JP3402268B2 - Method for piercing and rolling seamless metal pipes - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for piercing and rolling a seamless metal tube by a disc roll type inclined rolling mill. More specifically, the present invention relates to a seamless metal pipe piercing / rolling method for improving the stability of rolling during piercing / rolling and the quality of the hollow shell obtained by piercing / rolling.

[0002]

2. Description of the Related Art The Mannesmann-Plug method or the Mannesmann-Mandrel mill method is the most commonly used method for producing a seamless metal tube (hereinafter, also referred to as a seamless tube). In this method, a solid billet heated to a predetermined temperature in a heating furnace is pierced by a piercing and rolling machine (hereinafter also referred to as a piercer) to form a hollow shell, which is mainly drawn by a drawing mill such as a plug mill or a mandrel mill. , And then the outer diameter is mainly reduced by a reduction rolling machine such as a sizer or a stretch reducer to obtain a seamless pipe having a predetermined size.

Usually, a piercer has a rolled material to be perforated (hereinafter,
A pair of main rolls and barrel-shaped or cone-shaped main rolls in which the roll axis is inclined with respect to the path center of the solid billet (hereinafter also referred to as billet) and the hollow shell that is the rolled material, and the inner surface control tool. An inclined rolling mill having a plug and further having a pair of guide shoes or a pair of disc-shaped disc rolls for guiding the material to be rolled and the main roll alternately arranged around the path center is used.

FIG. 6 is a schematic plan view of a piercer having a cone-shaped main roll, and FIG. 7 is a schematic side view of the piercer.
FIG. 8 is a sectional view taken along line I-I of FIG.

In FIGS. 6 and 7, the main rolls 10A, 10
B is a gorge portion 1 having a diameter D1 at an intermediate portion in the central axis direction.
1 is provided. An entrance surface 12 having an entrance surface angle θ1 is provided on the entrance side of the gorge portion 11 (on the left side of FIGS. 6 and 7), and an exit surface angle on the exit side of the gorge portion 11 (on the right side of FIGS. 6 and 7). θ
Two exit faces 13 are provided, and a pair of them are arranged at positions facing each other horizontally or vertically with a pass line sandwiched so that the roll opening Rg of the gorge portion 11 has a predetermined value.

The central axis of the main roll has a three-dimensional inclination with respect to the pass line, and the angle between the central axis of the main roll and the pass line shown in FIG. 6 is a crossing angle γ, which is shown in FIG. The angle between the main roll central axis and the pass line is the inclination angle β.

As shown in FIG. 6, the plug 2 has a warhead shape as a whole, and its base end is supported by the tip of a mandrel bar M connected to a thrust block (not shown). The plug 2 is held in the middle of the main rolls 10A and 10B so as to substantially coincide with the pass line XX, and is rotatable about the pass line XX as an axial center.

As shown in FIG. 8, the disk roll 30
Each of u and 30d has a concave groove hole type 3a serving as a sliding surface with the material to be rolled on its outer peripheral surface, and its shape is a disk shape having a groove bottom diameter of D2. One pair of disc rolls
The upper and lower sides or the left and right sides of the pass line XX in a direction substantially orthogonal to the main rolls 10A and 10B face each other, and
Distance Dg between groove bottoms of a (hereinafter referred to as disc opening)
Is arranged so as to have a predetermined value, and is driven and rotated in the traveling direction of the material to be rolled by a driving device (not shown).

In the piercing and rolling by the piercer configured as described above, as shown in FIG. 6, the billet B heated to a predetermined temperature in the heating furnace is passed through the pass line from the inlet face 12 side of the main rolls 10A, 10B. It is transported in the direction of the white arrow along XX, and the entrance surfaces 12 and 1 of the main rolls 10A and 10B.
Bitten between two. Billet B is then the main roll 1
The hollow shell H is subjected to an intermittent reduction once per half rotation between the plug 2 and the main rolls 10A and 10B while it is screwed forward by the rotation of 0A and 10B.
Becomes

At this time, the grooved hole type of the disk roll, which is rotationally driven following the spiral rotational movement of the billet, serves to prevent the outer diameter of the hollow shell from increasing. That is, as shown in FIG. 8, the material to be rolled swells in the direction perpendicular to the rolling direction under the rolling by the main roll, but this bulging is restrained by the groove hole die 3a. Therefore, the material to be rolled immediately after the start of drilling is rolled while exhibiting an elliptical shape, but is gradually formed into a circular shape along with the spiral rotation movement, and is formed into a hollow shell having a predetermined shape and dimension.

When a hollow shell having a desired outer diameter is obtained with such a piercer, the disc opening is set based on the setting conditions of the main roll, the size of the plug used for perforation, and the plug position. .

