JP2001353520A - Forming method of square steel pipe - Google Patents

Abstract

(57) [Summary] [PROBLEMS] When using an existing seamless rolling equipment and performing processing with a pair of rolls (hereinafter referred to as two rolls), a square-shaped steel pipe having a large section with a side length of 250 mm or more is manufactured. We propose a suitable processing method. SOLUTION: In forming a seamless base tube having a circular cross section into a square steel pipe by a pair of rolls having a die, a bottom of the die is cut in parallel with a roll axis to form a square steel pipe. A method of forming a square steel pipe, wherein the rolling direction is such that the direction of the side of the roll is parallel to the roll axis direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a square steel pipe, particularly a square steel pipe suitable for use in building structures such as pipe columns.

[0002]

2. Description of the Related Art Generally, square steel pipes (hereinafter simply referred to as square steel pipes) are being widely used as pillars for steel structures of buildings. The manufacture of this square steel pipe is a so-called roll column in which an electric resistance welded pipe is cold or hot formed by a roll, a so-called press column in which a steel sheet is pressed and welded in a U-shape, and a so-called press column in which a seamless steel pipe is hot formed. Seamless columns (seamless rectangular steel pipes) and the like are known. At present, most of them are roll columns and press columns, but recently, so-called seamless columns obtained by hot forming seamless steel pipes have been manufactured.

Conventionally, as a method of manufacturing this seamless column, for example, a three-roll system as disclosed in JP-A-4-41006 and a two-roll system as disclosed in JP-A-11-57820 are known.

[0004] In the latter two-roll system, a heated circular tube is gradually formed into a square shape by a roll, and finally a pair of upper and lower members are arranged on a rear stand as shown in FIG. It is formed into a square rectangular steel pipe 3 by a lower roll 1 and an upper roll 2 having a hole shape. That is, a V-shaped hole 4 is engraved on each roll, and the square steel pipe 3 is rolled by a pair of rolls with one diagonal axis (hereinafter, diagonal rolling) parallel to the roll axis. You.

[0005] The production of square steel pipes by the seamless column method is usually performed by using a seamless rolling facility having a circular cross section without having a dedicated rolling facility. However, since the existing seamless rolling existing in Japan is generally a 16-inch mill, a roll of a sizer mill for forming a square steel pipe located behind the same is at most about 500 mm in width and about 700 mm in diameter.

[0006] Therefore, the existing seamless rolling equipment,
In addition, when diagonal rolling is performed by the two-roll method, there are the following problems.

That is, when the diagonal axis is parallel to the roll axis, the roll radius 5: D / 2 is usually about A from the viewpoint of roll strength.
/ 2 ^0.5 + αA (where A: column side length corrected for heat shrinkage, α: coefficient determined by material).

Here, when A = 350 mm and α is 0.5, the roll diameter D needs to be about 845 mm. The roll width W is also about 2 × A / 2 ^0.5 from the roll strength surface.
+ C (where C: roll flange width) is required. If the roll flange width C is 100 mm, about 595 mm is required.

[0009] Therefore, the roll shape becomes extremely large, and in the above-mentioned existing seamless rolling equipment, 28 rolls are required.
At present, it is impossible to substantially form a rectangular steel pipe having a side length of 0 mm or more without remodeling expensive equipment. Therefore, until now, with existing seamless rolling equipment,
There is no example of manufacturing a square steel pipe with a side length of 250 mm or more,
Such a large-sized square steel pipe has been used in the other processing column method described above.

[0010] However, it is inevitable that large square steel pipes by the seamless column method will be increasingly required in the future.
Further, it is preferable that the diameter and width of the roll be more compact even if the size is smaller than the large-sized steel pipe described above.

[0011]

SUMMARY OF THE INVENTION In view of the above, according to the present invention, when forming a seamless column (square steel pipe), the existing seamless rolling equipment is used and a pair of rolls (hereinafter referred to as two rolls) are used. In this case, a processing method particularly suitable for producing a square steel pipe having a large cross section having a side length of 250 mm or more is proposed.

