JP7544082B2 - Manufacturing method of hat-shaped steel sheet pile - Google Patents

Description

The present invention relates to a manufacturing method for hat-shaped steel sheet piles.

Conventionally, steel sheet piles with joints at both ends, such as hat-shaped ones, have been manufactured by the groove rolling method. A general process of this groove rolling method is known to be to first heat a steel material (rectangular material) to a specified temperature in a heating furnace, and then roll it in sequence using a roughing mill, an intermediate rolling mill, and a finishing rolling mill, each of which is equipped with a groove. In addition, rolling using a roughing mill, an intermediate rolling mill, and a finishing rolling mill is also called rough rolling, intermediate rolling, and finishing rolling, respectively, and these rolling processes are collectively called shaping rolling.

As a groove rolling method, for example, Patent Document 1 discloses a technology for manufacturing a hat-shaped steel sheet pile by forming multiple grooves in the rolls in rough rolling, intermediate rolling, and finish rolling, and performing rolling one or two passes with each groove. Patent Document 2 also discloses a technology for manufacturing a steel sheet pile having a flange, in which the rolling of the material to be rolled in the rough rolling process and intermediate rolling process is performed by multiple passes with multiple consecutive grooves, and in rolling with multiple grooves, the roll gap of the flange corresponding part is configured under predetermined conditions such that the flange reduction rate near the rolling neutral line is smaller in two consecutive grooves compared to the total flange reduction rate in the latter groove, and rolling is performed.

JP 2006-88176 A JP 2019-38014 A

However, the above conventional technology has the following problems to be solved. That is, in the technology disclosed in Patent Document 1, the flange is made straight at approximately the same angle as the product in the rough rolling, intermediate rolling, and finishing rolling processes, and one or two passes are rolled with a single hole type. However, when the flange width is large and the plate thickness is thin, reverse rolling may cause flange waves to occur due to an unbalanced elongation of each part in the cross section. In addition, after intermediate rolling, the flange crop stretches too much at the leading edge and the trailing edge of the material, causing deformation such as "shrinking inward" or "expanding outward" with respect to the hat-shaped cross section, which may cause the next pass of rolling to be unable to be properly bitten, or may cause the crop part to be bitten twice, resulting in poor biting. Note that "biting twice" refers to the long crop part being bent and bitten into the roll like two plates. In addition, the technology disclosed in Patent Document 2 does not provide sufficient conditions for suppressing the occurrence of flange waves. Furthermore, this technology does not prevent deformation of the crop area after intermediate rolling or poor engagement due to deformation of the crop area.

The present invention has been made in consideration of the above problems, and its purpose is to provide a manufacturing method for hat-shaped steel sheet piles that can suppress the occurrence of flange waves, while suppressing deformation of the crop portion and suppressing poor engagement.

In order to solve the above-mentioned problems and achieve the object, the manufacturing method of the hat-shaped steel sheet pile according to the present invention is a manufacturing method of the hat-shaped steel sheet pile in which the material to be rolled is subjected to rough rolling, intermediate rolling, and finish rolling in sequence using a plurality of grooves to produce a hat-shaped steel sheet pile having a web, a flange, an arm portion, and a joint portion, and is characterized in that in the rough rolling, the material to be rolled is rolled so that the thickness of the center part of the height direction of the flange is thinner than the thickness of the part other than the center part of the height direction of the flange, and at least one of the front end crop part and the rear end crop part of the material to be rolled after the rough rolling is cut before the intermediate rolling is performed.

The manufacturing method of the hat-shaped steel sheet pile according to the present invention is characterized in that, in the above invention, when cutting either the leading edge crop portion or the trailing edge crop portion, the crop portion that is to be the biting side of the first roll in the intermediate rolling is cut.

The manufacturing method of the hat-shaped steel sheet pile according to the present invention is characterized in that, in the above invention, the material to be rolled is rolled in the final groove in the rough rolling so that the thickness of the center part of the flange in the height direction is thinner than the thickness of the part other than the center part of the flange in the height direction.

The manufacturing method of the hat-shaped steel sheet pile according to the present invention is characterized in that, in the above invention, the material to be rolled is rolled in the final groove in the rough rolling so that the thickness of the center part of the flange in the height direction is 85 to 95% of the thickness of the part other than the center part of the flange in the height direction.

