JP2010149190A - Rolling apparatus and rolling control method of seamless tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling apparatus of a seamless tube capable of manufacturing a tube of less thickness deviation on the outlet side of a reduction mill or the like for adjusting the outside diameter of the tube without using any inside tool. <P>SOLUTION: The rolling apparatus of the seamless tube includes a rolling mill 11 having a plurality of hole type roll stands to adjust the outside diameter of the tube without using any inside tool, and a rolling control device 16 for individually adjusting the rolling-reduction position of each roll of an intermediate stand with the degree of processing larger than that of a final stand. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a seamless pipe rolling device and a rolling control method capable of reducing uneven thickness in a pipe circumferential direction in a mandrel mill line or a plug mill line.

  FIG. 3 is an explanatory view showing a method of manufacturing a seamless steel pipe by a Mannesmann-mandrel mill method. As shown in FIG. 3, when manufacturing a seamless steel pipe, the billet 51 is first heated to 1200 to 1300 ° C. in a heating furnace 52. Next, the heated billet 51 is pierced and rolled by a piercer 53 to form a hollow shell 54. A mandrel bar 55 is inserted into the hollow shell 54 and stretched and rolled by a mandrel mill 56 to adjust the tube thickness. Thereafter, the mandrel bar 55 is extracted, and a tube is formed into a predetermined diameter by an outer diameter adjusting rolling machine 57 such as a sizer or stretch reducer (hereinafter, the outer diameter adjusting rolling mill is referred to as a drawing mill for convenience) to obtain a product size. Finish. In the mandrel mill 56, the material is constrained by a perforated roll 58 from the outside and a mandrel bar 55 from the inside in a plurality of stands # 1,..., #N, and intersects by 90 ° in a plane perpendicular to the rolling direction. The thickness of the part is rolled alternately. In addition, among each stand of the mandrel mill, the final stand for rolling each portion in the circumferential direction of the hollow shell that is the material to be rolled (that is, the portion rolled at the bottom of the hole-shaped groove of the stand is the subsequent stand) A mandrel mill finishing stand) is called a mandrel mill finishing stand.

  In the mandrel mill, the wall thickness is determined by a geometrically determined distance based on the hole diameter of the hole roll and the outer diameter of the mandrel bar to be used. Therefore, when the finished wall thickness of the seamless steel pipe is different, it is necessary to change the above interval according to the finished wall thickness. As a method of changing this interval, conversion to another mandrel bar with a different diameter is required. There are changes in the roll gap (gap between the mandrel bar and the hole roll) by exchanging the hole roll and adjusting the position of the hole roll.

  However, exchanging the hole-type roll is more time-consuming and impractical than exchanging the mandrel bar. Further, when the roll gap of the mandrel mill is changed, uneven thickness occurs in the circumferential direction. This is because the wall thickness is determined by the gap determined by the hole diameter of the hole-type roll and the outer diameter of the mandrel bar to be used, so that it is formed by a pair of hole-type rolls other than the predetermined roll gap. This is because the hole diameter (shape) changes, and the interval also changes in the circumferential direction.

  FIG. 4 is a schematic diagram showing a relationship between a roll gap and a hole shape in a hole roll having a perfect hole shape, and FIG. 4 (a) shows a pair of hole rolls 61 and a mandrel bar 62. 4B is uniform in the circumferential direction, that is, when the wall thickness is uniform in the circumferential direction, FIG. 4B shows that the wall thickness is non-uniform in the circumferential direction when the roll gap is tightened. Represents the case. 4 (a) and 4 (b), the deepest part of the roll hole mold shown in FIG. 4 (b) is referred to as the groove bottom part 63, and the roll hole type opening part sandwiched between two rolls and not subjected to thickness reduction is referred to as a flange part 64. .

  In the case of FIG. 4B, the gap between the hole roll 61 and the mandrel mill bar 62 becomes the smallest at the portion corresponding to the groove bottom 63 of the hole roll 61, and as it advances toward the flange side of the hole roll 61. The gap between the hole-type roll 61 and the mandrel bar 62 is widened. Therefore, the rolled tube is minimized at the groove bottom 63 of the perforated roll 61 and becomes thicker toward the flange 64.

  The finishing stand of the mandrel mill is usually composed of two stands, and a general method is to use a hole-type roll having the same curvature and set the same roll gap. Since the adjacent stands of the mandrel mill are alternately crossed by 90 ° in the rolling direction, the thickness of the pipe after finishing 2 stands is the minimum thickness at the portion corresponding to the hole roll groove bottom 63 of the finishing 2 stands. Thus, the position shifted by 45 ° is the thickness distribution with the maximum thickness. Therefore, in order to prevent circumferential thickness unevenness in the mandrel mill, it is necessary to have mandrel bars having a large number of dimensions having an outer diameter corresponding to the pitch of the finished wall thickness. Therefore, in the method of exchanging the mandrel bar according to the finished wall thickness, there are problems that many mandrel bars are required and the manufacturing cost increases.

