JPS6036625A - Uniform cooling method of high-temperature steel plate - Google Patents

Abstract

PURPOSE:To produce a steel plate having excellent mechanical properties and weldability without variance by measuring the temp. distribution of the high- temp. steel plate right after hot rolling and eliminating the uneven temp. in the steel plate by partial cooling in accordance with the measured temp. distribution then cooling the steel plate with water to a specific temp. CONSTITUTION:The temp. distribution on the front and rear surfaces of a steel plate 3 of 700-900 deg.C right after hot rolling is measured by using scanning type radiation thermometers 10, 11 while the plate 3 is conveyed by conveying rollers 2. The measured value thereof is inputted to a control device 30, by which the value is processed. The partially high-temp. part of the plate 3 is cooled by a cooler 2 having many cooling water nozzles so that the entire part of the steel plate 3 is cooled to have the uniform temp. distribution. The plate 3 cooled to the same temp. over the entire part is fed further to temp. measuring devices 12, 13 where the cooling effect by the cooler 20 is monitored and further the information thereon is fed to a control cooler 4 to cool the plate 3 with water to 300-500 deg.C. The entire part of the plate 3 is uniformly cooled and the steel plate having excellent mechanical properties, weldability, etc. and having no variance in quality is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for cooling a high-temperature steel plate, and more particularly to a uniform cooling method for continuously cooling a hot steel plate directly on a rolling line immediately after rolling.

In recent years, steel plates immediately after rolling have been cooled to 800℃ at a cooling rate according to the plate thickness.
A new heat treatment method has been developed that uses water cooling to 600°C to improve mechanical properties and weldability, and is bringing about a major revolution in the manufacturing process of high-grade tempered steel sheets. According to this, immediately after rolling.

Since the steel plate is at a high temperature of 700° to 900°C, □
There is no need for reheating as in conventional heat treatment methods (labor and energy savings can be achieved), and it is also possible to reduce alloy components due to improved material properties through effective use of processing heat treatment effects.

As described above, the method of directly water-cooling high-temperature steel sheets after IK rolling is extremely effective in improving material quality and reducing manufacturing costs, but it has extremely serious problems in terms of material variation and cooling distortion caused by uneven cooling. There is. In other words, because the steel plate after rolling does not exhibit a uniform temperature distribution over the entire plate thickness, the partially existing low-temperature areas cause supercooling during water cooling, resulting in uneven cooling and cooling distortion. cause This partial temperature drop observed in the steel plate after rolling may be caused by the desguring water injection during rolling or by the transfer roller 12.
This is thought to be due to heat transfer to -, and in fact, a temperature decrease of 10° to 60°C compared to the average temperature of the plate is generally observed.

Therefore, in order to uniformly cool the steel plate over the entire plate thickness and to prevent cooling distortion, a cooling system is required.

The first priority is to maintain uniform cooling performance of the equipment.
It goes without saying that the temperature distribution of the steel plate to be cooled is also extremely important. However, in conventional controlled cooling methods, studies have been conducted to prevent cooling distortion and cooling unevenness by focusing only on ensuring uniform cooling performance of the controlled cooling device, and it has not been possible to achieve complete uniform cooling and prevention of cooling distortion. Ta.

In view of this problem, the present invention focuses on the temperature distribution of the plate thickness before controlled cooling of the steel plate to be cooled, and by making this a uniform temperature distribution over the entire plate thickness.

This paper provides a method for uniformizing the temperature distribution of a steel plate immediately after rolling, with the aim of achieving uniform cooling and prevention of cooling distortion in a subsequent control cooling device. On the other hand, controlled cooling is applied continuously over the entire length of the steel plate.

When cooling, prior to the controlled cooling, first, the plate wall temperature distribution of the steel plate is measured in advance, and based on this, partial high temperature parts of the steel plate are cooled with water to reduce plate wall temperature unevenness of the steel plate. and then performing the controlled cooling to perform a uniform cooling process.

It is characterized by a uniform cooling method for high-temperature steel sheets. 1 The details of the present invention will be explained below according to an illustrated embodiment.

