JP3085256B2 - Manufacturing method of seamless pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a seamless pipe by piercing and rolling a solid billet.

[0002]

2. Description of the Related Art As a method of manufacturing a seamless pipe, a Mannesmann pipe manufacturing method as shown in FIGS. In this method, first,
A round bar piece (solid billet) 1 is heated to a predetermined temperature in a rotary hearth heating furnace A, and is pierced by a piercing mill B to form a hollow shell 2. Since this hollow shell 2 is short and thick, it is continuously rolled by a roll 4 in a state where a mandrel bar is inserted into the pipe by a drawing rolling machine C such as a plug mill or a mandrel mill, and mainly has a wall thickness. And the length is extended to form the hollow shell 5. During this rolling, the temperature of the hollow shell 5 decreases, so that the hollow shell 5 is reheated in the reheating furnace D, and is drawn by a rolling mill (stretch reducer).
E reduces the outer diameter and finishes it into a seamless pipe of the specified dimensions.

[0003] The piercing mill B used in this method includes:
A piercing rolling method using a barrel-shaped or cone-shaped inclined rolling roll is adopted, and usually, two inclined rolling rolls 11 and 21 are used.
And a plug 14 to be inserted into the solid billet 1 and an outer surface regulating tool.

FIG. 5 is a Japanese Patent Application Laid-Open No. 63-238909 (Japanese Patent No. 1812).
No. 697) is a front view of a piercing mill using a guide shoe, FIG. 6 is a partially cutaway plan view as viewed from the direction I in FIG. 5, and FIG. 7 is a view as viewed from the direction II in FIG. FIG. Each of the inclined rolling rolls 11 and 21 has gorge portions 11g and 21g at an intermediate portion in the axial direction thereof, and a frusto-conical roll surface 11a whose diameter is gradually reduced from one side to one side in the axial direction. , 21a are formed, and on the other side, frustoconical roll surfaces 11b, 21b whose diameters are more gradually increased are formed.

The roll shafts 11c, 21 of the inclined rolling rolls 11, 21
c is the pass line X- of the solid billet 1 to be rolled.
As for X, it is installed so as to be crossed at a crossing angle γ in a plan view, and to cross at a middle angle (roll surfaces 11b, 21b) at a slant angle β in a side view. In this case the roll surface 11a, 21a and the pass line X-X and forms an inlet face angle alpha ₁ and the roll surface 11b, also the outlet face angle alpha ₂ formed by the 21b and the pass line X-X has been determined properly.

A plug 14 having a bullet-shaped tip and a base supported by a mandrel 15 is connected to the other side of the inclined rolling rolls 11 (roll surfaces 11b, 21b) along a pass line XX.
Side) from the gorge part 11g, 21g slightly roll surface 11a, 21
It is arranged so that it protrudes to the position on the a side. Guide shoes 12, 22 above and below the pass line XX (Fig. 5)
Are arranged at positions substantially intermediate between the inclined rolling rolls 11 and 21, respectively.

The inclined rolling rolls 11 and 21 are driven to rotate at the same angular speed in the directions indicated by arrows by drive units (not shown), and the solid billet 1 is moved from one side of the inclined rolling rolls 11 and 21 to the other side by a pass line. The screw is moved along XX.
Then, the guide shoes 12 and 22 are rolled into contact with the outer peripheral surface of the solid billet 1 which is screw-moved, thereby performing piercing and rolling while restricting the outward bulging, and the hollow piece 2 is obtained.

Such a piercing and rolling technique fundamentally denies the principle of piercing of the Mannesmann piercing method, and the conventional Mannesmann piercing method is a technique for piercing using a so-called rotary forging effect (Mannesmann effect). On the other hand, the rotation forging effect from when the solid billet 1 is bitten by the inclined rolling rolls 11 and 21 to when it reaches the plug 14 is suppressed as much as possible. The aim is to minimize the occurrence of additional shearing deformation, and to achieve a metal flow equivalent to or equivalent to the extrusion tube method.

This is for the following reasons. That is, the rotary forging effect is the main cause of the generation of internal flaws when a difficult-to-work material is pierced, and the additional shear deformation is a factor of propagation of internal flaws (Japanese Patent No. 1812697: JP-A-63-238909).
issue). Therefore, Japanese Patent Application Laid-Open No. 63-238909 discloses stainless steel, high-alloy steel and other difficult-to-machine materials as inner surface flaws,
The inclination angle β and the crossing angle γ are held in the range of 8 ° ≦ β ≦ 20 ° (1) 5 ° ≦ γ ≦ 35 ° (2) 15 ° ≦ β + γ ≦ 50 ° (3) The relationship as expressed by equation (4) is established between the diameter d _{0 of the} billet 1, the outer diameter d of the hollow piece 2 after piercing, and the thickness t of the hollow piece 2, and the piercing ratio (length of hollow piece / length) Length of solid billet = d
₀ ² / 4t (dt)) to 4.0 or more, or the expansion ratio (d / t)
d ₀ ) is 1.15 or more, or the thickness / outer diameter ratio (t / d) is 6.5.
% Is disclosed.