  In order to solve this problem, various methods have been proposed to prevent uneven thickness in the circumferential direction due to the roll gap in order to use a limited mandrel bar and to obtain a finished thickness by changing the roll gap.

  As a countermeasure against uneven thickness in the circumferential direction in the mandrel mill, the raw tube is rolled by two or more two-roll mills continuously arranged with the rolling direction alternately intersecting by 90 °, and then the rolling direction of the two-roll mill is A method (Patent Document 1) is proposed in which the finished wall thickness of a steel pipe is changed by rolling with a roll mill from four directions inclined at 45 ° to shape the pipe shape and changing the roll reduction amount of each roll mill. Yes. Further, in order to make the gap accuracy of the 2-roll mill and the 4-roll mill less than ± 0.1 mm, a hot thickness measuring device is arranged downstream of the 4-roll mill, and the final 3 measured by the hot thickness measuring device. A method (Patent Document 2) for adjusting the roll gap of the last three stands based on the thickness measurement result in the rolling direction of the stand has been proposed.

  FIG. 5 is an explanatory diagram of the roll arrangement of adjacent stands of a three-roll drawing mill, in which FIG. 5 (a) represents an odd-numbered stand and FIG. 5 (b) represents an even-numbered stand. In a drawing mill such as a 3-roll sizer or a 3-roll stretch reducer, as shown in FIGS. 5 (a) and 5 (b), the angle formed by the rolling direction of each roll is 120 ° within a plane perpendicular to the rolling direction. 4 to 28 stands (outer diameter machining) are arranged alternately by shifting the rolling direction of the perforated roll 75 by 60 ° between adjacent stands so that the drive shaft is horizontal. The number of stands is determined according to the degree), and the main pipe 76 is continuously drawn to reduce the outer diameter and slightly reduce the thickness, thereby finishing to a predetermined product size.

  6A and 6B are explanatory diagrams of the angular phase, in which FIG. 6A shows the relationship between the circumferential angle indicating the negative angular phase and the thickness increase rate, and FIG. 6B shows the positive angular phase. This represents the relationship between the circumferential angle and the rate of increase in wall thickness.

  In the single stand rolling of the drawing mill, the rolling groove extends at the bottom of the roll groove as compared with the edge (flange), and the circumferential thickness of the pipe undergoes nonuniform deformation. In rolling with a continuous stand, the roll groove bottom part and the edge part are alternately subjected to plastic deformation alternately for each stand, so that they have almost the same thickness. However, as shown in FIGS. 6 (a) and 6 (b), the roll groove The intermediate point between the bottom part and the edge part is in a negative phase (FIG. 6 (a)) or a thickening phase (FIG. 6 (b)) where the thickness is less than the thickness of the roll groove bottom part and the edge part. Hexagonal squares are produced. This squareness phenomenon tends to increase as the drawing ratio in the longitudinal direction of the pipe in the drawing rolling increases and as the diameter becomes thicker and smaller. Further, the six-direction thick portion generated in the drawing mill overlaps with the four-direction thick portion generated in the mandrel mill at a position shifted by 45 ° from the reduction direction of the mandrel mill. There is a known problem that uneven thickness (uneven thickness) in the circumferential direction is promoted.

  As a countermeasure against the uneven thickness promoted by the drawing mill, the mandrel mill and the drawing mill are arranged in tandem so that the thick-walled portion does not overlap, and one of the reduction directions of the mandrel mill and the reduction of the drawing mill There has been proposed a method (Patent Document 3) in which any of the directions is arranged within a range of ± 5 °.

Japanese Patent Laid-Open No. 6-87008 JP-A-8-71616 JP-A-8-19806

  The inventors of the present invention performed test rolling using the method disclosed in Patent Document 2 and the method disclosed in Patent Document 3 at the same time, but the thickness deviation of the mandrel mill on the mandrel mill exit side is ± Although the thickness could be suppressed to 0.1 mm or less, the thickness deviation in the reduction direction of the mandrel mill and the reduction direction of the reduction mill on the outlet side of the drawing mill could not be suppressed to ± 0.1 mm or less.

  In the test rolling, different thickness deviations are generated for each rolling direction of each roll of the three-roll drawing mill, and the method disclosed in Patent Document 3 includes a reduction of each roll of the three-roll drawing mill. Hexagonal tension that occurs uniformly in the direction can be suppressed, but there is a drawback that it is not possible to suppress the uneven thickness difference for each rolling direction of each roll of the drawing mill.

  Further, in the test rolling, uneven thickness is generated in the drawing mill, and the method disclosed in Patent Document 2 can suppress the uneven thickness of the mother pipe of the reduced rolling mill, but it occurs in the reduced rolling mill. There is a drawback that uneven thickness cannot be suppressed.

