JP2000246318A - Method and device for controlling outside diameter of seamless pipe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of controlling the outside diameter of a seamless pipe, which can maintain predicted accuracy of heat shrinkage factor at high accuracy not depending on pipe wall thickness and rolling schedule of each process. SOLUTION: In this method to control the outside diameter of a seamless pipe when the seamless pipe is rolled with sizing machine, cooled, and finished to a specified diameter after processes where a heated round billet is drilled to make a hollow pipe and rolled, each temperature distribution on inlet/outlet sides of the processes and on the inlet side of the sizing machine are sequentially determined on the basis of the temperature (S6) of the heated round billet, carrying time (S12) through the processes, and deformation strain volume (S16) through the processes (S14, 18). On the basis of the temperature distribution on the inlet side of the sizing machine and the deformation strain volume due to the target diameter to be rolled with the sizing machine, the temperature distribution of the seamless pipe on the outlet side of the sizing machine is predicted, and the target diameter is set so as to achieve approximate agreement between the target diameter at the average temperature which is calculated from the finished diameter and the target diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seamless pipe outer diameter control method and apparatus for controlling the outer diameter of a seamless pipe at the time of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 7 is an explanatory view for explaining an example of a method of manufacturing a seamless pipe. The manufacturing method of this seamless tube is
A billet 2 (round steel slab) heated to a high temperature in the heating furnace 1 is pierced with a plug core 6 and a plug 5 provided at the tip of the plug core 6 in a piercing machine 3 to form a hollow shell 4. I do. In this process, since the processing heat is generated inside the hollow shell 4, the average temperature of the hollow shell 4 is higher than in the state of the billet 2 before perforation. Further, on the inner surface of the hollow shell 4, a temperature drop occurs due to heat transfer due to contact with the plug 5 and radiant heat to the plug core 6.

[0003] Next, the processed hollow shell 4 is transported to a stretching rolling mill 7 such as a mandrel mill or a plug mill, and is rolled by the stretching rolling mill 7. In this process, when the elongating mill 7 is a mandrel mill, the mandrel bar 8 is inserted into the hollow shell 4, so that radiant heat from the inner surface of the hollow shell 4 to the mandrel bar 8 and heat transfer due to contact are generated. . Further, as in the case of drilling, processing heat is generated inside the hollow shell 4.

Next, the rolled hollow shell 4 is finished into a finished tube 10 having a required hot outer diameter by a constant diameter rolling mill 9 or a stretch reducer mill. During this process,
Processing heat is generated inside the finishing tube 10. Therefore, a temperature difference occurs between the surface temperature of the finished tube 10 and the average temperature inside the tube according to the rolling conditions and the rolling dimensions. Since the heat shrinkage rate before cooling to the final product depends on the average temperature of the finished tube 10, conventionally, the target hot shrinkage based on the tube surface temperature results on the exit side of the constant diameter rolling mill 9 and the predicted surface temperature value is used. By setting the outer diameter, dimensional accuracy is maintained. For this purpose, a surface thermometer 11 and an outer diameter gauge 12 are provided on the exit side of the constant diameter rolling mill 9. Normally, the rolled hollow shell 4 is soaked at a constant temperature in a reheating furnace (not shown). However, in a full retract type mandrel mill or the like, a mandrel mill and a constant diameter rolling mill 9 are arranged in tandem. In some cases, the reheating furnace may be omitted.

[0005]

As described above, since the heat shrinkage rate before cooling to the final product depends on the average temperature of the finished pipe 10, the pipe temperature variation at the time of constant diameter rolling in the final step. Has a large effect on the product dimensions, and a method of feeding forward the temperature on the inlet side of the constant-diameter rolling mill 9, a method of controlling the outer diameter based on the temperature distribution in the longitudinal direction, and the like have been proposed. For example, in Japanese Patent Publication No. 28408/1986,
The temperature at the exit side of the reheating furnace or the exit side of the elongation rolling mill 7 is measured, and based on the actual transfer time from the exit side of the reheating furnace or the exit side of the elongation rolling mill 7 to the constant diameter rolling mill 9, An outer diameter control method for estimating the inlet / outlet pipe temperature and changing the setting of the roll gap of the constant diameter rolling mill 9 has been proposed. In this proposal, it is desirable to construct an empirical formula as a function of the material temperature, the pipe outer diameter, the pipe wall thickness, and the steel type at the exit side of the constant-diameter rolling mill 9, particularly for the calculation of the heat shrinkage, which is a problem.

However, in order to actually improve the accuracy of predicting the thermal shrinkage, it is necessary to construct a huge empirical formula, and a huge number of man-hours and time are required to cope with all kinds of steel types and dimensions. . In particular, when the wall thickness of the pipe becomes thick, a temperature distribution occurs inside the pipe, so it is difficult to estimate the amount of change in the average temperature inside the pipe from the temperature drop calculated from the actual transfer time. An empirical formula representing the relationship between the surface temperature and the heat shrinkage must be constructed.

