JP2007224373A - Method for charging slab into heating furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a filling factor of a slab in a walking-beam type furnace. <P>SOLUTION: When continuously charging a plurality of slabs into the walking-beam type furnace and heating them in the furnace, this charging method includes determining a space (L) between a leading slab and a following slab by the expression: L=(ΔW1+ΔW2)/2+α, wherein ΔW<SB>1</SB>represents a thermally expanded amount in a width direction of the leading slab, which is calculated from a temperature when the leading slab has been charged and a set temperature when the slab is extracted; ΔW<SB>2</SB>represents a thermally expanded amount in a width direction of the following slab which is calculated from a temperature when the following slab has been charged and a set temperature when the slab is extracted; and (α) represents the minimum space between the slabs in the walking-beam type furnace. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for operating a walking beam heating furnace, and more particularly to a method for charging a slab.

  In order to hot-roll a slab from a thick steel plate or a hot-rolled steel plate, it is necessary to heat the slab to a predetermined temperature prior to that. In recent years, this heating is performed using a so-called walking beam heating furnace. At that time, the slab is charged into the heating furnace by arranging a plurality of slabs so that the longitudinal direction thereof is perpendicular to the hearth conveying direction of the heating furnace, and a necessary interval between the slabs is maintained. To be done.

  Conventionally, the furnace operating conditions of this heating furnace are determined from the slab heating conditions such as the steel type and the heating temperature, as disclosed in Patent Document 1 and Patent Document 2, and the in-furnace time for heating at the required temperature In addition to ensuring fuel efficiency, it is possible to reduce fuel consumption, improve productivity, and ensure the safety of charging, extraction, and tracking. In addition, although not disclosed in the above patent document, when heating slabs having substantially the same heating conditions, in consideration of productivity, the interval between the slabs can be safely inserted and extracted. It is also operated as a constant value that can be secured.

JP-A-8-291334 Japanese Patent Laid-Open No. 3-200619

  It is easy to operate with such a constant interval between slabs, and there is an advantage that the load required for tracking control is small, but since the interval between slabs is fixed to a predetermined value, The slab filling rate may not be increased sufficiently. In particular, when the predetermined value is excessively set, for example, placing importance on safety in the operation of the furnace, it becomes an obstacle to improving the slab filling rate in the heating furnace. An object of the present invention is to solve such operational obstacles and improve the slab filling rate of a walking beam type heating furnace.

  The present invention has been completed by paying attention to the fact that the interval between the slabs can be reduced to the minimum amount by considering the thermal expansion amount of the slabs in the in-furnace in setting the predetermined value.

That is, according to the present invention, when a plurality of slabs are continuously charged and heated in the walking beam type heating furnace, the gap L between the preceding slab and the succeeding slab is determined by the following equation (1). .
L = (ΔW ₁ + ΔW ₂ ) / 2 + α (1)
here,
ΔW ₁ : The amount of thermal expansion in the width direction of the preceding slab calculated from the charging temperature of the preceding slab and the setting temperature when extracting the slab ΔW ₂ : From the charging temperature of the succeeding slab and the setting temperature when extracting the slab Calculated amount of thermal expansion α of the trailing slab in the width direction: Minimum slab interval of the walking beam furnace

The above invention
When a plurality of slabs are continuously charged and heated in the walking beam type heating furnace, the slab width and slab at the time of charging of the preceding slab and the succeeding slab to be charged following the preceding slab on the transfer table Measuring the temperature;
Based on the slab width and slab temperature of each slab and the extraction set temperature, calculating the amount of thermal expansion in the heating furnace of these slabs;
Obtaining a transport stop signal of the walking beam heating furnace and estimating the tail end position of the preceding slab;
The succeeding slab can be realized by operating so as to include the step of determining and inserting the gap L between the preceding slab and the succeeding slab according to the equation (1).

  By this invention, the filling rate of the slab to a heating furnace can be improved, and the improvement of productivity of a hot-rolled steel material can be aimed at.

FIG. 1 is a conceptual diagram of a charging-conveying-extracting mechanism of a walking beam heating furnace to which the present invention is applied. Loading of this type - conveying - the walking beam type heating furnace having an extraction mechanism, slab S (S ₁ to S _n) is conveyed from the slab yard (not shown) to the charging roller 11, walking beam type by pusher 14 It is placed on the moving beam 12 of the heating furnace. In this state, the moving beam 12 repeats the forward, descending, retracting, and ascending cycle, and the slab S is repeatedly placed in the moving beam 12 and the stationary beam 13 in the furnace. And is placed on the extraction roller table 15 by the extractor 16 at the end of the heating furnace. Note that the slab charging-conveying-extraction in the walking beam heating furnace is arranged so that the longitudinal direction of the slab S is orthogonal to the conveying direction, that is, the width direction of the slab S is the conveying direction. This is well known.

