JP2006281221A - Method for preventing camber of u-shape sheet pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preventing method of the camber of a U-shape sheet pile by which a special inverting device and restraining device are not required in the case the U-shape sheet pile is rolled in the inverted U-shape position. <P>SOLUTION: This method has a stage where a long size U-shape sheet pile 1 is formed by hot finish rolling in the inverted U-shape position, a stage where the inside of the web part 2 of the long size sheet pile 1 is cooled as it is in the inverted U-shape position and a stage where the long size U-shape sheet pile 1 is divided into a prescribed length after or during cooling the inside of the web part 2 of the long size U-shape sheet pile 1. The cooling range is a range the length of which is ≥25% of the length of a U-shape sheet pile 1 after dividing and which includes the neighborhood of the middle of the U-shape sheet pile 1 after dividing. Further, weak cooling is performed to the inside of the web part 2 at the temperature drop of <80°C and the cooling rate of ≤5°C/s. Cooling water is sprayed from spray nozzles 8 toward the inside of the web part 2. The ranges where the cooling water jetted from a plurality of sprays is collided are away from each other. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for preventing warpage of a U-shaped steel sheet pile, and more particularly to a method for preventing warpage of a U-shaped steel sheet pile after hot finish rolling.

FIG. 3 is a sectional view showing a general shape of a U-shaped steel sheet pile. In FIG. 3, the U-shaped steel sheet pile 1 is composed of a horizontal web portion 2, a pair of flange portions 3 facing each other in a substantially C shape, and a claw portion 4 installed at the tip of each flange portion 3. Has been.
The manufacturing process of the U-shaped steel sheet pile 1 is generally formed into a long shape by heating the raw material, rough rolling in a roughing mill, intermediate rolling in one or more intermediate rolling mills, and finish rolling in a finishing mill, Then, it has the process of dividing | segmenting into predetermined product length in a sawing machine, and the process of cooling to substantially normal temperature in a cooling floor after a division | segmentation.
At this time, since the thickness of the web part 2 is thicker than that of the flange part 3, the temperature of the web part 2 is higher than that of the flange part 3 immediately after the end of rolling, and the temperature difference sometimes becomes 100 ° C. or more.

4 to 6 illustrate warpage after finish rolling of the U-shaped steel sheet pile, FIG. 4 is a temperature change diagram showing the temperature history of the web portion and the flange portion, FIG. 5 is a schematic diagram showing the warpage, and FIG. It is a schematic diagram which shows downward curvature.
4 to 6, it is general that the finish rolling is finished at a temperature equal to or higher than the transformation point for both the web portion 2 and the flange portion 3.
After finishing rolling, since the thin flange portion 3 is more easily cooled, it is transformed before the web portion 2 (time a in FIG. 4). Then, the temperature of the flange portion 3 is slowed down by transformation heat generation and transformation expansion occurs, so that “upward warping” occurs in which the web portion 2 is inside the radius of curvature and the flange portion 3 claw portion 4 is outside the radius of curvature ( (See FIG. 5).

Thereafter, when the transformation starts even in the thick web portion 2, the temperature decrease is slowed by the transformation heat generation, and sometimes the temperature rises (time b in FIG. 4). On the other hand, since the temperature of the flange portion 3 is lowered after the transformation is completed, the temperature of the flange portion 3 is greatly reduced as compared with the web portion 2, and the heat shrinks greatly.
Then, “downward warping” occurs in which the web portion 2 is outside the curvature radius and the claw portion 4 of the flange portion 3 is inside the curvature radius (see FIG. 6).

  Further, when the transformation of the web part 2 is completed, the heat diffusion in the cross section of the U-shaped steel sheet pile 1 and the heat radiation to the surroundings progress, and when the temperature difference between the web part 2 and the flange part 3 is reduced to some extent, the downward warping is reduced. In the end, however, the warping occurs (time c in FIG. 4).

