JPS611420A - Forced cooling method of hot-rolled thick steel plate and its device - Google Patents

Abstract

PURPOSE:To improve the quality of a thick steel plate by executing a temperature correction to an uneven high temperature part by forced auxiliary cooling, with respect to a temperature of the thick steel plate whose heat treatment has been ended, and thereafter, applying it to a straightening machine at least once. CONSTITUTION:A forced auxiliary cooling device 13 is provided at a distance in the rear part of a forced cooling device 4. The cooling device 13 is constituted of header mechanisms 14, 15 of the upper and lower parts, and cooling water is controlled and supplied to the upper and lower faces of a thick steel plate 7, respectively. The thick steel plate 7 which has passed through the cooling device 4 generates an uneven temperature at times. A temperature distribution of the steel plate 7 is measured by a temperature sensing meter 26, and based on this information, a control part 28 executes water quantity control to the part where a temperature is uneven, by giving a command to each valve of the header mechanisms 14, 15 of the upper part and the lower part of the cooling device 13. The steel plate 7 whose temperature has been corrected is applied to a roll straightening machine 30 and straightened. According to this method, the thick steel plate 7 of good quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a forced cooling method and apparatus for hot rolled thick steel plates.

(Prior Art) It is well known that a spray nozzle is attached to the front surface of a straightening machine in equipment for manufacturing thick steel plates.

However, the purpose of this spray device is to remove secondary scale that occurs on the surface of the steel sheet after hot rolling and before reaching the straightening machine.

By the way, the present applicant has proposed a technique for manufacturing a high-strength, high-strength steel plate by water-cooling the steel plate after controlled rolling, and this technique is attracting attention in the industry.

This proposed technology is an accelerated cooling facility, and a forced cooling device is installed between the finishing rolling mill and the straightening machine. This is achieved by online heat treatment technology that utilizes the high toughness improvement effect of controlled rolling and the strength increase effect of accelerated cooling.When manufacturing steel sheets with the same strength level, the carbon equivalent is lower than that of conventional steel or special control steel. Not only can it be reduced compared to rolled materials, but it is also extremely useful for improving weld cracking resistance and HAZ toughness (Kobe Steel Technical Report No. 3, published on October 1, 1983).
3@・See publication No. 4・Conventional example 1).

In addition, as disclosed in Japanese Patent Publication No. 51-20003, a first forced cooling device, a straightening device, and a second forced cooling device are sequentially installed in a straight line in the finished rolling material transfer path at the rear of the finishing rolling mill. There is a cooling adjustment device array for hot-rolled thick steel plates, which is characterized in that it is connected in series with (Conventional Example 2).

Furthermore, in a forced water cooling system for a hot rolling runout table, there is a technology that actually measures the steel plate temperature after the runout table has been cooled using a temperature needle CT in front of the coiler, compares that value with a target value, and feeds it back to the subsequent steel plate. (
Published October 1962, Hitachi Review No. 49 @ No. 10 No. 9
See pages 96 to 909, below, Conventional Example 3).

Also, JP-A-56-168908, JP-A-58-
No. 90314 (hereinafter referred to as conventional example 4) provides a feedback control method that focuses on temperature non-uniformity in the width direction of the steel sheet.

(Problems to be Solved by the Invention) Conventional Example 1 has no problem as long as there is no uneven temperature distribution in the steel plate after forced water cooling, but during mass production, uneven cooling may occur due to some disturbance. In particular,
If uneven cooling occurs in the width direction of a steel plate, even if the steel plate is temporarily flattened using a straightening machine, when the steel plate is cooled to room temperature, buckling due to thermal stress, that is, waves and warping will occur. In the next step, it is necessary to go through an undefined process such as cold straightening, which causes a problem of high cost.

Furthermore, even if the shape of the steel plate is good in appearance, horizontal bending may occur if strip cutting or other cutting is performed on a steel plate that has uneven temperature within the steel plate after warm straightening that exceeds the allowable value. Sometimes. The relationship between the temperature nonuniformity in the width direction, T, and the amount of lateral bending S is approximated by, for example, equation (1).

AT/B=+8・S/α・L 2− (11 where B: strip width, α: linear expansion coefficient, L: copper plate length.

