JPH07241609A - High expansion rolling method of seamless tube - Google Patents

Abstract

PURPOSE:To suppress the variation in the longitudinal direction of the outside diameter of a tube after rolling by making the rotational speed of disk guide shoes during rolling the tip of a material to be rolled faster than the rotational speed of the disk guide shoes during rolling the stational part in high expansion rolling with an inclined rolling mill. CONSTITUTION:An arithmetic and control circuit 40 controls the rotational speed of a forced driving motor 42 for the disk guide shoes 33A, 33B through a motor driving circuit 41. The arithmetic and control circuit 40 calculates the advance amount of the tube with rolling rolls 31A, 31B after detecting the start of biting the tip of a hollow tube stock 32A with a load cell 43 and operates the time for rolling the tip of the tube having a prescribed length that is predetermined and the time for rolling the stationary part of tube thereafter. In this way, the arithmetic and control circuit 40 controls the rotational speed of the disk guide shoes 33A, 33B at the time of rolling the tip of the tube to the stational part of the tube. The rotational speed of the disk guide shoes 33A, 33B in the tip of the tube is made faster than the rotational speed of the disk guide shoes 33A, 33B in the stational part of the tube. In this way, the metal flow in the longitudinal direction is accelerated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for highly expanding and rolling a seamless pipe such as a seamless steel pipe.

[0002]

2. Description of the Related Art The Mannesmann method is the mainstream in the manufacturing process of seamless pipes, and it is roughly classified into a plug mill method and a mandrel mill method depending on the rolling method. It consists of a piercing step, a drawing and rolling step of thinning and drawing the pierced hollow shell, and a finish rolling step of squeezing the drawn and rolled hollow shell to a predetermined outer diameter or a constant diameter.

The plug mill method is a method generally used for manufacturing medium diameter seamless pipes. In this method, a round billet is heated in a heating furnace and pierced and rolled by a Mannesmann piercer, which is an inclined rolling machine, to form a hollow shell. The obtained hollow shell is further thinned and expanded by an elongator, which is also a slant rolling machine, and further thinned and reduced by a plug mill having a pair of hole-type rolling rolls, and then slant rolled. The reeler, which is a machine, expands the pipe with a small amount of wall thickness reduction, and polishes the inner and outer surfaces of the pipe. The raw tube rolled by the reeler is reheated and then the size is adjusted by a sizer to obtain a product.

FIG. 7 is an explanatory view showing an example of changes in the outer diameter of the rolled material on the delivery side of each rolling step of the above-described plug mill rolling line. In both the elongator for thinning and expanding the hollow shell and the reeler for polishing by thinning and expanding, the expansion ratio is at most several percent to 17 or 18%, so products with a wide range of outer diameters Therefore, billets with various outer diameters are required, which is one factor that hinders productivity. Therefore, in recent years, for the purpose of reducing the material billet size and simplifying the equipment, there has been proposed a pipe rolling schedule in which the pipe is expanded more than before in the drawing process.

However, in an inclined rolling machine having a barrel type roll shape such as the conventional elongator and reeler, when attempting to expand the hollow shell highly, there is a problem in that the shell is not properly caught and the tail slips out. It is known that the hollow breaks due to flaring. Here, the high expansion ratio means that the expansion ratio E _r is 0.15 or more. Generally, in piercing rolling with barrel type rolls arranged at an inclination angle β, the roll diameter gradually decreases on the exit side from the gorge part and the peripheral speed becomes slower, so the wall thickness is reduced and the cross-sectional area decreases Will be applied to the material to be rolled, resulting in twisting of the material to be rolled,
It is said that additional shear strain is generated in the cross section.

In recent years, in order to solve these problems and expand the pipe more than ever, a pipe rolling method using an inclined rolling mill using a cone-type roll having a cross angle has been proposed. In the inclined rolling in which the cone-shaped rolls are inclinedly arranged at a constant advancing angle β, and the inclination rolling is performed by intersecting the pass line at the crossing angle γ, the roll diameter gradually increases toward the rolling-out side, and the peripheral speed increases. This is because the brake on the material to be rolled becomes light and it is possible to suppress the twist of the material to be rolled and the generation of additional shear strain in the cross section.

For example, in Japanese Examined Patent Publication No. 3-77005, the crossing angle as shown in FIGS. 8 and 9 is set to 2 ° to 35 °, and the contour line of the roll is composed of a conical entrance portion and a rotating hyperboloid portion. A characteristic diameter expansion rolling mill has been proposed. According to this method, the intermediate heating step, which is originally necessary, becomes unnecessary, and it is possible to manufacture a thin large-diameter steel pipe at low cost.

