JP2000176527A - Tube stock rolling method by mandrel mill and mandrel mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tube stock rolling method by a mandrel mill and a mandrel mill used for rolling capable of reducing a dimensional deviation of a rolled tube stock when changing a mandrel bar or a roll of each stand, or when correcting a rolling down reference position of each stand. SOLUTION: An arithmetic unit 5 obtains a first dimensional deviation and a second dimensional deviation using a mandrel bar dimensional error learning quantity ZMj or a roll gap error learning quantity Zc, a number nR of roll gap error learning or a number nM of mandrel bar dimension error learning, further obtains a mandrel bar dimensional error learning gain K and a roll gap learning gain Kc using a first difference between the mandrel bar dimensional error learning quantity Zc and a second difference between the second dimensional deviation and the roll gap error learning quantity Zc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for rolling a hollow tube with a mandrel bar inserted therein by means of a mandrel mill in which a rolling roll is rolled on the outer peripheral surface of the hollow tube, and a mandrel used for carrying out the method. About the mill.

[0002]

2. Description of the Related Art FIG. 7 is a schematic view showing a state where a raw tube is rolled by a mandrel mill. In the figure, reference numeral 1 denotes a hollow raw tube. A cylindrical mandrel bar B having a pointed cylindrical shape is inserted into a base tube 1 formed by piercing a circular column material with a piercer, and the base tube 1 and the mandrel bar B are transported in the arrow direction. A plurality of mandrel bars are prepared for each of a plurality of diameters, and a plurality of mandrel bars belonging to a diameter according to an order are circulated and used.

A plurality of rolling stands # 1, # 2,... Alternately having a pair of vertical rolls and horizontal rolls are arranged in tandem so as to face the transfer region of the raw tube 1 and the mandrel bar B. The rolls 11, 11,... Forming a pair are roll-contacted to the outer peripheral surface of the raw tube 1, and the stands # 1, # 2,. A predetermined roll gap is set in each of the rolling stands # 1, # 2,..., And while the raw tube 1 and the mandrel bar B pass through each of the rolling stands # 1, # 2,. Rolled to a thickness determined by the roll gaps set on the rolling stands # 1, # 2,... And the diameter of the mandrel bar B.

When the rolling of the raw tube 1 is completed, the mandrel bar B is pulled out from the rolled raw tube 1 by a stripper (not shown), and the drawn mandrel bar B is cooled in preparation for the next rolling. .

[0005] With such a mandrel mill, the raw tube 1
In the case of rolling, the deviation between the actual thickness of the tube rolled immediately before and the predetermined target thickness is determined, and the roll gap of each of the rolling stands # 1, # 2, ... is adjusted so that the thickness deviation is reduced. Was.

The thickness deviation may be caused by a roll gap setting error, a dimensional error of the mandrel bar B due to a contact loss with the raw tube 1 and a manufacturing error. The effect of the setting error of the roll gap on the thickness deviation is different from the effect of the dimensional error of the mandrel bar B on the thickness deviation. However, in the above-described conventional method, the two cannot be distinguished. There is a problem that the deviation cannot be sufficiently reduced.

For this reason, Japanese Patent Application Laid-Open No. 61-269909 discloses the following method. The plurality of raw tubes are rolled by the plurality of mandrel bars, and thickness deviations between the actual thickness and the target thickness of the rolled raw tubes are obtained.
The actual thickness of the rolled tube is measured by placing a scale to measure the weight of the tube on the entrance side of the first stand and measuring the length of the rolled tube on the exit side of the final stand. May be obtained by calculation based on the weight of the raw tube measured by the weighing scale and the length of the raw tube measured by the length meter, or may be rolled to the exit side of the final stand. A thickness gauge for measuring the thickness of the raw tube may be provided, and the thickness of the rolled raw tube may be determined by measuring the thickness with the thickness meter.

