Deformed steel bar twisting suppression method

Abstract

To provide a deformed steel bar twisting suppression method that can produce a deformed steel bar with non-twisting on an entire length thereof.SOLUTION: A deformed steel bar R, in which a projection S is formed by a mill roll 2 for molding projection, is plastically processed by using a pair of rolls installed on a downstream side of the mill roll 2 for molding projection, thereby correcting twisting occurring in the deformed steel bar R. For the pair of rolls, a convex roll 3, of which a cross-sectional shape is a circular arc-shaped convex and in which many small protrusions and / or small recesses are formed on a surface of a protrusion having the circular arc-shaped convex, is used. A portion of a concave groove H of the deformed steel bar R, in which the projection S is not formed and of which a cross-sectional shape is circular arc-shaped, is depressed from both sides by the protrusion and the small protrusion and / or the small recess of the convex roll 3, and plastic processing is applied to a central part of the deformed steel bar R, thereby correcting twisting occurring in the deformed steel bar R.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for suppressing twisting of deformed steel bars (reinforcing bars that have protrusions such as ribs or screw-like knots formed on their surfaces to increase their adhesive strength to concrete, and are also called "deformed steel bars." In this specification, "deformed steel bars" and protrusions such as ribs or screw-like knots formed on their surfaces are simply referred to as "protrusions") when they are manufactured, thereby suppressing twisting that occurs in the deformed steel bars and improving the shape of the deformed steel bars. [Background technology]

[0002] However, when deformed steel bars are manufactured by rolling, they tend to induce twisting due to the formation of protrusions such as ribs and screw-like knots on the surface, which has led to the problem of reduced shape accuracy of the deformed steel bars.

[0003] As a countermeasure to this problem, that is, as a method to suppress the twisting that occurs in deformed steel bars when manufacturing them, 1. A method of offsetting the twist that occurs in the deformed steel bar by tilting the rolling entrance guide in the opposite direction in advance (see, for example, Patent Document 1). 2. A method of correcting twists that occur in deformed steel bars by using roller guides to hold the deformed steel bars at the exit stand (see, for example, Patent Document 2). has been proposed and put into practical use.

[0004] However, the above-mentioned conventional method for suppressing twisting of deformed steel bars is as follows: 1. The method of tilting the rolling entrance guide in the opposite direction in advance results in asymmetric rolling, which reduces the shape accuracy of the shoulder thread. 2. The method of holding deformed steel bars using roller guides at the exit stand results in untwisting correction at two points where the rollers of the roller guide come into contact, and products whose properties are not uniform along their entire length (tip, middle, and rear end) will still have uneven twists. There was a problem.

[0005] Incidentally, in consideration of the problems with the conventional methods for suppressing twisting of deformed steel bars described above, the applicant of the present invention previously proposed a method for suppressing twisting of deformed steel bars, which can produce deformed steel bars that are free from twist along their entire length by applying uniform deformation from the side, even in the case of products whose properties are not uniform along their entire length (tip, middle, and tail) (see Patent Document 3).

[0006] Specifically, this method of suppressing twist in deformed steel bars involves plastically deforming a threaded rebar, which has had a threaded knot formed using a thread-shape forming mill roll, using a pair of rolls installed downstream of a thread-shape forming mill to correct the twist that occurs in the threaded rebar.The pair of rolls uses convex rolls with an arc-shaped cross section, and the areas of the threaded rebar where no threaded knots are formed are pressed down from both sides, and plastic processing is applied to the center of the threaded rebar, thereby correcting the twist that occurs in the threaded rebar.However, when plastic processing is performed using convex rolls with an arc-shaped cross section, there is a problem in that the center of the threaded rebar may not be sufficiently plastically deformed, leaving a twist. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-150017 [Patent Document 2] Japanese Patent Application Laid-Open No. 2007-125597 [Patent Document 3] Patent No. 7340677 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the problems associated with the conventional methods for suppressing twisting of deformed steel bars described above, the present invention aims to provide a method for suppressing twisting of deformed steel bars that can produce deformed steel bars that are free from twist throughout their entire length by improving the method for suppressing twisting of deformed steel bars disclosed in Patent Document 3. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the method for suppressing twisting of deformed steel bars of the present invention comprises the steps of: forming protrusions in a deformed steel bar using a protrusion-forming rolling roll of a protrusion-forming rolling mill; plastically deforming the deformed steel bar using a pair of rolls installed downstream of the protrusion-forming rolling mill; and correcting the twist that occurs in the deformed steel bar; the method comprises the steps of: as a subsequent step to the step of forming protrusions using the protrusion-forming rolling rolls, using convex rolls that have an arc-shaped convex cross section and have a number of small convex portions and / or small concave portions formed on the surface of the arc-shaped convex portion; pressing down from both sides the convex portions and small convex portions and / or small concave portions of the convex rolls at the portions of the concave grooves that have an arc-shaped cross section and where no protrusions are formed in the deformed steel bar; and applying plastic processing to the center of the deformed steel bar, thereby correcting the twist that occurs in the deformed steel bar.