On the other hand, Japanese Examined Patent Publication No. 5-38647 discloses a plug having two or more rolls each having a truncated conical diameter portion, an enlarged diameter portion and a sizing portion and a reeling portion as shown in FIG. With a cross-type inclined rolling mill equipped with at least the following, the roll surface angle α ₂ of the expanding portion is set to α ₂ > 5 °, the roll surface angle α ₃ of the sizing portion is set to α ₃ <α ₂ , and 0 ° ≦ α ₃ ≤10 °
And the reeling portion of the plug is arranged to face the sizing roll surface, and the reeling surface angle is approximately matched with the sizing portion roll surface angle α ₃ to perform pipe expanding piercing rolling or pipe expanding rolling. Is proposed. According to this method, it is possible to set the reeling portion of the plug to be long, and it is possible to improve the slip-out property, and as a result, it is possible to suppress the occurrence of uneven thickness and variation in outer diameter.

[0009]

However, as a result of diligent research conducted by the present inventor, as a result of using a cone type roll, it is possible to achieve a high expansion tube as compared with the case of using a barrel type roll. Only by using the added cone type roll, there is a limit to the range in which it can expand itself, and if it exceeds a certain limit, problems such as defective biting of the raw tube, defective pulling out of the bottom, and flaring and tearing of the hollow will occur. It was left.

According to the above-mentioned Japanese Patent Publication No. 3-77005, "By making the contour line of the roll a conical entry part and a rotating hyperboloid part, the vortex winding of the roll agrees with the shape of the hollow cone part reasonably, The axis coincides with the axis of the conical portion of the diameter-enlarging cored bar. It is not clear what kind of effect will be concretely obtained by making the contour line of the roll into a conical entry part and a rotating hyperboloid part, let alone an unsuccessful biting of the raw pipe However, it is not clear whether it is effective in preventing the hollow from breaking due to flaring.

On the other hand, in Japanese Examined Patent Publication No. 5-38647, "Because the reeling portion of the plug is opposed to the sizing portion of the roll, it is possible to positively reduce the wall thickness in the entire expanded portion of the rolling roll. The propulsive force for the material to be rolled can be increased to prevent clogging (poor slip-out), and the reeling length can be set to a large value to improve the uneven thickness and also to suppress fluctuations in outer diameter to improve pipe quality. It can be greatly improved. Although a certain effect is observed in preventing the trailing edge defect, it is not effective in preventing the hollow from breaking due to defective biting or flaring.

Further, as a result of the earnest research by the present inventor, regardless of whether the barrel type or the cone type is used as the rolling roll, when the tube expansion ratio E _r becomes large, the outer diameter of the other tip portion becomes steady. The outer diameter variation in the longitudinal direction of the pipe, which is larger than the outer diameter of the portion, is likely to occur. This is because in the steady pipe part, the forward tension based on the spiral progress of the preceding rolling part acts to steadily promote the forward metal flow, whereas in the pipe tip part, there is no action of this forward tension. The rolled material becomes stagnant. Therefore, the metal flow caused by the reduction of the wall thickness of the material to be rolled by the rolling roll and the plug is directed in the pipe circumferential direction rather than the pipe longitudinal direction at the pipe tip, which results in the outside of the pipe tip. The diameter can be made larger than that in the steady pipe section.

According to the experiment by the inventor, the variation of the outer diameter in the longitudinal direction of the pipe is as shown in FIG. 12, for example. Figure 12
When a hollow shell having an entrance-side outer diameter D _i of 70 mm and an entrance-side wall thickness t _i of 30 mm is expanded and rolled so that the exit-side outer diameter D _o is 90 mm and the exit-side wall thickness t _o is 15 mm, It is the outer diameter distribution in the pipe longitudinal direction. As a result, the diameter expansion ratio of the tip outer diameter to the steady portion outer diameter is 4.4%.

The above-mentioned variation of the outer diameter in the longitudinal direction of the pipe becomes particularly remarkable in the high tube-expansion rolling using the cone-type rolling roll which enables the high tube-expansion rolling with the tube expansion ratio E _r of 0.15 or more.

It is an object of the present invention to suppress longitudinal fluctuation of the pipe outer diameter after rolling in high pipe rolling using a tilt rolling mill.