An average of a plurality of thickness deviations obtained as described above is calculated, and this average thickness deviation is defined as a roll gap-induced thickness deviation caused by a roll gap setting error. Also,
For each mandrel bar, a partial average thickness deviation which is an average of thickness deviations of a plurality of raw tubes obtained by rolling using the mandrel bar is calculated. The difference between the partial average thickness deviation obtained for each mandrel bar and the above-described thickness deviation is obtained, and these are regarded as the mandrel bar-induced thickness deviation caused by the dimensional error of the mandrel bar. And
Based on the mandrel bar-induced thickness deviation and the roll gap-induced thickness deviation relating to the mandrel bar used in the next rolling, the roll gap adjustment amount is calculated, and the roll gap of each stand is adjusted to the obtained adjustment amount. To adjust.

[0009]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open
The method disclosed in JP-A-61-269909 has the following problems. If the mandrel bar or the roll of each stand is replaced with a new one, or if the rolling reference position of each stand is corrected, the thickness deviation due to the mandrel bar and the thickness deviation due to the roll gap obtained as described above are discarded. Using the mandrel bar or roll after replacement, or the corrected draft reference position, again, based on the thickness deviation obtained by rolling a plurality of pipes with a plurality of mandrels, respectively, based on the mandrel bar, The thickness deviation and the thickness deviation due to the roll gap must be calculated respectively. Therefore, the thickness accuracy of the tube rolled during this time is low.

Further, since the thickness deviation due to the mandrel bar and the thickness deviation due to the roll gap are calculated from the calculated thickness deviation or the average value of the measured thickness deviations, the average parameter is small. In this case, the calculation error or the measurement error has a large effect, and the accuracy of the mandrel bar-induced thickness deviation and the roll gap-induced thickness deviation is low. Therefore, there is a limit in reducing the thickness deviation.

The present invention has been made in view of the above circumstances, and its purpose is to replace a mandrel bar or a roll of each stand, or to correct a reference position for rolling down each stand. Even so, it is an object of the present invention to provide a method for rolling a raw tube by a mandrel mill that can sufficiently reduce the dimensional deviation of the rolled raw tube, and a mandrel mill used for carrying out the method.

[0012]

According to a first aspect of the present invention, there is provided a method for rolling a tube using a mandrel mill, comprising: inserting one mandrel bar selected from a plurality of mandrel bars into the tube;
The raw tube and the mandrel bar are fed to a rolling stand provided with a pair of rolls, and when the raw tube is rolled at the rolling stand, a dimensional deviation between the actual size of the previously rolled raw tube and a predetermined target size. Is determined, based on the obtained dimensional deviation, a predetermined rolling set value is corrected, and in the method of rolling the raw tube with the corrected rolling set value, every time the raw tube is rolled, the raw tube is set to the target thickness. The rolling set value error between the rolling set value required for the rolling and the corrected rolling set value is calculated using the first gain determined in accordance with the dimensional deviation and the rolling set value error, and the mandrel bar When calculating the mandrel bar error, which is the error between the reference size and the actual size, using the second gain determined in accordance with the dimensional deviation and the mandrel bar error, the number of times the rolling set value is calculated,
And using the number of times the mandrel bar error related to the mandrel bar is calculated, the first gain and the second gain are determined, and the rolling set value is corrected using the calculated rolling set value error and the mandrel bar error. Features.

In the method for rolling a tube by a mandrel mill according to the second invention, one mandrel bar selected from a plurality of mandrel bars is inserted into the tube, and the tube and the mandrel bar are provided with a pair of rolls. Feeding to a rolling stand, when rolling the tube at the rolling stand, determine the dimensional deviation between the actual size of the previously rolled raw tube and a predetermined target size, based on the obtained dimensional deviation, In the method of rolling the raw tube with the corrected rolling set value, and correcting the determined rolling set value, each time the raw tube is rolled, the rolling set value required for rolling the raw tube to the target thickness and the corrected rolling The rolling set value error from the set value is calculated using the first gain determined corresponding to the dimensional deviation and the rolling set value error, and the obtained rolling set value error is stored, and the rolling set value error is calculated. Count the number of calculations Further, a mandrel bar error, which is an error between the reference size and the actual size of the mandrel bar, is calculated using a second gain determined according to the dimensional deviation and the mandrel bar error, and the obtained mandrel bar error is calculated. Is stored for each mandrel bar, the number of times of calculation of the mandrel bar error is counted for each mandrel bar, the first difference between the partial dimensional deviation and the rolling set value error due to the rolling set value error in the dimensional deviation, Calculated using the stored rolling set value error and the number of times of calculation of the roll set value error, and calculates a second difference between the partial dimensional deviation and the mandrel bar error caused by the mandrel bar error in the dimensional deviation according to the mandrel bar. Calculated using the mandrel bar error stored and stored and the number of times the mandrel bar error is counted according to the mandrel bar. And, first obtained
The first gain and the second gain are calculated based on the ratio of the difference and the second difference.
A gain is obtained, and the rolling set value is corrected using a rolling set value error and a mandrel bar error calculated using the obtained first gain and second gain.