Here, in Conventional Example 1, temperature non-uniformity occurs because
There may be a problem with the forced cooling system (this means that it is caused by a defective shape of the steel plate, uneven temperature at the entrance of the steel plate, etc.).

Furthermore, in Conventional Example 2, the first and second
However, this cooling system does not take into account the deformation of the steel plate after online heat treatment, and after the second forced cooling system, the temperature at the entrance side of the copper plate, which is caused by non-uniformity etc. as in Conventional Example 1, is Non-uniformity occurs and cutting causes the problems described above.

Furthermore, in conventional examples 3 and 4, CT
is set as a target value (an online heat treatment function), and does not attempt to correct the position of the defect after detecting the defect using CT.Therefore, there is a problem similar to that described above.

(Means for solving the problem) The present invention cools a thick steel plate after hot rolling with forced water, and then corrects or corrects non-uniformity of the temperature of the thick steel plate before or during straightening. It is therefore an object of the present invention to provide a method and apparatus for manufacturing high-strength steel plates for shipbuilding, marine structures, tanks, etc., by solving the problems of the conventional examples described above. First, after a thick steel plate has been hot rolled or hot straightened, online heat treatment is completed by forced water cooling, and then the hot rolled thick steel plate is forced to be straightened by applying it to a straightening machine online. In the cooling method, the temperature of the thick steel plate after online heat treatment by forced water cooling is corrected by performing forced auxiliary cooling on-line for uneven high-temperature parts, and then being corrected by applying a straightening machine at least once. This invention relates to a forced cooling method for hot-rolled thick steel plates, which is characterized by the following:
In a forced cooling device for hot rolled thick steel plates, which is equipped with a forced water cooling device for on-line heat treatment and a straightening machine on a hot rolling line for thick steel plates, there is a forced cooling device for hot rolled thick steel plates downstream of the forced water cooling device. This invention relates to a forced cooling device for hot-rolled thick steel plates, characterized in that another forced auxiliary cooling device for correcting steel plate temperature imbalance and a straightening machine are arranged in the longitudinal direction of the line.

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

1 and 2 illustrate the equipment according to the first embodiment of the present invention, in which a line 2 of a finishing mill 1 shown in the form of a roll of hot thick steel plate is arranged in rows at intervals in the longitudinal direction of the line. In this embodiment, a roller table with rollers 3 is provided.

An online accelerated cooling device, that is, a forced cooling device 4 for online heat treatment, is provided on the line 2 downstream of the finishing mill 1.
It is composed of an upper header mechanism 5 provided above and a lower header mechanism 6 provided below the line 2.

In the upper header mechanism 5, spray nozzles 8 are arranged in parallel at intervals in the width direction of the thick steel plate 7, and each of the nozzles 8 can control the amount of cooling water including stopping with a valve 9. are arranged in rows in the longitudinal direction of the line, that is, in the threading direction, as shown in FIG.

In the lower header mechanism 6, spray nozzles 10 are arranged in parallel at intervals in the width direction of the thick steel plate 7, and each of the nozzles 10 can control the amount of cooling water including stopping with a valve 11. are arranged in a row between the rollers 3 as shown in FIG.

Cooling water can be supplied to each of the aforementioned nozzles 8°IO through a piping system (not shown) from a pump.

At the rear of the forced cooling device 4, a forced auxiliary cooling device 13 is installed at a distance from the device 4 in order to provide air cooling time in order to make the temperature distribution in the thickness direction of the copper plate quasi-steady after online heat treatment. The cooling device 13 corrects non-uniformity in temperature of the thick steel plate, and the cooling device 13 includes an upper header mechanism 14 and a lower header mechanism 15 having the same configuration as the upper and lower header mechanisms 5.6 of the forced cooling device 4 described above. It consists of
Cooling water can be supplied to the upper and lower surfaces of the thick steel plate 7 through online control.

That is, in the forced auxiliary cooling device 13, as shown in FIG. 2, an upper header mechanism 14 is constructed by arranging a group of spray nozzles 17 having valves 16 arranged in a row in the width direction of the thick steel plate 7 in the sheet passing direction. Further, the lower header 15 is constructed by arranging a group of spray nozzles 19 having valves 18 arranged in a row in the width direction of the thick steel plate 7 between the rollers 3 in the sheet passing direction.

