JP2007175719A - Method for manufacturing steel sheet pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a steel sheet pile which is excellent in productivity. <P>SOLUTION: When manufacturing the steel sheet pile which is made into a product size by hot-sawing after finish rolling, the product length of the steel sheet pile is compared with an interval between table rollers of a conveying line used for conveying the steel sheet pile. When the product length of the steel sheet pile is not longer than n-times the interval between the table rollers, the cooling rate of the web after the finish rolling of the steel sheet pile is previously determined and component design is performed so that the Ar<SB>3</SB>transformation completed temperature of the web in the cooling rate is in the vicinity of the sawing temperature in the hot-sawing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a steel sheet pile that is hot-sawed to a predetermined size after finish rolling.

  The steel sheet pile is roughly rolled into slabs, blooms or billets, finish-rolled into a predetermined cross-sectional shape, cut into a desired length, and then conveyed and shipped on a conveying line having a plurality of table rollers.

  In order to improve the productivity of steel sheet pile manufacturing, the steel sheet pile after finish rolling is quickly cut into product length by hot sawing, transported to the transfer line, and the production line from the finish rolling mill to the transfer line is established. It is desirable to use it continuously.

  Steel sheet piles may cause troubles in transportation due to deformation in the cooling process after finish rolling. Depending on the product dimensions, waiting time is required before hot sawing or after hot sawing. Decreases.

That is, as shown in FIG. 3, the steel sheet pile 1 has a thickness of the web 2 thicker than that of the flange 3 having the joint 4 at the end in order to ensure a section modulus. , The cooling rate of the two is different, and due to the difference in cooling rate, the thin flange 3 is first transformed (Ar ₃ transformation), and the flange 3 undergoes transformation expansion to cause “upward warping”, and then the web. 2 undergoes transformation (Ar ₃ transformation), the web 2 undergoes transformation expansion and “downward warping”, and finally “upward warping” caused by a difference in the plate thickness between the web 2 and the flange 3 occurs.

  When steel sheet piles are `` down-warped '', the steel sheet piles are in the shape of bows that touch both ends in the longitudinal direction to the conveyance line.If the steel sheet piles are short, the number of table roller supports is reduced. It is desirable to avoid conveying the tip in the “downward warp” state because the tip easily enters the gap between the table rollers and becomes impossible to convey.

  Therefore, if the steel sheet pile is short, after the transformation of the web, perform the hot sawing after the downward warpage is eliminated, or perform the hot sawing before the completion of the transformation of the web and eliminate the downward warping, I do. In any case, if the time until the transformation of the web is completed is long, continuous use of the production line is impaired and productivity is lowered.

  In the former case, it is necessary to wait for a long time before hot cutting, the continuity of finish rolling is impaired, and the cutting speed of hot cutting is also reduced. In the latter case, after the hot sawing, it is necessary to wait for the conveyance until the downward warping is eliminated, the continuity of the hot sawing is lost, and the productivity is remarkably lowered.

Patent Document 1 relates to a cooling method after rolling a U-shaped steel sheet pile, and describes that the warpage in a flange or a web is restrained, heated or cooled in order to reduce the warpage.
JP 55-92225 A

  However, the method described in Patent Document 1 requires a jig to be constrained and a cooling device, so that the addition of equipment is large, the adjustment of operation conditions is complicated, and the productivity is lowered.

  Then, an object of this invention is to provide the manufacturing method of the steel sheet pile which is excellent in productivity even if it is a short product dimension.

The object of the present invention can be achieved by the following means.
1. When manufacturing a steel sheet pile having a product size by hot sawing after finish rolling, the ingredients are set so that the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile becomes the sawing temperature of the hot sawing. A manufacturing method of a steel sheet pile characterized by performing design.
2.1. A method for manufacturing a steel sheet pile according to 2.1, wherein the hot sawing is performed when the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile has been reached.
The steel sheet pile manufacturing method according to 3.1 and 2, wherein cooling is performed so that the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile is completed at the hot sawing position. Manufacturing method of sheet pile.
4.1 In the manufacturing method of the steel sheet pile according to any one of 1 to ₃ , the components are designed so that the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile becomes the sawing temperature of the hot sawing. At this time, the product length of the steel sheet pile is compared with the distance between the table rollers of the conveyance line used for conveying the steel sheet pile, and it is determined whether the steel sheet pile product after the hot cutting can be conveyed on the table roller of the conveyance line. And when it becomes impossible to convey, the component design is performed so that the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile is close to the cutting temperature of the hot cutting. Production method.

