JPH0480975B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for estimating the forced cooling stop temperature of a material to be cooled when a hot rolled material is water-cooled in a hot rolling process in the steel industry, for example. It is something.

(Prior Art) In hot rolling processes and the like, high-temperature materials to be cooled are cooled with water for the purpose of material quality control, etc. In this case, it is important to control the cooling stop temperature in order to maintain the quality of the finished product.

For example, in conventional hot strip mills, water cooling is performed on a run-out table, and in order to control the cooling stop temperature mentioned above, a thermometer is installed in the middle or on the outlet side of the cooling device, and the material to be cooled is The temperature of a certain steel plate was being measured (Tokuko Sho)
53-25701). This hot strip mill produces thin plates, and since the temperature in the thickness direction after water cooling is averaged, that is, double heat is extremely fast, the surface temperature is taken as the representative temperature of the steel plate. There was no problem even if the cooling stop temperature was found to be higher.

However, in recent years, with advances in cooling technology, forced water cooling has come to be applied to plate factories and steel bar factories. When determining the average cross-sectional temperature, etc.) by online measurement,
Due to various disturbances (including differences in operating conditions),
This has to be done after a sufficient air cooling time has elapsed, and it takes time to determine the cooling stop temperature, which causes problems such as a decrease in productivity.

In general, when the material is the same, the temperature recovery of a water-cooled material is faster as the water density is lower or the material is thinner. But for example thickness 10mm
When a steel plate is cooled with water at a water density of 1 m ³ /min・m ² and the average temperature in the thickness direction is increased from approximately 800°C to 550°C,
After cooling, it takes about 150 seconds for the compound heat to build up in the thickness direction.
That is, in order to estimate the cooling stop temperature, it is necessary to wait 150 seconds after the cooling stops.

(Object of the Invention) The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to prevent the material from being cooled after forced cooling, not only after the material to be cooled undergoes multiple heating, but also without waiting for the completion of the multiple heating after cooling. An object of the present invention is to provide a method for estimating the forced cooling stop temperature of a cooled material, which makes it possible to determine the cooling stop temperature of the cooled material.

(Structure of the Invention) In order to achieve the above object, the present invention provides an air cooling time after forcibly cooling a high-temperature material to be cooled, measures the surface temperature of the material to be cooled, and measures the surface temperature of the material to be cooled when the forced cooling is stopped. In a method for estimating the forced cooling stop temperature of a material to be cooled, which calculates the representative temperature of a cross section perpendicular to the direction of transport of the material to be cooled, at least one representative point of the material to be cooled is determined.
The representative surface temperature T _AV is determined from the sample value obtained by measuring the surface temperature of the material to be cooled at least twice after a certain sample time at the representative point, and also indicates that the temperature at the representative point is rising. If the temperature is rising, _the difference between the surface temperature at the completion of compound heating and the above-mentioned representative surface temperature T _AV is determined for each two appropriate reference temperatures T _l (l = 1, 2). , the difference between the surface temperature at the completion of compound heating and the average temperature in the plate thickness direction at that point, ΔT _pl , and the temperature drop due to air cooling, ΔT _fpl , from the stop of forced cooling until the completion of compound heating, are expressed as the water density, the material to be cooled. The standard cooling stop temperature T _fTl is calculated by the following formula T _fTl = T _AV + DT _l + ΔT _pl + ΔT _fpl , and the target cooling stop temperature T _fp is calculated as appropriate.
The cooling stop temperature T _feo is calculated using the following formula T _feo = T _fT1 + (T _fT2 − T _fT1 )・(T′ _fe1 − T ₁ ) / (T ₂ − _{T 1} ) to improve calculation accuracy. If necessary, calculate the corrected cooling stop temperature T _feo+1 using the above cooling stop temperature T _feo using the following formula: T _feo+1 = T _fT1 + (T _fT2 − T _fT1 )・( T _feo - T ₁ ) / (T ₂ - _{T 1} ) T _feo+1 is newly set as T _feo , and this calculation is repeated an appropriate number of times to calculate the cooling stop temperature T _feo . If the temperature is not rising, the difference ΔT _nl between the representative surface temperature T _AV and the average temperature in the plate thickness direction at that temperature, and the forced cooling for each reference temperature T _l (l = 1, 2) The temperature drop ΔT _fnl due to air cooling after stopping until sampling is expressed as a function of the thickness of the material to be cooled and the air cooling time, and the reference cooling stop temperature T _fTl is calculated using the following formula: T _fA1 = T _AV + ΔT _nl + ΔT _fnl Then, the cooling stop temperature T _feo was calculated in the same manner as above.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows a thick plate finishing rolling equipment line to which the method according to the present invention is applied.
is arranged, and the steel plate 4 is passed along the pass line 5 from right to left in the figure. Furthermore, an inlet thermometer 6 and an outlet thermometer 7 are provided before and after the cooling equipment 2 in order to measure the surface temperature of the thick steel plate 4. In addition, as shown by the two-dot chain line in the figure, the cooling equipment 2 and the outlet thermometer 7 may be arranged in front of the hot leveler 3 in the sheet passing direction.

