JPH10272510A - Method for cooling joined part of sheet bar in hot rolling and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue good continuous rolling without separation in a joined part at the time of subsequent finish rolling by exactly cooling only the just near parts of the joined part between sheet bars in traveling. SOLUTION: This device is for cooling the joined part between the sheet bars before finish rolling and, by providing a nozzle 42 which is attached on a running truck 50 which is moved in synchronism with the speed of the sheet bars, truck driving device 52 and masking devices 60a, 60b, 62a, 62b on the upstream and downstream sides of a specified section, temp. is unformized without cooling the front and back away from the joined part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for cooling a sheet bar joint in hot rolling, and more particularly, to a method for cooling a sheet bar prior to hot finish rolling, which is suitable for use in joining billets. When the rear end of the bar and the front end of the succeeding sheet bar are heated and heated, pressed and butt-joined, only the sheet bar joint after joining can be cooled to achieve stable rolling. The present invention relates to a method and apparatus for cooling a sheet bar joint in hot rolling.

[0002]

2. Description of the Related Art Conventionally, in hot rolling of steel slabs, since the steel slabs extracted from a heating furnace have been rolled one by one, various troubles described below have occurred particularly in the finish rolling process. .

[0003] Poor biting at the tip of the slab Drawing of the trailing end of the slab Running trouble on the run-out table at the tip of the slab

[0004] In order to solve these problems, the rear end of the preceding slab and the front end of the following slab are sequentially joined on the entrance conveying line of the hot finish rolling mill and then subjected to finish rolling. A continuous rolling method to be provided has been proposed, and accordingly, various methods have been developed for joining billets.

[0005] Among them, an induction heating pressure welding method disclosed in Japanese Patent Application Laid-Open No. 60-24401 is known as a method capable of completing the bonding in a relatively short time. In this method, a solenoid type coil is used as a heating means, and a junction between a rear end portion of a preceding steel slab and a front end portion of a following steel slab is induction-heated, and then both ends are pressed, thereby leading and trailing. The two slabs are joined.

[0006]

However, in this method, the entire rear end surface of the preceding steel slab and the front end surface of the succeeding steel slab become a joint surface, and heating is performed over the entire joint surface. During the subsequent rolling, the joining temperature becomes high, the joining surface strength becomes weak, and the joining portion becomes thin during rolling,
There was a problem that a break occurred during rolling due to the tension between the rolling mills.

On the other hand, as related to the present invention, Japanese Patent Application Laid-Open No. 6-106203 proposed by one of the applicants discloses a method of cooling a pre-joined portion of a slab by cooling a pre-joined portion of the slab at the entrance of a finishing rolling facility. It is described that the gap between the billet phases generated at the time of pre-joining is closed at an initial stage of finish rolling, so that hot finish rolling can be stably performed under complete joining over the entire width direction of the sheet. I have.

However, in this method, since the cooling device is fixed, only the pre-joined portion cannot be properly cooled.

Japanese Patent Application Laid-Open No. Hei 6-262244, also proposed by one of the applicants, discloses that a descaling header that moves in synchronization with a billet is used to continuously remove the gap remaining between the billets. By injecting descaling water, the scale formation at the unjoined surface of the gap formed at the time of pre-joining of the slab is extremely small, and hot finish rolling is performed under joining over the entire width direction of the plate Is described to be performed stably.

In this method, it is necessary to synchronize the running speed of the descaling header and the billet joining surface. However, a valve for injecting the descaling water is provided with a running speed of the descaling header of the billet joining surface. If the valve is opened and closed after being synchronized with the traveling speed, the temperature accuracy is deteriorated due to the delay and instability of the valve opening / closing timing, the traveling distance is required to be long, and the cooling equipment becomes excessively large. On the other hand, if the fuel is injected before the running speed is synchronized, there is a problem in that the joint surface may be supercooled before and after.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to appropriately cool only the vicinity of the joint of the seat bar with relatively simple equipment.