  According to the present invention, since the hot sawing is performed immediately after the web transformation is completed, the stage where the web undergoes transformation expansion and shifts from the “downward warp” shape to the “upward warp”, that is, the “downward warp” occurs. Since it conveys immediately after canceling | dissolving, a steel sheet pile will pass continuously in each process from finish rolling to conveyance, and it becomes possible to improve productivity.

In the present invention, when a steel sheet pile having a product size is manufactured by hot sawing after finish rolling, the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile is equal to the sawing temperature of the hot sawing. It is the manufacturing method of the steel sheet pile characterized by performing component design so that it may become.
In the present invention, the relationship between the sawing temperature and the Ar ₃ transformation end temperature may be adjusted within a range that does not reduce the productivity, and the sawing temperature ± 20 ° C. is defined as the sawing temperature.

Since the component design is such that the Ar ₃ transformation completion temperature of the web after finish rolling becomes the sawing temperature ± 20 ° C. of the hot sawing, the hot sawing of the steel sheet pile after finish rolling is finished. Ar ₃ transformation completion temperature of the web after rolling can be set, and even when the Ar ₃ transformation of the web is not completed at the hot sawing position, the hot sawing can be started in a short waiting time. Become.

Further, even when the Ar ₃ transformation completion temperature of the web after the finish rolling of the steel sheet pile is not completed at the hot sawing position, the web sheet is made to reach the Ar ₃ transformation completion temperature of the steel sheet pile web slightly. The above-mentioned hot sawing can be performed by cooling.

Furthermore, in the present invention, when the component design is performed so that the Ar ₃ transformation completion temperature of the web after the finish rolling of the steel sheet pile becomes the cutting temperature of the hot cutting, the product length of the steel sheet pile, Compare the distance between the table rollers of the conveying line used for conveying the sheet pile, and determine whether the steel sheet pile product after hot cutting can be conveyed on the table roller of the conveying line. The steel sheet pile manufacturing method is characterized in that the component design is performed so that the Ar ₃ transformation completion temperature of the web after finish rolling is close to the cutting temperature of the hot cutting.
Hereinafter, the present invention will be described in more detail.

  The present invention compares the product length of the steel sheet pile with the distance between the table rollers in the conveyance line when manufacturing the steel sheet pile, and determines whether or not the conveyance by the table roller is hindered when the product is warped (step) 1).

  Fig. 1 shows the case where the product length of the steel sheet pile is such that when the downward warp occurs, the downward warp is corrected or reduced by its own weight (hereinafter, long), and Fig. 2 shows the case where the product is not corrected or reduced. FIG. 3 is an explanatory diagram schematically showing how the conveyance is affected by the distance between the table rollers in the conveyance line in the length (hereinafter, short).

  When the conveyance line of the steel sheet pile 1 has the table roller 5 and the guide plate 6 between the rollers (FIG. 1 (A), FIG. 2 (A)), the conveyance failure of the steel sheet pile 1 At the time of “downward warping”, the steel sheet pile 1 rides on the guide plate 6, and the table roller 5 idles in the direction of the arrow b, thereby making it impossible to convey.

  Moreover, when the conveyance line of the steel sheet pile 1 is comprised only by the table roller 5 (FIG. 1 (B), FIG. 2 (B)), the front-end | tip part of a steel sheet pile is at the time of the "down curvature" of the steel sheet pile 1 It interferes with the table roller 5 and cannot be conveyed.

