JPS60111703A - Manufacture of seamless pipe - Google Patents

Abstract

PURPOSE:To eliminate the generation of eccentric wall-thickness deviation and to obtain a seamless pipe free from quality deterioration by fixing a mandrel bar unrotatably and holding a plug freely rotatably at the front end of mandrel bar. CONSTITUTION:In manufacturing a seamless pipe by Mannesmann system, a mandrel bar 3 is fixed unmovably in the axial direction and unrotatably by a thrust block 4 and a bar steadier 5. A plug 2 is fitted to the front end of a plug holding piece 39 held rotatably around the axis of mandrel bar 3 at the front of the bar 3, and is rotated, together with the piece 39, around the axis of bar 3. In this way, the generation of eccentric wall-thickness deviation caused by the eccentric rotation of mandrel bar 3 is prevented, and a high quality seamless pipe is manufactured.

Description

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

[Prior art]

The method for manufacturing seamless steel pipes using the so-called Mannesmann method is as follows:
First, the billet, which has been heated to the required temperature in a heating furnace, is passed through a piercer and a hole is pierced at its center to obtain a hollow shell.If necessary, the hollow shell is passed through a second piercer (
After reaching the elongator) and undergoing treatment to expand the diameter and thin the wall, the borrow shell is stretched and rolled using a stretching mill such as a plug mill or mandrel mill, and polished using a reeler and sipe.

Shape correction and sizing are performed, and a seamless pipe is obtained through a refining process.

By the way, in the method of manufacturing a seamless pipe using the Mannesmann method as described above, the mandrel bar is bent by the axial thrust force applied through the plug due to the spiral movement of the billet or hollow shell. In the conventional method of manufacturing seamless steel pipes, the mandrel bar was rotated together with the plug, so this deflection causes the mandrel bar to rotate eccentrically, and the plug accordingly rotates eccentrically. Therefore, the axis of the plug and the pass center of the billet or hollow shell are misaligned, resulting in eccentricity and uneven thickness. Although the eccentric thickness unevenness that occurs with such a punching machine can be gradually reduced by using various rolling mills such as plug mills, reelers, and + isers, it is impossible to completely eliminate it, and it is impossible to completely eliminate it. It is important to prevent eccentric thickness unevenness from occurring in terms of the quality of seamless steel pipes, since they remain and deteriorate their quality.

〔the purpose〕

The present invention has been made in view of the above circumstances, and the mandrel bar, which rotatably supports the plug, is fixed to the tip of the mandrel bar in a non-rotatable manner. To provide a manufacturing method that eliminates the generation of meat and does not deteriorate the quality of seamless pipes.

[Structure of the invention]

The method for manufacturing a seamless pipe according to the present invention involves moving the material to be rolled in the axial direction using inclined rolling rolls, and inserting and setting a plug connected to a mandrel bar into the center of the material to be rolled. In the method of manufacturing a seamless pipe, the plug is connected to the tip of a mandrel bar, which is fixed in a non-rotatable manner, so as to be rotatable about its axis.

That is, as schematically shown in FIG. 1, the mandrel bar 2 3 is fixed by the thrust block 4 and bar tie ear 5 so that it cannot move or rotate in the axial direction, and the plug 2 is fixed at the tip of the mandrel bar 3 &Ml. The eccentric rotation of the mandrel bar 3 is achieved by fitting the tip of a plug holder 39 supported rotatably around its axis by the plug holder 39 and rotating the plug holder 39 together with the holder 39 around the axis of the mandrel bar 3. It is also intended to prevent the occurrence of eccentric thickness unevenness caused by this.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on drawings showing embodiments thereof. FIG. 2 is a schematic plan view showing the case where the method of the present invention is applied to a second piercer, and FIG. 3 is a plan sectional view of the vicinity of the plug.