Further, in the rolling process of the piercing machine 3 and the mandrel mill in the process up to the constant diameter rolling mill 9, heat is transferred from the inside of the pipe to the plug and the mandrel bar. No internal temperature distribution occurs. In particular, in a full-retract type mandrel mill in which a reheating furnace is omitted and a mandrel mill and a sizer mill are arranged in tandem, the temperature difference between the inner and outer surfaces of the tube becomes very large. In Japanese Patent Publication No. Sho 61-28408, although the temperature is actually measured or the temperature is predicted based on the actual transfer time, the prediction accuracy of the heat shrinkage rate is determined by the steel type, the outer diameter and the wall thickness. It depends on the accuracy of the empirical formula for the relationship between the required surface temperature and the heat shrinkage for each case.

The present invention has been made in view of the above-mentioned circumstances, and based on the rolling history from the extraction from the heating furnace to the constant-diameter rolling mill, the temperature distribution in the pipe on the exit side of the constant-diameter rolling mill. By controlling the outer diameter of the seamless pipe and the outer diameter of the seamless pipe, the prediction accuracy of the heat shrinkage can be maintained with high accuracy regardless of the pipe wall thickness and the rolling schedule of each process. It is intended to provide a device.

[0009]

According to a first aspect of the present invention, there is provided a method for controlling the outer diameter of a seamless pipe, comprising: forming a round billet heated by a heating furnace;
After passing through each process of piercing and forming a hollow shell and rolling, the outer diameter of the seamless pipe is controlled by controlling the outer diameter when rolling by a constant diameter rolling mill and cooling to finish it into a seamless pipe with a predetermined finishing diameter In the method, based on the temperature of the round billet heated in the heating furnace, the transport time associated with each step, and the deformation strain of the round billet or the hollow shell associated with each step, Each temperature distribution of the round billet or the hollow shell at the entrance and exit side of the constant diameter rolling mill and the entrance side of the constant diameter rolling mill are sequentially obtained, and the temperature distribution at the entrance side of the constant diameter rolling mill and the constant diameter rolling mill should be rolled. Based on the amount of deformation of the seamless pipe to be given by the target diameter, the temperature distribution of the seamless pipe on the exit side of the constant-diameter rolling mill is predicted, and based on the temperature distribution, the seamless pipe on the exit side of the constant-diameter rolling mill is estimated. Predict the average temperature of the pipe, To substantially match calculated target diameter at the back-calculated the average temperature between the said target diameter, and sets the target diameter.

A method of controlling the outer diameter of a seamless pipe according to a second invention is that a round billet heated in a heating furnace is pierced into a hollow shell by a piercing machine, and then rolled by a rolling mill. When rolling and cooling by a mill to finish a seamless pipe of a predetermined finish diameter, in a seamless pipe outer diameter control method of controlling the outer diameter, the temperature of the round billet heated in the heating furnace and the heating furnace Based on the transfer time up to the punch, the temperature distribution of the round billet on the side of the punch is determined, and the temperature distribution and the amount of deformation strain due to deformation from the round billet to the hollow shell by the punch are determined. Based on the temperature distribution of the hollow shell on the exit side of the drilling machine, based on the temperature distribution and the transport time from the drilling machine to the rolling mill, determine the temperature distribution of the hollow shell on the entrance side of the rolling mill, The temperature distribution and the hollow by the rolling mill Based on the deformation amount of strain the tube, determine the temperature distribution of the hollow shell on the delivery side of the rolling mill, based from the temperature distribution and the rolling mill on the transfer time until the constant 径圧 rolling mill,
The temperature distribution of the hollow shell on the inlet side of the constant diameter rolling mill is determined, and based on the temperature distribution and the deformation strain of the seamless pipe to be given by the target diameter to be rolled by the constant diameter rolling mill, Predict the temperature distribution of the seamless pipe on the exit side, predict the average temperature of the seamless pipe on the exit side of the constant diameter rolling mill based on the temperature distribution, and calculate the target diameter at the average temperature calculated backward from the finish diameter. The target diameter is set so that the target diameter substantially matches the target diameter.

The outer diameter control apparatus for a seamless pipe according to the third invention is characterized in that a round billet heated in a heating furnace is perforated and rolled into a hollow shell, and then rolled by a constant diameter rolling mill. When cooling and finishing to a seamless pipe of a predetermined finishing diameter, a seamless pipe outer diameter control device for controlling the outer diameter, the temperature of the round billet heated in the heating furnace and the respective steps Based on the accompanying transport time and the deformation strain amount of the round billet or the hollow shell involved in each step, the round billet or the hollow shell on the entrance side of each step and the entrance side of the constant diameter rolling mill. Each means for sequentially determining each temperature distribution, and the temperature distribution at the entrance side of the constant diameter rolling mill determined by the means and the deformation strain of the seamless pipe to be given by the target diameter to be rolled by the constant diameter rolling mill Based on the above-mentioned seamless Means for predicting the temperature distribution,
Means for predicting the average temperature of the seamless pipe on the exit side of the constant-diameter rolling mill based on the temperature distribution predicted by the means, and a calculated target diameter and the target calculated back from the finishing diameter at the average temperature predicted by the means. Means for setting the target diameter so as to substantially match the diameter.

In the seamless pipe outer diameter control method according to the first invention and the seamless pipe outer diameter control apparatus according to the third invention, a round billet heated in a heating furnace is perforated to form a hollow shell. After passing through each step of rolling, the outer diameter is controlled when rolling and cooling by a constant diameter rolling mill to finish a seamless pipe having a predetermined finishing diameter. Each means for sequentially determining each temperature distribution is based on the temperature of the round billet heated in the heating furnace, the transport time involved in each step, and the deformation strain of the round billet or hollow shell involved in each step, and Each temperature distribution of the round billet or the hollow shell at the entrance side of the side and the constant diameter rolling mill is sequentially obtained.