[0010] In this case, the small recesses and / or small protrusions formed on the surface of the grooves of the deformed steel bar by the small protrusions and / or small recesses can have a scale function that displays the longitudinal dimensions of the deformed steel bar.

[0011] In addition, the surface of the deformed steel bar on which the recessed groove is formed may be configured so that no ribs are formed. [Effects of the Invention]

[0012] According to the method for suppressing twisting of deformed steel bars of the present invention, as a subsequent process to the process of forming protrusions with a protrusion-forming rolling roll, a pair of rolls installed downstream of the protrusion-forming rolling mill are used, which have a convex cross-sectional shape in an arc-shaped configuration and have a large number of small protrusions and / or small recesses formed on the surface of the convex arc-shaped convex portion, and the areas of the deformed steel bar where no protrusions are formed, the concave grooves with an arc-shaped cross-sectional shape, are pressed down from both sides by the convex portions and small protrusions and / or small recesses of the convex roll, and plastic processing is applied to the center of the deformed steel bar, thereby correcting the twist that occurs in the deformed steel bar.This process allows the minimum necessary plastic processing to be applied to the center of the deformed steel bar when manufacturing deformed steel bars with a simple mechanism, and does not excessively deform the protrusions of the deformed steel bar that had protrusions formed in the previous process, so that the shape of the deformed steel bar can be improved with good dimensional accuracy while suppressing the twist that occurs in the deformed steel bar. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is an explanatory diagram showing an example of a rolling process for implementing a method for suppressing twisting of a deformed steel bar according to the present invention. FIG. [Figure 2] FIG. [Figure 3] 4 is an explanatory diagram showing the state of change in shape of the steel bar in the rolling process. FIG. [Figure 4] 10 is a photograph showing a deformed steel bar that has undergone the same rolling process. [Figure 5] 1A, 1B, and 1C are schematic diagrams showing deformed steel bars that have undergone the rolling process, in which (a) is a plan view, (b) is a front view, and (c) is a side view. [Figure 6] 1A and 1B are explanatory diagrams showing a typical deformed steel bar, where (a) is a front view and (b) is a side view. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, an embodiment of the method for suppressing twisting of a deformed steel bar according to the present invention will be described with reference to the drawings.

[0015] 1 to 3 show an embodiment of a method for suppressing twisting of a deformed steel bar according to the present invention. This method of suppressing twisting of deformed steel bars involves correcting the twist that occurs in a deformed steel bar R by plastically processing a deformed steel bar R on which protrusions (screw-shaped knots) S have been formed using a protrusion-forming rolling roll (screw-shaped forming rolling roll) 2, using a pair of rolls installed downstream of the protrusion-forming rolling roll (screw-shaped forming rolling roll) 2.The pair of rolls uses a convex roll 3 which has a convex cross-sectional shape in an arc and has a large number of small convex portions and / or small concave portions formed on the surface of this convex arc-shaped portion.The areas of the deformed steel bar R, where the protrusions (screw-shaped knots) S are not formed, and which have an arc-shaped cross-sectional shape and a concave groove H, are pressed down from both sides by the convex portions and small convex portions and / or small concave portions of the convex roll 3, and plastic processing is applied to the center of the deformed steel bar R, thereby correcting the twist that occurs in the deformed steel bar R.

[0016] Here, the protrusion forming roll 2 is a thread shape forming roll used to form thread-shaped knots S in the reinforcing bar material R0, but various types of rolls can be used depending on the shape of the protrusions S of the deformed steel bar R to be manufactured.

