JP7225066B2 - Steel temperature prediction method - Google Patents

Description

The present invention relates to a temperature prediction method for steel materials.

When a steel material is heated, for example, in a continuous heating furnace, the temperature history of the steel material in the heating furnace greatly affects the quality of the steel material. If the deviation from the target temperature history is large, a phenomenon called decarburization may occur, and desired mechanical properties may not be obtained. Therefore, in order to ensure product quality, it is necessary for the operator to appropriately control the temperature history of the steel material in the heating furnace.

Accurate steel temperature prediction is necessary for operators to properly control the temperature history. On the other hand, from the viewpoint of productivity, it is also necessary to suppress the time and cost of temperature prediction. Therefore, a method has been proposed for predicting the temperature of steel materials by correcting the overall heat absorption rate (heat transfer efficiency from the furnace to the steel materials) based on the number of burners used (see Japanese Patent Laid-Open No. 2018-3084). .

JP 2018-3084 A

In a heating furnace, even if the number of burners used is the same, the flow rate of fuel supplied to the burners may differ depending on the operating conditions. In this case, it is difficult to sufficiently improve the accuracy of predicting the temperature of the steel material with the method of Patent Document 1, in which the correction is performed based on the number of burners used.

In view of the above circumstances, it is an object of the present invention to provide a method for predicting the temperature of a steel material that can accurately predict the temperature of the steel material in the heating furnace.

In order to solve the above problems, the present inventors conducted intensive research as follows. That is, for example, as a method of predicting the temperature of the steel material in the heating furnace, the temperature in the heating furnace is measured at positions upstream and downstream of the burner in the conveying direction of the steel material, and the temperatures at these two positions (Fig. 5 (T1, T2) of (T1, T2)) is calculated by calculating the temperature at each position in the heating furnace (straight line Ls shown by the dashed line in FIG. 5), and the temperature of the steel material can be predicted based on each temperature .

However, between the above two positions, the heat from the burner causes the temperature in the heating furnace to rise above the straight line, and the degree of increase depends on the combustion load of the burner, that is, the flow rate of the fuel supplied to the burner. fluctuate. Therefore, the accuracy of the predicted temperature based on the straight line cannot be said to be sufficient with the above method. Therefore, the temperature in the heating furnace is calculated based on the fuel flow rate of the burner between the above two positions and the burner, and in addition to the temperatures (T1, T2) at the above two positions, the calculated temperature (Fig. 5 (K1, K2) of (K1, K2), the inventors have found that the temperature of the steel material at each position can be accurately predicted by predicting the furnace temperature at each position, and have completed the present invention.

That is, an invention made to solve the above problems is a method for predicting the temperature of steel material conveyed in a heating furnace, wherein the heating furnace comprises one or more burners arranged along the conveying direction of the steel material. and measuring the temperature in the heating furnace at a first position upstream and a second position downstream from the burner in the conveying direction; and measuring a fuel flow rate of the burner. , a third position between said first position and said burner and said burner and said second position based on the measured furnace temperatures at said first position and said second position and the measured fuel flow rate of said burner; the measured furnace temperature at the first position and the second position, and the calculated furnace temperature at the third position and the fourth position between predicting the furnace temperature at each position in the conveying direction in the heating furnace based on, calculating the heat flux at each position based on the predicted furnace temperature, and calculating the calculated heat flux and calculating the temperature of the steel material at each position based on the in-furnace temperature prediction step at each position based on the measured in-furnace temperatures at the first position and the second position. and a step of calculating a corrected in-furnace temperature obtained by correcting the reference in-furnace temperature using the calculated in-furnace temperatures at the third position and the fourth position. temperature prediction method.

The temperature prediction method of the steel material is based on the calculated in-furnace temperatures at the third and fourth positions in addition to the measured in-furnace temperatures at the first and second positions. By predicting the furnace temperature at each position of , the furnace temperature at each position can be predicted according to the fuel flow rate of the burner. In the prediction of the furnace temperature, the reference furnace temperature based on the measured temperatures at the first position and the second position is calculated using the calculated furnace temperature at the third position and the fourth position. By correcting, the furnace temperature at each position can be predicted with high accuracy. The heat flux is calculated based on the corrected in-furnace temperature thus obtained, and the temperature of the steel material is calculated based on this heat flux, thereby accurately predicting the temperature of the steel material in the heating furnace. can be done.