Furthermore, in this embodiment, the frame 21 is attached to the upper header mechanism 1 for mounting the nozzle which can be raised and lowered by the cylinder mechanism 20.
A member 22 provided on the 4th side and installed horizontally on the frame 21
A grid-shaped cooling water guide plate 23 is provided between each nozzle 17 at intervals in the width direction. In addition, since the guide plate 23 can be raised and lowered freely, it is kept raised and on standby during sheet passing, and does not become an obstacle. Further, by dividing the guide plate 23, cooling control can be made more accurate. Further, a grid-shaped cooling water guide plate 24 is also provided on the lower header mechanism 15 side. In addition, the above-mentioned information board 2
3.24 'It may not be necessary to provide this.

A piping member 25 is connected to each nozzle group 17 and nozzle group 19, and cooling water can be supplied from the pump P shown in FIG. 2, and the flow rate can be adjusted individually by each valve 16. It is said to be controlled.

Furthermore, a thermometer 2 made of a thick steel plate 7 is installed on the outlet side of the forced cooling device 4.
6 is provided, the temperature distribution of the steel plate is detected by the thermometer 26, and the information is inputted to the control unit 28 by the information command means 27, and in response to this input, the non-uniform high temperature portion is controlled by the forced auxiliary cooling device 13. In order to perform forced auxiliary cooling and temperature correction online, a feedback means 29 feeds back information from the control section 28 to the aforementioned groups of valves 16 and 18 for controlling each nozzle.

In addition, a plurality of thermometers 26 may be installed in the direction of the board,
Alternatively, one may be installed. When one piece is installed, it has a function to move freely in the line width direction using a cylinder mechanism (not shown) in the board direction, or has a mechanism with an equivalent function, and can measure temperature in the width direction. It is necessary to.

Further, behind the forced auxiliary cooling device 13, as shown in FIG. 1, a straightening machine 30, exemplified in the form of a roll, is provided.

Note that an embodiment may be adopted in which the straightening machine 30 is provided at the rear of the forced cooling device 4, the forced auxiliary cooling device 13 is provided at the rear thereof, and the straightening machine 30 is provided again at the rear of this, depending on the case. In short, after forced water cooling for on-line heat treatment is completed, temperature correction is performed by performing forced auxiliary cooling on-line for uneven high-temperature areas in accordance with the temperature distribution of the thick steel plate.
This means that it is sufficient to use a straightening machine at least once for straightening after that. That is, when the straightening machine 30 is provided at the rear of the forced water cooling device 4 and the forced auxiliary cooling device 13 is installed at the rear thereof, an operating method is adopted in which the water is sent backwards after forced auxiliary cooling and is re-straightened by the straightening machine 30. It is also possible.

FIG. 3 shows a second embodiment of the present invention, and since the basic configuration is the same as the first embodiment, common parts are indicated by common symbols, and only the differences will be explained below.

In FIG. 3, a temperature meter 31 is also provided between the finishing rolling mill 1 and the forced cooling device 4, a temperature detection device or a predicted value W32 is linked to the temperature meter 26, and a steel plate position detection device 33 are provided.

Furthermore, a first steel plate position recognition device 34 and a temperature non-uniformity storage device 35 within the sheet surface are provided, and a second steel plate position recognition device 36 for forced auxiliary cooling is also provided, whereby the temperature non-uniformity portion as well as the non-uniform temperature portion are provided. Each piece of information regarding the position of the steel plate is feed-hacked to the control unit 28.

FIG. 4 shows a third embodiment of the present invention, and is an example in which a cooling body using mist is used as the forced auxiliary cooling device 13. The cooling body of the other 5 forced auxiliary cooling devices may be air or the like.

That is, in FIG. 4, the nozzle 1 of the upper header mechanism 14
7 is provided with a high-pressure air supply pipe 37 together with cooling water, and the pipe 37 is also connected to the nozzle 19 of the lower header mechanism 15, where the cooling water is made into a mist by high-pressure air and is sprayed onto each steel plate 7. It is possible to spray on the upper and lower surfaces of the

Other configurations are common to the first embodiment, and it goes without saying that the third embodiment can be applied to the second embodiment.

