JP2011025308A - Method for manufacturing steel bar - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a steel bar capable of preventing the occurrence of twist in a wire rod drawn from a coil, and straightening the bend of the wire rod in the direction where straightening is needed, securely, at room temperature. <P>SOLUTION: In a method for manufacturing a steel bar, a steel bar 2 is manufactured after cold straightening is performed on a wire rod 1 drawn from a coil 3 into which the wire rod 1 is spirally wound by hot rolling. In the method, cold straightening is performed in the following way: a piece of the wire rod 1 drawn from the coil 3 is held to restrict twist by a pair of pinch rolls 4 disposed right behind the position where the wire rod 1 is drawn from the coil 3, and, the bend of the wire rod 1 whose twist is restricted is straightened by plurality of straightening rollers 5 arranged in the downstream side of the straightening rollers. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a steel bar, in which a steel bar is manufactured after the wire is drawn out from a coil wound in a spiral shape by hot rolling and cold-corrected.

  As shown in FIG. 7, in manufacturing the steel bar 2, the steel bar 2 is manufactured by drawing the wire 1 from the coil 3 in which the wire 1 is spirally wound by hot rolling and cutting it to a standard length. Has been performed conventionally. However, the wire 1 drawn out from the spiral coil 3 is subject to cold correction because a spiral bend is formed when the wire 1 is wound as the coil 3 by hot rolling.

  In this cold straightening, in the conventional steel bar manufacturing method, as shown in FIG. 7, the wire 1 drawn from the coil 3 is sandwiched between a pair of pinch rolls 4 provided in a straightening machine (not shown). After that, it has been generally performed by a method of correcting with a plurality of correction rollers 5 arranged in a staggered pattern.

  However, since the supply stand (not shown) in which the coil 3 is arranged and the straightening machine provided with the pinch roll 4 are spaced apart from each other, the wire 1 is pulled out from the coil 3 until the pinch roll 4 is reached. The wire 1 was often twisted before reaching the pinch roll 4. Moreover, the twist of the wire 1 varies even within the bundle of coils 3, and the coil 1 is wound in a state in which the direction of the wire 3 is constantly fluctuating, and the pinch roll 4 is kept in a state where the wire 1 drawn from the coil 3 is twisted. Had to reach. In such a case, the correction of the bending of the wire 1 performed by the correction roller 5 provided on the downstream side of the pinch roll 4 is performed in a state where the wire 1 is twisted. It was supposed to be done in a different direction.

  That is, the wire 1 is spirally wound in the hot rolling step of the previous step, and the wire 1 constituting the coil 3 has a three-dimensional bend. Therefore, when the wire 1 is pulled out from the coil 3, the wire 1 is pulled out while rotating (twisting). On the other hand, the correction roller 5 is fixed to a correction machine or the like. The wire 1 to be straightened and the straightening roller 5 that performs straightening have the above-described relationship. Therefore, the wire 1 is straightened while changing its orientation in the longitudinal direction, together with the variation in winding of the coil 3. Therefore, correction is performed in various directions, and correction that matches the circumferential direction of the coil 3 cannot be reliably performed. Therefore, even after correction with the correction roller 5, the three-dimensional bending remains in the wire 1, and as a result, the spiral shape of the coil 3 remains in the corrected wire 1.

  For example, in Patent Document 1, a thin steel bar rolled to a predetermined diameter of 30 mm or less from a billet is wound into a coil shape in a rolling process, and the wound coil is wound on a supply stand on a separate line different from the rolling process. Return and straighten with a multi-roll rough straightening machine with multiple sets of straightening rolls, cut to a predetermined length with a high-speed cutting machine, and then correct to a predetermined straightening accuracy with a two-roll straightening machine behind it. A method for manufacturing a thin steel bar is described.

  The method for manufacturing a thin steel bar described in Patent Document 1 is a normal hot-rolled steel bar, and is a method applied to correct bending. When this method is applied to correct the bending of a wire wound in a coil shape, the radius of curvature of the wire wound in a coil shape is extremely small compared to that of a steel bar. Requires a straightening roller. Moreover, even if it uses many correction | amendment rollers, it cannot correct reliably, but straightness will fall compared with a hot-rolled steel bar.