When the disc opening is small, the pressure on the contact surface between the disc roll and the material to be rolled becomes large, which causes problems such as frequent occurrence of guide flaws on the outer surface of the hollow shell. Further, if the disc opening is large, the ellipticity of the rolled material during drilling becomes large, which causes problems such as misrolling such as tail clogging and deterioration of uneven thickness. Therefore, it is the actual situation that the setting range of the disc opening is considerably restricted, so that it becomes difficult to roll the disc into a desired size and shape by adjusting the disc opening, and it is unavoidable to change the plug shape and the drilling conditions. There is a problem that is.

In addition, when the outer diameter of the hollow shell changes significantly due to the setting change of the main roll, plug, etc., there is a problem that the disk opening cannot be dealt with and frequent dimensional defects occur. In particular, the disc roll has less restraining force on the material to be rolled on the outlet side of the main roll than a plate-shaped guide shoe, so that the outer diameter of the hollow shell changes greatly and adjustment becomes difficult. If the outer diameter of the hollow shell cannot be adjusted, rolling will stop due to interference with the piercer guide on the exit side or steadya, or the inner surface of the hollow shell will stick to the mandrel bar. There is a problem that the reduction distribution changes and hinders rolling.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, prevent the occurrence of rolling flaws and rolling troubles when changing the outer diameter target value of a hollow shell, and perforate holes. An object of the present invention is to provide a method for piercing and rolling a seamless metal tube, which suppresses a change in outer diameter of the hollow shell when conditions are changed and enables stable piercing and rolling.

[0015]

DISCLOSURE OF THE INVENTION The present inventors have made various studies, paying particular attention to the arrangement of disc rolls.
The following findings were obtained.

A. When the disc roll is tilted with respect to the pass line and the tilt angle is changed, the outer diameter of the hollow shell changes significantly.

B. Therefore, by changing the inclination angle of the disk roll, it is possible to deal with the change of the outer diameter target value of the hollow shell, and it is possible to suppress the change of the outer diameter of the hollow shell when the drilling conditions are changed. .

C. The disc roll can be moved in the direction of the pass line based on the point on the pass line where the roll opening in the gorge portion is the minimum, and the ratio (Dp / Bd) of the moving distance Dp to the diameter Bd of the solid billet and By setting the ratio (Dg / Bd) of the opening degree Dg of the disc roll to the diameter Bd of the solid billet within an appropriate range, it is possible to make the action of the above b by changing the inclination angle of the disc roll more effective.

The present invention has been completed based on the above findings, and its gist is as follows.

(1) A joint for obtaining a hollow shell by arranging a plug along a pass line between a pair of main rolls and a pair of disc rolls alternately arranged around the pass line and perforating a solid billet. In the method of piercing and rolling a metal-free pipe, the disc roll is provided so as to be tiltable with respect to the pass line and movable in the pass line direction, and the inclination angle of the disc roll is adjusted so that the outer diameter of the hollow shell matches the target value. A method for piercing and rolling a seamless metal tube, which comprises adjusting.

(2) Further, the moving distance D of the disk roll
Ratio of p to diameter Bd of solid billet (Dp / Bd), opening Dg of disc roll and diameter B of solid billet
The ratio (dg / Bd) with d is adjusted within the range of 0.98 ≦ Dg / Bd ≦ 1.08 −0.3 ≦ Dp / Bd ≦ + 0.3. Method for piercing and rolling seamless metal tubes.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION The punching method of the present invention will be described below in detail with reference to the drawings. Note that the following description is for the case where the main roll shape is a cone type, but the same can be applied to the case where the main roll shape is a barrel type.

FIG. 1 is a schematic plan view of a piercer for carrying out the piercing and rolling method of the present invention, and FIG. 2 is a schematic side view of the piercer. FIG. 3 is a sectional view taken along line III-III in FIG. Figure 4 shows the main roll with no tilt angle,
It is a top view which shows the positional relationship of a main roll and a disc roll typically.

FIG. 5 is a schematic view showing the opening degree of the disc roll and its shape. FIG. 5 (a) is a side view and FIG. 5 (b) is a front view.

1-2, main rolls 1A, 1B
Is a gorge portion 11 having a diameter D1 at an intermediate portion in the central axis direction.
Is equipped with. An entrance surface 12 is provided on the entrance side (the left side in FIGS. 1 and 2) of the gorge portion 11, and the entrance surface is a truncated cone whose diameter decreases toward the end surface side of the main roll. An exit surface 13 is provided on the exit side (the right side in FIGS. 1 and 2) of the gorge portion, and the exit surface has a truncated cone shape whose diameter increases toward the end surface side of the main roll. The inlet face angle θ1 represents the angle between the pass line XX and the inlet face, and the outlet face angle θ2 represents the angle between the pass line XX and the outlet face. As described above, the shape of the main roll is a cone shape as a whole, and the pair of rolls is placed in a position facing left or right or up and down with the pass line sandwiched so that the roll opening Rg in the gorge portion 11 has a predetermined value. Will be placed.