[0016]

According to the present invention as set forth in claim 1, a pair of rolling rolls are inclinedly arranged at a constant advance angle β with respect to a pass line, and the rolling lines are arranged on the pass line between the rolling rolls. When expanding a hollow shell highly by using a pipe rolling mill with plugs, a forced drive disc guide shoe that guides the outer surface of the material to be rolled to the side of the rolling region formed by a pair of rolling rolls. , And the rotation speed of the disc guide shoe during the rolling of the tip of the material to be rolled,
It is designed to be faster than the rotation speed of the disc guide shoe during rolling in the steady portion.

According to a second aspect of the present invention, in the present invention according to the first aspect, the pipe rolling mill further comprises a pair of rolling rolls as cone type rolling rolls, and the pair of cone type rolling rolls is a pass line. with inclined arrangement at a constant advance angle β with respect to, the entrance face angle with respect to the pass line alpha ₁
And a projecting side angle α ₂ with a cross angle γ with respect to the pass line, and a plug is arranged on the pass line between the pair of cone type rolling rolls.

The present invention according to claim 3 is the same as the invention according to claim 2, wherein 5 ° ≦ β ≦ 25 ° and 10 ° ≦ γ ≦
40 °, 20 ° ≦ β + γ ≦ 50 °.

[0019]

The function of the present inventors is as follows as a result of detailed examination of the rolling condition of the material to be rolled at the time of high expansion rolling of the hollow shell using the inclined rolling mill. The optimum value of the shape and the effect of (B) disc guide shoe rotation speed control were found.

(A) Suitable values for roll arrangement and roll shape: A pair of cone-type rolling rolls are inclined and arranged at a constant advance angle β with respect to the pass line, and the entrance side angle α ₁ and the exit side surface with respect to the pass line. When the hollow shell is expanded highly, β, γ, and β + γ are set in the following ranges by arranging them so that they have an angle α ₂ and a crossing angle γ with respect to the pass line.
° ≤ β ≤ 25 °, 10 ° ≤ γ ≤ 40 °, 20 ° ≤ β + γ ≤ 50 ° and set α ₁ and α ₂ in the following range, and 0.5 °
≤α ₁ ≤5 °, 3 ° ≤α ₂ ≤10 °, α ₁ ≤α ₂ , and
Between the metal thinning ratio R _t and the pipe expansion ratio E _r , 1 ≦ E _r / R _t ≦ 3,
Where R _t = (t _i -t _o ) / t _i , E _r = (D _o -D _i ).
/ D _i , t _i : inlet side hollow shell thickness, D _i : inlet side hollow shell outer diameter, t _o : outlet side wall thickness, D _o : outlet side tube outer diameter It has been found that it is possible to significantly prevent the occurrence of hollow biting, defective tail slippage, and hollow breakage due to flaring, and to perform high pipe rolling.

[0021] That is, the cone-type roll, as shown in FIGS. 1 to 3 GORE - di section diameter D _R is 700 mm, the roll barrel length L
_R is 600 mm, roll length L ₁ from the entrance end to the gorge part
Is 250 mm, the entrance side angle α ₁ is 3 °, the exit side angle α ₂ is 5 °,
It is an inclined rolling mill with a crossing angle γ of 20 ° and a lead angle β of 15 °. It uses a hollow shell with a diameter _DH of 80 to 120 mm and a wall thickness t _H of 15 to 40 mm as the material to be rolled, and the roll gap E and the plug are advanced. The amount L was variously changed and the wall-thickness reduction ratio R _t and the pipe expansion ratio E _r were changed for pipe expansion rolling, and the occurrence of hollow biting due to defective biting and flaring was investigated. FIG. 11 shows the results organized by taking R _{t on} the horizontal axis and E _r on the vertical axis.

As is clear from the figure, a pair of cone type rolling rolls are arranged at an inclination with a constant advance angle β, and γ
In the slant rolling method of the pipes which are crossed with each other, the thinning rate R _t
And tube expansion ratio E _r in the range of 1 ≤ E _r / R _t ≤ 3, it is possible to avoid defective biting, defective slippage, and hollow breakage due to flaring, and the degree of freedom in rolling setting is improved. It is possible to raise it.

