JP3283705B2 - Prevention method of ear wave shape generation of thick steel plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention focuses on the fact that a steel sheet wave generated at the widthwise end of a thick steel sheet is generated due to a temperature deviation in the width direction of the steel sheet during cooling. The present invention relates to a method for reducing the temperature deviation during cooling by partially cooling the center portion of the substrate with water, thereby preventing the wave generated at the end in the width direction without changing the material.

[0002]

2. Description of the Related Art Conventionally, a steel sheet wave (ear wave) generated at an end portion in a width direction expected after cooling when passing a thick steel sheet through a device is generated by a hot rolling mill or a hot straightening machine after rolling. A method was adopted in which a slight steel sheet wave (medium wave) was generated at the center to overcompensate and prevent the steel sheet wave.

[0003]

After the steel sheet is rolled in hot rolling, the widthwise end of the steel sheet is cooled, and as a result, tensile stress is generated at the widthwise end by thermal stress,
At this time, if the temperature difference is too large, the generated stress is too large, and plastic elongation occurs at the end due to tensile stress. This elongation remains even if the steel sheet is cooled to room temperature, and remains as an ear wave at the widthwise end of the steel sheet. In many cases, a steel sheet having a wavy shape does not satisfy the required flatness of a product, and a great load including a straightening process is required to correct the wavy shape. In the conventional method using a rolling mill or a hot straightening machine, it was almost impossible to prevent the occurrence of plastic elongation due to such thermal stress.However, the present invention provides a method for controlling the shape after rolling or after hot straightening. An object of the present invention is to provide a method for reliably preventing the occurrence of thermal stress by controlling the water density and preventing the generation of an undulating shape in the rolling of a thick steel plate.

[0004]

SUMMARY OF THE INVENTION The method for preventing the generation of an undulating shape of a thick steel plate according to the present invention has been invented in order to solve the above-mentioned problems, and is provided downstream of a hot rolling mill in a hot rolling line. From the upstream side, place roller table 2 on threading line 7
Immediately after rolling, a steel sheet thermometer 3 is arranged to measure the surface temperature of the steel sheet from above, and three laser distance meters are arranged in the width direction from above the roller table 2 to determine the steel sheet shape from the steel sheet distance at each position. The steel plate shape meter 4 is arranged.
A hot straightening machine 11 for straightening the steel sheet immediately after rolling is arranged, and a steel sheet thermometer immediately before cooling 5 for measuring the surface temperature of the steel sheet M immediately after cooling from above the roller table 2 behind the hot straightening machine 11.
Place. Further, a water-flow shielding plate 6 for restricting the flow of water to the widthwise end portion is attached to the rear thereof, and a water-cooled steel plate for flowing water from both the upper and lower directions of the roller table 2 toward the steel plate passing surface on the table. The device 8 is arranged. Subsequently, the steel plate shape is detected by a facility in which a steel plate thermometer 9 immediately after cooling for measuring the surface temperature of the steel plate immediately after cooling and a steel plate shape meter 10 immediately after cooling similar to the steel plate shape meter 4 immediately after rolling are arranged. In the case where a wave is generated at the end, there is a method of preventing an ear wave shape of a thick steel plate by shielding the steel plate end portion, cooling only the central portion of the steel plate, and obtaining good flatness.

[0005]

According to the present invention, in order to reduce the temperature deviation in the width direction.
Water cooling does not change the material Ar _Three Start from below the transformation temperature
Is preferred. This cooling by water cooling is usually
Because it is a method involving material change,
Cool under component and water cooling conditions that do not fluctuate to reduce material changes.
Do not generate. The running water shield (edge mask 6) at the end is intentionally made of steel
Cools only the central part, and the temperature in the width direction
Performed to reduce the difference. This reduces temperature deviations
This reduces the tensile thermal stress generated at the end and suppresses plastic elongation
The ear waves are prevented. Hot straightener (Hot Leveler) immediately after rolling
Excessive steel with a wave height exceeding about 10 mm
Operates when removing plate waves by straightening.

