JPH1147804A - Method for rolling special shaped steel bar - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rolling method for obtaining a special shaped steel bar having extremely high dimensional accuracy by satisfying the degree of fullness in the nodal grooves of a roll and simultaneously preventing excessive over-filling in the outside diameter of ribs. SOLUTION: At the time of forming nodes 2 on the surface of a material S to be rolled having approximately round cross-sectional shape with the nodal grooves 7 which are formed at prescribed intervals in the circumferential direction of the grooves of the rolls R1 -R7 of a four-roll rolling mill arranged in at least the final finishing mill of a continuous rolling mill for wires and rods, tension of 0.2-1.2 kgf/mm<2> is imparted to the material S to be rolled between the four-roll rolling mill and the rolling mill just before it. By this impartation of tension, the dimension L3 of the outside diameter of a ribs 3 in four places of the circumference which are formed on the surface of the material S to be rolled by over filling in the clearances with an adjacent roll of the four-roll rolling mill is adjusted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling method for obtaining a deformed steel bar used for a reinforcing bar or the like embedded in concrete, and more particularly, to a method for improving the dimensional accuracy of a four-rib rib deformed steel bar exhibiting excellent bending workability. It relates to a rolling method that can be improved.

[0002]

2. Description of the Related Art As shown in FIG. 1 (a), a general deformed steel bar has a predetermined joint 2 and two vertical ribs 3 on a peripheral surface of a round bar.
Are formed. The diameter D of the portion (free surface) 5 excluding the node 2 and the rib 3, the height t of the node 2, the distance L between the nodes 2 adjacent in the axial direction, and the width d of the rib 3 are defined by JIS standards. In particular, the allowable range of the height t of the node 2 is strictly set. In contrast, FIG.
A four-ribbed deformed steel bar 1 having four longitudinal ribs 3 as shown in (b) is known. The four-rib deformed bar does not have torsion or bending in bending during use as compared with a general two-rib deformed bar, and has excellent workability.

As a method for rolling this type of 4-rib deformed steel bar, the present applicant has previously proposed a method in which the final finish rolling is performed by a four-roll rolling mill (Japanese Patent Laid-Open No. 7-32330).
2). This compound, two pair of rolls R _1, as shown in FIG. _2, R ₂ and R _3, in which is disposed a R ₄ to orthogonally, the finishing roll R ₁ to R to form a final finish path _In FIG. 4, a nodal groove 7 is formed at a predetermined interval along a circumferential direction as shown in FIG. This finishing roll R ₁ ~
Round caliber 8 by-out roll gap of R _4, the rolling mill train on the upstream side and pressure through the rolled material is rolled into a circular cross section, to form the section 2 on its peripheral surface. At the same time, four ribs 3 are formed by biting the adjacent rolls into the gap.

[0004]

When producing a deformed steel bar by rolling a material having a circular cross section from two orthogonal directions using _four finishing rolls R _{1 to} R ₄ having a nodal groove 7 in a circumferential groove 6. 2
Since the free surface 5 having no surface has a large amount of reduction, the material tends to extend in the longitudinal direction in proportion to the reduction in area. Therefore, the portion of the material that would otherwise be supplied to the roll node groove 7 to become the node 2 is removed by elongation. Therefore, now, as shown in FIG. 4, the outer diameter approximately equal to the diameter L _7a between opposing rolls R _1, R ₂ groove bottom (section head) of Fushimizo 7 (R _3, R ₄₎ 7a Rolled material S which is a round bar material
Is rolled down by the finishing rolls R _{1 to} R ₄ , the material filling degree of the roll joint grooves 7 becomes insufficient, and the meat is pulled down (pull-down).
And the node height t becomes smaller.

[0005] If the entry side diameter of the material S to be rolled is made larger than the above-mentioned L _7a in order to make the degree of filling of the groove 7 sufficient, the degree of filling of the roller groove 7 becomes sufficient, but the gap between adjacent rolls is increased. Of the rib 3 protrudes outward from the bottom of the node groove 7, and the outer diameter of the rib 3 becomes larger than the outer diameter of the node 2. Therefore, the range of variation in product dimensions was large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and is intended to satisfy the degree of filling of the roll joint groove and to prevent excessive biting of the rib outer diameter. Accordingly, an object of the present invention is to provide a rolling method capable of obtaining a deformed steel bar having extremely high dimensional accuracy.