A method for rolling a tube using a mandrel mill according to a third aspect of the present invention is the method according to the first or second aspect, wherein when the rolls are replaced or when the roll reduction reference position is changed, the number of times of calculation of the rolling set value error is increased. Is set to zero.

According to a fourth aspect of the present invention, in the method for rolling a pipe using a mandrel mill according to any one of the first to third aspects, when any one of the mandrel bars is replaced, the number of times of calculating the corresponding mandrel bar error is set to zero. It is characterized by the following.

In the mandrel mill according to the fifth aspect of the present invention, one mandrel bar selected from a plurality of mandrel bars is inserted into a raw tube, and the raw tube and the mandrel bar are fed to a rolling stand provided with a pair of rolls. Then, when rolling the tube at the rolling stand, a dimensional deviation between the actual size of the previously rolled raw tube and a predetermined target size is determined, and based on the obtained dimensional deviation, a predetermined rolling set value. In the mandrel mill that rolls the raw tube at the corrected rolling set value, the rolling set value error between the rolling set value required to roll the raw tube to the target thickness and the corrected rolling set value is the Means for calculating using the first gain determined corresponding to the dimensional deviation and the rolling set value error, means for storing the obtained rolling set value error, means for counting the number of times the rolling set value error is calculated, Mand Means for calculating a mandrel bar error, which is an error between the reference size and the actual size of the mandrel bar, using a second gain determined according to the dimensional deviation and the mandrel bar error, and calculating the obtained mandrel bar error by each mandrel. Means for storing for each bar, means for counting the number of times the mandrel bar error is calculated for each mandrel bar, and a first difference between the partial dimensional deviation and the rolling set value error caused by the rolling set value error in the dimensional deviation, Means for calculating using the stored rolling set value error and the number of times the roll set value error is calculated; and a second difference between the partial dimensional deviation and the mandrel bar error caused by the mandrel bar error in the dimensional deviation, The mandrel bar error stored according to the mandrel bar and the calculated number of mandrel bar errors counted according to the mandrel bar are used. Means for calculating the first difference and the second difference obtained, means for calculating the first gain and the second gain based on the ratio between the first difference and the second difference, Means for correcting the rolling set value using the rolling set value error and the mandrel bar error calculated using the obtained first gain and second gain.

Hereinafter, the present invention will be described using a roll gap which is one of the rolling set values. Assuming that the radial dimension of the mandrel bar is a reference dimension, a roll gap error that is an error between a roll gap required for rolling the raw tube to a target dimension and a corrected roll gap,
Further, a mandrel bar error, which is an error between a reference size in the radial direction of the mandrel bar and an actual size, is learned.

When exponential smoothing learning represented by Zi + 1 = KＫE + (1−K) ・ Zi (where Zi: learning amount, K: learning gain, E: actual deviation) is applied, the rolled element The second difference between the partial dimensional deviation of the mandrel bar due to the radial dimensional error of the mandrel bar and the dimensional error of the mandrel bar in the dimensional deviation of the pipe, and the partial dimensional deviation and the roll gap due to the roll gap error in the dimensional deviation The first difference from the error can be expressed by the following equation (1).

[0019]

(Equation 1)

The dimensional deviation includes a change with time and other disturbances.
The equation (2) having the first-order delay offset γ is rewritten as follows.

