WO2004108310A1

WO2004108310A1 - Drilling/rolling method in manufacturing seamless tube

Info

Publication number: WO2004108310A1
Application number: PCT/JP2004/007698
Authority: WO
Inventors: Chihiro Hayashi
Original assignee: Sumitomo Metal Industries, Ltd.
Priority date: 2003-06-06
Filing date: 2004-06-03
Publication date: 2004-12-16
Also published as: JP4196991B2; CN100509192C; EP1649945A4; DE602004031232D1; RU2005141132A; JPWO2004108310A1; EP1649945A1; EP1649945B1; RU2309810C2; CN1795060A

Abstract

A drilling/rolling method in manufacturing a seamless tube capable of suppressing additional shear deformation by suppressing rotational forging effect without so reducing roll diameter, characterized in that the tilt angle (β) of a main roll and the cross angle (Ϝ) of the main roll are held within a range meeting the requirements of the following equations (1) to (3), a relation between the outer diameter (d0) of a solid billet and the outer diameter (d) and wall thickness (t) of a hollow piece after drilling/rolling meets the requirement of the following equation (4), and the inlet diameter (D1), and outlet diameter (D2) of the main roll, and the (d0), (d), and (Ϝ) meet the requirement of the following equation (5). 8º ≤ β ≤ 20º...(1) 5º ≤ Ϝ ≤ 35º...(2) 15º ≤ β + Ϝ ≤ 50º...(3) 1.5 ≤ - ψr/ψθ ≤ 4.5...(4) (d/d0)/(0.75 + 0.025 Ϝ) ≤ D2/D1...(5) Where, in equation (4), ψr = 1n (2t/d0), ψθ = 1n {2 (d - t)/d0}.

Description

Specification

Punch rolling method in the production of seamless pipes

Technical field

The present invention relates to a method for piercing and rolling a billet in a process of manufacturing a seamless pipe. In particular, the present invention relates to a piercing and rolling method capable of producing a thin tube (hollow piece) with a high degree of processing from a billet.

Technology background

[0002] Mannesman plug milling and Mannesmann mandrel milling are the most commonly employed methods for producing seamless pipes. In these methods, a solid billet heated to a predetermined temperature in a heating furnace is pierced by a piercing mill to form a hollow rod-shaped hollow piece, which is mainly reduced in thickness by a stretching mill such as a plug mill or a mandrel mill. And make it a hollow shell. Next, the outer diameter is reduced mainly by a drawing rolling machine such as a sizer or a stretch reducer to obtain a seamless pipe having a predetermined size. The present invention relates to the first piercing and rolling step in the above steps.

[0003] First, the invention proposed by the present inventors in Patent Documents 1 and 2 will be described as a conventional technique.

Patent Document 1: Japanese Patent Publication No. 5-23842

Patent Document 2: Japanese Patent Publication No. 8-4811

[0004] The invention of Patent Document 1 (hereinafter referred to as a "first prior invention") is a cone-type main port supported at both ends, left and right or up and down across a pass line through which a billet and a hollow piece pass. The inclination angle β of the roll and the crossing angle _{この} of this main roll are kept within the range of the following equation (1) and set (3), and the diameter d of the solid billet and the hollow

0 The joint where the outer diameter d and wall thickness t of one piece satisfies the following formula (4), and the piercing ratio is 4.0 or more, the expansion ratio is 1.15 or more, or the “wall thickness / outer diameter” ratio is 6.5 or less It is an invention of a method for manufacturing a tubeless tube.