The cooling method using the cooling equipment 2 is a one-way cooling method in which the steel plate 4 is sequentially cooled from the front end toward the rear end in the transport direction while being transported. Incidentally, other cooling methods include cooling by oscillation passing, which cools the steel plate 4 while reciprocating, but the cooling method is not limited in any way to the application of the method according to the present invention described below.

In the above-mentioned equipment, after the steel plate 4 leaving the finishing mill 1 has been cooled in the cooling equipment 2, it is conveyed to the front of the hot leveler 3 and once stopped, and then the method according to the present invention is carried out. Then, the temperature of the steel plate 4 is measured using the outlet thermometer 7. That is,
Temperature sampling is performed at multiple times at the same location. After the measurement, the steel plate 4 is conveyed again, and the steel plate 4 is leveled by the hot leveler 3 to remove internal stress and distortion.

Next, the method for estimating the forced cooling stop temperature of a material to be cooled according to the present invention will be specifically explained by applying it to the above equipment.

First, it is known that the temperature change at any point where the above sampling was performed is as shown in FIG. The horizontal axis in the figure is the time from the start of water cooling, and t = τ〓 and τ〓 + Δτ _p indicate the time when water cooling is stopped and the time when reheating is completed after stopping water cooling, respectively.
The vertical axis is temperature, and the curve shows the change in the surface temperature of the steel plate 4 at the arbitrary point, and the curve shows the change in the representative temperature at this arbitrary point, that is, in this example, the average temperature in the thickness direction of the steel plate 4.

As shown in the figure, the state after water cooling is stopped consists of two regions. That is, the first state is the reheating process after stopping water cooling, and the time t=τ〓~τ〓
+Δτ _p , the second state is the process after completion of reheating,
Then, after time t=τ〓+Δτ _p .

In addition, as mentioned above, in the present invention, sampling is carried out at the same location at multiple points in time. Below, we will take an example of a case where the number of samplings is two (see Figure 2, each time before and after the completion of reheating). (The same symbol indicates the case where each measurement was made twice.), will be explained according to the flowchart shown in FIG.

After water cooling is stopped in the step, (τ _i , Ti) is sampled when the steel plate 4 is stopped. Here, τ _i : Time from the start of water cooling Ti: Surface temperature of the steel plate 4 at time t=τ _i i: 1,2.

In step, the amount of change Rt in the representative temperature over time and the representative surface temperature _TAV are calculated using the following equation.

Rt = (T ₂ - T ₁ ) / (τ ₂ - τ ₁ ) T _AV = (T ₂ + T ₁ ) / 2 Steps determine whether Rt is positive or negative, that is, the surface temperature of the steel plate 4 is rising at the time of sampling. If Rt > 0, the system is in the state of recuperation, and the process proceeds to step 2. If Rt is 0, the state is in the state after the completion of reheating, and the process proceeds to step 0.

In step ~, two appropriate reference temperatures Ti (i=1,
2) For example, set T ₁ = 300°C and T ₂ = 550°C, and for each reference temperature Ti, determine the surface temperature T _ps at the completion of reheating,
Difference from the representative surface temperature T _AV DT _l (=T _ps − T _AV ), difference ΔT _pl between the above surface temperature T _ps and the average temperature T _PA in the plate thickness direction
(=T _ps −T _PA ), time Δτ _l from water cooling stop to completion of reheating, and surface fall rate of steel plate 4 due to air cooling
Express V _cl as follows and calculate each value.

