JPH07102384B2 - Hot rolling method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hot rolled steel strip having a plate thickness of 1 mm or more and 2 mm or less by a hot strip mill.

[0002]

2. Description of the Related Art In recent years, hot-rolled steel strip having a thin plate thickness has been manufactured by a hot strip mill. This hot rolled steel strip is a rough pressure machine,
It is rolled by a finishing rolling mill, sent out onto a hot run table at a finishing exit speed of about 700 m / min, travels on a hot run table of about 200 m, and is then wound into a hot coil by a winding machine. The rolled material is often cooled by water injection on a hot run table.

FIG. 1 (A) is an explanatory view of an example of abnormal stripability that occurs while the tip of a rolled material is running on a hot run table. The rolled material 1 coming out of the roll 2 of the final finishing rolling mill is placed on the rotating table roller 4, and by the pushing force of the roll 2 and the rotation of the table roller 4, the rolled material 1 advances in the direction of the arrow 6 and winds up. Reach 3. Reference numeral 5 is a water injection cooling nozzle.

When the thickness of the rolled material 1 exceeds 2 mm, it hardly occurs, but when the thickness of the rolled material is 2 mm or less,
When the tip portion travels on the hot run table, abnormal rolling properties such as tip bending 1-1 and rising 1-2 are likely to occur in the rolled material. Therefore, in the case of a rolled material having a thickness of 2 mm or less, there arises a problem that, due to abnormal stripability, for example, smooth winding by the winding machine 3 is hindered or the upper water cooling nozzle 5 is damaged.

[0005]

The present invention has a thickness of 2 m.
An object of the present invention is to provide a hot rolling method that solves the problem of the stripability and the problem due to the stripability that occurs in the case of rolled materials of m or less.

[0006]

Means and Actions for Solving the Problems In the present invention, when a hot strip mill with a sheet thickness of 1 mm or more and 2 mm or less is manufactured at a finishing exit speed of 700 m / min or more, the tip of a rolled material is used. While the part is running on the hot run table, a deceleration threading that applies a negative acceleration of 30 m / min or more per second for 0.5 seconds or more is applied to the finishing exit speed at least once. It is a rolling method.

FIG. 1B is an explanatory view of the hot rolling method of the present invention. When abnormalities 1-1 and 1-2 in FIG. 1 (A) occur, the finishing outlet speed is changed from V ₁ as shown in FIG. 1 (B).
Decelerate to (V ₁ −ΔV). At this time, the rolled material 1 running on the hot run table tries to continue running in the direction of arrow 6 at a speed commensurate with V ₁ , but the final finish rolling roll 2 restrains the end portion. Therefore, an inertial force acts on the rolled material 1 traveling on the hot run table, and the inertial force corrects the shape of the abnormal strip passage, so that the rolled material 1 becomes a smooth strip.

The present inventors have found that the finish outlet speed before deceleration is 7
Rolled material with a plate thickness of 1.2 mm and plate thickness of 1.8 mm at 50 m / min
For the rolled material of No. 2, the tip of the rolled material exited the roll 2 of the final finishing rolling mill, and 8 seconds and 15 seconds later, the negative acceleration of the magnitude shown in FIG. The rolling speed was applied and the occurrence of abnormal stripability was observed. As shown in FIG. 2, if the magnitude of the negative acceleration is less than 30 m / min per second, it is insufficient to prevent the abnormal stripability. In addition, it is necessary to give negative acceleration over 0.5 seconds or more.

The present inventors performed deceleration threading similar to that shown in FIG. 2 once 12 seconds after the tip of the rolled material exited the roll 2 of the final finishing mill, but it was roughly the same as in FIG. Results were obtained. Therefore, in the present application, while the tip of the rolled material is traveling on the hot run table, deceleration threading for performing negative acceleration of 30 m / min or more per second for 0.5 seconds or more is finished at least once or more. Apply to exit speed.

The present invention is intended for a hot rolled steel strip having a plate thickness of 1 mm or more and 2 mm or less. If the plate thickness is less than 1 mm, it is rarely manufactured by a hot strip mill, and the plate thickness is 2 m.
In the case of hot-rolled steel strips exceeding m, occurrence of abnormal stripability is rare. Therefore, it is limited to 1 mm or more and 2 mm or less.

In the present invention, the initial finishing outlet speed is 700 m /
Be more than a minute The hot-rolled steel strip with a plate thickness of 1 mm to 2 mm is 7
Rolling at an initial finishing outlet speed of less than 00 m / min lowers the productivity (ton / hour), lengthens the rolling time, changes the temperature at the tip and tail portions, and causes fluctuations in the coil quality. Become.

In the present invention, since the reduced speed threading is performed, it is feared that the rolling speed after the reduced speed threading is lowered and the productivity is impaired. However, the initial rolling speed is set so that the rolling speed after the reduced speed threading becomes a normal rolling speed. By setting the finishing outlet speed, productivity is not reduced.

[0013]

By carrying out the present invention, the thickness is 2
It is possible to effectively prevent the stripability abnormality that occurs when hot-rolling a rolled material having a thickness of mm or less. For this reason, it is possible to prevent problems such as winding problems and damages to the upper water injection nozzle that occur due to the abnormal sheet passing property.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing the occurrence of a stripping abnormality and a method of preventing a stripping abnormality according to the present invention, and FIG. 2 is a diagram showing the relationship between deceleration threading and the occurrence of stripping abnormality.

[Explanation of symbols]

1: Rolled material 1-1: Tip bending, 1-2: Rise, 2: Roll of final finishing rolling mill, 3: Winding machine,
4: Table roller, 5: Water injection cooling nozzle.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Takashi Yamanoji 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Co., Ltd. Kimitsu Steel Co., Ltd. (56) Reference JP-A-59-144509 (JP, A)

Claims (1)

[Claims] 1. When manufacturing a hot-rolled steel strip having a plate thickness of 1 mm or more and 2 mm or less with a hot strip mill at an initial finishing outlet speed of 700 m / min or more, the tip of the rolled material is run on a hot run table. 30m / s during one second
A hot rolling method, characterized in that deceleration threading for performing negative acceleration of 0.5 minutes or more for 0.5 seconds or more is applied to the finishing exit speed at least once.