JPS6045962B2 - Wall thinning rolling method using pipe end thinning rolling equipment in seamless steel pipe manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal rolling method using a tube end thinning rolling device in seamless steel pipe manufacturing equipment.

The manufacturing process for seamless steel pipes consists of a drilling process in which a hole is made in a round steel piece, a stretching process in which the perforated hollow shell tube is stretched internally, and the stretched hollow shell tube is stretched to a specified outer diameter. It consists of three steps: squeezing and finish rolling.

That is, in the general manufacturing process of seamless steel pipes using a mandrel mill, for example, as shown in FIG. After being heated, it is pierced and rolled by a piercer mill 3 serving as a piercing rolling mill, and then elongated by a mandrel mill 5 serving as a stretching mill with a mandrel bar 4 inserted therein.

The hollow tube 6 stretched to double or quadruple length by the mandrel mill 5 is reheated in a reheating furnace 7 as necessary, and then transferred to a stretch reducer 8 as a finishing mill. It is then reduced and rolled to become a finished tube 9.
By the way, in the stretch reducer 8, the hollow blank tube 6 into which no mandrel bar is inserted is reduced and rolled by a large number of rows of roll stands with oval holes.
A finished tube 9 with a predetermined outer diameter and wall thickness can be formed. Here, the diameter of each roll hole shape in the continuous roll stand rows of the stretch reducer 8 is set so that the diameter becomes smaller toward the later stages, and the roll hole shape of the final roll stand is set outside the predetermined finished tube 9. The size corresponds to the diameter of the pipe 9, and thereby the outer surface of the finished tube 9 can be finished molded. Here, the wall thickness of the hollow tube 6 formed in the stretch reducer 8 becomes thicker as its outer diameter is reduced to a smaller diameter by the roll hole shape of each roll stand, and the wall thickness of the hollow tube 6 formed in the stretch reducer 8 becomes thicker as the outer diameter is reduced to a smaller diameter by the roll hole shape of each roll stand. As a result, the deformation of the tube at various circumferential portions becomes non-uniform, resulting in non-uniform wall thickness, resulting in the inconvenience that a finished pipe 9 of good quality cannot be obtained. In order to eliminate the above-mentioned disadvantages, in the conventional seamless steel pipe manufacturing process, when rolling the hollow shell tube 6 by the stretch reducer 8, the hollow shell tube 6 is rolled while applying a tensile force in the axial direction between each roll stand. The unevenness of the wall thickness in the cross section of the tube 6 is reduced, and at the same time, the tensile force is controlled by the roll rotation speed of each roll stand, thereby suppressing the increase in thickness or decreasing the thickness, and producing the finished tube 9 with a predetermined wall thickness.
It is possible to obtain.

However, even with the above-mentioned conventional seamless steel pipe manufacturing method, the tensile force between the roll stands is generated at both ends of the hollow pipe 6 from when it passes one roll until it is bitten by the next roll. cannot be given enough.

That is, it becomes impossible to remove the uneven thickness due to the increased thickness at both ends of the hollow tube 6, and it becomes necessary to cut off the increased thickness that occurs at both ends of the finished tube 9. The amount of cutting off of the thickened portion at both ends of the finished tube 9 varies greatly depending on the outside diameter reduction ratio in the stretch reducer 8 or the degree of control of the roll rotation speed in each roll stand. The ratio of the length with both ends cut off to the total length reaches about 5% on average. Therefore, in order to ensure that the wall thickness of the finished pipe obtained by the above-mentioned reduction rolling is uniform in the entire longitudinal direction, the present applicant has made the following efforts based on the specification and drawings attached to the application of Japanese Patent Application No. 56-74604. , 1. A core bar inserted into the inner periphery of the end of the hollow shell tube that has been perforated and stretched and rolled, and the core bar is brought into contact with the outer periphery of the end of the hollow shell tube into which the core bar is charged, while revolving and rotating. It also has a rolling roll for rolling down the end of the hollow shell, and reduces the wall thickness in advance by an increase in thickness that will be added to the end of the hollow shell by the reduction rolling that follows the elongation rolling. We have already proposed a thinning rolling method using a pipe end thinning rolling device in seamless steel pipe manufacturing equipment.

