JPS61170508A - Method for erasing skid mark in continuous heating furnace - Google Patents

Abstract

PURPOSE:To erase effectively skid marks by providing an auxiliary skid beam to the point off the extension line of the plane view on the down stream of skid beam and calculating the temp. distribution on the bottom surface of a material to be heated which is transferred from the skid beam to the auxiliary skid beam. CONSTITUTION:The auxiliary skid beam 15 is provided at the point off the extension line of the plane view on the down stream of the skid beam 11 and a heater 13 is provided to face upward below the extension line at the point provided with the auxiliary skid beam 15. The temp. distribution on the bottom surface of the material 11 to be heated when said material is transferred from the beam 11 to the beam 15 is then calculated and the quotient of the difference between the max. temp. and min. temp. thereof and an average temp. is determined. The heating of the heater 13 is controlled in order to erase the skid mark in accordance with such quotient and the predicted value of the residual time for heating by the heater 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for erasing skid marks that occur on the lower surface of a material to be heated that is charged into a continuous heating furnace.

[Prior art]

The material to be heated, such as a slab material, charged into a continuous heating furnace is heated while being transferred on a skid beam attached to the furnace.Generally, the skid beam is water-cooled to support the slab. The lower surface of the slab material that is in contact with the skid button or skid beam is at a lower temperature than other parts that are not in contact with the skid button or skid beam, resulting in skid marks.

Since skid marks have a negative effect on the dimensional accuracy 9 quality of rolled products, it is desirable to prevent them from occurring.

In recent years, continuous heating furnaces have generally become more energy efficient.
The plant has been upgraded and low-temperature extraction operations are being carried out, and for this reason the temperature inside the furnace is lower than before. However, as the temperature inside the furnace becomes lower, larger skid marks occur, which may limit the above-mentioned operation.

For this reason, various measures to prevent the occurrence of skid marks have been proposed. For example, method A (Japanese Patent Publication No. 42-1
5449), Method B (Special Publication No. 57-54529), in which a jet heating burner is installed on the furnace ceiling to locally heat the upper surface of the slab material where skid marks occur (Japanese Patent Publication No. 57-54529), a preheating zone on the upstream side of the furnace, The position of the skid beam in the soaking zone on the downstream side of the position of the skid beam installed in the tropical zone is set at a position that is out of the extension line of the skid beam on the upstream side, and the position where it contacts the skid beam of the slab material is changed, and the skid beam is Method C for suppressing the occurrence of marks (Revueda
Me'tallargie-CI T Mars
1984) etc.

[Problem that the invention seeks to solve]

However, electric resistance heating using Method A has technical problems such as durability and safety in applicability to large industrial furnaces. In addition, in method B, the slab material is locally heated from above, but this does not eliminate heat radiation to the skid beam at the bottom of the slab (it was impossible to prevent skid marks from occurring.Also, in method B, the hearth is installed A general method for jet heating equipment is described, but this method damages the skid beam and is not practical.Method C requires a long time to erase skid marks and is difficult to use in standard heating processes. In this case, the skid marks cannot be erased within the heating time, and in addition, new skid marks are generated at the skid beam position in the soaking zone, resulting in an increase in the number of skid marks. In addition, in all of the above methods A, B, and C, optimal heating control was not performed according to the steel type, dimensions, heating history, etc., and the temperature at the skid mark portion was simply increased. .

Furthermore, no technology has yet been developed to accurately measure the temperature of the bottom surface of the slab material while it is in the heating furnace or immediately after it has been extracted from the heating furnace. Attempts to implement controls were impossible.

[Means for solving problems]

The present invention has been made in view of the above circumstances, and is designed to prevent the skid beam near the extraction port from coming into contact with the skid mark portion formed on the lower surface of the material to be heated that is transferred on the skid beam of the continuous heating furnace. In addition to installing it away from the skid mark part, a heating device is installed on the extension of the skid mark part on the upstream side to heat the skid mark part, and the temperature difference between the skid mark part and the average temperature of the bottom surface of the slab is calculated. It is an object of the present invention to provide a method for erasing skid marks in a continuous heating furnace, which can erase skid marks by determining the temperature difference and eliminating the temperature difference by performing auxiliary heating.

A skid mark erasing method in a continuous heating furnace according to the present invention is a method for erasing skid marks on the lower surface of a material to be heated that is transferred on a skid beam in a continuous heating furnace. An auxiliary skid beam is provided at a location away from the auxiliary skid beam, and a heating device is provided upward below the extension line of the auxiliary skid beam, so that when the material to be heated is transferred from the skid beam to the auxiliary skind beam, Calculate the temperature distribution on the lower surface of the heated material, find the quotient of the difference between the maximum temperature and the minimum temperature and the average temperature, and erase the skid marks based on this quotient and the predicted value of the remaining heating time by the heating device ( It is characterized by controlling the heating of the heating device.

