JPH08117840A - Production of thick square steel pipe for connection - Google Patents

Abstract

PURPOSE: To easily obtain a connection steel pipe which is thick and is small in the radius of curvature in corner parts at a low cost by heating a thick steel pipe to a recrystallization temp. or above, arranging dies in four directions perpendicular to each other of its outer peripheral surface and simultaneously moving the dies toward the pipe axis from four directions, then extruding the pipe. CONSTITUTION: Four pieces of the dies 53 are arranged perpendicular to each other. A work P is heated to the recrystallization temp. or above and is arranged at the center of four pieces of the dies 53. The dies 53 are moved simultaneously from the four directions toward the pipe axis of the work P. The movement stops in the contacting state of the chamfered parts of the dies 53 and the molding is completed. Large compressive force acts on the work P from the respective sides toward the corner parts and, therefore, the corner parts are formed thick and simultaneously, the corner parts bulge outside, thereby forming a sharp sectional shape of a small radius of curvature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thick-walled square steel pipe used for a joint portion of a steel structure for construction.

[0002]

2. Description of the Related Art As a metal used for a connecting portion of a steel structure for construction, it is called a "dice" in which a flat diaphragm is attached to the upper and lower surfaces of a square steel pipe having substantially the same cross section as the upper and lower pillars. Things are common. This will be described with reference to FIG. This figure is a perspective view of a column-beam connection portion, where 1 is a column member, 2 is a fitting metal part, and 3 is a beam member.

The fitting part 2 has flat diaphragms 21 attached to the upper and lower sides of a short pipe 22 made of a square steel pipe having the same cross-section as the column member 1. The diaphragms 21 are spaced apart from each other by the flanges 31 of the beam member 3. First, the flanges of the upper and lower pillars are supported.
11. The web 12 is completely melted and welded to the surface of the diaphragm 21, and then the flange 31 of the beam 3 is the edge of the diaphragm 21, and the web 32 of the beam 3 is the short pipe 22 of the joint part metal fitting 2.
Each is completely melted and welded.

As described above, since all the joints are completely melted and welded, not only the welding amount becomes large but also
Since it is necessary to correct the welding distortion and the cost increases, improvement has been desired. Therefore, an attempt has been made to omit the diaphragm by increasing the wall thickness to about twice the normal thickness, although the outer dimensions are almost the same as the pillar material.

Conventionally, such a thick-walled square steel pipe is manufactured by the following method, for example. 1) Cold forming method (1 seam method) The steel strip is cold-worked by passing through many pairs of forming rolls and gradually deformed into a rectangular closed cross section.
As shown in (a), the mating surfaces are butt-welded to form a square steel pipe. It is, so to speak, the same as the method for manufacturing an electric resistance welded pipe having a circular cross section, but since the amount of plastic deformation is large, cracks are likely to occur at the corners, and a thick wall cannot be manufactured. 2) Cold forming method (2 seam method) A steel strip or flat plate is bent into a shallow U-shaped cross section by pressing or forming rolls, and as shown in Fig. 11 (b), butt welding of two joint surfaces is performed. And make a square steel pipe.

In Japanese Patent Laid-Open No. 5-331968, a steel plate having a thickness of 16 mm or more is clamped between a female mold and a male mold at a temperature of 500 ° C. or more, and the outer radius of the bent portion is 4 mm of the steel plate thickness. It is described that a square steel pipe is formed by forming a U-shaped cross section that is equal to or less than double and forming a pair to form a pair. FIG. 12 is a vertical sectional view showing an initial stage of the process, in which 91 is a female mold, 92 is a male mold, 93 is a guide roll, and P is a blank plate. 3) Welding assembly method (4 seam box method) As shown in Fig. 11 (c), four steel plates are assembled into a box-shaped cross section to form a square steel pipe by welding and joining the four joints.

In the above methods 1) to 3), if the square steel pipe is manufactured to have an appropriate length and is cut into a predetermined size as the metal fitting for the connection part, the angle at the time of cutting is controlled. Therefore, it is convenient that the accuracy of parallelism and squareness of the upper and lower surfaces can be obtained. However, in each case, the proportion of welding work is high and there is a problem in technical control, and particularly in the case of the methods 1) and 2), different molds are required depending on the size of the short pipe to be obtained.

On the other hand, Japanese Unexamined Patent Publication No. 3-234315 discloses a manufacturing method of a square steel pipe different from the above. FIG.
(A) is a plan view showing a state before molding, (b) is its AA
Sectional view, FIG. 14 (a) is a plan view showing a state after molding,
(B) is the BB sectional view. As shown in FIG. 13, a tube-expanding piece 96 having a shape obtained by dividing a rectangular body into two is inserted inside a short tube P having a circular cross section placed on a base 95, and an outer mold is provided on the outside.
By placing 98 and driving the wedge 97 into the tube expansion piece 96 to open it in the left-right direction, and simultaneously pressing the outer mold 98 in the front-back direction, the short tube P is formed into a rectangular cross section as shown in FIG.