  The present invention was made to solve the problems in the mandrel mill and the drawing mill, and has a small unevenness on the outlet side of the drawing mill or the like that adjusts the outer diameter of the pipe without using an inner surface tool. An object of the present invention is to provide a seamless pipe rolling device and a rolling control method capable of manufacturing a pipe.

  The inventors of the present invention conducted intensive test research to achieve the above-described object. As a result, the thickness deviation larger than ± 0.1 mm occurs in the rolling process of both the mandrel mill and the drawing mill, and the cause of the thickness deviation occurring in the mandrel mill is disclosed in Patent Document 2. In addition to the error in setting the roll gap, the fact that the positions of the two opposing rolls are displaced in the direction of the rotation axis, the cause of uneven thickness in the drawing mill, There is a deviation in the stand roll installation position, and this deviation causes the outer diameter reduction amount of the pipe to be uneven in each roll reduction direction, and the increase in the thickness of the pipe increases in the direction in which the outer diameter reduction amount increases. I found out.

  Furthermore, the amount of uneven thickness generated in the mandrel mill is determined almost uniquely for each wall thickness and material of the tube to be rolled in the mandrel mill, unless each roll of the mandrel mill is installed again. The amount of uneven thickness increases in proportion to the outer diameter processing rate in the drawing mill, and the amount of uneven thickness given before the drawing mill decreases on the exit side of the drawing mill, It has been found that the amount of reduction increases substantially in proportion to the outer diameter processing rate in the drawing mill.

  From the above findings, the amount of uneven thickness generated in the mandrel mill and the amount of uneven thickness generated in the drawing mill are formulated using the thickness of the pipe, the material, and the outside diameter processing rate in the drawing mill, Based on this, the amount of uneven thickness applied to the main pipe of the drawing mill is reduced so that the amount of uneven thickness in the rolling direction of the mandrel mill on the exit side of the reduced rolling mill is minimized. In order to obtain a mother pipe, it was investigated that a pipe with a small unevenness can be obtained by adjusting the roll gap of the final two or three stands which are finishing stands of the mandrel mill.

  Alternatively, based on the above-described formula, the amount of uneven thickness applied to the main pipe of the drawing mill is back-calculated so that the amount of uneven thickness in the rolling direction of the drawing mill on the exit side of the drawing mill is minimized. Then, it was investigated that a pipe with a small unevenness can be obtained by individually adjusting the rolling position of each roll of the drawing mill so that the above-calculated master wall with the uneven thickness is obtained.

  Alternatively, on the basis of the above formulated formula, the final two stands that are the finishing stands of the mandrel mill so that the amount of uneven thickness in the mandrel mill reduction direction or the reduction direction of the drawing mill is minimized. By adjusting the roll gap of the three stands or by individually adjusting the reduction position of each roll of the drawing mill, it was investigated that a tube with a small uneven thickness can be obtained.

  From the above-mentioned facts discovered by the present inventors, the amount of uneven thickness on the drawing side of the drawing mill varies depending on the outer diameter processing rate in the drawing mill, and the amount of uneven thickness on the inlet side of the drawing mill is adjusted. Thus, it can be said that the amount of uneven thickness on the outlet side of the drawing mill changes, but this is expressed as follows.

  The case where the following equation is selected as an example of the function f1 in the equation (1) will be described in more detail.

As a result of further diligent test studies, the inventors of the present invention expressed ΔWTS / WTS linearly with respect to ΔWTM / WTM and a and b linearly with respect to ρ as shown in the above equation (2). It has been found that the values of the constants c and d are within the following range.
−0.02 ≦ c (j) ≦ 0 (3)
0.9 ≦ d (j) ≦ 1.1 (4)
Further, the values of the constants e and f were found to be within the following range, although they differ depending on the installation situation of the mill, the dimensions of the pipe, the material, and the like.
−0.002 ≦ e (j) ≦ 0.002 (5)
−0.03 ≦ f (j) ≦ 0.03 (6)
That is, when adjusting the reduction position of each roll of the drawing mill based on the formulated formula, the adjustment amount (the reduction position change amount) of each roll of the drawing mill is the following formula: It should be satisfied.

  Moreover, when adjusting the gap of a mandrel mill based on the formulated formula, the adjustment amount (roll gap deviation) of the roll gap of the mandrel mill should satisfy the following formula.

  The above two formulas defining the adjustment amount of the reduction position of the drawing mill or the adjustment amount of the gap of the mandrel mill can also be expressed as follows. When the outer diameter reduction ratio ρ in the drawing mill is less than 30%, the thickness deviation from the average thickness given by each mandrel mill or each drawing mill stand is controlled within the following range, thereby reducing the uneven thickness. A small tube is obtained.

