JPS59206105A - Manufacture of seamless pipe - Google Patents

Abstract

PURPOSE:To prevent the generation of an eccentric wall-thickness deviation and to obtain a high-quality seamless pipe by connecting swingably a plug to a mandrel bar and aligning the axial center line of the plug with that of a material to be rolled. CONSTITUTION:In the 1st piercer A, a billet B is moved by biting it between rolling rolls 1l, 1r, to pierce it into a hollow shell H by a plug 2. Next, in the 2nd piercer A', the shell H is spirally moved by the rolling rolls 1l, 1r, to expand it by a plug 2a. A connecting member 31a is formed at the tip of a mandrel bar 3a used for supporting the plug 2a, and the tip surface of member 31a is processed into a spherical convex surface 24. A connecting boss 32a to be loose fitted to a recessed connecting hole 25 of plug 2a is provided to the center of the surface 24, to make the plug 2a swingable with respect to the bar 3a. In this way, the axial center line of plug 2a follows up the pass-center of hollow shell H, to prevent the generation of an eccentric wall-thickness deviation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing seamless pipes, and more specifically, to an improvement in the so-called Mannesmann method for manufacturing seamless pipes using an inclined rolling mill.

To manufacture seamless steel pipes using the Mannesmann plug mill method, first, a billet is heated to the required temperature in a heating furnace, passed through a piercer, a hole is drilled in the center of the billet, and a hollow shell is obtained. After passing the hollow shell through a second piercer (elongator) and processing it for diameter expansion and thinning, the hollow shell is stretched and rolled in a plug mill and reeled.

The sizer polishes the pipe, corrects its shape, and sizes it, and the refining process measures the diameter of the seamless steel pipe.

However, in the method of manufacturing seamless steel pipes using the Mannesmann plug mill method as described above, there is a problem in that uneven thickness occurs, which is unique to this method, and the quality of the seamless tube deteriorates. The form of uneven thickness can be roughly divided into the following two types.

+11 Eccentric thickness deviation in a piercer (2) Symmetrical thickness deviation in a plug mill In particular, eccentric thickness deviation that occurs in a piercer is a plug mill.

Although the thickness unevenness can be gradually reduced using rolling mills such as reelers and sizers, it is impossible to completely eliminate the thickness, as it remains in the final product and deteriorates its quality.
In terms of the quality of seamless steel pipes, it is important to prevent the occurrence of eccentric thickness unevenness.

It has been known that the cause of this eccentric thickness is due to uneven heat of the billet, and other factors have not been elucidated.

Therefore, the inventors of the present invention conducted experiments and research into the causes of eccentric thickness unevenness in the pier, and found that in addition to being caused by the above-mentioned uneven heat, uneven thickness also occurs due to core runout of the plug during drilling or diameter expansion. I found out that.

The present invention was made based on such knowledge, and its purpose is to enable the axial center of the plug to follow the axial center of the material to be rolled, thereby preventing the occurrence of eccentric thickness deviation due to core runout of the plug. To provide a method for manufacturing a seamless pipe that prevents deterioration of the quality of the seamless pipe.

The present invention provides a method for manufacturing a seamless pipe, in which a material to be rolled is spirally moved in the axial direction using an inclined rolling mill, and
A method for manufacturing a seamless pipe in which a material to be rolled is perforated or rolled by penetrating a plug connected to a mandrel bar,
The plug is characterized in that it is swingably connected to a mandrel bar so that its axial center line coincides with the axial center line of the material to be rolled.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to drawings showing an embodiment in which a second piercer uses a plug that characterizes the method of the present invention. FIG. 1 is a schematic plan view showing a state in which a billet is being perforated using a first viaser, and this perforation process itself is exactly the same as the conventional method. That is, the billet B, which is the material that has been heated to a required degree of roughness in a heating furnace (not shown), is passed through a first viaser. The first pierzer A includes a gorge portion 11 having a maximum diameter in the middle in the axial direction,
On both sides of this gorge portion 11, an inlet surface 12 and an outlet surface 13 are formed, each having a truncated conical shape whose diameter gradually decreases toward the terminal side.
A pair of rolling rolls 1ρ, lr equipped with
, followed by a reeling part 22 forming a substantially circular &(r trapezoid) and a plug 2 having a relief part 23 whose diameter decreases toward the base end, and both rolling rolls 17!

1r is placed on both sides of the pass center of billet B so that both axes are parallel in plan view, and in side view ゛ζ, one entrance surface 12 faces the - side with respect to the pass center, and the other one faces downward. They are arranged so as to face each other at a required angle.