The manufacturing method of the hat-shaped steel sheet pile according to the present invention has the effect of suppressing the occurrence of flange waves while suppressing deformation of the crop portion and suppressing poor engagement.

FIG. 1 is a diagram showing the cross-sectional shape of a hat-shaped steel sheet pile. FIG. 2 is an explanatory diagram showing the equipment configuration of a rolling line. FIG. 3 is a diagram showing a roll groove type for rough rolling. FIG. 4 is a diagram showing a roll groove type for intermediate rolling. FIG. 5 is a diagram showing a roll groove type for finish rolling. FIG. 6 is a diagram showing a schematic diagram of a flange wave. FIG. 7 is a diagram showing an example of a crop shape after intermediate rolling. 8(a) is a diagram showing a shape in which the cropped portion of the flange is bent inward, and FIG 8(b) is a diagram showing a shape in which the cropped portion of the flange is bent outward. Fig. 9(a) is a partial enlarged view of a flange portion of the K7 hole type, and Fig. 9(b) is an enlarged view of part A in Fig. 9(a).

Below, an embodiment of a manufacturing method for a hat-shaped steel sheet pile according to the present invention will be described. Note that the present invention is not limited to this embodiment. In this embodiment, the rolling target material having a hat-shaped steel sheet pile shape will be described as being rolled in a position in which the web is located above the flange (so-called inverted U position or hat position), but the scope of application of the present invention naturally extends to rolling in other positions (for example, U position).

Figure 1 shows the cross-sectional shape of a hat-shaped steel sheet pile 1.

As shown in FIG. 1, the hat-shaped steel sheet pile 1 manufactured in this embodiment has a uniform cross-sectional shape perpendicular to the longitudinal direction, which is a hat shape. The hat-shaped steel sheet pile 1 has a cross-sectional shape including a web 11, a pair of flanges 12, a pair of arms 13, and a pair of joints 14. The web 11 is a portion extending in one direction (the left-right direction in FIG. 1, also referred to as the "left-right direction" below). The pair of flanges 12 are portions connected to both ends of the web 11 in the left-right direction and extend at an incline with respect to the left-right direction. In the example shown in FIG. 1, the pair of flanges 12 extend at an incline so that the opposite end of the web 11 is on the lower side in the vertical direction (the up-down direction in FIG. 1, the direction perpendicular to the left-right direction). The pair of arms 13 are portions connected to the side of the pair of flanges 12 to which the web 11 is not connected and extend in the left-right direction. The pair of joints 14 are connected to the sides of the pair of arm parts 13 to which the flanges 12 are not connected, and have a hook-like shape that opens upward or downward in the vertical direction. When used as a steel sheet pile, the pair of joints 14 are used to connect to other steel sheet piles by fitting into the joints of other steel sheet piles. In this embodiment, the arm parts 13 and the joint parts 14 are also collectively referred to as a flat part. The flat part is a part of the hat-shaped steel sheet pile 1 that is formed by connecting to the end of the flange 12 to which the web 11 is not connected, and has a flat part extending in the left-right direction. In this embodiment, the arm part 13 is the flat part of the flat part. The distance between the pair of joints 14 indicated by W in FIG. 1 is referred to as the effective width, and the vertical distance from the upper surface of the web 11 to the lower surface of the arm part 13 indicated by H in FIG. 1 is referred to as the effective height.

Next, we will explain the rolling line used to manufacture hat-shaped steel sheet piles 1. Figure 2 is an explanatory diagram showing the equipment configuration of the rolling line 2.