[0005] The above-mentioned inclination angle β is an angle formed by the axis of the roll with respect to the horizontal or vertical plane of the pass line. The crossing angle Ί is the angle formed by the axis of the roll with respect to the vertical or horizontal plane of the pass line. 8 ° ≤ ≤20 °

5 ° ≤ γ≤35 °

15 ° ≤ + γ≤5Ο °

1.5≤-Ψ / Ψ ≤4.5

r θ

Where Ψ = ln (2t / d)

r 0

Ψ = ln {2 (d-t) / d}

Θ ο

[0006] The above-mentioned method of the first prior art is remarkably generated in the piercing and rolling step, particularly, in the thin-wall piercing and rolling step with a high working _ratio , by maintaining the roll inclination angle β and the crossing angle _に in appropriate ranges. This is a method in which the rotational forging effect and the added shear deformation are suppressed as much as possible. It also prevents internal flaws (laminate (double cracks occurring at the center of the wall thickness)) that occur in stainless steel and high alloy steel pipes, and distributes circumferential strain Ψ and wall thickness strain Ψ. This method is characterized by reducing the operational troubles such as flare-piping of the pipe meat or clogging of the buttocks by optimizing the amount and satisfying the relationship of the above equation (4).

[0007] The first prior invention described above has made it possible to form pipes of a difficult-to-process material by the Mannesmann pipe forming method, which had to be conventionally made by a tube extrusion method. In addition, thin-wall piercing and rolling with a high degree of processing was made possible, which made it possible to omit or shorten the steps in the subsequent elongation rolling and drawing rolling processes. Therefore, this invention was an invention that greatly contributed to streamlining the manufacturing process of seamless pipes.

[0008] For example, the Mannesmann piercer and the rotary elongator used in the Mannesmann-Plug mill process can replace double piercing and rolling with single piercing instead of double piercing. The Mannesmann-Plug Mill method is a method that goes through the Mannesman piercer → rotary elongator → plug mill → reeler → sizer process.

[0009] In the Mannesmann-mandrel mill system, the number of mandrel mill stands can be reduced by replacing the Mannesmann piercer with a cross-piercing mill. The Mannesmann-Mandrelminore method is a method that goes through the process of Mannesmann piercer → Mandrelminore → Stretch reducer. [0010] Further, the Mannesmann-Assel mill system, that is, the Mannesmann piercer → Assel mill

→ In the process of the stretch reducer process, the introduction of cross-piercing rolling mills was succeeded. According to the cross-piercing mill, so-called “size-free rolling” is possible, in which multi-size hollow pieces can be manufactured from a single-sized billet simply by changing plugs. Operational advantages such as shortening are significant.

[0011] The invention of Patent Document 2 (hereinafter referred to as "second prior invention") is an invention made for the purpose of further optimizing the relationship between the diameter of the cone-type main roll and the diameter of the solid billet. is there. According to the present invention, in order to minimize the effect of the rotary forging and also minimize the additional shearing deformation, the diameter of the gorge portion of the cone-type main roll (ie, the diameter of the roll gouge) D and the billet diameter d

g o is satisfied by satisfying the following expression (a).

2.5≤D /d≤4.5---(a)

g o

[0012] In the second prior invention, in order to stably pierce difficult-to-machine materials such as stainless steel and high alloy steel without causing internal surface flaws or lamination, it is necessary to use a roll roll with respect to the billet diameter. He says that the diameter should be as small as possible. However, in order to reduce the diameter of the roll cartridge, the shaft diameter of the entrance and exit rolls must also be reduced due to the roll structure. In this case, the strength of the bearing that supports the roll shaft is insufficient, and in particular, in the case of a cone type roll, the fatigue strength of the bearing on the entry side is insufficient, and durability becomes a problem. Therefore, excessive reduction in mouth-luggage diameter cannot be recommended in actual operation. Disclosure of the invention

Problems the invention is trying to solve

[0013] It is an object of the present invention to provide a piercing and rolling method capable of minimizing the rotational forging effect without significantly reducing the diameter of the roll gouge and also minimizing additional shear deformation.

Means for solving the problem

[0014] The present inventor has repeated studies to achieve the above object, and has reached the invention of the following piercing and rolling method. The meaning of the reference numerals in the following description is shown in FIG.

[0015] A two-sided supporting cone-type main roll opposed to the left and right or up and down with the pass line interposed The inclination angle β and the crossing angle _Ί are maintained within the ranges satisfying the following equations (1) to (3), and the outer diameter d of the solid billet and the outer diameter d and The relationship with the wall thickness t is

0

(4), and the main roll inlet diameter D, outlet diameter D, and d

A piercing and rolling method in seamless pipe production, wherein 120, d and γ satisfy the following expression (5).