[0021]

(Equation 2)

Roll gap error learning amount Z after learning n times
_C (i) and the mandrel bar dimensional error learning amount Z _Mj (i) (mandrel bar error) after learning n times are calculated by the following equations (3) and (4). Z _C (i) = Z _C (i−1) + K _C. Δwt (3) where K _C : roll gap error learning gain (first gain) K _C ≦ 1 Δwt: dimensional deviation between actual dimensions and target dimensions of the rolled raw tube Z _Mj (i) = Z _Mj ( _{i-1) -K M · (} Δwt / R Mj) ... (4) where, K _M: mandrel bar dimension error learning gain (second _{gain) K C + K M ≦ 1} R Mj: radial mandrel bar nominal Dimension (radius)

Roll gap error learning amount Z after learning n times
_C (i) and the number of times of learning (the number of times of calculation) are stored. Further, the mandrel bar dimensional error learning amount Z _Mj (i) after the n-time learning and the number of times of learning (the number of calculations) are stored for each of the plurality of mandrel bars. On the other hand, the initial learning amount of the mandrel bar dimensional error and the initial learning amount of the roll gap error are set in advance. By substituting these numerical values into equation (2), the above-described first difference and second difference are calculated. Then, the mandrel bar dimensional error learning gain K _M and the roll gap error learning gain K _C are obtained by the following equations (5) and (6). K _M: K _C = (the first difference) :( second _{difference) ... (5) K M +} K C = a constant ... (6)

The mandrel bar dimensional error learning gain K _M and roll gap error learning gain K _C obtained in this manner, and the dimensional deviation of the raw pipe rolled immediately before the raw pipe to be rolled are expressed by the following equation (3). The roll gap error learning amount Z _C (i) and the mandrel bar dimensional error learning amount Z _Mj (i) are calculated by substituting into the equation (4), and corrected by substituting them into the following equation (7). The roll gap C is obtained. C = C ₀ −Z _C (i) × 2 + Z _Mj (i) · R _Mj × 2 (7) where C _{0 is a} predetermined roll gap.

When the mandrel bar is replaced, the number of times of learning the dimensional error of the mandrel bar relating to the replaced mandrel bar is set to zero. Further, when the roll of the rolling stand is replaced or when the reference position of the roll is changed, the number of roll gap error learning is set to zero.

Now, let us consider a case where the mandrel bar immediately after replacement with a new one is inserted into a raw tube after the roll gap is corrected a plurality of times, and the raw tube is rolled. In the dimensional deviation of the rolled raw tube, the first difference between the first dimensional deviation caused by the radial dimensional error of the mandrel bar and the dimensional error of the mandrel bar is the second dimensional deviation caused by the roll gap error in the dimensional deviation. It is larger than the second difference between the dimensional deviation and the roll gap error. Therefore, as is apparent from the equations (5) and (6), the mandrel bar dimensional error learning gain KM is _equal to the roll gap error learning gain K _C.
It is set to a larger value.

Therefore, in the equation (7), the learned amount Z _Mj (i) of the mandrel bar dimensional error is largely changed without substantially changing the roll gap error learning amount Z _C (i), and the corrected roll gap is reduced. Is calculated. in this way,
Even if the mandrel bar or the roll of each stand is replaced, or if the reduction reference position of each stand is corrected, the corrected roll gap can be calculated correspondingly, so the rolled raw tube Can be sufficiently reduced.

[0028]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a mandrel mill according to the present invention.
Is a hollow shell. A circular columnar material base tube 1 made by puncturing with piercer, Yes and inserted Togasaki cylindrical mandrel bar B _1, base tube 1 and the mandrel bar B ₁ represents is transported in the arrow direction.

[0029] so as to face the transition zone of the base pipe 1 and the mandrel bar B _1, a plurality of rolling stands ♯1 the pair of vertical rolls and horizontal rolls are provided alternately, # 2, ... it is disposed at appropriate intervals Each rolling stand # 1, # 2,... Rolls a pair of rolls 11, 11,... On the outer peripheral surface of the tube 1 and presses down the tube 1 by the pressing devices 2, 2,. Apply force. Each rolling stand # 1, # 2, the ... Yes set roll gap was calculated as described below, blank pipe 1 and the mandrel bar B ₁ is the rolling stand # 1, # 2, during passage through the ..., mother tube 1 is rolling stand # 1, # 2, the roll gap that is set ... to, and is rolled to a thickness determined by the diameter of the mandrel bar B _1.