The round billet is passed through a first piercer (not shown) to form a hollow shell H, and this hollow shell H is passed through a second piercer A for diameter expansion and thinning treatment. The second piercer A is provided with a gorge portion 11 having a maximum diameter in the middle in the longitudinal direction of the shaft, and on both sides of the gorge portion 11, entrance surfaces 12, each having a truncated conical shape, the diameter of which gradually decreases toward the terminal side. A pair of rolling rolls IC1r equipped with an exit surface 13, and a rolling section 2 which has a warhead shape as a whole and has a substantially truncated conical shape from the tip side.
1. It is constructed by combining a reeling part 22 which follows the reeling part 22 in the shape of a substantially truncated cone and a plug 2 having a relief part 23 whose diameter decreases toward the base end, and the re-rolling roll 17! , lr are placed on both sides of the bus center of billet B so that both axes are parallel in plan view, and one entrance surface 12 faces upward and the other faces downward with respect to the bus center in side view. They are arranged so as to be inclined at a required angle.

On the other hand, the plug 2 is arranged with its axial line aligned with the bus center, and its base end surface is formed perpendicular to the axial line of the plug 2. A proper connecting hole 2a is formed whose diameter decreases toward the tip side.

The main body 31 of the mandrel bar 3 has a tubular shape, and its proximal end is connected to the thrust block 4 to support the thrust force received from the hollow shell H via the plug 2. A bar tape ear is provided in the middle. A plurality of mandrel bars 5 are provided to prevent bending and rotation of the mandrel bar 3. This prevents the mandrel bar 3 from moving and rotating in its axial direction.

The inner diameter of the distal end of the main body 31 is larger than that of the proximal end, and a female thread 31a is carved on the inner periphery.

At the distal end of the main body 31, there is a stepped cylindrical plug support support member 32, which has the same diameter as the outer diameter of the main body 31 and has a slightly smaller diameter on the proximal end. A male screw 32a carved in the main body 31 is screwed into the female screw 31a, and the boundary step is brought into contact with the distal end surface of the main body 31 to connect the main body 31.

A plug holder 39 is rotatably fitted into this support member 32, and a truncated conical connecting portion 3 at the tip of the holder 39
9b is fitted into the connecting hole 2a, and the plug 2 and the receiver 39 are connected to the main body 31. It is adapted to rotate relative to the support member 32.

The inner surface of the portion of the support member 32 extending approximately A along its entire length from the distal end side is a bearing fitting portion 32b formed to have a larger diameter than the inner surface of the central portion 32f. A thrust self-aligning roller bearing 36 is fitted concentrically to the portion. Also, approximately 1/1/2 of the total length from the base end side of the support member 32
The inner surface of the portion extending over the center portion 32f is a bearing fitting portion 32c formed to have a slightly larger diameter than the inner surface of the central portion 32f, and a conical roller bearing 35 is concentrically arranged in the deep inner part of the bearing fitting portion 32c. It is fitted.

The diameters of the inner and outer rings of the bearing 35 are selected to be smaller than the diameters of the inner and eight outer rings of the bearing 36.

The receiver 39 includes the connecting portion 39b and the main body 31 after the connecting portion 39b. A flange portion 39 having the same diameter as the outer diameter of the support member 32
a, and further has a shaft portion 39c on the rear side having an outer diameter reduced in three steps and an inner diameter reduced in two steps. The bearing 36 is fitted onto the medium diameter shaft portion 39d, and the bearing 36 is fitted onto the medium diameter shaft portion 39d.
The side surface of the inner ring is in contact with the step between e and e. The bearing 35 is externally fitted onto the small-diameter shaft portion 39F, and the outer ring side surface is in contact with the step between the center portion 32f of the support member 32 and the bearing fitting portion 32c, and the outer ring is in contact with the base end of the small-diameter shaft portion 39f. A spacer 40 that is fitted and positioned by a NAND member 41 is brought into contact with the side surface of the inner ring. The length of the shaft portion 39c is selected to be slightly shorter than the length of the support member 32. Support member 32. A lubricating oil injection hole 39 is formed in the space 50 between the fitting parts of the shaft portion 39c so as to reach the space 5° from the outer peripheral surface of the support member 32.
Grease 51 (or oil) is filled from g to lubricate both bearings 35 and 36. Note that the inner diameter of the substantially central portion of the central portion 32f of the support member 32 and the shaft portion 3
The outer diameter of the central portion of 9c is gradually reduced toward the tip to facilitate the flow of grease 51 (or oil).

