JPH07290129A - Winding temperature control method for hot rolled steel sheet - Google Patents

Abstract

(57) [Abstract] [Purpose] By making the surface roughness extremely fine, it is possible to perform cooling control that keeps the winding temperature constant, and this cooling control eliminates variations in the material and stabilizes the material. To provide a method for obtaining a hot rolled steel sheet. [Composition] In a winding temperature control method for a hot-rolled steel sheet that is cooled and wound after hot-finish rolling, the surface roughness of the hot-rolled steel sheet after hot-finish rolling is 1.0 to 1.5 µm in Ra display. Adjust and keep the winding temperature constant. The surface roughness of the hot-rolled steel sheet after rolling is adjusted by adjusting the surface roughness of the final stand roll of the hot finish rolling mill by online polishing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a coiling temperature of a hot rolled steel sheet which is cooled and wound after hot finish rolling.

[0002]

2. Description of the Related Art Conventionally, a hot rolling steel strip hot rolled by a hot finishing mill is wound into a product coil by a winding machine, but at a temperature of a hot rolling steel sheet wound by a winding machine. Since a certain winding temperature affects the mechanical properties of the product, a cooling device capable of cooling is provided between the hot finish rolling mill and the winding machine in order to control the winding temperature and the like. ing. Under such a structure, the rolling mill is cooled to about 600 ° C by a cooling device after completion of hot finish rolling and then wound up, but recently, for the purpose of quality improvement and production of new material, 400 ° C. Low-temperature winding is performed in which the material is cooled to a temperature of a certain degree or lower and wound up. However, since the coiling is carried out at a low temperature, there is a problem that the coiling temperature varies greatly and the material is unstable.

To address such problems, Japanese Patent Publication No. 5-76
Japanese Patent No. 374 discloses that the temperature difference at the time of online cooling is reduced to reduce material variations, shape defects, and dimensional inaccuracy. In the method of cooling and heat treating, the surface roughness of the material to be rolled after rolling is adjusted to 10 to 30 μm in Rz display over the vapor film thickness of the cooling medium, and after accelerating oxidation of the new surface after rolling, Disclosed is a cooling control method in an online controlled cooling heat treatment in which a cooling medium is used for cooling.

[0004]

[Problems to be Solved by the Invention]
Japanese Patent No. 6374 aims to reduce the temperature difference during online cooling to reduce material variations, shape defects, and dimensional accuracy defects, and is the same in terms of adjusting the surface roughness of the material to be rolled after rolling. However, the subject and the difference in surface roughness and the means of accelerating and oxidizing the newly-rolled surface for cooling are required. In the present invention, the surface roughness is extremely low, and it is possible to make the winding temperature constant by limiting the fineness to a narrow specific range. No means of accelerating the nascent surface is required.

[0005]

The present invention is different from the one described above, and by making the surface roughness extremely fine, it becomes possible to carry out cooling control for keeping the winding temperature constant, and temperature control by this cooling control is made possible. Accordingly, it is an object of the present invention to provide a method for obtaining a hot-rolled steel sheet having a stable material by eliminating variations in the material. The gist of the invention is as follows: (1) In a winding temperature control method for a hot rolled steel sheet that is cooled and wound after hot finish rolling, the surface roughness of the hot steel sheet after hot finish rolling is expressed in Ra. Is adjusted to 1.0 to 1.5 μm in order to make the winding temperature constant, and a winding temperature control method for hot-rolled steel sheet. (2) The winding temperature of the hot-rolled steel sheet according to claim 1, wherein the surface roughness of the hot-rolled steel sheet after rolling is adjusted by adjusting the roll surface roughness of the final stand roll of the hot finish rolling mill by online polishing. There is a control method.

[0006]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is an overall conceptual diagram showing a hot finish rolling process according to the present invention. As shown in FIG. 1, the slab extracted from the heating furnace 1 is then roughly rolled in the rough rolling mill group 2 and finish rolled in the finish rolling mill group 3 to form a strip. The final stand roll of the finishing rolling mill group 3 is provided with a roll for keeping the surface roughness of the roll constant by an on-line polishing finishing rolling mill 4, and then rolled up through a water injection facility 5 to form a coil 6. Become. In this case, the flatness detecting device 7 is arranged on the exit side of the online finish rolling mill 4 to detect and output the flatness of the hot rolled steel sheet. Further, in the feed forward control device 10, the steel plate temperature at the water injection device inlet side and the winding temperature by the winding thermometer 11 are input by the plate thickness by the finishing outlet side thermometer 8 and the plate thickness gauge 9.

FIG. 2 is a diagram showing the relationship between the winding temperature and the roughness Ra according to the present invention. FIG. 2 shows, for example, a plate thickness of 3.27 m.
In the case of m, the roughness Ra needs to be adjusted to 1.5 μm or less in order to obtain the winding temperature of 400 to 500 ° C. FIG. 3 is a diagram showing the relationship between the steel plate surface roughness Ra and the winding temperature variation according to the present invention. When the surface roughness Ra of the steel sheet is less than 1.0 μm, the winding temperature varies, which is not preferable. Further, when the thickness exceeds 1.5 μm, the variation in the winding temperature rapidly increases, so 1.0
The range was up to 1.5 μm.

