JPH02224801A - Rolling method for u-shaped steel sheet pile - Google Patents

Abstract

PURPOSE:To relieve the camber deformation while cooling from the end of the hot rolling of the U-shaped steel sheet pile before ordinary temp. is attained by executing slight reduction to the extent of shaping in the final pass in succession to reduction and cooling. CONSTITUTION:The breakdown rolling and intermediate rolling processes of a slab S to be rolled are executed in an ordinary manner. The slab S to be rolled is subjected to the bending to curl the flanges (f) thereof at the front end thereof and to form joints A and the reduction to form a slight crown (c) in the transverse central area of a web (w) after the above-mentioned rolling and before the final pass of a finishing mill 7. After the bending and reduction are executed, the front end of the slab S to be rolled is bitten with the rolling reduction rolls of the finishing mill 7 and while the front and rear of the slab to be rolled are kept restrained in this state, the slab is subjected to the force cooling to uniformly lower only the temp. of the web (w) in the longitudinal direction thereof. The slab is subjected to the reduction to the extent of the shaping to correct the crown (c) previously formed to the web (w) and the local deformation generated at the time of the reduction or cooling in the final pass of the finish rolling.

Description

Detailed Description of the Invention (Industrial Application Field) In the hot rolling of U-shaped steel sheet piles having flanges at each width end of the web, the ends of which are curled outward from each other, rolling of the steel sheet piles During the subsequent cooling process up to room temperature, unevenness in finishing temperature due to differences in thickness at various parts of the cross section causes differences in shrinkage, making warpage unavoidable.

This invention aims to effectively reduce warpage deformation that is inevitable when hot rolling U-shaped steel sheet piles.

(Prior art) U-shaped steel sheet piles have thick webs and flange thicknesses that have a relatively small cross-sectional shape, so the finished temperature after hot rolling is uneven in the cross section, and Warping deformation was inevitable during the cooling process (No. 9
(See Figure 10(a)).

Conventionally, to correct such warpage deformation, a roller straightening machine (three-point bending) installed on the same line or a straightening device installed off-line has been used, but with such devices, it is difficult to correct warp deformation. Not only was this insufficient (see FIG. 10(b)), but productivity was forced to drop significantly.

Here, as a prior art for suppressing the peculiar deformation during hot rolling of U-shaped steel sheet piles as described above, there is a restraint control cooling method (Japanese Unexamined Patent Publication No. 63-281709) or a temperature control rolling method for the material to be rolled. (Japanese Unexamined Patent Publication No. 55-48404) and the like are known.

(Issue g to be solved by the invention) The above-mentioned conventional technology is capable of correcting the warping deformation that occurs in the UY3 steel sheet pile during hot rolling to within a predetermined tolerance using a roller straightening machine or the like. In particular, in the U-position rolling method (Fig. 11(a)), the heat removed from the web in contact with the table is large, so the temperature difference between the web and the flange is small, and the temperature difference at the joint is small. This improves the temperature and reduces the wear of the rolls that control the curling of the flange tip, which has the advantage of extending the life of the rolls. There was a problem in that the transportation of the containers was unstable, especially when downward warping deformation occurred, making it impossible to perform a parallel shift at the transportation dock (reversing the container at the entrance to the cooling bed).

In addition, the restraint control cooling method (Fig. 11(b)) is capable of controlling up to the reverse warp deformation of steel sheet piles, and if it is realized without a straightening machine, it is possible to obtain good steel sheet piles without scale peeling. In the cooling process after hot rolling, detailed cooling control such as temperature measurement is required, and forced cooling can cause problems with material properties and flattening problems due to uneven temperatures on the front and back surfaces of the steel sheet piles. In addition to the problem that it is easy to use, there is also the disadvantage that the amount of capital investment increases significantly. Furthermore, in the temperature-controlled rolling method (FIG. 11(C)), there is a problem in that productivity is significantly reduced due to the necessity of adding a cooling standby time during the rolling process.

The purpose of this invention is to propose a new rolling method that can advantageously reduce the warpage that is inevitable when hot rolling U-shaped steel sheet piles, without significantly reducing productivity or performing complicated controls. With the goal.