When such upward warping or downward warping (hereinafter sometimes referred to as “warping” in some cases) occurs, the warped portion collides with the apron 9 or the table roll 10 and deforms, and this portion does not become a product. In addition to lowering the temperature, problems such as damage to the equipment also occur (see FIG. 6).
In addition, the conveyance capacity is lowered and the productivity is remarkably lowered. In particular, when a downward warp occurs, as shown in FIG. 6, the tip 1 t and the tail end 1 b of the U-shaped steel sheet pile 1 ride on the apron 9 of the transport table and do not come into contact with the table roll 10. Become. As a result, as described above, the temperature difference between the web portion 2 and the flange portion 3 becomes small and the downward warping becomes small, so that it must be cooled on the spot and waited.

The following inventions have been proposed as a technique for eliminating or reducing such downward warping. For example, the temperature of the web part 2 is cooled to the ferrite transformation temperature Ar3 or lower before the final finish rolling, and the temperature difference between the web part 2 and the flange part 3 is set within 50 ° C. There is a method in which finish rolling is performed in a posture, and then cooling is performed in a U-shaped posture by reversing the U-shaped steel sheet pile (for example, see Patent Document 1).
In addition, after finishing rolling in an inverted U-shaped posture, immediately after the U-shaped steel sheet pile is reversed, the leading end portion and the trailing end portion are constrained in the U-shaped posture, and the temperature difference between the web portion 2 and the flange portion 3. There is also a method of performing forced cooling until the temperature reaches 80 ° C. or lower (see, for example, Patent Document 2).
JP 58-215203 A (page 3, FIG. 6) Japanese Patent Laid-Open No. 63-220917 (page 3, FIG. 1)

However, the invention disclosed in Patent Document 1 requires a reversing device for this purpose because a U-shaped posture is required after finishing rolling in an inverted U-shaped posture in order to prevent downward warping. There was a problem that a large equipment cost was required. Moreover, since it conveyed with a U-shaped attitude | position, there existed a problem that a wrinkle might generate | occur | produce on the surface of a web part, when contacting with a table roll.
In addition, the invention disclosed in Patent Document 2 is forcibly cooled after restraining the front end portion and the rear end portion after finishing rolling is completed, so that the restraint device for this purpose (in the production line of the U-shaped steel sheet pile) ) Is newly required, and a long cooling device is required for cooling in the long (same as before division), and there is a problem that enormous equipment costs are required. In addition, it takes time to reverse and restrain, and there is a problem that productivity is remarkably hindered.

  The present invention is for solving the above-mentioned problem, and is a method for preventing warpage of a U-shaped steel sheet pile that does not require a special reversing device or restraining device in rolling a U-shaped steel sheet pile in an inverted U-shaped posture. The purpose is to provide.

(1) The method for preventing warpage of a U-shaped steel sheet pile according to the present invention, the inner surface of the web of a U-shaped steel sheet pile in an inverted U-shaped posture subjected to hot finish rolling is cooled by a spray cooling device,
The spray cooling is performed while the conveyance speed before and after the stop for dividing the U-shaped steel sheet pile is 1 m / second or less.

  (2) Moreover, in the said cooling process, the cooling range of the inner surface of the web part of the said U-shaped steel sheet pile is 25% or more of the length of the U-shaped steel sheet pile after the division, and after the division. It is the range including the center vicinity of a U-shaped steel sheet pile.

  (3) Further, in the cooling step, the inner surface of the web portion of the U-shaped steel sheet pile causes a temperature drop within 80 ° C. and is cooled at a cooling rate of 5 ° C./second or less. To do.

  (4) Moreover, in the said cooling process, a cooling fluid is sprayed toward the inner surface of the web part of the said U-shaped steel sheet pile.

  (5) Further, in the cooling step, the ranges of the cooling liquid sprayed from a plurality of sprays that collide with the inner surface of the web portion of the U-shaped steel sheet pile are separated from each other.

