JP2010207824A - Method of manufacturing hot-rolled steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of surely manufacturing hot-rolled steel strips having width ( refer to the target width) in which edge seam marks are included in the part of surplus width in hot-rolling equipment on which a sizing press for performing width press of a steel slab with a pair of press dies having a projected part is installed. <P>SOLUTION: The correlative relationship between the amount of deviation in the thickness direction of a slab hammering position and the amount of the maximum turn-around of the edge seam marks is previously determined for every slab standard including the kind of steel and dimensions of the slab. About that slab, the increment of the amount of the maximum turn-around of the edge seam marks is determined in the case where the amount of the deviation in the thickness direction at the slab hammering position is zero on the basis of the correlative relationship between the amount of the deviation in the thickness direction at the slab hammering position and the amount of the maximum turn-around of the edge seam marks. About the succeeding slab to which width press is applied after that slab, a set surplus width is corrected by adding the increment to the surplus width which is set in the case where the amount of the deviation in the thickness direction at the slab hammering position is zero. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a hot-rolled steel having a width that surely includes an edge seam wrinkle in a surplus width portion in a hot rolling facility provided with a sizing press for width-pressing a steel slab with a pair of press dies having convex portions. The present invention relates to a method of manufacturing a strip.

  As a kind of equipment to adjust the width, before installing a sizing press in the hot rolling line and rolling it with a roughing mill and a finishing mill, a pair of press dies with convex parts is used to move the steel slab in the width direction. Pressing (hereinafter referred to as width pressing) is performed. By doing in this way, the width adjustment amount is increased in the hot rolling process, the width of the slab cast in the continuous casting process is integrated, and the width of the hot-rolled steel strip is made differently.

When a hot-rolled steel strip is manufactured by a hot rolling facility, a linear defect (referred to as an edge seam flaw) extending in the longitudinal direction near the widthwise edge portion may occur. As shown in FIG. 6, the edge seam trough 9 extending in the longitudinal direction has wrinkle-like defects 8 on the side surface of the material to be rolled 7 in the hot rolling process in which the material to be rolled 7 is roughly rolled and finish-rolled. It happens to wrap around. 6A and 6B, which are cross sections in the width direction during rolling, 6 indicates a horizontal roll for rough rolling, and 7 indicates a material 7 to be rolled during rough rolling. Moreover, in FIG.6 (c), 10 showed the upper surface or lower surface of the hot-rolled steel strip. The front and back surfaces of the hot rolled strip 10, Ejjishimu flaw 9 wraparound amount d _e occurs.

  Here, in order to suppress the wrinkle-like defect generated on the side surface of the material to be rolled around the front and back surfaces, a pair of press dies 1 having convex portions is used, as shown in FIGS. 5 (a) and 5 (b). Thus, a method of width-pressing the slab M is disclosed (Patent Documents 1 and 2). Fig.5 (a) is a top view which shows the shape of a pair of press metal mold | die 1 which has a convex part of patent document 1, FIG.5 (b) is XX sectional drawing. In FIG. 5, 2 is an incline inclined surface provided on the entrance side inclined with respect to the slab conveyance direction, 3 is a parallel surface provided in the middle so as to be parallel to the slab conveyance direction, and 4 is inclined with respect to the slab conveyance direction. Reference numeral 5 denotes an output side inclined surface provided on the output side, and reference numeral 5 denotes a convex portion. The convex portion 5 has an isosceles trapezoidal shape, and is formed on the entry side inclined surface 2, the parallel surface 3, and the exit side inclined surface 4. When the slab M is width-pressed by the pair of press dies 1, A recess corresponding to the convex part 5 having an isosceles trapezoidal shape is formed.

The precondition is that when the slab M is width-pressed by the pair of press dies 1, there is no deviation in the thickness direction of the slab hitting position by the press dies. Here, the thickness direction deviation amount δ at the slab hitting position is the vertical difference between the vertical center position 1a of the isosceles trapezoidal convex portion and the slab thickness center O position (FIG. 5B and FIG. 1 (a)).
When there is no deviation in the thickness direction of the slab hitting position, the start positions P and Q of the recesses formed on the side surface of the slab 1 are as shown in FIG. The upper and lower positions are almost the same.

