JP2002331301A - Inclined drilling rolling method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inclined drilling rolling method capable of manufacturing a seamless steel tube having less deflective wall thickness and no internal flaw at high rolling efficiency. SOLUTION: In the inclined drilling rolling method using two or more rolls and one plug for drilling, using the roll 10 having No.1 to No.4 or No.1 to No.5 conical portions 11, 12, 13, 14, 15 ranging in order from an end of the roll central shaft 22 direction to the other end as the roll, a material to be rolled 5 is first drilled and rolled with No.1 conical portion and the leading end portion of the plug 2 and next, is loose-rolled with No.2 and No.3 conical portions, and then, is rolled with the whole or a part of No.4 conical portion to reduce the thickness and further, is rolled to widen the diameter with complete roundness with No.5 conical portion or the other part of No.4 conical portion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inclined piercing and rolling method used for manufacturing a seamless steel pipe.

[0002]

2. Description of the Related Art As a method of manufacturing a seamless steel pipe by a rolling method, generally, a Mannesmann pipe mainly having a small diameter is mainly used.
The mandrel mill system and the Mannesmann plug mill system mainly for medium diameter sizes are typical. The dimensional accuracy of the seamless steel pipe is greatly influenced by the setting of rolling conditions in the processes in these methods, the centering of the tool, the management of wear, the uniformity of the material, and the like.

As an example, a piercing process using a piercer is shown in FIGS. A pair of barrel-shaped rolls 1 are arranged left and right or up and down, and a perforating plug 2 is set at an intermediate position of the barrel-shaped rolls. 3 is a guide shoe, 4 is a perforated pipe (hollow, seamless steel pipe), 5 is a raw material (round billet) before perforation, and 6 is a bar for supporting the plug 2. Bar 6
One end is connected to the thrust block 7 side, and the other end supports the plug 2 to form a kind of cantilever. Therefore, the perforating plug 2 tends to be deviated from the center position between the rolls during perforation, and as a result, the wall thickness of the pipe 4 after perforation tends to be uneven (uneven thickness). Although this is an unavoidable phenomenon of the Mannesmann pipe manufacturing method, when the uneven thickness exceeds a predetermined reference value, the pipe material is degraded and the product yield is significantly impaired.

On the other hand, there has been proposed a rolling method called a hollow reducer or an ecorizer, in which a rolling step for the purpose of straightening the wall thickness is added in a step subsequent to the drilling step (for example, Japanese Patent Laid-Open No. 57-68207). Gazette). Although this method plays a role in improving the dimensional accuracy, there is a disadvantage due to an increase in the number of steps as compared with the conventional pipe making step. On the other hand, a rolling method in which a rolling step corresponding to the hollow reducer or the like is provided in one inclined rolling mill has been known for a long time. For example, on page 128 of the plastic working of a book (Hiroshi Suzuki, published by Shokabo, July 1961), a roll-expanding section is continuously provided on the exit side of a barrel-shaped roll as one of the Mannesmann-type punching methods. Further, it is described that there is a pipe-making system in which the outer diameter is reduced by the roll enlarged portion following the piercing and rolling by the barrel-shaped roll and the plug. Japanese Patent Publication No. Sho 61-2444 and Japanese Patent Laid-Open Publication No. Sho 61-67511 also propose a similar inclined rolling method. These are intended to reduce the uneven thickness by preferentially increasing the thickness of the thin portion by performing the bulging reduction by the roll enlarged portion in the latter half of the inclined rolling.

[0005]

However, in the method of reducing the diameter of the bulging in the latter half of the inclined rolling as described above, the effect of reducing the thickness deviation is not always sufficient, and there is much room for improvement. In addition, there is also a problem that an inner surface flaw is apt to occur during the process of reducing the diameter of the bulging pad. Also, since the inner diameter of the pipe after rolling becomes smaller than the diameter of the plug, the plug is removed from the bar (or the bar is removed from the thrust block) and the pipe is separated from the bar and the plug (or bar) is set again each time rolling is performed. Therefore, there is a problem that the rolling efficiency does not increase.

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the prior art and to provide an inclined piercing and rolling method capable of producing a seamless steel pipe having a small uneven thickness and no inner surface flaw at a high rolling efficiency.