According to the steel temperature prediction method of the present invention, it is possible to accurately predict the temperature of the steel in the heating furnace.

It is a flow figure showing the procedure of the temperature prediction method of steel materials of one embodiment of the present invention. FIG. 4 is a plan view of the interior of the heating furnace showing the arrangement of burners and thermometers, and is a plan view seen from above the conveying surface. It is a side view in a heating furnace which shows arrangement|positioning of a burner and a thermometer. FIG. 4 is a plan view of the inside of the heating furnace showing temperature acquisition positions in the conveying direction of the steel material, and is a plan view seen from above the conveying surface. FIG. 3 is a plan view schematically showing the relationship between each position in the heating furnace in the conveying direction of the steel material and the furnace temperature at each position. 5 is a graph showing the relationship between each position from position N1 to position N6 in the heating furnace in the conveying direction in Test Example 1 and the predicted in-furnace temperature directly above the steel material at each position.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[Method for predicting temperature of steel]
The method for predicting the temperature of a steel material is a method for predicting the temperature of a steel material conveyed in a heating furnace, wherein the heating furnace is equipped with one or more burners arranged along the conveying direction of the steel material. The method.

As shown in FIG. 1, the steel material temperature prediction method includes a step of measuring the temperature inside the heating furnace at a first position on the upstream side and a second position on the downstream side of the burner in the conveying direction (furnace internal temperature measurement step) S1, a step of measuring the fuel flow rate of the burner (fuel flow rate measurement step) S2, and based on the measured furnace temperature at the first position and the second position and the measured fuel flow rate of the burner and calculating the furnace temperature (correction furnace temperature) at a third position between the first position and the burner and a fourth position between the burner and the second position (correction furnace temperature calculation step) S3, the measured furnace temperature at the first position and the second position, and the calculated furnace temperature at the third position and the fourth position (correction furnace temperature) predicting the furnace temperature at each position in the conveying direction in the heating furnace (furnace temperature prediction step) S4, and calculating the heat flux at each position based on the predicted furnace temperature The method includes a step (heat flux calculation step) S5 and a step (steel temperature calculation step) S6 of calculating the temperature of the steel material at each position based on the calculated heat flux. In addition, "each position in the transfer direction in the heating furnace" refers to an arbitrary position in the transfer direction in the heating furnace. Further, in FIG. 1, instead of showing the in-furnace temperature prediction step S4, the following steps are shown.

Specifically, in this embodiment, as shown in FIG. The step of calculating the reference furnace temperature at each position (reference furnace temperature calculation step) S41, and the correction furnace temperature at the third position and the fourth position are used to correct the reference furnace temperature. and a step of calculating the corrected in-furnace temperature (corrected in-furnace temperature calculation step) S42.

As shown in FIGS. 2 and 3, a heating furnace to which the steel material temperature prediction method is applied includes the one or more burners 1a, 1b, 1c, and 1d. The burners 1a to 1d are arranged along the conveying direction D of the steel material (the direction of the white arrow in the figure). The burners 1a-1d have nozzles for ejecting flames. This nozzle is supplied with fuel for injecting the flame. The orientation of this nozzle is not particularly limited. As for the direction of the nozzle, for example, the direction that intersects the conveying direction of the steel material is preferable, and as shown in FIGS. 2 and 3, the direction that intersects the conveying direction of the steel material is more preferable. A so-called side burner is exemplified as a burner having such a nozzle. As this burner, for example, an axial flow burner can be used.

In the embodiment shown in FIGS. 2 and 3, a heating furnace provided with the side burners above and below the conveying surface 10 of the steel material A is used. In addition, the conveying surface 10 is a surface on which the steel material A is conveyed by a walking beam. 2 and 3, a pair of burners 1a are arranged above the conveying surface 10 and upstream in the conveying direction, a pair of burners 1b are arranged below the conveying surface 10 and upstream in the conveying direction, and burners 1b are arranged above the conveying surface 10 and in the conveying direction. A pair of burners 1c are arranged downstream in the direction, and a pair of burners 1d are arranged below the conveying surface 10 and downstream in the conveying direction, but the number and positions of the burners are not limited to this. Further, the heating furnace may be configured to have a plurality of heating zones, with the configuration shown in FIGS. 2 and 3 as one heating zone.