2, the rolling direction in the rolling line 2, that is, the transport direction of the material to be rolled, is the direction indicated by the arrow in FIG. 2. The slab, which is the material to be rolled and heated in the heating furnace 3, is hot-rolled using multiple grooves in the roughing mill 4, intermediate mill 5, and finishing mill 6, and is finished into the product shape of the hat-shaped steel sheet pile 1 shown in FIG. 1. In these rolling mills, grooves called calibers are engraved on the upper and lower rolls. In this embodiment, the rolling by the roughing mill 4, intermediate mill 5, and finishing mill 6 are also referred to as rough rolling, intermediate rolling, and finishing rolling, respectively, and these rolling processes are also collectively referred to as shaping rolling. In this embodiment, rough rolling and intermediate rolling are each performed by multiple pass rolling using two or more of the multiple grooves, and finish rolling is performed by one or more passes using one or more of the multiple grooves. As shown in FIG. 2, three stages of rough rolling (Box, K8, K7), four stages of intermediate rolling (K6, K5, K4, K3), and two stages of finish rolling (K2, K1) are exemplified. In addition, a tongue cut saw 7 is installed on the exit side of the rough rolling mill 4, and at least one of the leading end crop portion and the trailing end crop portion of the rolled material after rough rolling can be cut off.

Figure 3 shows the roll grooves used for rough rolling. Specifically, Figure 3 shows an example of the grooves of the rough rolling mill 4 used for rough rolling the hat-shaped steel sheet pile 1, and three grooves, a Box groove, a K8 groove, and a K7 groove, are engraved on the upper roll 41 and the lower roll 42.

In the rough rolling of this embodiment, first, the width of the slab, which is the material (raw material) to be rolled, is reduced in the Box groove. Next, the slab is bent into a hat shape and its thickness is reduced in the K8 groove. Furthermore, the thickness is further reduced in the K7 groove, and the slab is shaped into a shape close to the cross-sectional shape of the product. In the K8 groove and K7 groove of the rough rolling, multiple passes of rolling are performed.

Similarly, in the intermediate rolling mill 5, two to four grooves are engraved on one upper and lower roll pair, and rolling is performed sequentially using these grooves. Figure 4 shows the roll grooves for intermediate rolling. Specifically, Figure 4 shows an example of the grooves of the rolling mill 5A in the intermediate rolling mill 5 for hat-shaped steel sheet pile 1, and two grooves, K6 groove and K3 groove, are engraved on the upper roll 51A and the lower roll 52A, which are one upper and lower roll pair.

In addition, the other rolling mill 5B (not shown) of the intermediate rolling mill 5 for the hat-shaped steel sheet pile 1 also has two grooves, a K5 groove and a K4 groove.

In the intermediate rolling of this embodiment, the first pass of intermediate rolling is performed with a K6 groove (K5 rolling is a dummy with no reduction), and the second pass, which is rolling in the opposite direction to the first pass, is performed with tandem rolling using a K6 groove and a K5 groove. Furthermore, the third pass is performed with tandem rolling using a K4 groove and a K3 groove.

Similarly, in the finishing rolling mill 6, one to three grooves are engraved on one pair of upper and lower rolls, and rolling is performed sequentially using these grooves. Figure 5 shows the roll grooves used in finishing rolling. Specifically, Figure 5 shows an example of the grooves of the finishing rolling mill 6 for hat-shaped steel sheet pile 1, and two grooves, K2 groove and K1 groove, are engraved on the upper roll 61 and the lower roll 62, which are one pair of rolls.

In the finish rolling of this embodiment, the intermediately rolled material is rolled to the final thickness in the first pass of the finish rolling using the K2 groove, and in the second pass, which is rolling in the reverse direction, the claw bending of the joint portion 14 is performed using the K1 groove to form the product cross-sectional shape. The third pass is forward rolling through the K1 groove, but is a dummy roll in which no reduction or claw bending is performed. Note that in this finish rolling, the second pass may be a dummy roll, and claw bending may be performed using the K1 groove in the third pass. Two passes of rolling may also be performed using the K2 groove.

When rolling such hat-shaped steel sheet piles 1, a shape defect called a "flange wave" may occur. Figure 6 is a diagram showing a flange wave 20. As shown in Figure 6, the flange wave 20 is a shape defect in which the flange 12 (outer surface side) is not flat, but changes in height in the longitudinal direction, resulting in a wavy shape.

