JPH09155429A - Method for passing hot rolled steel plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To straighten and remove the floating and waving of a hot rolled steel plate by spraying the water jet in the traveling direction in the vertical face of a tip part of the steel plate before the tip part of the hot rolled steel plate leaves the final rolling stage and enters a run-out cooling zone. SOLUTION: A nozzle group 6 is installed close to an outlet side of a work roll 1 of the final stage of a finish rolling mill. The cooling water 7 is sprayed from a spray group of the nozzle group 6 in the advancing direction of a hot rolled steel plate 2 before the hot rolled steel plate leaves the final stage of the finish rolling mill and enters the run-out cooling zone so as to have the horizontal velocity component not to interfere the advancement of the steel plate 2 or to assist the advancement. Passing of the tip part of the hot rolled steel plate 2 is stabilized. The horizontal velocity component of the water jet in colliding with the hot rolled steel plate 2 is preferably not less than the passing speed of the hot rolled steel plate 2. The water jet is preferably sprayed at the position within 5m from the final stage of the finish rolling mill.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hot rolling process in the production of a hot rolled steel sheet, in which the leading end portion of the steel sheet is hot rolled until it exits the finish rolling mill, passes through a runout table, and reaches a winding machine. The present invention relates to a threading method that allows a steel sheet to pass stably.

[0002]

2. Description of the Related Art In hot rolling, the tip of a steel sheet sent from a finish rolling mill travels by a table roller installed on a run-out table, and when it is wound on a winder, the rolling speed and feed rate are The winding speed is synchronized, and the subsequent steel plate can be stably wound into a coil.

However, when manufacturing a thin product having a thickness of 1.2 mm or less, the tip of the hot-rolled steel sheet floats up,
Or often wavy. FIG. 3 is a side view showing the state of rising and corrugation of the tip of the hot-rolled steel sheet in the production of thin products. In the figure, 1 is a final work roll, 2 is a hot rolled steel plate, and 3 is a table roller. Due to such a phenomenon, a defect such as a product material and a surface property may occur, or in an extreme case, the traveling of the steel plate may be defective and the winding may be impossible.

Therefore, when manufacturing a thin product, the feeding speed of the hot-rolled steel sheet is kept until the tip end is wound up.
It should be set lower than the speed achieved in steady state. Here, the steady state is a state in which the leading end of the hot-rolled steel sheet is wound around the winder and the manufacturing conditions are stable. Therefore, not only is productivity reduced,
The yield was reduced because the quality of the unsteady part at the tip of the steel plate did not meet the standard.

In response to this problem, a fluid such as high-pressure cooling water is sprayed from the lower side, the upper side, or both the upper and lower sides of the run-out cooling zone to the tip of the sheet to assist the running of the hot-rolled steel sheet,
Alternatively, a method of preventing floating has been taken. Examples of such conventional techniques include JP-A-54-33015 (Prior art-1), JP-A-3-226306 (Prior art-2), and JP-A-50-7762 (Prior art). -3), Japanese Patent Application Laid-Open No. 5-131217 (Prior Art-4) and the like are known.

FIG. 4 is a side view showing an outline of a technique for injecting high-pressure cooling water in this runout cooling zone. In the figure, 4
Indicates a high-pressure nozzle, and 5 indicates high-pressure cooling water, and other symbols are the same as in FIG.

There is also a method of sucking the tip of the hot-rolled steel sheet, and as an example of a method using electromagnetic force, Japanese Patent Laid-Open No. 2-55
There is a technique described in Japanese Patent No. 610 (conventional technique-5).

