JPH0547293B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a square steel pipe having an embossed pattern.

By embossing the side surface of a square steel pipe, the vertical load in the same direction as the embossed surface (Fig. 1b)
It has been experimentally confirmed that the crushing load strength per unit area (arrow) is higher than that of ordinary square steel pipes of the same size.

Applications utilizing the above characteristics include, for example, threading materials for steel, and a lightweight and high-strength member can be provided. Furthermore, by applying various embossed patterns, it is possible to use it for decorative members, etc., and the applications that take advantage of this property are wide-ranging.

As a method of embossing a square steel pipe, after it is formed into a square pipe, the embossing is performed by pressing using a core etc. in the pipe, or the embossing is performed in the state of a plate material and then it is pressed into a predetermined shape. It is conceivable to weld by bending from the corner and butting the ends of the plates, but these methods are not economical or efficient because the work steps are roughly divided into two steps.

When manufacturing square steel pipes by embossing with roll forming, continuously shaping the material with roll forming, and butt welding the ends of the steel strip edges, the following two problems arise: It will be done.
First, when a steel strip is embossed, edge waves occur at the ends of the steel strip. Due to the generation of these edge waves, when welding the left and right edges of the steel strip against each other,
It becomes wrapped and welding becomes impossible. The generation mechanism of this edge wave is thought to be as follows.

When forming embossments with depths such as d and e in Fig. 8 on a flat plate part, especially at the corner C shown in Fig. 8c on both edge parts of the steel strip, the surrounding flat plate is The material is attracted from the rays shown in the same figure, and this spreads to both edges of the steel strip.
A periodic edge wave is generated. FIG. 8 schematically represents this state. 31 in the figure
38 indicates a square steel pipe, and 38 indicates an edge wave.

The second point is what kind of bending method should be used for the bending process up to butt welding both edge portions. Generally, in roll forming of square steel pipes,
The method is to bend it to a nearly round shape, butt weld both edges, and then shape it into a square shape in the sizing process. If this bending method is used, not only will the embossed shape be distorted, but since the embossed side is a rigid side, it cannot be bent into a round shape with a constant radius of curvature. Because the plate stiffness in the width direction of the material is non-uniform as a result of the emboss formation), it is not possible to butt weld both edges.

Furthermore, another possible forming method is to bend the blank plate into a nearly square shape and butt weld both edges, but as pointed out earlier, the edge waves that occur during embossing can be considered. for,
The butt of both edges is not aligned properly, making it impossible to weld.

As can be seen from the above, the problem is how to find a bending method that satisfies the conditions for welding by arranging the butt conditions for both edge portions.

In view of this situation, as a steel threading material, a rectangular steel tube with embossing on both sides is continuously embossed using roll forming, and then roll forming is performed to shape and define the square steel tube. In a series of cutting steps, we conducted experiments on the manufacturing method and established a manufacturing method that satisfies the performance as a skit material.

In the present invention, embossing refers to carving grooves at intervals in a portion of the steel strip corresponding to both side surfaces adjacent to the welding surface of the formed square steel pipe.

1a and 1b show a square steel pipe 31 having an embossed pattern 30. FIG. The steel pipe 31 has a top side 35 and a side side 3
6. It consists of a lower side 37, and W indicates a welding line.

That is, the gist of the present invention is to provide a method for obtaining a rectangular steel pipe having a welded seam on one side by embossing a steel strip with a roll and then rolling forming the steel strip. This involves bending the edge using a pair of upper and lower rolls with a radius of curvature _R.

Furthermore, the gist of the present invention is a method for obtaining a rectangular steel pipe 31 having a welded seam on one side by embossing a steel strip 11 with a roll and then performing roll forming. This involves applying a light reduction to the edge of the steel using a pair of upper and lower flat rolls.

The invention will now be described with reference to the accompanying drawings.

FIG. 2 is an overall explanatory diagram of the manufacturing line of the present invention. In the figure, an uncoiler 10, a steel strip 11,
Looper 12, pinch roll 13, embossing roll 14, rough forming roll 15 fin pass roll 1
6, high frequency resistance welding device 17, squeeze roll 1
8, a cooling zone 19, a sizing roll 20, a turquoise head roll 21, and a shearing device 22 are shown.

The steel strip used may be a strip, a slit coil, or a plate, and in order to fully utilize the advantages of continuous roll forming in this method,
A strip or slit coil is preferable, but of course a regular length material can be used without any problem in processing. Depending on the size of the rectangular steel pipe to be manufactured, coiled items such as strips of a predetermined width are processed using the uncoiler 1.
0, and in the case of regular length materials, it is customary to feed them one by one to the pinch rolls using a suitable feeding device.