5 ° ≤ γ≤35 ° '(2)

1.5≤-Ψ / Ψ ≤4.5

(d / d) / (0.75 + 0.0257) ≤D / Ό

0 2 1

Where において = ln (2t / d)

0

Ψ = ln {2 (d-t) / d}

o

It is.

[0016] As described above, the inclination angle β is the angle formed by the axis of the roll with respect to the horizontal or vertical plane of the pass line, and the intersection angle γ is the angle of the axis of the roll Is the angle made with respect to the horizontal plane.

In the above method of the present invention, the inlet diameter D and the outlet diameter D of the main roll and the above d

1 2 0

, D and γ preferably satisfy the following equation (6).

D / D ≤ (d / d) / (1.00-0.027γ) '' (6)

2 1 0

The effect of the method of the present invention is that the rolling forging effect and additional deformation are remarkable, the piercing and rolling specific force is S4.0 or more, the pipe expansion ratio is 1.15 or more, or the `` wall thickness / outside diameter ratio '' of a hollow piece. Can be obtained sufficiently by piercing and rolling at 6.5 or less.

BEST MODE FOR CARRYING OUT THE INVENTION

The ranges of the values of the inclination angle β and the crossing angle _{における in} the method of the present invention are the same as the ranges in the inventions of Patent Document 1 and Patent Document 2 described above. These ranges were determined from the viewpoint of reducing the rotary forging effect and minimizing additional shear deformation.

The ratio of logarithmic strain 半径 in the radial direction to logarithmic strain 円 in the circumferential direction, that is, the range of “1Ψ / Ψ” is the same as that in the invention of Patent Document 1. This is the reduction in piercing and rolling. It is determined by the principle and principle of how to distribute the amount in the longitudinal and circumferential directions. If the principle and principle are not met, flare (extruding phenomenon), peeling, or clogging of the bottom of the pipe will occur. Occurs, and the piercing and rolling itself stops.

[0020] A major feature of the present invention is that the roll shape with respect to the billet diameter mainly has a large effect on the rotary forging effect. Hereinafter, this point will be described.

First, the ratio of the inlet diameter D to the outlet diameter D of the cone type roll at the limit of contact between the tube material and the main roll, that is, the diameter expansion ratio “D / D”,

2 2 1 One piece outer diameter d and billet outer diameter d

0, that is, the relationship between the _expansion ratio “d / d” of the tube material and the crossing angle _材料 ,

0

It was investigated from the viewpoint of suppressing additional shear deformation.

Prior to the experiment, an index (index) representing the roll shape was selected. Then, we examined whether various possible indices could be used as indices indicating the relationship between the rotational forging effect and the additional shear deformation. As a result, the expansion ratio “d / d” of the tubing material and the diameter of the cone-shaped roll

0

The ratio with the ratio "D / D", that is, (d / d) / (D / D) was used as the index.

2 1 0 2 1

[0023] The barrel width L on the inlet side with respect to the gorge position of the roll shown in Fig. 1, that is, the barrel width ratio of the distance from the starting point of the roll penetration of the tubing to the roll gorge and the barrel width L on the outlet side.

Two

“L / L” is also considered as an index, but this is not directly related to the rotational forging effect and the added shear deformation.

twenty one

It is irrelevant directly, and the appropriate range was determined from another point of view. Generally, an unnecessary extra length is added to the barrel width, and there is a difficulty in defining the barrel width ratio itself.