However, in the case of the thinning rolling method using the already proposed tube end thinning rolling device, as shown in FIGS. Although it is possible to roll the hollow shell 6 so that the thickness decreases toward the outer end, as shown in FIG. The outer diameter reduction ratio in the stretch reducer 8 becomes large, and as a result, a phenomenon of thickening occurs at the end of the hollow tube 6, and the effect of tube end thinning rolling is impaired.

The present invention provides a joint that suppresses the expansion of the outside diameter due to thinning rolling at the end of the hollow mother pipe and reliably makes the wall thickness of the finished pipe obtained by reduction rolling uniform in its entire longitudinal direction. It is an object of the present invention to provide a method for thinning rolling using a tube end thinning rolling device in a steelless pipe manufacturing facility.

In order to achieve the above object, the present invention provides a core metal inserted into the inner circumference of the end of a hollow tube that has been perforated and stretched and rolled;
a rolling roll that revolves and rotates in contact with the outer periphery of the end of the hollow shell into which the core metal is charged, and that rolls down the end of the hollow shell, and the rolling roll is provided after the elongation and rolling. A wall thinning rolling method using a tube end thinning rolling device in a seamless steel pipe manufacturing facility, which enables the wall thickness added to the end portion of the hollow shell tube to be thinned in advance by rolling. The amount of expansion of the outer diameter of the end due to wall rolling is predicted, and the wall thinning rolling is performed by providing a clearance between the inner diameter of the hollow blank tube before thinning rolling and the outer diameter of the core metal to offset the predicted tube expanding amount. There is something like that.

Hereinafter, the present invention will be explained in more detail with reference to the drawings.

FIG. 4 is a partially cutaway side view showing an example of a tube end thinning rolling apparatus used for carrying out the present invention, and FIG. 5 is a front view of FIG. 4.

The tube end thinning rolling device 12 shown in FIGS. 4 and 5 is placed between the mandrel mill 5 and the reheating furnace 7 in the general seamless steel pipe manufacturing process shown in FIG. 1. ,
The end portion of the hollow tube 6 that has been elongated and rolled by the mandrel mill 5 can be rolled to reduce its thickness.

That is, the tube end thinning rolling device 12 is in a state in which it revolves around and rotates around the core metal 13 charged into the inner circumference of the end of the hollow shell 6 and the outer circumference of the hollow shell 6 into which the core metal 13 is charged. It has three rolling rolls 14 that are in contact with each other and are capable of rolling down the hollow shell 6 toward the center, so that the ends of the hollow shell 6 become thinner as the outer ends in the axial direction It is possible to roll it to Each rolling roll 14 is rotatably supported by a chock portion 15A of each rolling device 15'' via a support shaft 14A, and is movable toward the center of the core bar 13 by a rolling mechanism of the rolling device 15, which will be described later. The lowering device 15 includes:
One end portion 1 of the revolving housing 18 is rotatably supported on the frame 16 via a bearing 17 coaxially with respect to the core metal 13.
8A, the hollow tubes 6 are arranged at three equal positions in the circumferential direction around the core metal 13, and the core metal 13 is inserted therein.
The respective rolling rolls 14 can be brought into contact with the outer circumference of the end portion of the roller 14 in a state of revolution and rotation. Furthermore, rolling roll 1
4 is set in a direction different from the center axes of the core metal 13 and the hollow shell 6, and when the rolling roll 14 contacts the outer periphery of the hollow shell 6 while rotating and rotating, the hollow shell A relative helical motion can be generated between the roll 6 and the rolling roll 14. A gear 19 is attached to the outer periphery of the end of the revolution housing 18 on the opposite side from the rolling down device 15, and the revolution housing 18 is rotationally driven by a revolution drive device 21 via a drive gear 20 that meshes with the gear 19. It is becoming more and more like this. Support shaft 14A of the rolling roll 14
A shaft of a gear 22 supported on the inner circumferential side of the revolving housing 18 is connected to an end of the rotary housing 18 via a universal joint 23 .
The gears 22 are arranged at three equal intervals on the inner circumference of the revolving housing 18 in correspondence with the rolling rolls 14, and each gear 22 meshes with a ring-shaped gear 24 disposed coaxially with the revolving housing 18 around the core metal 13. It is considered possible. gear 24
is integrally provided on the outer periphery of the cylindrical sleeve 25, and the sleeve 25 is coaxial with the core metal 13 and is movable relative to the core metal 13 in the axial and rotational direction via a bearing 26 on the outer periphery. Possibly supported. One end of the sleeve 25 protrudes outward from the end of the revolving housing 18 on the gear 19 side, and a ring-shaped gear 27 is attached to the outer periphery of this protrusion. A gear 29 attached to the output shaft of a rotation drive device 28 is meshed with the gear 27, whereby the sleeve 25 is rotationally driven around the core metal 13, and the gear 29 is attached to the output shaft of the rotation drive device 28.
4, 22 and each rolling roll 14 via a universal joint 23.
is now driven by rotation. The lowering device 15
The rolling roll 14 can be moved back and forth in the rolling direction by the rotation of a pinion 31 screwed into the rolling screw 30.