  As a method of correcting the bending of the wire, in addition to the method described above, a method of drawing a die after straightening to a certain extent by a straightening roller and a method of correcting hotly can be exemplified. Has the problem that the speed for drawing cannot be improved and that the die needs to be replaced, and the latter has the problem that the cost for heating and the mechanical properties are impaired, It is not an appropriate correction method.

JP-A-11-33619

  The present invention has been made as a solution to the above-described conventional problems, and can suppress the occurrence of twist in the wire drawn from the coil in which the wire is spirally wound by hot rolling. It is an object of the present invention to provide a method of manufacturing a steel bar that can bend straightly in a direction that requires straightening, and that can be carried out cold.

  The invention according to claim 1 is a steel bar manufacturing method for manufacturing a steel bar after pulling out the wire from a coil in which the wire is spirally wound by hot rolling and performing cold straightening. With a pair of pinch rolls arranged at a position immediately after the wire is drawn out, the one wire drawn out from the coil is sandwiched to restrain the twist, and the bending of the wire to which the twist is restrained is The steel bar manufacturing method is characterized in that the cold straightening is performed by straightening with a plurality of straightening rollers arranged on the downstream side.

  According to a second aspect of the present invention, in the steel bar according to the first aspect, an imaginary plane that includes the central axis of the coil and that is orthogonal to the drawing direction of the wire passes through a part of the pair of pinch rolls. It is a manufacturing method.

  A third aspect of the present invention is the steel bar according to the first aspect, wherein a virtual plane including the central axis of the coil and perpendicular to the drawing direction of the wire passes through the rotation axis of the pair of pinch rolls. It is a manufacturing method.

  According to a fourth aspect of the present invention, one pair or two or more pairs of pinch rolls are further arranged between the plurality of straightening rollers, and the twisting of the wire rod and the correction of the bending are repeatedly performed. 4. The steel bar manufacturing method according to any one of claims 1 to 3, wherein the straightening is performed.

  According to a fifth aspect of the present invention, a plurality of shafts having a rotation axis inclined at 90 ° with respect to a rotation axis of the plurality of correction rollers and inclined at 90 ° with respect to a drawing direction of the wire rod on the downstream side of the plurality of correction rollers. The method of manufacturing a steel bar according to any one of claims 1 to 4, wherein an auxiliary straightening roller is disposed.

  A sixth aspect of the present invention is the wire rod that has been bent by cold correction according to any one of the first to fifth aspects, wherein the plurality of correction pieces having insertion holes are substantially straight. In order to further correct the bending of the wire rod by rotation of the rotary piece type straightening machine, sequentially inserted through the insertion hole of the rotary piece type straightening machine incorporated in the state of being arranged substantially in series. It is a manufacturing method of the steel bar to be made.

  The invention according to claim 7 is a multi-roll straightening in which a plurality of straightening rollers are arranged after cutting the wire obtained by correcting the bending by the method according to any one of claims 1 to 6 into a steel bar. This is a method of manufacturing a steel bar, which is passed through a machine and further corrects the bending of the steel bar.

  According to an eighth aspect of the present invention, there is provided a drum-shaped roller in which the center portion of the pressing surface is recessed after the wire having been bent by the method according to any one of the first to sixth aspects is cut into a standard length by cutting it into a bar steel. And a drum-shaped roller in which the center portion of the pressing surface swells is passed through a pair of drum correcting machines, and the bending of the steel bar is further corrected.

  According to the method for manufacturing a steel bar according to claim 1 of the present invention, one wire rod drawn out from a coil in which the wire rod is spirally wound up by hot rolling is used with a pair of pinch rolls immediately after being drawn out from the coil. Therefore, it is possible to prevent the wire from being twisted and to correct the subsequent bending of the wire in a direction that requires correction. And since it can correct | amend cold, the problem that the cost for heating and a mechanical property will be impaired does not generate | occur | produce.