The means for predicting the temperature distribution is based on the obtained temperature distribution on the entrance side of the constant diameter rolling mill and the amount of deformation of the seamless pipe to be given by the target diameter to be rolled by the constant diameter rolling mill. The means for predicting the temperature distribution of the seamless pipe on the exit side of the constant diameter rolling mill and estimating the average temperature predicts the average temperature of the seamless pipe on the exit side of the constant diameter rolling mill based on the predicted temperature distribution. The means for setting the target diameter sets the target diameter so that the calculated target diameter at the predicted average temperature, which is calculated backward from the finish diameter, substantially matches the target diameter. Thereby, the prediction accuracy of the heat shrinkage can be maintained with high accuracy regardless of the pipe wall thickness and the rolling schedule of each step.

The outer diameter control apparatus for a seamless pipe according to the fourth invention is characterized in that a round billet heated in a heating furnace is perforated into a hollow shell by a perforator, and then rolled by a rolling mill. When rolling and cooling by a mill to finish a seamless pipe of a predetermined finish diameter, a seamless pipe outer diameter control device for controlling the outer diameter, the temperature and heating of the round billet heated in the heating furnace Means for determining the temperature distribution of the round billet on the inlet side of the drilling machine based on the transfer time from the furnace to the drilling machine, and deformation of the round billet into the hollow shell by the drilling machine by the temperature distribution determined by the means. Means for determining the temperature distribution of the hollow shell on the exit side of the drilling machine, based on the amount of deformation strain caused by this, and rolling based on the temperature distribution determined by the means and the transport time from the drilling machine to the rolling mill. Temperature distribution of the hollow shell on the entry side Means for determining, based on the temperature distribution determined by the means and the deformation strain of the hollow shell by the rolling mill, means for determining the temperature distribution of the hollow shell on the rolling mill exit side, the temperature determined by the means Means for obtaining a temperature distribution of the hollow shell on the inlet side of the constant-diameter rolling mill based on the distribution and the transport time from the rolling mill to the constant-diameter rolling mill, and a target to be rolled by the temperature distribution and the constant-diameter rolling mill. Means for predicting the temperature distribution of the seamless pipe on the exit side of the constant diameter rolling mill based on the deformation strain of the seamless pipe to be given by the diameter, and output of the constant diameter rolling mill based on the temperature distribution predicted by the means. Means for predicting the average temperature of the seamless pipe on the side, and setting the target diameter so that the calculated target diameter calculated from the finish diameter and the target diameter at the average temperature predicted by the means substantially match the target diameter. Means.

In the seamless pipe outer diameter control method according to the second invention and the seamless pipe outer diameter control apparatus according to the fourth invention, a round billet heated in a heating furnace is pierced by a piercing machine to form a hollow element. After being rolled by a rolling mill, the roll is rolled and cooled by a constant diameter rolling mill to finish a seamless pipe having a predetermined finishing diameter. The means for determining the temperature distribution of the round billet obtains the temperature distribution of the round billet on the entrance side of the drilling machine based on the temperature of the round billet heated in the heating furnace and the transport time from the heating furnace to the drilling machine.

The means for determining the temperature distribution of the hollow shell on the exit side of the drilling machine is composed of the temperature distribution determined by the means for determining the temperature distribution of the round billet and the deformation strain due to the deformation from the round billet to the hollow shell by the drilling machine. Based on the above, the temperature distribution of the hollow shell on the exit side of the drilling machine is obtained. The means for determining the temperature distribution of the hollow shell on the rolling mill entrance side is based on the temperature distribution determined by the means for determining the temperature distribution of the hollow shell on the exit side of the drilling machine and the transport time from the drilling machine to the rolling mill. Obtain the temperature distribution of the hollow shell on the entrance side.

The means for determining the temperature distribution of the hollow shell on the exit side of the rolling mill includes the temperature distribution determined by the means for determining the temperature distribution of the hollow shell on the entrance side of the rolling mill and the deformation strain of the hollow shell by the rolling mill. Based on the above, the temperature distribution of the hollow shell on the exit side of the rolling mill is determined. The means for determining the temperature distribution of the hollow shell on the inlet side of the constant diameter rolling mill includes the temperature distribution obtained by the means for determining the temperature distribution of the hollow shell on the exit side of the rolling mill, and the transfer time from the rolling mill to the constant diameter rolling mill. Based on this, the temperature distribution of the hollow shell on the inlet side of the constant diameter rolling mill is determined.