This pinion 31 is connected to one end 18 of the revolving housing 18.
It meshes with a rack 32 inserted through A from the axial direction, and is rotationally driven by the movement of this rack 32 in the axial direction. Three racks 32 are arranged corresponding to each rolling roll 14, and one axial end of each rack 32 is connected to the side surface of the ring 33. Both sides of the outer end of the ring 33 are sandwiched between a pair of rollers 36 rotatably attached to the ram 35 of the hydraulic device 34, whereby the ring 33 rotates together with the revolving housing 18. However, it can be driven in the axial direction. In addition, in the figure, 37 is a wheel that allows the frame 16 to move, 38 is a pinch roll that is able to pinch the hollow tube 6, 39 is a feed roller that is able to move the hollow tube 6 back and forth in the axial direction, and 40 is a wheel that allows the hollow tube 6 to be moved back and forth. A hydraulic device is provided that allows the core bar 13 to move forward and backward in its axial direction.

Next, an embodiment of the thinning rolling method according to the present invention using the tube end thinning rolling device 12 will be described.

First, as explained in FIG.
The pipe is carried into the processing center of the tube end thinning rolling device 12 for the rear end.

Here, the wheels 37 of the pedestal 16 are kept stationary, the core metal 13 and the rolling rolls 14 are each waited at a retracted position in the axial direction with respect to the hollow tube 6, and the radial position of each rolling roll 14 is (roll down position) is on standby at its retracted position. The rear end of the hollow tube 6 is the tube end thinning rolling device 1
When it is confirmed, for example, by a detection signal from an infrared detector, that the metal core 13 and the roll roll 14 have been loaded into the processing position No. is set to the lowered position. Here, when the core bar 13 is advanced and inserted into the hollow shell 6, the hollow shell 6 is fixedly held by the pinch rolls 38. At the same time as the setting of the rolling position of the rolling rolls 14 is completed as described above, the pinch rolls 38 release the hollow tube 6, the revolution drive device 21 and the autorotation drive device 28 are activated, and the rolling rolls 14 is brought into contact with the outer periphery of the end of the hollow tube 6 in a state where it revolves and rotates on its axis.

Here, since the rotation axis of the rolling roll 14 is arranged in different directions with respect to the central axes of the hollow shell 6 and the core metal 13, the rolling roll 14 and the hollow shell 6 move in a spiral manner relative to each other. . On the other hand, since the pedestal 16 is held stationary, the hollow tube 6 moves in its axial direction based on the spiral movement, and the rolling position by the rolling rolls 14 is gradually displaced toward its outer end. Therefore, the rolling roll 14
When the orbital rotation speed and the autorotation rotation speed of At the same time, twisting deformation occurs at the end of the hollow tube 6.

Therefore, in this embodiment, the revolution rotation speed and the autorotation rotation speed of the roll rolls 14 are mutually adjusted so that the roll rolls 14 do not apply rotational torque to the ends of the hollow shell tube 6. 6 can be moved in its axial direction without rotating it. As the hollow shell 6 moves in the axial direction without rotating as described above, the thickness decrease can offset the increase in thickness added to the end portion of the hollow shell 6 due to subsequent reduction rolling. The end portion of the hollow tube 6 is thinned at the same rate. The thickness reducing action by the rolling rolls 14 is carried out by the hydraulic device 34 via the rollers 36 on the ring 3.
3, thereby rotating the pinion 31 via the rack 32, thereby rolling down the rolling roll 14. Here, the core metal 13 is projected by the hydraulic device 40 so as not to move relative to the hollow shell 6, and thereby the rolling roll 4 is moved from the hollow shell 6.
While the core metal 13 is being rolled to reduce its thickness, the state in which the core metal 13 is inserted into the hollow tube 6 is maintained. Therefore, in this embodiment, when the core metal 13 and the rolling rolls 14 perform thinning rolling, the amount of expansion of the outer diameter of the end of the hollow shell 6 due to the thinning rolling is predicted, and the hollow tube before thinning rolling is In order to provide a clearance between the inner diameter of the blank tube 6 and the outer diameter of the core metal 13 to offset the predicted tube expansion amount, the inner diameter of the hollow tube 6 before thinning rolling is made by the predicted tube expansion amount. A core metal 13 with a small outer diameter is used.

