JP2813632B2 - Material improvement method for corners of large diameter square steel pipes - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a method for forming large-diameter rectangular steel pipes, which comprises bending a thick steel plate by cold plastic working to form corners of the rectangular steel pipe. Deterioration of local material quality of steel sheet based on
The steel plate was heated to a predetermined temperature and tempered to correct the deterioration of the steel plate material. The present invention relates to a method for improving the quality of a corner of a large-diameter rectangular steel pipe in which a seam line is located on a side portion other than the corner portion.

2. Description of the Related Art Conventionally, a mass production method of a one-seam or two-seam large-diameter rectangular steel pipe formed by bending a thick steel plate and used as a column of a building has conventionally been classified into practically aside from the literature. A sheet steel plate is bent parallel to the longitudinal axis direction and overlapped in the width direction, and four places corresponding to the corners are bent, the cross section is formed into a shape similar to a square steel pipe, and both side edges of the steel plate are projected. It is welded together to form a square one-seam steel pipe.

One sheet steel plate is bent at two places along the width direction to form a U-shaped cross section, and the steel sheet is formed into a square cross-section by opposing each other, and its two leg edges are butt-welded and two-seam Manufactures square steel pipes.

Such construction methods are widely implemented even if there are slight differences in construction methods in detail.

As described above, conventionally, the economical method for manufacturing large-diameter rectangular steel pipes that has been implemented includes cold plastic deformation of a thick steel plate in any of the methods, that is, for a steel sheet for forming a corner portion, 90 ゜ cold bending is included.

By the way, when a flat thick steel plate is coldly bent at approximately 90 °, even if a required radius (outer radius) is given to the bent portion of the steel plate, the corner is formed. In the cross section of the corner steel, cold plastic deformation is performed while a tensile force acts on the material outside the neutral surface and a compressive force acts on the inside, so even though the processing is within the elastic limit of the material, It is inevitable that the material deteriorates, and there is no danger that brittle fracture will occur at the deformed portion due to repeated stress.

Further, even after removing the external force, residual stress is generated in each of the bent portions due to cold plastic working.

The above-mentioned phenomenon becomes more conspicuous as the thickness of the steel material is larger and the R given to the corner at the time of bending is smaller.

However, conventionally, regarding the specifications of this type of large-diameter rectangular steel pipe, the shape and structural characteristics thereof are mainly described as follows: (1) Compared to a section H-section steel having the same unit weight, the second moment of area per weight, High section modulus, strong against bending and torsional external force.

(2) The secondary radius of the cross section is large, and it is strong against buckling.

(3) Good balance of cross-sectional characteristics in the X and Y directions.

(4) The column cross-sectional area can be made relatively small,
The ratio of usable area to the same floor area can be increased.

(5) Since the cross-section is box-shaped, the aesthetic appearance is not impaired even if the material is used as it is exposed.

(6) Fireproof coating, painting and other decoration and construction around the column are easy and economical.

Although benefits are recognized for such construction characteristics, demand is growing, but in view of the above processing conditions, objective and technical analysis of material weaknesses or uncertainties inherent in square steel pipes The large-diameter rectangular steel pipe tends to be distributed on the market without sufficient consideration.

On the other hand, steel structures, buildings, etc. that use this type of large-diameter rectangular steel pipe as a column must generally support the weight of the structure itself and the accompanying structure for a long time after the column is constructed once. Of course, earthquakes
It is required to safely withstand severe repeated loads caused by external forces such as typhoons, and in many cases, these columns are in a construction state in which replacement or repair is not possible in principle.

Recently, large-diameter rectangular steel pipes formed by cold bending have been widely used as columns for buildings, and have also been used as columns for middle- and high-rise buildings. Consumers have been increasingly interested or reflected on the problem that the deterioration of the material based on the bending process may promote the brittleness change at the location.

Therefore, recently, problems have been pointed out by users and third parties regarding this kind of material problems of large-diameter rectangular steel pipes, and it is necessary for manufacturers to take immediate measures.