That is, the molding equipment is made compact,
The first object of the present invention is to minimize forming rolls, and in the case where a square steel pipe is manufactured using an existing seamless rolling facility equipped with a two-roll forming facility, a square shape having a large side length is used as much as possible. The second object is to manufacture a steel pipe, and when a square steel pipe is processed (sizer) with two rolls, unlike a normal four-roll processing method, the material is bitten from a roll flange portion. The third object is to propose a roll caliber shape for preventing this biting, since the biting occurs.

[0013]

Means for Solving the Problems The present inventor, when forming a rectangular steel pipe with a pair of rolls (two rolls), rolls in such a posture that a pair of sides of the rectangular steel pipe are parallel to the roll axis. Then, it was found that the forming roll can be minimized, a square steel pipe having a side length of 250 mm or more can be manufactured with the existing rolling equipment, and that the material can be prevented from being caught from the roll flange portion during rolling. The present invention has been completed.

Thus, the gist of the present invention is as follows.
It is as shown below.

(1) When a seamless base tube having a circular cross section is formed into a square steel pipe by a pair of rolls provided with a die, the bottom of the die is cut in parallel with the roll axis to form a square. A method for forming a square steel pipe, wherein the rolling posture is such that the direction of the side of the steel pipe is parallel to the roll axis direction.

(2) When a seamless tube having a circular cross section is formed into a large-section square steel tube having a side length of 250 mm or more by a pair of rolls provided with a die,
A method for forming a rectangular steel pipe, characterized in that a bottom of the die is cut in parallel with a roll axis and a rolling posture is set so that a direction of a side of the rectangular steel pipe is parallel to a roll axis direction.

(3) Rolling is performed such that the deformation amount in the bottom direction (Y-axis direction) of the groove is increased and the deformation amount in the roll flange portion direction (X-axis direction) is reduced. The method for forming a square steel pipe according to (1) or (2).

(4) At least at the final stand, rolling is performed such that the roll is not deformed in the roll flange portion direction (X-axis direction) even if it is deformed in the bottom direction (Y-axis direction) of the die. The method for forming a square steel pipe according to any one of (1) to (3).

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described with reference to embodiments shown in the drawings.

FIG. 2 is a view showing an example in which a square square steel pipe 3 is formed by a lower roll 1 and an upper roll 2 having a pair of upper and lower holes.

In FIG. 2, a U-shaped hole 6 is formed in each of the lower roll 1 and the upper roll 2, and the bottom 7 of the hole is parallel to the roll axis RR. For this reason, a pair of sides of the square steel pipe 3 are rolled in a posture parallel to the roll axis RR. The technical meaning of "parallel" means a range in which the bending is allowable because the rolling balance is lost and the rectangular steel pipe bends when rolling in a posture inclined at a certain value or more.

When the present invention is applied with the same specifications as the conventional diagonal rolling method shown in FIG. 1, the roll radius is D / 2.
Requires about A / 2 + βA from the viewpoint of roll strength (however, A: square steel pipe side length corrected for heat shrinkage, β: coefficient determined by material). Here, if A = 350 mm and β is 0.5, the roll diameter D is 700 mm. In addition, the roll width W is also approximately A + C (where C is the roll flange width) from the roll strength surface. Therefore, if the roll flange width C is 100 mm, the roll width W is 450 mm.

That is, when a rectangular steel pipe having a side length of 350 mm is manufactured by the conventional method, an extremely large roll having a roll width of 595 mm and a roll diameter of 845 mm is required, whereas the present invention shown in FIG. In order to manufacture a square steel pipe under the same conditions, roll width: 450 mm, roll diameter 7
It can be handled with a small roll of 00 mm.

