only during threading. Furthermore, in the method of Patent Document 2, a hearth roll for threading is provided throughout the continuous heat treatment furnace, and the hearth roll is simply raised to a certain level or more, and a threading bar is installed like a gas jet cooler installation part. It is not possible to deal with the case where there is a limit to the gap to be passed.

  Therefore, the problem to be solved by the present invention is to provide a new conveying roll exclusively for threading in the cooling zone of a horizontal continuous processing furnace equipped with a gas jet cooler that cools both surfaces of a steel strip by spraying high-speed gas. It is possible to easily and inexpensively secure a gap through which the threading bar passes.

  In order to solve the above-described problems, a method for threading a steel strip in a cooling zone of a horizontal continuous processing furnace according to the present invention includes a horizontal continuous processing furnace equipped with a gas jet cooler that cools by blowing high-speed gas on both sides of the steel strip. A steel strip threading method in a cooling zone, in which a steel strip is connected to a threading bar and passed through the cooling zone of a horizontal continuous processing furnace, and at the time of threading, the hearth rolls inside and outside the gas jet cooler Is lowered to secure a threading gap through which the threading bar can pass.

  In the present invention, it is preferable that the descending amount of the hearth roll on the inlet side and the outlet side of the gas jet cooler during threading is smaller than the descending amount of the hearth roll in the gas jet cooler. This is to prevent the threading bar from colliding with the hearth roll in the gas jet cooler.

  The cooling zone of the horizontal continuous processing furnace according to the present invention is a cooling zone of a horizontal continuous processing furnace provided with a gas jet cooler that cools by blowing high-speed gas on both sides of the steel strip. When threading to connect and pass through the cooling zone of the horizontal continuous processing furnace, a hearth roll lifting mechanism is installed to lower the gas jet cooler and the inlet and outlet hearth rolls of the gas jet cooler, and the threading bar passes when threading. It is characterized in that a threading gap that can be formed is secured.

  The hearth roll lifting mechanism is preferably provided on the side wall of the horizontal continuous processing furnace.

  Further, the blower for supplying gas to the gas jet cooler, the gas supply duct, and the heat exchanger for exchanging heat of the gas can be installed as a unit on the upper and side portions of the gas jet cooler.

  According to the present invention, by raising and lowering the hearth roll, there is no need to newly install a threading-dedicated transport roll, and without raising the upper wind box, the upper wind box and the hearth roll The threading bar will be able to pass through.

  Therefore, it is not necessary to provide a lifting mechanism for the upper wind box above the gas jet cooler, and a gap for passing the threading bar can be secured simply and inexpensively. In addition, the hearth roll that is raised and lowered during threading is smaller than a wind box and does not require a bellows, so the manufacturing cost of the hearth roll raising and lowering mechanism can be reduced.

  Furthermore, since the hearth roll lifting mechanism can be provided on the side wall of the horizontal continuous processing furnace, the upper space of the gas jet cooler can be effectively utilized. That is, accessory devices such as a heat exchanger and a blower of the gas jet cooler can be concentrated in the upper space of the gas jet cooler, and a space-saving unit of the gas jet cooler can be realized.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows an example of a continuous hot dip plating apparatus including a horizontal continuous processing furnace 12 to which the present invention is applied. The horizontal continuous processing furnace 12 includes a pre-tropical zone 1, a non-oxidation heating zone 2, a reduction zone 3 and a cooling zone 4 for continuously heating, soaking and cooling the steel strip 7, and overaging as necessary. A treatment zone is further provided, and the plating treatment facility 5 is continued. In the furnace, hearth rolls 6 are arranged with an appropriate interval. The steel strip 7 is paid out from the payoff reel 8 and is guided into the furnace through an intermediate facility such as a looper.

  In the case of starting up the furnace, breaking the steel strip 7, etc., threading for newly passing the steel strip 7 through the furnace is required. In the threading operation of the steel strip 7 into the furnace, a threading bar is put into the furnace from the furnace bottom 10 and is transported to the furnace front 9 by the hearth roll 6 as a transport means of the steel strip 7. Then, the steel strip 7 supplied by the furnace entry side equipment such as the payoff reel 8 and the looper is connected to the rear end of the threading bar at the furnace front 9 and is again conveyed to the furnace bottom 10 by the hearth roll 6.