Problems to be Solved by the Invention The method of the present invention responds to requests from those users and the like,
Conventionally, by improving the corner forming method based on the cold plastic deformation of large-diameter rectangular steel pipe in the known manufacturing method, the corner of rectangular steel pipe by bending thick steel plate while avoiding cost increase as much as possible It is an object of the present invention to provide a method for improving the material of a corner portion of a rectangular steel pipe, which repairs the deterioration of the material of a corresponding steel plate.

Means for Solving the Problems The method of the present invention has the following components to achieve the above object.

(1) Cold-bending a single-plate steel plate along the longitudinal axis direction, forming the cross-section of the steel plate into a shape similar to a rectangular steel pipe, and butting and welding the steel plate edges to each other to form a square cross-section By doing so, for a large-diameter rectangular steel pipe configured by positioning the seam line on a side part other than the corner part, each corner part of the steel pipe is opposed to each corner part, and the vicinity of the same corner part is respectively predetermined. A method for improving the material of a corner portion of a large-diameter rectangular steel pipe, comprising a step of arranging a heating means for heating to a temperature and relatively moving the heating means along the longitudinal axis of the rectangular steel pipe.

The large-diameter rectangular steel pipe formed based on the manufacturing method including the cold bending process, after the process of complete welding of the seam line of the same large-diameter rectangular steel pipe or the process of passing the flaw detection device for the welded joint, In a plane perpendicular to the longitudinal direction of the steel pipe, around the cross section of the steel pipe, the large-diameter rectangular steel pipe is charged into a heat treatment furnace equipped with a heating means installed to be opposed to and close to each corner, While relatively moving in the longitudinal axis direction, the vicinity of each corner formed by cold bending is continuously heated to about 670 ° C. to 760 ° C. by the heating means.

A gas or liquid fuel burner is employed for each heating means provided at each corner of the large-diameter rectangular steel pipe, and the flow of gas in the combustion chamber of the heat treatment furnace is usually a corner furnace. It becomes earring form. The position of the burner in the combustion chamber at that time may be provided axially symmetrically with respect to the large-diameter rectangular steel pipe. That is, the thermal expansion based on the heating at the corners of the steel pipe is measured so as to occur symmetrically with respect to the central axis of the cross section of the steel pipe. Further, a plurality of burners facing / arranged at the corners of the steel pipe can be arranged side by side in the longitudinal direction of the steel pipe.

Thus, while the large-diameter rectangular steel pipe thus formed passes through the heat treatment furnace, the vicinity of each corner is continuously and for a certain period of time.
By heating to a temperature of about 670 ° C to 760 ° C and then allowing it to cool naturally, the material near the corner of the steel pipe whose material has deteriorated due to bending due to cold plastic deformation of the thick steel plate has been refined. Thus, the original state is restored and the residual stress due to the above processing is eliminated.

The large-diameter rectangular steel pipe whose material has been refined in the vicinity of the corner of the steel pipe is further cut to the specified length in the longitudinal direction, is used for a flaw detector for welded joints, etc., or is passed through a straightening machine in the longitudinal axis direction. It is transported to go through a finishing process.

As described above, according to the method of the present invention, as a means for refining the brittleness or residual stress of the steel sheet constituting the steel pipe after forming the large-diameter rectangular steel pipe, the objective is achieved at a relatively low cost. Thus, it is possible to efficiently provide a high-quality large-diameter rectangular steel pipe in which the brittleness and deterioration of the material near the corner, which has been conventionally concerned, are eliminated.

Example An example of the method of the present invention and an apparatus for improving the quality of a corner portion of a large-diameter rectangular steel pipe implementing the method of the present invention will be described below with reference to the drawings. Partial deformation is possible within the range of the known technical level in the above, so that the constitutional requirements of the method of the present invention are interpreted in a limited manner based only on the specific examples described in the present examples, unless a special reason is found. Should not be.