In the present invention, 5 ° ≦ β ≦ 25 °, 10 ° ≦
The reason for setting γ ≦ 40 ° and 20 ° ≦ β + γ ≦ 50 ° is as follows. Within a certain range, the larger the advancing angle β, the crossing angle γ, and the sum β + γ, the more the twist of the material to be rolled and the additional shear strain in the cross section can be reduced, which prevents the hollow tear due to flaring. Effective against
However, β <5 °, or γ <10 °, or β + γ <20
If the angle is °, the effect is not sufficient and hollow breakage due to flaring tends to occur. Therefore, the lower limit of β is 5 °, γ
The lower limit of is 10 °, and the lower limit of β + γ is 20 °. On the other hand, β>
At 25 °, or γ> 40 ° or β + γ> 50 °, the twist of the material to be rolled increases in the opposite direction, and additional shear strain in the cross-section also occurs in the opposite direction, rather causing hollow tearing due to flaring. It tends to occur. Therefore, β is 25 ° and γ is
40 ° and β + γ shall not exceed 50 °.

The reason why 0.5 ° ≦ α ₁ ≦ 5 ° is set is as follows. The entrance side angle α ₁ has an important influence on the biting property of the material to be rolled. If α ₁ exceeds 5 °, the material to be rolled is drastically reduced during biting, and the drag force from the rolling roll required for deformation exceeds the thrust in the forward direction transmitted from the rolling roll. . Therefore, α ₁ is 5 °
Shall not be exceeded. On the other hand, if α ₁ becomes too small, it is necessary to considerably lengthen the roll barrel on the inlet side in order to obtain the outer diameter reduction of the material to be rolled necessary for the thrust in the forward direction. Becomes higher and not practical. Therefore, the lower limit of α ₁ is 0.5 °.

The reason why 3 ° ≦ α ₂ ≦ 10 ° is set is as follows. The larger the flank angle α ₂ is, the shorter the roll barrel on the exit side, which is necessary for the amount of pipe expansion, and the equipment can be downsized, but if it is too large, hollow breakage due to flaring will occur. Is likely to occur.
Therefore, α ₂ shall not exceed 10 °. On the other hand, α ₂
If is too small, it is necessary to lengthen the roll barrel on the outlet side considerably in order to obtain a predetermined amount of pipe expansion, resulting in high facility construction cost and impracticality. Therefore, the lower limit of α ₂ is 3 °.

The reason for setting α ₁ ≦ α ₂ is as follows.
When the exit side angle α ₂ becomes smaller than the entrance side angle α ₁ , in order to obtain a predetermined pipe expansion amount, the roll barrel length is longer than that when the exit side angle α ₂ is larger than the entrance side angle α _1. Becomes relatively long. Therefore, α ₁ does not exceed α ₂ .

(B) Effect of Disc Guide Shoe Rotation Speed Control As shown in FIGS. 1 to 3, the cone type roll has a gorge portion diameter D _R of 350 mm, a plug diameter D _P of 43 mm, and a gorge E of 36 mm.
Lead angle β is 10 °, the intersection angles γ is 20 °, the rolling roll speed is 60 rpm, the disk guide shoe diameter D _Z is 800 mm, shoe spacing in the inclined rolling mill of 52 mm, entry side outer diameter D _i is 40 mm, inlet A model experiment was carried out for expanding and rolling a hollow shell having a side wall thickness t _i of 8 mm and an inlet side length L of 250 mm.

In this model experiment, the disk guide shoe rotation speed was changed to 3.0 rpm, 3.5 rpm, and 4.0 rpm, and the rolled pipe tip outer diameter D _o at each rotation speed was investigated.
As a result, 3.0rpm in D _o is 54.0mm, 3.5rpm in D _o is
At 52.3 mm and 4.0 rpm, D _o was 50.8 mm, and it was confirmed that increasing the disc guide shoe rotation speed can reduce the outer diameter of the pipe tip and suppress its expansion.

That is, in the present invention, "the rotation speed of the disc guide shoe during the rolling of the tip of the material to be rolled should be made faster than the rotation speed of the disc guide shoe during the rolling of the steady portion".
As a result, a forward propulsive force for the tip of the pipe is given by the peripheral speed of the disc guide shoe, the stagnation of the material to be rolled at the tip of the pipe is suppressed, and as a result, the metal flow in the longitudinal direction of the pipe is promoted. This promotes the metal flow in the pipe longitudinal direction by increasing the disc guide shoe peripheral speed at the pipe tip, and promotes the metal flow in the pipe longitudinal direction due to the forward tension due to the spiral advance of the preceding rolling part in the pipe steady part. As a result, the outer diameter of the tube tip portion, which tends to increase in outer diameter if not according to the present invention, is suppressed, and the outer diameter of the tube tip portion is made substantially equal to the outer diameter of the steady tube portion. be able to.

