JPS6125444B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously manufacturing predetermined square steel pipes by continuous welding.

As shown in Fig. 1, the continuous square steel pipe manufacturing equipment consists of coils 1 and 2 arranged in an inlet coil supply section that supplies materials constituting square steel pipes, and materials 3 and 4 from these coils 1 and 2. A delivery roll 5 for sending out to the welding part, a group of forming rolls 6 arranged between the coil supply part and the welding part, a pressure roll 7 arranged above and below the welding part, a contactor 8 for supplying a welding heat source,
It is composed of a cutting machine 9 that cuts manufactured square steel pipes to a fixed length, and transport rolls 10 for transporting the square steel pipes.

The coil materials 3 and 4 are unwound from the respective coils 1 and 2 so as to constitute upper and lower members based on the welding position in the cross section constituting the square steel pipe, and are sent out to the welding part by the delivery roll 5. The sent-out coil material is formed into a shape by the forming rolls 6 disposed on the transfer path so that both ends in the width direction face each other, and then a contactor is placed on the side near the joint. It comes into contact with a high-frequency current through a roller 8, and is heated by using the resistance heat generation as a welding heat source, and pressure welding is performed by a pressure roller 7. When welding steel strips that are shaped in opposite directions, if the weld is located at the corner of the square steel pipe, there will be problems with the strength of the steel pipe, so weld the weld at the middle of the side of the steel pipe. It's for a reason. In other words, when force is applied to the side of the steel pipe,
This is because stress is concentrated at the corners, so if a welded part with weak strength is located at a corner, it is likely to break. Therefore, the shaped steel strips are faced and the ends of two parallel sides are welded together so that the welding part is located in the middle of the sides. The square steel pipe manufactured in this manner is cut into a fixed length by a cutting machine 9 disposed downstream thereof, and transported to a predetermined location by transport rolls 10.

The manufacture of square steel pipes by such high frequency welding has various problems, unlike the case of H-beam steel which is similarly manufactured by high frequency welding.

First, a method for manufacturing H-section steel will be described, and then problems in the method for manufacturing square steel pipes will be explained.

As shown in FIG. 2, the H-section steel is made by contacting the flange material 11 and web material 12 unwound from a coil (not shown) with a high-frequency current via a contactor 8' before the welding part. After being heated using resistance heat generation as a welding heat source, pressure welding is performed by a pressure roll 7'.

In this case, the angle θ formed from the joining position between the end face of the web joining point and the web side surface of the upper and lower flanges 11 is generally called the angle of incidence, and is an important point in determining the quality of welding. This angle of incidence varies depending on conditions such as plate thickness and welding speed, but is usually set around 6°. This flange material 1
In order to obtain an incident angle of 1, a large bend is applied to the flange material 11 before the joint point, but since the flange material 11 is a smooth steel plate, an external force is applied within the elastic limit corresponding to the rigidity of the plate itself. It is possible to bend large bends with just the welding method, and therefore no residual stress is generated in the material after welding.

On the other hand, in the case of square steel pipes, both ends of the plates 3 and 4 in the width direction are formed into a shape, so the rigidity increases greatly, and the crimping roll 7 has to be increased in size accordingly. In addition, in order to obtain the same angle of incidence as in the case of H-beam steel, the end portion near the weld line will undergo elongation due to plastic deformation due to bending and unbending, resulting in waving. For this reason, there are problems such as it is difficult to make the joint surfaces forming the square steel pipe smooth after welding, and it is also impossible to correct the joint surfaces.

This invention was proposed to solve the problems in manufacturing the square steel pipe, and as shown in Fig. 5, the ends to be joined by welding are shifted upward or downward from the center line of the square steel pipe. As shown in Fig. 6, one side (upper side in the figure) is set to the minimum height that can be formed and bent, the other side (lower side shown in the figure) is made higher, and the ends of both forming and bending parts are welded to each other. Consists of two parallel sides of a square steel pipe. In addition, the welded portion is located in the middle of the side surface, away from the corner of the square steel pipe, and stress concentration on the welded portion can be avoided.

With this configuration, in order to obtain the above-mentioned incident angle when manufacturing a square steel pipe, as shown in Fig. 5, a large bend is applied to the material 3' on the side of the lower forming depth, and a large bend is applied to the material 3' on the side of the forming depth on the other side. Deep side material 4'
Enter the welding position in a straight line.

This invention has the above-mentioned configuration, and in order to bend a steel strip into a shape and weld the ends,
The welded part will be located in the middle of the two parallel sides of the square steel pipe. Therefore, stress concentration on the welded portion can be avoided, and a steel pipe with high strength and resistant to breakage can be manufactured.

In addition, the forming depth of one of the steel strips is made as low as possible, and the steel strip with a low forming depth is given a large bend to obtain the necessary angle of incidence. That is, since the height of the two sides to be welded is low, the influence of bending due to large bends is small, elongation due to plastic deformation is difficult to occur, and waving does not occur.

[Brief explanation of the drawing]

Figure 1 is a schematic perspective view of square steel pipe manufacturing equipment, Figure 2
The figure is a perspective view of a welded part of H-section steel manufacturing equipment, Figure 3 is a cross-sectional view taken along line ~ in Figure 2, Figure 4 is a cross-sectional view taken along line ~ in Figure 2, and Figure 5 is a method of the present invention. FIG. 6 is a sectional view taken along the line - in FIG. 5, and FIG. 7 is a sectional view taken along the line - in FIG. 5. 1, 2... Coil, 3, 3', 4, 4'... Coil material, 5... Coil delivery roll, 6... Forming roll, 7... Pressing roll, 8... Melting contact, 9
... Cutting machine, 10 ... Transport roll.

Claims (1)

[Claims] 1. In equipment that manufactures square steel pipes by bending both ends in the width direction of two steel strips constituting a square steel pipe into shapes that face each other and continuously joining the ends by high-frequency welding, forming the steel strip Sometimes, the forming depth of one of the two shaped cross sections that make up the square is made as low as possible, and the forming depth of the other is formed to the necessary forming depth to form both sides of the square steel pipe after welding. A continuous welded square steel pipe manufacturing method characterized in that a steel strip on the lower depth side is given a large bend to obtain the angle of incidence necessary for welding.