〔Example〕

The present invention will be specifically explained below based on the drawings.

FIG. 1 is a schematic diagram showing the implementation state of the present invention, FIG. 2 is a plan sectional view of a continuous heating furnace, and FIG. 3 is an enlarged sectional view taken along the line ■-III in FIG. A slab material charged into a beam-type continuous heating furnace IO is shown. The slab material l is placed, for example, on two horizontal and parallel fixed skid beams 11.11, and two moving skids are respectively directed to the outside of the fixed skid beams 11.11 by rotating cranks (not shown). The movement of the beam 12.12 transports it in its width direction (in the direction of the open arrow). The slab material l is charged through the charging port 10d and then transferred to the preheating zone 10a of the heating furnace lO.

It is sequentially heated in the heating zone 10b and the soaking zone 10c.

The downstream end of the fixed skid beam 11.11 is connected to the heating furnace I.
It is bent downward at a position upstream of the width direction dimension of the slab material 1 from the O extraction port 10e. Upward burner portions 13a are located below the downstream extension of the downstream end of the fixed skid beam ratio li between the downstream end of the fixed skid beam 11.11 and the extraction port 10e.

13a is provided, and the burner portions 13a, 13a
each has a plurality of burners in the width direction of the slab material 1. Fuel is supplied to the burner sections 13a, 13a with the flow rate adjusted by the local heating device 13.

A fixed skid beam 1 is provided between the burner parts 13a and 13a.
An auxiliary skid beam 15, which is slightly longer than the width of the slab material 1, is fixed on the downstream side of the downstream end of the slab material 1 at the same direction and height as the fixed skid beam 11. The slab material l can be transferred from the fixed skid beam 11 onto the auxiliary skid beam 5.

Each ceiling side of the pre-heating zone 10a, heating zone 10b, and soaking zone 10c.

Thermometers 16, 16, .

The skid mark index calculation device 2 is a heating furnace 1 for slab material l.
At every predetermined time interval from charging to extraction, calculate the skid mark index described below, which has a strong correlation with the temperature distribution on the bottom surface of the slab material 1 and the dimensional accuracy 2 quality of the rolled product, and
The calculated skid mark index is output to the local heating control device 3. The skid mark index calculation device 3 uses a well-known method of diffracting the temperature (T i + j) distribution on the bottom surface of the slab material 1 and the partial differential equation of skidmer-dimensional unsteady heat conduction from the difference near-field, for example, on the bottom surface of the slab material 1. The following formulas (11 and (21) are set.

(Margins below) ρ・C−dx−dy2 ρ Tatami c −dxedy ql −σ ・φ1 ・Pi +σ・φ2 ・ (1−Fi) Amount of heat received from the furnace wall and skid beam per surface area λ of the varnish slab material 1 Thermal conductivity ρ Specific gravity of varnish slab material 1 C Specific heat of varnish slab material σ: Stefan Boltzmann constant φI Overall heat absorption rate of varnish slab material 1 from the furnace wall φ2 Overall heat absorption rate of varnish slab material 1 from the skid beam Note that T i , j, etc. indicate the temperature at the center point of the area where the slab material l is divided by a constant length pitch dx and a constant thickness pitch dy, as shown in Figure 4, and the subscript i indicates the length of the slab material l. The subscript j indicates the area in the thickness direction, and in the case of the bottom surface of the slab, j=1. Further, Ti, j', etc. are the temperatures in the region 1+J, etc. calculated at the previous point in time.

In addition, Fi is the shape of the shape between the first region of the bottom surface of the slab material l and the furnace wall [ratio not disturbed by the skid beam (0≦
Pi≦1)]; Tf is the furnace wall temperature input from the thermometer 16 etc. at the time of the calculation.

T3 is the skid beam temperature at the time of the calculation, dt is the residence time of the slab material in the furnace from the previous time to the time of the calculation, and since Ts is approximately constant during normal furnace operation, it is taken as a constant.

The skid mark index calculation device 2 receives signals regarding the in-furnace position of each slab material l from a host computer (not shown), and calculates δ1°Ti,j using equations (1) and (21). Necessary information, namely λ, ρ.

C, dX+ d3'+ ' + φ1. φ2,
Fi, Ts are set, and the same slab material 1
The temperature Ti,j' calculated at the previous point in time is stored.

