JP5155741B2 - Manufacturing method of round steel bar - Google Patents

Description

  The present invention relates to a method for manufacturing a round steel bar. More specifically, the present invention relates to a rolling method for rolling a steel piece to obtain a round bar steel.

  A rolling method is widely known as a method for producing a round steel bar. A steel ingot is obtained through refining and ingot forming processes. The steel ingot is divided and rolled to obtain a steel slab. This steel slab is rolled to obtain a round bar steel.

  FIG. 6 is a conceptual diagram showing a conventional round bar steel rolling facility 100. The rolling equipment 100 includes a block mill 102 and a steel slab mill 104. In the block mill 102, the steel ingot 106 is rolled by a rolling roll 108 to obtain a steel slab 110. In the billet rolling machine 104, the steel piece 110 is rolled by a rolling roll 112 to obtain a round bar steel 114.

  FIG. 7 is a process diagram of steel slab rolling in which a round steel bar 114 is obtained by rolling a conventional steel slab 110. The steel piece 110 is hot-rolled. The steel piece 110 having a rectangular section is passed through a substantially elliptic rolling hole of the rolling roll 112 and rolled into a steel piece 116 having an elliptical section. The steel piece 116 is passed through a substantially circular rolling hole of the rolling roll 112 and rolled into a round bar steel 114 having a circular cross section. In this way, a round steel bar 114 having a circular cross section is obtained from the steel piece 110.

  In the steel piece 110 having a large cross section, a biting failure into the rolling roll 112 may occur during rolling. In addition, wrinkles may occur on the outer peripheral surface of the rolled round steel bar 114. This bar is a bar that continues in a cover shape in the longitudinal direction of the round steel bar 114. This spear is said to be Hege.

  There is a rolling method in which a steel slab having a circular cross section is obtained by rolling a steel slab having an octagonal cross section instead of the steel slab 110 having a rectangular cross section. In this method, an octagonal cross-section steel slab is rolled into an elliptical steel slab 116. Rolled from an elliptical steel piece 116 to a round steel bar 114. In this rolling method, the occurrence of biting into the rolling roll 112 and the occurrence of lashes are suppressed. In this method, the cross-section of the steel slab is rolled into an octagon by split rolling.

  As shown in FIG. 6, a block mill generally includes a rolling roll 108 having a rectangular cross section. When rolling into a steel piece having an octagonal cross section, the rolling roll 108 is changed to a rolling roll 118 that rolls into an octagonal cross section. It takes time to change the type of the rolling rolls 108 and 118. This type change reduces production efficiency.

Japanese Unexamined Patent Application Publication No. 2004-188461 discloses a method of rolling into a steel piece having an octagonal cross section with a block mill.
JP 2004-188461 A

  In the conventional rolling method, the product yield decreases without the rolling roll 118 that rolls the cross section into an octagon. Moreover, when using the rolling roll 118, production efficiency falls by mold change.

  An object of the present invention is to provide a production method capable of efficiently obtaining a round steel bar having excellent quality.

  The rolling method according to the present invention for hot rolling an ingot to obtain a round bar steel includes the following rolling steps. In the first rolling step, the steel ingot is passed through a substantially rectangular rolling hole formed by a pair of rolling rolls to obtain a steel slab having a substantially rectangular cross section. In the second rolling step, the steel slab is passed through a substantially diamond-shaped or substantially elliptical rolling hole formed by a pair of rolling rolls, and the ridge of the steel slab is rolled. In the third rolling step, the steel slab is passed through a substantially elliptical rolling hole formed by a pair of rolling rolls to obtain a steel slab having a substantially elliptical cross section. In the fourth rolling step, the steel slab is passed through a substantially circular rolling hole formed by a pair of rolling rolls to obtain a steel slab having a substantially circular cross section.

  Preferably, prior to the second rolling step, the method further includes a step of adjusting the distance between the pair of rolling rolls forming the approximately rhombic or approximately elliptical rolling holes in accordance with the size of the cross section of the steel slab.