This method is good in that it does not require welding, but since it is a cold forming process, it is not possible to manufacture a product having an excessively large wall thickness. Also, the point that different molds are required for each dimension of the short pipe is similar to the above method.

[0010]

SUMMARY OF THE INVENTION The present invention solves these problems and provides a method for producing a thick-walled square steel pipe for a connection, which involves forming a thick-walled steel pipe into a rectangular cross section without a welding process. The purpose is to

[0011]

The present invention according to claim 1 heats a thick-walled steel pipe to a recrystallization temperature or higher and arranges the molds in four directions on the outer peripheral surface thereof at right angles to each other. Is simultaneously moved from four directions toward the pipe axis and pressed to form the thick-walled steel pipe into a rectangular cross section.

Further, according to the present invention as set forth in claim 2, a thick-walled steel pipe heated to a recrystallization temperature or higher is placed in a vertical position on a bottom plate of a rectangular form, and the outer peripheral surfaces of the thick steel pipe are placed at right angles to each other. Direction, an inner die which has a sloped surface on the back surface and is movable in the horizontal direction is arranged, and an outer die having four sloped surfaces that engage with the sloped surface is used as the mold and the inner die. The thick-walled steel pipe is shaped into a rectangular cross section by inserting the thick-walled steel pipe into a rectangular cross-section, and manufacturing the thick-walled steel pipe for connection.

Further, the present invention according to claim 3 is the thick-walled square steel pipe manufactured by the manufacturing method according to claim 1 or 2.
A method for manufacturing a thick-walled square steel pipe for a connection, which is characterized by cutting into a predetermined size.

[0014]

[Operation] In the present invention, a circular cross-section steel pipe or a square steel pipe having a circumference slightly longer than that of the square steel pipe to be manufactured is used as a raw material, and the raw material is heated to a recrystallization temperature, that is, a high temperature of 500 ° C or more. 4 on the outer peripheral surface
From the direction, simultaneously move and press the mold toward the tube axis to form a rectangular cross section.

At the time of forming, a large compressive force is applied to the raw material steel pipe from each side portion to the corner portion, so that the corner portion becomes thick and at the same time the corner portion protrudes outward, and the sharp radius of curvature is small. The cross-sectional shape will be different. Further, in the method of the present invention,
By adjusting the stroke at the time of pushing with a press or the like, one wedge-shaped mold can be used for manufacturing square steel pipes having a plurality of dimensions.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a sectional view seen from the front side showing a state before molding, and FIG.
Is a top plate, 52 is an outer mold, 53 is an inner mold, 54 is a form, 55 is a bottom plate, and P is a processed material.

The processed material P is a thick-walled steel pipe having a slightly longer circumference than the square steel pipe to be manufactured and having a length equal to or less than the length of the inner die 53 described later. This steel pipe is heated to a recrystallization temperature, that is, a high temperature of 500 ° C. or higher, for example, about 1000 ° C., and placed in the center of the bottom plate 55 in the mold 54. The mold frame 54 is constructed by assembling a thick steel plate into a rectangular cross section, appropriately attaching a reinforcing member or the like to the outside so as not to be deformed by a reaction force, and attaching a bottom plate 55 to the lower part.

Between the processed material P and the four sides of the mold 54, four inner molds 53 are placed so that their inner surfaces are in contact with the processed material P, and the gap between the back surface and the four sides of the mold 54. Then, the outer mold 52 attached to the top plate 51 is inserted. Here, inner mold 53 and outer mold 52
And a pair of wedges having the same sloped surface on one side, for example, a slope of 1/6. In this state, when the top plate 51 is pushed downward by a processing machine such as a 1000-ton press machine as shown by an arrow a, the outer mold 52 moves downward as shown by an arrow b as shown in FIG. Since the die 53 is extruded inward as shown by the arrow c, the processed material P is formed into a rectangular cross section as shown in FIG.

FIG. 5 shows a work material P and a set of four inner dies.
A plan view showing an arrangement of 53 shows a modified example of the inner die 53. As shown in (a), each inner die 53 is chamfered at 45 degrees on the side in contact with the processed material P, that is, on both sides of the non-graded surface. As a result of the molding process, the inner mold 53 moves inward and approaches each other as shown in (b), and the movement stops when the chamfered portions are in contact with each other, so that the molding also ends, and a square steel pipe of a constant size is always obtained. You can

Further, when pressing by a pressing machine or the like, the molding can be stopped at an arbitrary size by controlling the stroke, so that one set of molds can be used for manufacturing square steel pipes having a plurality of sizes. can do. FIG. 6 shows a sectional shape of a corner portion of a square steel pipe formed according to the present invention. Outer diameter 406
mm, 40 mm thick seamless steel pipe is formed and the outer surface spacing is 3
An example of manufacturing a 24 mm square steel pipe is as follows. Of the shapes of the corners, the outer radius of curvature R ₁ is 50 mm and the inner radius of curvature R ₂ is 16 m.
m, the wall thickness of the corner is 48 mm, the outer shape is almost the same as the corner of the square column, which is a column material of the same size, and the wall thickness is thicker than the general part up to the corner. I understand. Therefore, even if it is directly welded to the column member without using the diaphragm, no misalignment occurs.