  As described above, the case where ΔWTS / WTS is formulated linearly with respect to ΔWTM / WTM and a and b are linearly defined with respect to ρ has been described in detail. Of course, other general functions may be selected. Considering that the value is also affected by the pipe material, the rolling position adjustment method can be generally expressed as follows.

  (1) When adjusting the reduction position of a drawing mill:

  In order to be more strict, the following formula may be used instead of the above formula.

  (2) When adjusting the roll gap of the mandrel mill:

  In order to be more strict, the following formula may be used instead of the above formula.

  The present invention has been completed based on the above-described new findings found by the present inventors, and the gist thereof is as follows. That is, the first invention has a plurality of perforated roll stands, and individually adjusts the rolling position for adjusting the outer diameter of the pipe without using an inner surface tool, and the reduction position of each roll of the perforated roll stand. A seamless pipe rolling apparatus comprising a rolling control apparatus.

  According to a second aspect of the present invention, the rolling control device calculates an amount of uneven thickness to be applied to the pipe on the entrance side of the hole-type roll stand, and the roll reduction of each roll of the hole-type roll stand is based on the calculated amount of uneven thickness. The seamless pipe rolling device according to the first aspect, further comprising means for individually adjusting the position.

  A third invention has a plurality of perforated roll stands, a mandrel bar is arranged in a roll perforated array formed by the perforated roll stands, and a mandrel mill for rolling the tube, and a series downstream of the mandrel mill And an extractor for pulling out the tube from the mandrel bar or a rolling mill for adjusting the outer diameter of the tube, and an amount of uneven thickness applied to the tube on the exit side of the mandrel mill. A seamless pipe rolling apparatus comprising: a rolling control device that adjusts a roll gap of the mandrel mill based on a meat amount.

  4th invention is a rolling control method of a seamless pipe which has a plurality of perforated roll stands, and uses a seamless pipe rolling device provided with a rolling mill which adjusts the outside diameter of a pipe without using an inner surface tool. And calculating the uneven thickness applied to the pipe on the inlet side of the perforated roll stand, and individually adjusting the reduction position of each roll of the perforated roll stand based on the calculated uneven thickness. This is a seamless pipe rolling control method characterized by the following.

  A fifth invention has a plurality of perforated roll stands, a mandrel bar is disposed in a roll perforated array formed by the perforated roll stands, and a mandrel mill for rolling the tube, and a series downstream of the mandrel mill A seamless pipe rolling control method that is performed using a seamless pipe rolling device that is arranged and includes an extractor for pulling out the pipe from the mandrel bar or a rolling mill that adjusts the outer diameter of the pipe, It is a seamless pipe rolling control method characterized in that the amount of uneven thickness given to the tube on the outlet side of the mandrel mill is calculated, and the gap of the mandrel mill is adjusted based on the calculated amount of uneven thickness. .

  According to a sixth aspect of the present invention, the rolling control device includes means for individually adjusting a reduction position of each roll of the perforated roll stand based on the following equation: It is a tubeless rolling device.

  A seventh aspect of the invention is the seamless pipe rolling device according to the third aspect, wherein the rolling control device includes means for adjusting a roll gap of the mandrel mill based on the following equation. .

  The eighth invention is the seamless pipe rolling control method according to the fourth invention, characterized in that the rolling position of each roll of the perforated roll stand is individually adjusted based on the following equation.

  A ninth aspect of the invention is the seamless pipe rolling control method according to the fifth aspect of the invention, wherein the roll gap of the mandrel mill is adjusted based on the following equation.

  According to the present invention, a pipe having a uniform wall thickness distribution in the circumferential direction can be obtained by adjusting each roll reduction position of a drawing mill or a roll gap of a mandrel mill finishing stand.

It is a block diagram which shows one Embodiment of this invention. It is a block diagram which shows one Embodiment of this invention. It is explanatory drawing of the manufacturing process of the seamless steel pipe by a Mannesmann-mandrel mill system. It is a schematic diagram which shows the relationship between the roll gap and hole shape in a round hole type roll, The figure (a) is the figure (b) when the space | interval of a hole type roll and a mandrel bar is uniform in the circumferential direction. ) Represents the case where the roll gap is tightened. It is explanatory drawing of the roll arrangement | positioning of the adjacent stand of a 3 roll drawing rolling mill, The figure (a) represents an odd-numbered stand, and the figure (b) represents an even-numbered stand. It is explanatory drawing of a square phase, The figure (a) is the relationship between the circumferential direction angle which shows a negative square phase, and a wall-thickening rate, The same figure (b) is the circumferential direction angle which shows a positive square phase. Represents the relationship with the rate of increase in wall thickness. It is explanatory drawing which shows the direction of thickness measurement. It is explanatory drawing of the name of an angle direction.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing an embodiment of the first invention, the second invention, the fourth invention, the sixth invention, and the eighth invention.
In FIG. 1, 11 is a three-roll drawing mill comprising a plurality of stands # 1,..., #N, 12 is a mother pipe rolled by a mandrel mill, and 13 is a rolling roll of a drawing mill. The rolls in each stand of the three-roll drawing mill 11 are obtained by incorporating three perforated rolls 13 at 120 ° intervals. For example, when viewed from the upstream side of the drawing mill 11, an odd-numbered stand is shown in FIG. As shown in a), the even stands are arranged so that the roll reduction direction intersects by 60 ° between adjacent stands as shown in FIG. 5B. The outer diameter of the mother pipe 12 is drawn by a rolling roll 13 in order from the stand # 1 of the drawing mill, and finished to a predetermined pipe outer diameter.