Here, flange waves 20 often occur in the latter passes of intermediate rolling, where the thickness becomes thinner, or in finish rolling. If the flange waves 20 remain after the final rolling, the material cannot be made into a product (rejected product), and the product yield is significantly reduced, so it is necessary to suppress the occurrence of flange waves 20. Note that, for example, in this embodiment, an acceptable product without flange waves 20 refers to a material in which the difference in height between the highest point of the wave and the lowest point of the wave in the longitudinal direction on the outer surface side of the flange 12 does not exceed a predetermined allowable value, and the allowable value is set appropriately, but is 0.5 [mm] in this embodiment.

Next, we will explain the cropped portion of the hat-shaped steel sheet pile 1. Figure 7 shows an example of the crop shape after intermediate rolling.

The length of the cropped portions 151, 152, 153 of the web 11, flange 12, and arm portion 13 is also affected by the reduction rate in the cross section, but the cropped portion 152 of the flange 12 tends to elongate in the center of the height direction of the flange 12, and tends to be long in the center of the height direction of the flange 12. This is because, due to the characteristics of the grooved rolling of the hat-shaped steel sheet pile 1, metal flow occurs from the upper and lower parts of the height direction of the flange 12 toward the center of the height direction of the flange 12 during rolling, and the amount of metal in the center of the height direction of the flange 12 increases. In this way, the metal that gathers in the center of the height direction of the flange 12 is rolled with a roll gap that is almost equal in the height direction of the flange 12 after intermediate rolling, so that the cropped portion 152 also has a shape in which the center of the height direction of the flange 12 elongates the longest.

Figure 8(a) shows a shape in which the cropped portion 152 of the flange 12 is bent inward. Figure 8(b) shows a shape in which the cropped portion 152 of the flange 12 is bent outward.

Deformation of the crop portion 152 of the flange 12 is likely to occur at the end where the flange 12 is bitten during rolling, and whether it bends inward or outward depends on the rolling conditions, such as the difference in the friction state between the upper roll on which the groove for rolling the flange 12 is engraved and the lower roll. In addition, if the length (crop length) of the crop portion 152 of the flange 12 is long, the amount of deformation of the crop portion 152 inward or outward also increases, making it easier for poor biting during rolling to occur. For example, as shown in FIG. 8(a), when the crop portion 152 of the flange 12 is bent inward, the crop portion 152 hits the web guide on the inlet side of the next pass (next groove) and cannot be bitten by the roll. Conversely, as shown in FIG. 8(b), when the crop portion 152 of the flange 12 is bent outward, the crop portion 152 is completely bent by the biting of the next pass (next groove), and two pieces may be bitten. When double jamming occurs, the thickness of the inlet flange at that point becomes twice as thick as normal, greatly increasing the risk of roll cracking or breakage.

The inventors of the present application have studied a method of suppressing the elongation of the cropped portion 152 of the flange 12 after intermediate rolling in the rolling line shown in FIG. 2, thereby suppressing the crop deformation. As a result, in the rough rolling stage, the vicinity of the center of the height of the flange 12 in the rough steel billet is formed thinner than the other parts of the flange 12, and the cropped portion 152 of the flange 12 is cut by a tongue cut saw 7 installed in the rear stage of the rough rolling mill 4. Then, the reduction ratio of the thickness of the vicinity of the center of the height of the flange 12 in the subsequent intermediate rolling and finish rolling is set not to be too large compared to the other parts of the flange 12, thereby suppressing the crop elongation of the center of the height of the flange 12. This method makes it possible to reduce the reduction ratio of the center of the height of the flange 12 after intermediate rolling, and therefore it is possible to suppress the occurrence of flange waves, which are a problem in the latter half of intermediate rolling and finish rolling.

When the upper side of the flange 12 (the side closer to the web 11 in the hat position) or the lower side of the flange 12 (the side closer to the arm 13 in the hat position) stretches more than the center of the height of the flange 12, the flange 12 is close to the bent portion where the flange 12 and the web 11 join, or the bent portion where the flange 12 and the arm 13 join, the rigidity is high and crop deformation is unlikely to occur.

Flange waves become a problem from the latter half of intermediate rolling to finish rolling, and in order to suppress the occurrence of flange waves here, it is important to prevent the increase in thickness of the center of the flange 12 in the rolling upstream of this. The increase in thickness that causes flange waves is likely to occur in rolling with grooves after intermediate rolling. Therefore, in order to suppress this increase in thickness in advance, in this embodiment, for example, in rolling with the final K7 groove in rough rolling or the first K6 groove in intermediate rolling, rolling conditions are adopted in which the roll gap that rolls down the center of the height direction of the flange 12 is narrower than the roll gap that rolls down other parts of the flange 12.