Hereinafter, features of the present invention will be described with reference to the drawings. FIG. 1 is a layout drawing of a rolling line to which the present invention is applied, and FIGS. 2 and 3 show a water cooling device and a running water shielding device (edge mask 6). FIG. 2 is a front view and FIG.
Shows a cross-sectional view taken along line AA of FIG. FIG. 4 is a diagram showing the flow of cooling control of the feedforward steel sheet according to the present invention.

In FIG. 2, the water cooling device for the steel sheet M is such that a laminar flow type cooling device R is disposed on the upper side and a spray type cooling device S is disposed on the lower side. R comprises a header H2 and a laminar flow nozzle RN, and S comprises a header H1 and a spray nozzle SN. The flowing water shielding device 6 includes a shielding member 30 that can move in the width direction according to the width of the steel sheet M on both upper and lower sides of the steel sheet passage, receives cooling water from the opposed nozzle, and drains the cooling water from the steel sheet conveying path. A screw shaft 32 which is screwed into a screw nut 31 provided on the shield 30 to move the shield 30 in the width direction of the steel plate by rotation.
And a motor 33 for driving the screw shaft 32 to rotate. The threaded portions provided on both sides of the screw shaft 32 are formed so as to face in opposite directions, and are configured to move the shield 30 toward the center of the steel sheet by rotating the shaft in the forward direction and toward the steel sheet edge by rotating the shaft in the reverse direction. It is.

In FIG. 1, after a steel sheet M is rolled by a hot rolling mill 1 along a threading line 7, the rolling end temperature of the steel sheet is measured by a steel sheet thermometer 3 immediately after rolling. Determine the cooling start temperature from the temperature measured by thermometer 3,
If the cooling start temperature is high enough to give a remarkable quenching effect to the steel sheet, the water cooling by the water cooling equipment 8 is stopped. Immediately after rolling, a steel sheet shape meter 4 is installed downstream of the line of the steel sheet thermometer 3 and measures the shape of the steel sheet immediately after rolling by measuring three points in the width direction with a laser distance meter to determine the shape. Enter the wave shape, wave pitch, and wave height of the steel sheet in the following.

According to the input information, if the steel sheet has a corrugated shape only at the widthwise end after hot rolling, or is flat without any corrugated shape,
If the difference between the center temperature of the steel sheet and the end temperature of the steel sheet near the steel sheet temperature of 600 ° C. (hereinafter referred to as “temperature deviation in the width direction of the steel sheet”) is 20 ° C. or more, the plastic elongation of the steel sheet having a thickness of 6 mm with ordinary air cooling is obtained. In order to prevent the occurrence of temperature deviation in the width direction of the steel sheet, the water cooling device 8 sets the steel sheet temperature to 600 ° C.
Before the temperature deviation in the width direction becomes maximum between 700 ° C. and 700 ° C., the roller table 2 using the width direction end running water shielding device 6 is used.
Only the central portion of the upper steel sheet M is water-cooled, and the temperature is lowered to room temperature without increasing the width-direction temperature deviation. In this case, an appropriate cooling water density and a corresponding flow rate are transmitted to the downstream cooling equipment control device so that the temperature in the width direction end becomes a temperature deviation in the steel sheet width direction appropriately higher than the temperature in the center. Upon receiving this signal, the control device starts flowing water.

The steel sheet M is straightened by the hot-rolling straightening machine 11 so that the temperature of the steel sheet surface temperature is measured by the thermometer 5 just before cooling, and the temperature prediction accuracy immediately before cooling is determined for each steel sheet. In order to increase the temperature, a learning coefficient for the temperature drop after rolling of the sheet thickness and the temperature range used for the temperature calculation in the process controller is compared with the temperature immediately before cooling calculated from the temperature immediately after rolling.

