JPH10245635A - Floating type continuous annealing furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a floating type continuous annealing furnace which can obtain a flat steel plate by accurately straightening the warp developed to the steel plate in the furnace with a simple equipment. SOLUTION: In the floating type continuous annealing furnace providing a preheating zone NOF, heating zone HF and cooling zone CF and passing through a band state steel plate P floated up with a floater F set in the heating zone HF, a straightening roll means A for straightening the warp shape of the plate width developed in the steel plate P is arranged in a position CFb at the downstream side from the heating zone HF.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a floating type continuous annealing furnace. More specifically, the present invention relates to a floating type continuous annealing furnace capable of correcting a warped shape of a steel sheet and improving a yield.

[0002]

2. Description of the Related Art As shown in FIG. 4, a floating type continuous annealing furnace has a pre-tropical NOF, a heating zone HF, and a cooling zone C.
The rolled steel sheet (original sheet) P is supplied to the furnace while being supported by the backup roll BR, and then floated and traveled by a plurality of floaters F installed at predetermined positions in the heating zone HF. Meanwhile, it is configured to be heated by the heating means H arranged above and below the steel sheet P.

[0003] Since the steel sheet supplied into the continuous annealing furnace is cold-rolled, the steel sheet does not have a uniform shape and size, and defective portions such as middle-stretching and ear waves occur. Is corrected by increasing the line tension pulling the steel sheet from the outlet side 1 of the furnace to, for example, 0.7 to 1.0 kg / mm ² or more.

[0004]

However, in the annealing furnace, the steel sheet expands in the sheet width direction, and a tensile stress acts in the running direction due to the line tension to generate a buckling stress in the sheet width direction. Further, the flow velocity of the jet gas blown up from the floater to the lower surface of the steel plate is 20 to 80 m / sec.
c, and the flow velocity of the jet gas flowing in the width direction of the steel sheet is 10 to 50 m / sec, so that the floating pressure distribution immediately below the steel sheet is in a middle-high state. Furthermore, when shifting from the heating step to the cooling step in the annealing furnace, the rate of change in the sheet width changes greatly, so that a component force acts in the sheet width direction. As a result, as shown in FIG. 5, the steel sheet is easily curved so as to exhibit an upwardly convex shape in the sheet width direction, that is, tends to be C-warped.
Since a shape defect of about mm occurs, the line tension must be reduced to 0.4 kg / mm ² or less. In addition, since high-temperature processing materials such as high-grade materials requiring high quality or high-grade materials having a small thickness tend to cause C warpage, the line tension must be extremely low, that is, 0.25 kg / mm ² .

However, when the line tension is 0.7 kg / mm ²
If it is lower, there is a problem that the defective shape portion remains on the product without being corrected and the defective shape portion is not completely annealed.

On the other hand, it is conceivable to improve the shape defect by increasing the precision of the cold rolling, but the adjustment of the bending force, the adjustment of the shift amount of the intermediate roll, and the like are very delicate and must be adjusted accurately. Is difficult. Therefore, in order to prevent a shape defect from occurring in a step before the annealing step, enormous capital investment is required, for example, expansion of a stand of a TCM rolling mill.

The present invention has been made in view of the above circumstances, and has as its object to provide a floating continuous annealing furnace capable of accurately correcting warpage generated in a steel sheet in a furnace with simple equipment and obtaining a flat steel sheet. Aim.

[0008]

The floating continuous annealing furnace according to the present invention includes a pre-tropical zone, a heating zone and a cooling zone,
A floating continuous annealing furnace for passing a strip-shaped steel sheet floated by a floater installed in the heating zone, wherein a straightening roll means for correcting a warped shape of a sheet width generated in the steel sheet is provided from the heating zone. Is also provided at a downstream position.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A floating continuous annealing furnace according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory view showing one embodiment of a floating continuous annealing furnace of the present invention, FIG. 2 is an explanatory view showing one embodiment of a straightening roll means, and FIG. 3 is an explanatory view showing a temperature drop in a cooling zone. is there.