  The rolling equipment according to the present invention includes a rolling mill for rolling a steel ingot into a steel piece having a rectangular cross section, a ridge rolling machine for rolling the ridge of a steel slab having a rectangular cross section, and the ridge part being rolled. A billet rolling mill for rolling the billet into a predetermined cross section such as a round bar steel. These rolling mills are provided with a pair of rolling rolls, and are rolled by the pair of rolling rolls. A pair of rolling rolls of a rolling mill that rolls a ridge portion of a steel piece is formed with a substantially rhombic or substantially elliptical rolling hole and a through hole that passes without rolling.

  In the manufacturing method according to the present invention, the occurrence of lashes on the round bar steel is suppressed. The method according to the present invention is excellent in production efficiency.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 is a conceptual view showing a round bar steel rolling facility 2 according to an embodiment of the present invention. The rolling equipment 2 includes a block rolling mill 4, a ridge rolling mill 6, and a steel slab rolling mill 8. The block mill 4 includes a rolling roll 10. The ridge rolling mill 6 includes a rolling roll 12. The billet rolling machine 8 includes a rolling roll 14.

  FIG. 2 is a front view showing the rolling roll 10 of the block mill 4 of FIG. The rolling roll 10 includes a caliber 16. A substantially rectangular rolling hole 18 is formed by the caliber 16 of the pair of rolling rolls 10.

  Fig.3 (a) is the front view by which the rolling roll 12 of the ridge part rolling mill 6 of FIG. 1 was shown. The rolling roll 12 includes a caliber 20 and a caliber 22. The caliber 20 includes a pair of tapered surfaces 24. The tapered surface 24 is a truncated cone-shaped tapered surface. The pair of tapered surfaces 24 are positioned to face each other. The angle θ is an intersecting angle between the pair of tapered surfaces 24 in the front view of FIG. A substantially rhombic rolling hole 26 is formed by the caliber 20 of the pair of rolling rolls 12.

  The caliber 22 shown in FIG. 3A includes a pair of tapered surfaces 28 and a cylindrical surface 30. The tapered surface 28 is a truncated cone-shaped tapered surface. The pair of tapered surfaces 28 are positioned to face each other. The cylindrical surface 30 is located between the pair of tapered surfaces 28. The cylindrical surface 30 is a cylindrical outer peripheral surface parallel to the rotation axis of the rolling roll 12. A through hole 32 is formed by the caliber 22 of the pair of rolling rolls 12.

  FIG.3 (b) is the side view by which the rolling roll 12 of the ridge part rolling mill 6 of FIG. 1 was shown. In FIG. 3B, the upper rolling roll 12 is rotated counterclockwise. The lower rolling roll 12 is rotated clockwise. The steel slab is partially rolled through the rolling hole 26 from the left to the right. Although the upper rolling roll 12 is not shown in the drawing, it can be moved in the vertical direction by a feeding device. The distance between the pair of rolling rolls 12 can be changed by the vertical movement of the upper rolling roll 12. Thereby, the space | interval of the up-down direction of the rolling hole 26 can be changed into a desired space | interval.

  FIG. 4 is a front view showing the rolling roll 14 of the billet rolling machine 8 of FIG. The rolling roll 14 includes a caliber 34 and a caliber 36. A substantially elliptic rolling hole 38 is formed by the caliber 34 of the pair of rolling rolls 14. A substantially circular rolling hole 40 is formed by the caliber 36 of the pair of rolling rolls 14. The rolling roll 14 is formed with both a substantially elliptical rolling hole 38 and a substantially circular rolling hole 40. The steel slab rolling mill 8 provided with this rolling roll 14 serves as both a rolling mill that rolls a cross section of the steel slab into an ellipse and a rolling mill that rolls into a circle. You may form the substantially elliptical rolling hole 38 and the substantially circular rolling hole 40 separately in two rolling rolls. In this case, a rolling mill for rolling the cross section of the steel slab into an ellipse and a rolling mill for rolling into a circle are provided separately.