Therefore, as shown in FIG. 6, in the hollow tube 6 that has been subjected to thinning rolling, the amount of tube expansion due to thinning is canceled out, and the outer diameters of the unrolled portion and the rolled portion by the rolling rolls 14 are approximately equal to each other. At the same time, the thickness is reduced toward the outer end in the axial direction. Note that the inner diameter of the rolling part by the rolling rolls 14 is
As shown in the figure, the inner diameter of the non-rolled part is smaller than that of the unrolled part, resulting in a step, but since the rolling is performed while applying tensile force through the subsequent reduction rolling by the stretch reducer 8, the step is finished. It does not remain in the tube. When the thinning rolling of the rear end of the hollow shell 6 is completed in this way, the rolling position of the rolling rolls 14 is opened, and the core metal 13 is opened.
is retracted by the hydraulic device 40 and pulled out from the hollow shell 6.

The hollow blank tube 6 whose thickness reduction rolling has been completed at the retreating portion is then carried into the processing center of the pipe end thinning rolling device for the front end portion, and the front end portion is subjected to thinning rolling in the same manner as the rear end portion. Ru. FIG. 7 is a diagram showing the relationship between the tube end wall thinning amount ΔT and the outer diameter expansion amount ΔD.

That is, Fig. 7 shows that a hollow tube with an outer diameter of 89.0 TIT, a wall thickness of 6.45 mm, and a length of 2500 mg is reduced by cylindrical rolling rolls at a rolling temperature of 950°C and a roll inclination angle of 6 degrees. Thickness T of the unrolled part by the rolling rolls when subjected to wall rolling. and the wall thickness T1 of the rolled part, that is, the amount of thinning ΔT, and the outer diameter D of the non-rolled part by the rolling rolls. This shows the relationship between the difference between the outer diameter D1 of the rolled portion and the tube expansion amount ΔD, and the relationship between the two is expressed by the exponential function of equation (1) below. The general relationship between the amount of wall thinning ΔT and the amount of pipe expansion ΔD is expressed by the exponential function of equation (2) below.

- In Equation (2), the coefficients K and n are predetermined based on the tube outer diameter, wall thickness, roll inclination angle, rolling temperature, rolling speed, tube material, roll shape, etc.

Therefore, depending on the rolling conditions, the amount of thinning ΔT and the amount of pipe expansion △
Determine the relationship D in advance, predict the amount of pipe expansion due to thinning rolling,
It becomes possible to set the clearance that should be provided between the inner diameter of the hollow shell and the outer diameter of the core metal. Below, the outer diameter is 88. h1
Wall thickness 6.45? A concrete implementation result will be described in the case where the end portion of the hollow blank tube is reduced in thickness by 1.2 Tmm. According to the above equation (1), when determining the outer diameter expansion amount ΔD for the thickness reduction amount ΔT=1.2TmIn, it becomes ΔD=12.5.

Therefore, the clearance that should be provided between the inner diameter of the hollow raw pipe before rolling and anything other than the core bar is 1, which is equivalent to the above-mentioned pipe expansion amount ΔD.
It is sufficient if it is 2.5w$t. Therefore, the outer diameter of the core metal 13 to be used is 63.5=. When this core metal 13 was used to perform thinning rolling, it became possible to make the outer diameters of the unrolled portion and the rolled portion of the hollow tube 6 substantially equal. The hollow shell tube 6 subjected to thinning rolling in this manner is rolled in a stretch reducer 8 to have an outer diameter of 50.8 mm and a wall thickness of 6.45 wrm.
Table 1 was obtained as a result of comparing the crop lengths at the leading and trailing ends when rolling into a finished tube with a total length of 1 and a length of 2 and a conventional method. According to Table 1, the crop truncation length is significantly reduced by implementing the present invention, and the yield is 1. It is recognized that it is possible to improve I%.

