JPS60221527A - Cooling method of steel plate - Google Patents

Abstract

PURPOSE:To prevent scattering of cooling water by averting the interference between the nozzles of an upper cooling header and the end edge of a shielding member and correcting automatically the position thereof when the interference arises. CONSTITUTION:The top surface of a high-temp. thick steel plate 21 made by hot rolling is cooled by the cooling water flow from the nozzles on the side above the steel plate and the bottom surface thereof is cooled by the cooling water flow from the side below the plate 21. The cooling water flow to the top surface at each end is blocked by the shielding member 26 to execute controlled cooling so that the temp. is uniformly distributed in the transverse direction of the plate 21 after cooling. However, the respective inside ends 26A of the member 26 may interfere with the cooling water flow from the upper nozzles at the transverse size B of the steel plate with respect to the draining rate X at the end of the steel plate. The set value of the position of the member 26 is thereupon corrected.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for cooling a hot rolled steel plate, and more specifically, the present invention relates to a method for cooling a hot rolled steel plate. Related to a method for online cooling of a hot-rolled steel plate (prior art) In a hot rolling line in which a high-temperature thick steel plate is finished hot-rolled and then cooled on-line and the material quality of the steel plate is controlled by online heat treatment, As shown in Figure 6, on the line,
Heating furnace 1, rough rolling mill 2, finishing rolling mill 3, cooling device 4
, a straightening machine 5 such as a photo leveler are arranged in the above order. Thermometers 6 and 7 measure the temperature of the steel plate immediately before and after the finishing rolling mill 3, and thermometers 8 and 9 measure the temperature of the steel plate immediately before and after the cooling device 4. The above-mentioned equipment has the advantage that it is possible to effectively utilize the heat retained in the steel plate after rolling, and to produce steel plates of excellent quality at a low cost.

In the cooling device 4, while conveying the hot-rolled high-temperature thick steel plate, its upper surface is cooled by a pipe laminated nozzle, a spray jet nozzle, etc. arranged above the steel plate, and
The lower surface is cooled by a flow of cooling water injected by a spray jet nozzle or the like.

By the way, in general, for thick steel plates after finish rolling,
The temperature distribution in the width direction is not uniform, with the temperature at both ends in the width direction being low (and the temperature at the center in the width direction being high).

Therefore, if the above-mentioned thick steel plate is forcedly cooled with water on-line using the cooling device 4 without any consideration,
Due to the edge effect and the complicated heat transfer mechanism of water cooling in high-temperature areas, the temperature difference between the widthwise ends and the center of the steel plate when cooling is stopped is further amplified, and the mechanical strength of the steel plate after cooling is There is a problem that there is a large difference in properties in the width direction, and a large cooling strain occurs, causing large deformation such as warping of the steel plate.

The above problem occurs when the steel plate is repeatedly cooled to control the rolling temperature, especially for CR materials, and when the temperature of the steel plate immediately after the finishing rolling mill 3, that is, the finishing temperature is low,
It had become noticeable.

Therefore, Utility Model Application Publication No. 57-185421, Utility Model Application Publication No. 58
In Publication No. 47311 and Japanese Patent Application Laid-open No. 58-32511, in order to make the temperature distribution in the width direction of the steel plate approximately equal after cooling is completed, a heat treatment is applied to the upper side of both ends of the steel plate in the width direction. A system has already been proposed in which shielding members for blocking the flow of cooling water are movable in the width direction of the steel plate.

By the way, as shown in Japanese Unexamined Patent Publication No. 58-32511, the shielding width of each end in the width direction of the steel plate by the shielding member is set by the width and thickness of the steel plate and the density of the amount of cooling water with respect to the upper surface of the steel plate. is customary.

In the hot rolling line, the cooling device 4 is placed immediately after the finishing rolling mill 3, and the material quality of the steel plate is controlled by online heat treatment called controlled cooling. The temperature of the steel plate at the immediately preceding position,
That is, it is most ideal to measure the cooling start temperature and then make the final setting.

Additionally, if the upper cooling nozzle and the edge of the shielding member are on a vertical plane, the cooling water flow may collide with the edge, causing the cooling water to scatter and flow toward the steel plate. The subsequent temperature distribution in the width direction of the steel plate becomes unusual.