The means for predicting the temperature distribution is a seamless pipe to be given by the temperature distribution determined by the means for determining the temperature distribution of the hollow shell on the inlet side of the constant diameter rolling mill and the target diameter to be rolled by the constant diameter rolling mill. The temperature distribution of the seamless pipe on the exit side of the constant-diameter rolling mill is predicted based on the deformation strain amount. The means for predicting the average temperature predicts the average temperature of the seamless pipe on the exit side of the constant diameter rolling mill based on the temperature distribution predicted by the means for predicting the temperature distribution, and the means for setting the target diameter predicts the average temperature. The target diameter is set so that the calculated target diameter calculated backward from the finish diameter at the average temperature predicted by the means for performing the calculation substantially matches the target diameter.
Thereby, the prediction accuracy of the heat shrinkage can be maintained with high accuracy regardless of the pipe wall thickness and the rolling schedule of each step.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing an embodiment. FIG. 1 is a block diagram showing a configuration of an embodiment of a seamless pipe outer diameter control method and a seamless pipe outer diameter control device according to the present invention. A method of manufacturing a seamless pipe related to the outer diameter control device for a seamless pipe is as follows. A billet 2 (round billet) heated to a high temperature in a heating furnace 1 is connected to a plug core 6 and a plug core 6 in a punch 3. The hollow shell 4 is formed by piercing with a plug 5 provided at the tip. In this process, since the processing heat is generated inside the hollow shell 4, the average temperature of the hollow shell 4 is higher than in the state of the billet 2 before perforation. Further, on the inner surface of the hollow shell 4, a temperature drop occurs due to heat transfer due to contact with the plug 5 and radiant heat to the plug core 6.

Next, the processed hollow shell 4 is conveyed to a stretching mill 7 such as a mandrel mill or a plug mill, and is rolled by the stretching mill 7. In this process, the elongation mill 7
Is a mandrel mill, since the mandrel bar 8 is inserted into the hollow shell 4, radiant heat from the inner surface of the hollow shell 4 to the mandrel bar 8 and heat transfer due to contact are generated.
Further, as in the case of drilling, processing heat is generated inside the hollow shell 4.

Next, the rolled hollow shell 4 is finished into a finished pipe 10 having a required hot outer diameter by a constant diameter rolling mill 9 or a stretch reducer mill. During this process,
Processing heat is generated inside the finishing tube 10. Therefore, a temperature difference occurs between the surface temperature of the finished tube 10 and the average temperature inside the tube according to the rolling conditions and the rolling dimensions. The heat shrinkage before cooling to the final product depends on the average temperature of the finishing tube 10. Normally, the rolled hollow shell 4 is soaked at a constant temperature in a reheating furnace (not shown). However, in a full retract type mandrel mill or the like, a mandrel mill and a constant diameter rolling mill 9 are arranged in tandem. In some cases, the reheating furnace may be omitted.

In the above-described method for manufacturing a seamless pipe, the outer diameter control device 13 for a seamless pipe according to the present invention includes a furnace detector 1c for detecting that the billet 2 has left the heating furnace 1.
, The detection signal is given, the heating temperature at that time is given from the heating thermometer 1b, and the dimension at that time is given from the dimension measuring instrument 1a. The outside diameter control device 13 (seamless tube outside diameter control device) also confirms that the billet 2 has entered the drilling machine 3 and that the billet 2 has been pierced to form the hollow shell 4. The detection signal is given from the input / output detector 3b to be detected, and the diameter and the roll interval of the plug 5 in the final pass of the drilling machine 3 are given from the dimension setting device 3a.

The outer diameter control device 13 also receives a signal from the in / out detector 7b for detecting that the hollow shell 4 has entered the elongating mill 7 and that the hollow shell 4 has been rolled out. The detection signal is given, and the diameter and the roll interval of the mandrel bar 8 of the elongating mill 7 are given from the dimension setting device 7a. The outer diameter control device 13 is also provided with a detection signal from a steel input detector 9b that detects that the hollow shell 4 has entered the constant diameter rolling mill 9, and receives the detection signal at the final roll stand of the constant diameter rolling mill 9. The roll interval is given from the dimension setting device 9a.

The outer diameter control device 1 having such a configuration will be described below.
The operation 3 will be described with reference to the flowcharts of FIGS. When a detection signal indicating that the billet 2 heated to a high temperature in the heating furnace 1 has exited from the heating furnace 1 is given from the furnace output detector 1c (S2), the outer diameter control device 13 sets the time at that time. The memory is stored (S4), and the current heating temperature given from the heating thermometer 1b and the current dimension given from the dimension measuring device 1a are read (S6). Next, when a detection signal indicating that the billet 2 has entered the drilling machine 3 is given from the entry / exit detector 3b (S8), the outer diameter control device 13 stores the time at that time (S10). The time and the billet 2 correspond to the heating furnace 1
From the time (S4) stored at the time of exiting from (S2),
The transfer time between the heating furnace 1 and the punch 3 is calculated (S1).
2).

Next, the outer diameter control device 13 determines a temperature distribution Ti3 in the radial direction of the billet 2 on the entrance side of the drilling machine 3.
(R) is calculated (S14). Here, r represents the position in the radial direction. The temperature distribution Ti3 (r) is given by To1 (r) as the temperature distribution at the time of exiting from the heating furnace 1 and Qo2 as the amount of heat output from the billet 2 at the time of transportation. Ti3 (r) = f (To1 (r) , Qo2) (1). The temperature distribution To1 (r) was read when the billet 2 came out of the heating furnace 1 (S
6) The heat output Qo2 can be calculated from the heating temperature and the dimensions, and the heat output Qo2 is calculated based on the calculated (S12) transport time and the emissivity, heat conductivity, heat transfer coefficient and the like specific to each steel type. .