The upstream burner 1a and the burner 1b are arranged at the same position (position N3 in FIG. 4) in the conveying direction D of the steel material A. As shown in FIG. The downstream burners 1c and 1d are arranged at the same position (position N4 in FIG. 4) in the direction in which the steel material A is conveyed.

The shape of the steel material targeted by the method for predicting the temperature of the steel material is not particularly limited, and the method can be applied to steel bars, steel plates, and the like. In addition, the final heating temperature of the steel material is, for example, 1000° C. or higher and 1200° C. or lower.

A first thermometer 7a for measuring the temperature in the furnace is arranged at a first position (position N1 in FIG. 4) on the upstream side in the conveying direction of the upstream burners 1a and 1b in the heating furnace. Specifically, the first thermometer 7a measures the position of the first opening on the charging side of the steel material A in the heating furnace (position Ns in FIG. 4) and the position N3 of the upstream burners 1a and 1b. placed in between. A second thermometer 7b for measuring the temperature inside the furnace is arranged at a second position (position N6 in FIG. 4) downstream in the conveying direction from the downstream burners 1c and 1d in the heating furnace. Specifically, the second thermometer 7b is located between the position of the second opening on the extraction side of the steel material A in the heating furnace (position Nf in FIG. 4) and the position N4 of the downstream burners 1c and 1d. placed in Examples of the first thermometer 7a and the second thermometer 7b include conventionally known thermocouples. These first thermometer 7a and second thermometer 7b are used by being inserted into the heating furnace. 2 and 3 show only the temperature measurement units arranged at the tips of the first thermometer 7a and the second thermometer 7b.

<Furnace temperature measurement process>
In the in-furnace temperature measuring step S1, measured in-furnace temperatures T1 and T2 at positions N1 and N6 are measured by the first thermometer 7a and the second thermometer 7b (see FIGS. 4 and 5). As shown in FIG. 5, the horizontal axis is the conveying direction D, the vertical axis is the temperature T, and the measured furnace temperature T1 at the position N1 and the measured temperature T1 at the position N6 are measured at the coordinates where the vertical axis and the horizontal axis intersect at the position Ns. A straight line passing through the in-furnace measured temperature T2 is a reference temperature straight line Ls (broken line in FIG. 5), which will be described later.

<Fuel flow rate measurement process>
In the fuel flow rate measurement step S2, the fuel flow rate (total fuel flow rate) F at the burner 1a, the burner 1b, the burner 1c and the burner 1d is measured. A conventionally known flow meter can be used for this measurement. When the fuel flow rate of each of the burners 1a to 1b fluctuates during operation of the heating furnace, the total fuel flow rate F fluctuates accordingly.

<Correction Furnace Temperature Calculation Process>
In the correction in-furnace temperature calculation step S3, a third position between the position N1 and the position N3 (Fig. 4) and a fourth position (position N5 in FIG. 4) between positions N4 and N6.

Regarding the position N2, the effect of the heat from the burners 1a to 1d (especially the burners 1a and 1b on the upstream side) on the temperature inside the furnace on the upstream side in the conveying direction is investigated in advance. is determined as the position N2 for calculating the correction in-furnace temperature K1, which is the limit of the influence of the heat on the in-furnace temperature, i.e., the position where no influence is exerted (position in the conveying direction in the heating furnace). . For example, the position N2 is shifted little by little between the position N1 and the position N3, and the furnace temperature calculation step S1 to the steel material temperature calculation step S6, which will be described later, are performed. can be determined as