[0012]

SUMMARY OF THE INVENTION According to the present invention, prior to hot finish rolling, the rear end of the preceding sheet bar and the front end of the succeeding sheet bar are butt-joined by heating, heating and pressing. Using a cooling unit and a masking unit that run in synchronization with the seat bar traveling speed for cooling the seat bar joint, during acceleration and deceleration when the traveling speed of the cooling unit is synchronized with the seat bar traveling speed. Has solved the above-mentioned problem by preventing the coolant from covering the sheet bar.

Further, a plurality of types of the cooling means are provided, and the type and the cooling time of the cooling means to be used are determined according to the thickness of the sheet bar, the traveling speed, and the temperature of the joint.

[0014] Further, in a cooling device for a sheet bar joint in the same hot rolling, there is provided a traveling carriage mounted with cooling means for cooling the sheet bar joint and traveling in synchronization with a sheet bar traveling speed. This problem is solved by providing a masking means for preventing the coolant from being applied to the seat bar during acceleration / deceleration when the traveling speed of the traveling vehicle is synchronized with the seat bar traveling speed.

[0015] The inventors of the present invention have conducted research and development on a joining method that enables simple, quick and reliable joining without wasting energy when joining billets. Part to several tens of mm between the part and the rear end
It is installed with a gap in between, and a process of applying and heating an alternating magnetic field penetrating in the thickness direction of the billet in this region, and combining a type of pressing at least one of the billets,
In particular, we found that it was effective.

According to this method, an eddy current is induced in the joining area by the alternating magnetic field, and the heat generated due to the eddy current causes the temperature of the joining surface of the steel slab to rise. It was possible to join the billets reliably.

By the way, in such an induction heating method,
The temperature is raised to the melting point of the scale formed on the surface of the steel slab to be joined or the melting point of the steel slab (solidus temperature) or higher. However,
In such heating and pressing joining, the joining portion becomes high temperature and the strength at the time of rolling is weak, so when performing normal rolling control, the thickness of the slab at the time of rolling becomes smaller than the thickness of the slab other than the joining portion. . For this reason, there is a problem in that the tension between the finish rolling machines per unit area is excessively large in the rear stage of the finishing rolling mill, and breakage occurs during the finishing rolling.

The present inventors have further studied to solve the above-mentioned problems, and as a result, by locally cooling the slab joint, the thinning at the time of rolling is prevented, and stable hot rolling is continued. I found what I could do. However, the joint is moving at the billet rolling speed, and if the joint is cooled before and after, the tension between the finish rolling mills increases, and the tension applied to the joint also increases. For this reason, it is desirable to cool only near the joint.

However, if the cooling device is fixed as in Japanese Patent Application Laid-Open No. 6-106203, which has already been proposed by one of the applicants, it is not possible to properly cool only the vicinity of the running joint.

Therefore, as one of the applicants has already proposed in Japanese Patent Application Laid-Open No. Hei 6-262244, cooling water is applied to a joint from a traveling carriage synchronized with a billet traveling speed from both upper and lower sides or one side. Can be considered. In such a method, it is necessary to synchronize the traveling speed of the traveling trolley and the billet joint.However, if cooling water is applied by operating the valve after the synchronization, the temperature accuracy is deteriorated due to delay and instability of the valve opening / closing time. In addition to this, there is a problem that the traveling distance of the traveling vehicle becomes longer and the cooling equipment becomes excessively large.

Therefore, in the present invention, during acceleration / deceleration when the traveling speed of the traveling vehicle is synchronized with the traveling speed of the sheet bar such as a billet, a coolant such as water is not applied to the sheet bar. Masking means is provided, coolant is ejected before the running speed is synchronized, and when the traveling vehicle accelerates / decelerates, by masking between the billet and the cooling means, the time delay of valve opening / closing time can be ignored, and joining It is possible to perform accurate cooling control without supercooling the front and rear portions.

