JP2001172721A - Method for compensating slab temperature and equipment for compensating slab temperature - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a unit requirement of energy and a manufacturing cost in the slab temperature compensating equipment which is inserted between a casting apparatus and a hot-rolling apparatus and saves a reheating process of the slab in the hot-rolling apparatus. SOLUTION: The slab temperature compensating equipment 12 is arranged between the continuous casting apparatus 11 and the hot-rolling apparatus 15. The slab temperature compensating equipment 12 is constituted with an induction-heater 13 for heating the edge parts of the slab and a heat-holding furnace (heat-holder) 14 for heating the surfaces containing the side surfaces of the slab and composed of a gas-burning heating furnace for executing the heat-holding of the whole slab.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slab temperature compensating method and a slab temperature compensating device which is inserted between a casting facility and a hot rolling facility to omit a slab reheating process in the hot rolling facility.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable progress in a continuous casting-hot rolling direct joining technique in which a slab manufactured by a continuous casting facility is directly sent to a hot rolling facility and rolled to a product.

In this continuous casting-hot rolling direct connection process, in order to secure a temperature at which a slab manufactured by the continuous casting facility can be rolled before the hot rolling mill, the continuous casting facility and the hot rolling facility are combined. It is an indispensable condition to provide a slab temperature compensating facility between them.

[0004] The central portion of the slab in the width direction has a sufficient amount of heat, but the end of the slab is infinitely short of heat. It is.

[0005] As a conventional slab temperature compensating equipment, there has been a gas-fired heating equipment. This is to burn a high calorie gas to burn the slab edge and the corner, and at the same time, to increase the ambient temperature with the combustion gas to secure the heat retaining effect of the entire slab.

Further, there has been an example in which a transverse E-type induction heater for heating up to 200 mm or more inside in a slab side surface and a slab width direction is used as a slab temperature compensating equipment.

[0007]

In a slab temperature compensating equipment using a gas-fired heating equipment, a high burner flame temperature of 1200 ° C. or more is required for edge heating by a direct burner. There is a problem in that the fuel is burned at a low efficiency (heating efficiency of about 10%) so that the unit energy consumption is remarkably deteriorated.

The transverse E-type induction heater is a large-capacity and large-scale facility for induction-heating a wide range. This is because, in order to perform induction heating not only at the corners but also over a certain range of surfaces, it is necessary to apply both local and surface heating energy as in the case of gas-fired heating equipment. Incidentally, the heating power supply capacity is equivalent to 10,000 kW, and there is a problem that the power consumption unit is remarkably deteriorated.

Therefore, the conventional slab temperature compensating equipment has a problem that the unit energy consumption is low and the cost for compensating the slab temperature is high.

An object of the present invention is to provide a slab temperature compensating method and a slab temperature compensating equipment capable of improving the energy consumption for compensating the slab temperature and reducing the production cost.

[0011]

Means for Solving the Problems [Configuration] The present invention is configured as follows to achieve the above object.

(1) The slab temperature compensation method according to the present invention (claim 1) is performed between a slab casting step and a hot rolling step, and omits a slab reheating process in the hot rolling step. The edge of the slab is locally heated by an induction heater, and the surface temperature of the slab is maintained and heat is maintained by a heat insulator connected in series to the induction heater.

(2) The present invention (Claim 2) is a slab temperature compensating equipment which is inserted between a casting facility and a hot rolling facility to omit a slab reheating process in the hot rolling facility. An induction heater that heats the edge of the slab and a heat insulator that secures the surface temperature of the slab and keeps heat are connected in series.

Preferred embodiments of the present invention are described below.
The induction heater shall be a transverse type C-type inductor. The heat retainer is a gas-fired heating furnace that retains heat by heating the atmosphere. Or that the heat insulator is a heat insulator.

[Operation] The present invention has the following operation and effects by the above configuration.

The end of the slab having an insufficient amount of heat is provided by an induction heater having an excellent local heating property, and the entire slab is kept in a gas-fired heating furnace or a heating furnace having a high heat retention effect. Depending on the characteristics of the heater, heating and heat retention can be performed, and the energy intensity can be improved.
Manufacturing costs can be reduced.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a temperature compensation facility according to an embodiment of the present invention. As shown in FIG. 1, between the continuous casting facility 11 and the hot rolling facility 15,
A slab temperature compensation facility 12 is provided. The slab temperature compensating equipment 12 includes an induction heater 13 that heats the edge of the slab, and a heat insulation furnace (heat insulator) that includes a gas-fired heating furnace that heats a surface including a side surface of the slab and heats the entire slab. 14.