On the other hand, for the position N5, the effect of the heat from the burners 1a to 1d (particularly the downstream burners 1c and 1d) on the temperature inside the furnace downstream of these in the conveying direction was examined in advance. ~ 1d is the limit of affecting the furnace temperature, that is, the position where it does not affect (the position in the conveying direction in the heating furnace) is determined as the position N5 for calculating the correcting furnace temperature K2. do. For example, the position N5 is gradually shifted between the position N4 and the position N6, and the furnace temperature calculation step S1 to the steel material temperature calculation step S6, which will be described later, are performed. can be determined as

Specifically, for example, at the position N2 on the upstream side of the burner, the heat emitted from the burner has a relatively large effect on the temperature inside the furnace. Taking this into consideration, the correction furnace temperature K1 at the position N2 can be calculated, for example, based on the following equation (1). The minimum value Fmin and the maximum value Fmax of the fuel flow rate F of the burner used in the following formula (1) are based on the operating results of the heating furnace, such as the type, width, thickness, length, and conveying speed of the steel material. can be determined.
K1=T1+(F-Fmin)×(K2-T1)/(Fmax-Fmin) (1)
K2: Furnace temperature for correction at position N5 [°C]
T1: measured furnace temperature at position N1 [°C]
F: measured value of fuel flow rate [Nm ³ /h]
Fmin: Minimum value of fuel flow rate [Nm ³ /h]
Fmax: Maximum value of fuel flow rate [Nm ³ /h]

On the other hand, for example, at position N5 downstream of the burner, the effect of heat emitted from the burner is considered to be relatively small. Taking this into consideration, it can be assumed that the correction in-furnace temperature K2 at the position N5 is positioned on a reference temperature straight line Ls, which will be described later, as shown in FIG. The correction in-furnace temperature K2 at the position N5 can be calculated, for example, based on the following equation (2).
K2={(T2-T1)/(D6-D1)}×(D5-D1)+T1 (2)
T1: measured furnace temperature at position N1 [°C]
T2: measured furnace temperature at position N6 [°C]
D1: Distance from position Ns to position N1 D5: Distance from position Ns to position N5 D6: Distance from position Ns to position N6

In this manner, the correction in-furnace temperature K1 at the position N2 and the correction in-furnace temperature K2 at the position N5 can be calculated from the above two equations (1) and (2). These temperatures K1 and K2 are used in a corrected in-furnace temperature calculation step S42, which will be described later.

When the fuel flow rate F becomes the maximum value (Fmax), K1=K2 in the above formula (1) (double-dot chain line Lc2 in the region between position N2 and position N5 in FIG. 5). . On the other hand, when the fuel flow rate F is the minimum value (Fmin), in the above formula (1), K1=T1 (two-dot chain line Lc1 in the region between the position N1 and the position N2 in FIG. 5) .

<Furnace temperature prediction process>
In the in-furnace temperature prediction step S4, based on the measured in-furnace temperatures T1 and T2 at the positions N1 and N6 and the correction in-furnace temperatures K1 and K2 at the positions N2 and N5, the transfer in the heating furnace The furnace temperature at each position in the direction D is predicted. Specifically, the following steps are performed as the in-furnace temperature prediction step S4.

(Reference Furnace Temperature Calculation Process)
In the reference in-furnace temperature calculation step S41, the reference in-furnace temperature at each position in the transport direction D is calculated based on the measured in-furnace temperatures T1 and T2 at the positions N1 and N6. This reference in-furnace temperature is a temperature used to calculate a correcting in-furnace temperature, which will be described later, and is a reference temperature to be corrected by this in-furnace temperature for correcting. Specifically, in the coordinates (horizontal axis: conveying direction D, vertical axis: temperature T) shown in FIG. A straight line passing through the measured in-furnace temperature T2 at the distance D6 from the position Ns) is calculated as a set of reference in-furnace temperatures at each position (reference in-furnace temperature straight line Ls indicated by a dashed line in FIG. 5). This reference in-furnace temperature straight line Ls indicates that the distance of an arbitrary position N from the position Ns and the in-furnace temperature at this position N are in a linear relationship.

(Correction Furnace Temperature Calculation Process)
In the corrected in-furnace temperature calculation step S42, the corrected in-furnace temperature is calculated by correcting the reference in-furnace temperature using the corrected in-furnace temperatures K1 and K2 at the positions N2 and N5.