[0007]

Means for Solving the Problems The present inventors diligently studied to achieve the above object, and as a result, two or more rolls of a specific shape inclined and arranged and perforations arranged between the rolls After piercing and rolling the round billet at the roll entry side and the plug tip using a plug, the hollow is temporarily removed from the plug and emptied, and then reduced at the roll middle and the plug rear end. After the meat rolling, by performing the diameter expansion rolling at the roll exit side, a seamless steel pipe with a significantly reduced wall thickness is obtained, and the obtained seamless steel pipe has no internal surface flaws and remains plugged. In addition, the present invention has been found that it can be easily extracted from the mandrel bar as it is set in the thrust block, and that the same effect can be more easily obtained by arranging the rolls crosswise. Made.

(1) In the oblique piercing and rolling method using two or more rolls and one piercing plug, the first to fourth or first rolls are successively connected from one end to the other end in the roll center axis direction as the rolls. Using a roll having a fifth to a fifth conical portion, the material to be rolled is first pierced and rolled at the first conical portion and the tip end portion of the plug, and then the second to the third conical portion is subjected to blanking rolling, and then the The thickness reduction rolling is performed on all or a part of the conical portion of No. 4 and the rear end portion of the plug, and the diameter of the conical portion is further expanded and rounded on another portion of the fifth conical portion or the fourth conical portion. Inclined piercing and rolling method.

(2) The inclined piercing and rolling method according to (1), wherein the roll is used at an intersection angle of 0 to 30 °. (3) The roll sets the surface angles α1, α2, α3, α4 of the first, second, third, and fourth conical portions to 0 ° ≦ α1 ≦ 10 °,
α2 ≦ 15 °, α3 ≧ 0 °, α4 ≧ 0 °, and α1 + α2
≧ 2 ° and α2 + α3 ≧ 3 ° and 2 ° ≦ α3 + α4
The inclined piercing and rolling method according to (1) or (2), wherein ≦ 30 ° is used.

(4) The inclined piercing and rolling method according to any one of (1) to (3), wherein the roll is used at an inclination angle of 5 to 25 °. In the present invention, the conical portion means a truncated cone-shaped portion obtained by cutting the cone at two points in the center axis direction.
The inclination angle (symbol β) means that a line segment OA overlapping the roll center axis is rotated as a rotation center axis 21 by a perpendicular drawn from the point O to the rolling pass center axis 20, and the point A is defined as the rolling pass center axis. 20
And the rotation angle ∠AOA 'until it coincides with the point A ′ in the plane defined by the rotation center axis 21 and the intersection angle (symbol γ).
Is a line segment O drawn from the point O in parallel to the rolling pass central axis 20.
The angle ∠A′OB between B and the line segment OA ′ is (FIG. 4).

[0011]

FIG. 1 is a partially cutaway side view showing one embodiment of the present invention. In this embodiment, the inclined piercing rolling is performed with two inclined rolling rolls and one plug, but the present invention can also be applied to a case where three or more inclined rolling rolls are used. In the embodiment of FIG. 1, a guide shoe is used as in the conventional case, but the illustration is omitted.

In the present invention, as the roll for inclined rolling, a roll having first to fourth conical portions successively arranged from one end to the other end in the direction of the roll central axis 22 or the first to fourth conical portions as shown in FIG. Since the roll 10 having the five conical portions 11, 12, 13, 14, and 15 is used, the following four-stage rolling can be continuously performed. First stage: piercing and rolling by the first conical portion 11 and the tip end portion of the plug 2 Second stage: empty rolling by the second to third conical portions 12 to 13 Third stage: of the fourth conical portion 14 Wall thinning rolling with all (FIG. 1 shows this case) or part and the rear end of plug 2 Fourth stage: Fifth conical portion 15 (FIG. 1 shows this case) or fourth conical portion According to the four-stage rolling, the hollow 4 formed by the first-stage piercing-rolling corrects the uneven thickness to some extent by the second-stage blank-rolling. Then, the wall thickness is finally adjusted by the third-stage thickness reduction rolling, and the outer diameter is finally adjusted by the fourth-stage diameter expansion rounding rolling. Furthermore, the plug 2
It is constrained at two points, a front end portion and a rear end portion, and has a greater resistance to misalignment than in the related art where the constrained portion is only the front end portion. For these reasons, uneven thickness of the final product can be significantly reduced.