In addition to these methods, there has been taken a method of facilitating the passing of a steel sheet by plastically working the tip of the hot-rolled steel sheet to improve its rigidity. Examples of this technique include JP-A-56-33119 (Prior art-6) and JP-A-5-185128.
The techniques described in (Prior Art-7) and the like are known.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention Prior Art 1 to 1
In 5, these mechanisms work effectively only after the tip of the plate has been pumped into the runout cooling zone.
Therefore, at this point, the length of the hot rolled steel sheet effectively reaches 10 m or more. For example, as shown in FIG. 4 described above, the rising and waviness of the hot-rolled steel plate 2 in the portion hit by the high-pressure cooling water 5 can be suppressed, but waviness remains on the upstream side.
Although these mechanisms have the effect of correcting the acting portion, they can be said to be ineffective against the waving generated on the upstream side.

The reason is as follows. In order to correct the undulation once generated at a distance, it is necessary to stretch the hot-rolled steel sheet in the traveling direction and correct the unbalance (slackness) of the length of the undulated sheet with respect to the straight length in the passing direction. . However, when the steel plate length reaches 10 m, the weight of the hot-rolled steel plate becomes considerably large, so that it is practically impossible to stretch the plate in the traveling direction by the force of the fluid or the electromagnetic force.

Further, as in the case where the fluid is sprayed from the direction perpendicular to the plate, the pressing force can be applied only in the vertical direction, that is, in the case where there is only the velocity component perpendicular to the plate passing direction. However, momentum is exchanged between the hot-rolled steel sheet and the fluid, and instead of the fluid obtaining a velocity component in the traveling direction of the sheet, the hot-rolled steel sheet receives a force opposite to the traveling direction. . As a result, when the fluid is sprayed from the direction perpendicular to the steel sheet, the speed of the tip of the hot-rolled steel sheet becomes lower than the speed of the subsequent portion, causing slack in the subsequent steel sheet, which promotes corrugation of the steel sheet. .

In the above-mentioned prior art-6 and 7, when the tip is machined, the tip is inevitably warped upward with respect to the traveling direction due to the machining. Therefore, when passing through the plate, lift force of the air is generated and it rises like a kite. Thus, this technique has the factor of reducing the effect even if the rigidity of the tip of the plate is increased. In addition, it is practically difficult to correct the deformation of the hot rolled steel sheet due to working, and moreover, when wound on a coil, it is wound on the innermost layer,
It is also difficult to remove that part.

The present invention solves these problems and provides a method of correcting and removing the rising and waviness of a hot-rolled steel sheet at the time of its formation.

[0014]

According to a first aspect of the present invention, there is provided a method for threading a hot-rolled steel sheet in a hot rolling mill, wherein the hot-rolled steel sheet has a tip portion which has left the final stage of the finish rolling mill, and a runout. It is a method for passing a hot-rolled steel sheet, characterized by injecting a water flow in the traveling direction of the hot-rolled steel sheet onto both the upper and lower surfaces of the tip of the hot-rolled steel sheet before entering the cooling zone.

According to the present invention, immediately after the rising or corrugation of the tip of the hot-rolled steel sheet occurs, a water stream is simultaneously jetted to the tip of the hot-rolled steel sheet from the upper side and the lower side of the hot-rolled steel sheet. Remove the corrugation and keep the hot rolled steel flat. This is possible in the present invention, since the hot-rolled steel sheet is straightened at the time when the length from the tip of the hot-rolled steel sheet is short and the mass of the tip portion is small, the lifting and waviness are suppressed with a small force. Because you can do it. Therefore, an effective correction action occurs even with the force of the fluid.

Since the water flow also has a velocity component perpendicular to the passing direction of the hot-rolled steel sheet, a force for returning the hot-rolled steel sheet deformed in the direction away from the horizontal plane to the horizontal direction works. Since the water flow injected from the nozzle decreases in flow rate as it moves away from the nozzle, the pressure received from the cooling water flow increases as the hot-rolled steel plate deforms greatly and approaches the nozzle. for that reason,
Intermediate point between the upper and lower nozzles, that is, the plate transport surface (horizontal plane)
The restraining force that makes the position of S is a stable position acts on the hot-rolled steel sheet.

Further, by using water having a great cooling effect as the fluid, the temperature of the tip of the hot-rolled steel sheet can be lowered to increase the strength, so that the tip of the hot-rolled steel sheet can be maintained in a flat state. is there.