  When the hearth rolls 6 are provided at a pitch of about 3 m, the length of the threading bar may be about 10 m when straddling the three hearth rolls 6 so as not to fall between the hearth rolls. Further, the threading bar is chamfered at the lower end of the tip so that it does not hit the hearth roll 6 during threading, but the cross-sectional height may exceed 100 mm.

  FIG. 2 shows details of the cooling zone 4 of the horizontal continuous processing furnace 12 shown in FIG. The cooling zone 4 includes a gas jet cooler A that cools the steel strip 7 by spraying high-speed gas on both sides. The gas jet cooler A has an upper nozzle 13 provided in the upper window box 15 and a lower nozzle 14 provided in the lower window box 16, and gas supplied to the upper window box 15 and the lower window box 16 is supplied to the upper nozzle 13. 13 and the lower nozzle 14 are sprayed at high speed on both surfaces of the steel strip 7 to cool the steel strip 7. In addition, a hearth roll 6 as a conveying means for the steel strip 7 is arranged in the gas jet cooler A and on the inlet side and the outlet side of the gas jet cooler A. During normal operation, the steel strip 7 is gasified by the hearth roll 6. The inside of the jet cooler A is conveyed, and at the time of threading, the threading bar 11 and the steel strip 7 connected to the rear end thereof are conveyed through the gas jet cooler A by the hearth roll 6.

  In FIG. 2, the gap between the upper nozzle 13 and the lower nozzle 14 is 140 mm (that is, the distance between the steel strip 7 and the nozzle tip is 70 mm), the height of the threading bar 11 is 100 mm, and the required height of the threading has a margin. An example in the case of 120 mm is shown. In such a dimensional relationship, the plate level (pass line) of the steel strip 7 during normal operation is such that the distance between the steel strip 7 and the nozzle tip is 70 mm as an intermediate level between the upper nozzle 13 and the lower nozzle 14. The upper surface of the hearth roll 6 is also set at this height level. However, the threading bar 11 having a height of 100 mm cannot be passed with the steel plate 7 passing through the level (pass line) during normal operation. Therefore, at the time of threading, the hearth rolls 6 in the gas jet cooler A and on the inlet side and the outlet side of the gas jet cooler are lowered to ensure the necessary threading height at which the threading bar 11 can pass through the gas jet cooler A.

  In the example of FIG. 2, the descending amount of the hearth roll 6 is set to 50 mm, and the required threading height of 120 mm is secured. Here, the lowering amount of the hearth roll 6 on the inlet side and the outlet side of the gas jet cooler A is within a range in which the required threading height through which the threading bar 11 can pass can be secured, and the lowering amount of the hearth roll 6 in the gas jet cooler A. It is preferable to make it smaller. This is to prevent the hearth roll 6 and the threading bar 11 from colliding due to a sudden change in the level of the hearth roll 6 in the gas jet cooler A although the lower end of the tip of the threading bar 11 is chamfered. . The descending amount of the hearth roll 6 in the gas jet cooler A is not limited to 50 mm according to the example of FIG. 2, but can be determined according to the threading required height determined by the height of the threading bar 11 and the like. Good.

  3A and 3B show a lifting mechanism of the hearth roll, wherein FIG. 3A is a sectional view thereof and FIG. 3B is a side view thereof. The hearth roll raising / lowering mechanism 20 has the same configuration as the steering apparatus for the in-furnace transport roll disclosed by the applicant of the present invention in Japanese Patent Laid-Open No. 8-283871. That is, the hearth roll 6 can be moved up and down by an operation on the furnace side wall side by attaching the bearing of the hearth roll 6 eccentrically to the bearing support metal 21 on the furnace side wall and rotating the bearing support metal 21. The hearth roll elevating mechanism 20 is sealed using a gland packing 22, and thus has a simple structure, easy repair, and low cost.