Conventionally, the surplus width b of the hot-rolled steel strip is set on the premise that there is no deviation in the thickness direction of the slab hitting position by the press die, and as shown in FIG. A width W (also referred to as a target width W) of the steel strip 10 is set. That is, the hot rolled strip 10 manufactured, the Ejjishimu flaw wraparound amount d _e of each Ejjishimu flaws measured, is set according to the maximum value of which (referred Ejjishimu flaws maximum wraparound amount). For this reason, when the slab M is width-pressed with a pair of press dies 1 having convex portions, when there is no deviation in the thickness direction of the slab hitting position, an edge seam wrinkle is included in a portion corresponding to the set surplus width b. Therefore, the width W of the hot-rolled steel strip is acceptable.

Japanese Patent Laid-Open No. 10-52701 Japanese Patent Laid-Open No. 2005-34887

However, in actuality, when the slab M is width-pressed with a pair of press dies 1 having convex portions, a deviation in the thickness direction of the slab hitting position occurs, and as a result, the edge seam extends to the inner side of the set surplus width b. There was a problem that the wrinkles went around and the width a as a product could not be secured.
Patent Documents 1 and 2 describe a technique for reducing the maximum amount of edge seam wrinkles of the hot-rolled steel strip 10, but when a deviation in the thickness direction of the slab hitting position occurs, However, there was a problem that the edge seam sword did not take into consideration inward.

  Therefore, when the steel slab is width-pressed with a pair of press dies having convex portions, if the slab hitting position is displaced in the thickness direction, the edge seam exceeds the set surplus width b to the inner product width a. The wrinkles enter and the width W of the hot-rolled steel strip shown in FIG. 7 is rejected, that is, the product width a cannot be secured. When this happens, it is necessary to reapply another slab, set the width W (target width W) of the hot-rolled steel strip again, and manufacture the hot-rolled steel strip. Not only can this be confusing, but it can also lead to delays in delivery.

  The present invention solves the above-mentioned problems of the prior art, and in the hot rolling equipment provided with a sizing press for width-pressing a steel slab with a pair of press dies having convex portions, the edge seam wrinkles are provided with an extra width. It aims at providing the method of manufacturing the hot-rolled steel strip of the width | variety included in a part reliably.

  As a result of earnestly examining the cause of the deviation in the thickness direction of the slab hitting position, the present inventors have found that the slab hitting position of each slab hitting position is changed every time the slab hitting position is finished and rolled together with the slab of almost the same standard after replacing the mold. When the amount of deviation in the thickness direction is different and the deviation in the thickness direction of the slab hitting position occurs, the edge seam 疵 wraps inward from the set margin width, and the maximum amount of edge seam 周 り wrap around increases. Based on this knowledge, we found that the above problem can be solved by obtaining in advance the correlation between the amount of displacement in the thickness direction of the struck position and the maximum amount of edge seam wrinkles for each slab standard including steel grade and slab dimensions. It came to make this invention.

That is, the present invention is as follows.
(1) In a hot rolling facility equipped with a sizing press that presses a steel slab in the width direction with a pair of press dies having convex portions, the slab is width-pressed in the width direction, and then the width is continued. When hot-rolling the pressed slab to obtain a hot-rolled steel strip with a target width obtained by adding the product width to the preset extra width, the vertical distance from the center of the convex part of the press mold to the center of the slab thickness The correlation between the thickness direction deviation amount of the expressed slab hitting position and the edge seam wrinkle maximum wrapping amount is obtained in advance for each slab standard including steel type and slab size. Next, the amount of deviation in the thickness direction of the slab hitting position by the pair of press dies is detected for each slab, and based on the above correlation, the edge seam 疵 maximum wraparound amount when the thickness direction deviation of the slab hitting position is zero For the subsequent slab that determines the increment and presses the width after the slab, the increment is added to the set margin when the displacement in the thickness direction of the slab hitting position is zero, and the set margin is corrected. A method for producing a hot-rolled steel strip that does not include edge seam wrinkles.
(2) The shape of the side surface of the slab is measured during or after the width press to determine the difference in distance from the start position of the recessed portion formed on the side surface of the slab to the edge on the front and back surfaces. The manufacturing method of a hot-rolled steel strip that does not include an edge seam wrinkle according to the above (1), wherein an amount of positional deviation in the thickness direction is detected.
(3) A slit-like light parallel to the thickness direction is applied to the side surface of the slab for scanning, and the slit-like light reflected from the side surface of the slab is imaged with a camera. The method of manufacturing a hot-rolled steel strip that does not include edge seam wrinkles according to (2) above, wherein the shape of the side surface of the slab is measured.