Slab S _1, S ₂ in this moving state, the distance ··· S _n-1, S _n becomes smaller gradually due to thermal expansion of the slabs. That is, as shown in FIG. 2 (A), in the initial charge is, between the preceding slab S ₂ and succeeding slab S _1, even though placed spacing L, and the slab temperature rises by heating Thus, finally, as shown in (B), the slab widths W ₁ and W ₂ become W ₁ + ΔW ₁ and W ₂ + ΔW ₂ respectively. As a result, the separation distance between the slabs S ₁ and S ₂ is α = L-1 / 2 (ΔW ₁ + ΔW ₂ )
It becomes. The slab width W was measured as the maximum width of the slab width measured by a normal width meter, and was set to W ₁ and W ₂ for the slabs S ₁ and S ₂ , respectively.

Thus, even if the separation distance between the preceding slab S ₂ and the succeeding slab S ₁ is reduced, if there is a minimum slab interval for operating the walking beam heating furnace, the furnace can be operated. If the distance between the preceding slab S ₂ and the following slab S ₁ is determined as described above, the slab filling rate of the walking beam heating furnace can be maximized. Under such consideration, in the present invention, when continuously charging and heating a plurality of slabs in the walking beam type heating furnace, the gap L between the preceding slab and the succeeding slab when charging the slab,
L = (ΔW ₁ + ΔW ₂ ) / 2 + α (1)
It shall be determined by
here,
ΔW ₁ : The amount of thermal expansion in the width direction of the preceding slab calculated from the charging temperature of the preceding slab and the setting temperature when extracting the slab ΔW ₂ : From the charging temperature of the succeeding slab and the setting temperature when extracting the slab The amount of thermal expansion α in the width direction of the succeeding slab calculated is the minimum slab interval of the walking beam type heating furnace.

α are those defined as the minimum tracking margin of walking beam type heating furnace, it will be described with reference to FIG. 1, a slab of immediately behind the slab S _n by the extractor in a heating furnace end S _n- It is defined as the distance that can be extracted without interfering with ₁ . In practice, in determining the margin α, the slab heating temperature error, dimensional error, and shape factors such as warpage are further taken into account. Consider a size that can reliably prevent the occurrence of crimping accidents. This margin α varies depending on the size of the heating furnace, the maximum heating temperature, the size and material of the charging slab, and is about 10 to 15 mm empirically.

  In order to realize the above conditions and achieve the object of the present invention, for example, as shown in FIG. 3, a heating furnace 10 is added to a heating furnace control device 21, and a slab position calculation device 22 and a pusher control device 23 are provided. A configuration having a control system provided may be performed as described below. Hereinafter, this operation procedure is shown as an example.

First, when the upper conveying table 11 passes a preceding slab S ₂ and the following slab S _1, these slabs width and slab temperature measurements, they each preceding slab entry side information S _1E (W _1E, T _1E ), S _2E (W _2E , T _2E ) are input to the slab position calculation device 22 and stored. Further, the slab position calculation device 22 is inputted with the extraction set temperatures of these slabs as T _1D and T _2D , respectively. Here, the slab temperatures (T _1E , T _2E ) of the slabs S ₁ and S ₂ are measured as the highest temperature among the slab surface temperatures measured by the radiation thermometer.

The slab heating furnace 10 and Misaoro, the slab S _n of terminal prepares the intensifier side together reach a predetermined heating temperature is completed, the slab S _n are extracted by extractor 16 to obtain the extracted signal, the furnace control The apparatus 21 transports the slab _Sn-1 from the heating furnace to a position where it can be extracted, and temporarily stops in that state. In this stopped state, the heating furnace control device 21 calculates the stop position of the moving beam 12 of the slab heating furnace 10, and transmits the information to the slab charging position calculation device 22 as moving beam stop position information. This moving beam stop position information is information about which stage the moving beam 12 of the slab heating furnace 10 is in ascending, advancing, descending or retreating, and at which position in any one of the above stages, This is the basis for calculating the stop position of the preceding slab, and hence its tail end position.

As described above, the slab insertion position calculation device 22 is provided with the slab entry side information S _1E regarding the preceding slab S ₂ and the succeeding slab S ₁ . Also, moving beam stop position information is given. Furthermore, when the charged prior slab S ₂ is charging position information of the preceding slab S ₂ from the pusher 14 is input. Thus, the slab loading position calculating unit 22, preceding the tail position of the slab S ₂ can be calculated, the position is stored in the slab loading position calculating device 22.

The tail position tip position of the trailing slab S ₁ based on is determined as follows. As described above, the slab charging position calculation device 22 receives and stores the preceding slab information, the following slab information, and the extraction set temperatures (T _1D , T _2D ) of these slabs. On the other hand, as the operating condition of the slab heating furnace 10, a margin allowance α is separately set and accumulated. Therefore, based on this information, the necessary gap L to be placed between the tail end of the preceding slab S ₂ and the tip of the succeeding slab S ₁ is as described above.
L = (ΔW ₁ + ΔW ₂ ) / 2 + α
Where ΔW ₁ = W ₁ × (T _1D− T _1E ) × β
ΔW ₂ = W ₂ × (T _2D− T _2E ) × β
β: Linear thermal expansion coefficient of the slab The linear thermal expansion coefficient β of the slab uses a value measured for each steel type, charging temperature, and extraction temperature.