(Means for Solving the Problems) The present invention provides a method for hot rolling U-shaped steel sheet piles having flanges at each width end of the web, the tips of which are curled outward from each other, and in which a plurality of breakdown rolling steps are performed. Then, a rolled material having an inverted U-shaped cross section having a web and flanges subjected to intermediate rolling is bent by curling the flanges outward at their tips to form a joint, and After rolling down to form a slight round, the rolling material is stopped with the tip of the material being bitten by the reduction roll, and the rear end of the material is restrained to lower the temperature of only the web. A method for rolling U-shaped steel sheet piles, characterized in that after forced cooling, the final pass is resumed to perform finish rolling in which the warp deformation that occurs during cooling is alleviated by slight reduction of the crown in the web of the rolled material. be.

Now, FIG. 1 schematically shows the layout of a rolling equipment suitable for carrying out the present invention, in which 1 indicates a heating furnace;
2 is a breakdown mill, 3 is an intermediate mill, 4 is a roller guide for bending that curls the tip of the flange f of the material to be rolled S, 5 is a restraint device, 6 is a water cooling device, 7
is a finishing mill, 8 is a hot saw, and 9 is a cooling bed.

A case will be described below, taking as an example a case in which a rolled material S heated and soaked to a desired temperature in the heating furnace 1 is rolled into a predetermined cross-sectional shape according to the flow shown in FIG. 2, for example.

As shown in FIG. 3, the cross-sectional shape of the rolled material S during each rolling process is shown in FIG.
a1, lo to 8) and intermediate rolling (a1, 7 to 4) processes follow the usual procedure. And after this rolling, finishing mill 7
Until the final pass (Ma1, 1) of (Ka1, 3
．． In 2), first, the flange f of the rolled material S is curled at its tip to form the joint A, and the web W is
There is a very slight round C (0.2~0.
5+u+).

After performing the above-mentioned bending and rolling, the tip of the rolled material S is bitten by the rolling roll of the finishing mill 7, and while the rear end is restrained, the temperature of only the web W is made uniform in its longitudinal direction. Perform forced cooling to lower the temperature to
Next, in the final bath of finish rolling following this forced cooling, a reduction to the extent of shaping is performed to correct the local deformation that occurred during the reduction of the crown C1 previously formed on the web W and during cooling.

(Function) In conventional rolling, the joint A at the flange f of the U-shaped steel sheet pile is finished into a desired shape in the final bath of finish rolling, as shown in FIG. In this invention, the reason why the joint A of the flange f is bent in order to finish it before the final bath is that the temperature of the joint A decreases significantly due to forced cooling of the web W, and if the bending work is performed in this state, it may crack. This is because it is easy to cause. Also web W
The reason why the crown C is formed in the center area in the width direction is that if the crown C is formed in this way, only the web W is slightly rolled down in the final bath of finish rolling, and the crown C is formed in the center area in the width direction. This is because local deformation can be effectively alleviated.

Here, the above-mentioned crown C is preferably set to a bulge amount such that the rolled material S does not warp deformation or slightly tends to warp downward during slight reduction in the final bath.

Furthermore, in the present invention, when the web W of the rolled material S is forcedly cooled uniformly in its longitudinal direction, the leading end of the rolled material S is bitten by the rolling roll, and the rear end is fixed by the restraining device 5. This is because when forced cooling such as water cooling is applied to the web W of the material S to be rolled, the occurrence of warping deformation is inevitable (especially when rolling in an inverted U shape, as shown in Figures 5(a) and 5(b)). In this case, the amount of deformation is greatest at the leading and trailing ends. A warp at the leading end makes it impossible to fit into the next bus, and a warp at the rear end makes it impossible to achieve uniform cooling by the cooling device 6.