FIG. 1 shows the configuration of an example of an apparatus for carrying out the method of the present invention in a rolling line, in which 1 is a rolling machine, 2 is a conveying roller,
8 is a steel plate to be cooled after rolling, 4 is a control cooling device, 10 to 1
B indicates a steel plate temperature detector, and zO indicates a cooling device. The steel plate 8 to be cooled after being rolled by the rolling mill 1 is moved in the direction of the arrow in the figure by the conveyance roller 2, and the temperatures of the front and back surfaces of the steel plate are continuously measured by temperature detectors 10 and 11. A scanning radiation temperature sensor is used as the temperature detector 10.11, and as the steel plate 8 moves, the temperature distribution over the entire plate thickness is measured. The detection signal of the temperature detector 10.11 is transmitted as an electric signal to the control device f80, and this signal is processed by the control device 80 to select a desired nozzle in the cooling device 20, and at the same time control the amount of water to be ejected and the time of ejection. Determine.

The nozzle arrangement in the cooling device 20 in this embodiment is
As shown in FIG. As shown in the same figure (b), a cooling water supply pipe 4B incorporating a flow control valve 41 that can independently control the amount of water to be injected and a water control valve 4g that opens and closes the yarn path is connected to these pipes. The valves 41, 42 are automatically operated by the controller [800 command.

A control cooling device 4 similar to the conventional one is installed in front of the cooling device 20, and continuous pressure control cooling is performed over the entire length of the steel plate 8. Note that the illustrated temperature detectors 1...la, 1B are the temperature detectors 10. Although it has the same configuration as Ll, it is used for monitoring the cooling effect of the cooling device 20 or providing necessary information within the control cooling device.

Next, an example of a specific method of implementing the present invention using the above-mentioned apparatus will be described.

For ease of understanding, it is assumed that the temperature distribution measurement result of the steel plate 8 to be cooled by the temperature detector 10°11 is the temperature distribution shown in FIG.
0 The temperature distribution on the front and back surfaces is the same.

Also, the time it takes for the tip of the steel plate 8 to be cooled to enter the cooling device 20 is t. The threading speed of the steel plate 8 at this time is v(VI3
o. ).

Temperature detector 10. Measurement 1~ of the plate wall temperature distribution of the steel plate 8 using IIK, and the results of processing this with the controller 80.

Based on this, first, when the steel plate 8 moves through the cooling device 20 at a speed of V by X□(m), a predetermined flow rate of cooling water is ejected from the nozzle numbered 5~/1610 in the A row. Furthermore, the steel plate B is
□ At the advanced point, a predetermined flow rate of cooling water is ejected from the nozzles /165 to 410 in the B row. With this.

The 80,840°C portion of the copper plate is cooled. Next, when the tip of the steel plate 8 has advanced by K (Xs + ex + es) from the a position of the cooling device 20 (position fl at the time of to), the temperature reaches 0.
A predetermined amount of cooling water is spouted from the nozzle in row A6.47, and the steel plate 8 is (xa Xs ) from this position.

At the point where it has advanced, the cooling water jetting from the 46.7 nozzle in the 0th row stops. As a result, cooling of the 80860°C portion of the steel plate is completed, but cooling of the 840°C portion is continued. Furthermore, when the tip of the steel plate 8 has advanced by x4 from position a, the All nozzles in row A start spouting cooling water at a predetermined amount of -1°, and from this point the steel plate 18 advances by (x5 - x,). At this point, stop jetting cooling water from all nozzles in row A. As a result, the cooling of the steel plate 808 Z O'C portion is completed, and the cooling of the 840° C. portion by the A-row nozzles is also completed. Furthermore, cooling water jetting from all nozzles in row B is stopped at a position σ□ advanced from this point. This completes the cooling of the 80,840° C. portion of the steel plate by the B row nozzles. In this way, the steel plate 8 to be cooled that has passed through the cooling device 20 is partially cooled, and the temperature distribution of the plate becomes uniform.