According to the method of the present invention, the displacement amount in the thickness direction of the slab striking position is detected for each slab, and when the slab has a displacement in the thickness direction of the slab striking position, the slab striking is performed for the subsequent slab to be width-pressed after the slab. The increment determined for the slab is added to the margin set when the positional deviation in the thickness direction is zero, and the set margin is corrected.
For this reason, the margin of the trailing slab is obtained by adding the increment determined for the slab before the trailing slab to the margin set when the displacement in the thickness direction of the slab hitting position is zero. The margin is corrected so that the maximum wraparound amount does not fall below the increment.

  Therefore, it is possible to reliably manufacture a hot-rolled steel strip having a width (referred to as a target width) in which the edge seam is included in the extra width portion. After that, the hot-rolled steel strip is fed to the trimming line, and the corrected extra width is cut and removed, so that a hot-rolled steel strip that does not contain edge seams in the product width can be obtained. Even if there is a deviation in the thickness direction, hot-rolled steel strips without edge seam flaws can be shipped without disrupting the steel strip manufacturing process and without delay in delivery.

(A)-(d) is sectional drawing in each hot rolling process which discovered this invention method. It is an example of a characteristic diagram showing the correlation between the thickness direction shift amount δ and Ejjishimu flaw maximum wraparound amount d _max of the slab hitting position. (A) is a block diagram of a slab side surface shape detection apparatus suitable for use in the method of the present invention, and (b) is an explanatory diagram of a detection method using it. It is a block diagram of a suitable hot rolling facility applying the method of the present invention. (A) which shows the shape of a pair of press metal mold | die described in patent document 1, (b) is a top view, (b) is XX sectional drawing. (A), (b) is sectional drawing of the rolling width direction which shows the generation | occurrence | production process of edge seam wrinkles, (c) is a top view which shows the edge seam wrinkles of a hot-rolled steel strip. It is a top view which shows the definition of the target width W of a hot-rolled steel strip.

First, a suitable hot rolling facility to which the present invention method is applied will be described.
FIG. 4 is a configuration diagram of the hot rolling facility 20 described in Patent Document 1, and a sizing press 22 is installed between the heating furnace 21 and the roughing mill 23. The rough rolling mill 23 is composed of four stands each having an edger roll 26 and a rough rolling horizontal roll 27, and the finish rolling mill 24 is composed of seven stands. The width gauge 28 is installed on the entrance / exit side of each facility after the sizing press.

  M denotes a steel slab, and the slab M to be width-pressed may be heated on the heating furnace 21 and extracted onto the transfer table, or may be sent directly from the continuous casting machine onto the transfer table of the hot rolling line. is there. In order to width-press the slab M in the longitudinal direction, the feed amount in the conveyance direction of the slab M is set so as not to exceed the length of the parallel part of the mold, and after sending the slab M by the feed amount, The operation of hitting with a pair of press dies having convex portions is repeated (see FIG. 5A). The hot-rolled steel strip 10 having a predetermined target width and a predetermined finished thickness by hot rolling is wound up by a winder 25 and then sent to a trimming process or the like. However, before application of the method of the present invention, the extra width was set on the assumption that the slab hitting position was not shifted in the plate thickness direction.

  Next, when the slab M is width-pressed with a pair of press dies having convex portions in the hot rolling facility described above, the cause of the displacement in the thickness direction of the slab hitting position has been intensively studied, and the present invention has been achieved. The background is explained. 1 (a) to 1 (d) are cross-sectional views in each of the hot rolling processes that have led to the method of the present invention. Here, the displacement amount in the thickness direction of the slab hitting position is represented by δ, and can be detected by a slab side surface shape detection device as described later (see FIG. 3). In addition, the thickness direction shift | offset | difference of a slab hitting position arises with the installation characteristic of a sizing press at the timing which replaced a pair of press metal mold | die 1 which has a convex part (refer Fig.1 (a)).