The hot rolling equipment 14 is preferably arranged at a position where the slab moves in synchronization with the drawing speed (less than 5 mpm) of the continuous casting equipment. If heating is performed simultaneously during drawing by the continuous casting machine in such an arrangement, the drawing speed becomes very low. Since the power supply capacity is proportional to the drawing speed, the power supply capacity can be reduced by disposing the hot rolling equipment 14 at a position where the slab moves in synchronization with the drawing speed of the continuous casting equipment.

As the induction heater 13, for example, a transverse type C-type inductor is used. As shown in FIG. 2, the transverse type C-type inductor has a cross-sectional shape of C
The end of the slab 21 is arranged between the gaps of the C-shaped inductor 22. The C-type inductor 22 can heat the edge of the slab 21 with high efficiency while securing a safe distance from the slab 21. As the induction heater 13, besides the C-type inductor shown in FIG.
The modified C-type inductors 22 'and 22 "shown in FIG. 3B can be used.

If the C-type inductor 22 can generate a magnetic flux penetrating the end of the slab 21, by setting the frequency within a certain range, the end of the slab can be heated more locally.

The induction heater 13 is preferably a transverse type C-type inductor, but any type of inductor can be used as long as the end of the slab can be sufficiently heated, regardless of the shape of the inductor. . However, the E-type inductor is not practical because it has a lower heating efficiency than the C-type inductor.

Further, a heat retaining furnace 14 comprising a gas-fired heating furnace.
Is based on atmospheric heating, and does not matter the type or method as long as the slab has a sufficient heat retaining effect. As the heat retention furnace 14, it is preferable to use a tunnel furnace or the like having a high efficiency of raising the atmosphere of a tunnel furnace or the like to high heat. Since the heat retaining furnace 14 seeks only the heat retaining effect by increasing the ambient temperature, low-cost gas such as M gas, blast furnace, and mixture gas can be used.

If the transfer time from the continuous casting facility 11 to the hot rolling facility 15 is short and the surface temperature drop of the slab is small, a heat retaining cover can be employed instead of the gas-fired heating furnace.

In the slab temperature compensating equipment 12 described above, a small-capacity induction heater can be used by locally heating a required slab corner by an induction heater, and a heat storage furnace having a high heat retention effect can be used. By maintaining the heat of the entire slab, the unit energy consumption is improved, so that the manufacturing cost can be reduced.

The heating power supply capacity can be further reduced by limiting the heating range of the induction heater to a range of 30 to 50 mm square in the plate thickness direction and the plate width direction. In addition, the power supply capacity can be reduced by installing the position at a position that can be synchronized with the drawing speed of the continuous casting machine. By reducing the power supply capacity, the dimensions of the entire induction heater can be reduced, and the installation work cost can be reduced.

In a slab temperature compensation system using only a gas-fired heater, when directly rolling a long slab of 10 m or more, the furnace length had to be longer than the slab length. Since the entire slab is kept heat after the end is heated, a furnace longer than the slab length is not required.

Next, design requirements for the slab temperature compensating equipment will be described. The design requirement of this facility is how to limit the local heating range by the induction heating device to reduce the facility capacity and power consumption.

Even in a VSB (hard rolling mill) that can be strongly reduced (100 mm reduction) in the width reduction rolling in the next step, the position of occurrence of edge flaws is at most about 1/2 of the reduction amount. Accordingly, the heating range of the slab end by induction heating is 30 m in the thickness direction and the width direction in the slab edge direction shown in FIG.
An area S of a square of m to 50 mm may be considered.

When only cooling from the surface and induction heating are considered, ignoring heat transfer in the slab, in the induction heater, the amount of heat generated by induction heating and the time of radiant cooling pass through the induction heating area. It may be considered that Δt is continued.

The amount of heat generated by induction heating per unit volume in the heating section L is P = P / (S × L), where P is the power supplied to the area of the local heating range S in the heating section L. 1)

Assuming that the temperature change of the volume considering the width H, the height W, and the length ΔL is ΔT, the energy conservation equation is as follows. Becomes

Then, equation (2) is expressed as follows: ρ × C _p × (H × W × △ L) × △ T = -q × (H + W) × △ L × △ t +
p × S × △ L × △ t. Here, C _p is a constant pressure specific heat of the slab, and q is a radiant cooling amount per unit volume in the heating section L.