(Function) The hot thick steel plate is rolled by the finishing mill 1 and passed through the forced cooling device 4, where it undergoes online heat treatment to obtain mechanical properties such as high strength and high toughness through online accelerated cooling control. will receive.

By the way, while manufacturing a large number of products, temperature unevenness has already occurred in the steel plate machine on the forced water cooling system's four-man side due to external disturbances, such as skid marks in the heating furnace or local cooling during the rolling process. In some cases, it is not possible to avoid temperature non-uniformity in the steel plate after forced water cooling, such as when the steel plate is cooled by forced water cooling or when temperature non-uniformity occurs during forced water cooling due to the influence of the shape of the steel plate after rolling.

For example, as shown in FIG. However, in Figure 5,
indicates the longitudinal direction of the steel plate, Y indicates the steel plate width, and T indicates the temperature.

Even if a steel plate with more pronounced temperature non-uniformity is straightened by the straightening machine 30^ as shown in Fig. 7 (2) by water cooling after forced water cooling, the temperature of the steel plate 7A will drop to room temperature. Waves 7B are generated due to thermal stress, and at least an additional process such as cooling re-straightening is required in the next process.

In addition, there is no problem if the temperature is good as shown in Figure 7 (1), but if the temperature is uneven between Figures 7 (1) and (2), even if the copper plate is not straightened again as a large copper plate, the temperature will not be uniform. Uniform thermal stress exists within the steel plate 7^, so if the steel plate is cut into strips or the like when it is used, it will result in shape defects such as lateral bending after cutting.

However, in the present invention, the forced auxiliary cooling device 13 is provided in the downstream process of the forced water cooling device 4, and after correcting the temperature uneven portion of the steel plate 7, the correction [3
By multiplying by 0, the above problem is solved.

Here, the role of the straightening machine 30 is not only to improve the shape of the steel plate after rolling, but also to release the stress in the copper plate that has been created by the forced water cooling device 4 and the forced auxiliary cooling device 13. This means that after correcting the non-uniformity of the steel plate temperature in the forced auxiliary cooling device 13, correction necessary for stress release is performed at least once.

To explain the present invention in more detail, in the case of the first embodiment, the thermometer 26 measures the temperature distribution of the steel plate 7, and based on this information, information to be fed back is obtained, The control unit 28 controls each valve 16 of the upper header mechanism 14 of the forced auxiliary cooling device 13 in response to the temperature unevenness portion.
The amount of water (flow rate) from the nozzle 17 is controlled by issuing a command to activate the nozzle 17, and in the case of this embodiment, the lower header mechanism 15 is also controlled in the same way.

In the second embodiment shown in FIG. 3, the thermometer 26 also serves as a temperature detection device for controlling the forced auxiliary cooling device 13 and as a trigger for the steel plate position detection device.

The steel plate position recognition device 34 uses the trigger of the steel plate position detection device 33 as a reference, and in this example, receives, for example, the rotation pulse of the roller 3 of the roller table, and recognizes the steel plate position.

In addition, in the plate surface temperature non-uniformity storage device 35, the temperature of the temperature detection device 33 and the steel plate position (length/width) determined by the steel plate position recognition device 34 are stored in correspondence, and then, in this example, the steel plate position The controller 28 receives information from the steel plate position recognition device 36 that takes in signals from the detection device 33, rotation pulses of the roller 3, etc., and commands forced auxiliary cooling timing in consideration of the distance between the thermometer 26 and the forced auxiliary cooling device 13. It is sent to.

Here, when correcting the temperature non-uniformity of the steel plate, it is desirable to memorize the in-plane temperature of the steel plate after forced water cooling and correct the amount of deviation from the lowest temperature.

However, due to layout constraints, if the thermometer 26 is adjacent to the forced auxiliary cooling device 13, it may be necessary to correct the widthwise nonuniformity, which is important for thermal stress deformation of the steel plate, at each longitudinal position. It is possible.

In each of the embodiments described above, the amount of forced cooling at each correction position can be easily determined based on the forced cooling method, steel sheet dimensions, sheet threading speed, etc.

As auxiliary forced cooling methods, the air/water mist cooling method, forced air cooling, and spray method are effective for cooling the steel plate from the upper or lower surfaces, and when using a water column cooling method such as the pipe laminar cooling method, the lower surface cooling method is effective. is valid only.