When the steel sheet enters the water cooling device 8 for cooling, the steel plate M is unconstrained in order to avoid uneven cooling by equipment such as the constraining roll 13, and the end in the width direction of the steel plate is shielded by the shielding device 6. In advance, the steel sheet M is allowed to enter the running water at a threading speed already calculated and set to cool the steel sheet M.
Immediately after cooling steel sheet thermometer 9 located immediately after steel sheet water cooling device 8
By measuring the temperature in the width direction central part and the end part of the steel sheet M, calculating the temperature deviation in the width direction of the steel sheet, and comparing with the calculated respective temperature in the width direction, the cooling temperature drop at the time of water cooling. The learning of the learning coefficient is performed and reflected in the temperature drop prediction of the material after the next material.

Further, in order to accurately predict the shape of the steel sheet at the time of cooling at room temperature, the shape of the steel sheet when cooled to room temperature is measured by the steel sheet shape meter 10 immediately after cooling located downstream of the line. From the steel sheet shape, cooling start temperature, steel sheet width direction temperature deviation just before cooling, temperature just after cooling, steel sheet width direction temperature deviation just after cooling, etc., the prediction accuracy of the cooling temperature deviation and the steel sheet shape at room temperature cooling was improved, Applied to shape prediction of steel sheet after material.

[0013]

EXAMPLE A comparison was made between a water-cooled example of the present invention and a conventional water-cooled non-water cooled example of a sheet material of SS400 having a chemical composition shown in Table 1 and having a steel plate size of 6 mm × 3,000 mm × 15,000 mm. 2 is shown.

[0014]

[Table 1]

[0015]

[Table 2]

As is clear from Table 2, according to the present invention, almost no ear waves are generated in the steel sheet cooled to room temperature by the water cooling effect, whereas the generation of the ear waves is improved in the conventional example. However, the height of the ear wave after rolling was carried over to room temperature as it was, and a large ear wave remained.

[0017]

As is apparent from the above description, the present invention provides a steel plate manufactured without accelerated cooling without causing any change in the material of the steel material, and at the width direction end in the subsequent cooling process. The occurrence of strain elongation is prevented by partially cooling with water, and the flatness of the steel sheet shape after hot rolling and hot straightening is ensured. In addition, if this method is applied, it is possible to prevent and correct the steel sheet wave in the central part in the width direction by installing a device for shielding the central part in the width direction of the steel sheet in the cooling device.

[Brief description of the drawings]

Fig. 1 Equipment layout of rolling line

FIG. 2 is a diagram of a flowing water device and a flowing water shielding device.

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a flow chart of cooling control of a feedforward steel sheet according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hot rolling mill 2 Roller table 3 Steel plate thermometer 4 Steel plate shape meter 5 Steel plate thermometer 6 Running water shielding device 7 Passing line 8 Steel plate water cooling device 9 Steel plate thermometer 10 Steel plate shape meter 11 Hot straightening machine 13 Restraint roll 30 Shield Tool 31 Screw nut 32 Screw shaft 33 Motor M Steel plate S Spray cooling device R Laminar flow cooling device RN Laminar flow nozzle H1, H2 Header

──────────────────────────────────────────────────の Continuation of the front page (51) Int.Cl. ⁷ identification code FI B21C 51/00 B21B 37/00 116K (58) Field surveyed (Int.Cl. ⁷ , DB name) B21B 37/00-37 / 78 B21B 45/02 B21C 51/00

Claims (1)

(57) [Claims] 1. A steel sheet thermometer for measuring the surface temperature of a steel sheet from above a roller table, and a steel sheet shape meter for determining a steel sheet shape in a sheet width direction, on a line on an outlet side of a hot rolling mill, A hot straightening machine that straightens the hot water and a steel sheet thermometer that measures the surface temperature of the steel sheet immediately before cooling from above the roller table, and further behind it, a running water shield that restricts the running water to the end in the sheet width direction The steel sheet water cooling device attached to the plate is disposed above and below the roller table, and based on the lowering of the width in both sides in the width direction from the thermometer and the width central portion extension information from the shape meter, the water cooling device is operated. A method for preventing the generation of an undulating shape of a thick steel plate, wherein the central portion in the width direction of the rolled steel plate is water-cooled to obtain good flatness.