In general, as the roll crossing angle _γ increases, the roll expansion ratio “D / Ό” increases.

twenty one

It becomes a remarkable cone shape. If the barrel width L on the outlet side is the same,

Two

The pipe expansion ratio “d / d” is larger if compared with the assumption that the crossing angle is

0

As the roll diameter expansion ratio “D / D” must be smaller, the appropriate “

2 1 0

It is necessary to design a roll that becomes "D / D", and the difficulty of roll design is here.

twenty one

[0025] The roll design must be made from the viewpoint of reducing the rotary forging effect before the plug during piercing and rolling, and minimizing the additional shearing deformation typified by the circumferential shear strain γ after the piercing and rolling. No. This is because embrittlement of the pipe material due to the rotary forging effect is a cause of the occurrence of internal flaws in the pipe, and additional shear deformation is a cause of internal flaw propagation. [0026] The present inventor conducted a piercing and rolling experiment using a carbon steel billet as a test material using a test cross piercing and rolling mill, changing the roll shape, and examined the effect of the roll shape on the rotating forging effect and the added shear deformation. The effects were discussed in detail. Tables 1 and 2 show the experimental conditions. The thickness t of the hollow piece after the piercing and rolling was set so that the ratio of “thickness Z outer diameter”, that is, (t / d) × 100 was 2.53%.

[Table 1]

[Table 2] Table 2

[0029] An example of the effect of the diameter expansion ratio "D / D" and the pipe expansion ratio "dZd" on the rotary forging effect will be described.

2 1 0

Figures 2 (a) and 2 (b) show this. In addition, the expansion ratio "D / D" and the

An example of the effect of the 2 1 expansion ratio “d / d” is shown in Fig. 3 (a) and (b).

0

[0030] The effect of the roll shape on the rotary forging effect depends on whether the main roll and the Stop the disc roll and make a "stopper", and collect a plate-shaped micro tensile test specimen with a parallel part 25 mm in diameter direction (guide direction) perpendicular to the axial direction from the tip end of the plug and a thickness of 3 mm. Then, a tensile test was conducted at room temperature, and the effect of the roll shape on the drawing value (%) was examined and evaluated. The rotary forging effect appears more clearly in the reduction value (%) than in the elongation value (%) in the tensile test.

As the additional shear deformation, attention was paid to the circumferential shear strain γ, and the measurement was performed by a pin embedding method. That is, a plurality of pins were embedded parallel to the axis along the diameter of the solid billet, and the circumferential shear strain γ was measured across the hollow piece after piercing and rolling.

As is apparent from FIG. 2, for example, when the roll crossing angle _Ί is fixed, the smaller the expansion ratio “d / d” and the larger the expansion ratio “D / Ό”, the smaller the aperture value. Can be increased

0 2 1

Wear. That is, the rotary forging effect can be reduced. In other words, the range of the inclination angle where the throttle value of the tube material before the plug is larger than the throttle value of the base material is wider.

Further, as can be seen from FIG. 3, the circumferential expansion strain can be reduced as the pipe expansion ratio decreases and the diameter expansion ratio increases. That is, additional shear deformation can be suppressed. Therefore, even if the expansion ratio is increased, the circumferential shearing deformation does not become too large if the roll crossing angle γ is made sufficiently large so that the expansion ratio becomes large and the roll shape is made appropriate. .

By the way, when the roll shape is inappropriate, that is, when the roll crossing angle is small with respect to the pipe expansion ratio, the diameter expansion ratio becomes too small in order to obtain the pipe expansion ratio, and the outlet diameter D of the roll increases.

2 When the pipe diameter approaches the diameter D and the peripheral speed of the discharge roll at the pipe separation point decreases,

The effect of pulling out is weakened. Thereby, the slip phenomenon between the roll and the tubing becomes pronounced. This slip phenomenon is also affected by the billet diameter, the slip increases on the entry side, and the rotational forging effect begins to appear due to the increase in the number of times of rotational forging, and the inclination angle β at which the pipe material before the plug becomes more brittle than the base material β Range expands. The number of rotation forgings is the number of rotations of the billet until the billet is inserted into the mouth and reaches the plug tip.

[0034] Of course, additional shear deformation also appears significantly. The extreme case is when the exit diameter D of the roll approaches the entrance diameter D. In addition, additional shearing deformation means circumferential shearing.

twenty one

Strain γ, surface torsional shear strain γ and longitudinal shear strain γ You.