When the rolling of the raw tube 1 is completed, the mandrel bar B ₁ is pulled out of the rolled raw tube by a stripper (not shown), and the drawn mandrel bar B ₁ is pulled out.
₁ is transferred to the end of a circulator 7 that circulates a plurality of mandrel bars B _n ,..., B ₃ , B ₂ from the end to the head, where it is cooled in preparation for the next rolling. Next pipe 1
Is supplied from the piercer to the mandrel mill, the mandrel bar _Bn located at the head of the circulator 7 is inserted into the raw tube 1.

The mandrel bar has a plurality of diameters.
Separately several bars B₁, B_Two, ..., B _nAre prepared
Multiple mandrels belonging to the diameter dimension according to the order
Rubber B₁, B_Two, ..., B_nMounted on circulator 7
I have.

The roll-down position controllers 3, 3,... For controlling the roll-down position of the roll are provided corresponding to the respective roll-down units 2, 2,. The corrected roll gap is provided from the arithmetic unit 5 for performing the calculation for correcting the roll gap.

Each of the mandrel bars B ₁ , B ₂ ,..., B _n mounted on the circulator 7 has a different identification number, and the mandrel bars B ₁ , B ₂ ,. B _n and its identification number are tracked by the tracking device 6.
Then, the tracking device 6 gives the arithmetic device 5 the identification number of the mandrel bar B inserted from the circulator 7 into the raw tube 1.

A thickness gauge 8 for measuring the thickness of the rolled raw tube 1 is arranged on the exit side of the final rolling stand.
When the rolled raw tube 1 is sent out from the final rolling stand, the thickness gauge 8 measures the thickness of the raw tube 1 and gives the result to the arithmetic unit 5. The arithmetic unit 5 calculates a corrected roll gap as follows before rolling the raw tube 1 into which the mandrel bar B is inserted, and gives the corrected roll gap to the rolling position control devices 3, 3,.

Each of the rolling position control devices 3, 3
When the corrected roll gaps are given to the rolling rolls 3, 3,..., The rolling down position controllers 3, 3,. Is adjusted to a position corresponding to the correction roll gap.

FIG. 2 is a block diagram showing the configuration of the arithmetic unit 5 shown in FIG. 1. FIGS. 3 and 4 are flowcharts showing the procedure for calculating the corrected roll gap by the arithmetic unit 5 shown in FIG. is there. The arithmetic unit 5 includes a data registration unit 53 in which data such as a target thickness and a roll gap related to the raw tube, and data such as a plurality of identification numbers and radii of the mandrel bars B _{1 to} B _n are registered. Counter 51, which counts the number of times the roll error has been learned (roll gap error learning count n _R ), and mandrel bars B _{1 to} B
_A second counter 52 is provided for counting the number of times that the dimensional error in the radial direction of _n has been learned (mandrel bar dimensional error learning number n _M ) for each of a plurality of identification numbers, and a calculation unit 55 for performing various calculations described later.

The arithmetic unit 55 determines whether a clear command for the first counter 51 and / or the second counter 52 has been given, and if it has been given, the first counter 51 and / or the second counter 52 Is set to zero (steps S1 and S2).

The arithmetic unit 55 calculates the roll gap error learning amount Z _C and the mandrel bar dimensional error learning amount Z _Mj each time the raw tube 1 is rolled as described later, and obtains the obtained roll gap error learning amount Z _C. The learning amount Z _Mj of the mandrel bar dimensional error is _supplied to the learning amount storage unit 56 for each of the plurality of identification numbers, and the learning amount is stored and updated therein, and the first counter 51 and the second counter 52 are updated.

The arithmetic unit 55 is a tube rolled from the thickness gauge 8
Wait until the actual thickness of 1 is given (step S
3). The calculation unit 55 receives the actual thickness from the thickness gauge 8
If it is, read it (step S4) and
From the registration unit 53, the corresponding target thickness of the raw tube 1 is read,
Thickness deviation Δ, which is the difference between the read target thickness and the actual thickness
wt is calculated (steps S5 and S6). The operation unit 55
Roll gap from first counter 51 and second counter 52
Error learning frequency n_RAnd the number of times of mandrel bar size error learning
n_MFrom the learning amount storage unit 56.
Learning error Z _CAnd mandrel bar size error learning amount
Z_MjIs read (step S7).

