JPS6257709A - Controlling method for cooling of steel products - Google Patents

Abstract

PURPOSE:To eliminate the temp. difference of steel products after cooling and to produce the steel products having stable quality by calculating the difference between the actual temp. and target temp. of the steel products at a water spraying position and controlling a water spraying rate so that the temp. difference is made zero. CONSTITUTION:Intermediate thermometers 71, 72 are disposed near cooling zones 51, 52 and the surface temps. of the strip measured by these thermometers are inputted to a temp. error correcting circuit 8. The circuit 8 determines the recuperatiom temp. from the water spraying position up to the intermediate thermometers and calculates the actual surface temp. of the steel products at the water spraying position from such temp. The difference between said temp. and the target temp. is then determined and such a water spraying rate as to eliminate the difference is determined. The water spraying to the strip is controlled by a water spraying control circuit 9 in accordance with the water spraying rate determined in the above-mentioned manner. The temp. difference of the steel products after cooling is thus thoroughly eliminated and the production of the steel products having the stable quality is made possible.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a cooling control method for steel materials, and in particular to a method for controlling the winding temperature of a hot strip, and more particularly to a method for controlling the winding temperature of a hot strip, and more particularly, a non-temperature control method in which the cooling control is terminated near the transformation point. This invention relates to a method suitable for cooling control of steel materials.

[Conventional technology]

The method for determining the water injection pattern in steel material cooling control is based on the difference between the actual measured value of the winding thermometer and the target value. A method that performs temperature correction and eliminates the difference (see Japanese Patent Application Laid-Open No. 60-40609). A method for calculating the temperature distribution (see Japanese Unexamined Patent Publication No. 8886/1986) has been proposed so far.

[Problems to be solved by invention C] However, the former cooling control method does not take into account the reheating effect of the steel material from the time cooling water injection ends until the temperature is measured. If there is a disturbance caused by a change in speed, thickness, thickness, or even size, an error will occur between the measured surface temperature and the target temperature, and as a result, the end of water injection calculated based on this will occur. This will result in an error in the average temperature at that time. For this reason, the accuracy of cooling control is reduced, and the accuracy of temperature control of the steel material is also reduced. This means that
It has been difficult to accurately manufacture steel materials that meet the strict requirements for materials in recent years at high speeds.

Moreover, since the latter uses the temperature after completion of reheating, the temperature at the time of completion of rolling or the time of start or end of injection of cooling water is not the temperature to be controlled, making accurate control impossible.

[Means for solving problems]

In order to solve this problem, the present invention subtracts the recuperation temperature from the water injection end position of the cooling zone to the thermometer from the surface temperature of the steel material detected by a thermometer installed in the middle of the cooling zone. As a means of determining the actual side cross-sectional average temperature of the steel material at the water injection end position, comparing this actual side cross-sectional average temperature with the target cross-sectional average temperature to determine the error temperature, and performing water injection control to eliminate this error. There is.

[Effect]

Next, a method for determining a water injection pattern in the present invention will be explained using a hot strip production line as an example.

The apparatus used in this example is equipped with a control system as shown in FIG. In the figure, the roll rotation speed of the finishing rolling mill 1 is captured by the rotation speed detector 2.
For each predetermined length, the thickness and temperature of the corresponding portions are measured using a thickness gauge 3 and a thermometer 4, respectively. Then, the bath time for each cooling zone is determined from the planned speed pattern, and the water injection N (refers to the water injection amount per flowering time or the water injection time under a constant water amount.Hereinafter, this is (collectively referred to simply as water injection amount).

In the present invention, the relative error in the water injection amount determined in this manner is corrected as follows based on the difference between the target cross-sectional average temperature and the actual cross-sectional average temperature.

Upper cooling zone 53,5□ and lower cooling zone 61°6
Measure the surface temperature of the strip with intermediate thermometers 7□7□ installed on each exit side of □, and use this measured surface temperature to calculate the cross-sectional average temperature error ΔT of the strip defined by the following formula + 11. do.

ΔT, =ΔT, /(1-e −””) −−−
−−−−−−−−−−(11However, ΔT,・Lr T
@D ・・−・−・−−−−−−−−−−−m−・
・・・・・−・・・−(2) t=L/V ■Strip speed (m/5ec) T, 1: Actual surface temperature of strip (°C) Ts,:
Target surface temperature of strip 7 ('C) L: Distance from the water injection end position to the thermometer (m) C4: Recuperation time constant (sec) calculated in advance based on plate thickness, steel type, and temperature level Next, The correction amount of water injection amount is calculated by the following equation (4).