[0017] In this case, a groove-forming roll 1 is placed in the process preceding the protrusion-forming roll (thread-shape forming roll) 2, and before the protrusion (thread-shape forming roll) 2 forms the protrusion (thread-shaped knot) S, the groove-forming roll 1 forms a groove H with an arc-shaped cross-section extending in the longitudinal direction of the reinforcing bar material R0 at a 180° symmetrical position on the circumferential surface of the reinforcing bar material R0.

[0018] The convex roll 3 has a cross-sectional shape of an arc-shaped convex, and has many small convex portions and / or small recesses formed on the surface of this arc-shaped convex portion.The convex roll 3 has an arc-shaped convex shape with a smaller radius of curvature than the concave groove H, and the convex portions and small convex portions and / or small recesses of the convex roll 3 fit into the areas of the deformed steel bar R where protrusions (thread-shaped knots) S are formed by the groove-forming rolling roll 1 and the protrusion-forming rolling roll (thread-shaped forming rolling roll) 2, i.e., the groove H area, where no protrusions (thread-shaped knots) S are formed, and the convex portions and small convex portions and / or small recesses of the convex roll 3 fit into the areas of the arc-shaped convex portion where many small convex portions and / or small recesses are formed on the surface, and press down from both sides, applying plastic processing uniformly to the center of the deformed steel bar R, thereby correcting any twist that occurs in the deformed steel bar R.

[0019] Here, the numerous small convex portions and / or small recesses formed on the surface of the arc-shaped convex portion of the convex roll 3 can be square or round small protrusions and / or small recesses arranged regularly (in a grid pattern, checkerboard pattern, etc.).

[0020] The deformed steel bar R, the twist of which has been corrected by the convex rolls 3, is transported to a cooling bed (not shown) via run-in rollers 4 and breaking plates 5.

[0021] An example of a deformed steel bar R manufactured by this method for suppressing twisting of a deformed steel bar is shown in Figs. Deformed steel bar R is manufactured using a convex roll 3, which has a circular arc-shaped convex surface on which numerous small square convex portions are arranged in a regular (grid-like) pattern.By forming numerous small square concave portions in a regular (grid-like) pattern in the area pressed down from both sides by the convex roll 3, plastic processing is applied uniformly to the center of the deformed steel bar R, correcting any twisting that occurs in the deformed steel bar R.

[0022] This method for suppressing twisting of deformed steel bars has the following effects. 1. When forming the protrusions S with the protrusion forming roll 2, the entrance side is not tilted in the opposite direction, but is rolled symmetrically to make the shoulder dimensions uniform, and after forming the protrusions S, the convex roll 3 is used. Furthermore, by rolling down the portions of the deformed steel bar R where no protrusions S are formed from both sides and applying plastic processing to the center of the deformed steel bar R, the twist that occurs in the deformed steel bar R is corrected, and thus, when manufacturing the deformed steel bar R, the minimum amount of plastic processing necessary can be applied to the center of the deformed steel bar R using a simple mechanism, and the protrusions S of the deformed steel bar R, which had protrusions formed in a previous process, are not excessively deformed, so that the shape of the deformed steel bar R can be improved with good dimensional accuracy while suppressing the twist that occurs in the deformed steel bar R. In particular, by using a convex roll 3 in which a large number of small protrusions and / or small recesses are regularly arranged on the surface of the arc-shaped convex portion, and by regularly forming a large number of small recesses and / or small protrusions in the portion rolled down from both sides by the convex roll 3, plastic processing is applied uniformly to the center of the deformed steel bar R, and it is possible to eliminate, for example, the strong twist that occurs when rolling under strong pressure so that the protrusions S become high. 2. By forming a groove H with an arc-shaped cross-sectional shape extending in the longitudinal direction of the reinforcing bar material R0 at a 180° symmetrical position on the peripheral surface of the reinforcing bar material R0 using a groove-forming rolling roll 1, the center of the deformed steel bar R can be stably guided to the convex roll 3. 3. Since the deformed steel bar R comes into hot contact with the convex roll 3 having an arc-shaped cross section, no roughening occurs on the side surface of the deformed steel bar R, and the surface quality can be improved. 4. The small recesses (and / or small protrusions) h formed on the surface of the grooves of the deformed steel bar R can have a scale function that indicates the longitudinal dimension of the deformed steel bar R. Specifically, in the deformed steel bar R shown in Figures 4 and 5, a convex roll 3 is used in which a large number of small protrusions, each 2 mm long (1 to 10 mm, preferably 1 to 5 mm, more preferably 1 to 3 mm) and 1 mm high (0.5 to 5 mm, preferably 0.5 to 3 mm, more preferably 0.5 to 2 mm), are regularly arranged at intervals of 2 mm (0.5 to 5 mm, preferably 0.5 to 3 mm, more preferably 0.5 to 2 mm), on the surface of a convex portion having an arc shape with a radius of 25 mm (R10 to 50 mm, preferably R15 to 40 mm, more preferably R20 to 30 mm), and small recesses h having a length of 2 mm and a depth of 0.5 mm are formed at intervals of 2 mm. In addition, the shape, size, and direction of the small recesses (and / or small protrusions) h to be formed can be made different every 10 mm (100 mm, 1000 mm, etc.). 5. In conventionally used deformed steel bars R, as shown in Figure 6, when protrusions S are formed using a protrusion-forming roll 2, material is bitten off, resulting in the formation of ribs Ri extending in the longitudinal direction of the deformed steel bar R. Because these ribs Ri are not constrained during forming, their protrusion height varies, which can cause variations in processing accuracy, for example, when bending the deformed steel bar R. After forming the protrusions S, a convex roll 3 is used to press down from both sides the areas of the deformed steel bar R where the protrusions S are not formed, and plastic processing is applied to the center of the deformed steel bar R, resulting in a ribless shape in which no ribs Ri are formed. This eliminates the cause of variations in processing accuracy when bending the deformed steel bar R. Furthermore, when a ribless deformed steel bar R is sheared with a flat blade in a stable position when placed on a flat surface (laying it on its side with the ribless portion facing up and down), the flat blade can cut with high reproducibility without crushing the protrusions S. Incidentally, in the case of a deformed steel bar R on which ribs Ri are formed, the flat blade always hits the protrusion S first, crushing the protrusion S and causing it to deform, which then causes a crack and shear, resulting in what is known as a bent nose. However, in the case of a deformed steel bar R with a ribless shape, this problem is eliminated, and a deformed steel bar R with high cutting performance can be obtained.