Therefore, when the thickness direction shift of the slab hitting position by the pair of press dies 1 occurs due to the equipment characteristics of the sizing press, the start positions P and Q of the recess corresponding to the protrusion are shown in FIG. As described above, the shape is substantially point-symmetric with respect to the slab center 0, and the shape is different between the upper side and the lower side of the slab M.
Such a slab M is supplied to the subsequent rough rolling mill, and the state during rough rolling with the horizontal roll 6 for rough rolling is obtained by subjecting the material to be rolled 7 to rough rolling and finish rolling in FIG. The generation position of the edge seam ridge 9 of the hot-rolled steel strip 10 is shown in FIG.

The bulge shape on both side surfaces of the material 7 to be rolled is formed as shown in FIG. 1 (c), and correspondingly, as shown in FIG. Edge seam ridges 9 that are symmetrical and have different wraparound amounts on the upper and lower sides of the slab M are formed on the front and back surfaces. And it turned out that the amount of wraparound from the part which was struck by the convex part among the upper part and the lower part of the side surface of the slab M increases. In FIG. 1 (d), d ₁ and d ₂ are wraparound amounts of the edge seam ridges produced from the portions hit by being shifted by the convex portions.

As described above, when the slab M is width-pressed with a pair of press dies 1 having a convex portion in a hot rolling facility, the cause of the deviation in the thickness direction of the slab striking position has been intensively studied, and the slab hit by the convex portion When the striking position is shifted to the upper part or the lower part of the side surface of the slab M, the slab center is substantially point-symmetric with respect to the slab center 0, and the amount of wrap around one surface decreases, but the amount of wrap around the other surface increases. As a result, it was understood that the amount of wraparound from the portion hit by being shifted by the convex portion increased compared to the case where there was no deviation in the thickness direction of the slab hitting position. Here, the maximum amount of edge seam wrinkles is d _max .

Then the present inventors, using a hot rolling equipment shown in FIG. 4, was performed in the thickness direction shift amount δ of the slab hitting position, the quantitatively grasp experiments the relationship between Ejjishimu flaw maximum wraparound amount d _max .
(Experimental conditions)
Experimental equipment: The shape of the pair of press dies 1 incorporated in the sizing press 22 of the hot rolling equipment shown in FIG. 4 is equal in the length of the side connecting the convex portions 5 having a trapezoidal cross section between the parallel bases. The shape is an isosceles trapezoid (see FIG. 1A).
Standard of slab M: Steel type = SUS430, slab size = thickness 200-260 mm, slab width 500-2000 mm, heating temperature = 1100-1300 ° C., width press amount = 30-250 mm, slab length = 4500-12500 mm, slab weight = 0 to 32 tons.
(experimental method)
After a slab M is width-pressed by a sizing press 22 with a pair of press dies 1 having an isosceles trapezoidal shape 5, the slab M is once cooled, and three locations in the longitudinal direction of the slab are based on the side shape of the cooled slab. The thickness direction deviation amount δ of the slab hitting position was detected with the average value. Thereafter, the slab M is recharged into the heating furnace and heated, and the slab M is heated in the sizing press 22, and thereafter, the material to be rolled is hot-rolled and hot-rolled steel strip in the same manner as the process material. Then, the amount of edge seam wrap around the obtained hot-rolled steel strip was examined. The result is shown in FIG.
(Experimental result)
The results shown in FIG. 2 show that there is a correlation between the thickness direction deviation amount δ at the slab striking position and the edge seam 疵 maximum wraparound amount d _max for slabs having almost the same slab standard including steel type and slab size. . Curve in FIG. 2 is a surplus width increment determined curve determined so as not to fall below the respective experimental points of Ejjishimu flaw maximum wraparound amount d _max. According to this extra width increase determination curve, when the thickness direction deviation amount of the slab hitting position is detected in the slab, the slab and the slab standard are almost the same, and the subsequent slab to be width-pressed after the slab, An increment to allow the edge seam to be included in the extra width can be determined. For example, by subtracting the reference value 16.2mm of _{d max} in the case where it is detected and the thickness direction shift amount [delta] = 4 mm slab hitting position of the slab, [delta] = [delta] = 0 mm from the value 21.2mm of _{d max} in 4 mm, The increment (= 21.2-16.2 = 5.0 mm) is calculated. Next, for a subsequent slab that is width-pressed after the slab, the amount of deviation in the thickness direction of the slab hitting position is the same as that of the slab, that is, in this example, the amount of deviation in the thickness direction of the slab hitting position is δ = 4 mm. Predictable.