[0010]

(Equation 1)

This publication also discloses a configuration in which the entry end faces of the roll shafts 11c and 21c of the inclined rolling rolls 11 and 21 do not collide with the solid billet 1 when the crossing angle γ is increased. In the normal inclined roll 11 (21), supporting and driving of the inclined roll 11 (21) are realized by attaching the roll shafts 11c (21c) protruding on the entrance side and the exit side to the frames 16 and 17. doing. However, in the piercing rolling mill disclosed in this publication, as shown in FIG. 8, a concave portion 11d is provided at the tip of one side (roll surface 11a side) of the inclined rolling roll 11, and the concave portion 11d is provided with a support frame on the entry side. The roll shaft 11c to be attached to 16 is substantially immersed. As a result, even when the crossing angle γ of the inclined roll 11 (21) is increased, the solid billet 1 can be supported by the frame 16 without colliding with the entry-side end face of the roll shaft 11 c (21 c).

[0012]

By performing piercing and rolling under the above-described conditions, the problem of inner surface flaws can be substantially solved, but the problem of wear of the plug 14 remains as an unsolved problem. The deformation resistance of stainless steel is about twice that of carbon steel, and the deformation resistance of high alloy steel (for example, 30Cr-40Ni-3Mo) is about four times that of carbon steel. In this case, countermeasures against plug life are important issues. Also, in the drilling of carbon steel, extension of the plug life is desirable from the viewpoint of running cost reduction.

The present invention has been made in view of such circumstances, and the cross angle γ of the inclined rolls is set to 0 ° ≦ γ <5 °.
An object of the present invention is to provide a method for manufacturing a seamless pipe that can extend the life of a perforated plug by setting the expansion ratio to 1.15 or more.

It is another object of the present invention to provide a method of manufacturing a seamless tube that can extend the life of a pierced plug by using a pierced plug larger than the diameter of a metal round bar piece.

[0015]

SUMMARY OF THE INVENTION There are two types of wear of a plug. One is wear of a plug tip and the other is rough surface of a plug body. The present inventors have conducted various studies on the plug material and the drilling setup, including the development of a plug made of a different material (for example, a plug whose tip is made of a heat-resistant material). It was concluded that the perforation method itself was the most effective.

In the method for manufacturing a seamless pipe according to the present invention, a perforated plug is inserted into the metal round bar piece in the longitudinal direction while rolling the metal round bar piece with the opposed inclined rolling roll. In the method of obtaining a hollow shell and manufacturing a seamless pipe, the crossing angle γ of the inclined rolling rolls is set to 0 ° ≦ γ <5 °,
The expansion ratio is set to 1.15 or more.

According to a second aspect of the present invention, there is provided a method of manufacturing a seamless pipe, wherein a pierced plug is inserted into the metal round bar piece in the longitudinal direction thereof while rolling the metal round bar piece with the opposed inclined rolling roll. In the method for producing a hollow shell by using a perforated plug having a diameter larger than that of the metal round bar, the crossing angle γ of the inclined rolling roll is set to 0 ° ≦ γ <5 °. It is characterized by the following.

In order to increase the expansion ratio by using perforated plugs having the same diameter in order to obtain a hollow shell having the same diameter, a metal round bar piece having a small diameter is used. Then, the heat capacity ratio of the perforated plug to the metal round bar piece becomes relatively large, so that the temperature of the perforated plug does not easily rise even if it comes into contact with the metal round bar piece heated to a predetermined temperature. Therefore, the softening of the perforated plug is reduced, and the wear of the plug, including the wear of the tip and the rough skin of the body, is suppressed, and the life can be extended. Conversely, the diameter of the metal round bar pieces is the same,
The same is true when a perforated plug with a large diameter is used. That is, the relative heat capacity ratio of the perforated plug to the metal round bar piece is larger than that in the case where the one having a relatively small diameter is used, and the same effect as in the case described above can be obtained.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. The method for producing a seamless pipe according to the present invention relates to a piercing and rolling step using inclined rolling rolls, and can be carried out in a conventional piercing and rolling mill as shown in FIGS. While rolling the round slab 1 with the inclined rolling rolls 11 and 21 provided across the pass line of the round slab 1 made of a material such as stainless steel, high alloy steel, or carbon steel, the round slab 1 The hollow plug 2 is obtained by inserting a piercing plug 14 in the longitudinal direction into the hollow tube 2 to manufacture a seamless tube. Here, the crossing angle γ of the inclined roll is set to 0 ° ≦
γ <5 ° and the expansion ratio is 1.15 or more. Preferably, a perforated plug having a diameter larger than the round slab 1 is used.