When the roll used for rolling does not have the first to fourth or first to fifth conical portions, it is difficult to obtain the second-stage bulging rolling state, and the effect of reducing uneven thickness is poor. . Further, if the rolls are arranged in a crossed manner as described above, the above-mentioned effect can be more easily obtained, but the crossed angle γ
Is too large, the difference in rolling speed between the leading rolling portion and the trailing rolling portion becomes large, and the drilling speed cannot follow the rolling speed and stops drilling. Therefore, the crossing angle is preferably in the range of 0 to 30 °. .

Further, since the third step is reduced-thickness rolling, the inner surface wrinkles caused by the second-step blank-diameter reduction rolling are smoothed. In addition, the diameter of the product pipe becomes larger than the maximum diameter of the plug by the fourth stage of rounding and rounding rolling, and the product pipe can be pulled out to the plug tip side. And the rolling efficiency is improved.

In the present invention, the first,
Surface angles α1, α2, α3, α of the second, third, and fourth conical portions
4 is 0 ° ≦ α1 ≦ 10 °, α2 ≦ 15 °, α3 ≧ 0 °, α
4 ≧ 0 °, α1 + α2 ≧ 2 °, and α2 + α3 ≧ 3
It is preferable that the rolls are arranged and rolled so that the angle satisfies 2 ° ≦ α3 + α4 ≦ 30 °. Here, the surface angle of each conical portion refers to the roll surface of each conical portion in a state where the roll is arranged on the rolling line and an axis 20A parallel to the central axis of the rolling path.
(See FIG. 5).

0 ° ≦ α1 ≦ 10 ° When α1 is a negative value, it is difficult to make full use of the Mannesmann effect, and the life of the plug is shortened. On the other hand, when it exceeds 10 °, billet biting failures occur frequently.・ Α2 ≦ 15 ° When α2 exceeds 15 °, the diameter expansion at the second conical portion progresses too rapidly, and breakage easily occurs.

Α1 + α2 ≧ 2 ° When α1 + α2 is less than 2 °, the effect of correcting the thickness deviation by the blank-rolling in the second and third conical portions cannot be sufficiently obtained. Α3 ≧ 0 ° If α3 is less than 0 °, the plug diameter at this portion becomes too small to sufficiently obtain the effect of correcting the uneven thickness by the bulging rolling at the second and third conical portions, which is suitable for plug design. Not.

Α2 + α3 ≧ 3 ° If α2 + α3 is less than 3 °, the roll body length becomes too long in order to sufficiently obtain the effect of correcting the thickness deviation by the empty-rolling rolling in the second and third conical portions, and from the viewpoint of equipment. Is also not appropriate. -Α4 ≧ 0 ° If α4 is less than 0 °, the thickness reduction rolling and the diameter reduction rolling proceed simultaneously, so that the material flow is braked and the dimensional accuracy is deteriorated due to flaws and twists.

2 ° ≦ α3 + α4 ≦ 30 ° When α3 + α4 is less than 2 °, the plug diameter in the thickness reduction rolling at the fourth conical portion becomes too small, which is not suitable for plug design. If α3 + α4 exceeds 30 °, the change in the outer diameter in the thickness-reduced rolling section is too rapid, and the rolling becomes unstable, and the restraining force of the plug is hardly obtained.

In the present invention, the roll has an inclination angle β = 5.
It is preferable to use 25 °. If the inclination angle β is less than 5 °, the advancing speed of the material to be rolled is slow, and there is a problem in terms of the generation of inner surface flaws due to Mannesmann cracking and the butt-removing property. Because there is.
When the intersection angle γ is given (γ> 0 °), the fifth conical portion is also used as an extension of the fourth conical portion, that is, the fifth conical portion is omitted and the fourth conical portion is omitted. It is also possible to perform wall-thinning rolling in a part of the part (the part on the entry side of the material to be rolled), and to perform diameter-expanding rounding rolling in the other part (part on the exit side of the material to be rolled).

[0021]

EXAMPLE (Case 1) A round billet (diameter 170 mm) of martensitic 13% Cr steel was heated to 1200 ° C., and two rolls having the dimensions and shapes shown in FIG. And the roll inclination angle β and the cross angle γ were set to the values shown in Table 1, and the rolls were inclined and pierced and rolled while being guided by the guide shoes to obtain hollows having the wall thickness and outer diameter shown in Table 1. The rotation speed of the roll was 90 rpm.