The reason why this can be predicted is that the displacement in the thickness direction of the slab hitting position is caused by the equipment characteristics of the sizing press at the timing when the pair of press dies 1 having convex portions is replaced, and is manufactured after the pair of dies are replaced. This is because the amount of deviation δ in the thickness direction of the slab striking position is different for each chance (an opportunity to finish and roll slabs of almost the same standard together).
As described above, according to the method of the present invention, the correlation between the displacement amount δ in the thickness direction of the slab hitting position and the maximum wraparound amount of the edge seam 疵, for example, as shown in FIG. The thickness direction deviation amount δ of the slab striking position is detected for each slab, and the slab is detected based on the correlation between the thickness direction deviation amount δ of the slab striking position and the edge seam 疵 maximum wraparound amount. The increment of the edge seam 疵 maximum wraparound amount with respect to the case where the displacement amount in the thickness direction of the hit position is zero is determined. Next, for the succeeding slab that is width-pressed after the slab, the increment is added to the surplus set when the displacement amount in the thickness direction of the slab hitting position is zero, and the set surplus width is corrected.

By doing in this way, about a succeeding slab, the hot-rolled steel strip of the target width which added the product width to the corrected surplus width can be obtained.
It is preferable to use a slab side surface shape detecting device as shown in FIG. 3A to detect the thickness direction deviation amount δ of the slab hitting position. This slab side surface shape detecting device applies slit light projecting means 12 that scans the side surface of the slab M by applying slit-shaped light 11 parallel to the thickness direction, and slit-shaped light 11 reflected from the side surface of the slab M. A camera 13 for imaging and an image processing device 14 connected to the camera 13 are provided. According to such a slab side surface shape detection device, based on the image data of the side surface of the slab M obtained by imaging with the camera 13, as shown in FIG. The distances L ₁ and L ₂ from the start position P of the dent corresponding to the convex part at the upper and lower parts to the edge of the side surface are obtained, and the slab hitting position is determined by the difference between the obtained vertical distances (= L ₁ −L ₂ ). The amount of deviation in the thickness direction can be accurately detected online.

(Embodiment 1) As Example 1 of the present invention, a slab that is width-pressed by a pair of press dies having an isosceles trapezoidal convex portion 5 is scanned by applying slit-like light parallel to the thickness direction, and a camera is scanned. Then, the slit-shaped light reflected from the side surface of the slab was imaged, and the side surface shape of the slab was measured based on the image data captured by the camera. As a result, one of the pair of press dies (driving side) was shifted upward by 4 mm while the other (operation side) was shifted downward by 4 mm. Therefore, the thickness direction deviation amount δ = 4 mm at the slab hitting position, and the extra width increment shown in FIG. Based on the determination curve, determine the increment (+ 5mm) of the edge seam 疵 maximum wraparound amount of the slab, and set the remaining width for the subsequent slab that is width-pressed after the slab as there is no deviation in the thickness direction of the slab hitting position. The increment (+5 mm) was added to correct the set margin. Hot rolling to give this extra width was performed to obtain a hot-rolled steel strip.

As a result of sending the obtained hot-rolled steel strip to the trimming process and cutting off and removing the excess width portion, a desired product width free from edge seam wrinkles could be obtained.
(Example 2) As Example 2 of the present invention, the slab width-pressed with a pair of press dies having an isosceles trapezoidal convex portion 5 was cooled, and the side shape was manually measured using a small micrometer. . As a result, one of the pair of press dies (drive side) was shifted downward by 2 mm and the other (operation side) was shifted upward by 2 mm. Based on the determination curve, the increment of the edge seam 疵 maximum wraparound amount of the slab is determined (= 17.5-16.2 = 1.3 mm), and the thickness of the slab hitting position is determined for the subsequent slab that is width-pressed after the slab. The above-mentioned increment of 1.3 mm was added to the extra width set as having no direction shift, and the preset extra width was corrected. Hot rolling to give this extra width was performed.