Further, the injection hole 39g is closed with a screw 39h after being filled with the grease 51.

An oil seal 38, 38 is provided between the bearing fitting portion 32b of the support member 32 and the large diameter shaft portion 39e of the shaft portion 39c.
Oil seals 34, 34 are interposed between the bearing fitting portion 32c of the support member 32 and the spacer 4o.

The shaft portion 39c of the receiver 39 has a cooling water flow hole 44, and the tip of the shaft portion 39c in contact with the flange portion 39a has a plurality of cooling water holes (only shown in the drawing) in the radial direction. A water discharge hole 44a is provided. Flange portion 39a
A slight gap is formed between the proximal side surface of the support member 32 and the distal side surface of the support member 32.
This is to prevent rotation of the receiver 39 from being hindered even if elastic deformation occurs in the receiver 39 due to a bending moment or the like applied to the receiver 32 via the support member 32.

The proximal opening of the support member 32 is sealed with a cover 47, and the cooling water supply pipe 42 is inserted and fixed in the center of the cover 47. The base end side of the supply pipe 42 is connected to a cooling water supply source (not shown), and cooling water from the cooling water supply source flows through the supply pipe 42 and the hole 44 to reach the flange portion 39.
a is cooled and discharged to the outside from the discharge hole 44a. In addition,
An O-ring 46 is fitted into the inner circumferential surface of the toilet seat 49 provided at the center of the cover 47 in order to prevent the cooling water flowing through the hole 44 of the cooling water supply pipe 42 from entering the main body 31. Also, a seal 48 is fitted in contact with the toilet seat 49.

With the above structure, in the present invention, the mandrel bar 3 is fixed so that it cannot move in the axial direction or rotate around the axis, and the support member has the plug 2 screwed onto the tip of the mandrel bar 3. The mandrel bar 3 rotates together with the support 39 which is rotatably supported by bearings 35 and 36 fitted inside the mandrel bar 3. Also, since the bearing 36 is a thrust self-aligning roller bearing, the mandrel bar 3 Even if deflection occurs at the tip, the axial center line of the plug 2 can be held constant due to the alignment action of the bearing 36, and the eccentric rotation of the plug 2 will not cause core runout. It becomes possible to align the axis line with the path center of the hollow shell H. The borrow shell H whose diameter has been expanded in this manner is passed through a plug mill, a reeler, and a sipe to form a finished product.

In addition, although the above-mentioned example described the case where the method of the present invention is applied to the second piercer, it is of course applicable to the first piercer as well, and can also be applied to other rolling machines such as a reeler. Of course.

〔effect〕

As detailed above, the seamless pipe molding method according to the present invention includes:
It is possible to prevent core runout of the plug during drilling, diameter expansion, and stretching and rolling, and it is possible to improve the quality of seamless pipes without causing eccentric thickness deviations, and
Since the mandrel bar does not rotate, the mandrel bar rotation receiving portion of the thrust block becomes unnecessary and the structure can be simplified, and the present invention has excellent effects.

[Brief explanation of drawings]

The drawings show embodiments of the present invention, and FIG. 1 is an explanatory diagram of the principle of the present invention, FIG. 2 is a schematic plan view showing the implementation state of the method of the present invention, and FIG. 3 is a planar cross-section around the plug. It is a diagram. ljj, lr...Roll roll 2...Plug 3.
... Mandrel bar 32 ... Support member 39 ... Receiver H ... Hollow shell patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono

Claims (1)

[Scope of Claims] 1. A joint in which a plug connected to a mandrel bar is inserted into the center of the material to be rolled to make a hole in the material while the material to be rolled is spirally moved in the axial direction by an inclined rolling roll. A method for manufacturing a seamless pipe, characterized in that the plug is connected to the tip of a mandrel bar which is fixed in a non-rotatable manner so as to be rotatable about its axis. Method.