  FIG. 5 is a flowchart showing an example of a manufacturing method using the rolling equipment of FIG. In this manufacturing method, the steel ingot 42 is obtained through the steps of refining (STEP 1) and ingot forming (STEP 2). The steel ingot 42 is used for the first rolling (STEP 3). In the first rolling, the steel ingot 42 is passed through the rolling hole 18 (see FIG. 2) of the block mill 4 and a steel piece 44 is obtained. This first rolling is referred to as “bulk rolling”.

  This steel piece 44 is subjected to second rolling (STEP 4). In the second rolling, the steel piece 44 is passed through the rolling hole 26 (see FIG. 3A) of the ridge rolling mill 6. The ridge of the steel slab 44 is rolled down by the ridge rolling mill 6 to obtain a steel slab 46. This second rolling is called “ridge rolling”.

  The steel piece 46 is subjected to third rolling (STEP 5). In the third rolling, the steel piece 46 is passed through the rolling hole 38 (see FIG. 4) of the steel piece rolling machine 8. By the third rolling, a steel piece 47 having an elliptical cross section is obtained.

  This steel piece 47 is used for the fourth rolling (STEP 6). In the fourth rolling, the steel piece 47 is passed through the rolling hole 40 (see FIG. 4) of the steel piece rolling machine 8. By the fourth rolling, a round steel bar 48 having a circular cross section is obtained. The round steel bar 48 is rolled into a predetermined cross section by this fourth rolling. The predetermined cross-sectional shape is a predetermined cross-sectional shape of the product. In this embodiment, the circular cross section of the round steel bar 48 is used. The shape of the rolling hole 40 is formed in this circular cross-sectional shape. The third rolling (STEP 5) and the fourth rolling (STEP 6) are collectively referred to as “steel rolling”.

  In this manufacturing method, the ridge portion of the steel piece 44 is reduced in the second rolling (STEP 4). When the steel piece 44 whose ridge portion is not crushed is passed through the rolling hole 38 of the third rolling, it contacts the rolling roll 14 that forms the rolling hole 38 from the ridge portion of the steel piece 44. Since only the ridge portion is in contact with the rolling roll 14, a biting defect is likely to occur in the rolling hole 38. In the steel piece 46 rolled at the ridge, the occurrence of this biting failure is suppressed.

  When the steel piece 44 whose ridge portion is not crushed is passed through the elliptical rolling hole 38, the steel piece 44 is easily rolled so that the ridge portion of the steel piece 44 covers the side surface of the steel piece 44. In the steel slab rolled so that the ridge covers the side surface of the steel slab 44, scabs are generated on the surface rolled into the round bar steel. In the slab 46 that has been ridge-rolled, the ridge is prevented from covering the side surface of the steel slab 46 by rolling. Thereby, generation | occurrence | production of the baldness of the round steel bar 48 is suppressed.

  As described above, the distance between the pair of rolling rolls 12 shown in FIG. 3 can be changed. When the steel piece 44 having a large cross section is ridge-rolled, the upper rolling roll 12 moves upward and is positioned. The distance between the upper rolling roll 12 and the lower rolling roll 12 is adjusted according to the size of the cross section of the steel piece 44 to be ridge-rolled. The pair of rolling rolls 12 can partially roll the ridge portion from the steel piece 44 having a relatively large cross section to the steel piece 44 having a relatively small cross section without exchanging the rolling roll 12. In the ridge rolling of the steel piece 44 having a relatively large cross section, the rolling allowance does not become larger than necessary. Thereby, the load of ridge rolling can be kept relatively small. The ridge rolling with a relatively small load has a short rolling time. Even if this ridge portion rolling step is provided between the block rolling step and the rolling step, the production amount per unit time of the round bar steel 48 is not reduced. The ridge rolling with a relatively small load suppresses the occurrence of biting defects.

