JPH0547294B2 - - 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-mentioned characteristics include, for example, use in skid materials for steel, and it is possible to provide lightweight and high-strength members. 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, a core or the like is used inside the pipe to emboss it by pressing, or by embossing it in the form of a plate and press it into a specified shape. It is conceivable to bend the plate from the corner, butt the edges of the plate, and then weld.
According to this method, the work steps are roughly divided into two steps, so it cannot be said to be economical or efficient.

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 problems can be raised: .

The first point is that when a steel strip is embossed, edge waves are generated at each embossed pitch on the edge of the steel strip.
Due to the generation of edge waves, when the left and right end edges of the steel strip are brought together and welded, a lapping condition occurs, making welding impossible. The generation mechanism of this wave can be considered 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 As shown in the diagonal lines in the figure, material is pulled from the edge of the steel strip, 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
34 indicates a square steel pipe, and 34 indicates an edge wave.

Furthermore, when embossing is performed with rolls, if the roll forming line of the square steel pipe is carried out on the same line, the embossing will be discontinuous as shown in Figure 1 or Figure 8, and the influence of material vibration etc. caused by embossing will occur. However, there is a problem in that this affects the roll forming.

In view of this situation, as a steel threading material, a square steel tube with embossing on both sides is continuously embossed using roll forming, and then formed to a specified length. 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 a steel strip corresponding to both side surfaces adjacent to a welding surface of a square steel pipe.

Figure 1 shows a square steel pipe 3 with an embossed pattern 30.
1 is shown. The square steel pipe 31 has a top side 35, a side side 36,
It consists of a lower side 37, and W indicates a welding line.

That is, the gist of the present invention is a method for obtaining a square steel pipe having a welded seam on one side by embossing a steel strip with a roll and performing roll forming.
At the same time as embossing is applied to the steel strip, the edge of the steel strip is bent using a pair of upper and lower rolls having a constant radius of curvature, and the mutually independent embossing roll drive system and forming roll drive system are synchronously controlled. The purpose is to form a certain amount of loops in the steel strip between the embossing roll stand and the forming roll stand.

The present invention will be explained below with reference to the drawings.

FIG. 2 is an overall explanatory diagram of the method of the present invention. In the figure, an uncoiler 10, a steel strip 11, an embossing roll 14, a pinch roll 13, a rough forming roll 1
5, Fin pass roll 16, high frequency welding device 1
7, squeeze roll 18, cooling zone 19, sizing roll 20, Turks head roll 21,
A shearing device 22 is shown. In the present invention, the embossing roll 14 is provided with a DC control drive system 30, a loop detector 23 is provided in the looper between the embossing roll 14 and the pinch roll 13, and a speed detector 24 is provided on the entry side of the rough forming roll 15. It is provided. 32 indicates a forming roll DC control drive system. The DC control drive system controls the rotation speed of the DC motor.

The steel strip used may be either a strip or a slit coil, and in order to take full advantage of the continuous processing of roll forming in this method, a strip or a slit coil is preferred. A coiled material such as a strip having a predetermined width according to the size of the square steel pipe to be manufactured is introduced into an embossing roll through an uncoiler. 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 necessary to make the embossed pattern long and deep. good. Therefore, it is recommended that the embossing length be extended to the vicinity of the upper and lower corners on both the left and right sides.

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. At the same time as embossing, the upper side is set to a constant radius of curvature R _E (Figure 3).
The embossing roll is equipped with a pair of upper and lower rolls having a diameter of 100 mm to press down the entire width of the material, thereby canceling out the edge waves. Furthermore, by adding a flanged flange roll (FIG. 3, 29), 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 has a female die 25 and the lower roll has a male die 26.
is provided in the desired shape described above. In the present invention, when formed into a square steel tube, the edge portion of the steel strip that becomes the upper side is bent by upper and lower rolls having a radius of curvature _R. For this purpose, the upper and lower rolls form caliber 27-1. . 29
Shows a flanged roll.

Generally used as a wrinkle presser during deep drawing of thin plates.
Although a blank holder is used, according to the findings of the present inventor, by simultaneously applying bending to the above-mentioned edge portions while embossing the steel strip, edge waves 34 are generated due to the tension caused by the embossing. However, by combining bending with rolls,
It has become clear that the wrinkles are eliminated and a groove free of welding defects can be obtained during butt welding, which will be described later.

According to the present invention, in addition to the above-mentioned bending process during embossing, by applying a light reduction (plate thickness x 10%) to the edge part of the steel strip using a flat roll, the tension caused by embossing is canceled out. This can solve the above-mentioned problem of edge wave formation. Therefore, it is necessary to perform embossing and rolling down the edge portion at the same time.

The embossed steel strip 11 is introduced into the rough forming roll 15A via the pinch rolls 13, but in the present invention, the drive system for rolling the embossed pattern and the drive system for roll forming are separate systems. By doing so, it is possible to solve the problem that the influence of embossing affects the forming roll.