On the other hand, a two-roll sizer of an existing seamless rolling equipment having the same roll width of 500 mm and a roll diameter of 700 mm can handle only the MAX side length of 280 mm in the conventional method.
Can be molded up to.

By the way, in the two-roll rolling of the present invention, for example, as described in Japanese Patent No. 2888986, the amount of drawing per one step is small, and the roll hole die is brought into contact with the entire peripheral surface of the steel pipe without any gap. When caliber design is performed using the same concept as the roll method,
Very little metal metal is attracted, causing bite. This is particularly noticeable on the final stand and the stand before the final stand.

For example, forming a square steel pipe is disclosed in Japanese Patent No. 288/288.
It is molded with a four-roll caliber as in No. 29886, and the caliber shape is determined as follows.

That is, in FIG. 3, the diameter of the mother pipe 8 (D
_in ) and the final shape side length (H) of the square steel pipe 3, the required X-axis and Y-axis deformation ω is ω = (D _in / 2−H / 2), and is shared by two or more stands. It is molded. By its division, deformation amount [delta] _n of n stand is determined.

Further, as shown in FIG. 4, in the four-roll rolling, since the square steel pipe is symmetrical in the vertical and horizontal directions and in the 45 ° direction, it is composed of eight identical caliber-shaped portions.

Specifically, the caliber-shaped arc X _n (A _n ,
B _n ) is on the axis 45 degrees from the origin (A _n , B _n )
If they are folded back, they overlap with the arc Y _n (A _n , B _n ). Similarly,
The caliber shape overlaps even when it is folded back on the X axis and the Y axis. Thus, point Y _n on the Y-axis of the caliber shape is determined by the deformation amount δn of n stand, the X-axis like a point X _n and equidistant Caliber shape. That is, X _n = Y _n .

The total deformation of 45 degree direction of the roll caliber is ^{_{(D in / 2 0.5 -H /}} 2), the division of each stand, the deformation amount [delta] _{n45 degree} n stand is determined. Therefore, a point (A _n ,
B _n ) is determined. Then, the caliber shapes Y _n and (A
_n , _Bn ) are smoothly connected by a straight line, an arc or an approximate curve. In this way, the former caliber shape 9 and the caliber shape 10 are determined.

However, in the case of forming a square steel pipe by two-roll rolling as in the present invention, if a caliber design is made based on the same concept, the pipe is formed to bite out of the flange portion.

This will be described in detail with reference to FIG.
In roll rolling, the deformation on the X axis is to move the point of X _{n-1 to} the point of X _n , and this deformation is performed by rotating the roll about the point G to convert X _n-1 to X _n . Is to move to a point.

On the other hand, in the two-roll rolling shown in FIG.
Nearest roll flange portion F to X _n point is to move the J point to X _n point closer roll rotation where the point E and the axis,
Due to this movement, no force acts to move the X _n-1 point to the X _n point. That is, the point X _n-1 from the point J of the material entering the n-th stand is deformed to the outside of the point F of the roll flange, and starts to bite.

Since the rectangular steel pipe is symmetrical in the vertical and horizontal directions, the four rolls uniformly deform both the X axis and the Y axis. However, in the case of two rolls, the fact that the bottom of the roll groove is alternately rolled up and down and left and right is utilized to increase the amount of deformation in the direction of the bottom of the groove (the Y-axis direction in the figure), which is the bottom of the groove. If the amount of deformation in the part direction (the X-axis direction in the drawing) is reduced, the roll flange can be prevented or suppressed from biting.

In particular, in the final stand, the roll surface of the flange portion (portion F in the figure) is perpendicular to the axis (θ in the figure).
Therefore, it is preferable to set (X _n−1 −X _n ) to 0. That is, it is preferable that even if the roll flange is deformed in the bottom direction (Y-axis direction), it is not deformed in the roll flange portion (X-axis direction). Here, X _n-1 is the X-axis direction roll caliber distance in the front caliber shape 9 in the front stand,
X _n means the X-axis direction roll caliber distance in the caliber shape 10 at the stand.