The following equation (2) is preset in the arithmetic unit 55.
The operation unit 55 calculates y in the expression (2). _nTo mandrel bar
Dimension error learning amount Z_MjOr roll gap error learning amount Z_C
And the number of roll gap error learning times n_ROr ma
Number of times of learning the error of the drel bar n_MBy substituting
Therefore, the mandrel bar
A first dimensional deviation (y) caused by a dimensional error in the radial direction of
Due to roll gap error in dimensional deviation Δwt
The second dimension deviation (y) is obtained (step S8), and the first dimension is calculated.
Deviation and Mandrel Bar Size Error Learning Amount Z_MjFirst difference with
Minute and second dimension deviation and roll gap error learning amount Z_C
Is calculated (step S9). In addition,
(2) y in the equation₀Is set in advance.

[0041]

(Equation 3)

The following formulas (5) and (6) are preset in the arithmetic unit 55, and the arithmetic unit 55 calculates the formulas (5) and (6)
By the equation, obtaining a mandrel bar dimension error learning gain K _M and the roll gap error learning gain K _C (step S10, S11). K _M: K _C = (the first difference) :( second _{difference) ... (5) K M +} K C = a constant ... (6)

[0043] The arithmetic unit 55 Yes to set the following expressions (3) and (4), the arithmetic unit 55, in both equations, the mandrel bar size error learning gain K _M and the roll gap determined as described above By substituting the error learning gain K _C , the roll gap error learning amount Z _C (i-1) and the mandrel bar dimensional error learning amount Z _Mj (i-1) read out from the learning amount storage unit 56, and the thickness deviation Δwt. , Roll gap error learning amount Z _C
(I) and the learning amount Z _{Mj of the} mandrel bar dimensional error (i)
Is calculated (step S12). Z _C (i) = Z _C (i−1) + K _{C. Δwt ... (3) Z Mj (} i) = Z Mj (i-1) -K M · (Δwt / R Mj) ... (4) where, R _Mj: nominal radial dimension of the mandrel bar

The arithmetic unit 55 calculates the roll gap error learning amount Z _C (i) obtained by calculating the roll gap error learning amount and the mandrel bar dimensional error learning amount stored in the learning amount storage unit 56 as described above. ) And the mandrel bar size error learning amount Z _Mj (i), and the first counter 51
Of the roll gap error learning number n _R , and the second counter
52 of the corresponding mandrel bar size error learning frequency n _M respectively increases by 1 (step S13, S14).

The following equation (7) is set in the arithmetic unit 55 in advance. The calculation unit 55 reads a predetermined roll gap C ₀ from the data registration unit 53 to roll the raw tube 1 (step S15), reads the read roll gap C ₀ , and the calculated roll gap error learning amount Z _C ( The modified roll gap C is obtained by substituting the mandrel bar dimensional error learning amount Z _Mj (i) and the mandrel bar radial nominal size R _Mj for each identification number into the equation (7) (step S16). . C = C ₀ −Z _C (i) × 2 + Z _Mj (i) · R _Mj × 2 (7)

In the present embodiment, the thickness of the rolled raw tube 1 is measured by the thickness gauge 8. However, the present invention is not limited to this, and the rolled raw tube 1 is output to the outlet side of the mandrel mill. A length gauge for measuring the length of the tube may be arranged, and a weigh scale for measuring the weight of the raw tube to be rolled may be arranged on the inlet side of the mandrel mill. In this case, the thickness L of the rolled tube is obtained by substituting the length L of the tube measured by the length meter and the weight W of the tube measured by the weight meter into the following equation (8). Calculate T. T = (D / 2) −√ (D / 2) ² −W (1−ΔW / 100) / (πρL) (8) where D: target outer diameter of the rolled raw tube or rolled Outer diameter of raw pipe ΔW: Scale loss rate of raw pipe π: Pi ρ: Specific gravity of raw pipe during rolling

In the present embodiment, the thickness deviation of the rolled tube is reduced. However, the present invention is not limited to this, and the length deviation of the rolled tube is reduced. Needless to say, this may be done.