  According to the method for manufacturing a steel bar according to claim 2 of the present invention, the virtual plane that includes the central axis of the coil and that is perpendicular to the drawing direction of the wire rod is disposed so as to pass through a part of the pair of pinch rolls. One wire immediately after being pulled out from the coil can be reliably sandwiched between a pair of pinch rolls, and the occurrence of twisting of the wire can be more reliably prevented.

  According to the method for manufacturing a steel bar according to claim 3 of the present invention, the virtual plane including the central axis of the coil and perpendicular to the drawing direction of the wire rod is arranged so as to pass through the rotation axis of the pair of pinch rolls. One wire just after being pulled out of the coil can be more reliably sandwiched between a pair of pinch rolls, and the occurrence of twisting of the wire can be more reliably prevented.

  According to the method for manufacturing a steel bar according to claim 4 of the present invention, since the constraint of the twisting of the wire with the pinch roll and the correction of the bending of the wire with the straightening roller are repeated a plurality of times, the bending of the wire is corrected. This can be done more reliably.

  According to the method for manufacturing a steel bar according to claim 5 of the present invention, the minor correction in the axial direction at the time of winding the coil of the wire can also be performed by the auxiliary correction roller.

  According to the method for manufacturing a steel bar according to claim 6 of the present invention, in addition to the cold correction according to any one of claims 1 to 5, the bending of the wire rod is also performed because of the correction of the bending by the rotary piece type straightening machine. Can be more reliably corrected.

  According to the method for manufacturing a steel bar according to claim 7 of the present invention, since the bending is corrected even after the wire is cut into a steel bar, the bending of the manufactured steel bar can be corrected more reliably.

  According to the method for manufacturing a steel bar according to claim 8 of the present invention, since the bending is corrected even after the wire is cut into the steel bar, the bending of the manufactured steel bar can be corrected more reliably.

It is a side view for demonstrating the process of embodiment of Claim 1-3 of this invention. It is a side view for demonstrating the process of embodiment of Claim 4 of this invention. It is a side view for demonstrating the process of embodiment of Claim 5 of this invention. It is a longitudinal cross-sectional view which shows the outline | summary of a rotary piece type corrector. It is a side view which shows the outline | summary of a multi-roll straightening machine. It is a side view which shows the outline | summary of a drum straightening machine. It is a side view for demonstrating the process of a prior art example. It is a side view for demonstrating bending amount (delta) of a wire (steel bar), (a) shows the example of meandering bending, (b) shows the example of arc-shaped bending. The measurement result of bending amount (delta) of the bar steel in an Example is shown, It is a graph which shows the variation of bending amount (delta) of the bar steel manufactured with the manufacturing method of the bar steel of Claims 1-3. FIG. 7 is a graph showing the measurement result of the bending amount δ of the steel bar in the example, and showing the variation in the bending amount δ of the steel bar manufactured by the method for manufacturing a steel bar according to claim 4. FIG. 9 is a graph showing the measurement result of the bending amount δ of the steel bar in the example, and is a graph showing variation in the bending amount δ of the steel bar manufactured by the method for manufacturing a steel bar according to claim 5. FIG. 9 is a graph showing the measurement result of the bending amount δ of the steel bar in the example, and showing the variation in the bending amount δ of the steel bar manufactured by the method for manufacturing a steel bar according to claim 6. FIG. 9 is a graph showing the measurement result of the bending amount δ of the steel bar in the example, and showing the variation in the bending amount δ of the steel bar manufactured by the method for manufacturing a steel bar according to claim 7. FIG. 9 is a graph showing the measurement result of the bending amount δ of the steel bar in the example, and showing the variation in the bending amount δ of the steel bar manufactured by the method for manufacturing a steel bar according to claim 8. It is a graph which shows the measurement result of bending amount (delta) of the bar steel in an Example, and shows the variation in bending amount (delta) of the bar steel manufactured with the manufacturing method of the conventional steel bar. It is a side view for demonstrating the process of embodiment using a rotary piece type corrector.