Further, when a force is transmitted from the beam flange to the column, a larger force acts on the flange end portion, so that it is advantageous in strength that the corner portion of the square steel pipe is thicker than the general portion. Is. In addition, Table 1 shows the results of forming square steel pipes from various raw pipes.

[0022]

[Table 1]

Although an example of manufacturing a square steel pipe from a steel pipe having a normal circular cross section has been described above, the rounded square steel pipe can be formed into a square steel pipe having a sharp cross section by the forming process of the present invention. . In addition, as described in the section of the prior art, if the square steel pipe is manufactured to an appropriate length and this is cut into a predetermined size as a metal fitting, it is possible to control the angle at the time of cutting. Therefore, it is convenient that the accuracy of parallelism and squareness of the upper and lower surfaces can be obtained.

FIG. 7 shows a blank pipe before being processed (shown by ○ and ●,
Is the L direction, ● is the C direction, the same below) and the graph of the absorbed energy measured by the Charpy test at 0 ° C for the square steel pipe (*, ★) after forming. , And the corners are showing an increasing tendency, and especially for the corners, 25J or more is required, which is far better than this.

FIG. 8 is a graph showing the results of the tensile test. The high numerical value on the upper side is the tensile strength, and the lower value is the yield point. Also,
FIG. 9 is a graph showing the yield ratio (Y _R ) which is the ratio of the yield point to the tensile strength. Each of them shows a numerical value that is almost the same as that of the raw pipe, and there is no particular problem due to the processing.

[0026]

According to the present invention, there is an excellent effect that a thick-walled steel pipe for a connection having a small radius of curvature at a corner can be easily obtained at low cost.

[Brief description of drawings]

FIG. 1 is a front sectional view showing an embodiment of the present invention.

FIG. 2 is a horizontal sectional view taken along the line AA of FIG.

FIG. 3 is a front sectional view showing an embodiment of the present invention.

FIG. 4 is a horizontal sectional view taken along the line BB of FIG.

FIG. 5 is a plan view showing a modified example of the present invention.

FIG. 6 is a partial cross-sectional view of a square steel pipe showing an embodiment of the present invention.

FIG. 7 is a graph showing mechanical properties according to an example of the present invention.

FIG. 8 is a graph showing mechanical properties according to an example of the present invention.

FIG. 9 is a graph showing mechanical properties according to an example of the present invention.

FIG. 10 is a perspective view showing a column-beam connection portion according to the present invention.

FIG. 11 is a cross-sectional view of a thick-walled square steel pipe manufactured by a conventional manufacturing method.

FIG. 12 is a front sectional view showing a conventional method for manufacturing a thick-walled square steel pipe.

FIG. 13 shows another conventional method for manufacturing a square steel pipe,
(a) is a plan view and (b) is a sectional view taken along the line AA.

[Fig. 14] Similarly, showing another conventional method for manufacturing a square steel pipe, (a) is a plan view and (b) is a sectional view taken along the line BB.

[Explanation of symbols]

 1 pillar material 2 metal fittings 3 beam material 11, 31 flange 12, 32 web 21 diaphragm 22 short tube 51 top plate 52 outer mold 53 inner mold 54 form 55 bottom plate 91 female 92 male 93 guide roll 95 base 96 Tube expansion piece 97 Wedge 98 External P processed material (blank plate, short tube)

Claims (3)

[Claims] 1. A thick-walled steel pipe is heated to a recrystallization temperature or higher, dies are arranged in four directions on the outer peripheral surface thereof at right angles to each other, and the dies are simultaneously moved and pressed from the four directions toward the pipe axis. And forming the thick-walled steel pipe into a rectangular cross-section. 2. A thick-walled steel pipe heated to a recrystallization temperature or higher is placed in a vertical position on a bottom plate of a rectangular mold, and the outer peripheral surfaces thereof have inclined surfaces in four directions perpendicular to each other. , Arranging a horizontally movable inner mold and engaging with the inclined surface 4
A thick-walled square steel pipe for a connection characterized in that the thick-walled steel pipe is formed into a rectangular cross section by inserting an outer mold having a base sloped surface between the mold and the inner mold and pressing it down. Manufacturing method. 3. A method for manufacturing a thick-walled square steel pipe for a connection, which comprises cutting the thick-walled square steel pipe manufactured by the manufacturing method according to claim 1 or 2 into a predetermined size.