The effect of the disc guide shoe rotation speed control according to the present invention is particularly effective when high expansion rolling with a pipe expansion ratio E _r of 0.15 or more is performed by using a cone type roll as a rolling roll. However, the effect of this disc guide shoe rotation speed control is also useful when a barrel type roll is used as the rolling roll.

[0031]

1 is a plan view showing an inclined rolling mill according to the present invention, FIG. 2 is a side view of FIG. 1, FIG. 3 is a front view seen from the rolling direction of FIG. 1, and FIG. 4 is a disc guide according to the present invention. It is a schematic diagram which shows a shoe rotation speed control circuit.

In FIGS. 1 to 3, a pair of cone type rolling rolls 31A, 31B having a gorge diameter D _R are inclined with respect to the pass line at a constant advance angle β, and
The rolling rolls 3 are arranged so as to have an entrance side angle α ₁ and an exit side angle α ₂ at an intersection angle γ with respect to the pass line.
The disc guide shoes 33A and 33B were arranged on both sides of the rolling region formed by 1A and 31B. In addition, rolling roll 3
In 1A and 31B, the portion of the diameter D _R is an inflection point of the diameter change in the roll axis direction, and the diameter D _R is matched with the gorge portion. Then, the plug 34 was arranged between the both rolling rolls 31A and 31B, and the hollow shell 32A was tilt-rolled at the gorge portion roll gap E of both rolling rolls 31A and 31B to obtain the hollow shell 32B after pipe rolling.

At this time, in the example of the present invention, 5 ° ≦ β ≦ 25
°, 10 ° ≦ γ ≦ 40 °, 20 ° ≦ β + γ ≦ 50 °, 0.5 ° ≦ α
₁ ≦ 5 °, 3 ° ≦ α ₂ ≦ 10 °, and α ₁ ≦ α ₂ . Further, the wall thinning ratio R _t and the pipe expansion ratio E _r are defined as follows: 1 ≦ E _r / R _t ≦ 3
And

The operation and effect of this embodiment will be described below. That is, in the inclined rolling mill having a cone type rolling roll shown in FIG. 1 having a gorge diameter D _R of 700 mm, a cross angle γ, a lead angle β,
The entrance side angle α ₁ and the exit side angle α ₂ are changed as shown in Table 1, and a roll gap E is obtained by using a hollow shell having a diameter _DH of 80 to 120 mm and a wall thickness t _H of 15 to 40 mm as a material to be rolled. And the advanced amount L of plugs were variously changed to change the wall-thickness reduction ratio R _t and the pipe expansion ratio E _r , and pipe rolling was performed. At that time, biting failure, slipping out,
Table 1 also shows the presence or absence of hollow breakage due to flaring.

In all of the comparative examples, even under the condition that the biting failure, the trailing edge failure, and the hollow tearing due to flaring occur, according to this method, the biting failure, the trailing edge failure, and the hollow tearing due to flaring are caused. It did not occur at all.

[0036]

[Table 1]

Further, in FIG. 4, reference numeral 40 denotes an arithmetic control circuit, and the arithmetic control circuit 40 controls the rotation speed of the forced drive motor 42 of the disk guide shoes 33A, 33B via the motor drive circuit 41. Then, the arithmetic control circuit 4
0 additionally includes a load cell 43, and the load cell 43
After detecting the start of biting the tip of the hollow shell 32A,
The pipe advance amount by the rolling rolls 31A and 31B is calculated, and the rolling timing of the pipe tip portion of a predetermined length and the rolling period of the subsequent pipe steady portion are calculated. As a result, the arithmetic control circuit 40 controls the rotational speeds of the disc guide shoes 33A and 33B as described later when rolling the pipe tip portion to the pipe steady portion.

That is, in this embodiment, the disk guide shoe rotation speed was set to the following (a) when rolling from the pipe tip to the pipe steady part.
Control was performed as in the four cases of (d) (FIG. 5), and the longitudinal distribution as shown in FIG. 6 was obtained for the rolling-out side outer diameter D _o .

As the rolling roll, the cone type roll shown in FIGS. 1 to 3 was used, and the roll gorge diameter D _R was 700 mm.
, Plug diameter _DT 65 mm, lead angle β 15 °, crossing angle γ 2
0 °, Gorge E 65mm, Disc guide shoe diameter D _Z 1
The hollow shell 32A has an outer diameter D _i of 70 mm, an inner wall thickness t _i of 30 mm, and a blank tube 32 after rolling.
The target outer diameter D _o of B was 90 mm, and the target wall thickness t _o was 15 mm.