  The inventors of the present invention have made sure that the wire drawn out from the coil in which the wire is spirally wound by hot rolling is not twisted, and correct the subsequent bending of the wire in the direction that requires correction. With the aim of finding a method for producing steel bars from wire rods that can be carried out, we have been diligently experimenting and researching.

  As a result, a pair of pinch rolls that restrain the twisting of the wire is placed at a position immediately after the wire is pulled out of the coil, and a single wire just after being pulled out of the coil is sandwiched between the wires. The present inventors have found that the generated twist can be reliably restrained, and have completed the present invention. In addition, it is desirable that a virtual plane that includes the central axis of the coil and that is perpendicular to the drawing direction of the wire rod pass through a part of the pair of pinch rolls, and further includes the central axis of the coil, and It was also confirmed that it is more desirable to arrange the virtual plane perpendicular to the wire drawing direction so as to pass through the rotation axes of the pair of pinch rolls.

  However, the wire is spirally wound by hot rolling, and as described above, the wire is slightly bent in the axial direction. Therefore, if correction is performed with a plurality of correction rollers arranged on the downstream side of the pinch roll, there is a possibility that a new bend occurs during correction. When such bending occurs, there is a possibility that a slight spiral shape may remain in the straightened wire. In order to eliminate such a possibility, a countermeasure was provided by further providing a pinch roll between the plurality of correction rollers.

  Further, it is not possible to correct a slight bending in the axial direction when winding a coil of a wire by simply providing a pinch roll between a plurality of correction rollers. In order to correct this slight bending in the axial direction, a plurality of secondary correction rollers having a rotation axis inclined by 90 ° with respect to the rotation axes of the correction rollers are arranged downstream of the correction rollers. .

  Manufacture of steel bars by the method as described above makes it possible to manufacture steel bars with good straightness, but residual stress may be a problem depending on the application. For the improvement, after correcting the bending of the wire by the method described above, the straightness can be further improved by further performing the rotary piece type correction, the multi-roll correction, and the drum correction, and the residual stress is also improved. Can be reduced.

  Hereinafter, the present invention will be described in more detail based on embodiments shown in the accompanying drawings.

  FIG. 1 is a side view for explaining a process according to an embodiment of the present invention. In this embodiment, first, in the hot rolling step of the previous step, the wire 1 is wound up spirally in a winder and transferred to a supply stand or the like. The steel bar 2 is manufactured by drawing the wire 1 from the coil 3 wound by the winder and performing cold correction.

  In the present invention, the one wire 1 drawn from the coil 3 is sandwiched between the pair of pinch rolls 4 immediately after being drawn, so that twisting of the drawn wire 1 can be suppressed. In the embodiment shown in FIG. 1, the rotation axis of the pinch roll 4 includes the central axis of the coil and is disposed on a virtual plane C perpendicular to the drawing direction of the wire, so that the wire 1 is drawn from the coil 3. In this state, the pair of pinch rolls 4 can be securely sandwiched and the twist of the wire 1 can be restrained.

  As shown in FIG. 1, the pinch roll 4 does not necessarily have its rotational axis positioned on the virtual plane C, and any part of the pinch roll 4 may be positioned on the virtual plane C. . Thus, by arrange | positioning the pinch roll 4, the twist of the wire 1 can be restrained reliably. In addition, a part of the pinch roll 4 does not necessarily have to be arranged on the virtual plane C. If the position can restrain the twist of the wire 1 immediately after being pulled out from the coil 3, the wire rod is drawn from above the virtual plane C. The pinch roll 4 may be disposed at a position slightly separated from the front and rear in the pull-out direction.

  In a state where the twist is restrained by the pinch roll 4, the wire 1 is further sent to the downstream side, pressed by a plurality of straightening rollers 5 arranged in a staggered manner, and wound as a coil 3 in a hot rolling process. This corrects the spiral bend that occurs during the process. In other words, since the bending of the wire 1 is corrected by the correction roller 5 in a state where the twist is constrained, the correction in the direction that originally requires correction, that is, the circumferential direction of the coil 3 is surely performed. it can.