The strip is fed by one or two passes of pinch rolls to prevent meandering. For this reason, it is preferable to use a flange roll with a flange as the pinch roll, or to combine it with a vertical roll.

The strip is introduced from pinch rolls to embossing rolls. The embossed pattern is formed on both sides of the square steel pipe, but in order to make the performance characteristics of this product effective, that is, to increase the crushing load strength,
It is best to make the embossing length long and deep. Therefore, it is preferable to extend the embossing length to both the left and right sides, up to the vicinity of the upper and lower corners.

As mentioned earlier, by applying embossing at the trial production stage, edge waves are generated at the welding edges, making it impossible to weld both ends of the steel strip.The purpose of the present invention is to eliminate this problem. Then, at the same time as the embossing process, the upper side is made with a constant radius of curvature R _E (the third
The feature is that a pair of upper and lower rolls with a diameter (see Figure) are added to the embossing roll to press down over the entire width of the material, thereby canceling out the edge waves. In addition, flange rolls with flanges (Fig. 3, 2
By adding 9), meandering of the material can be prevented.

FIG. 3 shows an example of an embossing roll in the present invention. In the figure, the embossing roll 14 is composed of an upper roll 14-1 and a lower roll 14-2, and the upper roll is provided with a female die 25 and the lower roll is provided with a female die 26 in the desired shape described above. In the present invention, the edge portion of the steel strip, which becomes the upper side when formed into a square steel tube, is bent by upper and lower rolls having a radius of curvature _RE . form. 2
9 is a flanged roll.

Generally, a blank holder is used to hold down the wrinkles during deep drawing of thin plates, but according to the findings of the present inventor, by simultaneously embossing the steel strip and bending the edge portions mentioned above, It has become clear that even if edge waves occur due to tension during embossing, the wrinkles are canceled out by the bending process using rolls, and a groove free of weld defects can be obtained during butt welding, which will be described later.

Further, according to the present invention, in addition to the above-mentioned bending process during embossing, the tension caused by embossing is canceled by applying a light reduction (plate thickness x 10%) to the edge part of the steel strip using a flat roll. , which can solve the above-mentioned problem of wrinkle formation. Therefore, it is important to perform embossing and roll rolling of the edges at the same time.

Furthermore, according to experiments, although the embossing roll was used without being driven, it was confirmed that the forming torque required to form the embossing accounted for approximately 30% of the total torque. Therefore, it is desirable to drive the embossing roll.

When driving the embossing roll, it is preferable to drive the embossing roll at a peripheral speed slightly lower than the feed speed during forming. This applies tension with the embossing roll stand and in the next process.
If it is not formed in tension, it will sag between the stands,
This is because this sag accumulates, causing an overlapping phenomenon and making molding impossible.

Once the embossing has been formed, it is introduced into a rough forming roll, which is the next step, and bending of the top edge and side edges including the embossed surface are performed. Note that the rolls used in the next and subsequent steps are assembled in such a way as to avoid the sides on which the embossing is formed. The upper corner bending roll 15-A is the upper roll 15 as shown in FIG.
-1 and a lower roll 15-2, and the edge of the upper roll is a caliber (hole type) with a radius of curvature R _B.
27-2 is formed to give the desired curvature to the steel strip, facing the concave caliber of the edge of the lower roll, and at the same time, when it is made into a square tube, it should form the left and right upper corners. Position the steel strip at θ゜_B = 60゜±
It has a profile that bends up to 10°. The radius of curvature R _B is the radius of curvature added during embossing.
R should be smaller than _E , preferably about 1 to 3 times the side length. Further, the steel strip is bent at a position 28 leaving widths L ₁ and L ₂ at both ends so that the length of the upper side of the square steel pipe is the same when the joint is welded. The bending position 28 is preferably a symmetrical position with respect to the roll center C.

Next, the steel strip 11 is introduced into a rough forming roll 15-B shown in FIG.
is bent to approximately 70°±10° and roughly formed into a pentagonal cross-sectional shape with open apexes.

The steel strip whose upper and lower corners are bent to an intermediate angle is sent to a fin pass roll 16 shown in FIG. In the fin pass process, the upper side bending radius is
Getting R _F. To obtain a roll hole type capable of obtaining feeding force by applying reduction (restraint). To obtain a roll hole type in which an embossed shape formed in an upstream process does not collapse. For this purpose, the roll hole type to be used in the operation was determined from an experimental standpoint.