(Problems to be Solved by the Invention) That is, as shown in FIG. Within the diameter of the nozzle 11,
In other words, if it is on a vertical plane, it will collide with 61i as shown in the figure.
As a result, the normal cooling distribution as shown in Figure 8a becomes an abnormal cooling distribution as shown in Figure 8, and waves are generated in the shape of the steel sheet immediately after cooling. There is also.

In addition, even if the steel plate Y is cooled with the temperature distribution R or RA after cooling and the shape is corrected by the straightening machine 5 after cooling, the temperature distribution in the width direction remains as shown in FIGS. Afterwards, the steel plate shape 1 does not become the normal shape 13 shown in Fig. 9a, but the steel plate shape 1 again shows waves due to thermal deformation as shown in Fig. 4.
It becomes 38.

(Means for solving the problem) The present invention prevents the cooling water flow from scattering by avoiding interference between the nozzle of the upper cooling header and the edge of the shielding member, and automatically correcting the interference when there is interference. Therefore, in the present invention, the upper surface of a hot-rolled high-temperature thick steel plate is treated with a cooling water flow from a large number of nozzles arranged above the steel plate, and the lower surface is treated with a cooling water flow from a lower side of the steel plate. At the same time, the cooling water flow to the upper surface of each end is blocked by shielding members movable in the width direction of the steel plate provided on the upper side of each end of the steel plate in the width direction of the steel plate. In a steel plate cooling method that achieves a temperature distribution of The present invention provides a method for cooling a steel sheet, which is characterized in that the steel sheet is cooled by cooling the steel sheet.

(Example) Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

1 to 4, reference numeral 20 denotes a cooling table, which in this example is a roller table, and is installed between a finishing rolling mill and a straightening machine, and is used to cool two hot-rolled steel plates.
It can be transported in the direction of arrow A in the figure.

Reference numeral 22 denotes an upper cooling header, which is arranged above the cooling table 20 in parallel in the steel plate conveying direction.The header 22 is equipped with an inverted U-shaped laminar flow nozzle 23 in this example. For example, based on a header in which the nozzle is placed in the center of the equipment width direction as shown in Figure 3,
A large number of them are arranged in a staggered manner, that is, they are relatively moved in the width direction.

A lower cooling header 24 is disposed between the roller tables, and can eject cooling water from a nozzle 25 of the header 24.

Reference numeral 26 denotes a pair of left and right shielding members, which are provided between the upper surface of the thick steel plate 21 on the cooling table 20 and the upper nozzle 23. It is said to be movable.

The thick steel plate 21 is cooled by such a cooling device, by cooling the upper surface of the hot-rolled high-temperature thick steel plate 21 with a cooling water flow from the nozzle 23 above the steel plate, and cooling the lower surface with a cooling water flow from the lower side of the steel plate. At the same time, the shielding members 26 block the flow of cooling water to each end and top surface, and after cooling, the steel plate is cooled in a controlled manner using an onoline so that the temperature distribution in the width direction of the steel plate becomes approximately uniform.

As shown in FIG. 2, depending on the steel plate width dimension B, each inner end 26A of the shielding member 26 receives cooling from the upper nozzle 23, as shown in FIG. Since it may interfere with the water flow, the movement amount setting of the shielding member is corrected to prevent this interference.

Now, Zo is the judgment value, B is the plate width, Xo is the draining initial setting value, thX is the correction value, βp is the minimum pitch in the nozzle width direction, d
Letting be the nozzle diameter and y be the thickness of the inner end portion 26A, it can be corrected as follows.

In the separately calculated Zo value, Zo −#p
≦d/2 or Zo-Ap≧np-(d/2'+y)≦Zo, the preset value of the movement amount One example is that a standard value is set from the water density, this standard value is corrected by a correction value set from the thickness of the steel plate, and this corrected value is used as the shielding width by the shielding member. d/2 < 20 -42p < jl! p-(d/2 +
The correction value, X, is determined so that y), and the movement amount set value of the shielding member is corrected. Here, [ ] is a Gauss symbol.

Furthermore, by satisfying -βp<, x<βp, the cooling water flow from the upper nozzle 23 is directed toward the shielding member 26.
This prevents interference with the edge portion 26A.

Furthermore, as another example, when the minimum nozzle pinch becomes small, the modified end edge 26A of the shielding member 26 may be corrected to be in the middle of the minimum nozzle pitch.