  The wire 1 that has finished the correction of the bending is further sent to the downstream side, and is cut into a standard length by a cutting machine 9 (shown in FIG. 16), whereby the target steel bar 2 is manufactured.

  The above is the description of the embodiment shown in FIG. 1. As shown in FIG. 2, as shown in FIG. By repeatedly restraining the twist of 1 and correcting the bending of the wire 1, the bending of the wire 1 can be corrected more reliably.

  Although FIG. 2 shows an embodiment in which only one pair of additional pinch rolls 4 is provided, two or more pairs of additional pinch rolls 4 may be provided. In this case, each pinch roll 4 must be disposed between the straightening rollers 5, and a pair of pinch rolls 4 that restrain the twist of the wire 1 and a straightening roller 5 that straightens the bending of the wire 1 downstream thereof. Must be provided as a set.

  Moreover, even if the bending of the wire 1 is corrected by each method described above, the circumferential direction generated when the coil 3 of the wire 1 is wound can be corrected, but the axial direction when the coil 3 of the wire 1 is wound Some bends cannot be corrected. As shown in FIG. 3, the bending in the axial direction is inclined by 90 ° with respect to the rotation axis of the plurality of correction rollers 5 on the downstream side of the plurality of correction rollers 5 and is 90 ° with respect to the drawing direction of the wire 1. Correction can be made by arranging a plurality of secondary correction rollers 10 having inclined rotation axes.

  When the straightening of the wire 1 is corrected by each method described above, but the correction is insufficient, or when it is necessary to manufacture the steel bar 2 requiring higher straightness, FIG. By providing the rotary piece type straightening machine 6 shown on the further downstream side of the plurality of straightening rollers 5, the bending of the wire 1 can be more reliably corrected.

  Inside the rotary piece type straightening machine 6, a plurality of straightening pieces 6a formed with insertion holes are built in a state of being substantially in series so that the insertion holes are arranged in a substantially straight line. In addition, the substantially linear shape shown here indicates that the insertion holes are aligned in the same direction. Specifically, as shown in FIG. 4, the insertion holes of the correction pieces 6a are intentionally shifted. Deploy. Further, the main body 6b of the rotary piece type straightening machine 6 has a cylindrical structure in which both end faces are closed, and concentric insertion holes are formed on both end faces. The plurality of correction pieces 6a described above are arranged in series in the hollow portion of the main body 6b, and each is incorporated with a space therebetween, but each insertion hole is arranged from the surface side of the main body 6b by a position adjusting screw 6c. It is possible to adjust the position.

  By inserting the wire 1 sequentially into the insertion hole of the rotary piece type straightening machine 6 and rotating the rotary piece type straightening machine 6 together with the main body 6b, the bending of the wire 1 can be more reliably corrected. When the bending of the wire 1 is corrected by the rotary piece type straightening machine 6, the bending of the wire 1 cannot be completely corrected in the upstream process, and residual stress is generated. In addition, since the rotary piece type straightening machine 6 can give plastic deformation in the twist direction, the residual stress can be removed.

  After correcting the bending of the wire 1 by each of the above methods, the wire 1 is further sent to the downstream side, and the target bar 2 is manufactured by cutting it to a standard length with a cutting machine 9 (shown in FIG. 14). However, the bending of the steel bar 2 is corrected as necessary. The correction can be performed using the multi-roll correction machine 7 shown in FIG. 4 or the drum correction machine 8 shown in FIG. Even if the residual stress is removed in the state of the long wire 1, a problem may remain in the straightness at the stage where the steel bar 2 is formed. The straightening after making these steel bars 2 is carried out mainly in order to improve the straightness of the steel bars 2.

  The multi-roll straightening machine 7 is a straightening machine provided with a plurality of straightening rollers 7a, and the bending of the steel bar 2 can be corrected by passing the steel bar 2 between the straightening rollers 7a arranged in a staggered manner. In addition, 7b shown in FIG. 5 is a pinch roll provided at the entrance.