Next, the outer diameter control device 13 calculates the amount of deformation strain from the billet 2 to the hollow shell 4 in the drilling machine 3 (S16). The amount of deformation strain in the drilling machine 3 is determined by using the outer diameter, wall thickness, and length on the entry side as Di, respectively.
3, WTi3, Li3, the outer diameter, wall thickness on the outlet side,
If the lengths are Do3, WTo3, and Lo3, respectively, the radial strain is φL3, the axial strain is φr3, and the circumferential strain is φθ3, φL3 = Log (Lo3 / Li3) (2) φr3 = Log ( (WTo3 / WTi3) (3) φθ3 = −φL3-φr3 (4) The outer diameter Di3, the thickness WTi3, and the length Li3 on the entrance side are given and read from the dimension measuring device 1a (S6), and the outer diameter Do3, the thickness WTo3, and the length Lo3 on the exit side are determined by the dimension setting device 3a. Given by

Assuming that the equivalent strain representing the entire deformation strain is ε3, ε3 = ((2/9) × ((φL3-φθ3) ² + (φθ3-φr3) ² + (φr3-φL3) ² )) It can be obtained from ^1/2 (5).

Next, the outer diameter control device 13 calculates and stores the temperature distribution To3 (r) of the hollow shell 4 on the exit side of the drilling machine 3 (S18). Qi3 = η × Kf × ε3 (6) where Qi3 is the machining heat generation amount in the process in the drilling machine 3, Kf is the material deformation resistance, and η is the coefficient representing the relationship between the deformation strain amount and the heat generation amount. In addition, since the amount of deformation strain in each step of the piercing machine 3, the stretching rolling machine 7 and the constant diameter rolling machine 9 differs depending on the rolling schedule, each piece (the billet 2 or the hollow shell 4) is calculated using the equation (6). A prediction calculation of the processing calorific value Qi3 is performed online.

The billet 2 in the process in the punch 3
Alternatively, assuming that the amount of heat output from the outer surface of the hollow shell 4 is Qo3 and the amount of heat output from the inner surface of the hollow shell 4 is Qo3 ′, the temperature distribution To3 (r) on the outlet side of the drilling machine 3 is To3 ( r) = f (Ti3 (r), Qi3, Qo3, Qo3 ') (7) The operation of equation (7) is, for example,
It can be executed online using a heat transfer calculation model in which the wall thickness is divided into a plurality of meshes in the radial direction of the tube. The heat output Qo3, Qo3 ′ is determined based on the required time in each step in the drilling machine 3 and the heat transfer by contact with the plug 5 based on the radiation rate, heat conductivity, heat transfer rate, etc., which are specific to each steel type. And the radiant heat to the plug core 6 are calculated.

Next, the outer diameter control device 13 receives a detection signal indicating that the hollow shell 4 pierced in the piercing machine 3 has exited the piercing machine 3 from the in / out detector 3b (S20). The time at that time is stored (S22). Next, when a detection signal indicating that the hollow shell 4 has entered the elongating mill 7 is given from the entry / exit detector 7b (S24), the outer diameter control device 13 stores the time at that time (S24). S
26) From the time and the time (S22) stored when the hollow shell 4 comes out of the drilling machine 3 (S20), the transport time between the drilling machine 3 and the elongation mill 7 is calculated (S2).
8).

Next, the outer diameter control device 13 controls the elongating mill 7
Temperature distribution Ti in the radial direction of the hollow shell 4 on the entry side
7 (r) is calculated (S30). Temperature distribution Ti7 (r)
Can be obtained from Ti7 (r) = f (To3 (r), Qo4) (8), where Qo4 is the heat output from the hollow shell 4 at the time of transfer from the piercing machine 3 to the elongation mill 7. I can do it. Temperature distribution To on the exit side of drilling machine 3 To
3 (r) is calculated by equation (7) and stored (S1
8) The heat output Qo4 is calculated based on the calculated transfer time (S28) and the emissivity, heat conductivity, heat transfer coefficient and the like specific to each steel type.

Next, the outside diameter control device 13
Of the deformation strain of the hollow shell 4 at (S)
32). The amount of deformation strain in the elongating mill 7 is determined by setting the outer diameter, wall thickness, and length on the entry side to Di7, WTi7,
Li7, the outside diameter, wall thickness, and length on the outlet side are Do7, WTo7, and Lo7, respectively, and the radial strain amount is φ.
L7, φr7 for axial strain, φ for circumferential strain
Assuming θ7, φL7 = Log (Lo7 / Li7) (9) φr7 = Log (WTo7 / WTi7) (10) φθ7 = −φL7−φr7 (11) The outer diameter Di7, the wall thickness WTi7, and the length Li7 on the entry side are given from the dimension measuring device 3a, and the outer diameter Do7, the wall thickness WTo7, and the length Lo7 on the exit side are given from the dimension setting device 7a.

Assuming that the equivalent strain representing the entire deformation strain is ε7, ε7 = ((2/9) × ((φL7−φθ7) ² + (φθ7−φr7) ² + (φr7−φL7) ² )) It can be obtained from ^1/2 (12).