That is, according to the present invention, the embossing roll drive system and the forming roll drive system are separated,
The rotation speed of the embossing roll is controlled so that the material speed is the same as that of the forming roll. Furthermore, a certain amount of loops are formed in the steel strip between the embossing roll and the forming rolls subsequent to the pinch rolls to prevent vibrations generated during embossing from having an adverse effect on the forming process. According to this method, embossing and roll forming are performed separately, so forming can be performed stably without being affected by material vibrations caused by embossing.

Once the embossing has been formed, it is introduced into the next step, a rough forming roll, where the top edge bending and side edge bending including the embossed surface are performed. Note that the rolls for the next and subsequent steps are assembled so as to avoid the sides on which the embossing is formed. As shown in FIG. 4, the upper corner bending roll 15-A
5-1 and a lower roll 15-2, the edge of the upper roll is formed with a caliber 27-2 having an upper corner bending radius of curvature R _B , and the edge of the lower roll is formed with a concave caliber 27-2. While giving the steel strip the desired curvature relative to the (hole shape), at the same time, when it is made into a square tube, the steel strip is bent to θ° _B = 60° ± 10° at the positions that should be the left and right upper corners. Has a bending profile. The radius of curvature R _B is smaller than the radius of curvature R _E added during embossing, and is preferably about (1 to 3) times the side length.

When the joint is welded, the steel strip is bent at a position 28 leaving widths L ₁ and L ₂ at both ends so as to have the length of the upper side of the rectangular tube. The bending position 28 is preferably a symmetrical position with respect to the roll center C. Next, the strip steel is introduced into the rough forming roll 15-B, and the corner bending angle β of the side including the embossed surface is bent by the upper roll and the lower roll to about 70° ± 10°,
It is roughly formed into a pentagonal cross-sectional shape with open vertices.

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 fin pass processing, the optimum upper side bending radius R _F is obtained for the purpose of stably butting both edges during the welding process. 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 (see Figures 6 and 9).

After each side of the square steel pipe has been preformed in this manner, it is subsequently introduced into welding rolls having a predetermined roll profile, subjected to electric resistance welding, and produced into a pipe. As shown in Fig. 7, the welding roll of the present invention is a five-sided roll squeeze, and the function of each roll is as follows.
Adjust the butt shape of the two upper rolls on the left and right. By adding a slight curvature R _SQ to the roll, stabilization of the butt can be achieved. The pair of left and right rolls also apply the necessary pressing force to the upset. Furthermore, it consists of a lower roll that acts like a safety valve to prevent the pipe material from escaping downward when pressure is applied by a pair of left and right rolls. , it is possible to obtain reliable welding quality.

The square steel pipe produced in this manner is shaped into the final cross-sectional shape using several stages of shaping rolls, and then cut into a desired length using a suitable conventional shearing machine to produce a product.

As described above, according to the present invention, square steel pipes can be produced at high speed by roll forming followed by embossing by roll forming, and the industrial effects are great.

[Brief explanation of the drawing]

Fig. 1a is a schematic diagram of a square steel pipe according to the present invention, b
2 is a schematic diagram of a cross section of a square steel pipe, FIG. 2 is an overall explanatory diagram of the present invention, FIG. 3 is a partial sectional view of an embossing roll of the present invention, FIG. 4 is a partial sectional view of a rough forming roll of the present invention, and FIG. FIG. 5 is a partial sectional view of another rough forming roll of the present invention, FIG. 6 is a partial sectional view of the fine pass roll of the present invention, FIG. 7 is a partial sectional view of the squeeze roll of the present invention, and FIG. 8a is a partial sectional view of the squeeze roll of the present invention. Schematic diagram showing the state in which edge waves are generated at the edge part due to elongation strain generated around the embossing, b is a schematic diagram of a steel strip, c is a partial diagram of b, d is a Y-Y cross-sectional view of c, e is a XX sectional view of c, and FIG. 9 is a chart of (upper side corner bending radius of curvature)/(plate thickness) in each forming process. 14: Embossing roll, 15: Rough forming roll,
23: Loop detector, 24: Speed detector, 30:
Emboss roll DC control drive system, 32: Forming roll DC control drive system, 34: Edge wave.

Claims (1)

[Claims] 1. In a method of obtaining a square steel pipe 31 having a welded seam on one side by embossing a steel strip 11 with a roll and performing roll forming, the steel strip is embossed and at the same time the edge of the steel strip is formed with a certain curvature. Bending is performed using a pair of upper and lower rolls with a radius, and the embossing roll drive system and forming roll drive system, which are independent of each other, are synchronously controlled.
A method for forming a square steel pipe with an embossed pattern, which comprises forming a certain amount of loops in a steel strip between an embossing roll stand and a forming roll stand.