  The drum straightening machine 8 is a straightening machine in which a drum-shaped roller 8a having a concave center part of the pressing surface and a drum-shaped roller 8b having a central part of the pressing surface swelled in pairs and arranged at different angles. By passing the bar 2 between the shape roller 8a and the drum-shaped roller 8b, the bending of the bar 2 can be corrected.

  Cold straightening was carried out by drawing the wire from a coil in which the wire was spirally wound by hot rolling. The cold correction is performed based on the method described in claims 3 to 8, respectively, and an example in which the cold correction is performed by the method described in claims 1 to 3 is described in the first and fourth embodiments. Example in which cold correction is performed by the method Example 2, in which cold correction is performed by the method described in claim 5, Example 3 in which cold correction is performed by the method described in claim 6, and example 6 Example 4 and Example 7 in which cold correction was carried out by the method described in claim 7 were carried out as Example 5 and Example 6 in which cold correction was carried out by the method described in claim 8 were carried out. The example which did not do was made into the comparative example.

  The pair of pinch rolls added in the second embodiment is a pair, and in the third to sixth embodiments, the cold correction performed first is performed by the method shown in claim 3. Moreover, in Example 5, 6, the bending correction of the wire with the rotary piece type | formula correction machine 6 is implemented similarly to Example 4, and the wire 1 of Examples 4-6 is cut | disconnected in FIG. The process up to the bar 2 is shown. In addition, 6d is a pinch roll disposed on the upstream and downstream sides of the rotary piece type straightening machine 6.

  The diameter of the wire obtained by hot rolling is φ22 mm, and in each of the examples and comparative examples, 100 steel bars cut into 6 m were manufactured, and the bending amount δ shown in FIG. Data was obtained by measuring. In each example and comparative example, data on two types of steel types: S55C and SUJ2 were obtained. Note that S55C is in a hot-rolled state, SUJ2 is in a state after spheroidizing heat treatment, and pickling, coating treatment, etc. are not performed.

  A bending amount δ of 2 mm or less is a bending amount that does not cause a problem as a steel bar, and in a stricter standard, the standard is 1 mm or less.

  9 shows the measurement results of Example 1, FIG. 10 shows the measurement results of Example 2, FIG. 11 shows the measurement results of Example 3, FIG. 12 shows the measurement results of Example 4, and FIG. FIG. 13 collectively shows the measurement results of Example 6, and FIG. 15 shows the measurement results of the comparative example. In addition, the left side of each bar graph shows an example using S55C and the right side using SUJ2 as materials.

  In the comparative example, the amount of bending δ varied widely, and a majority exceeding 2 mm was measured regardless of the steel type, and a very large bending of 4.5 mm or more was also measured. When S55C and SUJ2 are compared, it can be confirmed that the bending of the SUJ2 having a higher deformation resistance is larger. In addition, it is considered that the large variation in the measurement result was caused by the variation in the bending from the coil drawing point to the pinch roll. In addition, it tried to straighten the cut steel bar through a multi-roll straightening machine and a drum straightening machine, but the steel bar with a large bend could not be passed through the straightening machine.

  On the other hand, in Examples 1 to 6, the measured bending amount δ is 2 mm or less, which is a bending amount that does not cause a problem as a steel bar, passes through the central axis of the coil and is orthogonal to the wire drawing direction. With a pair of pinch rolls placed on the wire, a single wire drawn from the coil is pinched to constrain the torsion, thereby ensuring that the wire is bent in the direction that requires correction in the subsequent cold correction. It can be seen that it can be corrected.

  In Example 1, both the measured bending amount δ of S55C and SUJ2 is 2 mm or less, which is considered to be a bending amount that does not cause a problem as a steel bar. In Example 2, 93% in S55C and 54% in SUJ2 It can be corrected to a bending amount δ of 1 mm or less. From this result, it can be seen that the bending of the wire rod can be more reliably corrected by repeating the constraint of the twist of the wire rod with the pinch roll and the correction of the bending of the wire rod with the correction roller a plurality of times.

