JP2569963B2 - Manufacturing method of square steel pipe - 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 manufacturing a square steel pipe (column material) suitable as a structural material for a high-rise building.

[0002]

2. Description of the Related Art In recent years, the demand for square steel pipes (column materials) having a square cross section, mainly for building materials for general buildings, factories or warehouses, has been increasing rapidly.

Various proposals have been made for the production of such a column material, but the following method has been established as a representative production method, and the following method has been established. Means are employed. (a) A round steel pipe such as an ERW pipe is used as a material,
For producing a column material by continuously performing surface forming by cold roll forming using a roller forming machine (Japanese Patent Laid-Open No. 61-11561).
No. 4, JP-A-63-2515), (b) A method of continuously forming a column material directly from a strip material by cold roll forming using a multi-stage roll forming machine ( JP-A-61-193723), (c) As shown in FIG. 2, two channels in the width direction of the material steel sheet were sequentially subjected to 90 ° press bending to form a channel material (channel material). A method in which two of these channel members are opposed to each other and the edges are welded to each other to form a column material (two-seam method). (D) As shown in FIG. Press-bending to give an approximate column material shape, and then adjusting the shape by cold roll forming, and then welding the edge butt portion (1 seam method), (e) FIG. As shown, after cutting the material steel plate to each side dimension of the column material, the four steel plates were welded in a box shape. How to a column member (4 Side box column) (pre - DOO 4 ply method).

However, among the methods for producing each of these column materials, the size of the column material that can be formed by the cold roll forming method described in the above items (a) and (b) is at most about 500 mm square. It was not suitable for manufacturing large-sized column materials used for large buildings and high-rise buildings.

[0005] Further, the plate 4 mentioned in the above (e)
In the case of the sheet-to-sheet method, a large-sized column material that is sufficiently reliable for high-rise buildings can be obtained. However, in the manufacture of the material, “thick narrow cutting of thick plates”, “welding at four places” and “ It is necessary to attach a backing metal at the time of welding, etc., so that the production efficiency is extremely low, and the cost must be increased.

[0006] On the other hand, the press method mentioned in the above items (c) and (d) has a good production efficiency and can produce a relatively large (500 mm square or more) column material. In particular, in the case of the “two-seam method” described in the above item (c), the punch can be shared regardless of the size, and a small turn is effective.
Since it is easy to manufacture a product in which a diaphragm for preventing buckling is inserted in the inside of the connection portion, it has recently attracted particular attention.

However, at present, buildings having a height of more than 60 m need to be rated as "Building Center", but "press-formed column materials" have not been used for practical purposes. It has become. The reason is that the performance (uniform elongation, toughness, yield point, yield ratio) of the corner part, which is the formed part (bent part), of the press-formed column material is deteriorated by work hardening. Was. For example, uniform elongation [Eu
] Is estimated to be 10% or more.
As shown in (1), in the column material manufactured by the press method, the uniform elongation of the inner surface and the outer surface in the corner portion is remarkably reduced, resulting in less than 10%.

[0008] In particular, there is a demand for a large-sized press-formed column material and a tendency to have a large wall thickness in response to the recent increase in size and height of buildings and the like. Since the degree of working of the knurled portion (elongation of the outer peripheral portion) is increased, the mechanical performance as a rectangular column product tends to be further deteriorated.

Further, in consideration of the tendency to increase the size of the column material, the press-formed column material has another limitation in terms of the formable dimension range. That is, the press used in the press forming of a large column material is generally at most about 3000 ton class, but in the case of the 3000 ton class press, the maximum formable thickness of the steel sheet is about 32 mm thick. However, there is a concern that this will not be able to meet the demand for thickening, which is expected to increase in the future.

In view of the above, the object of the present invention is to provide not only a column material having a relatively small size but also a large column material required for a high-rise building exceeding 60 m, for example. The aim was to establish a means that could be mass-produced at a low cost with good workability while guaranteeing performance.