FIG. 1 shows a processing line of a device for improving the quality of a corner portion of a large-diameter rectangular steel pipe for implementing the method of the present invention, and FIG. 1 (a) shows an apparatus constituting the processing line. b) shows a state of forming or working a steel plate corresponding to each step on the same apparatus.

In the present embodiment, the square steel tube forming line is a single plate steel plate.
11 is applied to the bending press 3, and the same sheet steel plate 11 is cold-bent along the longitudinal axis direction, that is, bent at four places in the width direction, and the cross section is formed into a shape 12 similar to a square steel pipe. After forming, it is passed through a shaping roll stage 4 to shape the cross section into a square of a standard size, and the longitudinal edges of the steel plate are butt-welded by a welding machine 5 to form a seam line at a side portion other than a corner portion. , The large-diameter rectangular steel pipe 14 is formed.

In addition, a manufacturing method of a large-diameter rectangular steel pipe based on known cold plastic working, that is, a single-plate steel sheet is bent at two locations along the width direction and formed into a U-shaped cross section, and the cross sections are opposed to each other. It is also possible to use a method of forming a square steel material and butt-welding the two leg edges to form a two-seam large-diameter square steel pipe.

The large-diameter rectangular steel pipe 14 thus shaped is carried along a longitudinal axis thereof into a tunnel type refining furnace 7 in which the inner wall peripheral surface is stretched with refractory bricks. A burner (heating means) for heating the vicinity of the large-diameter rectangular steel pipe 14 is provided symmetrically with respect to the central axis of the steel pipe cross section, along the steel pipe transfer direction, and opposed to each corner of the large-diameter rectangular steel pipe 14, A plurality of windows for injecting the spray flame into the furnace are provided.

Large-diameter square steel pipe 14 carried into tempering furnace 7 after cold forming
Is symmetrically heated near the corners of the steel pipe while it is transported in the longitudinal direction in opposition to the burner flame that heats the vicinity of each corner, and the vicinity of the pipe reaches 700 ° C to 800 ° C Alternatively, the required heating temperature is maintained for a specific period of time by gradually heating the heat treatment furnace 7 while being exposed to a burner flame several times and heating to 700 to 800 ° C., during which time it deteriorates based on cold plastic working. The material in the vicinity of the corner of the steel pipe is gradually refined / improved, and then carried out of the refining furnace 7, and then the heating temperature of the corner of the steel pipe is gradually cooled.

Burner fuels include coal gas as well as light oils such as LNG and LPG,
Liquid fuels such as kerosene and heavy oil may be used.

The fuel gas is sucked by the exhaust device provided near the material outlet of the heat treatment furnace 7 and does not leak to the outside from the material inlet / outlet of the heat treatment furnace 7 and the burner flame injection window.

However, a curtain-like member made of a heat-resistant material is provided at the inlet / outlet of the steel pipe of the heat treatment furnace 7 so that heat energy is not unnecessarily released to the outside from the opening, and no cooling air is sucked in from the outside. In this way, the thermal efficiency is increased.

Of course, the compressed air used for the burner is also preheated by the thermal energy leaking from the combustion gas exhaust device or the heat treatment furnace wall. This cools the combustion gas passing through the gas exhaust device and extends the service life of the device.

Thus, the large-diameter square steel pipe 14 unloaded from the heat treatment furnace 7
Is fed into the cutting machine 8 and the end portion is cut by a cutter which slides in synchronization with the movement of the steel pipe 14 to form a product 15 which is a large-diameter rectangular steel pipe having a unit length of the standard length in the longitudinal axis direction.

Since the vicinity of each corner of the large-diameter rectangular steel pipe (product) 15 still maintains a high temperature, the cut large-diameter rectangular steel pipe (product) 15
In step 15, the large-diameter rectangular steel pipes 15 arranged on the cooling zone 9, air-cooled or water-cooled, and cooled to room temperature are carried out to the product carrying-out table 10.

