JPS59104209A - Method for controlling outer diameter of seamless pipe - Google Patents

Abstract

PURPOSE:To obtain a pipe having a uniform outer diameter in a cold state by estimating the amount of heat shrinkage of the outer diameter of a blank pipe at the time when cooled to a cold state in accordance with the temperature distribution in the axial direction of the pipe, and setting and controlling roll gaps in a sizer basing on the amount of heat shrinkage. CONSTITUTION:A blank pipe P is introduced by providing a thermometer 2 to the inlet side of a sizer 1 to obtain the deviation of temperature between the top and the bottom of the pipe P, and the deviation of the amount of shrinkage of its outer diameter at the time when cooled to a cold state is estimated. Next, for eliminating this deviation, the dimension of its outer diameter in hot state is calculated by an arithmetic unit 4, and the roll gaps at the rolls 24, 25 of stands 14, 15 are calculated at each part of the pipe P and the results are stored. Next, a speed of pipe P is calculated basing on the signal of a speedometer 3, and the delay time that each position of pipe P arrives at the stands 14, 15 is obtained to control the roll gaps at the roll 24, 25 to said calculated values respectively immediately before the arrivals by means of rolling reduction motors 44, 45, thereby performing a sizing. Thus, a pipe having a uniform outer diameter in a cold state is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the outer diameter of a seamless pipe, which makes it possible to improve the accuracy of the outer diameter of the seamless pipe, particularly on the bottom side.

In general, a tube that has been elongated and rolled using a plug mill, etc. is polished and shaped using a reeler, and then finished using a sizer to meet the specified dimensional specifications. It is known that there is a relationship between Particularly in the case of seamless pipes, when using the Mannesmann plug mill method, reeling is performed in the pre-sizing process, but the reeling process takes about 20 to 30 seconds for the top and bottom of the pipe. Because of this difference, the temperature in the reeled tube is about 40 to 60 degrees Celsius higher at the bottom than at the top of the tube. Therefore, if such a tube is passed through a sizer with a constant roll gap, the outer diameter will be uniform in the hot state immediately after sizing, but the heat shrinkage rate on the bottom side, where the temperature is higher, will be higher than on the top side. Because of its large diameter, there was a problem in that in cold conditions, the outer diameter of the tube became smaller at both the top and bottom sides of the tube.

The present invention has been made in view of the above circumstances, and its purpose is to take into account the amount of heat shrinkage when the reeled tube reaches a cold state, and to An object of the present invention is to provide a method for controlling the outer diameter of a seamless pipe, by which a pipe with a uniform outer diameter can be obtained under cold conditions by setting and controlling the gap.

The method for controlling the outer diameter of a seamless pipe according to the present invention measures the temperature of each part in the axial direction of the raw pipe at the entry side of the sizer, detects the temperature difference of each part in the axial direction with respect to the temperature at the tip of the raw pipe, and The sizer roll gap is set and controlled according to the difference so that the outer diameter of each part in the axial direction becomes uniform after the tube is cooled.

The present invention will be specifically explained below based on the drawings.

FIG. 1 is a schematic diagram showing the implementation state of the method for controlling the outer diameter of a seamless pipe according to the present invention, in which P indicates a raw pipe and 1 indicates a sizer. The raw pipe P passes through a plug mill and a reeler (not shown), is maintained at a temperature of approximately 70°C, is introduced into the sizer 1 from the direction of the white arrow, and is finished to the required outer diameter dimension, and then cooled to approximately 70°C in the cooling process. It is then cooled down to a certain temperature and then transported to the finishing and inspection process. sizer 1 is 5
In the case where it consists of stands, the first stand l1
The caliber diameters of the caliber rolls 21, 22, . . . 25 in the 1st second stand 2, . The roll gaps of the caliber rolls 21 to 25 are appropriately set by rolling down motors 41 to 45 connected to the respective roll shafts via rolling down screws 31 to 35. There is.

On the entry side of sizer 1, the raw pipe P is placed facing the moving area of the raw pipe P.
A non-contact thermometer 2 that measures the surface temperature of the tube P
A speedometer 3 is provided to detect the moving speed of the vehicle.

The speedometer 3 pivotally connects one arm of the bell crank 3c of the air cylinder 3a, and the bell crank 3c.
The roll 3d is pivotally supported on the narrow arm of the roll 3d, and a pulse generator PG1 is attached to the shaft of the roll 3d.By operating the air cylinder 3a, the roll 3d is moved around the circumference of the base pipe P corresponding to the thermometer 2. Roll 3
Pulses are output from the pulse generator PG according to the rotational speed of d.