  1 (A) and 1 (B), when the “downward warp” of the steel sheet pile 1 is large, the conveyance becomes impossible. However, because the product length of the steel sheet pile 1 is long, due to the deflection due to its own weight indicated by the arrow a. The state where the conveyance becomes impossible is avoided. Accordingly, since the “downward warp” amount is corrected or reduced by the deflection due to its own weight, it is acceptable even if the steel sheet pile product length is shorter than that when it is short.

  FIG. 2 is an explanation when the steel sheet pile product length is short, and FIG. 2 (A) is a case where the conveying line of the steel sheet pile 1 has a table roller 5 and a guide plate 6 between the rollers 5. A case where the steel sheet pile 1 rides on the guide plate 6 when the steel sheet pile 1 is “down-warped” and the table roller 5 is idled and cannot be conveyed.

  FIG. 2 (B) shows that when the conveying line of the steel sheet pile 1 is composed of only the table roller 5, the tip of the steel sheet pile 1 interferes with the table roller 5 when the steel sheet pile 1 “warps”. This indicates the case where conveyance is impossible.

When the steel sheet pile product length is short, the inability to convey is eased when the steel sheet pile is long. Deflection due to its own weight indicated by arrow a does not occur, so that the Ar ₃ transformation of the web after finish rolling of the steel sheet pile is not completed. When hot sawing is performed, conveyance becomes impossible.

That is, in the present invention, when the component design is performed so that the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile becomes the cutting temperature of the hot cutting, the product length of the steel sheet pile and the steel By comparing the distance between the table rollers of the conveying line used for conveying the sheet pile, it is determined whether the steel sheet pile product after the hot sawing can be conveyed on the table roller of the conveying line.

Then, when the conveyance becomes impossible, the component design is performed so that the Ar ₃ transformation completion temperature of the web after the finish rolling of the steel sheet pile is close to the cutting temperature of the hot cutting. The vicinity of the sawing temperature means a sawing temperature of ± 20 ° C. Within this range, after the web Ar ₃ transformation is completed in a short waiting time, hot sawing can be performed, and steel sheet pile manufacturing Does not significantly affect time productivity.

In addition, even after performing cooling and reaching the Web Ar ₃ transformation completion temperature, even when performing hot sawing, it is possible to perform hot sawing with mild cooling that does not affect the steel sheet pile. Occurs. The sawing temperature is preferably ± 15 ° C.
The product length of the steel sheet pile is compared with the distance between the table rollers of the conveyance line used to convey the steel sheet pile, and it is determined whether the steel sheet pile product after the hot cutting can be conveyed on the table roller of the conveyance line. If it is determined in step 1 that trouble will occur, then the web cooling rate after finish rolling of the steel sheet pile of the product dimensions is obtained, and the Ar ₃ transformation end temperature at the cooling rate is the hot sawing temperature. The component design is performed so as to be (step 2).

  Hereinafter, each step will be described in detail.

[Step 1]
When the steel sheet pile has a short overall length, if the steel sheet pile warps downward, the number of table rollers to be supported decreases, and the tip of the steel sheet pile to be conveyed is sandwiched between the table rollers, making conveyance impossible (Fig. 1, 2).

  In normal operation, if the number of table rollers of the conveyance table that supports the steel sheet piles to be conveyed is n or less, or the total length of the steel sheet piles to be conveyed is n times or less the gap length between the table rollers, the conveyance is impossible. It becomes.

  This relationship may be obtained in advance for each steel sheet pile product. In addition, by obtaining in advance, problems in production will be found in advance in the steel sheet pile where production is started, and when it is determined that the conveyance becomes impossible, until the bottom warp of the steel sheet pile is resolved, Since it cannot be loaded on a conveyance line and productivity falls remarkably, in this invention, the component design of a steel sheet pile is performed by step 2. FIG.

[Step 2]
In this step, the steel sheet pile component design is adjusted so that the Ar ₃ transformation end temperature of the web becomes the hot sawing temperature.

  In the production line of steel sheet piles, the arrangement of roughing mills, finish rolling mills and hot sawing devices is fixed, and the moving speed between each equipment is also fixed. When the cooling rate (usually air cooling) is defined, the sawing temperature for hot sawing is determined.

  Since steel sheet piles have different thicknesses between the flange and the web, the cooling rate of the web after finish rolling is determined.