[0023] The above describes the method for suppressing twisting of deformed steel bars according to the present invention based on its examples, but the present invention is not limited to the configurations described in the above examples, and the configuration can be changed as appropriate within the scope of the invention. [Industrial Applicability]

[0024] The method for suppressing twisting of deformed steel bars of the present invention is a simple mechanism that suppresses twisting that occurs in deformed steel bars when manufacturing deformed steel bars by improving the shape of the rolls that hold the deformed steel bars at the exit stand, and can improve the shape of the deformed steel bars. It can be suitably used for this purpose. [Explanation of symbols]

[0025] 1 Groove forming roll 2. Roll for forming protrusions (roll for forming thread shapes) 3 Convex roll 4 Run-in Roller 5 Breaking Plate H Groove h Small concave (small convex) R deformed steel bar R0 Rebar material S Protrusion (screw-like node) Rib

Claims

1. A method for suppressing twist in a deformed steel bar, in which a deformed steel bar on which protrusions have been formed by a protrusion-forming roll of a protrusion-forming rolling mill is plastically deformed using a pair of rolls installed downstream of the protrusion-forming rolling mill, thereby correcting twist that occurs in the deformed steel bar, As a subsequent step to the step of forming protrusions with the protrusion-forming rolling rolls, a pair of rolls are installed downstream of the protrusion-forming rolling mill, and convex rolls having a convex cross section with an arc-shaped cross section and a large number of small convex portions and / or small concave portions formed on the surface of the convex portion with an arc-shaped cross section are used, and the portions of the deformed steel bar where no protrusions are formed and the concave grooves with an arc-shaped cross section are pressed down from both sides with the convex portions and small convex portions and / or small concave portions of the convex rolls, and plastic processing is applied to the center of the deformed steel bar, thereby correcting the twist that occurs in the deformed steel bar. A method for suppressing twisting of deformed steel bars.

2. A method for suppressing twisting of deformed steel bars as described in claim 1, characterized in that the small recesses and / or small protrusions formed on the surface of the grooves of the deformed steel bars by the small protrusions and / or small recesses have a scale function that displays the longitudinal dimensions of the deformed steel bars.

3. The method for suppressing twisting of a deformed steel bar according to claim 1 or 2, characterized in that no ribs are formed on the surface of the deformed steel bar on which the recessed grooves are formed.

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