  Moreover, in FIG. 1, 15 is a calculating device, 16 is each roll reduction device of a drawing mill. The calculation device 15 and each roll reduction device 16 constitute a rolling control device. The arithmetic unit 15 determines the bias to be applied to the inlet pipes of the # 1 and # 2 stands of the drawing mill based on the formula given in advance based on the tube thickness, the material, and the outer diameter processing rate in the drawing mill 11. The amount of meat is calculated, and the amount of change in the rolling position of each roll of the # 1 and # 2 stands of the drawing mill necessary to give the uneven thickness is calculated.

  Formulas for calculating the amount of uneven thickness to be given to the inlet pipes of the # 1 and # 2 stands of the drawing mills incorporated in the arithmetic unit 15, and # 1 and # required to give the amount of uneven thickness An expression for obtaining the amount of change in the rolling position of each roll of the two stands can be obtained, for example, by the following experiment.

  7A and 7B are explanatory views showing the direction of thickness measurement. FIG. 7A shows the case of the tube A, and FIG. 7B shows the case of the tube B. FIG. In the mandrel mill 56 shown in FIG. 3, the hollow shell 54 is first rolled by a normal manufacturing method. At this time, during mandrel mill rolling, the outer surface of the upper pipe end of the pipe is provided with a ridge on the downstream side of the mandrel mill so that it can be identified which direction of the pipe has been reduced by the mandrel mill. Next, the mother tube rolled by the mandrel mill is drawn by a drawing mill 57, and the drawn tube (tube A) has a thickness T1, T1 ′, corresponding to the rolling direction of the last two stands of the mandrel mill. T2 and T2 ′ (see FIG. 7A) are measured.

  Next, a hollow element tube 54 having the same dimensions and material as the hollow element tube used when the tube A is rolled is used in the mandrel mill 56 by using the same mandrel bar 55 as when the tube A is rolled. Except for the point, the tube A is rolled at the same setting as when rolled. That is, the setting is different from when the tube A is rolled, and when the number of mandrel mill stands is N, in the # N-1 stand, the gap between the rolling roll and the mandrel bar is increased by 0.5 mm. Conversely, in the #N stand, the roll reduction position of the last two stands is adjusted so that the gap between the rolling roll and the mandrel bar is reduced by 0.5 mm. In the same way as when the tube A is rolled, during the mandrel mill rolling, the outer surface of the upper tube end portion of the tube is provided with a wrinkle downstream of the mandrel mill, and which direction of the tube is reduced by the mandrel mill. Keep it distinguishable.

  Next, the master tube rolled by the mandrel mill is drawn by the drawing mill 57, and the thickness T3, T3 ′, T4, T4 in the down direction of the last two stands of the drawn mandrel mill (tube B) is drawn. '(See FIG. 7B) is measured.

  Based on the above experiment, the following equation shows how much the amount of uneven thickness generated in the drawing mill and the amount of 1.0 mm unevenness given before the drawing mill decreases on the exit side of the drawing mill. (15).

  Further, by performing the same experiment by changing the outside diameter processing rate in the drawing mill, the amount of reduction on the outlet side of the drawing mill of 1.0 mm uneven thickness given in front of the drawing mill ( Expression (15) a) and the outlet thickness deviation (b in Expression (15)) of the drawing mill can be obtained as a function of the outer diameter processing amount. In addition, by measuring the thickness of the pipe in the rolling-down direction of the drawing mill of the pipe that has been drawn for each material, the thickness of the pipe and the amount of uneven thickness for each material can be obtained. The following equation (16) obtained in this way is incorporated in advance in the arithmetic unit 15 as an equation for calculating the amount of uneven thickness to be given to the inlet pipes of the # 1 and # 2 stands of the drawing mill. ing.

  ΔWTS / WTS is a function of ΔWTM / WTM, and a and b are functions of ρ, but in equation (16), ΔWTS / WTS is simply made linear with respect to ΔWTM / WTM, and a and b b was linear with respect to ρ. The present invention is not limited to this, and based on the experimental results, for example, a stricter expression such as the following expression (17) may be incorporated in the arithmetic unit 15.