The obtained hollows were examined for uneven thickness and inner surface flaws. The uneven thickness was evaluated from the thickness data measured at 32 equal points in the circumferential direction of the hollow section by the following formula: (maximum value−minimum value) / average value (× 100%). The inner surface flaw was evaluated by visually observing the inner surface by dividing a hollow portion of 1 m length vertically, and evaluating the presence or absence of the flaw. Table 1 shows the results.

[0023]

[Table 1]

In the present invention, in which the above-described four-stage rolling is performed using the rolls having the first to fifth conical portions, the thickness deviation rate is much smaller than that of the comparative example. No inner surface flaw was generated in both the present invention example and the comparative example because the bulging reduction was not performed in the latter half of the roll. The hollow inner diameter of each of the present invention example and the comparative example was larger than the plug diameter, and the hollow was easily pulled out from the bar in the set state. This was about 10% of the case where plugs or bars had to be attached and removed for each one.

(Case 2) A round billet (diameter 60 mm) of carbon steel equivalent to JIS STKM13 was heated to 1150 ° C., and then, two rolls having the dimensions and shapes shown in FIG. Table 2 shows the roll inclination and crossing angles.
, And inclined piercing and rolling while guiding with a guide shoe to obtain hollows having the wall thickness and outer diameter shown in Table 2. The rotation speed of the roll was 90 rpm.

The obtained hollow was examined for uneven thickness and inner surface flaws in the same manner as in Case 1. Table 2 shows the results.

[0027]

[Table 2]

In the example of the present invention in which the four-stage rolling is performed using a roll having the first to fifth (or fourth) conical portions, the wall thickness deviation rate is much smaller than that of the comparative example. No inner surface flaw was generated in both the present invention example and the comparative example because the bulging reduction was not performed in the latter half of the roll. The hollow inner diameter of each of the present invention example and the comparative example was larger than the plug diameter, and the hollow was easily pulled out from the bar in the set state. This was about 10% of the case where plugs or bars had to be attached and removed for each one.

[0029]

According to the present invention, there is an excellent effect that a seamless steel pipe having a sufficiently small uneven thickness and no inner surface flaw can be manufactured with high rolling efficiency.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view showing one embodiment of the present invention.

FIG. 2 is a side view showing one example of a conventional inclined piercing and rolling method.

FIG. 3 is a view taken in the direction of arrows AA in FIG. 2;

FIG. 4 is an explanatory diagram of definitions of a tilt angle and a cross angle.

FIG. 5 is an explanatory diagram of definitions of roll dimensions.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Barrel roll 2 Plug 3 Guide shoe 4 Pipe (hollow, seamless steel pipe) 5 Material (round billet) 6 Bar 7 Thrust block 10 Roll 11, 12, 13, 14, 15 First, Second, Third, Third 4. Fifth conical part 20 Rolling path center axis 20A Axis parallel to rolling path center axis 21 Rotation center axis 22 Roll center axis

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takanori Tamari 1-1 1-1 Kawasaki-cho, Handa-shi, Aichi F-term in the Chita Works of Kawasaki Steel Corporation (reference) 4E016 AA09 BA09 DA07 DA19

Claims (4)

[Claims] In the inclined piercing and rolling method using two or more rolls and one piercing plug, the first to fourth or the first to fourth or first to fourth rolls are sequentially connected from one end to the other end in the roll central axis direction as the rolls. Using a roll having a fifth conical portion, the material to be rolled is first pierced and rolled at the first conical portion and the tip end portion of the plug, and then subjected to vacancy rolling at the second to third conical portions and then to the fourth conical portion. Characterized in that wall thinning rolling is performed on all or a part of the conical portion and the rear end portion of the plug, and further, the other portion of the fifth conical portion or the fourth conical portion is subjected to diameter expansion rounding rolling. Punch rolling method. 2. The inclined piercing and rolling method according to claim 1, wherein the roll is used at an intersection angle of 0 to 30 °. 3. The roll comprises a first, second, third, and fourth rolls.
The surface angles α1, α2, α3, and α4 of the conical part of 0 ° ≦ α1
≦ 10 °, α2 ≦ 15 °, α3 ≧ 0 °, α4 ≧ 0 °, and α
1 + α2 ≧ 2 ° and α2 + α3 ≧ 3 ° and 2 ° ≦ α
The inclined piercing and rolling method according to claim 1 or 2, wherein 3 + α4 ≤ 30 ° is used. 4. The inclined piercing and rolling method according to claim 1, wherein the roll is used at an inclination angle of 5 to 25 °.