[00011]

In order to achieve the above object, the present inventors have carefully studied the above-mentioned various situations surrounding the column material from various angles, and in particular, have discussed the two-seam press. Focusing on the relatively good workability, low manufacturing cost, and relatively high manufacturable dimensions of the column material,
As a result of diligent studies in search of a solution to the above-mentioned problem pointed out by the press-column material, the following results were obtained. When the induction heating is performed locally using a special work coil and the entire length of the bent portion is simultaneously heated without time lag, and then bent immediately, a) The corner portion (bent portion) due to work hardening The performance degradation is remarkably improved. B) The thick material can be sharply bent to expand the allowable range of the moldable dimensions. C) The molding load is reduced and the molding efficiency is reduced. Phenomena such as improvement, etc. appear intertwined, and it is possible to produce high-performance large-sized column materials that can be sufficiently satisfied even if existing press equipment is used almost as it is. "

The present invention has been completed on the basis of the above findings and the like.
After the local heating of the 0 ° bent portion and the simultaneous heating over the entire length of the bent portion are performed by induction heating, press bending is performed while the bent portion is in a high temperature state to obtain a U-shaped channel member, By welding two of these channel members facing each other and welding the edge parts, a column material (square steel pipe) with good performance can be mass-produced stably without special dimensional restrictions. Have.

Hereinafter, the present invention will be described in more detail with reference to the drawings together with its operation and effects.

FIG. 1 shows one of the column material manufacturing steps according to the present invention.
FIG. 3 is a conceptual diagram illustrating an example. First, a groove is formed on both edges in the width direction of a material steel plate according to a conventional method. A long rectangular annular induction heating work coil surrounding the entire length of the bent portion is inserted through the steel plate after the groove processing for welding is completed, and the bent portion is locally heated. Subsequently, while the bent part of the steel sheet is in a high temperature state by the induction heating, the part is immediately subjected to 90 ° press bending.

Next, the other bent portion is similarly bent after heating. Thus the groove profile of the resulting U-shaped cross section and is welded with temporary by CO ₂ welding and facing each other two as a conventional method, then the inner and outer surfaces Sabuma - Zia - welding by click welding To form a square column material. Of course, the welding method is not limited to sub-mark welding, and there is no problem if MIG welding or the like is applied.

The above is an example in which V-shaped bending is performed twice in order to obtain a channel material as an intermediate material. However, in order to increase efficiency, induction heating is performed at two bent portions as shown in FIG. The two heating portions may be bent by one stroke by press U bending to form a channel. The most characteristic feature of the present invention is that only a necessary part is subjected to induction heating under specific conditions immediately before press bending.

When the local heating of the bent portion is performed immediately before the press bending, the following effects can be obtained. A) The work hardened structure is suppressed, the mechanical properties of the corners are improved, and a level sufficient for application to high-rise buildings is secured. FIG.
FIG. 4 is a graph comparing mechanical properties of a corner portion between “in the case of locally heating a bent portion” and “in the case of cold forming without heating” during 90 ° bending of a steel sheet. 7 also heats the bent part locally to 600 ° C,
It can be confirmed that molding at 900 ° C. ensures good corner performance.

B) Also, the advantages of hot forming can be enjoyed. As a result, the molding load can be significantly reduced (yield stress can be reduced to 1/3 to 1/5 of that of cold-worked materials), and thick products can be manufactured (manufacturable range can be expanded to the thicker side). Furthermore, it is also possible to reduce the R of the corner (even if it is 3R by cold press molding, it becomes about 2R when the method of the present invention is applied), and a beautiful rectangular box having a sharp corner is obtained. Can be FIG. 8 is a graph showing the relationship between the heating temperature of steel and the deformation resistance. It is clear that the deformation resistance sharply decreases as the heating temperature increases.
As shown in the above, in the production of the press-formed column material, the forming load is significantly reduced by the local heating of the bent portion, and the range of dimensional dimensions that can be produced is greatly expanded. This fact is shown in FIG. 9, which is a comparison experiment between the case where the local heating of the bent portion is performed and the case where the column material is cold-formed without heating during the bending process of the steel sheet. Can be fully confirmed.