By the way, the mandrel bar size error learning
Inn K_MAnd roll gap error learning gain K_CAsk for
In steps S8 to S11, the following operation is performed.
May be implemented. That is, the thickness on the right side of the equation (2)
Dimensional deviation due to roll gap error
Is due to mandrel bar dimensional error in thickness deviation
Assuming an approximate value of the dimensional deviation y in advance, the first difference after learning n times
Minute and the second difference (yy)_n), Roll gap learning times
Number n_ROr the number of times of mandrel bar dimensional error learning n _MFunction
Can be expressed as in the following equations (9) and (10).
You. The first difference (yy)₀) = F_M(N_M) (9) Second difference (yy)₀) = F_M(N_R) …(Ten)

The expressions (9) and (10) and (5)
From equation and (6), the following equation for calculating the mandrel bar dimension error learning gain K _M and the roll gap error learning gain K _C (11) and equation (12) below is derived. K _M = g _M (n _M , n _R ) (11) K _C = g _R (n _M , n _R ) (12)

The equations (11) and (12) obtained in this manner are obtained.
The formula is set in the calculation unit 55 in advance. Then, the calculation unit 55
Obtains the mandrel bar dimensional error learning gain K _M and the roll gap error learning gain K _C by equations (11) and (12).

Further, instead of the equation (7) used in step S16, for example, the tension applied to the raw tube 1 is corrected by a sizer (not shown) disposed on the exit side of the final rolling stand. You may use a formula that has been made. Further, the roll gap C ₀ used in step S16 may be registered in the data registration unit 53 in advance, or may be calculated by the arithmetic unit 5 according to rolling conditions based on a predetermined mathematical formula. Good.

[0052]

Next, the results of a comparative test will be described. FIG. 5 is a histogram showing the results of the comparison test. In the figure, the hatched bars indicate the results obtained by the method of the present invention, and the unhatched bars indicate the results obtained in Japanese Patent Application Laid-Open No. Sho 61 (1986).
1 shows the results obtained by the method disclosed in Japanese Patent Application Publication No. 269909. The vertical axis represents frequency, and the horizontal axis represents the ratio of the deviation between the actual thickness and the target thickness to the target thickness.
In the method of the present invention, each time the raw tube was rolled, as shown in FIG. 6, the roll gap error learning gain (◇) and the mandrel bar size error learning gain (〇) were changed to perform rolling.

As is clear from FIG. 5, in the conventional method, the ratio of the deviation between the actual thickness and the target thickness of the rolled raw tube to the target thickness is within ± 0.5% is 68.2%.
Met. On the other hand, in the method of the present invention, the ratio of the deviation between the actual thickness and the target thickness of the rolled raw tube to the target thickness was within ± 0.5% is 83.4%, Was further reduced.

[0054]

As described in detail above, in the present invention,
Even if the mandrel bar or the roll of each stand is replaced, or even if the rolling reference position of each stand is corrected, the present invention is excellent in that the dimensional deviation of the rolled raw tube can be sufficiently reduced. It has the effect.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a mandrel mill according to the present invention.

FIG. 2 is a block diagram illustrating a configuration of the arithmetic device illustrated in FIG. 1;

FIG. 3 is a flowchart showing a procedure for calculating a corrected roll gap by the arithmetic unit shown in FIG. 2;

FIG. 4 is a flowchart showing a procedure for calculating a corrected roll gap by the arithmetic unit shown in FIG. 2;

FIG. 5 is a histogram showing the results of a comparative test.

FIG. 6 is a graph showing a result of changing a roll gap error learning gain and a mandrel bar dimensional error learning gain in the method of the present invention.

FIG. 7 is a schematic diagram showing a state where a raw tube is being rolled by a mandrel mill.

[Explanation of symbols]

 DESCRIPTION OF REFERENCE NUMERALS 1 raw pipe 2 drafting device 3 drafting position control device 5 computing device 6 tracking device 7 circulator 8 thickness gauge B mandrel bar ♯1 rolling stand

Claims (5)