The central axis of the main roll has a three-dimensional inclination with respect to the pass line, and the angle between the central axis of the main roll and the pass line shown in FIG. 1 is a crossing angle γ, which is shown in FIG. The angle between the main roll central axis and the pass line is the inclination angle β.

As shown in FIG. 1, the plug 2 has a warhead shape as a whole, and its base end is supported by the tip of a mandrel bar M connected to a thrust block (not shown). The plug 2 is held so as to substantially coincide with the pass line XX at an intermediate portion of the main rolls 1A and 1B, and is rotatable about the pass line XX as an axial center.

As shown in FIG. 3, the disc roll 3u,
3d has a concave groove hole type 3a which becomes a sliding surface with the material to be rolled on its outer peripheral surface, and its shape is a disk shape having a groove bottom diameter of D2, and the main rolls 1A, 1B. Are arranged so as to face each other above and below or to the left and right of the pass line XX in a substantially orthogonal direction, and the distance between the groove bottoms of the groove hole molds 3a, 3a, that is, the disc opening Dg is set to a predetermined value. Further, the disc rolls 3u and 3d are, as shown in FIG.
While being provided so as to be movable in the traveling direction and the reverse direction of the material to be rolled with the point O on the pass line XX at which the roll opening in the gorge portion 11 of A and 1B is the minimum as a base point,
On the exit side of rolling, in the direction opposite to the rotating direction of the material to be rolled, on the entering side of rolling, in the same direction as the rotating direction of the material to be rolled, the pass line X
It is provided so as to be able to incline in opposite directions with respect to −X at an inclination angle α (hereinafter, also referred to as a disk inclination angle), and is configured to be driven to rotate in the traveling direction of the material to be rolled by a driving device (not shown). . The distance Dp between the axial center of the disc roll and the base point is referred to as the disc distance, and the case where the axial center of the disc roll is on the advancing direction side from the base point is (+), and the one on the reverse side is (-). It is represented by.

According to the present invention, the piercer configured as described above is used, and the disc inclination angle is changed so that the outer diameter of the hollow shell obtained by piercing and rolling matches the target value. To do. Hereinafter, a specific example will be described.

Table 2 shows the outer diameter of the hollow shell obtained when variously changing the disk tilt angle from the initial setting value of 3 ° under the perforation conditions shown in Table 1. The difference between the initial set value of the disk tilt angle and the changed disk tilt angle is called the disk tilt angle change amount and is represented by Δα.

[0031]

[Table 1]

[0032]

[Table 2]

As shown in Table 2, the outer diameter of the hollow shell can be significantly changed by changing the disk inclination angle from the initial setting value of 3 °. Therefore, the change of the target value of the outer diameter of the hollow shell can be dealt with by changing the disc inclination angle. Moreover, a change in the outer diameter of the hollow shell that occurs when the perforation conditions such as the inclination angle of the main roll are changed can be suppressed by changing the disc inclination angle.

In a preferred embodiment of the present invention, the ratio (D) of the moving distance Dp of the disk roll to the diameter Bd of the solid billet.
p / Bd) and the ratio (Dg / Bd) between the disc roll opening Dg and the diameter Bd of the solid billet are 0.98 ≦ Dg / Bd ≦ 1.08 −0.3 ≦ Dp / Bd ≦ + 0.3 Adjust to the range.

When Dg / Bd is less than 0.98, seizure between the disk roll and the material to be rolled is likely to occur, and in the worst case, rolling is impossible. If it is larger than 1.08, the thickness of the hollow shell obtained by rolling becomes large and the product dimension becomes out of range.

When Dp / Bd is less than -0.3, there are problems that the roundness of the outer diameter of the hollow shell is deteriorated and the uneven thickness is increased. If it is larger than 0.3, there is a problem that uneven thickness is increased due to insufficient restraint of the rolled material on the inlet side and rolling is stopped due to restraint on the outlet side.

In the piercing and rolling by the piercer configured as described above, as shown in FIG. 1, the billet B heated to a predetermined temperature in the heating furnace has the inlet surface 1 of the main rolls 1A and 1B.
It is transported from the second side along the path line XX in the direction of the white arrow, and is caught between the inlet faces 12, 12 of the main rolls 1A, 1B. Billet B is then the main roll 1A, 1B
The hollow shell H is formed by rotating the plug 2 while advancing while rotating spirally, and intermittently thickening is performed once per half rotation between the plug 2 and the main rolls 1A and 1B.

[0038]

(Embodiment 1) Disk tilt angle when piercing and rolling was carried out under the conditions shown in Table 3 by using the piercer having the basic structure shown in FIGS. 1 to 3 and the outer diameter target value of the hollow shell was changed. The influence of the change and the proper range of Dp / Bd and Dg / Bd were confirmed.