Figure 9(a) is a partial enlarged view of the flange portion of the K7 hole type. Figure 9(b) is an enlarged view of part A in Figure 9(a).

As shown in FIG. 9, in this embodiment, as the final K7 groove of the rough rolling, a convex portion 421 with a convex amount d is provided at a position corresponding to the center of the height of the flange 12 of the lower roll 42, and the roll gap for pressing down the center of the height of the flange 12 is narrower than other parts of the flange 12. Note that "L1" in FIG. 9 indicates the width of the convex portion 421 in the direction along the flange 12. "L2" in FIG. 9(b) indicates the width of the convex portion 421 in the left-right direction (direction along the web 11) of the hat-shaped steel sheet pile 1. In addition, the convex portion provided at the position corresponding to the center of the height of the flange 12 in the K7 groove may be installed on either one or both of the upper roll 41 and the lower roll 42. The shape of the convex portion is not limited to the arc shape shown in FIG. 9(b), and may be, for example, a trapezoidal shape or a triangular shape.

By rolling with such a K7 groove, the thickness of the center of the height of the flange 12 can be made thinner than the other parts of the flange 12. In this case, it is desirable that the thickness of the center of the height of the flange 12 is 85 to 95% of the thickness of the other parts of the flange 12. The reason for this is that if the thickness exceeds 95%, the effect of suppressing excessive stretching of the cropped portion 152 in the center of the height of the flange 12 after intermediate rolling may be reduced. Conversely, if the thickness is less than 85%, problems may occur with the biting of the flange 12 in the first rolling pass with the K7 groove, for example, the center of the height of the flange 12 may be locally under strong pressure, and biting may not be performed well.

In this way, the cropped portion 152 of the flange 12 in the rough steel billet formed by rough rolling has a shape in which the center of the flange 12 in the height direction is elongated compared to conventional shapes, but since the material is thick at the rough rolling stage, crop deformation does not pose a problem. Furthermore, for at least one of the leading end or trailing end where crop deformation becomes a problem after intermediate rolling, the tongue cut saw 7 installed downstream of the rough rolling mill 4 cuts off the cropped portion 152 of the flange 12, etc., to set the crop length to zero at the start of intermediate rolling.

For example, in the case of rolling in the rolling line shown in FIG. 2, the tip side of the material that has finished intermediate rolling will be bitten again as the tip side in the first pass of the next finishing rolling, so crop deformation is likely to become a problem, especially at the rolling tip side. Therefore, in this case, it is preferable to cut off the crop portion on the tip side of the material by the tongue cut saw 7 after rough rolling. On the other hand, the rolling rear end side will be bitten in the K6 groove and the K5 groove from the rear end side of the material in the second pass of intermediate rolling, which is the return pass. Therefore, depending on the groove shape and rolling conditions, crop deformation may become a problem when the K5 groove is bitten. In such a case, the crop portion on the rear end side of the material can be cut off by the tongue cut saw 7 at the end of rough rolling. In this way, how to cut the crop portions on the tip side and rear end side after rough rolling can be appropriately selected depending on the rolling method and rolling conditions after intermediate rolling.

In addition, FIG. 9 shows a case where a K7 groove is used to thin the center portion of the flange 12 in the height direction, but a similar groove can also be used for the K8 groove. In addition, the K7 groove shown in FIG. 9 can be used to perform one pass of rolling, or multiple passes of rolling.