The downward warping is a phenomenon during the Ar ₃ transformation of the web, and is eliminated after the completion of the Ar ₃ transformation of the web. Therefore, when the components of the steel sheet pile are designed so that the Ar ₃ transformation finishing temperature of the web becomes the hot sawing temperature, After hot sawing, it can be transported promptly, and the product length of the steel sheet pile is long, so that productivity does not decrease compared to a product that does not require transport standby due to downward warping.

If a difference between the Ar ₃ transformation end temperature and the hot sawing temperature of the changed web due to the design of the steel sheet pile components occurs, adjustment can be made by adding a little waiting time or cooling.

Hereinafter, the present invention will be specifically described with a hot sawing temperature of 700 ° C. and a steel sheet pile as a product standard SY295. The product length of the steel sheet pile is 6 m, and on the other hand, the distance between the table rollers in the transfer line is 1.5 m.

Therefore, the component design is performed so that the Ar ₃ transformation end temperature in the steel sheet pile web is 700 ° C. which is the hot sawing temperature. The hot cutting temperature is 18 mm for the product thickness (mm) of the web, the cooling rate is 0.5 ° C./s, the finish rolling finish temperature of the web is 760 ° C., from the finishing mill to the hot cutting device. The moving speed from the finishing mill to the hot sawing device was 120 m / s, and 1.0 m / s.

Table 1 shows an example of the component examination of SY295, and the Ar ₃ transformation end temperature was determined for Si—Mn, Nb, and Cu. Ar ₃ transformation end temperature at a cooling rate of around 0.5 ° C./s is Ar ₃ e (° C.) = 810-273 × C (%) + 27 × Si (%) − 74 × Mn (%) − 56 × Ni (% ) -16 × Cr (%)-9 × Mo (%)-5 × Cu (%)-1620 × Nb (%).

From Table 1, the Ar ₃ transformation end temperature is No. 3 and no. No. 9 has the highest Ar ₃ transformation end temperature of 687 ° C. 5 of 656 ° C. is the lowest.

  Since the sawing temperature is 700 ° C., the component composition of the steel sheet pile is No. 3 or No. No. 9 can be started by waiting until the temperature drops by 13 ° C. until the downward warping is resolved after hot cutting. In 5, it must wait until the temperature drops by 44 ° C.

  Since the air cooling rate is about 0.5 ° C./s, according to the present invention, it is not necessary to wait for 88 sec (44 / 0.5), and productivity can be improved.

An example which shows a steel sheet pile cross section. The figure which shows the steel sheet pile on a conveyance line, and demonstrates the state which became impossible to convey by the downward curvature. The figure which shows the steel sheet pile on a conveyance line, and demonstrates the state which became impossible to convey by the downward curvature.

Explanation of symbols

1 Steel sheet pile 2 Web 3 Flange 4 Joint 5 Table roller 6 Guide plate

Claims (4)

When manufacturing a steel sheet pile having a product size by hot sawing after finish rolling, the ingredients are set so that the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile becomes the sawing temperature of the hot sawing. A manufacturing method of a steel sheet pile characterized by performing design. The method for manufacturing a steel sheet pile according to claim 1, wherein the hot sawing is performed at a stage where the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile has been reached. 3. The steel sheet pile manufacturing method according to claim 1, wherein cooling is performed so that the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile is completed at the hot sawing position. Manufacturing method of sheet pile. In the manufacturing method of the steel sheet pile according to any one of claims 1 to 3, component design is performed so that the Ar ₃ transformation completion temperature of the web after finish rolling of the steel sheet pile becomes the sawing temperature of the hot sawing. Compare the product length of the steel sheet pile with the distance between the table rollers of the conveyance line used to convey the steel sheet pile, and whether the steel sheet pile product after hot cutting can be conveyed on the table roller of the conveyance line The steel sheet pile is characterized in that the component design is performed so that the Ar ₃ transformation completion temperature of the web after the finish rolling of the steel sheet pile is close to the cutting temperature of the hot sawing when it is judged and cannot be conveyed. Manufacturing method.

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