The drawing speed of the slab in the continuous casting equipment is V
Then, since Δt = L / V, equation (2) is given by: ρ × C _p × (H × W × △ L) × △ T = {− q × (H + W) × ΔL + p ×
ΔL / L} × L / V.

As a result, the temperature change ΔT of the slab is given by ΔT = Ｔ−q × (H + W) × L + P｝ / (ρ × C _p × H
× W × V).

Next, a specific temperature change of the slab is calculated. Assuming that the surface temperature is 1200 ° C., the cooling heat flow rate q has the following value.

[0037] q = ε × σ × (T surf 4 -T 0 4) = 0.8 × 4.88 × 10 -8 × (1473.15 4 -300 4) = 183548kcal / m 2 h = 213262W / m ² Other physical property values and arrangement were as follows: ρ = 7800 kg / m ³ , C _p = 0.16 kcal / kg = 670 J / kg, L = 1 m, V = ² mpm = 3.33 × 10 ⁻² m / s .

Next, the area to be considered for the edge is set to H from the end.
= 50 mm, the amount by which the slab edge averagely rises in temperature as a square area up to W = 50 mm is determined. Heating frequency of 300Hz or more and 1000H for local heating
Assuming that a heating efficiency of 50% is possible by setting a value less than z to a numerical limitation range, the relationship between the power supply and the amount of temperature rise is as shown in FIG.

As shown in FIG. 5, if an induction heating device is arranged on the continuous casting output side, even if the temperature is raised by 300 ° C., the power supply capacity on one side of the slab is at most 600 KW / one side, so that a compact induction heating device can be obtained. 5 per side in the prior art
Considering that it was 000 KW, economical design becomes possible.

The required temperature rise in the corner can be evaluated as follows.

For example, after the casting of a slab having a length of l is completed at the drawing speed V, the transport time τ _h , τ _t required to transport the slab to the hot rolling equipment in the next step is τ _h = (casting time) + ( Table transfer time) τ _t = (table transfer time) + (width rolling time). Here, τ _h is the time required for the slab tip to be conveyed, and τ _t is the time required for the slab tail to be conveyed.

For example, the transfer times τ _h and τ _t required to complete the casting of a 10-m slab at a drawing speed of 2 m / min and to transfer the slab to the hot rolling equipment in the next step are as follows. Assuming that the minute speed in the hot rolling equipment is 50 m, τ _h = 10 [m] / 2 [mpm] × 60 [s] +300 [s] = 600
[s] τ _t = 300 [s] +10 [m] / 50 [mpm] × 60 [s] = 31
2 [s]. Therefore, the temperature drop is more severe at the tip, and the equipment design may be performed at the tip.

Assuming that the cooling speed of the slab is about 0.16 ° C./s, the temperature that decreases during the transfer from the completion of casting to the hot rolling facility is 0.16 [° C./s]×600 [s]. $ 100
[° C.], which indicates that the temperature should be raised by about 100 ° C.

The transfer times τ _h and τ _t from the completion of casting of the 30-m slab to the next step of hot rolling equipment are as follows, assuming that the table transfer time is 300 seconds and the speed per minute in the hot rolling equipment is 50 m. _{τ h = 30 [m] /} 2 [mpm] × 60 [s] +300 [s] = 120
0 [s] τ _t = 300 [s] +30 [m] / 50 [mpm] × 60 [s] = 33
6 [s]. However, the temperature drop is more severe at the tip, and the equipment design should be done at the tip.

Assuming that the cooling speed of the slab is about 0.16 ° C./s, the temperature that decreases during the transfer from the completion of casting to the hot rolling equipment is 0.16 [° C./s]×1200 [s]. $ 2
00 [° C.], indicating that the temperature should be raised by about 200 ° C.

In addition, even if the equipment allowance is taken into consideration, when directly feeding a 30 m slab, 200 [° C.] × 1.25 times = 250 [° C.]
From FIG. 5, the power source is 550 kw / one side induction heating device.

Next, the conditions that the gas-fired heating furnace should have are evaluated.