Therefore, the warpage prevention method for the U-shaped steel sheet pile according to the present invention has the following effects.
(I) Since the inner surface of the web portion of the U-shaped steel sheet pile is cooled, downward warping can be prevented. Further, in parallel with the division of the U-shaped steel sheet pile, or to cool the inner surface of the web part at a time including the time of the low speed conveyance before and after the division (for example, conveyance speed of 1 m / second or less), the productivity is improved. Significant improvement can be achieved.
(Ii) The cooling range of the inner surface of the web portion of the U-shaped steel sheet pile is 25% or more of the length of the U-shaped steel sheet pile after the division, and the vicinity of the center of the U-shaped steel sheet pile after the division. Therefore, desired cooling and prevention of warping can be achieved with a minimum cooling range, that is, a cooling facility with a minimum scale.

(Iii) Moreover, since the temperature falls within 80 ° C. and is weakly cooled at a cooling rate of 5 ° C./second or less, desired steel properties can be obtained.
(Iv) Further, since the coolant is sprayed toward the inner surface of the web portion of the U-shaped steel sheet pile, the flange portion is not unnecessarily cooled, and desired steel material characteristics are obtained throughout the U-shaped steel sheet pile. be able to.

(V) In addition, since the ranges of collision of the cooling liquid sprayed from the plurality of sprays are separated from each other, there is no local supercooling and no quenching is performed locally.
(Vi) Furthermore, a cooling device before finish rolling, a reversing device after finish rolling, and a restraint device are unnecessary, and an increase in equipment cost can be prevented.

  FIG. 1 is an apparatus configuration diagram schematically showing a part of a rolling line for carrying out a method for preventing warpage of a U-shaped steel sheet pile according to an embodiment of the present invention. In FIG. 1, a dividing machine 12 is arranged on the downstream side (right side in the figure) of the finishing mill 11, and a plurality of aprons 9 (see FIG. 2) and table rolls are disposed between the finishing mill 11 and the dividing machine 12. 10 forms a transfer line. A plurality of (for example, a total of 20) spray nozzles 8 are installed in a row along the conveyance direction of the conveyance line (similar to the left-right symmetry axis of the U-shaped steel sheet pile 1) below the apron 9.

  2A and 2B are perspective perspective views and a transverse cross-sectional view schematically showing the cooling of the U-shaped steel sheet pile in the method for preventing warpage of the U-shaped steel sheet pile according to the embodiment of the present invention. In FIG. 2, the U-shaped steel sheet pile 1 is composed of a horizontal web portion 2, a pair of flange portions 3 that face each other in a substantially C shape, and a claw portion 4 installed at the tip of each flange portion 3. Has been. Then, the U-shaped steel sheet pile 1 is finish-rolled in an inverted U-shaped posture, remains in that posture, and remains long and the inner surface of the web portion 2 (the surface sandwiched between the flange portions 3 is referred to as an “inner surface”). The coolant is ejected toward the head.

  At this time, the cooling liquid is sprayed from each spray nozzle 8 at a predetermined flow rate at a predetermined injection angle (for example, 50 °) in a conical shape or an elliptical conical shape. An elliptical coolant injection range 7 is formed. Moreover, since the injected cooling liquid falls immediately after colliding with the inner surface of the web portion 2 and is less scattered to the surroundings, it is possible to cool only the web portion 2 without cooling the flange portion 3. is there.

  In addition, when the space below the apron 9 is limited and a large number of spray nozzles 8 cannot be installed in a wide range, the length of the range in which the U-shaped steel sheet pile 1 is cooled is limited. At this time, it is preferable to set the length of the cooled range to a range of 25% or more (L / 4) including the vicinity of the center of the divided product length (L) and to cool for a certain amount of time instead. It is. This is because the effect of preventing warping due to cooling is greater near the center than at the end. When the cooling range is less than 25%, the effect of preventing warpage is almost lost.

That is, the warpage preventing method for the U-shaped steel sheet pile according to the embodiment of the present invention is as follows.
Forming a U-shaped steel sheet pile by hot finish rolling in an inverted U-shape;
Cooling the inner surface of the web of the U-shaped steel sheet pile in an inverted U-shape,
Dividing the U-shaped steel sheet pile into a predetermined length after or while cooling the inner surface of the web of the U-shaped steel sheet pile.
The cooling process is not limited to the time when the U-shaped steel sheet pile is completely stopped. When the conveyance speed is reduced to a very low speed immediately before the dividing process (for example, for 1 m / sec or less). ) Or after the dividing step is completed, and also during a very low speed (for example, 1 m / second or less) during which the conveyance speed has not yet increased.
Therefore, since the cooling step is performed in parallel with the dividing step, the time of about 5 to 10 seconds required for the dividing step is effectively used, and the total production capacity of the production line can be further increased.