This is because when applied to the upper surface of a steel plate, the auxiliary cooling water in the pipe laminar cooling method may flow out of the target position for non-uniformity correction, causing no adverse effect.

In addition, in FIG. 6 (11 (21), the steel plate size thickness 161, width 3200 m++, length 12
Temperature distribution after forced water cooling with 500 Dragon at a threading speed of 1.2 m/sec (Figure 6 (1)) and temperature distribution after this was corrected by forced auxiliary cooling device (Figure 6 ( 2)
) is shown.

Next, Figure 8 shows the shape defects of the steel plate and the temperature distribution on the entrance side of the steel plate (
Conventional example (No.
1) is compared with an example in which the present invention is applied to a copper plate where almost the same temperature non-uniformity has occurred (floors 2 to 7 in FIG. 8).

In FIG. 8, the cooling level, that is, the cooling level of the forced auxiliary device 13, refers to the cooling intensity level.
, medium is indicated by level 2, weak is indicated by level 3, and the temperature non-uniformity after forced water cooling is indicated by the level where the maximum temperature difference (difference between the highest temperature part and the lowest temperature part) is almost equal. There is.

That is, it can be seen that when there is a temperature difference of this level, an amount of lateral bending of around 30 mm/15 m as shown in the conventional example occurs, whereas in the present invention, the amount of lateral bending can be reduced.

As mentioned above, it is not necessary to apply the present invention to all copper plates after forced water cooling. For example, as an operational standard, temperature nonuniformity occurring after forced water cooling may be
There is also a method that is estimated from 1.1 and applied when the temperature is about 20°C or higher.

(Effects of the Invention) According to the present invention, after completion of forced water cooling for online heat treatment, temperature correction is performed by performing forced auxiliary cooling on-line on uneven high-temperature parts in accordance with the temperature distribution of the thick steel plate. After that, the steel plate is passed through a straightening machine at least once, so even if temperature unevenness occurs after forced cooling due to a defective steel plate shape, a high quality thick steel plate can be manufactured, and this steel plate can be cut into strips etc. No horizontal bending occurs even after processing.

In achieving the above advantages, the present invention also provides a thermometer,
Since it is sufficient to provide a control unit and an auxiliary forced cooling device on the equipment line, the equipment cost is not too high to mass-produce the above-mentioned high-quality products, and implementation is easy.

[Brief explanation of drawings]

Fig. 1 is a schematic side view of the entire equipment showing the first embodiment of the present invention, Fig. 2 is a detailed front view of the auxiliary forced cooling device in Fig. 1, and Fig. 3 is a schematic side view of the entire equipment showing the first embodiment of the present invention. FIG. 4 is an explanatory view of the main parts showing the third embodiment of the present invention, FIG. 5 is an explanatory view showing an example of non-uniform steel plate temperature, and FIG. 6+11
(21 is an explanatory diagram showing before and after forced auxiliary cooling straightening in this plant, Fig. 7+11 (2) is an explanatory diagram showing the temperature distribution after forced water cooling and the shape of the steel plate in the subsequent process,
FIG. 8 is an experimental diagram showing a comparison between the conventional example and the present invention. 1.-Finishing rolling mill, 4-Forced water cooling device, 13-.Forced auxiliary cooling device, 26-Temperature meter, 28-Control unit, 30- Straightening machine.

Claims (1)

[Claims] 1. After hot rolling or hot straightening a thick steel plate, after completing online heat treatment by forced water cooling, forced straightening of the hot rolled thick steel plate by applying it to a straightening machine online. In the cooling method, the temperature of the thick steel plate after online heat treatment by forced water cooling is corrected by performing forced auxiliary cooling on-line for uneven high-temperature parts, and then using a straightening machine at least once to correct the temperature. A forced cooling method for hot-rolled thick steel plates, characterized by: 2. In a forced cooling device for hot rolled thick steel plates, which is equipped with a forced water cooling device for online heat treatment and a straightening machine on a hot rolling line for thick steel plates, downstream of the forced water cooling device, A forced cooling device for hot-rolled thick steel plates, characterized in that a straightening machine and another forced auxiliary cooling device for correcting temperature non-uniformity of the steel plate are arranged in the longitudinal direction of the line.