Although not shown, it is attached to the cooling zone 9 and
Welding joint inspection equipment is installed to prevent unexpected defective products from being mixed into products.

When the steel pipe shaping speed of the shaping roll stage 4 does not match the steel material refining ability of the refining furnace 7, in FIG.
Immediately after the shaping roll stage 4, a cutting machine 8 is provided to first form a square steel pipe having a standard tone, and then the steel pipe is sequentially charged into a plurality of heat treatment furnaces 7 provided in parallel. If this is the case, matching between the two processing efficiencies becomes possible.

Further, in consideration of the case where the rectangular steel tube is formed by the bending press 3 and the formed steel tube is distorted in the longitudinal axis direction based on the butt welding of the steel material longitudinal edge portion,
A straightening machine (not shown) may be provided in a part of the line.

As described above, according to the embodiment method of the present invention, a thick single steel plate is bent by cold plastic working and formed by a conventionally known method for manufacturing a large-diameter rectangular steel pipe forming a corner portion. The brittleness of the corner material is smaller than that of
The degree of degradation or residual stress is quite different.

Further, the residual stress in the vicinity of the corner of the steel pipe is extremely small, so that a product with improved quality can be provided.

In addition, various effects described in the above section (action) can be obtained.

Effects of the Invention The method of the present invention is as described above. (1) In a thick-walled large-diameter rectangular steel pipe, the brittle deterioration of the material based on the cold plastic deformation at the corner of the steel pipe, which is natural in the conventional product, is reduced. Does not occur. Further, it is possible to provide a high-quality product with almost no residual stress generated due to corner forming.

(2) Although the tempering step of the steel pipe material is incorporated in the forming step, the forming efficiency of the steel pipe does not decrease.

(3) The refining furnace can use the lowest-priced fuel as much as possible, and the refining of the material by heating can be performed relatively inexpensively.

(4) It is unavoidable that the cost required for heating is increased, but the tempering of the steel plates constituting the large-diameter rectangular steel pipe is performed within the minimum necessary range, so that a tempered high-quality steel pipe can be obtained. To keep the product low price.

For example, the method for improving the material of the corner portion of the large-diameter rectangular steel pipe according to the present invention has special functions and effects that cannot be expected by the conventional thick-walled large-diameter rectangular steel pipe forming method.

[Brief description of the drawings]

FIG. 1 shows an outline of a method for improving the material quality of a steel pipe corner portion of the present invention, an apparatus for performing the method, and a shape of a steel sheet formed based on the method. 3 ... bending press, 4 ... shaping roll stage, 5 ... welding machine, 7 ... tempering furnace, 8 ... cutting machine, 9 ... cooling zone,
10… Product unloading table, 11… Single-plate steel plate, 12… Shape similar to large square steel pipe, 14… Large square steel pipe, 15 …… Product (large square steel pipe).

──────────────────────────────────────────────────続 き Continued on front page (73) Patent holder 999999999 Shin Nakajima 4-26-27, Kichijoji Honcho, Musashino City, Tokyo (72) Inventor Shin Nakajima 4-26-27, Kichijoji Honmachi, Musashino City, Tokyo (56) Reference Reference JP-A-63-2515 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B21C 37/15

Claims (1)

(57) [Claims] 1. A single-plate steel plate is cold-bent along a longitudinal axis direction, the cross-section of the steel plate is formed into a shape similar to a rectangular steel pipe, and edges of the steel plates are butt-welded to each other to form a rectangular cross-section. By forming the seam line into a large-diameter rectangular steel pipe configured with the seam line located on a side part other than the corner part, facing each corner part of the steel pipe, the vicinity of the same corner part, respectively A method for improving the quality of a corner portion of a large-diameter rectangular steel pipe, comprising a step of arranging a heating means for heating to a predetermined temperature and relatively moving the heating means along the longitudinal axis of the rectangular steel pipe.