[0039]

[Table 3]

As shown in Table 3, the initial settings at the start of piercing and rolling are as follows: the reference outer diameter of the hollow shell is 91 mm, the disc tilt angles are 1 ° and 4 °, the disc opening is 73 mm, and the disc moving distance is 0 mm. However, after that, the outer diameter target value of the hollow shell was changed to 86 mm and 84 mm, and at that time, the disc inclination angle, the disc opening degree, and the disc moving distance were changed, and rolling was performed. As a comparative example, rolling was performed with the disc inclination angle fixed at the initial setting and only the disc opening and the disc movement distance changed. Table 4 shows the results of piercing and rolling together with comparative examples. It should be noted that the case where problems such as rolling defects and rolling stop did not occur is indicated by ◯, and the case where the above problems occurred is indicated by X.

[0041]

[Table 4]

As shown in Table 4, in the comparative example, problems such as rolling defects and rolling stop occurred. In the example of the present invention, it was possible to change the outer diameter target value of the hollow shell without causing the above problems.

(Embodiment 2) Using the piercer having the basic structure shown in FIGS. 1 to 3, the disk tilt angle, the disk opening, and the disk moving distance are changed according to the tilt angle of the main roll under the conditions shown in Table 5. Then, piercing and rolling were performed. As a comparative example, rolling was performed with the disc inclination angle fixed at the initial setting and only the disc opening and the disc movement distance changed.

[0044]

[Table 5]

Table 6 shows the results of piercing-rolling together with comparative examples. The ratio (ΔD / D) of the difference (ΔD) between the outer diameter of the obtained hollow shell and the target outer diameter and the target outer diameter (D) is ± 1%.
Those that were within were rated as ◯, and those that were more than 1% or less than -1% were rated as x.

[0046]

[Table 6]

As shown in Table 6, in the comparative example, the outer diameter was not sufficiently corrected even if the disc opening and the disc moving distance were changed. In the example of the present invention, the outer diameter of the hollow shell could be rolled within ± 1% of the target outer diameter even if the inclination angle was changed in the range of 12 to 7 °.

[0048]

According to the present invention, when the outer diameter of the hollow shell is changed, rolling defects, rolling troubles, etc. are prevented from occurring, and when the drilling conditions are changed, the outer diameter change of the hollow shell is suppressed.
Stable piercing and rolling becomes possible. Therefore, economic effects such as improvement of product quality and reduction of dimensional defect rate can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a piercer for carrying out the piercing and rolling method of the present invention.

FIG. 2 is a schematic side view of the piercer shown in FIG.

3 is a sectional view taken along line III-III in FIG.

FIG. 4 is a plan view schematically showing a positional relationship between a main roll and a disc roll in a state where an inclination angle is not given to the main roll.

5A and 5B are schematic diagrams showing an opening degree of a disc roll and its shape, wherein FIG. 5A is a side view and FIG. 5B is a front view.

FIG. 6 is a schematic plan view of a piercer having a cone-shaped main roll and a disc roll.

FIG. 7 is a schematic side view of the piercer shown in FIG.

8 is a cross-sectional view taken along the line I-I of FIG.

[Explanation of symbols]

1A, 1B, 10A, 10B: main roll, 2: plug, 3u, 3d, 30u, 30d: disc roll, 3a: slotted type, 11: Gorge section 12: Entrance surface, 13: Exit surface, M: Mandrel bar, H: hollow tube, B: Billet.

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-7-124612 (JP, A) JP-A-3-27806 (JP, A) JP-A-8-174013 (JP, A) JP-A-8- 215714 (JP, A) Actual Kaihei 7-9501 (JP, U) International Publication 96/21526 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) B21B 19/04

Claims (2)

(57) [Claims] 1. A seamless shell for arranging a plug between a pair of main rolls and a pair of disc rolls alternately arranged around a pass line along the pass line and perforating a solid billet to obtain a hollow shell. In the method of piercing and rolling a metal pipe, a disc roll is provided so as to be tiltable with respect to the pass line and movable in the pass line direction, and the tilt angle of the disc roll is adjusted so that the outer diameter of the hollow shell matches the target value. A method for piercing and rolling a seamless metal tube, comprising: 2. The ratio (Dp / Bd) of the moving distance Dp of the disc roll to the diameter Bd of the solid billet and the ratio (Dg / Bd) of the opening Dg of the disc roll to the diameter Bd of the solid billet. Is adjusted to a range of 0.98 ≦ Dg / Bd ≦ 1.08 −0.3 ≦ Dp / Bd ≦ + 0.3. 3. The seamless metal pipe piercing / rolling method according to claim 1, wherein