As a result, it is possible to increase the relative heat capacity ratio of the perforated plug, suppress the wear of the plug including the wear of the tip and the rough surface of the body, and extend the life.

[0021]

【Example】

Embodiment 1 FIG. A solid billet made of medium carbon steel (S45C) with a diameter of 100 mm, 81 mm, 70 mm, and 53 mm was used as a sample.
These were pierced using a plug composed of 5% Cr-1% Ni-3% W to obtain a hollow piece having an outer diameter of 105 mm, a wall thickness of 5.3 mm, and a length of 1000 mm. Table 1 summarizes the perforation ratio and expansion ratio for each billet.

[0022]

[Table 1]

The crossing angle γ of the inclined rolling rolls 11 and 21 is 0 °,
There were four types, 10 °, 20 °, and 30 °, and the inclination angle β was 12 °. The inlet face angle α ₁ is 3 °, and the outlet face angle α ₂ is 4 °
And The temperature at the time of drilling was set to 1200 ° C., and the result of measuring the plug load for each intersection angle γ is shown in FIG.

It is clear from FIG. 1 that the expansion ratio has a large effect on the plug load. As the expansion ratio increases, the plug load decreases significantly. From this experimental result, it can be inferred that in order to obtain hollow pieces of the same size, the life of the plug becomes longer as the billet having a smaller diameter is used. Although the influence of the cross angle γ is small, the plug load slightly increases as the cross angle γ increases.

Embodiment 2 FIG. Using the same sample and plug as in Example 1, a drilling experiment was repeated under the same conditions. FIG. 2 shows the result of an actual investigation of the life of the plug (the number of usable perforations). From Example 1, it was inferred that the longer the expansion ratio, the longer the life of the plug, but it was confirmed in this example that the plug life greatly varied depending on the expansion ratio.
Therefore, when obtaining a hollow piece of a predetermined size, it has been demonstrated that the life of the plug (the number of perforations) can be significantly extended by using a billet having a small diameter.

The expansion ratio in the conventional parallel perforation method is about 1.05 to 1.10. However, when the expansion ratio is 1.5, the life becomes 2 to 2.5 times, and the expansion ratio is increased. To
It is clear from this example that the life is increased 3 to 4 times when 2.0 is set. Therefore, only by changing (decreasing) the diameter of the billet to be used, the life of the plug is greatly extended, and the cost of consumables can be reduced.

The influence of the crossing angle γ is also apparent, and the longer the crossing angle γ, the longer the life. This tendency becomes more remarkable as the pipe expansion ratio increases. This is considered to be due to the following reasons. That is, when the roll crossing angle γ is large, the plug load slightly increases, but the drilling speed naturally increases beyond the influence of the plug load, so that the time required for drilling is shortened and the life is extended.

In the present invention, the fact that the cross angle γ is 0 ° corresponds to the conventional Mannesmann perforation method.

[0029]

As described above, according to the method for manufacturing a seamless pipe according to the present invention, the crossing angle γ of the inclined rolls is set to 0 ° ≦ γ <5 °.
By increasing the pipe expansion ratio to 1.15 or more, it is possible to increase the relative heat capacity ratio of the perforated plug, suppress the wear of the plug including the wear of the tip and the rough skin of the body, and extend the life, etc. The present invention has excellent effects.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a roll crossing angle and a plug load at each expansion ratio.

FIG. 2 is a graph showing a relationship between a roll crossing angle and a plug life at each expansion ratio.

FIG. 3 is an explanatory view showing a process of manufacturing a seamless pipe.

FIG. 4 is an explanatory view showing a process of manufacturing a seamless pipe.

FIG. 5 is a front view showing a piercing mill;

FIG. 6 is a partially broken plan view as seen from the direction I in FIG. 5;

FIG. 7 is a partially broken side view as viewed from the II direction in FIG. 5;

8 is a partially broken plan view showing a support portion of the inclined rolling roll shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Solid billet 2 Hollow piece 14 Plug 21 and 22 Inclined rolling roll B Bore mill

Claims (2)

(57) [Claims] 1. A metal shell is rolled by a pair of inclined rolls, and a perforated plug is inserted into the metal round bar in the longitudinal direction thereof to obtain a hollow shell. In the method for producing a roll, the crossing angle γ of the inclined rolling roll is 0 ° ≦
A method for producing a seamless pipe, wherein γ <5 ° and an expansion ratio is 1.15 or more. 2. A metal shell is rolled by a pair of inclined rolls, and a perforated plug is inserted into the metal round bar in the longitudinal direction thereof to obtain a hollow shell. In the method of manufacturing, using a perforated Bragg of a diameter larger than the metal round bar piece, the crossing angle γ of the inclined rolling roll is 0 ° ≤
A method for producing a seamless tube, characterized by piercing with γ <5 °.