[0007]

In order to achieve the above-mentioned object, a method for rolling deformed steel bars according to the present invention comprises a four-roll rolling mill at least as a final finishing mill among continuous rolling mills for wire rods and bars. The method of rolling a deformed steel bar in which a knot is formed on a surface of a material to be rolled having a substantially round cross-section with knot grooves formed at predetermined intervals in a circumferential direction of a roll hole die of the rolling mill. And the material to be rolled between the rolling mills
It is characterized by applying a tension of 1.2 kgf / mm ² .

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 shows an example of the path schedule adopted in this embodiment. First, a base material S having a square cross section is flat rolls F _{1 to} F ₆ of a rough rolling mill group.
By carrying out caliber-less rolling while alternately changing the rolling direction between the vertical direction and the horizontal direction, the cross-sectional area of the base material is gradually reduced. Subsequently, the intermediate mill group and finishing mill group oval grooved O ₁ ~ O ₄ and round caliber r ₁
And pressure from the vertical direction and the horizontal direction alternately with ~r _4, finally a final finishing mill of round grooved r ₅ of four rolling mill, quadrature by two pairs four rolls having a Fushimizo By rolling from two directions, a deformed steel bar 1 having the joints 2 and the four ribs 3 formed on the peripheral surface as shown in FIG.

At this time, tension is intentionally applied to the material to be rolled between the four-roll rolling mill (round hole type r ₅ ) provided as the final finishing mill and the immediately preceding rolling mill (round hole type r ₄ ). Even if the tension is applied by adjusting the number of rolls of both rolling mills by a single drive system in which each rolling mill is driven by a dedicated motor, the roll gap is adjusted by a common drive system in which a plurality of stands share a drive motor. Although it may be carried out only by itself, a single drive system is preferable from the viewpoint of assuring more precise dimensional accuracy. For example, by adjusting the rotation of the motor according to a load relay or a motor load current value during rolling, the tension applied to the material to be rolled between the final finishing rolling mill and the immediately preceding rolling mill is quickly and finely controlled while controlling the tension. It is possible to

[0010] The rolling roll R ₁ to R ₄ of the four-roll rolling mill for final finishing, like the roll R _1, R ₂ shown in FIG. 3, arcuate cross section circumferential groove 6 on the roll circumferential surface is formed A nodal groove 7 is formed on the groove surface of the circumferential groove 6 at a predetermined width at a predetermined interval in a direction perpendicular to the circumferential direction.

[0011] inlet side of the rolled material such two pairs four of the rolling four-roll rolling mill having grooved roll R ₁ to R roll gap-out 8 is formed by ₄ (i.e. round caliber r ₅₎ S is reduced by rolling rolls R _{1 to} R ₄ while applying tension. In this case, the rolled material S fed from the round hole type r ₄ immediately before the rolling mill is a cross-sectional substantially round shape as shown in FIG. The outer diameter H of the material to be rolled is equal to or larger than the diameter (hereinafter referred to as “knot head diameter”) L _{7a of} a circular section formed by the groove bottom 7a of the knot groove 7 of the rolling rolls R _{1 to} R ₄ of the four-roll mill. And

As described above, when the outer diameter H of the material S to be passed through the round hole type r ₅ is larger than the node diameter L _7a of the roll hole type, the rolling material S is tensioned. with reduction in R ₁ to R _4, the rolled material S is subjected to any elongation due to tensile stress elongation in the longitudinal direction by the pressure, the outer diameter is rolled while increasing reduced diameter than the absence of tensioning. However, since the extra material is supplied into the roll groove type groove 7 due to the large outer diameter, the round hole shape r ₅
The filling degree of the nodal groove 7 is good, and a large pull-down does not occur. Therefore, the nodal height t of the product deformed steel bar 1 does not decrease, and the roundness is good.

On the other hand, each adjacent rolling row which is a non-rolling portion
Le R₁~ R_FourRolled material S starts to bite in the gap between
As a result, ribs 3 of deformed steel bars are formed (FIG. 6). This bite
Bare 10 is the rib outer diameter L of the product deformed steel bar._ThreeStipulate
Since the rolling force is not applied, the outside of the material to be rolled S
The amount corresponds to the diameter H. Therefore, without applying tension
When rolled as it is, the deformed steel bar of the product is as shown in FIG.
To rib outer diameter L_ThreeIs the joint outer diameter L_TwoIt will be larger.
However, according to the method of the present invention, rolling while applying tension is performed.
And the round hole type r_FiveEntry rolled material supplied to
Reduction rate of outer diameter H of S (% of reduction amount to original outer diameter H)
Is larger, so that the rib 3 starts to bite 10
As a result, as shown in FIG.
Outer diameter L _ThreeIs the joint outer diameter L_TwoBecomes equal to

FIG. 9 shows the experimental results of the relationship between the tension between stands and the outer diameter reduction rate (HL- ₃ ) / H of the material S to be rolled in the present invention. The test conditions were as follows.