  Furthermore, the amount of change δ (# 1) of the uneven thickness amount ΔWTS after the drawing rolling when the rolling position of the # 1 stand is changed by 1 mm is shown by an experiment in which the rolling position of the # 1 stand of the rolling mill is changed and rolled. # 1 stand of the drawing mill when the reduction position of the # 1 stand is changed by 1 mm by measuring and calculating back the equation (16) using the outer diameter reduction ratio ρ in the drawing mill after the # 2 stand The thickness variation amount pS (# 1) at can be obtained as follows.

  Similarly, for the # 2 stand, by changing the rolling position of the # 2 stand and performing rolling, the change amount δ (# 2) of the uneven thickness amount ΔWTS after the drawing rolling when the rolling position of the # 2 stand is changed by 1 mm. ), And by calculating back the equation (16) using the outer diameter reduction ratio ρ in the drawing mill after the # 3 stand, the reduction position of the # 2 stand of the drawing mill is changed by 1 mm. The uneven thickness variation amount pS (j) in the two stands can be obtained as in the following equation (19).

  In order to determine the amount of change in the rolling position of each roll of the # 1 and # 2 stands, which is necessary to give the thickness deviation to the inlet pipes of the # 1 and # 2 stands of the drawing mill, The obtained equations (18) and (19) are incorporated in the arithmetic device 15 in advance.

  Based on the equation (16), the arithmetic unit 15 calculates the thickness deviation amount ΔWTM in each of the rolling down directions (six directions) to be given by the # 1 and # 2 stands. Further, the amount of change in the reduction position of each roll of the # 1 and # 2 stands required to obtain the uneven thickness ΔWTM is calculated based on the equations (18) and (19), and the calculated # 1, # The amount of change of the rolling position of each roll of the two stands is commanded to each rolling machine 16 of the # 1 and # 2 stands of the drawing mill, and the rolling position of each roll is adjusted individually.

  To summarize the configuration described above, the following equation (20) is obtained.

  Equation (20) may be solved as follows, for example. For each of j = 0 °, 60 °, 120 °, 180 °, 240 °, and 300 °, ΔWTS (i, j) other than i = 1, 2 is set to 0, and ΔWTS (1, j) and ΔWTS ( 2, j) and then ΔGS (i, j) is derived from ΔWTS (i, j). Here, when ΔGS (i, j) exceeds the mechanically settable range, ΔGS (i, j) is set to a value within an allowable range, and i = 1, 2, 3, 4 ΔWTS (i, j) other than the above is set to 0 to obtain ΔWTS (3, j) and ΔWTS (4, j), and then ΔGS (i, j) is derived from ΔWTS (i, j). This step can be repeated until a solution is obtained. Hereinafter, this method is referred to as method A.

  By being configured as described above, the calculation device 15 is required to make the amount of deviation in the rolling direction (six directions) of the drawing mill on the exit side of the drawing mill 11 zero. The amount of change in the rolling position of each roll of the stand is calculated based on Equation (16), Equation (18) and Equation (19), and the amount of change in the rolling position of each calculated roll is calculated for each of # 1 and # 2 stands. A command is given to the roll reduction device 16 to adjust the reduction position of each roll individually. Therefore, the thickness distribution in the rolling direction of the # 1 and # 2 stands of the drawing mill is made uniform, and uneven thickness in the circumferential direction of the tube 12 can be suppressed.

The present invention can also be carried out in the following manner even in a drawing mill without a reduction adjusting mechanism, that is, a calculation device 15 and a drawing mill without each roll reduction device 16 of the drawing mill.
That is, based on the equation (16), the thickness deviation in each of the reduction directions (6 directions) to be given by the # 1 and # 2 stands is calculated in advance. Further, the amount of change in outer diameter reduction amount in the roll reduction direction of each of the # 1 and # 2 stands required to obtain the uneven thickness is calculated based on the equations (18) and (19), and the calculated outer diameter The cutting amount of the roll in the roll reduction direction of each of the # 1 and # 2 stands is adjusted based on the reduction amount of the reduction amount. That is, the roll is cut so that the roll diameter difference in the roll reduction direction of each of the # 1 and # 2 stands coincides with the calculated outer diameter reduction amount in each roll reduction direction.

  The configuration described above will be specifically described with Expression (20). Here, the minimum value of the number of used stands of the drawing mill is Nmin. Note that, in a drawing mill without a reduction position adjusting mechanism, when the number of stands used for the drawing mill is determined, the outer diameter reduction amount of the drawing mill is generally determined.