  For example, in the case of four cut pieces having a product length of 12 m, the first cut is first cooled when the tip crop is divided. That is, the range of 3 m or more from the position of 4.5 m or less from the divider 12 to the position of 7.5 m or more, which is a range of 25% or more including the center of the first cut, is cooled. During this time, the second to fourth cuts are not cooled. Then, when the cooling of the first cut is finished and the division of the tip crop is finished, the U-shaped steel sheet pile 1 (long material) is conveyed to divide the first cut and the second cut. That is, in parallel with the division, a range of 25 m or more including the center of the second cut is cooled from a position of 4.5 m or less from the divider 12 to a position of 7.5 m or more. During this time, the third cut and the fourth cut are not cooled. Further, similarly, the third cut and the fourth cut are cooled and divided, and finally the tail end crop is divided.

Further, when the spray nozzle 8 is installed in a wide range in the transport direction of the transport line, for example, in the case of the above example, the first cut and the second cut are simultaneously performed while the tip crop is being divided. It may be cooled. That is, the range of 15 m or more from the position of 4.5 m or less to the position of 19.5 m or more from the divider 12 may be cooled. Then, the second cut and the third cut may be simultaneously cooled while the first cut and the second cut are divided. That is, since the cooling time after the second cut can be secured approximately twice as long as that of the first cut, weak cooling can be achieved accordingly.
Furthermore, when the installation range of the spray nozzle 8 is wider, or when the product length after the division is short, it may be simultaneously cooled over three or more cuts.

  Further, the cooling of the U-shaped steel sheet pile 1 is preferably cooling that causes a temperature drop within 80 ° C. If it is higher than 80 ° C., depending on the steel components, it will burn, and mechanical properties such as elongation will not be satisfied. The cooling rate is preferably within 5 ° C./second. When the temperature is higher than 5 ° C./second, depending on the steel components, baking occurs and mechanical properties such as elongation are not satisfied.

  In addition, it is preferable to cool by spraying the coolant so that the coolant spray range 7 below the inner surface of the web portion 2 does not wrap (do not overlap). This is because if cooling is performed in a state where the conveyance of the U-shaped steel sheet pile 1 is stopped, supercooling occurs where the coolant injection range 7 wraps, and the product material is deteriorated.

[Example]
Table 1 shows cooling conditions and cooling results in the examples of the present invention. In Table 1, the manufactured U-shaped steel sheet pile 1 has a web portion 2 having a thickness of 24 mm, a flange portion 3 having a thickness of 11 mm, an effective width 5 of 600 mm, and an effective height 6 of 200 mm. The cooling condition is that a total of 20 spray nozzles 8 arranged in a line along the conveying direction below the apron 9, and from each spray nozzle 8, a coolant is flowed at a flow rate of 40 liters / minute and an injection angle of 50 °. It is sprayed in a shape.
At this time, the jetted cooling liquid falls immediately after colliding with the web part 2 and is less scattered to the surroundings, so that only the web part 2 is cooled without cooling the flange part 3. Table 1 shows the necessary equipment, the ratio of the web cooling unit, the temperature drop due to spray cooling, and the cooling rate as the cooling conditions, comparing the production efficiency as a cooling result.

  In Comparative Example 1, cooling is performed before finish rolling, and after finishing rolling, the U-shaped posture is reversed, and then restrained and cooling is performed. In cooling before finish rolling, it takes the longest time for cooling to lower the temperature of the web part 2 to the ferrite transformation temperature Ar3 or lower, and the production efficiency is as low as 70 ton / hour.