The required gap L to be placed between the tail end of the preceding slab S ₂ and the tip of the succeeding slab S ₁ calculated in this way is input to the pusher control device 23, and the stroke amount of the pusher 14 is based on the gap L. And the trailing slab S ₁ is inserted at a predetermined position, that is, with a gap L between the tail end of the preceding slab S ₂ and the tip of the trailing slab S ₁ . It should be noted that the control accuracy of the stroke amount of the pusher 14 is preferably controllable on the order of 1 mm or less in accordance with the object of the present invention.

  By operating as described above, the slab filling rate can be improved in accordance with the object of the present invention. Hereinafter, embodiments of the present invention will be clarified by examples.

In accordance with the present invention, 17 slabs having a slab charging temperature of 100 ° C. and a slab width of 1000 mm are charged into a slab heating furnace and heated to 1000 ° C. In this case, the thermal expansion coefficient is 14 × 10 ⁻⁶ . Α: Minimum tracking margin of the walking beam type heating furnace: α is set to 13.6 mm.

From the above conditions, the thermal expansion amount of the preceding slab and the following slab is (1000-100) × 14 × 10 ^-6 = 12.6mm respectively.
And therefore
The gap between the leading slab and the trailing slab is
L = 13.6 + (12.6 + 12.6) /2=26.2mm
It becomes. In this case, the slab filling rate to the heating furnace is
R = (1000 + 12.6) × 17 / (1000 + 26.2) × 17 = 98.6%
It becomes.

On the other hand, when the gap L between the preceding slab and the following slab is a constant value of 30 mm, the slab filling rate is
R = 98.3%
The filling rate was improved by 0.5% according to the present invention.

Slab charging temperature: 800 ° C. The other conditions are the same as in Example 1. From the above conditions, the thermal expansion of the leading slab and the trailing slab is (1000-800) x 14 x ^10-6 = 2.8mm respectively.
And therefore
The gap between the leading slab and the trailing slab is
L = 13.6 + (2.8 + 2.8) /2=16.4mm
It becomes. In this case, the slab filling rate to the heating furnace is
R = (1000 + 2.8) × 17 / (1000 + 16.4) × 17 = 98.7%
It becomes.

On the other hand, when the gap L between the preceding slab and the following slab is a constant value of 30 mm, the slab filling rate is
R = 97.4%
The filling rate was improved by 1.3% according to the present invention.

It is a conceptual diagram of the charging-conveying-extraction mechanism of the walking beam type heating furnace to which the present invention is applied. It is explanatory drawing of the relationship between the gap | interval L between the slabs at the time of charging at the time of applying this invention, and the minimum tracking allowance (alpha) of a walking beam type heating furnace. Apply It is the schematic of the control system of the heating furnace for implementing this invention.

Explanation of symbols

10: Slab heating furnace
11: Loading roller
12: Moving beam
13: Fixed beam
14: Pusher
15: Extraction roller table
16: Extractor
21: Heating furnace controller
22: Slab charging position setting device
23: Pusher control device
S (S ₁ , S ₂ ,... S _n-1 , S _n ): Slab

Claims (2)

In charging and heating a plurality of slabs continuously in a walking beam furnace,
A method for inserting a slab into a walking beam heating furnace, wherein a gap L between the preceding slab and the following slab is determined by the following equation.
L = (ΔW ₁ + ΔW ₂ ) / 2 + α
here,
ΔW ₁ : Amount of thermal expansion in the width direction of the preceding slab calculated from the charging temperature of the preceding slab and the extraction set temperature of the slab ΔW ₂ : Calculated from the charging temperature of the succeeding slab and the extraction setting temperature of the slab Thermal expansion amount α in the width direction of the following slab: Minimum slab spacing of the walking beam furnace When continuously charging and heating a plurality of slabs in a walking beam type heating furnace, the slab width at the time of charging the preceding slab and the succeeding slab to be charged following the preceding slab on the transfer table, and Measuring the slab temperature;
Based on the slab width and slab temperature at the time of charging each slab and the set temperature at the time of extraction, calculating the amount of thermal expansion in the heating furnace of these slabs;
Obtaining a transport stop signal of the walking beam heating furnace and estimating the tail end position of the preceding slab;
The following slab is inserted by setting a gap L between the preceding slab and the following slab according to the following equation:
A method for charging a slab into a walking beam furnace.
L = (ΔW ₁ + ΔW ₂ ) / 2 + α
Here, ΔW ₁ : The amount of thermal expansion in the width direction of the preceding slab calculated from the charging temperature of the preceding slab and the extraction setting temperature of the preceding slab ΔW ₂ : From the charging temperature of the succeeding slab and the extraction setting temperature of the slab Calculated amount of thermal expansion α of the trailing slab in the width direction: Minimum slab interval of the walking beam furnace

Images