[0022]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 schematically shows an entrance-side transfer line of a finishing mill into which the first embodiment of the present invention is incorporated.

In FIG. 1, reference numerals 10a and 10b denote preceding and following billets, respectively, and 12 a coil box for winding and storing a billet heated in a heating furnace (not shown); , 24 is a pinch roll for conveying the billet, 16 is a leveler for straightening the billet unwound from the coil box 12, and 18 is a cut of the front and rear end of the billet before joining. The cutting device 22 for shaping into a shape suitable for joining is, for example, a joining device for joining the rear end of the preceding steel slab 10a and the tip of the following steel slab 10b during running, and 26 is a booklet. The joint cooling device according to the invention, 28 is a descaler for removing scale, 3
0 is the first stand of the finishing mill. Although FIG. 1 illustrates an example in which the heating and joining processes are performed between runs in synchronization with the running of the steel slab as the joining device 22, the looper 25 indicated by a broken line in the drawing is used. It is also possible to perform the heating and joining process while the joining device is stopped.

Now, when the alternating magnetic field A is applied to the butting portion 10c of the preceding steel slab 10a and the following steel slab 10b by the joining system 22 by the transverse method shown in FIG. Such an eddy current B is induced, and the bonding surface is preferentially heated. In FIG.
Reference numeral 32 denotes an alternating magnetic field generating coil that penetrates in the thickness direction of the billet to generate an alternating magnetic field A. The alternating magnetic field generating coil 32 includes a pair of iron cores 3 installed vertically above and below the billet.
4a, 34b, a conductor 36 continuously wound around these iron cores 34a, 34b, and a power supply 38.

As shown in detail in FIG. 4, the joint cooling device 26 is provided with a plurality of nozzles 4 in the width direction of the billet perpendicular to the plane of the drawing.
2 provided with upper and lower nozzle headers 40a, 40b for applying water from above and below to the joints of the steel slabs for cooling, and a valve 44 for turning on / off the cooling water supplied from the nozzle headers 40a, 40b. And a traveling vehicle 50 for traveling the nozzle headers 40a and 40b for performing inter-running cooling, and cooling water is supplied to the billet during acceleration / deceleration when the traveling speed of the traveling vehicle 50 is synchronized with the billet traveling speed. The masking devices 60a, 60b, 62a, and 62b at the time of vertical acceleration and deceleration are provided so as not to cover.

The upper and lower nozzle headers 40a, 40b
Is connected via the connecting member 46 or directly to the traveling vehicle 50 so as to move at the same speed as the traveling vehicle 50.

The traveling carriage 50 is composed of wheels 54 driven by a drive motor 52 and a body 56 supporting the wheels 54 and the nozzle header, and is disposed above the steel bill by the drive motor 52, for example. The vehicle travels on the rail 58 for the traveling distance C.

The operation of the first embodiment will be described below.

First, the cutting device 18 cuts the rear end of the preceding steel slab 10a and the front end of the following steel slab 10b.

Next, at the joining device 22, the rear end of the preceding steel slab 10a and the front end of the following steel slab 10b are connected as shown in FIG.
And as shown in FIG. 3, they are opposed to each other with a gap.

Next, an alternating magnetic field A is applied in the thickness direction of the steel slab to the alternating magnetic field generating coil 32 arranged so as to cover the rear end of the opposing preceding slab 10a and the front end of the following slab 10b. Thereby, the rear end of the preceding slab 10a and the front end of the following slab 10b are heated in the slab width direction.