As shown in FIG. 1, the floating type continuous annealing furnace includes a pre-tropical NOF, a heating zone HF, and a cooling zone CF.
The strip-shaped steel sheet P supplied into the continuous annealing furnace is pulled from the outlet side 1 of the furnace, and is supplied by a plurality of floaters F installed at predetermined positions in the heating zone HF.
The steel sheet P is heated by the heating means H while the steel sheet P is floated and passed. The pre-tropical NOF may be a non-oxidizing pre-tropical zone that is rapidly heated to shorten the annealing time. Further, a slow cooling zone BZ may be provided behind the cooling zone CF.

[0011] The floating continuous annealing furnace of the present invention comprises:
The straightening roll means A is provided at a position downstream of the heating zone HF.

As shown in FIG. 2, the straightening roll means A includes a support roll 2 disposed below a pass line L in the traveling direction of the steel sheet, and a first support roll 2 disposed above the pass line L. What consists of leveler roll 3 can be used. In the present invention, the first leveler roll 3 is a so-called C warpage correction roll. Since the C-warped shape of the sheet width of the steel sheet P generated by the floater F is greatly curved when the line tension is large, it is necessary to increase the reduction amount of the leveler roll 3 as the straightening roll means A. For example, the line tension is about 0.7kg
In the case of / mm ^2, the amount of reduction needs to be about 20 mm or more.

The straightening roll means A may be installed at any place where the floater F can correct the C-warped shape of the sheet width generated on the steel sheet P without affecting the properties of the steel sheet P. Although not particularly limited, for example, the durability temperature of the leveler roll 3 is set to 75.
The temperature of the steel sheet is 650 with respect to the elongation percentage of the steel sheet of 0.2% at 0 ° C. or less and the reduction amount of the leveler roll 3 of 20 mm.
If the temperature is not less than ° C., the cooling unit CF is provided between the inlet CFa and the outlet CFb of the cooling unit CF due to a temperature drop (heat cycle) shown in FIG. In the present embodiment,
The straightening roll means A is installed on the outlet side CFb of the cooling zone CF.

The diameter of the support roll 2 is about 100 to 200 mm in order to support the steel sheet P from below. On the other hand, the roll diameter of the first leveler roll 3 is:
Since it is for correcting the C warpage of the steel sheet, the thinner the better, the better it is, but the strength is also required, so it is about 100 to 200 mm, preferably about 150 to 170 mm. The first leveler roll 3 is moved up and down by, for example, a worm jack so that the amount of reduction can be adjusted. In addition, as the support roll 2 and the first leveler roll 3, it is preferable to use a ceramic roll sprayed with ceramic so as not to generate a pick-up flaw, which is a sintering phenomenon due to the contact between the roll and the steel sheet P.

In the present embodiment, the C-warped shape generated by the floater F can be corrected by the straightening roll means A installed downstream from the heating zone HF. Further, in order to correct the rolled shape defective portion of the original sheet, the C-warping generated when the line tension of the steel sheet P is increased can be corrected by the correction roll means A. As a result, a flat steel plate P can be obtained.

In order to correct a large amount of C warpage by the leveling roll 3 as the correcting roll means A, when a large amount of reduction (for example, about 30 to 50 mm) is given, the steel sheet P has a curved shape in the traveling direction. In other words, an L-warped shape may occur. Considering such a case,
In the present embodiment, a second leveler roll 4 disposed below the pass line L is provided downstream of the straightening roll means A as shown in FIG. In the present invention, the second leveler roll 4 is a so-called L warpage correction roll. The roll diameter of the second leveler roll 4 is
200 to 40 to correct the L warpage of the steel sheet.
It is about 0 mm, preferably about 250 to 350 mm. As the second leveler roll 4, it is preferable to use a ceramic roll as in the case of the first leveler roll 3. By setting the amount of reduction of the second leveler roll 4 to about 30 to 80 mm, the L-warped shape of the steel sheet P can be corrected, and the steel sheet P can be made flatter. For example, as the sheet thickness becomes thinner or as the soft material becomes smaller, the amount of reduction of the roll 4 is increased to about 40 to 70 mm.