The skid mark index calculation device 2 takes in the furnace wall temperature Tf from the thermometer 16 corresponding to the position of the applicable slab material in the furnace based on the signal output from the host computer (not shown) at predetermined time intervals. The input signal Tf from a total of 16, the above (ll, +21 formula and the set λ, p, c
, σ, φ1. Calculate ql based on φ2, Fi + Fs + Ti, etc., and calculate the value of slab material l in each area of slab material 1.
From the temperature values in each region of the lower surface, the difference ΔT (>O) between the maximum value and the minimum value and the quotient divided by each of the lower surfaces (hereinafter referred to as skid mark index) are output to the control device 3. 6th
The figure is a diagram showing an example of temperature distribution in a cross section in the longitudinal direction of the slab material l based on Ti and j calculated by the skinned mark index calculation device 2 at a certain point in time.

The time prediction device 4 receives the extraction pitch of the preceding slab material from a host computer (not shown), the dimensions of the slab material 1 based on the rolling plan,
Information regarding the operation schedule, such as the number of steel types and the like, is input, and the scheduled extraction time of the corresponding slab material l is determined based on the extraction pitch. The determined value is input to the local heating control device 3.

The local heating control device 3 adjusts the fuel supply amount of the skid mark index calculation heating device 13 to make it approximately zero at the time of extraction. In other words, the heating temperature of the local heating device 13 is adjusted over time so that the bottom surface temperature distribution of the slab material l at the time of extraction is calculated, the skid at the time of extraction is calculated, and the skid mark index is matched within the target extraction time content range. It is calculated at predetermined time intervals until the scheduled extraction time of the applicable slab material I input from the prediction device 4. The obtained heating temperature is determined by the local heating device 1 each time the calculation is performed.
Output to 3.

In the local heating control device 3, the following formulas (3) and (41) are set for the temperature Ti, j, etc. in each region of the lower surface of the slab material l at the time of extraction, and the skin temperature, for example, for the lower surface of the slab.

(Margins below) ρ ・ c -dx-dy ql-σ ・φ1 ・Fi +σ ・φ3 ・Gi +σ ・φ2 ・ (IFi-Gi)...(4) However, ql The bottom surface of varnish slab material l is the unit time. , Heat received per unit surface area from the furnace wall, skinned beam, and local heating device φ3 Overall heat absorption rate of the varnish slab material 1 by the local heating device TL Heating temperature of the local heating device Gi Area including the bottom surface of the mini-slab 1 and local heating In addition, the local heating control device 3 calculates the information necessary to calculate q2, Tt, and j from equations (31, (41), respectively, that is, λ
, ρ, c + dx+ dt, σ, φ1. φ2
1 φ3, Pi.

TL + Ts, Gi are set, and the previously calculated temperatures Ti, j', etc. of the same slab material 1 are stored.

Note 1. (3), (T i, j' in formula 41
The initial setting values are the skid mark index T i immediately before the relevant slab material 1 is transferred onto the auxiliary skid beam 15.
, j, etc. are used.

The local heating control device 3 is configured to receive an input signal from a host computer (not shown) immediately before the slab material l is transferred from the fixed skid beam 11 onto the auxiliary skid beam 15. When input, the extraction time of the relevant slab material 1 is taken from the time prediction device 4, and the time from the taken time to the extraction time is used as the time during which the relevant slab material 1 is locally heated on the auxiliary skid beam 15,
(For the target skid mark index ΔT /Taν at time points 31 and +41, however, ε: determines whether the reference value (>0) is reached or not. Continue calculation of the target heating temperature TL of the heating device 13, When a value satisfying equation (5) is obtained, the heating temperature TL flaw signal is output to the local heating device 13.

When the local heating device 13 receives the signal TL, the local heating device 13 receives the input signal TL.
The opening degree of a valve (not shown) is adjusted so that the amount of fuel blown out is associated with the amount of fuel blown out.

FIG. 7 is a flowchart summarizing the above. The skid mark index calculation device 2 calculates the time from the previous calculation time to the next calculation time for a certain slab material l, and at that point, the furnace wall temperature Tf where the relevant slab material l is located is measured by a corresponding thermometer. 16 and inputted from a host computer (not shown), it is determined whether the applicable slab material is on the fixed skid beam 11 or the auxiliary skid beam 15, and Slab material 1 is fixed skid beam 1
If it is above 1, repeat this again.

When the relevant slab material 1 is on the auxiliary skid beam 15, the calculated values of temperatures Ti and j in each region of the lower surface of the slab material 1 are output to the local heating control device 3.

When the local heating control device 3 receives both of the above calculated values, it takes in the furnace wall temperature Tf from the thermometer 16 in the soaking zone 10c, and assumes the target heating temperature TL (3).