According to the invention of claim 2, the horizontal velocity component of the water flow at the time of collision with the hot-rolled steel sheet is set to be equal to or higher than the threading speed of the hot-rolled steel sheet. It is a method of threading.

In the present invention, the horizontal velocity component of the water flow at the position of the conveying surface of the hot-rolled steel sheet is set to be equal to or higher than the passage speed at the tip of the hot-rolled steel sheet. As a result, the relative velocity of the water flow with respect to the hot-rolled steel sheet comes to face the strip passing direction,
Due to the viscosity of the water flow, a force that pulls the steel sheet in the sheet passing direction is generated. Therefore, it is possible to not only prevent the hot-rolled steel sheet from rising and corrugating, but also to extend the slack generated in the hot-rolled steel sheet.

The invention according to claim 3 is the method for threading a hot-rolled steel sheet according to claim 1 or 2, characterized in that the water stream is injected at a position within 5 m from the final stage of the finishing rolling mill.

The present invention utilizes the phenomenon that the hot-rolled steel sheet is less lifted and corrugated when the position of the water jet is closer to the final stage of the rolling mill, as will be described later in the embodiment section. ing. By positioning the nozzle within 5 m from the last stage of the finishing rolling mill, the maximum vertical displacement of the hot-rolled steel sheet can be suppressed within a range that does not hinder practical use.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention.
It is a figure showing an example. In the figure, 1 is the final work roll,
2 is a steel plate, 3 is a roller, 6 is a nozzle, and 7 is a water flow.

The present invention makes it possible to improve the running of the hot-rolled steel sheet by injecting a water cooling nozzle provided immediately after the finish rolling mill according to predetermined conditions. As shown in FIG. 1, the constituent element of the present invention is composed of a nozzle group 6 installed above and below the hot-rolled steel plate 2 close to the exit side of the work roll 1 at the final stage of the finish rolling mill. By controlling the cooling water 7 from the spray group 6 so as to have a horizontal velocity component that does not hinder the progress of the steel sheet in the traveling direction of the hot rolled steel sheet 2 or assists the progress of the hot rolled steel sheet 2, It realizes the stability of the threading at the tip of the.

FIG. 2 is an enlarged view showing the arrangement of the water stream 7 and its surroundings. In the figure, H is the vertical displacement of the steel plate,
V is the strip speed, Vx is the horizontal velocity component of the water flow, Vy is the vertical velocity component of the water flow, and the other symbols are the same as in FIG.

In this figure, the cooling water 7 sprayed from the nozzle 6 has a horizontal velocity component at the point of collision with the hot-rolled steel plate 2.
It has Vx and vertical velocity component Vy (both are average values). It is desirable that the horizontal velocity component Vx be equal to or higher than the transport velocity V of the steel plate, as described later.

[0026]

EXAMPLES Examples of the invention in the production of hot-rolled steel sheet having a thickness of 1.2 mm will be described below. A plurality of nozzle groups 6 are arranged in the strip width direction, and are installed at a position at a distance L from the finish rolling mill.

Table 1 shows that, when the distance L from the finishing rolling mill to the nozzle was changed, the tip of the hot-rolled steel sheet passed through the nozzle for 1 second by the displacement gauge installed at a position 2 m from the finishing stand. 3 is a table showing the results of measuring the maximum value of the vertical displacement H of the steel sheet between

When the distance L is short, the vertical displacement H of the hot-rolled steel sheet is suppressed to a small value, but the displacement H increases as the distance L increases. Especially, the distance L is 5m
Displacement H is suppressed to less than 20 cm until
When L becomes 7 m, the displacement H becomes 40 cm or more, and the effect decreases.

[0029]

[Table 1]

Table 2 is a table showing the relationship between the horizontal and vertical velocity components Vx and Vy of the water flow and the maximum displacement of the steel sheet. The maximum value of the displacement H of the steel sheet is obtained by measuring the vertical displacement of the steel sheet with a displacement meter installed at a position 2 m from the finishing stand, and measuring the maximum value for 1 second after the tip of the hot-rolled steel sheet passes through the nozzle. Using.

