JP5971224B2 - Round billet rolling method - Google Patents

Description

  The present invention relates to a method for rolling a round billet.

When manufacturing a wire rod, steel bar, or small diameter round billet by subjecting a round billet to hot rolling, a continuous rolling facility in which a plurality of rolling parts having a pair of rolls arranged opposite to each other is used, The diameter of the round billet is reduced by sequentially passing the round billet through the plurality of rolling portions.
In recent years, there has been a demand for product cost reductions and stricter product dimensions, so the upstream rolling section of continuous rolling equipment performs large-pressure rolling with flat rolls mainly for securing a reduction in area, and downstream In the rolling section on the side, rolling is performed by making a product with a perforated roll. And the rolling which satisfies both the said requirements is implement | achieved by the combination of these two types of rolling.

  A problem in the continuous rolling as described above is a biting failure in the first rolling section on the upstream side of the continuous rolling equipment (that is, the rolling section through which the round billet is first passed). In the second and subsequent rolling sections, the round billet is pushed into the rolling section with a large pushing force from the upstream rolling section, so that it is difficult to cause a biting failure in which the round billet is not caught between the rolls in the rolling section. On the other hand, in the 1st rolling part, since there is no upstream rolling part, the pushing force is small. Therefore, the round billet is difficult to be caught between the rolls of the rolling part, and there is a possibility that a poor biting may occur. In particular, when a new roll was used for the first rolling part or when a roll immediately after polishing was used, the round billet was less likely to be bitten because the friction coefficient of the outer peripheral surface of the roll was small.

  In general, in hot rolling, when the biting angle is θ and the coefficient of friction between the rolled material and the roll is μ, the biting condition of the rolled material needs to satisfy the expression μ> tan θ. Therefore, in the large rolling rolling that deviates from the biting condition, the biting failure is likely to occur. Therefore, the biting failure was suppressed by applying a technical device. In the single rolling with a small indentation force, the guideline of the upper limit of the biting angle is 20 °. Therefore, in the present invention, rolling with the biting angle exceeding 20 ° is referred to as large reduction rolling.

An example of the rolling method with the above technical device is the technology described in Patent Document 1. That is, in order to improve the biting property of the rough bar rolled by the roughing mill to the finishing mill, a rotary cutting device is arranged on the downstream side of the roughing mill, and the tip of the rough bar is cut into a wedge shape. It is a technology. The tip formed in the wedge shape has a curved surface with a radius of curvature similar to that of the roll of a finish rolling mill, so the contact form between the roll and the coarse bar when the coarse bar is pushed between the rolls is in surface contact. It becomes. As a result, the coarse bar is easily caught between the rolls of the finishing mill.
Further, in Patent Document 2, the friction coefficient between the rolled material and the roll is increased by injecting a mixture of fluid and solid particles to the roll from a nozzle arranged in the vicinity of the roll, and the biting of the rolled material is performed. Techniques for improving the performance have been proposed.

JP 2003-285101 A JP-A-4-238612

However, in the technique disclosed in Patent Document 1, it is necessary to introduce a rotary cutting device to a continuous rolling facility, and thus there is a problem that a cost and an installation place are required. In addition, since the tip of the coarse bar is cut, there is a problem that the yield decreases.
Furthermore, in the technique disclosed in Patent Document 2, since it is necessary to introduce an injection device that injects a mixture of a fluid and solid particles onto a roll into a continuous rolling facility, there is a problem that a cost and an installation place are required. Moreover, there is a possibility that the rolling stop time may increase due to an increase in the number of man-hours, and further, there is a problem that the necessity to maintain the spraying device arises.

  Therefore, the present invention solves the problems of the conventional technology as described above, and without introducing new equipment, and without causing a decrease in yield and an increase in man-hours, the first upstream side of the continuous rolling equipment. It is an object of the present invention to provide a round billet rolling method capable of improving the biting property of the round billet in the second rolling section.