4 and 5 show the expansion ratio “d / d”, the roll expansion ratio “D / Ό”, and the roll crossing angle.

0 2 1

6 shows the relationship of γ. These figures also show the results of the roll shape pass / fail determination. In other words, the symbol 〇 indicates that the roll shape is appropriate, and the symbol · indicates that it is inappropriate.

It is necessary to determine whether the roll shape is appropriate or not based on the rotary forging effect. Therefore, whether the ductility (diaphragm value) of the tube material before the plug can be made larger than the diaphragm value of the base material (billet) was used as a criterion for judgment. Then, piercing and rolling were performed at an inclination angle (β) of 12 °, and as described above, a plate-shaped micro-tensile test specimen having a parallel portion of 25 mm and a thickness of 3 mm taken from within the cross section of the tube before the plug was used. A tensile test was performed to determine whether the squeezing value of the tube material before the plug was greater than the squeezing value of the base material. If it is increasing, the force is the above-mentioned symbol, otherwise it is the symbol. From FIGS. 4 and 5, the appropriate roll shape conditions are as follows.

(5/6) + (l / 3) (d / d) ≤ (D / D)

0 2 1

1 + 0.03γ≤ (D / D)

twenty one

If “D / D” is adopted as the roll shape index as described above, “D / D”

2 1 2 1

, “D / d” and γ become clear, but the relationship between the three variables

0

It becomes difficult to do. In order to avoid this problem, the present inventor has set the roll shape index as the ratio of the pipe expansion ratio "d / d" to the roll expansion ratio "D / D", that is, "(d / d) / (D

0 2 1 0 2

/ D) ".

1

FIG. 6 shows the roll shape index “(d / d) / (D / D)”, the expansion ratio “d / d”, and the

It is a figure which shows the relationship of 0 2 1 0 fork angle γ. “(D / d) / (D / D)” on the vertical axis and γ on the horizontal axis

0 2 1

The condition under which “dZd” remains as a parameter in each case is an appropriate condition for the roll shape to be appropriate.

0

Can be represented by two inequalities. That is,

(d / d) / (D / D) ≤0.75 + 0.0257

O 2 1

And from this

(d / d) / (0.75 + 0.025γ) ≤ (ϋ / ϋ)

Ο 2 1

It becomes.

[0038] Here, in order to solve problems in equipment such as the strength and life of the bearing, the diameter of the entrance roll is reduced by ぁ. In order to obtain the optimum roll shape without reducing the size, if the gorge diameter Dg of the roll is set to 4.5 times or more of the billet diameter d,

0

1.00-0.027 y ≤ (d / d) / (D / Ό)

Ο 2 1

Than this,

D / D ≤ (d / d) / (1.00-0.027 7) '' (6)

2 1 0

It becomes. From this equation (6) and the above equation (5),

(d / d) / (0.75 + 0.025 7) ≤ (D / D) ≤ (d / d) / (l .00-0.027 γ)

O 2 1 0

It is a desirable condition of the roll shape to satisfy the condition.

[0039] In Tables 1 and 2, and in the graphs of Figs. 2 to 6, (a) shows the gorge diameter of the roll D = g

(B) is the case where D = 500 mm. Therefore, the comparison between (a) and (b) is g

The content of the second prior invention disclosed in Patent Document 2 will be discussed. The upper limit of the above inequality (Equation (7)) can be calculated by performing the same calculations as in Tables 1 and 2 with D = 315 mm.

Guided easily.

[0040] In addition, D and D are power tubes which are the inlet diameter and the outlet diameter of the cone-shaped main roll.

1 2

It is assumed that the material enters at the entrance surface of the main roll and leaves the roll at the exit surface.Accordingly, the diameter of the main roll at the position where the billet enters the roll is D.

The main roll diameter at the position where the hollow piece leaves the roll is D.

Two

Finally, the barrel width of the roll will be described. The barrel width L is the sum of L in Fig. 1.

1 2

. Adding an extra length to the barrel width will increase the overall structure of the rolling mill more than necessary. Therefore, the inlet barrel width L should be determined in consideration of the number of finishing reels, as long as the stability of the penetration barrel is not impaired.