  In this embodiment, the angle θ of the rolling roll 12 is 95 °. In this manufacturing method, the angle θ is set to 75 ° to 115 °. By this tapered surface 24, the ridge portion of the steel piece 44 is rolled. The ridge portion of the steel slab 44 is rolled into a preferred chamfered shape by the caliber 20 having the angle θ of 75 ° or more and 115 ° or less. In the caliber 20 having a large angle θ, the amount of change in the vertical spacing of the rolling holes 18 can be reduced when the ridge portion rolling is performed on the large and small steel pieces 44 having different side lengths. The caliber 20 can perform ridge rolling from a steel piece 44 having a smaller cross section to a steel piece 44 having a larger cross section. The caliber 20 has a wide range of cross-sectional sizes of the steel piece 44 that can be ridge-rolled. In this respect, the angle θ is more preferably 80 ° or more, and further preferably 85 ° or more. If the angle θ is too large, the effect of suppressing the biting failure and the reduction of lashes in the subsequent rolling process is reduced. In this respect, the angle θ is more preferably 110 ° or less, and further preferably 105 ° or less.

  A steel piece 46 is obtained through this ridge rolling process. This steel piece 46 is sent to the rolling process. The steel piece 46 is hot rolled. The steel slab 46 is passed through the rolling hole 38 of the rolling roll 14 to obtain a steel slab 47. The steel piece 47 is further passed through the rolling hole 40 of the rolling roll 14 to obtain a round steel bar 48. In this manufacturing method, a large-diameter round steel bar 48 (for example, a round steel bar having a diameter of 200 mm or more) is obtained.

  As shown in FIG. 3, a steel piece 50 from which a small-diameter round steel bar 48 (for example, a round steel bar having a diameter of less than 200 mm) is obtained is passed through the through hole 32. The through hole 32 is set to a size that allows the steel piece 50 having a small cross section to pass through without rolling. Thereby, the steel piece 50 with a small cross section is sent to a rolling process, without being edge-rolled. Small cross section

  In the method for manufacturing the round bar steel 48, the steel piece 46 that has been ridge-rolled is passed through the rolling hole 38 of the steel piece rolling machine 8. Thereby, generation | occurrence | production of the biting defect is suppressed. Occurrence of baldness is suppressed. The steel piece 44 does not need to be rolled into a substantially octagonal cross section in advance. In this partial rolling, it is not necessary to change the mold to a rolling roll that is rolled into an octagon. There is no time for changing molds to rolling rolls rolled into octagons. This manufacturing method is excellent in production efficiency.

  The steel piece 50 is a steel piece in which the length of one side of a square cross section is short. In the steel piece having a relatively small cross section, the biting failure in the rolling roll 14 does not occur. In the round steel bar 48 obtained from the steel piece 50, no lashes are generated. The size of the cross section where no biting failure or baldness occurs is specified by rolling a plurality of steel pieces having different cross-sectional areas on a trial basis. In this embodiment, there was no occurrence of a biting failure in a steel piece having a side length of less than 190 mm. In the round bar steel with a diameter of less than 170 mm obtained from a steel piece having a length of one side of less than 190 mm, there was no occurrence of baldness. In this embodiment, the steel piece 50 is a steel piece in which the length of one side of a square cross section is shorter than 190 mm. This steel piece 50 does not require ridge rolling. The steel piece 50 is passed through the through hole 32.

  A steel piece 44 having a side of a substantially square cross section with a side length of 190 mm or more is ridge-rolled before being rolled. One type of rolling roll 12 can be used for rolling a steel piece 44 having a side length of 190 mm or more and 280 mm or less. A good round steel bar 48 having a diameter of 170 mm or more and 260 mm or less can be obtained with this one type of rolling roll 12.

  The rolling roll 12 of the ridge rolling mill 6 can be rolled without replacement from a steel slab 50 having a small cross section that does not require ridge rolling to a steel slab 44 having a large cross section that requires ridge rolling. This rolling facility 2 does not require the ridge rolling mill 6 to be removed from the production line.

  The cross section of the steel slab 44 is rolled into a substantially square shape through the rolling hole 18 of the block mill 4. The size of the cross section of the steel piece 44 can be changed depending on the use of the steel piece 44. The length of one side of the square cross section is determined by the block rolling process. In the rolling equipment 2, the rolling of the steel slab 44 in which the length of one side of the square cross section is in the range of 130 mm to 260 mm is possible without replacing the rolling roll 12. The steel piece 44 is rolled to obtain a good round steel bar 48 having a diameter of 100 mm to 260 mm.