(41, (Calculate formula 51, that is, the temperature at each point of the slab material l at the time of extraction and the skid mark index predictor are (
5) Determine whether or not the formula is satisfied, and if not, change the target value of the heating temperature TL of the local heating device 13 and perform (5)
) Calculate until the formula is satisfied. Then, the satisfying heating temperature TL is output to the local heating device 13.

As a result, the amount of fuel supplied to the local heating device 13 is controlled to an appropriate value, and skid marks on the slab material 1 are erased by the combustion flame.

The slab material 1 on the auxiliary skid mark 15 from which the skid mark has been erased is placed on the downstream side of the continuous heating furnace IO, and an extractor (not shown) that can move back and forth in the direction of transport of the slab material 1 and can move up and down. After being taken out, it is sent to, for example, a rolling process and rolled.

Although the above embodiment is applied to a walking beam type continuous heating furnace, the present invention is of course not limited to this and can be applied to any continuous heating furnace equipped with a skid beam.

Also, although the above explanation applies to slab materials,
Of course, the present invention is applicable not only to slab materials but also to metal materials in general.

Furthermore, the above actual h&! In the example, skid marks on the slab material 1 are erased immediately before extraction from the heating furnace, but in the present invention, the position of the skinned beam is shifted not only immediately before extraction, but also during the extraction, and the local heating device is also used. It is also possible to provide a heating device. Heating in this manner is advantageous in shortening the time between charging and extraction.

〔effect〕

100 slabs from among the slabs transferred through a continuous heating furnace under substantially the same conditions are heated and rolled according to the present invention, and half of one side in the length direction of the top surface of the rolled steel plate is heated with a temperature needle. Actual measurement (Due to rolling, the temperature distribution on the bottom surface of the slab material may appear on the top surface of the steel plate).

Figure 8 is a graph showing the actual measured value (dashed line) of the steel plate temperature after rolling, with the vertical axis representing the temperature of the steel plate after rolling. After rolling the steel plate, the results were measured in the same way as before (actual #jA
) are also shown.

As can be understood from this figure, in the past, the temperature at the skinned mark position was lower, at about 70°C, compared to the high temperature part at the longitudinal end of the steel plate, but with the present invention, this can be reduced to about 30°C. It became possible. This improves the dimensional accuracy and quality of the finished product.

Figure 9 is a graph showing the skid mark index applied to the temperature change of the rolled material obtained by rolling the slab material (instead, it is a graph showing the skid mark index applied to the temperature change of the rolled material obtained by rolling the slab material according to the present invention). For this reason, Figure 1O shows the skid mark index related to temperature changes for conventionally rolled materials.As can be understood from these two figures, conventionally rolled materials had a large skid mark index and a wide range of variation. However, according to the present invention, the skid mark index and the width of the variation can be reduced.

As detailed above, according to the present invention, it is possible to reduce or eliminate the skid mark index, thereby improving the dimensional accuracy and quality of the rolled material, thereby increasing operational stability during processing, Further, the present invention has excellent effects such as ease of low-temperature extraction operation.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing the implementation state of the present invention, Fig. 2 is a plan sectional view of a continuous heating furnace, Fig. 3 is an enlarged sectional view taken along the m-m line in Fig. 2, and Fig. 4 is a temperature measurement position. FIG. 5 is a graph showing the temperature distribution on the lower surface of the steel sheet predicted by the present invention, FIG. 6 is a graph showing an example of the temperature distribution in the cross section of the steel sheet,
FIG. 7 is a flowchart showing the heating control contents of the present invention;
Figures 8.9 and 10 are detailed illustrations of the present invention. 1... Rope plate 2... Skid mark index calculation device 3
...Local heating control device 4...Time prediction device 13
... Local heating device 15 ... Auxiliary skid beam patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono 4 diagrams! Ip Figure 5 Figure 6 Notebook 8

Claims (1)

[Claims] 1. In a method for erasing skid marks on the lower surface of a material to be heated that is transferred on a skid beam in a continuous heating furnace, an auxiliary device is provided at a point on the downstream side of the skid beam that is outside the extension line in plan view. A skid beam is provided, and a heating device is provided upward below the extension line of the location where the auxiliary skid beam is provided, and temperature distribution on the lower surface of the heated material when the heated material is transferred from the skid beam to the auxiliary skid beam. is calculated, the quotient of the difference between the maximum temperature and the minimum temperature and the average temperature is determined, and the heating control of the heating device is performed to erase the skid mark based on this quotient and the predicted value of the remaining heating time by the heating device. A method for erasing skid marks in a continuous heating furnace, characterized by: