JPH0910837A - Warp straightening of hot rolled stock and device therefor - Google Patents

Abstract

PURPOSE: To surely execute warp straightening of a slab with low cost equipment investment and at low running cost just before hot scarfing by cooling at one side of stock at least just before hot scarfing treatment in hot rolling a hot rolled stock. CONSTITUTION: By stopping a slab 1 at measuring position, by detecting a warped quantity and warped direction of the tip part of slab with a slab warp detecting instrument 1 and by executing water cooling while a solenoid valve 8 at the warped outer peripheral face side is opened for required time only based on the result, a warp of the hot rolled stock 1 is straightened. However, in the case of upward warp, the warped outer face is a rear face, by opening the solenoid valve 8 for rear cooling, rear face cooling of stock is executed with a rear face cooling device 6 and in the case of downward warp, the warped outer face is an upper face, by opening the solenoid valve 9 for upper face cooling, upper face cooling of stock is executed with an upper face cooling device 7. Thus, the warp of hot rolled stock 1 is surely straightened before hot scarfing so as to prevent manual repair.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a warp straightening method and straightening apparatus for hot-rolled material before hot scarf treatment.

[0002]

2. Description of the Related Art A hot rolled material is, for example, a slab. The slab cast in the steelmaking process, especially the surface of the continuous casting slab, has surface cracks that occur during the cooling process of the casting and defects such as inclusions trapped in the surface layer of the slab during the solidification process. If heated and rolled in this state, surface defects of the steel plate, two plates, etc. occur, and there is a problem that quality and yield are reduced. As a countermeasure against this, there is a method of removing 1 mm to 6 mm of the surface of the slab with a hot scarf so as to remove surface defects before the slab is inserted into the furnace.

The hot scarf preheats the surface of the front end of the slab with preheating gas to a temperature at which it reacts with oxygen, and then jets an oxygen jet to the surface to ablate the surface of the slab due to an oxidation reaction. In order to perform delicate control, it is necessary to bring the oxygen blow-out pipe outlet and the surface of the slab close to each other at a constant interval.
However, if there is a warp in the slab, hot scarf processing cannot be performed because it cannot be approached at a constant interval as described above,
The slab needs to be cooled from a high temperature to a low temperature, and a human needs to perform hand care. After that, since the slab is inserted into the heating furnace, there are major disadvantages such as deterioration of the heating furnace unit consumption and increase of maintenance processing cost. As a warp correction technique for steel plates and cast slabs, Japanese Patent Laid-Open No. 5-32364 and Japanese Patent Laid-Open No. 62-32364
No. 34616, for example.

[0004]

[Patent Document 1] Japanese Patent Application Laid-Open No. 5-32364
The gazette discloses a technology for correcting warpage of a thin steel plate by electromagnetic force. However, in the case of a slab, the electromagnetic force required for correction is extremely large because the thickness is thicker than that of a steel strip. However, it is industrially unsuitable for straightening warpage of slabs because it becomes extremely large, enormous equipment cost is required, and a large amount of electric power is required.

Further, JP-A-62-34616 discloses
To prevent warpage due to rolling resistance change due to temperature difference between the upper and lower surfaces of the slab during rolling, measure the upper and lower surface temperatures of the slab after extraction from the heating furnace, and heat the lower temperature side to equalize before rolling. However, if this method is applied, when the temperature of the slab to be heated is high, a large heating device is required due to poor heat input efficiency, resulting in high equipment cost and energy loss due to heating. Running costs are also high.

An object of the present invention is to provide a method and an apparatus for surely correcting warpage of a slab just before a hot scarf with a low cost equipment investment and a very low running cost.

[0007]

The features of the present invention are as follows: (1) When hot-rolling a hot-rolled material, at least one side of the material is cooled before the hot scarf treatment before the heating furnace. Method for straightening hot-rolled material. (2) The method for correcting warpage of a hot-rolled material according to (1), wherein when cooling at least one surface of the hot-rolled material, the one-sided cooling condition is determined based on the warpage information. (3) The method for straightening a hot rolled material according to (1) or (2), wherein one surface is a warped outer peripheral surface. (4) In a warp straightening device provided in front of a hot scarf in a hot rolling process, a warp gauge is provided on the inlet side of the cooling device, and cooling control for controlling cooling conditions of the cooling device based on information of the warp gauge. A warp straightening device for hot-rolled material, which is provided with a device. (5) A warpage gauge is provided inside the cooling device or on the outlet side of the cooling device,
The warp straightening device for hot-rolled material according to (4), further comprising a cooling control device capable of controlling the cooling conditions of the cooling device in consideration of the information of the warpage meter. It is.