In the above embodiment, the hollow shell 6 is released by the pinch rolls 38 during thinning rolling by the rolling rolls 14. However, in the pipe end thinning rolling device 12, the hollow shell 6 may be fixed by the pinch rolls 38 and the frame 16 may be movable during thinning rolling by the rolling rolls 14. Also,
In the above embodiment, the present invention is applied to a tube end thinning rolling device 12 that uses rolling rolls 14 that are arranged in different directions with respect to the hollow tube 6 and move relative to each other in the axial direction of the hollow tube 6. I explained the case.

However, the present invention provides a pipe end thinning rolling device in which the rolling rolls are not arranged in opposite directions with respect to the hollow shell pipe, and is provided with other means for relatively moving the rolling rolls and the hollow shell pipe in the axial direction, or By using a rolling roll having a roll width equal to or greater than the length of the end of the hollow shell to be thinned, there is no need to move the rolling roll and the hollow shell relative to each other in the axial direction. It can also be applied to tube end wall thinning rolling equipment, etc. Furthermore, the present invention is not only applicable to a seamless steel pipe manufacturing process based on a mandrel mill method, but also to a seamless steel pipe manufacturing process using other rolling methods such as a plug mill method.

As described above, the present invention provides a core metal inserted into the inner periphery of the end of a hollow tube that has been perforated and stretched and rolled, and a core metal inserted into the outer periphery of the end of the hollow tube into which the core metal is inserted. Rolling rolls that revolve and rotate on their own axis and come into contact with each other and roll down the end of the hollow shell, the thickening added to the end of the hollow shell by the reduction rolling that follows the elongation rolling. A wall thinning rolling method using a tube end wall thinning rolling device in a seamless steel pipe production facility that enables the wall thickness to be reduced in advance, the method comprising: predicting the amount of expansion of the outer diameter of the end due to the wall thinning rolling; Since the wall thinning rolling is performed with a clearance between the inner diameter of the hollow shell tube and the outer diameter of the core metal to offset the above predicted tube expansion amount, it is possible to reduce the wall thickness at the end of the hollow shell tube. It becomes possible to suppress the accompanying expansion of the outer diameter of the tube and to ensure that the wall thickness of the finished tube obtained by reduction rolling is uniform in its entire longitudinal direction.

[Brief explanation of the drawing]

Figure 1 is a process diagram showing the manufacturing process of general seamless steel pipes.
Figure 2 is a front view showing the state of thinning of a hollow shell pipe by the pipe end thinning rolling device proposed by the present applicant [7];
The figure is a cross section taken along the line ■-■ in Figure 2, Figure 4 is a partially cutaway side view of an example of a tube end thinning rolling device used for carrying out the present invention, and Figure 5 is the same as Figure 4. 6 is a central vertical sectional view of a copper tube obtained by thinning rolling according to the present invention,
FIG. 7 is a diagram showing the relationship between the amount of pipe end wall thinning and the amount of outer diameter expansion. 3...Piercer mill, 5...Mandrel mill, 6.
...Hollow tube, 8...Stretch reducer, 12.
... Tube end thinning rolling device, 13... Core bar, 14... Rolling roll, 21... Drive device for revolution, 28... Drive device for rotation.

Claims (1)

[Claims] 1. A core bar inserted into the inner periphery of the end of the hollow shell tube that has been perforated and stretched and rolled, and the core bar is brought into contact with the outer periphery of the end of the hollow shell tube into which the core bar is charged, while revolving and rotating. , a rolling roll that rolls down the end of the hollow shell, and the wall thickness is reduced in advance by an increase in thickness that will be added to the end of the hollow shell by the reduction rolling that follows the elongation rolling. A thinning rolling method using a tube end thinning rolling device in a seamless steel pipe production facility, which predicts the amount of expansion of the outer diameter of the end due to the thinning rolling, and calculates the inner diameter of the hollow blank tube before thinning rolling. A thinning rolling method using a tube end thinning rolling device in a seamless steel pipe production facility, which performs thinning rolling by providing a clearance between the core metal outer diameter and the above predicted tube expansion amount to offset the above predicted tube expansion amount.