On the other hand, the plug 2 is arranged with its axial center line aligned with the pass center, and its base end face perpendicular to the axial line is aligned with the mandrel bar.
The mandrel bar 3 is connected to the tip end surface perpendicular to the axial line of the mandrel bar 3, and rotates integrally with the mandrel bar 3 about the axial line. The mandrel bar 3 is for supporting the plug 2, and its proximal end is connected to a thrust block 4 to enable rotation of the mandrel bar 3 and to support the thrust force received by the plug 2. ing.

There is a mandrel bar between plug 2 and thrust bronchus 4.
A plurality of bar tie ears 5 are arranged to suppress the deflection of the bar tie 3.

In the first piercer A configured in this way, billet B
is transferred in the axial direction as shown in the direction of the white arrow in the figure, is caught between the inlet surfaces 12 and 12 of both rolling rolls 1β and lr, and is rotated in the axial direction while being rotated along the axial line surface. A hole is formed by the action of the plug 2, which is moved in a so-called spiral movement and prevented from moving in the axial direction by the thrust block 4, thereby forming a hollow shell H.

Next, the diameter expansion by the second piercer A', which is a post process, will be explained. FIG. 2 is a schematic plan view of the plug and its surroundings showing a state in which the diameter is expanded using the second via No. 8'. Note that the same parts as in the first piercer A are given the same numbers.

This second piercer A' is installed in the direction of movement of the hollow shell H toward the first piercer, and the hollow shell H that has been perforated by the first piercer A is transferred thereto.

The hollow shell Ha is spirally moved by two rolls IC1r similar to the two rolls IA and lr used in the first piercer A, and its diameter is expanded by the plug 2a.

The plug 2a, which is the main part of the method of the present invention, has each part increased in diameter compared to the plug 2 used in the first piercer A in order to ensure the required amount of diameter expansion, and its axial dimension is the same as required. As a whole, the plug 2 is formed into a warhead shape like the plug 2.

The proximal end surface of the plug 2a is formed perpendicular to the axis of the plug 2a, and a suitable concave connecting hole 25 is formed in the center thereof toward the distal end side of the plug 2a.

The distal end of the mandrel bar 3a, whose proximal end is connected to a thrust block (not shown), is composed of a solid connecting member 3]a fitted into a tube body, and its distal end surface is spherical. The plug 2 is machined into a convex surface 24 in the center of the convex surface 24.
A connecting boss 32a is provided which is loosely fitted into the concave connecting hole 25 of a, and when the connecting host 32a is loosely fitted into the connecting hole 25 and the plug 2a and the mandrel bar 3a are connected, the plug 2a is fitted into the connecting boss 32a. It is possible to swing relative to the mandrel bar 3a within the clearance between the mandrel bar 3a and the connecting hole 25.

When diameter expansion and rolling are performed using such a second piercer, an axial thrust force acting on the mandrel bar 3a through the plug 2a due to the spiral movement of the hollow shell H causes the mandrel bar 3a to move as shown in FIG. Even if the plug 2a is deflected, the plug 2a can be swung within the above clearance range, and regardless of the deflection of the mandrel bar 3a, it is possible to align its axis with the basis center of the borrow shell H, allowing for diameter expansion. , core runout does not occur during rolling, and as a result, eccentric thickness unevenness can be prevented from occurring. In other words, in the conventional plug support structure in which the back surface of the plug 2b and the end surface of the connecting member 3 of the mandrel bar 3b abut on a plane perpendicular to the axis of both, as shown in FIG. The axial center line of the mandrel bar 3b moves so that its axial center line coincides with the axial center line of the mandrel bar 3b, which causes the center runout of the plug 2b. The axis line of 2a follows the bus center of the borrow shell (2), thereby preventing the occurrence of eccentric thickness.

The borrow shell (1) whose diameter has been expanded in this manner is passed through a plug mill, a reeler, and a size to form a finished product.

In addition, in the above-mentioned embodiment, the plug 2a has a connecting structure that allows the plug 2a to swing with respect to the mandrel bar 3a.
The base end surface of the connecting member 31a is a plane perpendicular to the axis thereof, and the connecting member 31a
Although the case where the distal end surface of the spherical convex surface 24 is connected is shown, it is of course possible to have a structure in which this is provided in reverse and connected, and the case where the second piercer is used is described. However, when the diameter expansion process is not required, the first piercer may have a swingable support structure as described above; 2nd piercer
Needless to say, the structure may be used in conjunction with a plug mill.