DT ₅₅₀ = 5.176×10 ^-3・ω ^0.02237・t ^1.845・Rt+(0055・t−2.60)・logω+0.072t−3.90 [℃] ω: Bottom water density (final bank) [m ³ /min・
m ² ] DT ₃₀₀ = 3.236×10・ω ^0.00942・t ^1.871・Rt＋0.012t−0.55 ΔT _p550 = 1.274×10 ^-1・t ^0.960 [℃] ΔT _p330 = 2.044×10 ^-2・t ^0.980 Δτ _p550 = 10 ^m1 m1=(-0.131・logt+0.288)・logω+
1.87・logt−1.55 Δτ _p300 =10 ^m2 m2=(−0.0736・logt+0.152)・logω+
1.83・logt−1.56 V _c550 = 5.929・t ^-0.8865 [℃/sec] V _c330 = 1.756・t ^-0.8295 steps, the temperature drop ΔT _fPl due to air cooling during the time Δτ _Pl after stopping water cooling is calculated by the following formula: ΔT _fPl Calculated using =V _cl・Δτ _pl [°C].

In step, the reference stop temperature T _fTl is calculated using the following formula.

T _f550 = T _AV + DT ₅₅₀ + ΔT _p550 + ΔT _fp550 T _f330 = T _AV + DT ₃₀₀ + ΔT _p300 + ΔT _fp300 Step, set the target cooling stop temperature T' _fp as appropriate, and calculate the cooling stop temperature T _feo by the following formula, T _feo = Calculated using T _f300 + (T _f550 − T _f300 ) ・(T′ _fp −300)/(550−300).

Furthermore, in order to improve the calculation accuracy, proceed to the step as necessary to replace the target cooling stop temperature T′ _fp with the cooling stop temperature T _feo in the formula in the above step to obtain the newly corrected cooling stop temperature T _{feo+ 1} and set it as the new cooling stop temperature T _feo . In other words, the corrected cooling stop temperature T _feo+1 is calculated by the following formula T _feo+1 = T _f300 + (T _f550 − T _f300 ) ・(T _feo −300)/(550−300), and T _feo Set ₊₁ as new T _feo .

In step, the cooling stop temperature T _feo obtained by the initial calculation in step or the cooling stop temperature T _feo obtained by repeating the loop of steps and steps an appropriate number of times is finally determined as the cooling stop temperature.

On the other hand, when Rt0, proceed to step ~,
In the same way as above, the surface temperature drop rate V _c is expressed, and
The difference ΔT _nl (= T _AV − T _nA ) between the representative surface temperature T _AV and the average temperature T _nA in the plate thickness direction and the temperature drop ΔT _fnl on the surface of the steel plate 4 due to air cooling are expressed as follows and the respective values are calculated. .

ΔT _n550 ≒ΔT _p550 =1.274×10 ^-1・t ^0.960 [℃] ΔT _n300 ≒ΔT _p300 =2.044×10 ^-2・t ^0.980 ΔT _fn550 =V _c550・Δτ _AV [℃] ΔT _fn300 =V _c300・Δτ _AV Δτ _AV = (τ ₁ + τ ₂ )/2−τ〓 [sec] However, Δτ _AV : representative air-cooling time, τ: water-cooling time. In step, calculate the reference stop temperature T _fT1 using the following formula.

T _f550 = T _AV + ΔT _n550 + ΔT _fn550 T _f300 = T _AV + ΔT _n300 + ΔT _fn300 In steps ~, determine the cooling stop temperature T _feo in the same manner as in steps ~ above.

Figure 4 shows an example of calculation performed according to the above procedure, where the horizontal axis is the initially assumed target cooling stop temperature T' _fp , and the vertical axis is the prediction error (=T _fei - T _fp , T _fp is the true value of the cooling stop temperature), and the case where the cooling stop temperature is calculated only once (n = 1) and the case where it is calculated three times using the above loop (n
=3).

In addition, A in the figure is t=50mm, ω=0.15m ³ /min・
When predicted from the temperature measurement after 5 seconds after cooling at ^m2 , B
shows the case where t=50mm, ω=1.0m ³ /min·m ² , and predicted from temperature measurement 20 seconds later.