  In Comparative Example 2, the cooling is not performed before the finish rolling, but is constrained and cooled after being reversed to the U-shaped posture after the finish rolling (see Patent Document 2). It takes a long time for handling because the product is inverted and cooled by being restrained after waiting for finish rolling to finish. For this reason, the production efficiency is as low as 80 ton / hour.

  In Comparative Example 3, finish rolling is performed in an inverted U-shaped posture, and cooling is not performed before and after that. At this time, downward warping occurred after finish rolling, the conveyance became impossible, and standby was performed on the line, so that the production efficiency was the lowest at 60 ton / hour.

Example 1 is the technology of the present invention, and cooling before finish rolling is not performed, and after finishing rolling in an inverted U-shaped posture is completed, it is conveyed to the divider 12 without changing the inverted U-shaped posture and stopped. During the division work, the product was cooled at 40 ° C. at a cooling rate of 5 ° C./s in the range of 25% of the product length (L / 4) near the center of the product length (L). is there.
At this time, the cooling device upstream of the finish rolling mill 11, the reversing device downstream of the finish rolling mill 11, and the restraining device are no longer necessary, so that the equipment cost can be greatly reduced.

In addition, since the web part is cooled by 40 ° C. within the range of 25% of the product length after the division including the vicinity of the center of the product after the division, the downward warping of the cooling part is reduced, and the web part is reduced below the product length. Warpage has also been reduced, and the time during which conveyance becomes impossible due to downward warping has been shortened. Furthermore, there is no time for cooling before finishing rolling, inversion and restraint after finishing rolling, and cooling is performed in parallel with the dividing operation in a stopped state during the dividing operation after finishing rolling. , Time is used effectively, and the production efficiency is improved to 100 ton / hour.
Moreover, since the temperature drop of the cooling liquid injection range 7 of the web part 2 was 40 ° C. and the cooling rate was 5 ° C./sec. The same material as the shape steel sheet pile was obtained.

Example 2 does not perform cooling before finish rolling, and after finishing rolling in an inverted U-shaped posture, transports it to the divider 12 without changing the inverted U-shaped posture, and stops and performs the dividing operation. In the meantime, the vicinity of the center of the product length (L) was cooled at 80 ° C. at a cooling rate of 5 ° C./second in the range of 25% of the product length (L / 4). Compared with Example 1, the temperature drop is increased.
Since the web part is cooled at 80 ° C., the downward warping of the cooling part is eliminated, the downward warping with respect to the product length is further reduced from that in Example 1, and the time during which the conveyance becomes impossible due to downward warping is further shorter than in Example 1. The production efficiency is improved to 110 ton / hour.
Moreover, since the temperature drop of the cooling part of the web part was set to 80 ° C. and the cooling rate was 5 ° C./second, the cooling of the U-shaped steel sheet pile manufactured in the past did not occur during cooling. The same material was obtained. In addition, since it is the same equipment as Example 1, equipment cost is reduced significantly.

In Example 3, the cooling before finish rolling is not performed, and after finishing rolling in an inverted U-shaped posture, it is conveyed to the dividing machine 12 without changing the inverted U-shaped posture, and is stopped and divided. In the meantime, the range (0.8 × L) of 80% of the product length near the center of the product length (L) was cooled at 80 ° C. at a cooling rate of 5 ° C./second.
Since the web portion is cooled at 80 ° C. in the range of 80% of the product length in the vicinity of the center of the product length, the lower warp after finish rolling is eliminated over the entire length, and the time during which it becomes impossible to convey due to the lower warp lost. For this reason, the production efficiency is improved to 120 ton / hour.
Moreover, since the temperature drop of the cooling part of the web part was set to 80 ° C. and the cooling rate was 5 ° C./second, the cooling of the U-shaped steel sheet pile manufactured in the past did not occur during cooling. The same material was obtained. In addition, since it is the same equipment as Example 1 and 2, equipment cost is reduced significantly.