[Claims] Claims: 1. A mandrel selected from a plurality of mandrel bars
This mandrel bar is inserted into the raw tube, and the raw tube and the mandrel bar are fed to a rolling stand provided with a pair of rolls. A method for obtaining a dimensional deviation between a dimension and a predetermined target dimension, correcting a predetermined rolling set value based on the obtained dimensional deviation, and rolling the raw tube with the corrected rolling set value, comprising: Each time rolling is performed, a rolling set value error between a rolling set value required for rolling the raw tube to a target thickness and a corrected rolling set value is determined in accordance with the dimensional deviation and the rolling set value error. Calculate using the gain, also, when calculating the mandrel bar error which is the error between the reference size and the actual size of the mandrel bar, using the second gain determined corresponding to the dimensional deviation and the mandrel bar error, The rolling The first gain and the second gain are determined using the number of times of calculation of the set value and the number of times of calculation of the mandrel bar error related to the mandrel bar, and the rolling setting is performed using the calculated rolling set value error and mandrel bar error. A pipe rolling method using a mandrel mill, wherein values are corrected. 2. One selected from a plurality of mandrel bars.
This mandrel bar is inserted into the raw tube, and the raw tube and the mandrel bar are fed to a rolling stand provided with a pair of rolls. A method for obtaining a dimensional deviation between a dimension and a predetermined target dimension, correcting a predetermined rolling set value based on the obtained dimensional deviation, and rolling the raw tube with the corrected rolling set value, comprising: Each time rolling is performed, a rolling set value error between a rolling set value required for rolling the raw tube to a target thickness and a corrected rolling set value is determined in accordance with the dimensional deviation and the rolling set value error. Calculated using the gain, and stores the obtained rolling set value error, counts the number of times the rolling set value error is calculated, and the mandrel bar error, which is the error between the reference size and the actual size of the mandrel bar, The dimensional deviation and The calculated mandrel bar error is calculated using the second gain determined corresponding to the mandrel bar error, the obtained mandrel bar error is stored for each mandrel bar, and the number of calculation of the mandrel bar error is counted for each mandrel bar. Calculating a first difference between the partial dimensional deviation caused by the rolling set value error and the rolling set value error using the stored rolling set value error and the number of times of calculating the rolling set value error, and calculating the mandrel in the dimensional deviation. The second difference between the partial dimensional deviation caused by the bar error and the mandrel bar error
The difference is calculated using the mandrel bar error stored according to the mandrel bar and the number of times of calculation of the mandrel bar error counted according to the mandrel bar, and based on the ratio of the obtained first difference and second difference. A first gain and a second gain, and correcting the rolling set value using the rolling set value error and the mandrel bar error calculated using the obtained first gain and second gain. Tube rolling method by mill. 3. The method according to claim 1, wherein when the roll is replaced or when the roll reduction reference position is changed, the number of times of calculating the roll set value error is reduced to zero. 4. The method according to claim 1, wherein when any one of the mandrel bars is replaced, the number of times of calculating the corresponding mandrel bar error is set to zero. 5. One selected from a plurality of mandrel bars
This mandrel bar is inserted into the raw tube, and the raw tube and the mandrel bar are fed to a rolling stand provided with a pair of rolls. In a mandrel mill that obtains a dimensional deviation between a dimension and a predetermined target dimension, corrects a predetermined rolling set value based on the obtained dimensional deviation, and rolls the raw tube with the corrected rolling set value, A rolling set value error between a rolling set value required for rolling the raw tube to the target thickness and the corrected rolling set value is calculated using a first gain determined in accordance with the dimensional deviation and the roll set value error. Means, means for storing the obtained rolling set value error, means for counting the number of times of calculation of the rolling set value error,
Means for calculating a mandrel bar error, which is an error between the reference size and the actual size of the mandrel bar, by using a second gain determined in accordance with the dimensional deviation and the mandrel bar error; Means for storing for each mandrel bar, means for counting the number of times the mandrel bar error is calculated for each mandrel bar, and a first difference between the partial dimensional deviation and the rolling set value error caused by the rolling set value error in the dimensional deviation. Means for calculating using the stored rolling set value error and the number of times of calculation of the roll set value error,
The second difference between the partial dimensional deviation and the mandrel bar error due to the mandrel bar error in the dimensional deviation,
Means for calculating using the mandrel bar error stored according to the mandrel bar and the number of times of calculation of the mandrel bar error counted according to the mandrel bar, and means for calculating the ratio between the obtained first difference and the second difference Means for calculating a first gain and a second gain based on a ratio between the first difference and the second difference, and a rolling set value error and a mandrel bar calculated using the obtained first and second gains. Means for correcting a rolling set value using an error.