[0008]

The present inventor has found that the warp of the hot rolled material is caused by the warp of the slab before the heating furnace, and as a result of various tests for straightening the warp of the slab before the hot scarf, the results show that It was found that warpage can be corrected by using contraction. That is, as shown in FIG. 1 before the hot scarf, if the front end and / or the rear end of the slab is higher than the center in the longitudinal direction of the slab (hereinafter referred to as warpage), the slab 1
If the front end and / or the rear end of the slab is lower than the central part in the longitudinal direction of the slab (hereinafter referred to as warpage), By cooling (for example, water cooling) from the upper surface 3 of the piece 1 (FIG. 1 (b)), it has been found that the slab warpage can be corrected by heat shrinkage on the slab cooling side. Further, in order to correct the warpage relatively quickly, it is desirable to secure a cooling-side surface temperature drop amount of 100 ° C. or more.

Next, an example of the present invention will be described with reference to the drawings. In FIG. 2, the slab 1 is stopped at the measurement position, the warp amount and the warp direction (upward warp or downward warp) of the front end of the slab is detected by the slab warp detection device 10, and the sequencer 11 is based on the result. Then, the motor-operated valve 8 on the outer peripheral surface side of the warp is opened and water-cooled for a necessary time to correct the warp of the hot-rolled material 1. Here, in the case of upward warp, the warped outer peripheral surface is the lower surface, the lower surface cooling motor-operated valve 8 is opened, and the lower surface cooling device 6 cools the lower surface of the material. In the case of downward warp, the warped outer peripheral surface is the upper surface. The upper surface cooling motor-operated valve 9 is opened and the upper surface cooling device 7 cools the upper surface of the material. Further, in determining the cooling time, in addition to the method of uniquely determining the sequencer 11 from the value of the warp detection device 10 as described above, the warp amount during cooling is detected at any time using the warp detection device 12, A cooling control device 13 is provided to cool the warp amount to a target value or less.
A method of controlling with is also possible.

It should be noted that the hot-rolled material may be any material regardless of the material type, such as ultra-low carbon steel (so-called SUL
Steel C), low carbon steel, medium carbon steel, high carbon steel, low alloy steel, high alloy steel and the like, aluminum, aluminum alloy, copper, copper alloy and the like may be used. In the figure, reference numeral 4 is a conveying roll for conveying the cast slab 1, and reference numerals 5 and 5a are hot scarfing devices for performing the ablation of the upper and lower surfaces of the slab 1 whose warpage has been corrected.

[0011]

EXAMPLES Examples of the method of the present invention and comparative examples are shown in Table 1. Slabs of various steels were water-cooled in the hot rolling process by the method shown in FIG. 2 before the hot scarf treatment before the heating furnace. By adopting the example of the present invention, the non-materials of the hot scarf was significantly reduced from 1% to 0.12% in one month rolling.

[0012]

[Table 1]

[0013]

As described above, according to the present invention, since the warp of the hot-rolled material can be reliably corrected before the hot scarf, it is possible to prevent the cold manual maintenance in the off-line, and to heat the material in warm and hot conditions. Since it can be charged into the heating furnace, the heating cost can be greatly reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a relationship between material warpage and cooling.

FIG. 2 is an explanatory diagram showing an example of the present invention.

[Explanation of symbols]

 1 Hot Rolled Material 2 Warp Inner Surface 3 Warp Outer Surface 4 Conveyor Roll 5, 5a Hot Scarfing Device 6 Bottom Cooling Device 7 Top Cooling Device 8 Bottom Cooling Motorized Valve 9 Top Cooling Motorized Valve 10 Cast Fraction Warping Detection Device 11 Sequencer 12 Cast slab warp detection device 13 Cooling control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Nishikawa 5-3 Tokai-cho, Tokai-shi, Aichi New Nippon Steel Co., Ltd. Nagoya Steel Works

Claims (5)

[Claims] 1. When hot rolling a hot rolled material,
A hot-rolled material warp straightening method, characterized in that at least one surface of the material is cooled before a hot scarf treatment in a heating furnace. 2. The method for correcting warpage of a hot-rolled material according to claim 1, wherein when cooling at least one side of the hot-rolled material, the one-sided cooling condition is determined based on the warpage information. 3. The method for straightening a warp of a hot-rolled material according to claim 1, wherein one surface is a warp outer peripheral surface. 4. A warp straightening device provided in front of a hot scarf in a hot rolling process, having a warp gauge on the inlet side of a cooling device, and further controlling cooling conditions of the cooling device based on information of the warp gauge. A warping correction device for hot-rolled material, which is provided with a cooling control device. 5. A warpage meter is provided inside or on the outlet side of the cooling device, and a cooling control device capable of controlling the cooling condition of the cooling device in consideration of the information of the warpage meter is also provided. Item 4. A warp straightening device for hot-rolled material according to item 4.