(α8-α,)Δt(Tll-T.

However, C9: Specific heat (Kcal/kg-'C) ρ: Specific gravity (
kg/m3) h: Plate thickness (m) No: Water injection amount per control zone α, ,: Heat transfer coefficient by water cooling (Kcal/m”hr ℃
) α, : Heat transfer coefficient by air cooling (Kcal/m”hr'c
) Δt: Control zone pass time (sec) T, strip average temperature at the entrance of the second control zone (°C) To: Water temperature ('C) Based on ΔT1 and ΔN obtained in this way, the desired target winding temperature can be determined. Since the relative error in the water injection amount is corrected to the temperature before reheating, the error in the starting point for winding temperature (cooling) control is eliminated, improving yield, and there are not many calculation steps, so equipment There is no increase in expenses and it is possible to avoid a rise in costs.

The present invention provides desirable effects not only in the above-mentioned hot strip manufacturing line but also in the manufacturing process of non-tempered steel sheets.

That is, when cooling is completed near the transformation point, cooling water injection can be uniformly and accurately completed just above the transformation point across the width of the steel sheet, or cooling water injection can be completed just below the transformation point. As a result, the flatness of the fil plate after cooling control is significantly improved, and a stable high yield is guaranteed.

〔Example〕

Next, the present invention will be specifically explained with reference to the embodiments shown in FIGS. 1 and 2.

In FIG. 1, the temperature error correction circuit 8 includes an intermediate thermometer 7
3.7! Input the actual value of the IJ tube surface temperature measured in step 5 of each cooling zone. (6,), 5. (6
ffi) and the recuperation temperature from the water injection end position to intermediate thermometer 3□, subtract it from the value determined in advance, calculate the cross-sectional average temperature at the water injection end position, and calculate the error from the target. Then, a correction calculation is made for the water injection amount corresponding to the error, and
Output to the water injection amount control circuit 9. In the water injection amount control circuit 9,
When the corresponding portion of the strip passes through the fine adjustment zone 10.11, water injection control is performed using the water injection amount correction portion.

FIG. 2 shows the results of cooling with the water injection amount controlled in this manner. As is clear from FIG. 2, in the present invention, even if a temperature error occurs at the water injection end position in an intermediate process, the winding temperature error is substantially reduced by subsequent correction control at the final water injection end position. The target will disappear. Therefore, the variation in material quality that was seen with conventional methods when building materials has been eliminated, and highly stable operability and operability have been achieved.

〔Effect of the invention〕

The present invention calculates the temperature at which the steel material recuperates from the water injection end position in the cooling zone to the thermometer, and subtracts this to calculate the cross-sectional average temperature error due to the difference between the target surface temperature and actual surface temperature of the steel material at the water injection position. Since the amount of water to be injected is determined so as to eliminate this error, the cooling temperature error is substantially eliminated.

As a result, many advantages are brought about, such as being able to stably manufacture steel materials of stable quality with high productivity.

[Brief explanation of the drawing]

FIG. 1 is a control system diagram used in an embodiment of the present invention, and FIG. 2 is a diagram showing a temperature control state in an embodiment of the present invention. Patent applicant: Nippon Steel Corporation Agent: Masu Tegori (and 2 others) Fig. 1 1 Finish rolling II 2: [ii1 Rotation speed detector 3
・Plate thickness gauge 4. Thermometer 42° width thermometer 51.
52,53,61.62,63: Cooling Zonin 71.
72: Core temperature trace meter 8/Temperature error correction circuit 9: Water injection amount control circuit 10, I+/Fine adjustment zone 12: Water injection pattern determination circuit 15/Learning circuit S Strip Figure 2 &! (ml

Claims (1)

[Claims] 1. The actual side cross section of the steel material at the water injection end position is obtained by subtracting the recuperation temperature from the water injection end position of the cooling zone to the thermometer from the surface temperature of the steel material detected by a thermometer installed in the middle of the cooling zone. 1. A cooling control method for steel materials, which comprises: determining an average temperature, comparing this real-side cross-sectional average temperature with a target cross-sectional average temperature to determine an error temperature, and performing water injection control to eliminate this error.