From this table, the vertical displacement H of the hot rolled steel sheet
It can be seen that the maximum value of is strongly dependent on the horizontal velocity component Vx of the water flow. When the horizontal velocity component Vx of the water flow is smaller than the stripping velocity V of the hot-rolled steel sheet, the maximum displacement H of the steel sheet is about 30 cm or more in all cases. On the contrary,
When the horizontal velocity component Vx of the water flow is higher than the strip velocity V of the hot-rolled steel sheet, the maximum displacement H of the steel sheet is 20 cm in all cases.
Less than.

By the way, even if the horizontal velocity component Vx is larger than the steel sheet passing velocity V, if the vertical velocity component Vy of the water flow is 0, the displacement of the steel sheet can be sufficiently suppressed as shown in the comparative example. Can not. Therefore, the vertical velocity component of the water flow
It is desirable that Vy also has a certain size (100 mpm).

[0033]

[Table 2]

In the following example, the distance L from the finishing mill is
Was set to 1 m. It was set to turn off the cooling water 0.5 seconds after another displacement gauge installed under the nozzle detected the tip of the plate. At this time, the tip of the hot rolled steel sheet is
It was also clarified from the visual observation result by the video installed immediately before the winder that the temperature was lowered by 350 ° C. Therefore, it is considered that the rigidity of the tip of the hot rolled steel sheet is also improved. When the maximum displacement H of the steel sheet was more than 50 cm, it was around 30% in the comparative example, but was 0% in this example, which was not seen at all.

According to the present embodiment, it is possible to improve the threading speed of the tip of the hot-rolled steel sheet to enhance the productivity and reduce the length of the defective portion of the tip to about half. In this embodiment,
In order to effectively drain the cooling water from the lower side in the plate transport direction, the transport rollers are grooved.

[0036]

According to the present invention, the nozzle for injecting the cooling water is provided immediately after the finish rolling mill and the injection angle, the flow velocity and the time are controlled, so that the rising and corrugation of the hot rolled steel sheet are removed and prevented. I can. Further, since the strength can be increased by lowering the temperature of the tip of the hot-rolled steel sheet, it is possible to stabilize the threading or pass it at a higher speed, and at the same time, to remove the defective portion of the tip of the hot-rolled steel sheet. Decrease,
Product yield can be improved.

[Brief description of the drawings]

FIG. 1 is a side view showing an example of an embodiment of the present invention.

FIG. 2 is an enlarged view showing the arrangement of the water flow and its periphery in the present invention.

FIG. 3 is a side view showing the rising and waviness of the tip of a steel sheet in a conventional example.

FIG. 4 is a side view of a conventional example in which high-pressure water is jetted from above.

[Explanation of symbols]

 1 Final stage work roll 2 Hot rolled steel plate 3 Roller 7 Water flow V Thread speed Vx Horizontal velocity component of water flow

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toru Minote 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Masaaki Yamamoto 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Co., Ltd.

Claims (3)

[Claims] 1. A method for threading a hot-rolled steel sheet in a hot-rolling mill, comprising the step of removing the hot-rolled steel sheet after the leading end of the hot-rolled steel sheet leaves the final stage of the finish rolling mill and before entering the runout cooling zone. A method for passing a hot-rolled steel sheet, characterized by injecting a water flow directed in the traveling direction of the hot-rolled steel sheet onto both the upper and lower surfaces of the tip portion. 2. The method of passing a hot-rolled steel sheet according to claim 1, wherein the horizontal velocity component of the water flow when the hot-rolled steel sheet collides with the hot-rolled steel sheet is equal to or higher than the passing speed of the hot-rolled steel sheet. 3. The method of passing a hot-rolled steel sheet according to claim 1, wherein the water stream is injected at a position within 5 m from the final stage of the finish rolling mill.