Moreover, the range of the coiling temperature of 400 to 500 ° C. corresponds to the transition boiling region, and the coiling temperature difference due to the surface roughness of the steel sheet becomes large. In particular, the cooling of the steel sheet surface is also the point at which the vapor film begins to collapse, which means that its behavior greatly affects the cooling ability. When cooling a hot steel sheet, water accompanied by a boiling phenomenon is usually used as a refrigerant. Therefore, the end temperature of film boiling tends to vary depending on the physical or chemical properties of the heat transfer surface. Therefore, it became clear that the end temperature of film boiling is stabilized by forming a certain regularity on the heat transfer surface, which is relatively regular. That is, these roughness Ra penetrates the vibrating vapor film on the heat transfer surface and comes into direct contact with the refrigerant liquid. as a result,
The film boiling end temperature settles in a narrow range, and the cooling end temperature becomes constant. Therefore, it is effective to provide the surface with regular and optimum surface roughness as a means for achieving uniform cooling. It has been experimentally found that the surface roughness Ra is optimally 1.0 to 1.5 μm described above.

FIG. 4 is a detailed view of the finish rolling mill with online polishing according to the present invention. As shown in FIG. 4, an online polishing device 13 is provided on the surface of the work roll 12, and the surface of the work roll 12 is provided with a desired rough surface condition by the online polishing device 13. And this work roll 1
By separating the plate edge wear removal of No. 2 and the surface roughness control from each other, it becomes possible to freely give a desired surface roughening condition to the work roll surface by the online polishing device 13, and the desired surface roughness of the hot rolled steel plate 14 can be obtained. The rough surface condition of is added.
For that purpose, a light reduction of 1 to 10% is sufficient. Subsequently, the water injection facility 5 is cooled at a desired cooling rate to a desired end temperature. At this time, since a uniform surface roughening condition is given to the surface of the hot rolled steel sheet during cooling, temperature dispersion does not occur in the cooling process, and a flat steel sheet is produced.

[0010]

EXAMPLE In the hot rolling finish rolling process shown in FIG. 1, the final stand roll of the finish rolling mill group is an online polishing finish rolling mill, and the flatness detecting device 7 is provided on the exit side of the online polishing finishing rolling mill 4. Installed, detects the flatness of the hot rolled steel sheet, outputs it, and feedforward controller 1
At 0, the temperature of the inlet side steel plate of the water injection device by the finishing output side thermometer 8, the winding temperature by the winding thermometer 11, the plate thickness by the plate thickness gauge 9, the passage speed in the water injection device by the speed detector, the water injection amount command value, etc. From the results of, the relationship between flatness and heat transfer coefficient, etc. is quantitatively understood. In this way, by determining the water injection amount using the output from the flatness detecting device 7, it was possible to eliminate the fluctuation of the winding temperature due to the change of the flatness and obtain a uniform winding temperature of the hot-rolled steel sheet. . In this case, the plate thickness is 3.27m
m, plate width 880 mm, water inlet device inlet side steel plate temperature 1180
℃, target winding temperature 450 ℃, maximum water injection device passage speed 1
Roughness Ra of 1.3 μm by adding a reduction rate of 5% to the surface of the hot-rolled steel sheet by the online finishing mill with polishing 4 at 000 m / min.
Was granted.

[0011]

As described above, in the method for controlling the coiling temperature of the hot rolled steel sheet according to the present invention, an online polishing finish rolling machine is provided on the inlet side of the cooling device, and the water injection amount in the water injection device is adjusted. As a result, a constant target winding temperature can be obtained, the mechanical properties of the hot-rolled steel sheet product are made uniform, and a great economic effect can be obtained by improving the yield by improving the quality.

[Brief description of drawings]

FIG. 1 is an overall conceptual diagram showing a hot finish rolling process according to the present invention,

FIG. 2 is a diagram showing a relationship between a winding temperature and a roughness Ra according to the present invention,

FIG. 3 is a diagram showing a relationship between a steel plate surface roughness Ra and a winding temperature variation according to the present invention;

FIG. 4 is a detailed view of an online-polishing finish rolling mill according to the present invention.

[Explanation of symbols]

 1 heating furnace 2 rough rolling mill group 3 finishing rolling mill group 4 finishing rolling mill with online polishing 5 water injection equipment 6 coil 7 flatness detection device 8 finishing delivery side thermometer 9 plate thickness gauge 10 feedforward controller 11 winding thermometer 12 Work Roll 13 Online Polishing Device 14 Hot Rolled Steel Sheet

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B21B 37/00 BBM

Claims (2)

[Claims] 1. A method for controlling a winding temperature of a hot rolled steel sheet, which is cooled and wound after hot finish rolling, wherein the surface roughness of the hot rolled steel sheet after hot finish rolling is 1.0 to 1. A winding temperature control method for hot-rolled steel sheet, wherein the winding temperature is adjusted to 5 μm and the winding temperature is kept constant. 2. The winding of the hot-rolled steel sheet according to claim 1, wherein the surface roughness of the hot-rolled steel sheet after rolling is adjusted by adjusting the surface roughness of the final stand roll of the hot finish rolling mill by online polishing. Temperature control method.