Two

The barrel width ratio “L / L” is preferably within the following range.

twenty one

1.0≤L / L ≤2.0

twenty one

Example 1

Using a billet of 18% Cr-8% Ni austenitic stainless steel having a diameter of 60 mm as a test material, a high workability thin-wall piercing and rolling with a pipe expansion ratio of 1.5 was performed using a guide shoe. The billet heat temperature was 1250 ° C. The hot workability of stainless steel is much worse than that of carbon steel. [0043] 1. Role conditions

Crossing angle: _γ = 25 °

Gorge diameter D = 400mm

g

Tilt angle ... 3 = 12 °

Inlet diameter ... D = 240mm

1

Outlet diameter ... D = 550mm

Two

Roll expansion ratio ... D / D = 2.29

twenty one

Inlet barrel width… L = 300mm

1

Outgoing barrel width ... L = 460mm

Two

Norel width… L + L = 760mm

1 2

Balenole width ratio… L / L two 1.53

twenty one

[0044] 2. Punch rolling conditions

Plug diameter… d = 80mm

P

Billet diameter d = 60mm

o

Hollow cylinder diameter ... d = 90mm

Hollow Chenore thickness ... t = 2.7mm

Expansion ratio… d / d = 1.50

0

Perforation rolling ratio… d ² /4t(dt)=3.82

0

"Thickness / outer diameter" ratio ... (t / d) X 100 = 3.0%

Roll shape index ... (d / d) / (D / D) = 0.655

0 2 1

Logarithmic strain in the thickness direction Ψ = ln (2t / d) = 1η009 = — 2.408

r 0

Circumferential logarithmic strain… = ln {2 (d-t) / d} = 1η2 · 91 = 1.068

Θ ο

Reduction ratio… — Ψ / Ψ = 2.255

r Θ

[0045] As described above, since the rolling distribution ratio in the circumferential direction and the thickness direction, that is, the rolling distribution ratio in the longitudinal direction and the circumferential direction was appropriate, piercing and rolling could be performed without generating flare or peeling. did it. Since the roll shape was also optimized, no internal flaws or lamination were observed even in the case of piercing and rolling with a high degree of work and ultra-thin wall of difficult-to-work material. Example 2 [0046] The hot workability of high alloy steel is still worse than that of stainless steel, and lamination is likely to occur when the piercing and rolling temperature exceeds 1275 ° C. Therefore, in this example, a 70% diameter billet of a 25% Cr-35% Ni-3Mo high alloy steel was used as a test material and a disc roll was used. Thin-wall piercing rolling was performed.

[0047] 1. Role conditions

Crossing angle: γ = 30 °

Tilt angle = 12 °

Gouge diameter ... D = 500mm

g

Inlet diameter ... D = 300mm

Outlet diameter ... D = 670mm

Two

Roll expansion ratio ... D / Ό = 2.23

twenty one

Inlet barrel width… L = 300mm

1

Outgoing barrel width ... L = 460mm

Two

Balloon width… L + L = 760mm

1 2

Balenole width ratio… L / L = 1.53

twenty one

[0048] 2. Punch rolling conditions

Plug diameter ... d = 130mm

P

Billet diameter d = 70mm

o

Hollow cylinder diameter ... d = 140mm

Hollow Chenore thickness ... t = 3.5mm

Expansion ratio… d / d = 2.00

0

Perforation rolling ratio: dso 4t (d—) = 2.56

o

"Thickness Z outer diameter" ratio ... (t no d) X 100 = 2.5%

Roll shape index ... (d / d) / (D / D) = 0.897

0 2 1

Logarithmic strain in thickness direction… = ln (2t / d) = 1η010 = — 2.303

r 0

Logarithmic distortion in the circumferential direction Ψ = ln {2 (d—t) / d} = 1η3 · 90 = 1 · 361

θ ο

Reduction ratio… — Ψ / Ψ = 1.692

r θ

[0049] As described above, the rolling reduction in the circumferential direction and the thickness direction is appropriate, and the roll shape is also appropriate. Since it has been optimized, piercing and rolling could be performed without any problems even in high-work thin-wall piercing and rolling of high alloy steel having poor hot workability.