As detailed above, the method for manufacturing a seamless pipe according to the present invention includes:
The present invention has excellent effects, such as being able to prevent core runout of the plug during drilling, diameter expansion, and elongation rolling, and improving the quality of seamless pipes without causing eccentric thickness deviations.

The method of the present invention is not limited to the above-mentioned Mannesmann plug mill system, but can also be applied to other methods using an inclined rolling mill, such as the Mannesmann mandrel mill system.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIG.
A schematic plan view showing a state in which a billet is being perforated using a piercer, FIG. 2 is a schematic plan view around the plug showing a state in which the diameter is expanded using a second piercer, and FIG. FIG. 4 is a schematic diagram showing the effects of the present invention, and is a schematic diagram showing a gangway for connecting a mandrel bar and a plug according to a conventional method. IA, lr - rolling roll 2.2a, 2b... plug 3.3a, 3b... mandrel bar 11... gorge part 12... inlet surface 13... exit surface 24...
Convex surface 25...Concave connecting hole 31a...Connecting member
32a...Connection boss A...First piercer-A'...
・Second piercer B...Viresol l-H...Hollow shell patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono Procedural amendment W (voluntary) August 7, 1982 Patent Application No. 82267 2, Title of Invention 1''-1 Tubeless Manufacturing Method 3, Relation to Amendment Person Case J- Address of Patent Applicant 5-15 Kitahama, Higashi-ku, Osaka Name (2)
11) Sumitomo Metal Industries Co., Ltd. Representative Norifumi Kumagai 4, Agent address: 207 Nisshin Building, 1-14-22 Shitennoji, Tennoji-ku, Osaka 543. "Detailed Description of the Invention" and "Brief Description of Drawings" columns of the specification, as well as Drawing 6, Contents of Amendment 6-11 "Detailed Description of the Invention" column (1) Page 3, line 2 of the specification [Correct the word ``Pier J'' to ``Piercer.'' (2) “When using Braguwo” on page 4, line 2 of the specification.
Correct the statement to read, "When using a plug." (3) On page 5, line 12 of the specification, the phrase [Thrust Block 4] is corrected to read "Thrust Block 4." (4) On page 6, line 5 of the specification, the phrase "around the plug" should be corrected to "around the plug." (5) “Vasis Center” on page 8, line 2 of statement 11
Correct the statement to "Bus Center". (6) "Size" on page 8, line 16 of the specification,
"Sipe", I corrected. (7) In the second and third lines of page 9 of the specification, the words "Of course," have been corrected to "Of course," and the revised 1, Of course. ” and then add the following sentence: [Also, the connecting portion between the plug and the mandrel bar may have a connecting structure as shown in FIG. 5. That is, the plug 2c has a saucer-shaped connecting hole 25c provided in the center of its base end surface, and its distal end surface is processed into a spherical concave surface 25d. The distal end of one mandrel bar 30 is composed of a connecting member 3]c fitted into the tube body, and the connecting member 31c extends from the center of the circular base on the proximal end toward the distal end. The cylindrical body part protrudes, and its tip is formed into a spherical surface 3]d, and by spherically supporting the concave surface 25d of the plug 2C on the spherical surface 31d, the plug 2c can swing relative to the mandrel bar 30. Supported. And, in the ``6-21 Brief Description of Drawings'' column fil, on page 10, line 2 of the specification, the phrase ``around the plug'' is corrected to ``around the plug''. (2) On page 10, line 5 of the specification, the phrase ``This is a schematic diagram showing a mode of connection.'' has been replaced with ``A schematic diagram showing a mode of continuity.
FIG. 5 is a partially cutaway plan view of the mandrel bar and plug connection used in carrying out the method of the present invention. ” he corrected. (3) At the end of page 10, line 13 of the specification, “2c.
... Plug 3c ... Mandrel bar 25c ... Connection hole 25d ... Concave surface 31c ... Connection member 31d
...spherical surface" is added. 6-3 Add Figure 5 shown in the attached drawing sheet. 7. List of attached documents (1) 1 additional drawing

Claims (1)

[Claims] 1.1 A seamless pipe in which a plug connected to a mandrel bar is inserted into the center of a material to be rolled while the material is spirally moved in the axial direction in an oblique rolling mill to perforate or roll the material to be rolled. A method for manufacturing a seamless pipe, characterized in that the plug is swingably connected to a mandrel bar so that its axial center line coincides with the axial center line of the material to be rolled.