(Example)
As an example of the present invention, a hat-shaped steel sheet pile 1 of 25H (series designation) with a product web thickness of 13.2 [mm] was rolled using the roll grooves shown in Figures 3 to 5 on the rolling line shown in Figure 2. In addition, in the compatible example, the K7 groove was rolled using a groove having a convex portion 421 for the roll gap that rolls down the height direction center of the flange 12 as shown in Figures 9 (a) and 9 (b). The convex amount d of this convex portion 421 was set to 2.0 [mm]. Note that the K6 groove to the K1 groove are normal grooves without a convex portion. In contrast, in some of the comparative examples, a flat groove without a convex portion was used for the K7 groove. In these compatible examples and comparative examples, various conditions were set for cutting the crop portions at the front and rear ends of the material with the tongue cut saw 7 at the end of rough rolling. In addition, the occurrence of flange waves at the product stage was investigated. These conditions and results are shown in Table 1. In Table 1, Compliant Examples 6 and 7 (Conditions No. 8 and 9) are conditions in which the roll gap in the first pass of intermediate rolling is widened in both rolling mills 5A and 5B of the intermediate rolling mill 5, no thickness reduction is performed, and the intermediate rolling starts biting from the rear end side.

As is clear from Table 1, in Compliant Examples 1 to 7, no flange waves with problematic wave irregularity heights exceeding 0.5 mm occurred, and products with good shapes were obtained. In particular, in Compliant Examples 1 to 3 and 5 to 7 (Conditions No. 1 to 3 and 7 to 9), in which the thickness of the center part of the flange 12 in the height direction was set to 85 to 95% of the thickness of the flange 12 other than the center part in the height direction in K7 groove rolling, products with particularly good shapes, with flange wave heights of 0.2 mm or less, were obtained.

In contrast, in Comparative Example 1, by adjusting the rolling conditions, it was possible to roll to the finish rolling stage, but in the end, the flange wave height of the product exceeded the standard (0.5 mm), and a product with a good shape could not be obtained. In Comparative Example 2, in which the cropped portion was not cut off by the tongue cut saw 7, the crop deformation on the tip side was large, resulting in a misroll in which the roll could not be engaged in the first pass of the finish rolling.

In this embodiment, a rolling example of a 25H hat-shaped steel sheet pile 1 is shown, but it has been confirmed that the present invention can also be applied to other series of hat-shaped steel sheet piles (10H, 50H, etc.). In addition, even if the cropped portion on the rear end side is cut off by a tongue cut saw 7, the same effect can be achieved, especially in a rolling pass in which the rear end side is continuously bitten in multiple passes.

Reference Signs List 1 Hat-shaped steel sheet pile 2 Rolling line 3 Heating furnace 4 Rough rolling mill 5 Intermediate rolling mill 5A, 5B Rolling mill 6 Finishing rolling mill 7 Tongue cut saw 11 Web 12 Flange 13 Arm portion 14 Joint portion 20 Flange wave 41, 51A, 61 Upper roll 42, 52A, 62 Lower roll 151, 152, 153 Crop portion 421 Convex portion

Claims (4)

A method for manufacturing a hat-shaped steel sheet pile, comprising the steps of: subjecting a material to be rolled to rough rolling, intermediate rolling, and finish rolling in sequence using a plurality of grooves; and manufacturing a hat-shaped steel sheet pile having a web, a flange, an arm portion, and a joint portion,
In the rough rolling, the rolling target material is rolled so that the thickness of the center part of the flange in the height direction is thinner than the thickness of the part other than the center part of the flange in the height direction,
After the rough rolling, at least one of a front end crop portion and a rear end crop portion of the rolling target material after the rough rolling is cut off before the intermediate rolling is performed ;
The manufacturing method of the hat-shaped steel sheet pile, characterized in that a rolling reduction rate of a center part in a height direction of the flange after the intermediate rolling is made smaller than that of other parts of the flange . The method for manufacturing a hat-shaped steel sheet pile according to claim 1, characterized in that when cutting either the leading edge crop portion or the trailing edge crop portion, the crop portion that is the first rolling bite side in the intermediate rolling is cut. The method for manufacturing hat-shaped steel sheet piles according to claim 1 or 2, characterized in that in the final groove of the rough rolling, the material to be rolled is rolled so that the thickness of the center part of the flange in the height direction is thinner than the thickness of the parts other than the center part of the flange in the height direction. The method for manufacturing a hat-shaped steel sheet pile according to any one of claims 1 to 3, characterized in that in the final groove of the rough rolling, the material to be rolled is rolled so that the thickness of the center part of the flange in the height direction is 85 to 95% of the thickness of the part other than the center part of the flange in the height direction.

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