Next, the outer diameter control device 13
The temperature distribution To7 (r) of the hollow shell 4 on the outlet side is calculated and stored (S34). Qi7 = η × Kf × ε7 (13), where Qi7 is the processing heat generation amount in the process of the elongating mill 7, Kf is the material deformation resistance, and η is a coefficient representing the relationship between the deformation strain amount and the heat generation amount.

Assuming that the amount of heat output from the outer surface of the hollow shell 4 in the process in the elongating mill 7 is Qo7 and the amount of heat output from the inner surface of the hollow shell 4 is Qo7 ',
The temperature distribution To7 (r) on the outlet side can be obtained from To7 (r) = f (Ti7 (r), Qi7, Qo7, Qo7 ') (14). The heat output Qo7, Qo7 '
By calculating the radiant heat and the heat transfer to the mandrel bar 8 based on each required time in each step in the elongating mill 7 and the emissivity, heat conductivity, heat transfer coefficient and the like specific to each steel type. Ask.

Next, the outer diameter control device 13
When a detection signal indicating that the hollow shell 4 rolled in the above step has exited from the elongating mill 7 is given from the entrance / exit detector 7b (S36), the time at that time is stored (S3).
8). Next, when a detection signal indicating that the hollow shell 4 has entered the constant diameter rolling mill 9 is given from the steel entry detector 9b (S40), the outer diameter control device 13 stores the time at that time. (S42), and from the time and the time (S38) stored when the hollow shell 4 comes out of the elongating mill 7 (S36), the transfer time between the elongating mill 7 and the constant diameter mill 9 is calculated. The calculation is performed (S44). The constant-diameter rolling mill 9 includes the hollow shell 4
Is finished into a finished tube 10 having a required hot outer diameter.

Next, the outside diameter control device 13 is controlled by the constant diameter rolling mill 9.
Temperature distribution Ti in the radial direction of the hollow shell 4 on the entry side
9 (r) is calculated (S46). Temperature distribution Ti9 (r)
Is obtained from Ti9 (r) = f (To7 (r), Qo8) (15), where Qo8 is the amount of heat output from the hollow shell 4 at the time of transfer from the elongating mill 7 to the constant diameter mill 9. I can do it. The temperature distribution To7 (r) on the exit side of the elongating rolling mill 7 is calculated and stored according to the equation (14) (S34), and the heat output Qo8 is calculated (S44). The calculation is performed based on the coefficient, heat conductivity, heat transfer coefficient, and the like.

Next, the outer diameter control device 13 is controlled by the constant diameter rolling mill 9.
A target hot outer diameter (target diameter) of the finishing tube 10 on the outlet side is temporarily set (S48), and the deformation strain amount of the hollow shell 4 is calculated (S50). The amount of deformation strain in the constant-diameter rolling mill 9 is obtained by calculating the outer diameter, the thickness, and the length on the entry side by Di, respectively.
9, WTi9, Li9, the outer diameter and wall thickness on the exit side,
When the lengths are Do9, WTo9, and Lo9, respectively, the radial strain is φL9, the axial strain is φr9, and the circumferential strain is φθ9, φL9 = Log (Lo9 / Li9) (16) φr9 = Log ( (WTo9 / WTi9) (17) φθ9 = −φL9−φr9 (18) The outside diameter Di9, the thickness WTi9, and the length Li9 on the entry side are provided from the dimension measuring device 7a, and the outside diameter Do9, the thickness WTo9, and the length Lo9 on the exit side are provisionally set (S48).

Assuming that the equivalent strain representing the entire deformation strain is ε9, ε9 = ((2/9) × ((φL9−φθ9) ² + (φθ9−φr9) ² + (φr9−φL9) ² )) It can be obtained from ^1/2 (19).

Next, the outer diameter control device 13 controls the constant diameter rolling mill 9.
The temperature distribution To9 (r) of the finishing tube 10 on the outlet side is calculated and stored (S52). Qi9 = η × Kf × ε9 (20) where Qi9 is the processing heat generation amount in the process of the constant diameter rolling mill 9, Kf is the material deformation resistance, and η is a coefficient indicating the relationship between the deformation strain amount and the heat generation amount. .

Assuming that the amount of heat output from the outer surface of the hollow shell 4 in the process in the constant diameter mill 9 is Qo9 and the amount of heat output from the inner surface of the hollow shell 4 is Qo9 ',
The temperature distribution To9 (r) on the outlet side can be obtained from To9 (r) = f (Ti9 (r), Qi9, Qo9, Qo9 ') (21). The heat output Qo9, Qo9 '
It is determined based on each required time in each step in the constant diameter rolling mill 9 and the emissivity, heat conductivity, heat transfer coefficient and the like specific to each steel type.

Next, the outer diameter control device 13 is controlled by the constant diameter rolling mill 9.
Average temperature Tave inside the finishing tube 10 at the outlet side
Is calculated and stored (S54). The average temperature Tave is:
(S52) It can be easily calculated on the basis of the temperature distribution To9 (r) of the finishing pipe 10 at the exit side of the constant diameter rolling mill 9 which is calculated and stored by the equation (21). Next, the outer diameter control device 1 calculates and stores (S54) the average temperature Tave.
Then, the hot target outer diameter Dh is calculated based on the cold target outer diameter Dc (the outer diameter of the final product) (S55).