On the other hand, at the stand on the upstream side, the angle θ between the roll surface of the flange and the shaft becomes small, and the deformation direction can be called.

Specifically, as shown in the vector analysis diagram at the time of rolling in the two-roll method in FIG. 6, at the point where the roll flange F contacts the incoming material, the roll is rotated from J to K in the direction of K. A vector JK results. Vector JK
Are the tangent line J at an angle α 'with respect to the X axis in the L direction and the vertical vector JM from J in the M direction.
Is decomposed into If the _Xn-1 point can be transformed into the _Xn point without contacting the roll by this vector JM, the roll flange can be formed without being bitten. Therefore, the upstream stand has X _n-1 −X _n ≧
It may be set to 0. A specific roll caliber shape will be described.

3 for manufacturing a 300 mm square steel pipe
Table 1 shows the roll caliber shape of the four-roll rolling of the stand.

[0039]

[Table 1]

Table 2 shows the roll caliber shapes of the two rolls of the five stands of the present invention for manufacturing a 300 mm square steel pipe (roller calibers are alternately shifted by 90 degrees).

[0041]

[Table 2]

As is clear from comparison between Tables 1 and 2, in the two-roll rolling according to the present invention, it is possible to manufacture a 300 mm square steel pipe using rolls having almost the same size as the conventional four-roll rolling. Has become.

[0043]

The method for forming a square steel pipe according to the present invention has the following remarkable effects. In the case of square steel pipes having the same size (side length), the size of the roll itself is small, which is advantageous in terms of roll cost, and the whole forming equipment is also compact. When utilizing the existing seamless rolling equipment, it is possible to form a larger square steel pipe.

[Brief description of the drawings]

FIG. 1 is a view showing a conventional method for forming a two-roll rolling type seamless column.

FIG. 2 is a view showing a method of forming a seamless column of a two-roll rolling system according to the present invention.

FIG. 3 is a diagram for explaining an amount of deformation when a mother pipe is formed into a square steel pipe.

FIG. 4 is a diagram for explaining a caliber design in a four-roll rolling method.

FIG. 5 is a diagram for explaining prevention or suppression of biting at a roll flange portion in a two-roll rolling method.

FIG. 6 is a vector analysis diagram at the time of rolling in a two-roll system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Lower roll 2 Upper roll 3 Square steel pipe 4 V-shaped hole 5 Roll radius (D / 2) 6 C-shaped hole 7 Bottom 8 Mother pipe 9 Front caliber shape 10 Rear caliber shape RR roll Shaft A Square steel pipe side length W Roll width ω Deformation D _in Mother pipe diameter H Final shape side length

Claims (4)

[Claims] In forming a seamless base tube having a circular cross section into a square steel pipe with a pair of rolls provided with a die, a bottom of the die is cut in parallel with a roll axis to form a square die. A method for forming a square steel pipe, wherein a rolling posture is such that a direction of a side of the steel pipe and a roll axis direction are parallel to each other. 2. A seamless base tube having a circular cross section is formed by a pair of rolls having engraved dies having a side length of 250 mm.
When forming into a square steel pipe having a large cross section of at least mm, the bottom of the die is cut in parallel with the roll axis, and the rolling posture is such that the direction of the side of the square steel pipe and the roll axis direction are parallel. Forming a square steel pipe. 3. Rolling is performed so as to increase the amount of deformation of the groove in the bottom direction (Y-axis direction) and to reduce the amount of deformation in the roll flange portion direction (X-axis direction). 3. The method for forming a square steel pipe according to 1 or 2. 4. At least at the final stand, rolling is performed such that even when deformed in the bottom direction (Y-axis direction) of the die, it is not deformed in the roll flange portion direction (X-axis direction). The method for forming a square steel pipe according to any one of claims 1 to 3.