  FIG. 4 shows an example of unitization of the gas jet cooler according to the present invention. In the present invention, the upper wind box 15 is not raised, and the upper space of the gas jet cooler A is not occupied by the lifting device 17 of the upper wind box unlike the conventional example of FIG. Attached to the upper space of the gas jet cooler A, such as the blower 19 for supplying gas to the gas and the heat exchanger 18 for exchanging heat of the gas, can be gathered in the upper space of the gas jet cooler A, including the gas supply duct 24. Can be installed as a unit in the department.

  Thus, according to the present invention, it is possible to realize a unitization of a space-saving gas jet cooler. Normally, an overhead crane runs above the gas jet cooler, and a looper is installed below the gas jet cooler base, so there is little effective space around the gas jet cooler. When the gas jet cooler is united according to the present invention, the effective space is expanded.

  In addition, the development of improving the cooling speed of the gas jet cooler is still actively carried out, but the unitized gas jet cooler according to the present invention can be used for the replacement of the development result with high efficiency. It is not necessary to consider the installation space of auxiliary equipment such as the heat exchanger 18 and the blower 19 and can be replaced in a short construction period.

An example of the continuous hot dipping equipment provided with the horizontal type | mold continuous processing furnace to which this invention is applied is shown. The detail of the cooling zone of the horizontal type continuous processing furnace shown in FIG. 1 is shown. The raising / lowering mechanism of a hearth roll is shown, (a) is the sectional drawing, (b) is the side view. An example of unitization of the gas jet cooler concerning the present invention is shown. A conventional example of raising the upper windbox is shown.

Explanation of symbols

1 Pre-tropical zone 2 Non-oxidation heating zone 3 Reduction zone 4 Cooling zone 5 Plating treatment equipment 6 Hearth roll (in-furnace transport roll)
7 Steel strip 8 Payoff reel 9 In front of furnace 10 Furnace bottom 11 Threading bar 12 Horizontal continuous processing furnace 13 Upper nozzle 14 Lower nozzle 15 Upper window box 16 Lower window box 17 Lifting device for upper window box 18 Heat exchanger 19 Blower 20 Hearth roll Lifting device 21 Bearing support hardware 22 Gland packing 23 Bellows 24 Supply duct 25 Furnace body A Gas jet cooler

Claims (5)

A steel strip threading method in the cooling zone of a horizontal continuous processing furnace equipped with a gas jet cooler that cools by blowing high-speed gas on both sides of the steel strip,
When threading the steel strip connected to the threading bar and passing through the cooling zone of the horizontal continuous processing furnace, the threading gap through which the threading bar can pass by lowering the hearth rolls inside and outside the gas jet cooler and the gas jet cooler A method for threading a steel strip in a cooling zone of a horizontal continuous processing furnace.   The steel in the cooling zone of the horizontal continuous processing furnace according to claim 1, wherein a descending amount of the hearth roll on the inlet side and the outlet side of the gas jet cooler at the time of threading is smaller than a descending amount of the hearth roll in the gas jet cooler. Band threading method. In the cooling zone of a horizontal continuous processing furnace equipped with a gas jet cooler that cools by blowing high-speed gas on both sides of the steel strip,
At the time of threading where the steel strip is connected to the threading bar and passes through the cooling zone of the horizontal continuous processing furnace, there is provided a hearth roll lifting mechanism that lowers the hearth rolls on the gas jet cooler and on the inlet and outlet sides of the gas jet cooler, A cooling zone for a horizontal continuous processing furnace characterized in that a threading gap through which a threading bar can pass during threading is secured.   The cooling zone for a horizontal continuous processing furnace according to claim 3, wherein the raising / lowering mechanism of the hearth roll is provided on the side wall of the horizontal continuous processing furnace.   The blower that supplies gas to the gas jet cooler, the gas supply duct, and the heat exchanger that performs heat exchange of the gas are installed as a unit at the upper part and the side part of the gas jet cooler according to claim 3 or 4. Horizontal continuous processing furnace cooling zone.

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