Here, there is a relationship as shown in FIG. 5 between the average temperature Tave inside the pipe and the heat shrinkage rate. As the average temperature (pipe average temperature) increases, the heat shrinkage rate increases, It turns out to be unique to each. Therefore, the sizing mill 9
Average temperature Tave inside the finishing tube 10 at the outlet side
, It is also possible to predict the heat shrinkage from the time of cooling to the final product, and the constant diameter is calculated from the target cold outer diameter Dc (finished diameter) and the predicted heat shrinkage α (Tave). Hot target outer diameter Dh (calculated target diameter) on the exit side of rolling mill 9
Can be calculated by the following equation. Dh = (1 + α (Tave) / 100) × Dc (22)

Next, the outer diameter control device 13 compares the tentatively set (S48) hot target outer diameter with the (S55) target hot outer diameter Dh calculated by the equation (22) (S56). If they do not substantially coincide with each other, the hot target outer diameter of the finishing tube 10 on the exit side of the constant-diameter rolling mill 9 is temporarily set again (S48), the deformation strain amount is calculated (S50), and the temperature distribution To9 (r) is calculated. Calculation and storage (S52), calculation of the average temperature Tave inside the pipe (S54), and calculation of the target hot outer diameter Dh (S5).
5) A comparison is made between the provisionally set hot target outer diameter (S48) and the calculated hot target outer diameter Dh (S55) (S56).

The outer diameter control device 13 is temporarily set (S4
8) Calculated as hot target outer diameter (S55) Hot target outer diameter D
h substantially coincide with each other (S56), they are provisionally set (S4).
8) The hot target outer diameter is set in the dimension setting device 9a as the hot target outer diameter that is the constant diameter of the constant diameter rolling mill 9 (S58).

The above-mentioned method of making the tentatively set (S48) hot target outer diameter and the calculated (S55) hot target outer diameter Dh substantially coincide with each other is as follows. Various methods are known, such as a method of using the total 12, and these methods are used. Further, it is conceivable that a prediction error occurs in the temperature prediction such as the temperature distribution. However, the measurement result of the surface thermometer 11 on the exit side of the constant-diameter rolling mill 9 and the temperature distribution on the exit side of the constant-diameter rolling mill 9 calculated and predicted are considered. To9 (r) is compared with the surface temperature, and only the deviation is calculated and predicted as the average temperature T.
By using the method of learning and correcting ave, it is expected that the accuracy of prediction calculation of the average temperature Tave will be further improved.

FIG. 6 (b) shows the outer diameter accuracy of the product when the outer diameter control method and the outer diameter control device of the seamless pipe according to the present invention described above are applied. error)
FIG. 6 (a) shows the product outer diameter accuracy (cold cold) when the operation operator manually intervenes to correct the hot target outer diameter based on the surface temperature measured on the exit side of the constant-diameter rolling mill as in the past. 2 is a graph showing an error from a target outer diameter. In the product outer diameter accuracy according to the conventional method, the product outer diameter varies depending on the pipe size and the finishing temperature, but according to the seamless pipe outer diameter control method and outer diameter control device according to the present invention, It can be seen that the hot target outer diameter can be appropriately set irrespective of the wall thickness, material and temperature of the pipe, and the accuracy of the product outer diameter is improved.

[0048]

According to the seamless pipe outer diameter control method and the seamless pipe outer diameter control apparatus of the present invention, the prediction accuracy of the heat shrinkage rate can be improved regardless of the pipe wall thickness and the rolling schedule of each process. It can be held with high precision, and the outer diameter,
The trouble of constructing and calculating an empirical formula for each pipe thickness and steel type can be saved. In addition, the outer diameter accuracy of the product is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of a seamless pipe outer diameter control method and a seamless pipe outer diameter control device according to the present invention.

FIG. 2 is a flowchart showing the operation of the outer diameter control device for a seamless pipe according to the present invention.

FIG. 3 is a flowchart showing the operation of the seamless pipe outer diameter control device according to the present invention.

FIG. 4 is a flowchart showing the operation of the outer diameter control device for a seamless pipe according to the present invention.

FIG. 5 is a graph showing an example of the relationship between the average temperature inside the tube and the heat shrinkage on the exit side of the constant diameter rolling mill.

FIG. 6 is a graph showing the effect of the seamless pipe outer diameter control method and the seamless pipe outer diameter control device according to the present invention.

FIG. 7 is an explanatory diagram for explaining an example of a method of manufacturing a seamless tube.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating furnace 1a Dimension measuring device 1b Heating thermometer 1c Outlet detector 2 Billet (round billet) 3 Drilling machine 3a, 7a, 9a Dimension setting device 3b, 7b In / out detector 4 Hollow shell 5 Plug 6 Plug core metal 7 Stretching Rolling mill 8 mandrel bar 9 constant diameter rolling mill 9b steel entry detector 11 surface thermometer 12 outer diameter gauge 13 outer diameter control device (seamless tube outer diameter control device)

Claims (4)

