JPH09308907A - Controlled cooling method and apparatus for thick steel plate - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To produce scale peeling unevenness in accordance with the distribution of the jet collision force of the descaling nozzle of the rolled material for controlled cooling
When controlled cooling is performed in the next step, cooling unevenness occurs depending on the distribution of scale peeling unevenness. Prevent this. SOLUTION: The flow rate of the header 2 in which the nozzle position coincides with the descaling nozzle position is increased by a flow rate adjusting valve 5, and after the controlled cooling, the temperature distribution in the width direction of the steel sheet is adjusted so as to be uniform, and the controlled cooling is performed. Allows uniform cooling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlled cooling of thick steel plate.

[0002]

2. Description of the Related Art A controlled cooling technique for cooling a thick steel sheet online immediately after hot rolling can give a required strength to the steel sheet in a smaller number of steps than before, and an additive alloy and carbon for obtaining the same strength. The equivalent weight can be reduced, and the weldability is greatly improved. Further, by combining with controlled rolling, it has become possible to manufacture a high-strength steel sheet excellent in low-temperature toughness and weldability, which was conventionally considered difficult.

Important techniques for establishing a controlled cooling technique are (1) practical use of a cooling device having a predetermined cooling capacity, and (2) a device and a cooling method for uniformly cooling a steel sheet. (1) Regarding a cooling device having a predetermined cooling capacity, various kinds of nozzles have been developed and put into practical use (for example, Japanese Patent Publication No. 52-85909 and Japanese Utility Model Publication 59-59).
No. 09072, Japanese Patent Publication No. 59-029054, etc.). (2) Regarding a device and a cooling method for uniformly cooling a steel plate, a masking device for preventing steel plate edge supercooling (Japanese Patent Laid-Open No. 60-166117, actual S61-12).
7812), end offset control for preventing front and rear end supercooling (Japanese Patent Publication No. 56-086622),
Various developments, proposals, and practical applications have been made such as a method of providing a water amount crown in the width direction according to the temperature distribution in the width direction of the steel sheet (Japanese Patent Laid-Open No. 61-19412), and uniform cooling is being achieved, but at a sufficient level. Is not reached.

[0004]

One of the major factors that hinder this uniform cooling is the scale distribution state of the front and back surfaces of the rolled material that is subjected to controlled cooling. The scale generated during rolling is removed by spraying high-pressure water onto the steel sheet using a descaling device provided before or after the mill or on one side. FIG. 5 shows an example of the plane shape of the spray pattern 22 of the descaling nozzle with respect to the plate width of the steel plate, and the collision pressure distribution 21 of the high-pressure water on the steel plate when spraying with this spray pattern 22. As shown in FIG. 5, it is difficult to make the collision pressure uniform even if the injection pattern is devised.
Scale peeling unevenness occurs depending on the distribution of the collision pressure. When the rolling is completed in such a state and the controlled cooling is performed in the next step, there is a distribution of scale peeling unevenness or scale thickness unevenness, so that cooling unevenness occurs even if cooling is performed uniformly by the cooling device.

It is an object of the present invention to solve the above problems and provide a controlled cooling method and apparatus capable of uniformly cooling the steel sheet in the width direction.

[0006]

In general, a steel sheet is more likely to cool as the scale is attached, and after control cooling, temperature unevenness occurs in the width direction of the steel sheet as shown by a temperature curve 23 in FIG. Further, due to the collision pressure distribution or flow rate distribution of the descaling jet water described above, a temperature distribution in the width direction occurs in the steel sheet during rolling, and if the control cooling is performed in such a state, the temperature distribution in the width direction will be maintained even after the control cooling. May occur.

Such temperature unevenness after controlled cooling may result in non-uniform strength of the product or residual stress. When the residual stress remains, it does not usually appear in the shape of the steel sheet, but when the steel sheet is cut and used, the residual stress is released and bending or the like occurs, which is a serious problem. In order to solve the above-mentioned problems, the present invention provides a controlled cooling method and device capable of uniform cooling in the width direction. That is, in the method of the present invention, in controlling and cooling a thick steel plate, the cooling water is injected to the steel plate position that matches the injection pattern of the descaling nozzle of the rolling mill, and the widthwise temperature unevenness of the steel plate caused by descaling is eliminated. A control cooling method for a thick steel plate is provided, which comprises controlling the injection flow rate of the cooling water as described above. According to this method, it is possible to perform cooling control according to width-direction scale unevenness caused by descaling during rolling or temperature unevenness, and width-direction non-uniformity in controlled cooling due to descaling during rolling. Cooling can be prevented.