The cooling water ejection timing of each nozzle in FIG. 8(A) during the above cooling process is illustrated over time in FIG. 8(B). In addition, in the figure, each small circle is divided into eight equal parts, and each head represents each nozzle row A, B, and C as shown in the figure, and the shaded part within one circle is A.
Indicates that the corresponding nozzle in the row is spouting cooling water,
Similarly, the dots in the circle indicate that the corresponding nozzles in the B row are spraying cooling water, and the black parts indicate that the corresponding nozzles in the 0 row are spraying cooling water. However, the white part inside the circle is where cooling water is spouted.

It shows that there is no. From the figure, each high temperature part (860° C., 840° C., 820° G) of the steel plate 8 is cooled by the cooling water jet from the nozzle of the corresponding nozzle row, matching the steel plate advancing time (the situation can be clearly seen).

Note that the amount of water ejected from each nozzle depends on the thickness of the steel plate 8 to be cooled,
It varies depending on the inlet temperature, material, threading speed, etc., and by inputting this information into the advance control device 80, the appropriate amount of water is automatically determined. Also, selection of nozzle number, ie, 1. .

The cooling portion is determined by converting the signals from the temperature detectors 10 and 11 into X-Y coordinates on a two-dimensional plane in the control device 80, and determining the cooling portion in the width direction of the steel plate, as shown in FIG. 8(a). (Y
Determine the nozzle number in the longitudinal direction of the steel plate (
The sheet passing speed and the corresponding injection time are determined based on the temperature distribution in the X direction).

The steel plate to be cooled, whose thickness distribution has been made uniform through the above operations, is transported to the next process, the control cooling device 4, where it is cooled in the same manner as in the past, and is uniformly cooled without uneven cooling or cooling distortion. Exhibits a temperature distribution.

The nozzle 1 used in the apparatus for carrying out the present invention may be a spray nozzle, a jet nozzle, a laminar flow nozzle, or the like, but suitable cooling methods such as proper cooling by cooling water retention on the upper surface of the steel plate, non-uniform cooling, etc. When considering water and air at the same time, K.

It is desirable to use a two-fluid nozzle that provides jet cooling.

In addition, in this embodiment, thermometers are installed on the 200 Å side of the cooling device to measure the temperature of the front and back surfaces of the steel plate separately, and the nozzles are also pressurized so as to spray cooling water one by one, facing the front and back surfaces of the steel plate. It is also possible to measure the temperature of one of the surfaces and cool either the front or back surface to make the temperature distribution of the steel plate 8 uniform.

As is clear from the detailed explanation above, even if uniform cooling was performed in the control cooling device 4 in the past, the temperature distribution of the steel plate 8 to be cooled was not uniform, resulting in uneven cooling and cooling. However, according to the present invention, the temperature distribution within the steel plate 80 before entering the control cooling system is completely uniform, which has caused distortion, which has been a big problem.

Therefore, uniform cooling treatment can be performed without uneven cooling or accompanying cooling distortion, which greatly contributes to the production of high-grade tempered steel sheets in particular.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram schematically showing an example of a device used to carry out the present invention, FIG. 2 is a chronological diagram showing the arrangement of the cooling device shown in FIG. 1, and FIG. 8 (A) is a plan view. Figure, (b) is A- of (b)
FIG. 8 is a diagram illustrating a situation in which a steel plate to be cooled is cooled based on an embodiment of the present invention, and FIG. The relationship between the steel plate and the nozzle array of the cooling device is shown, and (b) shows the cooling water spout timing of each nozzle. l...Rolling mill 2...Transport roller 8...Steel plate to be cooled Sheet...Control cooling device 10-18
...Temperature detector zO...Cooling device 80...Control device 40...2 fluid nozzle 41...Ryuyari control valve
42...Water use valve 4B...Cooling water supply pipe 44...
・Air supply piping.・Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] L When performing controlled cooling over the entire length of a high-temperature steel plate to continuously cool it, prior to the controlled cooling,
First, the plate wall temperature distribution of the steel plate is measured in advance, and based on this, the uneven temperature of the plate wall of the steel plate is eliminated by water-cooling the partially high-temperature parts of the steel plate, and then the controlled cooling is performed. A method for uniformly cooling high-temperature steel sheets characterized by: 1. uniform cooling treatment;