In order to solve the above problems, a round billet rolling method according to an aspect of the present invention is to roll a round billet using a continuous rolling facility in which a plurality of rolling sections having a pair of opposed rolls are arranged. It is a rolling method of a round billet to reduce the diameter, and a hole-type roll is used as the roll of the first rolling section on the upstream side through which the round billet is first passed among the plurality of rolling sections of the continuous rolling equipment. The cross-sectional shape of the circumferentially extending groove formed on the outer peripheral surface of the perforated roll is an arc along the outer peripheral surface of the round billet.
In this round billet rolling method, the radius of curvature of the arc may be 0.95 times to 1.05 times the radius of the round billet. The depth of the groove may be 1% or more and 15% or less of the diameter of the round billet. Furthermore, the groove may be provided in the center in the width direction of the outer peripheral surface of the hole-shaped roll, and both end portions in the width direction of the outer peripheral surface of the hole-shaped roll may be cylindrical surfaces.

  The rolling method of the round billet according to the present invention uses a perforated roll in which the cross-sectional shape of the groove is an arc along the outer peripheral surface of the round billet. The round billet can be improved in the first rolling section on the upstream side of the continuous rolling facility.

It is a schematic diagram which shows an example of the continuous rolling equipment which can apply the rolling method of the round billet which concerns on this invention. It is a figure explaining the shape of a roll.

An embodiment of a rolling method for a round billet according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing an example of continuous rolling equipment to which the rolling method of a round billet according to the present invention can be applied. Moreover, FIG. 2 is a figure explaining the shape of the roll which the upstream 1st rolling part through which a round billet passes first among several rolling parts with which the continuous rolling equipment of FIG.
The continuous rolling facility shown in FIG. 1 is a facility that performs hot rolling on a round billet CB having a circular cross section to reduce the diameter, for example, to produce a wire rod, steel bar, or a small diameter round billet. The continuous rolling equipment includes a roughing mill 1 disposed on the upstream side, an intermediate rolling mill 2 disposed on the downstream side of the roughing mill 1, and a finish disposed on the further downstream side of the intermediate rolling mill 2. And a rolling mill 3. Furthermore, although illustration is abbreviate | omitted, the rolling mill for wire manufacture is provided in the downstream of the finish rolling mill 3. FIG.

Each of the rough rolling mill 1, the intermediate rolling mill 2, and the finishing rolling mill 3 has a pair of rolls arranged opposite to each other, and includes a rolling stand as a rolling unit that rolls the rolled round billet CB by rolling. Yes. The number of rolling stands provided in the rough rolling mill 1, the intermediate rolling mill 2, and the finishing rolling mill 3 is not particularly limited, and may be one or more.
When the round billet CB is rolled to reduce the diameter to produce the steel bar SR, for example, the rough rolling mill 1 includes eight rolling stands, the intermediate rolling mill 2 includes ten rolling stands, and the finishing rolling mill 3 includes two rolling mills. It is good also as a structure provided with two rolling stands (refer FIG. 1).
When a round billet CB is rolled to reduce the diameter and produce a small round billet, for example, the rough rolling mill 1 includes four rolling stands, the intermediate rolling mill 2 includes three rolling stands, and finish rolling. The machine 3 may be configured to include one rolling stand.

Below, the example which manufactures a bar steel using the continuous rolling installation of FIG. 1 is demonstrated.
The rough rolling mill 1 includes four rolling stands having horizontal rolls and four rolling stands having vertical rolls, and the rolling stands having horizontal rolls and the rolling stands having vertical rolls are directed from the upstream side to the downstream side. Are alternately arranged.
More specifically, the first rolling stand S1, which is the first upstream rolling stand, has a pair of rolls 11A and 11B extending in the horizontal direction so as to oppose the supplied round billet CB in the vertical direction. The second rolling stand S2, which is the second upstream rolling stand, is a first rolling stand in which a pair of rolls 12A and 12B extending perpendicularly to the rolls 11A and 11B are arranged to face each other. The round billet CB rolled in S1 is rolled down in the horizontal direction.