Specifically, in the region between the position N1 and the position N2 in the coordinates shown in FIG. It is calculated as a set of corrected in-furnace temperatures at the respective positions (corrected in-furnace temperature straight line Lc1 indicated by a solid line in FIG. 5). This corrected in-furnace temperature straight line Lc1 indicates that the distance of an arbitrary position N from the position Ns and the in-furnace temperature at this position N are in a linear relationship in the region between the positions N1 and N2. . That is, in this area, the temperature T(D) at an arbitrary position N is calculated by the following formula.
T(D)={(K1-T1)/(D2-D1)}×(D-D1)+T1
D1: Distance from position Ns to position N1 D2: Distance from position Ns to position N2 D: Distance from position Ns to any position N

In the region between the position N2 and the position N5, the straight line connecting the correction furnace temperature K1 at the position N2 and the correction furnace temperature K2 at the position N5 is the set of correction furnace temperatures at each position ( It is calculated as a corrected in-furnace temperature straight line Lc2) shown as a solid line in FIG. This corrected in-furnace temperature straight line Lc2 indicates that the distance of an arbitrary position N from the position Ns and the in-furnace temperature at this position N are in a linear relationship in the region between the positions N2 and N5. . That is, in this area, the temperature T(D) at an arbitrary position N is calculated by the following formula.
T(D)={(K2-K1)/(D5-D2)}×(D-D2)+K1
D2: Distance from position Ns to position N2 D5: Distance from position Ns to position N5 D: Distance from position Ns to any position N

In the region between the positions N5 and N6, a straight line (straight line Ls in FIG. 5) connects the correction in-furnace temperature K2 at the position N5 and the measured in-furnace temperature T2 at the position N6. This straight line matches the reference in-furnace temperature straight line Ls. That is, in this region, the temperature T(D) at an arbitrary position D is calculated by the following formula.
T(D)={(T2-K2)/(D6-D5)}×(D-D5)+K2
D5: Distance from position Ns to position N5 D6: Distance from position Ns to position N6 D: Distance from position Ns to any position N

In other regions, the temperature T(D) at an arbitrary position D exists on the reference in-furnace temperature straight line Ls. That is, between the position Ns and the position N1, the temperature T(D) at an arbitrary position N is calculated by the following formula.
T(D)=T1+{(T2-T1)/(D6-D1)}×(D-D1)
D1: Distance from position Ns to position N1 D6: Distance from position Ns to position N6 D: Distance from position Ns to any position N

On the other hand, between the position N6 and the position Nf (not shown in FIG. 5), the temperature T(D) at an arbitrary position D is calculated by the following formula.
T(D)={(T2-T1)/(D6-D1)}×(D-D6)+T2
D1: Distance from position Ns to position N1 D6: Distance from position Ns to position N6 D: Distance from position Ns to any position N

Then, the corrected in-furnace temperature T(D) at an arbitrary position N in the transport direction D is calculated as a set of corrected in-furnace temperatures (corrected in-furnace temperature curve) at each position. That is, the corrected in-furnace temperature T(D) at an arbitrary position N in the entire region from the position Ns to the position Nf is represented by a line connecting the plurality of straight lines (Ls, Lc1, Lc2).

As described above, when the fuel flow rate F of the burner is the maximum value Fmax, the correction in-furnace temperature K1 is equal to the correction in-furnace temperature K2. Therefore, the corrected in-furnace temperature curve in the region between the position N1 and the position N5 is two lines shown above the corrected in-furnace temperature straight line Lc1 and the corrected in-furnace temperature straight line Lc2 shown by solid lines in FIG. It is a line connecting two-dot chain lines (Lc1 and Lc2 represented by two-dot chain lines in FIG. 5). On the other hand, when the fuel flow rate F of the burner is the minimum value Fmin, the correction in-furnace temperature K1 becomes equal to the measured in-furnace temperature T1. Therefore, the corrected in-furnace temperature curve in the region between the position N1 and the position N5 is two dashed double-dot lines shown below the corrected in-furnace temperature straight lines Lc1 and Lc2 (Fig. 5 is a line connecting Lc1 and Lc2) represented by two-dot chain lines.