(A) Conventional method The peripheral speed of the disc guide shoe is V = 1.
It was kept constant at 4 (m / min).

(B) Inventive method 1 The peripheral speed V of the disc guide shoe was set to V = 1.6-0.4 x (m / min) for the position x in the longitudinal direction of the blank tube ≤ tip 0.5 (m). x> 0.5 (m) at the tip was kept constant at V = 1.4 (m / min).

(C) Inventive Method 2 V = 1.6 (m / min) was constant for x ≦ 0.2 (m). For 0.2 (m) <x ≦ 0.25 (m) V = 1.6 −2 (x−0.2)
(m / min). For 0.25 (m) <x ≦ 0.45 (m), V = 1.5 (m / min) was kept constant. For 0.45 (m) <x ≤ 0.5 (m) V = 1.5-2 (x-
0.45) (m / min) constant. For x> 0.5 (m), V was constant at 1.4 (m / min).

(D) Inventive method 3 V = 1.6 (m / min) was constant with respect to x ≦ 0.4 (m). For 0.4 (m) <x ≦ 0.5 (m) V = 1.6 −2 (x−0.4) (m
/ min). For x> 0.5 (m), V was constant at 1.4 (m / min).

As a result, as shown in FIG. 6, the conventional method exhibited a non-uniform outer diameter distribution in which the outer diameter of the tip of the pipe was larger than that of the steady portion of the pipe in the longitudinal direction of the pipe. On the other hand, in all of the methods 1 to 3 of the present invention, the outer diameter distribution (D _o ) in the longitudinal direction of the pipe is
Was suppressed to ± 2% of the target value.

[0045]

As described above, according to the present invention, it is possible to suppress the longitudinal variation of the outer diameter of the pipe after rolling in the high expansion rolling by the inclined rolling mill.

[Brief description of drawings]

FIG. 1 is a plan view showing an inclined rolling mill according to the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is a front view seen from the rolling direction in FIG.

FIG. 4 is a schematic diagram showing a disc guide shoe rotation speed control circuit according to the present invention.

FIG. 5 is a schematic diagram showing a disc guide shoe rotation speed control pattern.

FIG. 6 is a diagram showing a distribution of a pipe outer diameter in a longitudinal direction.

FIG. 7 is a diagram showing an example of changes in the outer diameter of the material to be rolled on the delivery side of each rolling step of the rolling line by the conventional plug mill method.

FIG. 8 is a schematic diagram showing a conventional inclined rolling mill.

FIG. 9 is a schematic diagram showing the rolling roll of FIG.

FIG. 10 is a schematic view showing another conventional inclined rolling mill.

FIG. 11 is a diagram showing a situation of occurrence of defective biting, defective slip-out, and hollow tear due to flaring when pipe rolling is performed while changing the thickness reduction ratio and the pipe expansion ratio.

FIG. 12 is a diagram showing a pipe outer diameter longitudinal direction distribution according to a conventional method.

[Explanation of symbols]

 31A, 31B Rolling rolls 32A, 32B Hollow shell 33A, 33B Disc guide shoe 34 Plug 40 Calculation control circuit 41 Motor drive circuit 42 Adjustment drive motor 43 Load cell

Claims (3)

[Claims] 1. A hollow tube rolling mill is used, in which a pair of rolling rolls are inclinedly arranged at a constant advance angle β with respect to a pass line, and a plug is arranged on the pass line between the rolling rolls. For high expansion of the raw pipe, a forced drive disc guide shoe that guides the outer surface of the material to be rolled is placed on the side of the rolling region formed by a pair of rolling rolls. A seamless pipe high expansion rolling method characterized in that the guide shoe rotation speed is set higher than the disk guide shoe rotation speed during rolling in a steady portion. 2. The pipe rolling mill according to claim 1, wherein the pair of rolling rolls are cone type rolling rolls, and the pair of cone type rolling rolls are inclinedly arranged at a constant advance angle β with respect to a pass line, and Cross-arranged at an intersection angle γ with respect to the pass line so as to have an entrance side angle α ₁ and an exit side angle α ₂ with respect to the pass line, and a plug is arranged on the pass line between the pair of cone type rolling rolls. A seamless pipe high expansion rolling method. 3. The method according to claim 2, wherein 5 ° ≦ β ≦ 25 °, 10
A seamless pipe high expansion rolling method where ° ≤ γ ≤ 40 ° and 20 ° ≤ β + γ ≤ 50 °.