  First, the outer diameter reduction amount change amount in the roll reduction direction of each of the # 1 and # 2 stands when the number of used stands is Nmin is determined. For each of j = 0 °, 60 °, 120 °, 180 °, 240 °, and 300 °, ΔWTS (i, j) equal to or greater than i = Nmin + 1 is set to 0, and ΔWTS (i, j) is obtained, and ΔGS (i, j) is derived from the obtained ΔWTS (i, j). Next, the outer diameter reduction amount change amount in the roll reduction direction of each of the # 1 and # 2 stands when the number of used stands is Nmin + 1 is determined. For each of j = 0 °, 60 °, 120 °, 180 °, 240 °, and 300 °, ΔWTS (i, j) where i = Nmin or less is the value of ΔWTS (i, j) obtained as described above. ΔWTS (i, j) equal to or greater than i = Nmin + 2 is set to 0, and ΔWTS (Nmin + 1, j) is obtained by reversely calculating the equation (20), and ΔGS (Nmin + 1, j) is obtained from the obtained ΔWTS (Nmin + 1, j). Nmin + 1, j).

This step is repeated until i reaches the maximum number of used stands, and the rolls in the rolling direction of each stand of the drawing mill may be cut in accordance with ΔGS (i, j) obtained here.
By being configured as described above, each roll roll-down direction of # 1 and # 2 stands required to make the amount of uneven thickness in the roll-down direction (6 directions) of the drawing mill on the exit side of the drawing mill zero. The outer diameter reduction change amount is calculated based on the equations (18) and (19), and the cutting amount of each roll is adjusted according to the calculated outer diameter reduction change amount. Therefore, the thickness distribution in the roll down direction of the # 1 and # 2 stands is made uniform, and uneven thickness in the circumferential direction of the tube 12 can be suppressed.

Next, embodiments of the third invention, the fifth invention, the seventh invention and the ninth invention will be described. FIG. 2 is a block diagram showing an embodiment of the third, fifth, seventh and ninth inventions.
In FIG. 2, 31 is a mandrel mill composed of a plurality of stands # 1,..., #N, 32 is a hollow shell (element tube) perforated by a piercer, 33 is a mandrel bar, 34 is a mandrel mill rolling roll, Reference numeral 35 denotes a three-roll extractor or drawing mill composed of a plurality of stands # 1,..., #N.

  The mandrel bar 33 pierced by the piercer is inserted into the mandrel bar 33 and the rear end of the mandrel bar 33 is held at a constant speed by a holding device (not shown). It is drawn and rolled by a perforated rolling roll 34.

  After the rolling is completed by the mandrel mill 31, the mandrel bar 33 is stopped, and the mother pipe 32 is pulled out from the mandrel bar 33 by the extractor 35. The rolls in each stand of the three-roll extractor and the drawing mill 35 are obtained by incorporating three perforated rolls 36 at intervals of 120 °. As shown in FIG. 5 (a), the even stands are arranged so that the roll reduction direction intersects 60 ° between adjacent stands as shown in FIG. 5 (b). The outer diameter of the mother pipe 32 rolled by the mandrel mill 31 and drawn from the mandrel bar 33 is drawn by the rolling roll 36 in order from the stand # 1 of the drawing mill and finished to a predetermined pipe outer diameter.

  In FIG. 2, reference numeral 38 denotes an arithmetic unit, and 39 denotes a roll finishing device for finishing 2 stands, which is a mandrel mill finishing stand. The calculation device 38 calculates the amount of uneven thickness to be given to the mandrel mill outlet side based on the formula (16) given in advance from the tube thickness, material, and outer diameter processing rate in the drawing mill 35. . Further, the amount of change in the reduction position of the two mandrel mill finishing two stands required to give the uneven thickness is calculated.

  Expression (16) is incorporated in the arithmetic device 38 in advance. In the arithmetic unit 38, the thickness deviation amount ΔWTM in each of the rolling-down directions (four directions) of the finishing two stands of the mandrel mill is calculated based on the equation (16). Further, the calculation device 38 calculates the change amount of the gap of the mandrel mill finish 2 stand necessary for obtaining the uneven thickness amount ΔWTM, and calculates the calculated change amount of the gap to each roll reduction device of the mandrel mill finish 2 stand. 39 and adjust the roll gap.

  When the configuration described above is arranged, the following equation (21) is obtained.

  With the above-described configuration, the arithmetic unit 38 can perform the mandrel mill finishing necessary for reducing the thickness deviation in the rolling direction (four directions) of the mandrel mill finishing 2 stand on the exit side of the drawing mill 35 to zero. The change amount of the roll gap of the two stands is calculated based on the formula (16), and the calculated change amount of the roll gap of the two mandrel mill finishing two stands is commanded to each roll reduction device 26 of the two mandrel mill finishing two stands. Adjust. Therefore, the thickness distribution in the roll down direction of the two mandrel mill finishes 2 is made uniform, and uneven thickness in the circumferential direction of the pipe 32 can be suppressed.