Industrial applicability

[0050] In the piercing and rolling method of the present invention, the relative relationship between the expansion ratio of the tube material and the diameter expansion ratio of the cone-shaped main roll is optimized. Therefore, the rotary forging effect in the piercing and rolling process is significantly suppressed, and the inner surface flaws, which are likely to occur in high-throughput thin-wall piercing and rolling of difficult-to-make materials such as stainless steel and high alloy steel, are more reliably detected. Can be suppressed. According to the method of the present invention, pipe expansion piercing and rolling up to an expansion ratio of 2.0 is possible.

[0051] As described above, the present inventor has proposed a high-crossing angle piercing and rolling method from the viewpoint of reducing the rotational forging effect and suppressing additional shear deformation, and has made several inventions so far. However, high crossover angle is a necessary condition to suppress the rotary forging effect and suppress the additional shear deformation, but is not a sufficient condition. A necessary and sufficient condition is optimization of the roll shape, and a high crossover angle is a necessary condition of the roll shape optimization.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view showing a mode of piercing and rolling.

[Figure 2] Diameter expansion ratio (D / D) and pipe expansion on rotational forging effect (aperture value in micro tensile test)

twenty one

FIG. 3 is a diagram showing the influence of the ratio (dZd).

P

[Figure 3] Expansion ratio (D / Ό) and expansion ratio on applied shear strain (circumferential shear strain)

It is a figure which shows the influence of 21 pipe ratio (d / d).

P

FIG. 4 is a diagram showing a relationship between a diameter expansion ratio (D / D), a pipe expansion ratio (d / d), and a roll inclination angle (γ).

2 1 ρ

is there.

FIG. 5 is a graph showing the relationship between a diameter expansion ratio (D / D), a pipe expansion ratio (d / d), and a roll crossing angle (γ).

2 1 ρ

is there.

[Figure 6] The relationship between the roll shape index, that is, (d / d) / (D / D) and the roll crossing angle (γ)

0 2 1

FIG.

Explanation of reference numerals

[0053] γ: Roll crossing angle

D: Roll inlet diameter D: Roll exit diameter

Two

D: Roll gorge diameter

L: Width of entry side of Lorenole

L: Width of the barrel on the outlet side of Lonore

Two

d: Outer diameter of billet

0

d: Hollow piece outer diameter t: Hollow piece thickness

Claims

The scope of the claims

Maintain the inclination angle β and the crossing angle _の of the cone-type main rolls supported at both ends, which are opposed to each other on the left and right or up and down with the pass line in between, so as to satisfy the following formulas (1) to (3). The relationship between the outer diameter d of the actual billet and the outer diameter d and wall thickness t of the hollow piece after piercing and rolling is given by the following equation.

0

(4), and the main roll inlet diameter D, outlet diameter D, d, d and

A piercing and rolling method in seamless pipe production, wherein 120 and γ satisfy the following expression (5).

8 ° ≤ ≤20 ° '' (1)

5 ° ≤ γ≤35 ° '(2)

15 ° ≤ + γ≤5Ο °

1.5≤-Ψ / Ψ ≤4.5

r θ

(d / d) / (0.75 + 0.025γ) ≤D / Ό '(5)

0 2 1

Where において = ln (2t / d)

r 0

Ψ = ln {2 (d-t) / d}

θ o

It is.

The relationship between the inlet diameter D and outlet diameter D of the main roll and the above d, d and γ is given by the following equation (6)

1 2 0

2. The piercing and rolling method according to claim 1, wherein

D / D ≤ (d / d) / (1.00-0.0277) '' (6)

2 1 0

The piercing and rolling according to claim 1 or 2, wherein the piercing and rolling ratio is 4.0 or more, the pipe expansion ratio is 1.15 or more, or the `` wall thickness / outer diameter ratio '' of the hollow piece is 6.5 or less. Method.