  The third rolling stand S3, which is the third upstream rolling stand, has the same configuration as the first rolling stand S1, and the fourth rolling stand S4, which is the fourth upstream rolling stand, 2 It has the same configuration as the rolling stand S2. Subsequent fifth to eighth stands (not shown) are similar to the first to fourth rolling stands S1 to S4, the rolling stand having the same configuration as the first rolling stand S1, and the second rolling. Rolling stands having the same configuration as the stand S2 are alternately arranged.

  Therefore, the billet CB supplied to the roughing mill 1 is alternately rolled in the rolling directions orthogonal to each other in the first to eighth rolling stands, that is, the rolling directions different by 90 °, and the diameter is gradually reduced. The rolls of the second to sixth rolling stands are flat rolls in which the outer peripheral surface of the roll is a cylindrical surface in order to perform large reduction rolling and ensure a reduction in area. The rolls of the seventh and eighth rolling stands have a flat roll portion in which the outer peripheral surface of the roll is a cylindrical surface, and a hole-type roll portion in which a hole-shaped groove is formed on the outer peripheral surface of the roll. Both rolling and rolling with a perforated roll can be performed. The shape of the rolls 11A and 11B of the first rolling stand S1 will be described in detail later.

Next, the round billet CB rolled by the rough rolling mill 1 and reduced in diameter is supplied to the intermediate rolling mill 2.
The intermediate rolling mill 2 includes five rolling stands having horizontal rolls and five rolling stands having horizontal rolls, and the rolling stands having horizontal rolls and the rolling stands having vertical rolls are directed from the upstream side to the downstream side. Are alternately arranged.
More specifically, the ninth rolling stand S9, which is the ninth rolling stand on the upstream side, has a pair of rolls 21A and 21B extending in the horizontal direction facing each other, and the supplied round billet CB having a reduced diameter is vertically aligned. The tenth rolling stand S10, which is the tenth rolling stand on the upstream side, has a pair of rolls 22A and 22B extending perpendicularly and perpendicular to the rolls 21A and 21B. The round billet CB rolled in the ninth rolling stand S9 is pressed down in the horizontal direction.

  The eleventh rolling stand S11, which is the eleventh rolling stand on the upstream side, has the same configuration as the ninth rolling stand S9, and the twelfth rolling stand S12, which is the twelfth rolling stand on the upstream side, It has the same configuration as the 10 rolling stand S10. Subsequent thirteenth to eighteenth stands (not shown) are, similarly to the ninth to twelfth rolling stands S9 to S12, a rolling stand having the same configuration as the ninth rolling stand S9, and the tenth rolling. Rolling stands having the same configuration as the stand S10 are alternately arranged.

  Accordingly, the billet CB having a reduced diameter supplied to the intermediate rolling mill 2 is alternately rolled in the rolling directions orthogonal to each other in the ninth to eighteenth rolling stands, that is, the rolling directions different by 90 °, and gradually built into the product. Is made. The rolls included in the ninth to eighteenth rolling stands are perforated rolls in which a circular arc-shaped groove is formed on the cylindrical outer peripheral surface of the roll in order to perform rolling into the product.

Next, the round billet CB which has been rolled by the intermediate rolling mill 2 and made into a product is supplied to the finishing mill 3.
The finishing mill 3 includes one rolling stand having a horizontal roll and one rolling stand having a roll. Specifically, the 19th rolling stand S19 which is the 19th rolling stand on the upstream side has a pair of rolls 31A and 31B extending in the horizontal direction so as to face each other, and the round billet CB in which the supplied product is built is made. A twentieth rolling stand S20 that is a 20th rolling stand that is squeezed in the vertical direction and is the upstream side 20th (most downstream side) rolling stand is perpendicular to the rolls 31A and 31B and extends in the vertical direction. The round billet CB rolled by the 19th rolling stand S19 is pressed down in the horizontal direction by arranging 32B facing each other.