  Further, in Example 3, the total number in S55C and the total number in SUJ2 of 98% can be corrected to a bending amount δ of 1 mm or less. From this result, a plurality of secondary correction rollers having a rotation axis inclined by 90 ° with respect to the rotation shafts of the correction rollers are arranged on the downstream side of the plurality of correction rollers to correct the axial direction when winding the coil of the wire rod. It can be seen that the straightening of the bending of the wire can be more reliably performed by carrying out the above together.

  Further, in Example 4, the total number can be corrected to S55C and the bending amount δ of 1 mm or less can be corrected by 88% in SUJ2. From this result, it is understood that the bending of the wire rod can be more reliably corrected by performing the correction of the bending with the rotary piece type correcting machine.

  Further, in Example 5 and Example 6, the measured bending amount δ is 1 mm or less in both S55C and SUJ2. That is, it can be seen that the bending of the manufactured steel bar can be more reliably corrected by correcting the bending with a multi-roll correcting machine or a drum correcting machine after correcting the bending with the rotary piece type correcting machine.

DESCRIPTION OF SYMBOLS 1 ... Wire rod 2 ... Steel bar 3 ... Coil 4 ... Pinch roll 5 ... Correction roller 6 ... Rotation piece type correction machine 6a ... Correction piece 6b ... Main body 6c ... Position adjustment screw 6d ... Pinch roll 7 ... Multi-roll correction machine 7a ... Correction roller 7b ... Pinch roll 8 ... Drum straightening machine 8a ... Drum-shaped roller 8b ... Drum-shaped roller 9 ... Cutting machine 10 ... Sub straightening roller A ... Center axis B ... Pull-out direction C ... Virtual plane

Claims (8)

In the method of manufacturing a steel bar, after the wire is drawn out in a spiral form by hot rolling, after the wire is drawn out and subjected to cold correction,
With a pair of pinch rolls arranged at a position immediately after the wire is drawn from the coil, the one wire drawn from the coil is sandwiched to restrain the twist,
A method for manufacturing a steel bar, wherein the cold straightening is carried out by correcting the bending of the wire, the twist of which is constrained, with a plurality of straightening rollers arranged downstream thereof.   2. The method for manufacturing a steel bar according to claim 1, wherein a virtual plane including a central axis of the coil and perpendicular to a drawing direction of the wire passes through a part of the pair of pinch rolls.   The method for manufacturing a steel bar according to claim 1, wherein a virtual plane including a central axis of the coil and perpendicular to a drawing direction of the wire passes through a rotation axis of the pair of pinch rolls. Between the plurality of straightening rollers, one pair or two or more pairs of pinch rolls are arranged,
The method of manufacturing a steel bar according to any one of claims 1 to 3, wherein the cold straightening is performed by repeatedly performing twisting restraint and bending correction of the wire.   On the downstream side of the plurality of correction rollers, a plurality of sub correction rollers having a rotation axis inclined by 90 ° with respect to the rotation axes of the plurality of correction rollers and inclined by 90 ° with respect to the drawing direction of the wire rod are arranged. The method for manufacturing a steel bar according to any one of claims 1 to 4, wherein: A wire rod that has been bent by cold correction according to any one of claims 1 to 5,
A plurality of correction pieces in which insertion holes are formed are sequentially inserted into the insertion holes of the rotary piece type straightening machine incorporated in series so that the insertion holes are arranged substantially linearly,
A method of manufacturing a steel bar, wherein the bending of the wire is further corrected by rotation of the rotary piece type straightening machine.   A wire rod whose curvature has been corrected by the method according to any one of claims 1 to 6 is cut into a steel bar by cutting it into a standard length, and then passed through a multi-roll straightening machine in which a plurality of straightening rollers are arranged. A method of manufacturing a steel bar, characterized by correcting bending.   A wire rod whose curvature has been corrected by the method according to any one of claims 1 to 6 is cut into a standard length to form a steel bar, and then the hourglass roller having a recessed central portion of the pressing surface, and the central portion of the pressing surface are A method of manufacturing a steel bar, comprising: passing through a drum straightening machine in which swelled drum-shaped rollers are arranged in pairs, and further correcting the bending of the steel bar.

Images