  In the embodiments corresponding to the first invention, the second invention, the fourth invention, the sixth invention and the eighth invention, the reduction position adjusting stand of the drawing mill is limited to # 1, # 2, but the present invention Is not limited to this, and the reduction position may be adjusted with a stand that performs outer diameter machining other than # 1 and # 2, or between # 1 and # 2 and stands other than # 1 and # 2. You may adjust a reduction position by both. When adjusting the reduction position with a plurality of stands of a drawing mill, the sum of the thickness deviations provided at each stand may be the thickness deviation to be corrected.

  In the embodiments corresponding to the third invention, the fifth invention, the seventh invention, and the ninth invention, the finishing stand of the mandrel mill is limited to the finishing two stands, but the present invention is not limited to this. The roll gap may be adjusted by finishing 3 stands.

  In the above description, the drawing mill has three rolls, but even if the drawing mill has two rolls or four rolls or more, uneven thickness can be suppressed by the same method. Further, although the mandrel mill is a two-roll mill, uneven thickness can be suppressed by the same method even if it is a three-roll mandrel mill or a four-roll mandrel mill having two or more stands.

  A raw tube having an outer diameter of 320.0 mm and a wall thickness of 30.0 mm is rolled by a 5-stand 2-roll mill continuously arranged with the rolling direction alternately crossed by 90 °, and then, with respect to the rolling direction of the 2-roll mill. A mandrel mill rolled with a roll mill from four directions inclined at 45 ° was stretch-rolled to an outer diameter of 276.0 mm and a wall thickness of 15.0 mm, and then an outer diameter of 219.0 mm and a meat by a three-roll drawing mill comprising 8 stands. Rolled to a thickness of 16.2 mm.

(Invention Example 1)
After drawing and rolling with a mandrel mill, the amount of change in the reduction position of each roll of the drawing mills # 1 and # 2 stands is calculated based on the formula (20), and the reduction rolling machine is calculated based on the calculated amount of change in the reduction position. The roll reduction positions of the # 1 and # 2 stands were individually adjusted and subjected to constant diameter rolling with a drawing mill.

(Invention Example 2)
Based on the formula (21), the amount of change in the reduction position of the three mandrel mill finishing stands (8 directions) was calculated, and the roll reduction position of each roll of the three mandrel mill finishing stands was adjusted based on the calculated amount of change in the reduction position. In this state, after stretching and rolling with a mandrel mill, constant diameter rolling was performed with a drawing mill.

(Invention Example 3)
After drawing and rolling with a mandrel mill, the change amount of the reduction position of each roll of the # 1 and # 2 stands of the drawing mill is calculated based on the following formula (22), and the drawing is performed based on the calculated change amount of the reduction position. The roll reduction positions of the # 1 and # 2 stands of the rolling mill were individually adjusted and subjected to constant diameter rolling with a drawing mill.

(Invention Example 4)
Based on the following formula (23), the amount of change in the reduction position of the 3 mandrel mill finish stands (8 directions) was calculated, and the roll reduction position of each roll of the 3 mandrel mill finish stands was adjusted according to the change amount of the calculated reduction position. In this state, after stretching and rolling with a mandrel mill, constant diameter rolling was performed with a drawing mill.

(Comparative example)
As a comparative example, Japanese Patent Application Laid-Open No. 8-71616 measures wall thickness downstream of a mandrel mill and adjusts each roll reduction position of the mandrel mill finishing stand so that the pipe is close to a perfect circle on the exit side of the mandrel mill. Rolled by the conventional method shown in

  Table 1 shows the results of comparison of the wall thickness distributions after constant diameter rolling for each of Invention Example 1, Invention Example 2, Invention Example 3, Invention Example 4, and Comparative Example.

  As shown in Table 1, Examples 1-4 of the present invention, in which the reduction position of the mandrel mill or the drawing mill was adjusted, had an uneven thickness ratio improved by about 2-3% as compared with the comparative example.

11, 35, 57: drawing mill,
12, 32, 54, 76: Raw tube,
13, 36, 75: rolling rolls of a drawing mill,
15, 38: arithmetic unit,
16: A rolling roll reduction device of a drawing mill,
31, 56: Mandrel mill,
33, 55, 62: Mandrel bar,
34, 58, 61: mandrel mill rolling rolls,
39: Mandrel mill rolling roll reduction device,
51: Billet,
52: heating furnace,
53: Piasa,
58: Product,
63: groove bottom,
64: Flange part.

Claims (1)

  A rolling mill having a plurality of perforated roll stands and adjusting the outer diameter of the pipe without using an inner surface tool, and each of the intermediate stands having a working degree larger than the working degree of the final stand among the perforated roll stands. A seamless pipe rolling apparatus, comprising: a rolling control apparatus that individually adjusts a roll reduction position.

Images