The slab heated and joined by the joining device 22 is
The joint cooling device 26 cools only the area immediately adjacent to the joint. Specifically, the traveling vehicle 50 is at the standby position D in FIG.
It stops until the joint of the billet approaches the predetermined position.
When the joint arrives at the predetermined position, the traveling vehicle 50 starts accelerating as shown by the solid line I, reaches the billet speed (dashed line H) within the acceleration masking range, and at a position E outside the acceleration masking range. The upper and lower nozzle headers 40a and 40b move above and below the joint. The traveling vehicle 50 moves in a predetermined range indicated by positions E to F in FIG. 5 in synchronization with the speed of the steel slab, then decelerates within the deceleration masking range and stops at the predetermined position G. FIG. 5 shows an example of the relationship between the speed of the billet (dashed line H) and the speed of the traveling vehicle (solid line I) when the speed of the billet is constant. The traveling vehicle has a predetermined range E outside the masking range during acceleration / deceleration.
Between F, it moves in synchronization with the speed of the billet.

In the nozzle 42, a valve 44 is opened in advance so as to start injection within a masking range during acceleration. Therefore, when the nozzle 42 is out of the masking range at the time of acceleration, since the upper and lower nozzles 42 are located above and below the joint, the nozzle 42 is directly poured only into the joint, and only the immediate vicinity of the joint is cooled. . The traveling trolley 50 has a predetermined range E
Since the cooling water moves between F in synchronization with the speed of the billet, the cooling water is injected only to the joint.

When the traveling vehicle enters the deceleration masking range, the valve 44 is closed and the injection of the cooling water is stopped.

The cooling water injected within the acceleration / deceleration masking range does not cool the steel slab,
a, 60b, 62a, 62b.

In the above description, the steel slab is cooled from the vertical direction. However, the steel slab may be cooled only from the upper or lower direction. For example, when cooling only from above, the lower nozzle header 40b, the connecting member 46,
The lower masking devices 60b and 62b are unnecessary. on the other hand,
When cooling from only the lower direction, the upper nozzle header 40
a, The upper masking devices 60a and 62b are unnecessary.

Before and after the joining portion passes over the table roller 70, the cooling water from the lower nozzle is blocked by the table roller 70 and cannot be sprayed on the joining portion of the billet, or scatters on the table roller 70. Therefore, the actual cooling length becomes shorter. Therefore, it is desirable to use the upper nozzle as a cooling method.

Since it takes time from the opening of the valve to the stable discharge of water, it is desirable that the valve be located immediately close to the nozzle 42. However, in the present invention, there is a masking means and the water is discharged in advance. Therefore, a valve may be provided on the header.

Next, a second embodiment of the present invention will be described in detail with reference to FIG.

In the second embodiment, a plurality of nozzle headers (80a, 82a in FIG.
a, 80b, and 82b at the top and bottom, respectively, so that the nozzle header to be used can be changed by, for example, the product of the billet thickness and the billet transfer speed.

It is known that the cooling capacity of a normal water spray is proportional to the 0.8 power of the water flow density of the slab. Therefore, the product of the slab thickness and the slab transport speed is about 1/2 of the maximum value. In this case, as shown in FIG. 6, two types of nozzle headers are provided, and the flow rate of the smaller nozzle is set to 4 times that of the larger flow rate nozzle.
It is preferable to use about 0%.

In the above-described embodiment, the present invention is applied to cooling of a steel slab joint. However, the application of the present invention is not limited to this, and a sheet of a general metal slab other than a steel slab is used. Obviously, the same applies to the cooling of the bar joints. The coolant is not limited to water.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS For example, a low-carbon steel sheet bar having a width of 1000 mm and a thickness of 30 mm is supplied to the line shown in FIG. 1 as a leading billet 10a and a trailing billet 10b, respectively. And the leading end of the following sheet bar is 5m
m, and an alternating magnetic field generating coil (for example, a width of 1300 mm and a length of 240 mm) covers the gap.
mm) 32 and then heated by applying an alternating magnetic field A. The heating conditions at this time are as follows.
Heating was performed for 12.5 seconds at a frequency of 1000 Hz with KW. Subsequently, the steel slab was pressed with a pressing force of 2 kgf / mm ² to complete the joining.

Next, 10 seconds after the completion of joining, the traveling distance C
= Water flow density of 8000 l /
Cooled for 2.5 seconds with an m ² minute water spray. FIG. 7 compares the temperature distribution on the entrance side of the finishing mill in the case of conventional cooling without cooling, and without masking with cooling during running, and with the cooling according to the present invention and with masking according to the present invention. Show.