Reference numeral 4 denotes an arithmetic control unit which reads at a predetermined timing the surface temperature of the raw pipe P measured from the top to the bottom while the raw pipe P moves under the thermometer 2, and also reads the surface temperature of the raw pipe P from the top to the bottom at a predetermined timing. The average value of the temperatures read from multiple locations in the axial direction is calculated, and this is the reference temperature T. This reference temperature T. and the temperature Ti (i=1.2...n) of each part in the axial direction of the raw pipe P read after that, and calculate the deviation ΔT1. After tasing to obtain the same diameter, calculate the deviation of each part in the axial direction of the amount of outer diameter contraction that is predicted to occur when cooled to room temperature, compensate for the deviation of each part, and create a uniform outer diameter in the cold state. In order to obtain VC, calculate the outer diameter of each part in the axial direction during hot operation. Next, in order to obtain a hot tube having the above-mentioned outer diameter on the exit side of the sizer L, in the sizing process of the raw tube P, the fourth and fifth stands 14 and 15 are set for each part in the axial direction. Calculate the roll gap J 1i" 21 of the caliber roll 24.25 and store it in sequence. These roll gaps δ1.δ are both axes relative to the reference temperature T determined for the blank tube P. It is desirable to set the coefficient 4i e K2i in advance for each temperature difference so that it can be determined as a value obtained by multiplying the temperature difference ΔTi of each part in the direction by the coefficient 1j and K2i.

Further, the arithmetic control unit 4 counts the pulses emitted from the pulse generator PG in the speedometer 3 to calculate the moving speed Vp of the raw tube P, and also calculates the moving speed Vp from the pre-inputted thermometer 2 installation position. Stand 4.5 14.
The part of the raw pipe P whose temperature was measured with the thermometer 2 based on the distance L□J L2 up to 15 is the 4.5th stand 1.
The delay times t1i and t2i until reaching 4.15 are calculated. Then, from the time when each temperature-measured portion of the raw tube P passes the thermometer 2, each temperature is 1. ．． Immediately before reaching the 4,511 21st stand 14.15 after 1 hour has elapsed, each pulse generator PG2. Based on the number of pulses emitted from PG3, the currently set Calibur Roll 24
．． 25 is calculated, the deviation between this roll gap and the newly calculated roll gaps δ□i, δ41 is determined, and a control signal is output to the rolling down motor 44, 45 in order to eliminate this roll gap deviation. There is. As a result, each part of the raw pipe in its axial direction is moved between caliber rolls 21 to 21 whose roll gaps are set according to the respective temperatures.
25 will be subjected to sizing.

Therefore, the outer diameter of the tube immediately after passing through the sizer varies depending on the temperature under hot conditions, but in cold conditions it becomes a tube with a uniform outer diameter over its entire length as a result of shrinkage.

Next, the results of a comparative test between the method of the present invention and the conventional method will be explained. The sample material has an outer diameter of 352m+++.

A raw pipe with a wall thickness of 9.4πm and a length of 12400M was used, and the roll gap was set and controlled for the fourth and fifth stands of the sizer in order to match the cold outer diameter target value of 339mm. The results are shown in Figures 2 (a) and (b).

Figure 2 (a) is a graph showing the comparative test results for the method of the present invention, and Figure 2 (b) is a graph showing the comparative test results for the conventional method. ) and the outer diameter (rtrm) is plotted on the vertical axis.

The solid lines in each graph indicate the cold outer diameter, and the broken lines indicate the hot outer diameter at the exit side of the sizer. As is clear from this graph, when the method of the present invention is used, the hot outer diameter gradually expands from approximately the middle toward the bottom, but the cold outer diameter is uniform over approximately the entire length. It has become. On the other hand, in the conventional method, the hot outer diameter is the same over the entire length, but the cold outer diameter is smaller at the bottom than at the middle.

In FIG. 1, the configuration in which roll gap control is performed in the fourth and fifth stands has been described, but it goes without saying that the control may be performed in all stands.

As described above, in the method of the present invention, the roll gap of the sizer is set and controlled according to the temperature of each part in the axial direction of the raw pipe, so it is possible to eliminate the influence of thermal contraction caused by temperature differences in the raw pipe, and to cool the pipe. The present invention has excellent effects, such as making the outer diameter uniform over the entire length, greatly improving pipe quality, and improving yield.

[Brief explanation of drawings]

FIG. 1 is a schematic side view showing the state of implementation of the method of the present invention, and FIGS. 2 (a) and (b) are graphs showing comparative test results. P...Main pipe 1...Sizer 2...Thermometer 3
...Speedometer 4...Calculation control unit 11-15...Stand 21-25...Caliber roll 31-35.
・・Down screw 41~45・・Down motor PG1
．． PG2. PG3...Pulse generator patent applicant Noboru Kono, patent attorney representing Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] 1. Measure the temperature of each part in the axial direction of the raw pipe at the entrance side of the sizer, and detect the temperature difference of each part in the axial direction with respect to the temperature at the tip of the raw pipe. 1. Adjust the roll gap of the sizer according to the temperature difference after cooling the pipe. A method for controlling the outer diameter of a seamless pipe, characterized by controlling settings so that the outer diameter of each part in the axial direction is uniform.