An apparatus of the present invention capable of suitably carrying out the above-mentioned method of the present invention is a controlled cooling apparatus for thick steel plates.
A plurality of nozzle headers whose nozzle pitches and positions in the width direction match the pitches and positions of the descaling nozzles of the rolling mill were installed in the steel plate transport direction, and a flow rate adjustment valve that independently controls the flow rate of these nozzle headers was provided. It is a controlled cooling device for thick steel plates characterized by the above. The controlled cooling device has a plurality of nozzle headers in the traveling direction of the thick steel plate. A part of this nozzle header is used as a plurality of nozzle headers that match the descaling nozzle pitch and position, and a flow rate adjusting valve that can independently control the flow rate of the headers of these nozzles is provided to control the flow rate. That is, it becomes possible to perform cooling control according to width-direction scale unevenness or temperature unevenness caused by descaling during rolling.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a side view showing the configuration of the embodiment,
FIG. 2 is a front view showing the nozzle arrangement of the embodiment, in which the headers 1 and 2 appear to overlap each other in the front and back. The steel plate 11 is rolled by the rolling mill 9 and advances on the table roller 10. A descaling nozzle 8 is provided on the front surface of the rolling mill 9 to remove the scale. A control cooling device is provided downstream of the rolling mill 9. In the present invention, a nozzle header 2 is provided in addition to the conventional nozzle header 1. In FIG. 1, the cooling nozzle header 1,
2 are alternately arranged in the transport direction of the steel plate 11. As shown in the front view of FIG. 2, the nozzle header 2 of the present invention in which the pitch and position are aligned with the descaling nozzle is
The nozzle pitch and position are set so as to match the descaling pitch and position, and match with the position of high collision pressure in the descaling nozzle collision pressure distribution 21 of the steel plate 11. The conventional nozzle header 1 is arranged at an arbitrary position. The piping systems 3 and 4 of the nozzle headers 1 and 2 are independent of each other, and flow rate adjusting valves 5 and 6 are provided in the systems 3 and 4, respectively. The flow rate of the cooling water supplied from the pump 7 is controlled by the flow rate adjusting valves 5 and 6 independently of the normal nozzle header 1 in accordance with the scale thickness distribution or temperature distribution by descaling. Is possible.

According to the method of the present invention, the cooling water is sprayed to the position of the steel plate which coincides with the spray pattern of the descaling nozzle of the rolling mill, and the cooling water is sprayed so as to eliminate the temperature unevenness in the width direction of the steel plate due to the descaling. Control the flow rate. In this control, a plurality of nozzle headers whose nozzle pitch and position in the width direction match the pitch and position of the descaling nozzle of the rolling mill are installed in the steel plate transport direction, and the flow rate is adjusted to control the flow rate of these nozzle headers independently. It is realized by a controlled cooling device provided with a valve.

An embodiment of the present invention will be described with reference to FIGS. If scale unevenness occurs according to the descaling collision distribution after rolling, that is, if the scale thickness of the part with high collision pressure (immediately below the descaling) becomes thin, the scale thickness becomes thin in the controlled cooling in the next process. Therefore, it becomes difficult to cool, and after controlled cooling, the temperature rises only under the descaling. In order to prevent this, the flow rate of the header 2 where the nozzle position coincides with the descaling nozzle position is increased by the flow rate adjusting valve 5 and is adjusted so that the temperature distribution in the width direction becomes uniform after the controlled cooling.

As a result, uniform cooling by controlled cooling becomes possible. In the description of the embodiment, the nozzle header 2 matched with the descaling nozzle position as shown in FIG. 1 is arranged between the normal nozzle headers 1, but this arrangement is as shown in FIGS. 3 and 4, for example. , The header 2 may be arranged on the front surface or on the rear surface. Alternatively, any form may be used, such as arranging every few lines.

In the above description, the case where the invention is applied to the cooling device for the upper part of the steel sheet is described, but the same can be considered for the lower part of the steel sheet.

[0014]

According to the present invention, it has become possible to greatly reduce the unevenness in the widthwise cooling due to the descaling during rolling, which has been a problem in the past, due to the descaling during rolling.

[Brief description of drawings]

FIG. 1 is a side view showing a configuration of an example.

FIG. 2 is a front view showing the nozzle arrangement of the embodiment.

FIG. 3 is a side view showing the configuration of the embodiment.

FIG. 4 is a side view showing the configuration of the embodiment.

FIG. 5 is a diagram showing a descaling injection pattern in rolling.

FIG. 6 is a graph showing a steel plate temperature distribution after controlled cooling.

[Explanation of symbols]

1 Normal nozzle header 2 Nozzle header aligned with descaling nozzle position 3 Piping system of nozzle 1 4 Piping system of nozzle 2 5 Flow control valve of nozzle 2 6 Flow control valve of nozzle 1 7 Water supply pump 8 Descaling header 9 Rolling Machine 10 Table roller 11 Steel plate 21 Collision pressure distribution 22 Injection pattern 23 Temperature distribution curve

Claims (2)

[Claims] 1. In controlling and cooling a thick steel sheet, cooling water is jetted to a steel sheet position that coincides with a jetting pattern of a descaling nozzle of a rolling mill so as to eliminate temperature unevenness in the width direction of the steel sheet due to descaling. A method for controlling cooling of a thick steel plate, which comprises controlling an injection flow rate of the cooling water. 2. A controlled cooling device for a thick steel plate, wherein a plurality of nozzle headers whose nozzle pitch and position in the width direction match the pitch and position of a descaling nozzle of a rolling mill are installed in the steel plate conveying direction, and these nozzle headers are installed. A control cooling device for thick steel plates, which is provided with a flow rate adjusting valve for independently controlling the flow rate of the steel sheet.