As is clear from the figure, in both cases A and B, the prediction error increases when n = 1, depending on the assumed target cooling stop temperature, but when n = 3, it is not affected by the value of the target cooling stop temperature. It becomes an almost constant value. In other words, variations in calculation results due to the magnitude of the target cooling stop temperature are almost eliminated by repeating the calculation of the cooling stop temperature three times.

(Effects of the Invention) As is clear from the above explanation, according to the present invention, the state after forced cooling is divided into the recuperation process and the two after completion of reheating.
Even if the surface temperature of the material to be cooled is sampled in any of the two regions, the cooling stop temperature is calculated in accordance with the characteristics of each region. Therefore, the stop temperature of the cooled material can be determined not only after the cooled material has recovered heat after forced cooling, but also without waiting for the completion of recuperation after cooling, which can be used for product quality control and proper cooling. Therefore, feedback to the forced cooling means can be quickly provided, and productivity can be improved.

In addition, the standard cooling stop temperature is determined for each of the two standard temperatures, and the cooling stop temperature can be calculated using a calculation formula based on these values. There is no need to use a separate formula each time, and calculations can be simplified.

[Brief explanation of the drawing]

Figure 1 is a schematic equipment configuration diagram of the plate rolling equipment, Figure 2
The figure is a schematic diagram of the cooling line of a steel plate, Figure 3 is a flowchart according to the present invention, and Figure 4 is a diagram showing the results of calculations by applying the method according to the present invention to the schematic model shown in Figure 2. be. 2... Cooling equipment, 4... Steel plate, 7... Outlet side thermometer.

Claims (1)

[Claims] 1. After forcibly cooling a high-temperature material to be cooled, an air cooling period is provided, the surface temperature of the material to be cooled is measured, and a cross section perpendicular to the direction of transport of the material to be cooled when forced cooling is stopped is measured. In the method for estimating the forced cooling stop temperature of a material to be cooled, at least one representative point of the material to be cooled is set, and at that representative point, after a certain sampling time, the surface temperature of the material to be cooled is determined by at least 2 points. The representative surface temperature is calculated from the sample value obtained by measuring twice.
In addition to finding T _AV , it is determined whether the temperature at the representative point is rising, and if it is rising,
The difference between the surface temperature at the time of completion of reheating and the above representative surface temperature T _AV for each of two appropriate reference temperatures T _l (l = 1, 2)
DT _l , the difference between the surface temperature at the completion of reheating and the average temperature in the plate thickness direction at that point ΔT _pl , and the temperature drop due to air cooling between the forced cooling stop and the completion of reheating ΔT _fpl
is expressed as a function of water flow density, thickness of the material to be cooled, and representative temperature change, and the reference cooling stop temperature T' _fTl is calculated by the following formula: T _fTl = T _AV + DT _l + ΔT _pl + ΔT _fpl , and the target cooling stop temperature is calculated as appropriate. T′ _fp
The cooling stop temperature T _feo is calculated using the following formula T _feo = T _fT1 + (T _fT2 − T _fT1 )・(T′ _fel − T ₁ ) / (T ₂ − _{T 1} ) to improve calculation accuracy. If necessary, calculate the corrected cooling stop temperature T _feo+1 using the above cooling stop temperature T _feo using the following formula: T _feo+1 = T _fT1 + (T _fT2 − T _fT1 )・( T _feo - T ₁ ) / (T ₂ - _{T 1} ) T _feo+1 is newly set as T _feo , and this calculation is repeated an appropriate number of times to calculate the cooling stop temperature T _feo . If the temperature is not rising, the difference ΔT _nl between the representative surface temperature T _AV and the average temperature in the plate thickness direction at that temperature, and the forced cooling for each reference temperature T _l (l = 1, 2) The temperature drop ΔT _fnl due to air cooling after stopping until sampling is expressed as a function of the thickness of the material to be cooled and the air cooling time, and the standard cooling stop temperature T _fTl is calculated using the following formula: T _fAl = T _AV + ΔT _nl + ΔT _fnl A method for estimating a forced cooling stop temperature of a material to be cooled, characterized in that the cooling stop temperature T _feo is calculated in the same manner as described above.