As a result of sending the obtained hot-rolled steel strip to the trimming process and cutting off and removing the excess width portion, a desired product width free from edge seam wrinkles could be obtained.
(Example 3) As a conventional example, a side shape of a slab was measured in the same manner as in Invention Example 1 for a slab that was subjected to width pressing by a sizing press under the same conditions as in Invention Example 1. As a result, as much as the slab of Invention Example 1, the amount of deviation in the thickness direction of the slab hitting position by the pair of press dies was generated, but as usual, the amount of deviation in the thickness direction of the slab hitting position was not generated. The set margin was left as it was, and hot rolling was performed to give this margin.

  The excess width of the obtained hot-rolled steel strip was cut and removed in the trimming process, but the edge seam wrinkles remained within the product width, so trimming was performed again so that the edge seam wrinkles were not included in the product width in the trimming process. As a result, the production of the hot-rolled steel strip was obstructed and the hot-rolled steel strip was less than the product width, so it had to be transferred to a narrow-width product.

M Slab O Center of slab cross section δ Thickness direction deviation amount d _e Edge seam 回 り wrap amount d _max Edge seam 疵 Maximum wrap amount d ₁ , d ₂ Edge seam 回 り wrap amount P, Q Start position of recess corresponding to convex portion L ₁ , L ₂ Distance from the start position of the recess corresponding to the convex portion to the edge of the side surface W Target width of the hot-rolled steel strip a Product width b Extra width 1 A pair of press dies 1a Top and bottom of the isosceles trapezoidal convex portion Center position in the direction 2 Inlet side inclined surface 3 Parallel surface 4 Outlet side inclined surface 5 Convex portion of the mold 6 Horizontal roll for rough rolling 7 Rolled material 8 Wrinkle defect 9 Edge seam
10 Hot-rolled steel strip
11 Slit light
12 Slit light projection means
13 Camera
14 Image processing device
20 Hot rolling equipment
21 Heating furnace
22 Sizing press
23 Rough rolling mill
24 Finishing mill
25 Winder
26 Edger roll
27 Horizontal roll for rough rolling
28 Width meter

Claims (3)

A slab that has been pressed in the width direction after the width of the slab is pressed in the width direction in a hot rolling facility provided with a sizing press that presses the width of the steel slab in the width direction with a pair of press dies having convex portions. When hot rolling a steel strip with a target width obtained by adding a product width to a preset extra width,
The correlation between the deviation in the thickness direction of the slab striking position expressed by the vertical distance from the center of the convex part to the center of the slab thickness and the maximum wraparound amount of the edge seam 疵 is determined in advance for each slab standard including steel grade and slab size. And
The amount of deviation in the thickness direction of the slab hitting position is detected for each slab, and based on the correlation, the increment of the edge seam 疵 maximum wraparound amount when the thickness direction deviation of the slab hitting position is zero is determined,
For the subsequent slab to be width-pressed after the slab, the increment is added to the set margin when the thickness direction deviation amount at the slab hitting position is zero, and the set margin is corrected. A method for producing a hot-rolled steel strip that does not contain edge seams.   Measure the shape of the side surface of the slab during or after the width press, and based on the shape of the side surface, find the distance from the start position of the recessed portion corresponding to the convex portion above and below the side surface to the edge of the side surface The method for producing a hot-rolled steel strip free from edge seam wrinkles according to claim 1, wherein the amount of deviation in the thickness direction of the slab hitting position is detected from the difference between the obtained vertical distances.   The side surface of the slab is scanned by applying slit-shaped light parallel to the thickness direction, the slit-shaped light reflected from the side surface of the slab is imaged with a camera, and based on the image data captured by the camera, The method of manufacturing a hot-rolled steel strip that does not include an edge seam flaw according to claim 2, wherein the shape of the side surface of the slab is measured.

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