(Heat flux calculation process)
In the heat flux calculating step S5, the heat flux in the heating furnace at each position in the conveying direction D is calculated based on the corrected in-furnace temperature. Specifically, the heat flux in the heating furnace at each position is calculated based on the following equation (3). That is, by substituting the corrected in-furnace temperature at each position indicated by the corrected in-furnace temperature curve calculated above into the following equation (3), the heat flux in the heating furnace at each position is calculated. . By this calculation, the relationship between the heat flux at each position and the temperature of the steel material (that is, the temperature in the furnace on the surface of the steel material) is obtained. This relationship is used as a boundary condition in the steel material temperature calculation step S6, which will be described later.

In the above formula (3), q [W/m ² ] is the heat flux to the steel material, δ [W/m ² /K ⁴ ] is the Stefan Boltzmann constant, T _f [K] is the furnace temperature, T _s [K ] is the steel material surface temperature.

(Steel material temperature calculation process)
In the steel material temperature calculation step S6, the temperature of the steel material at each position in the conveying direction in the heating furnace is calculated based on the calculated heat flux. Specifically, using the above equation (3) as a boundary condition, the temperature from the surface to the inside of the steel material at each position in the conveying direction is Calculate the distribution.

上記式（４）中、ρ［ｇ／ｍ３］は鋼材の密度、ｃ［Ｊ／ｇ／Ｋ］は鋼材の比熱、Ｔ［Ｋ］は鋼材の温度、δｔ［ｓ］は微小時間、δｘ［ｍ］及びδｙ［ｍ］はそれぞれ微小区間、λｘ［Ｗ／ｍ／Ｋ］及びλｙ［Ｗ／ｍ／Ｋ］はそれぞれｘ方向及びｙ方向の熱伝導率である。ｘ方向は搬送面１０に垂直な方向である。ｙ方向は、搬送方向Ｄである。

In the above formula (4), ρ [g / m3] is the density of the steel, c [J / g / K] is the specific heat of the steel, T [K] is the temperature of the steel, δt [s] is the minute time, δx [ m] and δy[m] are the microsections respectively, and λx[W/m/K] and λy[W/m/K] are the thermal conductivities in the x and y directions respectively. The x direction is the direction perpendicular to the transport plane 10 . The y-direction is the transport direction D.

By performing such temperature prediction for each position in the conveying direction D at a plurality of points in the heating furnace, it is possible to predict the temperature of the steel material in the heating furnace. Further, by predicting the temperature of the steel material at each position in the heating furnace, for example, the predicted temperature of the steel material at the second opening (position Nf) of the heating furnace can be obtained. Since this predicted temperature can be regarded as the temperature of the steel immediately after extraction from the heating furnace, this predicted temperature can be used for operational control of the heating furnace.

[advantage]
The steel material temperature prediction method is based on the calculated furnace temperatures (correction furnace temperatures) at the third and fourth positions in addition to the measured furnace temperatures at the first and second positions. By predicting the furnace temperature at each position in the conveying direction in the heating furnace by using the above, it is possible to predict the furnace temperature at each position according to the fuel flow rate of the burner. In the prediction of the furnace temperature, the reference furnace temperature based on the measured temperatures at the first position and the second position is calculated using the calculated furnace temperature at the third position and the fourth position. By correcting, the furnace temperature at each position can be predicted with high accuracy. The heat flux is calculated based on the corrected in-furnace temperature thus obtained, and the temperature of the steel material is calculated based on this heat flux, thereby accurately predicting the temperature of the steel material in the heating furnace. can be done.

[Other embodiments]
The steel material temperature prediction method of the present invention is not limited to the above embodiment. For example, the steel temperature prediction method may include steps other than those described above, if necessary.

For example, in the above embodiment, the correcting furnace temperature K2 at the position N5 is on the reference furnace temperature straight line Ls. A correction furnace temperature K2 that does not exist may be calculated.