The transfer time τ _h , τ _t from the completion of casting of the 10 m slab to the hot rolling equipment in the next step is τ _h = (table transfer time) τ _t = (table transfer time) + (width rolling time) Becomes

For example, after the casting of a 10 m slab is completed,
Transfer time τ to hot rolling equipment _h, Τ_tOf the slab
Under the same conditions as the consideration for the required temperature rise in the corner, τ_h= 300 [s] τ_s= 300 [s] + 10 [m] / 50 [mpm] x 60 [s] = 31
2 [s].

Therefore, the temperature drop is more severe at the tail end, and the equipment design may be performed at the tail end. If the cooling speed is about 0.12 [° C./s], it becomes 0.12 [° C./s]×312 [s] ≒ 37 [° C.].
A temperature drop of about 7 ° C. is estimated.

The transfer time τ _h , τ _t from the completion of casting of the 30-m slab to the hot rolling equipment in the next step is the same as that in consideration of the required temperature rise in the corner of the slab, and the tip τ _h = 300 [s] tail end τ _s = 300 [s] +10 [m] / 50 [mpm] × 60 [s] =
336 [s] Therefore, the temperature drop is more severe at the tail end, and the equipment design may be performed at the tail end. When the cooling speed is about 0.12 [° C / s],
0.12 [° C./s]×336 [s] ≒ 40 [° C.], and a temperature drop of about 40 ° C. is estimated during the transfer to the hot rolling equipment after the completion of casting.

From the above considerations, if the temperature in the furnace is kept at 1150 ° C., 1100
Since a temperature of not less than ° C. can be secured, it is possible to surely achieve a temperature of not less than the ferrite-forming temperature (below the Ar ₃ transformation point).

By installing an induction heating device on the continuous casting output side with the above design and keeping the temperature in a gas-fired heating furnace, sufficient surface humidity can be ensured in the hot rolling equipment in the next step. If the transfer time is short, the gas-fired heating furnace is omitted, and there is no problem with the heat retaining cover.

The present invention is not limited to the above embodiment, but can be implemented with various modifications without departing from the spirit of the invention.

[0055]

As described above, according to the present invention, the end of a slab having a shortage of heat is performed by an induction heater having an excellent local heating property, and a gas-fired heating furnace or a heat holding furnace having a high heat retention effect is provided. By keeping the heat of the entire slab, heating and heat can be carried out according to the characteristics of the respective heaters, and the energy consumption can be improved, so that the production cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a temperature compensation facility according to an embodiment of the present invention.

FIG. 2 is a diagram showing a schematic configuration of a C-type inductor which is an example of an induction heater.

FIG. 3 is a diagram showing a modification of the C-type inductor.

FIG. 4 is a diagram showing a range considered by a slab.

FIG. 5 is a characteristic diagram showing a relationship between a temperature rise of a slab and heating power by an induction heater.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Continuous casting equipment 12 ... Slab temperature compensation equipment 13 ... Induction heater 14 ... Heat keeping furnace 15 ... Hot rolling equipment 21 ... Slab 22 ... C type inductor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C21D 1/42 B21B 37/00 132B (72) Inventor Hiroshi Sekine 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (72) Inventor Masanori Yamagishi 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Japan Inside Nippon Kokan Co., Ltd. (72) Yoichi Honashiki 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun (72) Inventor Yoshimichi Hino Inventor, 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Co., Ltd. (72) Inventor Tetsuji Doizaki 1-1-1, Shibaura, Minato-ku, Tokyo Inside Toshiba Corporation Head Office (72) Inventor Norio Kudo Fukushima Fukushima 9 Tennohara, Matsukawa-cho, Shima-shi F-term in Kitashiba Electric Co., Ltd. (reference) 4E024 BB07 BB09

Claims (2)

[Claims] 1. A slab temperature compensating method which is performed between a slab casting step and a hot rolling step and omits a slab reheating process in the hot rolling step, wherein an edge of the slab is cut by an induction heater. A slab temperature compensation method, wherein the slab is locally heated, and the surface temperature of the slab is maintained and heat is maintained by a heat retainer connected in series to the induction heater. 2. A slab temperature compensating unit inserted between a casting unit and a hot rolling unit and omitting a slab reheating process in the hot rolling unit, comprising: an induction heater for heating an edge of the slab. A slab temperature compensating facility, wherein a slab for keeping the surface temperature of the slab and keeping the heat is connected in series.