After cooling, a plate thickness of 2 mm was obtained using a 7-stand mill.
Rolling was performed up to, but the one subjected to cooling by the method of the present invention was able to continue good continuous rolling without separation of the joining surfaces during rolling.

[0047]

According to the present invention, it is possible to accurately and responsively cool only the vicinity of the running seat bar joint, and to perform accurate cooling control without excessive cooling before and after the joint. . Therefore, good continuous rolling can be continued without separating the sheet bar joining portion during rolling after joining.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an inlet-side transfer line of a finishing mill into which a first embodiment of a joint cooling device according to the present invention is incorporated.

FIG. 2 is a side view showing a basic configuration of a joining device used in the entrance-side transfer line.

FIG. 3 is a plan view of the same.

FIG. 4 is a side view showing a configuration of the joint cooling device.

FIG. 5 is a diagram for explaining the operation of the joint cooling device.

FIG. 6 is a side view showing the configuration of a second embodiment of the joint cooling device according to the present invention.

FIG. 7 is a diagram for explaining the operation of the method of the present invention in comparison with the conventional method.

[Explanation of symbols]

10a Leading billet 10b Trailing billet 10c Butt 22 Joining device 26 Joining cooling device 30 First finishing mill stand 40a, 40b, 80a, 80b, 82a, 82b Nozzle header 42 Nozzle 44 ... valve 46 ... connecting member 50 ... traveling carriage 52 ... drive motor 54 ... wheels 56 ... body 58 ... rails 60a, 60b ... acceleration masking device 62a, 62b ... deceleration masking device

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI C21D 9/52 102 C21D 9/52 102 9/573 101 9/573 101Z (72) Inventor Hideyuki Nikaido Kawasaki, Chuo-ku, Chiba-shi, Chiba No. 1 Kawasaki Steel Corporation Chiba Works (72) Inventor Shigefumi Katsura 1 Kawasaki-cho Chuo-ku, Chiba City, Chiba Prefecture Kawasaki Steel Corporation Chiba Works (72) Inventor Shigeru Isoyama Chuo-ku Chiba City, Chiba Prefecture 1 Kawasaki-cho, Chiba Works, Kawasaki Steel Co., Ltd. 6-22, Shinmachi, Hiroshima Works, Mitsubishi Heavy Industries, Ltd.

Claims (3)

[Claims] 1. Prior to hot finish rolling, the sheet bar joint is cooled when the rear end of the preceding sheet bar and the front end of the succeeding sheet bar are butt-joined by heating, heating and pressing. During the acceleration / deceleration when the running speed of the cooling unit is synchronized with the running speed of the seat bar, the cooling agent and the masking device that run in synchronization with the running speed of the seat bar are used. A method for cooling a sheet bar joint in hot rolling, characterized in that only the area immediately adjacent to the sheet bar joint is cooled so as not to cover. 2. The cooling device according to claim 1, wherein a plurality of types of the cooling means are provided, and a type and a cooling time of the cooling means to be used are determined according to a thickness of the sheet bar, a traveling speed, and a junction temperature. Method of cooling the sheet bar joint in hot rolling. 3. A cooling device for a sheet bar joint portion in which a rear end portion of a preceding sheet bar and a front end portion of a succeeding sheet bar are heated and heated, pressed and butt-joined before hot finish rolling. In the above, a traveling vehicle, which is equipped with a cooling means for cooling a seat bar joint, and which travels in synchronization with the traveling speed of the seat bar, and acceleration / deceleration when the traveling speed of the traveling vehicle is synchronized with the traveling speed of the seat bar. A cooling device for a sheet bar joint in hot rolling, comprising: a masking means for preventing a coolant from splashing on the sheet bar inside, and cooling only a portion immediately adjacent to the sheet bar joint.