Here, the heating temperature of the bent portion is preferably adjusted so that the press forming temperature is in the range of 600 to 1100 ° C. This is because, in order to sufficiently eliminate the work hardened structure in the bent portion by various experiments, it is desirable to secure a press forming temperature of 600 ° C. or more.
If the temperature is less than 0 ° C., it is difficult to secure “uniform elongation _Eu > 10%” in the mechanical performance of the processed portion. On the other hand, from the viewpoint of reducing the molding load, it is effective to set the molding temperature higher. However, in the present invention, the heating is local heating, and therefore, the heat is easily diffused to the surroundings by heat conduction. -The loss is large. That is, although the molding load can be reduced as the temperature increases, the heating energy loss also increases. Further, when viewed as hot forming, if the temperature is set to 1100 ° C. or more, a scale loss and the like are added, and the corner portion forming and the shape of the R are likely to vary. Therefore, it is recommended to heat the bent portion so that the press forming temperature is in the range of 600 to 1100 ° C.

The induction heating under the specific conditions defined in the present invention is performed by a special work coil (a long rectangular annular induction heating work coil surrounding the entire length of the bent portion) as shown in FIG. Can be realized stably. In general, when a plate material is partially induction-heated, a spiral or small circular work coil is used, and heating is performed with the coil facing the heating surface. When induction heating is performed by using a work coil, a) the heating portion becomes extremely narrow and localized, and only the required portion (bending portion) can be heated, preventing unnecessary oxidation and deterioration of steel plate performance. (B) Uniform simultaneous heating over the entire length of the bent portion of the plate is possible, and press bending can be performed under the same conditions in the longitudinal direction, so that products with partial unevenness in quality can be obtained. Since the work coil has a shape surrounding the heated portion (the work coil portion is opposed to the steel plate as the material to be heated), heating is performed in the simplest and most efficient manner. The local heating of only the main part enables the energy efficiency to be improved, the energy consumption to be reduced, and other effects can be ensured. In addition to these, it is possible to provide an excellent means for producing a column material that has not been achieved in the past. .

[00020]

[Summary of Effects] As described above, according to the present invention,
It is possible to stably mass-produce column materials having sufficiently satisfactory performance even at corners without special dimensional restrictions, and to supply high-performance building materials and the like at low cost. And industrially very useful effects.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating an example of a column material manufacturing process according to the present invention according to the present invention.

FIG. 2 is an explanatory view of an example of a conventional method for manufacturing a press-formed column material (two-seam method).

FIG. 3 is an explanatory view relating to another example (1 seam method) of a conventional method for producing a press-formed column material.

FIG. 4 is an explanatory diagram relating to yet another example of a conventional press-formed column material manufacturing method (a four-plate aligning method).

FIG. 5 shows a core of a column material manufactured by a conventional press method.
It is the graph which showed the state of uniform elongation in a knurl part.

FIG. 6 is a conceptual diagram illustrating another example of the column material manufacturing process according to the present invention according to the present invention.

FIG. 7 is a graph comparing the mechanical properties of the corner portions in the case of performing “local heating of a bent portion” and the case of performing “cold forming without heating” during 90 ° bending of a steel sheet. .

FIG. 8 is a graph showing the relationship between the heating temperature of steel and the deformation resistance.

FIG. 9 is a graph comparing the dimensional range in which a column material can be manufactured between “in the case of performing local heating of a bent portion” and “in the case of cold forming without heating” during bending of a steel sheet.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Yamamoto, 3rd section of Kashima-cho, Kashima-gun, Ibaraki Pref. Sumitomo Metal Industries, Ltd. Kashima Works (56) References

Claims (1)

(57) [Claims] 1. After beveling both edges of a steel sheet, 9
The local heating of the 0 ° bent portion and the simultaneous heating over the entire length of the bent portion are performed by induction heating, and then the bent portion is press-bent in a high temperature state to obtain a channel having a U-shaped cross section. A method for manufacturing a rectangular steel pipe, characterized in that two of these channel members are faced to each other and the edges are welded to each other.