[Claims] After a round billet heated in a heating furnace is perforated and rolled into a hollow shell, each step is followed by rolling and cooling by a constant diameter rolling mill to form a seamless pipe having a predetermined finishing diameter. Upon finishing, in the outer diameter control method of a seamless pipe for controlling the outer diameter, the temperature of the round billet heated in the heating furnace, the transport time associated with each step, and the round billet associated with each step or On the basis of the deformation strain amount of the hollow shell, the temperature distribution of the round billet or the hollow shell on the entrance side of each step and the entrance side of the constant diameter rolling mill is sequentially obtained, Based on the temperature distribution on the inlet side and the deformation strain of the seamless pipe to be given by the target diameter to be rolled by the constant diameter rolling mill, predict the temperature distribution of the seamless pipe on the exit side of the constant diameter rolling mill, Based on the temperature distribution, Predicting the average temperature of the seamless pipe, the target diameter is set to substantially match the calculated target diameter and the target diameter at the average temperature calculated backward from the finish diameter, Outer diameter control method. 2. A round billet heated in a heating furnace is pierced by a piercing machine to form a hollow shell, rolled by a rolling mill, rolled by a constant diameter rolling mill, cooled, and jointed to a predetermined finishing diameter. In the method of controlling the outer diameter of a seamless pipe for controlling the outer diameter when finishing the pipe, a drilling machine based on a temperature of the round billet heated in the heating furnace and a transfer time from the heating furnace to the drilling machine. Determining the temperature distribution of the round billet on the entrance side, and the temperature of the hollow shell on the exit side of the drilling machine based on the temperature distribution and the amount of deformation strain due to deformation of the round billet into the hollow shell by the drilling machine. Calculating the temperature distribution and the temperature distribution of the hollow shell on the rolling mill entry side based on the temperature distribution and the transport time from the drilling machine to the rolling mill; and deforming the hollow shell by the rolling mill. Rolling mill based on the amount of strain The temperature distribution of the hollow shell on the inlet side of the constant diameter rolling mill is determined based on the temperature distribution and the transport time from the rolling mill to the constant diameter rolling mill. Based on the temperature distribution and the amount of deformation of the seamless pipe to be given by the target diameter to be rolled by the constant diameter rolling mill, the temperature distribution of the seamless pipe on the exit side of the constant diameter rolling mill is predicted. Predicting the average temperature of the seamless pipe on the exit side of the constant diameter rolling mill based on the constant diameter rolling mill, and setting the target diameter so that the calculated target diameter at the average temperature calculated backward from the finish diameter substantially matches the target diameter. A method for controlling the outer diameter of a seamless tube, characterized in that: 3. After the round billet heated by the heating furnace is subjected to the steps of perforating, rolling into a hollow shell, and rolling, the roll is cooled by a constant diameter rolling mill to form a seamless pipe having a predetermined finishing diameter. At the time of finishing, it is a seamless pipe outer diameter control device for controlling the outer diameter, the temperature of the round billet heated in the heating furnace and the transport time associated with each step and the round billet associated with each step or Means for sequentially obtaining the temperature distribution of the round billet or the hollow shell on the inlet and outlet sides of the respective steps and on the inlet side of the constant diameter rolling mill, based on the deformation strain amount of the hollow shell, Based on the determined temperature distribution on the inlet side of the constant diameter rolling mill and the deformation strain of the seamless pipe to be given by the target diameter to be rolled by the constant diameter rolling mill, the seamless pipe on the exit side of the constant diameter rolling mill Means for predicting the temperature distribution of Means for predicting the average temperature of the seamless pipe on the exit side of the constant-diameter rolling mill based on the predicted temperature distribution; and, at the average temperature predicted by the means, the calculated target diameter and the target diameter calculated back from the finishing diameter. Means for setting the target diameter so as to make them substantially coincide with each other. 4. A round billet heated in a heating furnace is pierced into a hollow shell by a piercing machine, rolled by a rolling mill, then rolled and cooled by a constant diameter rolling mill, and cooled to a seam having a predetermined finishing diameter. When finishing to a pipeless, it is a seamless pipe outer diameter control device for controlling the outer diameter, based on the temperature of the round billet heated in the heating furnace and the transfer time from the heating furnace to the drilling machine, Means for determining the temperature distribution of the round billet on the inlet side of the drilling machine; and, based on the temperature distribution determined by the means and the amount of deformation strain due to deformation of the round billet into the hollow shell by the drilling machine, output of the drilling machine. Means for determining the temperature distribution of the hollow shell on the side of the rolling mill, and determining the temperature distribution of the hollow shell on the side of the rolling mill based on the temperature distribution determined by the means and the transport time from the punch to the rolling mill. Means, and a temperature component determined by the means Means for determining the temperature distribution of the hollow shell on the exit side of the rolling mill, based on the deformation strain of the hollow shell by the rolling mill, and the temperature distribution determined by the means and from the rolling mill to the constant diameter rolling mill. Means for calculating the temperature distribution of the hollow shell on the inlet side of the constant diameter rolling mill based on the transfer time of the constant diameter rolling mill; and the deformation strain of the seamless pipe to be given by the temperature distribution and the target diameter to be rolled by the constant diameter rolling mill. Means for predicting the temperature distribution of the seamless pipe on the exit side of the constant-diameter rolling mill based on the amount, and estimating the average temperature of the seamless pipe on the exit side of the constant-diameter rolling mill based on the temperature distribution predicted by the means. And a means for setting the target diameter so that the calculated target diameter calculated backward from the finish diameter at the average temperature predicted by the means substantially matches the target diameter. Pipe outer diameter control device.