  Therefore, the round billet CB with the built-in product supplied to the finish rolling mill 3 is alternately rolled in the rolling directions orthogonal to each other in the nineteenth and twentieth rolling stands S19 and S20, that is, in the rolling directions different by 90 °. Then, finish rolling is gradually performed to obtain a product steel bar SR. The rolls 31A, 31B, 32A, 32B of the 19th and 20th rolling stands S19, S20 are holes in which a circular arc-shaped groove is formed on the cylindrical outer peripheral surface in the same manner as the rolls 31A, 31B, 32A, 32B. It is a mold roll.

  In addition, as the 19th and 20th rolling stands S19 and S20, the round billet CB in which the product is built is formed from the top, bottom, left, and right by a total of 4 rolls, that is, a pair of horizontally arranged rolls and a pair of vertically arranged rolls. You may use the rolling stand which performs 4 roll rolling which pinches and rolls. The four rolls in this case are hole-type rolls in which a groove having a circular arc shape is formed in the center in the width direction of the cylindrical outer peripheral surface of the roll.

  Here, the shape of the rolls 11A and 11B of the first rolling stand S1 will be described in detail with reference to FIG. As described above, the first rolling stand on the upstream side of the continuous rolling equipment (that is, the rolling stand through which the round billet is first passed) has a problem of poor biting. As a result of intensive studies, the inventors have solved the problem of biting failure by applying technical contrivance in the shape of the rolls 11A and 11B of the first rolling stand S1, and As a result, the area reduction rate can be ensured equally, and the present invention has been completed.

  That is, roll 11A, 11B which 1st rolling stand S1 has is made into a hole-type roll, The cross-sectional shape of the groove | channel 51 extended in the circumferential direction formed in the outer peripheral surface (The groove | channel 51 is formed in the plane in alignment with the rotating shaft of roll 11A, 11B. The sectional shape when cut) was an arc along the outer peripheral surface of the round billet CB. If the rolls 11A and 11B are perforated rolls having an outer peripheral surface having such a shape, the rolls 11A and 11B and the round billet CB are brought into surface contact at the time of biting, the contact area is increased, and the friction coefficient is increased. Therefore, the round billet CB is easily bitten between the rolls 11A and 11B.

  When using a new roll or a roll just after polishing, the friction coefficient of the outer peripheral surface of the roll is small, so that it is easy to cause biting failure, and in particular, it is easy to cause biting failure at the first passing of the material. If it is a hole-type roll which has the outer peripheral surface of such a shape, even if it is a case where a new roll or a roll just after grinding | polishing is used, it will be hard to produce a biting defect. As a result, downtime (operation stop time of the continuous rolling equipment) when biting failure occurs is reduced.

And, it is only necessary to change the shape of the roll, and it is not necessary to introduce a new device to the continuous rolling equipment, so it is not necessary to prepare a place for installing the device, and to improve the biting property at a low cost Can do. Furthermore, since it is not necessary to cut the rolled material as in the technique of Patent Document 1 described above, the yield is not reduced and the man-hour is not increased.
The radius of curvature of the arc is preferably 0.95 times or more and 1.05 times or less of the radius of the round billet CB to be rolled. If it does so, it will become difficult to generate | occur | produce a biting defect more. If the radius of curvature of the arc is less than 0.95 times the radius of the round billet CB, the rolls 11A, 11B and the round billet CB are less likely to come into surface contact, which may reduce the ease of biting. On the other hand, if it exceeds 1.05 times, the contact area between the rolls 11A and 11B and the round billet CB becomes small (the outer peripheral surfaces of the rolls 11A and 11B have a shape close to a flat roll). May decrease.

  Moreover, it is preferable that the depth d (depth of the deepest part) of the groove | channel 51 shall be 1% or more and 15% or less of the diameter of the round billet CB to roll. By doing so, since the depth d of the groove 51 is shallow, it is possible to achieve both large rolling reduction that achieves a high surface reduction rate comparable to rolling by a flat roll and excellent biting properties. If the depth d of the groove 51 is less than 1% of the diameter of the round billet CB, the depth d of the groove 51 is too shallow, and the biting property may be reduced. On the other hand, if it exceeds 15%, the depth d of the groove 51 is too deep, so that the amount of reduction becomes small and there is a possibility that a high area reduction rate cannot be realized.

  Furthermore, it is preferable that the groove 51 is provided in the center in the width direction of the outer peripheral surfaces of the rolls 11A and 11B, and both end portions in the width direction of the outer peripheral surfaces of the rolls 11A and 11B are the cylindrical surfaces 52 and 52. When grooves are formed over the entire width direction of the outer peripheral surfaces of the rolls 11A and 11B and both end portions in the width direction are not cylindrical surfaces, the reduction amount is small, and there is a possibility that a high surface reduction rate cannot be realized. On the other hand, if the range of the cylindrical surfaces at both ends in the width direction is too large (if the width of the groove 51 is too small), the shape of the groove 51 becomes distorted, which may damage the round billet CB.

〔Example〕
The present invention will be described more specifically with reference to the following examples. A round billet was supplied to a rolling stand similar to the first rolling stand S1 included in the continuous rolling facility of FIG. 1 to evaluate the degree of occurrence of biting failure. The round billet was supplied to the rolling stand 30 times, and the occurrence degree of the biting failure was evaluated according to how many times the biting failure occurred.
The diameter of the round billet to be rolled is 175 mm. Moreover, the roll which a rolling stand has is a new hole type roll, the groove | channel extended in the circumferential direction is provided in the width direction center part of the outer peripheral surface, and the width direction both ends of the outer peripheral surface are cylindrical surfaces. . And the cross-sectional shape of a groove | channel is an arc along the outer peripheral surface of the round billet to roll, and it evaluated by changing the curvature radius of this arc variously. In addition, the depth of the groove was set to 5 mm in order to secure the same area reduction rate as rolling with a flat roll. The rolling conditions were such that the gap between the two rolls of the rolling stand was 104 mm, the temperature of the round billet was 940-1100 ° C., and the biting angle was 30.6 °.

The radius of curvature of the arc is 0.95 times (83.1 mm), 1 time (87.5 mm), 1.05 times (91.9 mm), or 1.08 times (94.5 mm) of the radius of the round billet. did. In addition, as a comparative example, evaluation was performed when the roll of the rolling stand was a flat roll.
When the radius of curvature of the arc is 0.95 times, 1 time, and 1.05 times the radius of the round billet, no biting failure occurs even once in 30 times, and the radius of curvature of the arc is equal to the radius of the round billet. In the case of 1.08 times, biting failure occurred in 5 out of 30 times. Moreover, in the rolling of these Examples, the large reduction rolling equivalent to the case of using a flat roll could be realized. On the other hand, in the comparative example using a flat roll, biting failure occurred in 10 out of 30 times.

11A, 11B Roll 51 Groove 52 Cylindrical surface d Depth CB Round billet SR Steel bar S1 First rolling stand

Claims (3)

A rolling method of a round billet that rolls a round billet and reduces the diameter using a continuous rolling facility in which a plurality of rolling parts having a pair of opposed rolls are arranged,
Of the plurality of rolling parts of the continuous rolling equipment, a hole roll is used as the roll of the first rolling part on the upstream side through which the round billet is first passed, and is formed on the outer peripheral surface of the hole roll. The cross-sectional shape of the circumferentially extending groove is an arc along the outer peripheral surface of the round billet, and the radius of curvature of the arc is 0.95 to 1.05 times the radius of the round billet. A rolling method for round billets. Rolling method of the round billet according to claim 1, characterized in that the depth of the groove is 15% or less than 1% of the diameter of the round billet. Provided the groove in the widthwise central portion of the outer peripheral surface of the grooved roll, according to both widthwise end portions of the outer peripheral surface of the grooved roll to claim 1 or claim 2, characterized in that the cylindrical surface Round billet rolling method.

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