This will be explained below based on FIG.

In Figure 7, straight line 1 is an example in which the bending radius of the upper corner is the same in each forming process.If the bending radius is smaller than that of the first stage, the corner part will become plastic at an early stage, as is clear from the plasticity theory. As a result, spring back cannot be obtained at the upper bent portion, making it impossible to butt the two edges with a squeeze roll. In other words, with squeeze rolls, it is customary to butt-weld by drilling into the springback of the steel strip and applying an upset, and if you try to forcefully adjust a material that does not have a springback, it may bend into the pipe. The following is an example where welding became impossible due to this.

On the other hand, for curve 2, the radius of curvature of the upper corner bending in the welding process is (8~9) x (plate thickness), the radius of curvature of the upper corner bending in the fin pass is gradually decreasing, and the angle distribution (θ° _F ) is θ _F1 ≦θ This shows how the spring back is properly controlled by giving _F2 ≦θ _F3 , reducing the rate of change, and sending the material to the welding process. According to this example, the butt was stable and the welding was highly reliable. Furthermore, curve 3 shows an example used for operation.

In this way, the bending angle (θ° _F3 ) of the upper corner bending radius of the final stage of Finpass is advanced to 80°±5°, and at the same time both edge ends of the square steel pipe are placed on the sides of Finpass roll F, and the outer circumference of the tube is A compressive force is applied by a roll to give a reduction (restraint) of 0.5 to 1% to the square tube.

After each side of the square tube has been preformed in this way, it is subsequently introduced into welding rolls having a predetermined roll profile, electrical resistance welding is performed, and the tube is formed.

The square steel pipe produced in this way is shaped into the final cross-sectional shape using several stages of shaping rolls in the sizing process, and then cut to the required length using a customary appropriate shearing machine for production. . In experiments, even at high-speed molding speeds exceeding 100 m/min,
It has been confirmed that molding can be performed.

As explained above, according to the method of the present invention,
By incorporating an embossing roll pass in a series of pipe-making lines, embossing and roll forming are performed continuously by roll forming, and embossed square steel pipes can be manufactured efficiently and economically.

[Brief explanation of the drawing]

FIG. 1a is a schematic diagram of a square steel pipe according to the present invention, FIG. 1b is a schematic cross-sectional diagram, FIG. 2 is an explanatory diagram of the process of the present invention, and FIG. 3 is a partial cross-sectional diagram of an embossing roll of the present invention. FIG. 4 is a partial cross-sectional view of a rough forming roll of the present invention, FIG. 5 is a partial cross-sectional view of another rough forming roll of the present invention, FIG. 6 is a fine pass roll of the present invention, and FIG. 7 is a partial cross-sectional view of a rough forming roll of the present invention. Fig. 8a is a schematic diagram showing the state in which edge waves are generated at the edge part due to elongation strain generated around the embossing, and Fig. 8b is a diagram of (top corner bending radius of curvature)/(plate thickness). Schematic diagram, c is a partial view of b, d is a YY cross-sectional view of c, e
is a XX sectional view of c. 14: Embossing roll, 15: Rough forming roll,
16: Fin pass roll, 17: High frequency welding machine,
18: squeeze roll, 25: female type, 26: male type, 38: edge wave.

Claims (1)

[Claims] 1. A method for obtaining a square steel pipe 31 having a welded seam on one side by embossing a steel strip 11 with a roll and then performing roll forming,
A method for forming a square steel pipe having an embossed pattern, characterized in that the edge portion of the steel strip is bent by a pair of upper and lower rolls having a radius of curvature _RE at the same time as the steel strip is embossed. 2. An upper corner bending roll having a radius of curvature R _F , which is made by shaping the roughly formed steel strip in the fin pass process of roll forming into a gradually decreasing shape with a constant ratio smaller on the downstream side than on the upstream side when viewed from the material conveyance direction. A method for forming a rectangular steel pipe having an embossed pattern according to claim 1, wherein the method comprises forming a square steel pipe with a plurality of stages of fin pass rolls having an embossed pattern. 3. In a method for obtaining a square steel pipe 31 having a welded seam on one side by embossing a steel strip 11 with a roll and then performing roll forming, the edge portion of the steel strip is simultaneously embossed. A method for forming a rectangular steel pipe having an embossed pattern, the method comprising applying a light reduction to the steel pipe using a pair of upper and lower flat rolls.