  In this embodiment, the generation of lashes is suppressed by rolling the slab of the steel piece 44. From this point of view, the rolling holes 26 formed by the pair of rolling rolls 12 may have any shape suitable for rolling the ridges. For example, the rolling hole 26 may be substantially oval.

  The present invention can be applied to a production method in which a steel bar having a rectangular cross section is rolled to obtain a round bar steel.

FIG. 1 is a conceptual diagram showing a round bar steel rolling facility according to an embodiment of the present invention. FIG. 2 is a front view showing a rolling roll of the block mill of FIG. FIG. 3A is a front view showing the rolling roll of the ridge rolling mill of FIG. 1, and FIG. 3B is a side view showing the rolling roll of the ridge rolling mill of FIG. FIG. 4 is a front view showing a rolling roll of the steel slab rolling mill of FIG. 1. FIG. 5 is a process diagram of a rolling method according to an embodiment of the present invention. FIG. 6 is a conceptual diagram showing a conventional round steel bar rolling facility. FIG. 7 is a process chart of steel slab rolling in which a round steel bar is obtained by rolling a conventional steel slab.

Explanation of symbols

DESCRIPTION OF SYMBOLS 2 ... Rolling equipment 4 ... Mass rolling mill 6 ... Edge rolling mill 8 ... Billet rolling mill 10 ... Roll roll 12 ... Roll roll 14 ... Roll roll 16. ··· Caliber 18 · · · Rolling hole 20 · · · Caliber 22 · · · Caliber 24 · · · Tapered surface 26 · · · Rolling hole 28 · · · Tapered surface 30 · · · cylindrical surface 32 · · · through hole 34 ... Caliber 36 ... Caliber 38 ... Rolling hole 40 ... Rolling hole 42 ... Steel ingot 44 ... Steel slab 46 ... Steel slab 47 ... Steel slab 48 ... Round Steel bar 50 ... Steel slab 100 ... Rolling equipment 102 ... Bump rolling mill 104 ... Steel slab rolling mill 106 ... Steel ingot 108 ... Rolling roll 110 ... Steel slab 112 ...・ Rolling roll 114 ... Round bar steel 116 ... Steel 118 ... Rolling roll

Claims (3)

In a rolling method to obtain a round bar steel by hot rolling a steel ingot,
A first rolling step in which the steel ingot is passed through a substantially rectangular rolling hole formed by a pair of rolling rolls, and a steel piece having a substantially rectangular cross section is obtained;
A second rolling step in which this steel slab is passed through a substantially rhomboid or substantially elliptical rolling hole formed by a pair of rolling rolls, and the ridge of the steel slab is rolled,
A third rolling step in which the steel slab is passed through a substantially elliptical rolling hole formed by a pair of rolling rolls to obtain a steel slab having a substantially elliptical cross section; A method for producing a round bar steel, comprising a fourth rolling step in which a steel slab having a substantially circular cross section is obtained by passing through a circular rolling hole.   Prior to the second rolling step, the round according to claim 1, further comprising a step in which a distance between a pair of rolling rolls forming a substantially diamond-shaped or substantially elliptical rolling hole is adjusted according to the cross-sectional size of the steel slab. Steel bar manufacturing method. A rolling mill comprising a pair of rolling rolls and rolling the steel ingot into a steel piece having a rectangular cross section by a pair of rolling rolls;
A ridge rolling mill that includes a pair of rolling rolls and rolls a ridge of a steel piece having a rectangular cross section with a pair of rolling rolls;
A steel slab rolling mill that includes a pair of rolling rolls and rolls a steel slab rolled at a ridge by a pair of rolling rolls into a predetermined cross section such as a round steel bar,
With
A rolling facility in which a pair of rolling rolls of a ridge rolling mill is formed with a substantially rhomboid or elliptical rolling hole and a through hole that is passed without rolling.

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