That is, if the integer value N is B-ml! p(N±1) When N is an even number, x-□ The movement setting value of the shielding member 26 is corrected as follows.

Such a method of correcting the shielding member position setting value X solves the problem.

Note that depending on how χ is defined, the expression may be different from the above formula, but the same effect can be obtained.

Next, that's all. -ffp< as the range of X. xkuffp
Fig. 5 shows the relationship between the shielding member setting amount X obtained from the results of steel plate thermal deformation analysis of the shielding member 26 and the critical temperature at which buckling of the steel plate occurs.

That is, in Fig. 5, ■ indicates the forced water cooling, ■ indicates the air cooling process after straightening, ■ is determined by the cooling stop temperature and water volume density, and ■ is determined by the cooling stop temperature, and in the figure, the temperature is 500°C. This shows when air cooling is being performed after water cooling has stopped.

As is clear from Fig. 5, in order to prevent the steel plate from deforming, the temperature difference must be T within the curve shown by ■ during forced water cooling, and the temperature difference H after straightening. ,
It must be within T.

That is, in the shaded area in FIG. 5, the shielding member position setting value X is set at a point where T is large, as shown by arrow A point.

Therefore, in the setting correction method described above, the correction amount t,
It is possible to take both positive and negative values, but as is clear from Fig. 5, in the x/B region smaller than 2x/B = 2χA / B at point A, T rapidly decreases, whereas 2χA In the x/B region, which is larger than /B. T is decreasing little by little.

This shows that when correcting x, it is advantageous to take X to be positive.

That is, in the above correction method, 0ku. It is desirable to set x to βp.

(Effects of the Invention) The present invention is as described above, and when cooling a hot-rolled thick steel plate from the upper and lower surfaces, a shielding member is provided at the upper part to uniformly cool the temperature distribution. Since collision between the member and the upper water flow can be avoided,
Approximately uniform forced water cooling can always be ensured over the entire board width direction.

[Brief explanation of drawings]

FIG. 1 is a front view of a cooling device used in the present invention - an example; FIG. 2 is a schematic plan view; FIG. 3 is a plan view showing the nozzle arrangement; FIG. 4 is an explanatory front view of a modified example; Fig. 5 is a graph showing the relationship with the critical buckling temperature difference, Fig. 6 is an overall view of a general cooling equipment, Fig. 7 is a front view of a conventional example, and Fig. 8 a-
b is an explanatory diagram comparing the temperature distribution of the present invention a and the conventional example, No. 9
Figures a and b are process explanatory diagrams showing the steel plate shapes of the present invention a and the conventional example. 22... Upper cooling water header, 23... Upper nozzle,
24... Lower cooling water header, 25... Nozzle, 26
...Shielding member, 26^...Inner edge of 26. Patent Applicant Kobe Steel, Ltd. Procedural Amendment (Import) 1 Indication of the case Showa 594V Patent Application No. 74778 2 Name of the invention Steel plate cooling method 3 Person making the amendment Relationship with the case Patent applicant (119) Kobe Co., Ltd. Steelworks/1 Agent Address: 1013 Mikuriya, Higashiosaka City, Osaka Prefecture WLu University V
i+0617821 (g 8j 'B oath 5 Date of notice of reasons for refusal Showa year, month, day (voluntary) 7. Contents of amendment +11 "zo・7p≧tp" on page 9, line 3 of the specification
-(d/2+y)≦zoJ t;hru't rZ
Correct as o-t'p≧zp-(cl/2+7)J. (3) In the first line of page 10 of the same book, it says “is.”
Correct this by saying, ``For example, [x] represents the largest integer that does not exceed x2.'' (4) Figure 5 of the drawing will be corrected as shown in the attached sheet.

Claims (1)

[Claims] 1. The upper surface of a hot-rolled high-temperature thick steel plate is cooled by a cooling water flow from a large number of nozzles arranged above the steel plate, and the lower surface thereof is cooled by a cooling water flow from below the steel plate. At the same time, the flow of cooling water to the upper surface of each end is blocked by a shielding member movably provided above each end of the steel plate in the width direction of the steel plate to achieve a desired temperature distribution in the width direction of the steel plate after cooling. In the steel plate cooling method, the steel plate is cooled by modifying the set value of the shielding member position so that the cooling water flow from the nozzle on the upper side of the steel plate and the inner edge of each shielding member do not interfere with each other. A steel plate cooling method characterized by: