JP2002102912A - Apparatus and method for fixed diameter rolling of metallic pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus and method for a fixed diameter rolling of a metallic pipe capable of preventing the generation of flashes and obtaining an excellent circularity when a plurality of metallic pipes with the same specifications are produced from a plurality of tube stock with the same specifications. SOLUTION: A drafting position of the aperture die rolling at least a single stand of a plurality of basing stands set up to an either tube stock after the No.2 tube stock among a plurality of tube stock is adjusted based on the variations between a recorded value of the rolling information given by at least a single stand of a plurality of basing stands of the tube stock rolled by the fixed diameter rolling earlier than either tube stock after No.2 and a target value of the rolling information.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sizing apparatus and a sizing method for a metal pipe such as a seamless steel pipe. More specifically, the present invention relates to a constant diameter rolling apparatus and a constant diameter rolling method for a metal tube capable of manufacturing a metal tube excellent in both roundness and surface properties.

[0002]

2. Description of the Related Art For example, a metal pipe such as a seamless steel pipe is generally formed by heating a steel slab and piercing it with a piercing mill or the like to form a thick hollow material. Etc., and then reduced diameter rolling is performed by a constant diameter rolling machine so as to have a predetermined outer dimension and a perfect cross section. This constant diameter rolling mill usually has a 3 roll sizer or a 2 roll sizer having 4 to 13 stands,
A stretch reducer or the like having 25 stands is used. In the following description, a three-roll sizer in which each stand has three rolls will be described as an example of a constant diameter rolling mill.

FIG. 1 is an explanatory diagram schematically showing a configuration of a three-roll sizer. FIG. 2 is a side view schematically showing three rolls arranged on each stand of the three-roll sizer. FIG. 2 (a) is a side view taken along the line AA of FIG. 1, and FIG. It is a BB arrow side view. 1 and 2, reference numeral 1 is a stand, 2 is a hole type roll, 3 is a metal tube, and O is a pass center.

A three-roll sizer is a stand 1 in which three hole-type rolls 2, 2, 2 as shown in FIGS. 2 (a) and 2 (b) are incorporated at 120 ° intervals around a path center O in a vertical plane. Are connected and arranged as shown in FIG. In the adjacent stands, the roll axes are arranged so as to be shifted from each other by 60 ° about the pass center so that the mutual roll arrangement is in the relationship shown in FIG. 2A and FIG. 2B. Usually, an arcuate hole-shaped roll is used in the last one to several stands of the sizer, and an elliptical arc-shaped hole-shaped roll is used in other stands.

[0005] In the rolling of a sizer, there is no restriction on the inner surface of the tube. Therefore, in the rolling of one stand, the bottom of the groove (E in Fig. 2 (a)) and the flange (F in Fig. 2 (a)) are rolled. In this case, the amount of wall thickness increase accompanying rolling is different, and uneven deformation occurs in the circumferential direction. Since rolling is performed while the groove bottom and the flange of the material to be rolled are alternately changed by 60 °, the thickness of the intermediate point between the groove bottom and the flange becomes thicker or thinner than the groove bottom or the flange. This is referred to as hexagonal tension or square tension, and is likely to occur particularly when rolling a thick-walled thick pipe.

In order to prevent the hexagonal tension, it is necessary to reduce the circumferential wall thickness by making the shape of the hole-shaped roll close to a perfect circle and rolling the material to be rolled so as to hold down the material to be rolled by the flange portion of the hole-shaped roll. is there. However, if the shape of the grooved roll is made closer to a perfect circle, biting may occur at the flange portion and biting flaws may remain in the rolled product. In particular,
This is likely to occur when rolling thin-walled thin tubes.

Therefore, when a wide range of wall thickness is rolled with the same roll-type roll, hexagonal tension is likely to occur in a thick-walled tube, and biting is likely to occur in a thin-walled tube. For that reason,
It is necessary to hold a roll in accordance with the wall thickness of the pipe, and the number of rolls increases, which causes problems such as an increase in equipment costs and a shortage of roll storage space. Further, frequent roll replacement is required according to the wall thickness of the pipe, and a great deal of time and labor must be spent, which is also a problem in terms of productivity.

In order to solve this problem, there has been disclosed a rolling method using a constant diameter rolling mill capable of adjusting a rolling position of a grooved roll. For example, in Japanese Patent Application Laid-Open No. Hei 7-16616, using a housing that changes the distance between the roll rotation axis and the pass center, a predetermined caliber is cut in a state where the distance between the roll rotation axis and the pass center is large, A method of rolling by changing the ellipticity of a grooved roll by reducing the distance between a roll rotation axis and a pass center during rolling is disclosed.

In such a constant-diameter rolling mill, it is possible to roll pipes having different thicknesses by using the same hole roll by adjusting the rolling position of the hole roll. That is, in the rolling of thick material, the roll reduction position is opened to make the hole shape close to a perfect circle, and the occurrence of hexagonal tension is suppressed.In the case of thin material rolling, the roll reduction position is closed to reduce the degree of inertia of the hole shape. By increasing the size, the load acting on the flange is reduced, and the occurrence of a biting flaw is suppressed.

[0010]

However, even when the sizing is performed by the sizing mill disclosed in the above publication,
The distribution of the working degree of each stand is broken due to the wear of the grooved roll, the setting error of the roll pressing position, etc., the roundness of the product obtained by constant diameter rolling is deteriorated, and the product is scratched out Sometimes. In other words, the distribution of the working degree of each stand is broken, and in rolling at the stand where the working degree is higher than the target working degree, the load applied to the flange increases, and a biting flaw occurs. In particular, when the working degree of the final stand is lower than the target working degree, the portion where the outer surface of the material to be rolled does not come into contact with the grooved roll (the unfilled part, this phenomenon is called the unfilled phenomenon) increases. The roundness is reduced.

SUMMARY OF THE INVENTION In view of the above situation, it is an object of the present invention to prevent the occurrence of biting flaws when manufacturing a plurality of metal pipes of the same specification from a plurality of raw pipes of the same specification, and to provide an excellent tube. It is an object of the present invention to provide a sizing apparatus and a sizing method for a metal tube capable of obtaining a roundness.

[0012]

Means for Solving the Problems The present inventor made various studies to solve the above-mentioned problems, and obtained the following findings. (A)
Detects rolling information such as rolling load and rolling torque of each stand constituting the constant diameter rolling mill, calculates the deviation between the actual value of the detected rolling information and the predicted value of the rolling information, and, based on the deviation, determines the next material. By adjusting the roll reduction position of each stand which is set at the time of constant diameter rolling of the base tube, it is possible to prevent the occurrence of scratches.

(B) The above-mentioned rolling information is detected at the last stand, and a deviation between the actual value of the detected rolling information and the predicted value of the rolling information is obtained. By adjusting the roll reduction position of the final stand and / or the roll reduction position of the upstream stand adjacent to the final stand, it is possible to prevent biting flaws and improve roundness.

The present invention has been completed based on the above findings, and the gist thereof is as follows. (1) A constant diameter rolling mill including a plurality of stands having a plurality of grooved rolls, and rolling information of at least one of the plurality of stands when the constant diameter rolling mill performs constant diameter rolling of a metal tube. Rolling information detector to be detected, based on the deviation between the actual value of the rolling information and the predicted value of the rolling information detected by the rolling information detector, based on the roll-shaped roll in at least one of a plurality of stands A rolling device for a metal tube, comprising: a control mechanism for adjusting a rolling position.

(2) The metal tube rolling apparatus according to the above (1), wherein the plurality of grooved rolls are three grooved rolls. (3) A constant diameter rolling method using a constant diameter rolling mill provided with a plurality of stands having a plurality of grooved rolls, wherein a plurality of pipes of the same specification are used by the constant diameter rolling mill to form a plurality of pipes of the same specification. When manufacturing a metal tube, a second one of the plurality of raw tubes is used.
The roll-down position of the hole-shaped roll of at least one of the plurality of stands set for any of the second and subsequent blanks is set to a fixed diameter before any of the second and subsequent blanks. A method for rolling a metal tube, wherein the method is adjusted based on a deviation between an actual value of rolling information of at least one of the plurality of stands of the rolled raw tube and a predicted value of the rolling information.

(4) The apparatus for rolling a metal tube according to the above item (3), wherein the plurality of grooved rolls are three grooved rolls. (5) The method for rolling a metal tube according to the above (3) or (4), wherein the rolling information is a rolling load.

(6) The method for rolling a metal tube according to the above (3) or (4), wherein the rolling information is a rolling torque. (7) The stand according to any one of the above items (3) to (6), wherein the stand for adjusting the rolling position of the roll is a stand having the deviation or an upstream stand adjacent to the stand having the deviation. The method for rolling a metal tube according to any one of the above.

[0018]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description of the embodiments, a case where the constant diameter rolling mill is a three-roll sizer is taken as an example.

FIG. 3 is a schematic diagram schematically showing an example of the configuration of the rolling device for metal pipes according to the present embodiment. In this figure, reference numeral 4 denotes a 3-roll sizer, S1 to S7 stand, 5: a rolling information detector, 6: an arithmetic unit, 7: a roll reduction position control device, and the same elements as those in FIG.

As shown in FIG. 3, the metal tube rolling apparatus according to the present embodiment has three grooved rolls (two grooved rolls are shown in FIG. 3 and one is omitted). 7 with 2,
A three-roll sizer 4 including the original stands S1 (first stand) to S7 (seventh stand), and rolling information detectors 5, 5, 5, and 5 provided on each stand. And a control mechanism composed of a roll pressing position control device (hereinafter, also referred to as a control device) 7, 7, 7, 7 provided in each stand. In the figure, of the seven stands, two stands S1 and S2 on the upstream side and two stands S6 and S7 on the downstream side are shown, and the stands S3 to S5 are omitted.

As the three-roll sizer according to the present embodiment, a known three-roll sizer can be used. That is, 3
As shown in FIGS. 2 (a) and 2 (b), the roll sizer is composed of a stand in which three hole type rolls 2, 2, 2 are assembled around a path center O in a vertical plane at intervals of 120 °. Be composed. In the adjacent stands, the roll axes are arranged so as to be shifted from each other by 60 ° about the pass center so that the mutual roll arrangement is in the relationship shown in FIG. 2A and FIG. 2B.

The rolling information detector 5 detects rolling information such as a rolling load and a rolling torque acting on each stand when rolling the material to be rolled. A load cell is used for detecting the rolling load, and a rolling cell is used for detecting the rolling load. An ammeter is used for detecting the torque.

The arithmetic unit 6 calculates the deviation between the actual value of the rolling information such as the rolling load and the rolling torque of each stand detected by the rolling information detector 5 and the predicted value of the rolling information. A function of calculating a correction amount of the roll-down position of the hole-shaped roll of each stand so as to be zero, and at least one of a stand where a correction amount larger than a predetermined value is recognized and an upstream stand adjacent to the stand And a function of transmitting a correction amount of an electric signal to the control device.

The control device 7 has, for example, a hydraulic drive mechanism capable of adjusting the rolling position of the roll.
Based on the transmitted electric signal of the correction amount, the drive mechanism is operated to correct the roll-down position of the roller.

In the description of the metal tube rolling apparatus of the present embodiment, a case where a rolling information measuring device and a control device are provided in all stands is taken as an example, but the present invention is not limited to this.
The present invention is also applicable to a case where each of the rolling information measuring device and the control device is provided in at least one stand. For example, in FIG. 3, the rolling information measuring device is connected to a stand S which is a final stand.
7 and the control device may be provided in the S6 stand.

As described above, the rolling apparatus for a metal tube according to the present embodiment is configured. Next, a three-roll sizer including seven stands, a rolling information detector provided on each stand,
A method of rolling a metal tube by the metal tube rolling device of the present embodiment including a control mechanism will be described. In the following description, a case where the rolling information detector is a load cell and the rolling information is a rolling load is taken as an example.

FIG. 4 is a flowchart illustrating a rolling method according to the present embodiment. As shown in FIG. 4, in the present embodiment, when rolling a plurality of metal tubes of the same specification from a plurality of raw tubes of the same specification on the basis of a preset roll reduction position of each stand, Detect the rolling load with the load cell provided on the stand, calculate the deviation from the predicted value of the rolling load, and change the set value of the roll reduction position of each stand at the time of rolling the next raw tube based on the deviation. Rolling is performed under the new conditions that have been changed and set.

The predicted value of the rolling load is determined by conducting a constant-diameter rolling test under various rolling conditions in advance, and determining the appropriate value of each stand that does not generate any burrs and has a good roundness. The appropriate rolling load, and
It can be obtained by storing it in a table stratified by the outer diameter and the material, etc., and pulling out from the stratified table. In addition to creating a rolling load equation,
By grasping the appropriate roll reduction position of each stand in which a metal pipe with no bite and good roundness is obtained in advance, and calculating the rolling load at this appropriate roll reduction position from the rolling load formula, the rolling load is calculated. May be calculated.

In this embodiment, the deviation is reduced to zero.
Adjust the roll-down position of the at least one stand-shaped roll. That is, by adjusting the roll-down position of the hole-shaped roll in at least one of the stand having the deviation and the upstream stand adjacent to the stand, it is possible to suppress the occurrence of the biting flaw.

In particular, when the stand having the deviation is the S7 stand which is the final stand, the occurrence of biting flaws is generated by adjusting the rolling position of the hole type roll of at least one of the S7 stand and the S6 stand. And a metal pipe excellent in roundness can be obtained.

That is, if the actual value of the detected rolling load is smaller than the predicted value of the rolling load in the stands other than the final stand, it is determined that an unfilled phenomenon has occurred in the stand, and the hole-shaped roll of the stand is determined. Is closed, or the roll-down position of the hole-shaped roll of the upstream stand adjacent to the stand is opened.
Also, in the stand except the final stand, if the actual value of the detected rolling load is larger than the predicted value of the rolling load, it is determined that a biting flaw is likely to occur in the stand, and the roll-down position of the grooved roll of the stand is determined. Be open or close the roll-down roll position of the upstream stand adjacent to the stand.

If the detected rolling load at the final stand is smaller than the predicted rolling load, it is determined that an unfilled phenomenon has occurred at the stand, and the roll reduction position of the upstream stand adjacent to the stand is determined. Make it open. In addition, in the final stand, if the actual value of the detected rolling load is larger than the predicted value of the rolling load, it is determined that the stand is likely to cause biting flaws in the stand, and the hole-type roll reduction of the upstream stand adjacent to the stand is determined. Close the position.

In the description of this embodiment, a case where the constant diameter rolling mill is a three-roll sizer is taken as an example. However, the present invention is not limited to this form, and can be similarly applied to a known constant-diameter rolling mill such as a two-roll sizer or a stretch reducer. Further, in the description of the present embodiment, a case where the rolling information detector is a load cell and the rolling information is a rolling load is taken as an example. However, the present invention is not limited to this embodiment, and can be similarly applied to a case where the rolling information detector is an ammeter and the rolling information is a rolling torque.

[0034]

(Embodiment 1) In the basic configuration shown in FIG. 3, each stand is provided with a roll pressing position control device 7, 7, 7, 7.
A rolling device including a three-roll sizer 4 composed of a base stand and load cells as rolling information detectors 5, 5, 5, 5 was used. In each of 1 to 6, two base tubes having an outer diameter of 300 mm and a wall thickness of 14 mm
A test was conducted in which the steel pipe having an outer diameter of 260 mm and a wall thickness of 15 mm was subjected to constant diameter rolling. Roll reduction position control device 6, 6, 6, 6
Has a hydraulic drive mechanism.

The first tube is rolled under the condition of a predetermined roll reduction position. At this time, the rolling load is detected by a load cell provided at each stand, and the predicted rolling load value stored in advance in the stratified table is obtained. Is determined, and based on the deviation, the set value of the roll reduction position of each stand when rolling the second tube is changed and set, and rolling is performed under the changed and set new condition. Was.

The state of occurrence of biting flaws and the roundness of the rolled steel pipe were investigated. For the flaws to be found, the presence of flaws is evaluated by x mark, and the absence of flaws is evaluated by ○ mark. Those with a minimum difference of 0.3 mm or less were evaluated with a mark (pass), and those with a minimum difference of more than 0.3 mm were evaluated with a cross. Table 1 shows the predicted value of the rolling load and the actual value of the rolling load of each stand, the state of occurrence of biting flaws, and the roundness.

[0037]

[Table 1] Test No. In the rolling of the 1st: 1st raw tube, a biting flaw was generated and the roundness was poor. Therefore, the set value of the roll reduction position of the sixth stand was changed so that the rolling load of the sixth stand, in which the actual value of the rolling load was higher than the predicted value, was reduced, and the rolling load of the seventh stand, which was lower than the predicted value, was increased. To roll the second tube.

Test No. 2: In rolling the first tube,
A biting flaw occurred. Then, the set value of the roll reduction position of the sixth stand was changed to lower the rolling load of the seventh stand, in which the actual value of the rolling load was higher than the predicted value, and the second tube was rolled.

Test No. 3: In rolling the first tube,
A biting flaw occurred. Therefore, the second base tube was rolled by changing the set value of the roll reduction position of the third stand so as to reduce the rolling load of the fourth stand where the actual value of the rolling load was higher than the predicted value.

No. 4: In the rolling of the first tube, a biting flaw occurred. Therefore, the set value of the roll reduction position of the fourth stand was changed so that the rolling load of the fourth stand, in which the actual value of the rolling load was higher than the expected value, was reduced, and the second tube was rolled.

Test No. 5: In rolling the first tube,
A biting flaw occurred. Therefore, the second base tube was rolled by changing the set values of the roll reduction positions of the fourth stand and the fifth stand so as to reduce the rolling load of the fourth stand where the actual value of the rolling load was higher than the expected value.

Test No. 6: In rolling the first tube,
A biting flaw occurred. Therefore, the second tube was rolled by changing the set value of the roll reduction position of the second stand and the third stand so as to reduce the rolling load of the fourth stand where the actual value of the rolling load was higher than the expected value.

As shown in Table 1, Test No. 1-6 2
In the rolling of the first raw tube, a steel pipe having good roundness without any biting flaw was obtained. (Embodiment 2) Three roll sizers 4 and rolling information detectors 5, 5, 5 each having seven basic stands each having a roll reduction position control device 7, 7, 7, 7 in each stand in the basic configuration shown in FIG. , 5 using a rolling device equipped with an ammeter, and a test no. In each of 7 to 12,
Two pipes with an outer diameter of 300 mm and a wall thickness of 14 mm
A test was performed in which the steel pipe having a thickness of 0 mm and a thickness of 15 mm was rolled to a constant diameter.

The first tube is rolled under the condition of a predetermined roll reduction position. At this time, the rolling torque is detected by an ammeter provided at each stand, and the rolling torque predicted in advance stored in the stratified table is estimated. The value is determined by changing the set value of the roll reduction position of each stand when rolling the second tube based on the deviation, and rolling is performed under the changed and set new condition. went.

The occurrence of biting flaws and roundness of the steel pipe after rolling were investigated and evaluated in the same manner as in Example 1.
It is shown in Table 2.

[0046]

[Table 2] Test No. 7: In the rolling of the first tube, the roundness was poor. Therefore, the set value of the roll reduction position of the sixth stand is changed so that the rolling torque of the sixth stand, in which the actual value of the rolling torque is higher than the predicted value, is reduced, and the rolling torque of the seventh stand, which is lower than the predicted value, is increased. Then, the second tube was rolled.

Test No. 8: In rolling the first tube,
A biting flaw occurred. Therefore, the second base tube was rolled by changing the set value of the roll reduction position of the sixth stand so as to lower the rolling torque of the seventh stand where the actual value of the rolling torque was higher than the predicted value.

Test No. 9: In rolling the first tube,
A biting flaw occurred. Therefore, the second base tube was rolled by changing the set value of the roll reduction position of the third stand so as to lower the rolling torque of the fourth stand where the actual value of the rolling torque was higher than the predicted value.

Test No. 10: In the rolling of the first tube, biting flaws occurred. Therefore, the second base tube was rolled by changing the set value of the roll reduction position of the fourth stand so as to reduce the rolling torque of the fourth stand where the actual value of the rolling torque was higher than the predicted value.

Test No. 11: In the rolling of the first tube, biting flaws occurred. Therefore, the set values of the roll reduction positions of the fourth stand and the fifth stand were changed so that the rolling torque of the fourth stand, in which the actual value of the rolling torque was higher than the predicted value, was reduced, and the second tube was rolled.

Test No. 12: In the rolling of the first tube, a biting flaw occurred. Therefore, the set value of the roll reduction position of the second stand and the third stand was changed so that the rolling torque of the fourth stand, in which the actual value of the rolling torque was higher than the predicted value, was reduced, and the second tube was rolled.

As shown in Table 2, Test No. In the rolling of the second tube of 7-12, there is no biting flaw,
A steel pipe with good roundness was obtained.

[0053]

According to the present invention, even when the reduction in the distribution of the working degree of each stand is lost due to the wear of the roll and the setting error of the roll reduction position, it is possible to prevent the occurrence of the biting flaw. Thus, a metal pipe having excellent roundness can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically showing a configuration of a three-roll sizer.

FIG. 2 is a side view schematically showing three rolls arranged on each stand of the three-roll sizer, and FIG.
FIG. 2B is a side view as viewed in the direction indicated by the arrow A, and FIG.

FIG. 3 is a schematic diagram schematically illustrating a configuration example of a rolling device for metal tubes of the present embodiment.

FIG. 4 is a flowchart illustrating a rolling method according to the embodiment.

[Explanation of symbols]

 1, S1 to S7: Stand 2: Hole type roll 3: Metal tube 4: 3 roll sizer 5: Rolling information detector 6: Calculation device 7: Roll reduction position control device

Claims (7)

[Claims] 1. A constant diameter rolling mill having a plurality of stands having a plurality of grooved rolls, and rolling of at least one of the plurality of stands when the metal tube is subjected to constant diameter rolling by the constant diameter rolling mill. Rolling information detector to detect information, based on the deviation between the actual value of the rolling information detected by the rolling information detector and the predicted value of the rolling information, the hole shape in at least one of a plurality of stands A rolling device for metal pipes, comprising: a control mechanism for adjusting a rolling position of a roll. 2. The metal tube rolling apparatus according to claim 1, wherein the plurality of grooved rolls are three grooved rolls. 3. A constant diameter rolling method using a constant diameter rolling mill including a plurality of stands having a plurality of grooved rolls,
When manufacturing a plurality of metal pipes of the same specification from a plurality of pipes of the same specification in the constant diameter rolling mill, with respect to any of the second or later raw pipe in the plurality of raw pipes The roll-down position of the grooved roll of at least one of the plurality of stands is set to be equal to or smaller than the number of the second and subsequent ones of the plurality of base tubes that have been rolled to a constant diameter. A method for rolling a metal pipe, wherein the adjustment is performed based on a deviation between an actual value of the rolling information of at least one of the stands and a predicted value of the rolling information. 4. The apparatus according to claim 3, wherein the plurality of grooved rolls are three grooved rolls. 5. The method according to claim 3, wherein the rolling information is a rolling load. 6. The method according to claim 3, wherein the rolling information is a rolling torque. 7. The stand according to claim 3, wherein the stand for adjusting the pressing position of the roll is a stand having the deviation or an upstream stand adjacent to the stand having the deviation. A method for rolling a metal tube as described above.