For example, in the above embodiment, the first thermometer 7a and the second thermometer 7b are arranged upstream and downstream of the burners 1a to 1d, respectively, but the arrangement and number of thermometers are particularly limited to the above embodiment. not. For example, in FIGS. 2 and 3, depending on the distance between the upstream burners 1a, 1b and the downstream burners 1c, 1d, there may be additional distances between the upstream burners 1a, 1b and the downstream burners 1c, 1d. A third thermometer may be arranged. In this case, between the first thermometer 7a and the third thermometer, and between the third thermometer and the second thermometer 7b, the furnace temperature measurement step S1 to the steel material temperature calculation step S6 are performed. you can go

EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limitedly interpreted based on the description of these examples.

Two types of steel material X whose thickness (dimension in the direction perpendicular to the conveying plane), width (dimension in the conveying direction), and length (dimension in the conveying direction and in the direction perpendicular to the conveying plane) are equal to each other, but whose components are different from each other and steel material Y, Test Examples 1 and 2 were performed on the heating furnace as shown in FIGS. 2 and 3 as follows.

(Test example 1)
・Example 1
For 472 steel materials X, as shown in FIG. The reference furnace temperature straight line Ls represented by the straight line connecting the measured furnace temperature T2 at the position N6 is corrected by the correction furnace temperature K1 at the position N2 and the correction furnace temperature K2 at the position N5. A corrected in-furnace temperature curve (straight line Ls, straight line Lc1 and straight line Lc2 shown in FIG. 5) was created. Using this corrected in-furnace temperature curve, the in-furnace temperature at each position in the transport direction (each position between the position Ns and the position Nf) was calculated. Using each calculated temperature, the temperature distribution from the surface to the inside of the steel material X at each position was predicted by the above-described formulas (3) and (4).

On the other hand, the surface temperature of the steel material X immediately after the steel material X was extracted from the second opening of the heating furnace (corresponding to the position Nf) was actually measured with a radiation thermometer. Then, it was compared with the predicted temperature of the surface of the steel material at the position Nf obtained above. Specifically, the deviation of the predicted temperature from the measured temperature (measured temperature−predicted temperature) was calculated as the standard deviation (1σ).

・Comparative example 1
For the 472 steel materials X, as shown in FIG. A reference furnace temperature straight line Ls (straight line Ls shown in FIG. 5) represented by a connecting straight line was created. Using the furnace temperature at each position in the conveying direction (each position between the position Ns and the position Nf) calculated based on the reference furnace temperature straight line Ls, each of the above equations (3) and (4) is used. The temperature distribution from the surface to the inside of the steel material X at each position was predicted. Otherwise, in the same manner as in Example 1, the measured temperature is compared with the predicted temperature of the steel material surface at the position Nf, and the deviation of the predicted temperature from the measured temperature (measured temperature - predicted temperature) is calculated as a standard. Calculated as deviation (1σ).

- Comparison between Example 1 and Comparative Example 1 The standard deviation obtained in Comparative Example 1 was set to 100%, and the ratio (percentage) of the standard deviation obtained in Example 1 to the standard deviation in Comparative Example 1 was calculated. By the way, it was 99%. Therefore, it was found that the variation in the steel material X was improved by 1% by correcting the reference furnace temperature (reference furnace temperature straight line Ls) as described above.

The predicted in-furnace temperature calculated by performing the same steps as in Example 1 is compared with the predicted in-furnace temperature calculated by performing the same steps as in Comparative Example 1 for the region from position N1 to position N6. An example of the result is shown in FIG. In FIG. 6, the predicted in-furnace temperature is indicated as "furnace temperature". 6, the horizontal axis is the transport direction D, the distance from the position N1 to the position N6 is 1.0, and the distance from the position N1 to any position N between these positions N1 and N6 is the position It is shown as a ratio to the distance from N1 to position N6. On the other hand, in FIG. 6, the vertical axis is the furnace temperature, the furnace temperature at the position Nf is 1.0, and the furnace temperature at the arbitrary position N is expressed as a ratio to the furnace temperature at the position Nf. show.

(Test example 2)
・Example 2
The predicted temperature at the position Nf was compared with the measured temperature in the same manner as in Example 1, except that 438 steel materials Y were used instead of the steel materials X.