As the device 5 for fixing the rear end of the rolled material S, a type that restrains both sides of the flange f as shown in FIG. 6 can be used, but if the rear end of the rolled material S is warped upward, If there is a possibility that this may occur, a type that can fix both sides of the flange f and the upper part of the web W may be used, as shown in FIG. In addition, if a plurality of restraint devices 5 are provided as shown in FIG. 8, when the tip of the material S to be rolled is bitten by the rolling roll, the material S to be rolled is positioned in the hole shape of the rolling roll by positioning. This is advantageous for accurately biting.

Following rolling and cooling in the manner described above, slight reduction to the extent of shaping is performed in the final bath, so the temperature of the U-shaped steel sheet pile after hot rolling is sufficiently low on the exit side of the final bath, and therefore The occurrence of large warping deformations that occur during the cooling process to room temperature can be advantageously reduced.

In carrying out the rolling according to the present invention, it is preferable that the rolled material S be placed in an inverted U posture in consideration of the guideability of the rolled material S and the transport workability after rolling.

(Example) A rolled material heated and soaked to 1200 to 1300'C in a heating furnace was processed in a breakagen mill and an intermediate mill for 50% each
〜11 buses, and then finish rolling with 3 passes.The first bus is normal rolling.
In the second pass of finish rolling, a crown of 0.2 to 0.5 mm is formed in the center area of the web width of the rolled material, and a bending process is performed to form a joint using a roller guide installed on the entry side of the finishing mill. went. Then, before passing through the final bus for finish rolling, the tip of the material to be rolled is bitten by the rolling roll, and conveyance is stopped at this point, and the rear end of the material to be rolled is fixed with a restraint device, and the flange is held as much as possible. The web was forcedly cooled by water cooling until the temperature of the web reached 750'C so as not to be cooled, and then subjected to shaping rolling with a slight reduction of 1 to 2%.

When the warping deformation in the obtained U-shaped steel sheet pile was investigated, the amount of deformation was less than 5 koms per 1 m, confirming that the rolling method according to the present invention is extremely effective.

(Effects of the Invention) Thus, according to the present invention, it is possible to significantly alleviate the warping deformation of the U-shaped steel sheet pile during the cooling from the end of hot rolling to room temperature, and the passing through the roller straightening machine (on-line straightening)
It is possible to keep the value within the allowable value for sufficient use, and compared to conventional warpage suppression technology, there is less reduction in rolling efficiency, and the equipment required for rolling is relatively simple and requires less increase in power. can suppress warpage deformation.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the layout of a rolling equipment suitable for carrying out the present invention, FIG. 2 is an explanatory diagram of the rolling procedure according to the present invention, and FIG. 3 is a diagram showing the rolled material at each rolling stage. Fig. 4 is an enlarged sectional view of the joint at the tip of the flange, and Fig. 5 (
a) and (b) are diagrams explaining the occurrence of warping deformation, and Fig. 6 (
a), (b), Figures 7 and 8 are explanatory diagrams of the restraint device, Figure 9 is a diagram showing the cross-sectional characteristics of the U-shaped steel sheet pile, and Figure 1θ (
a), Φ) are diagrams showing warping deformation and local deformation of a U-shaped steel sheet pile, and FIGS. 11(a), (b), and (C) are explanatory diagrams of conventional methods for suppressing warping deformation. 1...Heating furnace 3...Intermediate mill 5...Restraint device 7...Finishing mill 9...Cooling bed...Breakdown mill...Roller guide...Water cooling device...Heat Fig. 3 Fig. 9 Queg thickness (may) Fig. 3 (a)

Claims (1)

[Scope of Claims] 1. When hot rolling a U-shaped steel sheet pile having flanges at each width end of the web, the tips of which are curled outward, multiple breakdown rolling and intermediate rolling are performed. A rolled material having an inverted U-shaped cross section with a web and flanges is bent by curling the flanges outward at their ends to form a joint, and forming a very slight crown in the center area in the width direction of the web. After applying the rolling reduction, the rolling material was stopped with the leading end of the material being bitten by the reduction roll, and forced cooling was performed by restraining the rear end of the material and reducing the temperature of only the web. A method for rolling U-shaped steel sheet piles, characterized in that the final pass is resumed after finishing rolling to alleviate warping deformation occurring during cooling by slight reduction of the crown in the web of the material to be rolled.