Rolled material S Outer diameter H: 14.0 mm Target dimensions Diameter D: 11.5 mm Node height t: 0.75 mm Distance between nodes L: 9.5 mm Rib width d: 1.5 mm Rolling method One-pass rolling by a four-roll rolling mill, tension is applied to the material to be rolled between immediately before rolling mill Roll shape Node head diameter L _7a : 13.0 mm Node groove depth: 0.75 mm From these results, the tension between stands It can be understood that the diameter reduction rate increases and becomes gradually saturated almost in proportion to. The magnitude of the tension applied in the method of rolling a deformed steel bar according to the present invention is 0.1 mm.
² to 1.2 kg / mm ² . If the tension is less than 0.2 kg / mm ^2, the reduction rate of the material (assuming that the diameter H is larger than the groove diameter of the hole type) is less than 2%, and the biting is excessive. Outer diameter. On the other hand, the upper limit 1.
2 kg / mm ² is a tension at which the material to be rolled S is torn. [Example] As target dimensions, diameter D: 11.5 mm, distance L between nodes: 9.5 mm, height t of node: 0.75 m
m, rib width d: 1.5 mm, rib height: 0.75
In order to manufacture a deformed steel bar of 1 mm, the outer diameter H is 14.0 m.
m was finish-rolled with a 4-roll rolling mill.

At this time, the four-roll rolling mill and the immediately preceding rolling mill
0.5kgf / mm ^TwoImplemented when
As an example, a case without tension was added as a comparative example. Izu
Also in this case, the roll shape of the four-roll rolling mill has a nodal head diameter L
_7a: 13.0 mm, depth of the nodal groove 0.75 mm.

As a result, in the comparative example, the knot height t is 0.6.
Although it was almost the target value of 5 to 0.75 mm, the height of the rib was 0.9 to 1.2 mm, deviating in a direction larger than the target value. On the other hand, in the example, the knot height t and the rib height were 0.65 to 0.75 mm, which almost matched the target values.

[0018]

As described above, according to the method of rolling a deformed steel bar according to the present invention, at least when rolling a 4-rib deformed steel bar using a four-roll rolling mill as a final finishing rolling mill, The material is sufficiently filled into the nodal groove, and the rolling is performed while applying tension to the material to be rolled between the immediately preceding rolling mill, so that pull-down of the nodal portion and excessive biting of the rib portion are prevented. This has the effect of improving the dimensional accuracy of the deformed steel bar.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a deformed steel bar, in which (a) is a two-rib deformed steel bar, and (b) is a four-rib deformed steel bar.

FIG. 2 is a front view illustrating a roll arrangement of a four-roll rolling mill.

FIG. 3 is a schematic diagram showing an example of a roll groove of a final finishing mill for deformed bar rolling.

FIG. 4 is a cross-sectional view for explaining a thinning (pull-down) in a roll hole type at the time of rolling.

FIG. 5 is a schematic diagram showing an example of a path schedule according to the present invention.

FIG. 6 is a sectional view showing a dimensional relationship between a roll die and a material to be rolled in the final finishing mill of the present invention.

FIG. 7 is a diagram showing an example of a cross-sectional shape of a deformed steel bar when rolled without applying tension.

FIG. 8 is a diagram showing an example of a cross-sectional shape of a deformed steel bar when rolled while applying tension.

FIG. 9 is a graph showing the relationship between the tension between stands and the diameter reduction rate of a material.

[Explanation of symbols]

2 Section 3 ribs 7 Fushimizo R ₁ roll R ₂ roll R ₃ roll R ₄ roll S material being rolled L ₃ ribs outer diameter

Claims (1)

[Claims] 1. A four-roll rolling mill is arranged at least in a final finishing rolling mill of a continuous rolling mill for wire rods and bars, and a nodal groove formed at a predetermined interval in a circumferential direction of a roll die of the rolling mill. In a method of rolling a deformed steel bar in which a node is formed on the surface of a material to be rolled having a round cross section, a tension of 0.2 to 1.2 kgf / mm ² is applied to the material to be rolled between the four-roll rolling mill and the immediately preceding rolling mill. And a method for rolling deformed steel bars.