・Comparative example 2
The predicted temperature at the position Nf was compared with the measured temperature in the same manner as in Comparative Example 1, except that 438 steel materials Y were used instead of the steel materials X.

- Comparison between Example 2 and Comparative Example 2 The standard deviation obtained in Comparative Example 2 was set to 100%, and the ratio (percentage) of the standard deviation obtained in Example 2 to the standard deviation in Comparative Example 2 was calculated. By the way, it was 88%. Therefore, with regard to the steel material Y, it was found that the variation was improved by 12% by correcting the reference furnace temperature (reference furnace temperature straight line Ls) as described above.

The steel temperature prediction method can accurately predict the temperature of the steel in the heating furnace, and thus can be suitably applied to the manufacture of various steels involving heating processes.

1a, 1b upstream burners 1c, 1d downstream burner 7a upstream thermometer 7b downstream thermometer 10 conveying surface A steel material D conveying direction Ls reference furnace temperature straight line Lc1 between position N1 and position N2 Corrected furnace temperature straight line Lc2 Corrected furnace temperature straight line T1 between position N2 and position N5 Measured furnace temperature T2 at position N1 Measured furnace temperature K1 at position N6 Corrected furnace temperature K2 at position N2 Position Correction in-furnace temperature S1 in N5 Furnace temperature measurement step S2 Fuel flow rate measurement step S3 Correction in-furnace temperature calculation step S41 Reference furnace temperature calculation step (S4 furnace temperature prediction step)
S42 Corrected Furnace Temperature Calculation Step (S4 Furnace Temperature Prediction Step)
S5 heat flux calculation step S6 steel material temperature calculation step

Claims (1)

A method for estimating the temperature of steel material conveyed in a heating furnace, wherein the heating furnace comprises a first burner arranged upstream in the conveying direction of the steel material , and a first burner arranged downstream in the conveying direction of the steel material. Equipped with 2 burners ,
A temperature T1 in the heating furnace at a first position N1 on the upstream side of the first burner in the conveying direction, and a temperature T1 in the heating furnace at a second position N6 on the downstream side of the second burner in the conveying direction. measuring the temperature T2 ;
measuring the fuel flow rate F of the first burner and the second burner ;
Based on the measured furnace temperatures T1 and T2 at the first position N1 and the second position N6 and the measured fuel flow rate F of the first burner and the second burner , the first position N1 and the first burner a step of calculating correction furnace temperatures K1 and K2 at a third position N2 between and at a fourth position N5 between the second burner and the second position N6 ;
Based on the measured furnace temperatures T1 and T2 at the first position N1 and the second position N6 , and the correction furnace temperatures at the third position N2 and the fourth position N5 , a step of predicting the temperature inside the furnace at each position in the conveying direction;
calculating a heat flux at each position based on the predicted furnace temperature;
calculating the temperature of the steel material at each of the positions based on the calculated heat flux;
The correction furnace temperature calculation step includes:
A correction furnace temperature K1 at the third position N2 is calculated based on the following formula (1), and a correction furnace temperature K2 at the fourth position N5 is calculated based on the following formula (2). ,
The furnace temperature prediction process is
A straight line passing through the measured in-furnace temperature T1 at the first position N1 and the measured in-furnace temperature T2 at the second position N6 is defined as a set of the reference in-furnace temperatures at the respective positions. a step of calculating the temperature in the furnace;
calculating a corrected in-furnace temperature obtained by correcting the reference in-furnace temperature using the corrected in-furnace temperatures K1 and K2 at the third position N2 and the fourth position N5 .
K1=T1+(F-Fmin)×(K2-T1)/(Fmax-Fmin) (1)
K2={(T2-T1)/(D6-D1)}×(D5-D1)+T1 (2)
However, in the above formula (1), "Fmin" means the minimum value of the fuel flow rate F [Nm ³ /h], and "Fmax" means the maximum value of the fuel flow rate F [Nm ³ /h], In the above formula (2), "D1" is the distance from the position Ns of the first opening on the charging side of the steel material in the heating furnace to the first position N1, and "D5" is the distance from the position Ns to the above The distance 'D6' to the fourth position N5 means the distance from the position Ns to the second position N6.

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