In Example 4, cooling is not performed before finish rolling, and after finishing rolling is finished in an inverted U-shaped posture, it is transported to the dividing machine 12 without changing the inverted U-shaped posture, and is stopped while being divided. Further, a range of 15% of the product length near the center of the product length (L) was cooled at 40 ° C. at a cooling rate of 5 ° C./second.
Since the web portion having a length of 15% near the center of the product length is cooled at a temperature drop of 40 ° C., the lower warpage of the cooling portion is reduced, the downward warpage with respect to the product length is also reduced, and the time during which the conveyance due to the downward warp becomes impossible. The production efficiency was 85 ton / hour.
Moreover, since the amount of temperature drop of the cooling part of the web part was set to 80 ° C. and the cooling rate was 5 ° C./second, the U-shaped steel sheet pile manufactured in the past was not fired during cooling. The same material was obtained. In addition, since it is the same equipment as Example 1, equipment cost is reduced significantly.

In Example 5, cooling before finish rolling is not performed, and after finishing rolling in an inverted U-shaped posture is completed, the workpiece is transported to the dividing machine 12 without changing the inverted U-shaped posture, and stopped to perform a dividing operation. In the meantime, a range (L / 4) of 25% of the product length from the tip of the product length (L) was cooled at 40 ° C. at a cooling rate of 5 ° C./second.
Since the web part 25% longer than the tip of the product length is cooled at a temperature drop of 40 ° C., the warpage of the cooling part is reduced, the downward warp to the product length is also reduced, and the time during which the conveyance due to the downward warp becomes impossible The production efficiency was 85 ton / hour.

  As described above, the U-shaped steel sheet pile warpage prevention method of the present invention can be widely used as a warpage prevention method for various sizes of U-shaped steel sheet piles because a desired quality and high production efficiency can be obtained without requiring a special device. can do.

The apparatus block diagram which shows typically a part of rolling line which implements the curvature prevention method of the U-shaped steel sheet pile which concerns on embodiment of this invention. The perspective perspective view and cross-sectional view which show typically the mode of cooling of a U-shaped steel sheet pile in the curvature prevention method of the U-shaped steel sheet pile which concerns on embodiment of this invention. Sectional drawing which shows the general shape of a U-shaped steel sheet pile. The temperature change figure which shows the temperature history after the finish rolling of a U-shaped steel sheet pile. The schematic diagram which shows the curvature after the finish rolling of a U-shaped steel sheet pile. The schematic diagram which shows the downward curvature after the finish rolling of a U-shaped steel sheet pile.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 U-shaped steel sheet pile 1b Tail end 1t Tip 2 Web part 3 Flange part 4 Claw part 5 Effective width 6 Effective height 7 Coolant injection range 8 Spray nozzle 9 Apron 10 Table roll 11 Finishing mill 12 Divider

Claims (5)

A method for preventing warpage of a U-shaped steel sheet pile that cools an inner surface of a web of a U-shaped steel sheet pile in an inverted U-shaped posture subjected to hot finish rolling, using a spray cooling device,
A method for preventing warpage of a U-shaped steel sheet pile, wherein the spray cooling is performed while the U-shaped steel sheet pile is stopped for division or before and after the conveyance speed is 1 m / second or less.   In the cooling step, the cooling range of the inner surface of the web of the U-shaped steel sheet pile is 25% or more of the length of the U-shaped steel sheet pile after the division, and the center of the U-shaped steel sheet pile after the division. The method for preventing warpage of a U-shaped steel sheet pile according to claim 1, wherein the method includes a range including the vicinity.   The inner surface of the web of the U-shaped steel sheet pile causes a temperature drop within 80 ° C. and is cooled at a cooling rate of 5 ° C./second or less in the cooling step. The method for preventing warping of the U-shaped steel sheet pile as described.   The method for preventing warpage of a U-shaped steel sheet pile according to any one of claims 1 to 3, wherein in the cooling step, a coolant is sprayed toward an inner surface of the web of the U-shaped steel sheet pile. 5. The U-shaped steel sheet pile according to claim 4, wherein the ranges of the cooling liquid sprayed from a plurality of sprays that collide with the inner surface of the web of the U-shaped steel sheet pile are separated from each other. Warpage prevention method.

Images