Next, another embodiment of the present invention will be described. Since the steel sheet has different annealing conditions (temperature × passing speed) depending on the steel type as shown in FIG. 3, only one straightening roll means cannot cope with each steel type. The straightening of the C-warped shape tends to vary. Therefore, at least the straightening roll means for the low-temperature treatment material with a low sheet temperature is installed immediately after the heating zone, and the straightening roll means for the high-temperature treatment material with a high sheet temperature is installed at a position away from the heating zone. Is desirable.

In the present embodiment, the straightening roll means A of the above-described embodiment is provided on the atmosphere gas seal portion 5 on the inlet CFa of the cooling zone CF and on the outlet CFb, respectively.
This is because, depending on the type of steel, the annealing temperature in the HF zone varies, and some of them reach 650 to 750 ° C at the position of CFa.
This is because some of them have the following position.

Then, the sheet passing speed or the set furnace temperature of the heating zone HF is controlled so that the optimum sheet temperature region T for correcting the C-warped shape of the steel sheet P is 650 to 750 ° C.
The two correction roll means A are used properly. For this reason, the steel plate of each steel type can be straightened.

By providing the second leveler roll 4 in the straightening roll means A, it is possible to straighten the C-warp shape and the L-warp shape in the same manner as in the above embodiment and obtain a flat steel plate.

[0021]

As described above, according to the present invention,
By increasing the line tension, it is possible to correct the rolled shape defective portion of the original sheet, and to correct the generated C-warped shape by the correction roll means due to the increased line tension. For this reason, a flat steel plate can be obtained.

Further, by providing the leveling roll means with a second leveler roll, it is possible to correct the L-warped shape generated when a large amount of C warpage is corrected.

Further, since at least two straightening roll means are provided and selectively used according to the low-temperature treatment material and the high-temperature treatment material of the steel sheet, a flat steel sheet of each steel type can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an embodiment of a floating type continuous annealing furnace according to the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of a correcting means.

FIG. 3 is an explanatory diagram showing a temperature drop in a cooling zone.

FIG. 4 is an explanatory view showing a conventional floating type continuous annealing furnace.

FIG. 5 is an explanatory diagram showing C warpage of a steel sheet.

[Explanation of symbols]

 1 Furnace Outlet 2 Support Roll 3 First Leveler Roll 4 Second Leveler Roll 5 Atmospheric Gas Seal A Straightening Roll Means NOF Pretropical HF Heating Zone CF Cooling Zone CFa Cooling Zone Inlet CFb Cooling Zone Outlet

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazumi Okamoto 1 Fujimachi, Hirohata-ku, Himeji-shi, Hyogo Nippon Steel Corporation Hirohata Works

Claims (5)

[Claims] 1. A floating continuous annealing furnace having a pre-tropical zone, a heating zone and a cooling zone, wherein a strip-shaped steel sheet floated by a floater installed in the heating zone is passed through, and a width of the steel sheet generated on the steel sheet. And a straightening roll means for correcting the warped shape of the heating zone is provided at a position downstream of the heating zone. 2. The method according to claim 1, wherein the straightening roll means has a steel plate temperature of 6 ° C.
The floating type continuous annealing furnace according to claim 1, which is installed at a position within a range of 50 to 750 ° C. 3. The straightening roll means comprises a support roll installed below a pass line in the traveling direction of the steel sheet, and a first leveler roll arranged above the pass line. Floating type continuous annealing furnace. 4. The floating continuous annealing furnace according to claim 3, wherein said straightening roll means comprises a second leveler roll disposed below said pass line. 5. The floating continuous annealing furnace according to claim 1, wherein said straightening roll means is provided at an upstream position and a downstream position of a cooling zone.