JPS5953126B2 - Manufacturing method of large diameter square steel pipe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for manufacturing large diameter rectangular steel pipes for use in construction and other purposes.

Conventionally, large-diameter square steel pipes used for construction and other purposes are manufactured by bending two steel plates into a U-shaped cross section, then butting them together and welding them to form a square steel pipe.

In this method, two weld lines are created in one steel pipe, so welding materials and welding work account for a large portion of the steel pipe cost, and a considerable amount of strain relief work is required in conjunction with welding. This has become an obstacle to reducing the manufacturing cost of steel pipes.

In the case of small-diameter steel pipes, a single plate is bent and welded with a single welding line, but usually 350rn
In the case of large-diameter steel pipes of m x 350 mm or more, there are many problems in bending and other aspects, and for this reason, it was considered practically impossible to manufacture large-diameter steel pipes from a single plate.

In addition, in the conventional method, two steel plates are beveled.

Bending Process 9 It is difficult to make the process continuous because it involves many different processes such as joining the two parts together, tacking, welding, and removing distortion.As a result, it is also time-consuming to transfer parts between processes. The percentage of production costs reached a considerable amount.

In order to solve such problems, the present inventor previously proposed a method of manufacturing a large square steel pipe from a single steel plate, but the following problems remain with that method.

In other words, since the material is made from a single steel plate cut to a predetermined size, it is necessary to change the dimensions of the material each time the length of the steel pipe to be manufactured changes, and the work must be interrupted. Furthermore, since welding is performed by submerged arc welding, it is necessary to weld from the inner surface of the steel pipe, and bevel processing is also required, so that the work cannot be said to be sufficiently simplified.

In view of these points, the present invention aims at further simplifying the work in a method of manufacturing a large diameter rectangular steel pipe using a single steel plate.

The present invention is a method for manufacturing a large-diameter square steel pipe, in which a steel plate is pulled out from a coil of steel plate material, and after removing the strain with a leveler, it is sequentially cut into a certain length, and both sides are trimmed, and the four corners of the square steel pipe are pressed using a press. The position corresponding to the shape is bent to form a shape similar to that of a square steel pipe, and then, while being transferred in the length direction, at least butt-matching is performed between the rear end in the transport direction and the front end of the next molded product. The tack welding is carried out using a traveling tack welding machine at the points adjacent to the section, and then the connected parts are sequentially pressed from the outside with rollers into the shape of a rectangular steel pipe and transferred in the length direction by high-frequency welding. The abutting portions in the length direction are welded, and then the tacking portions are separated using a traveling cutting machine, and then the strain is removed using a strain relief press or a roller.

Hereinafter, the present invention will be explained with reference to drawings of embodiments.

In the material supply section, the steel plate 1 is pulled out from the coil 11 of the steel plate material and is passed through a leveler 15 to straighten the bend.

Next, the continuous steel plate 1 is cut into a predetermined length by the shearing machine 6, and while being fed in the length direction by the transfer roller 10,
The cutting machine 2 is used to align both sides.

The steel plate 1 cut to a predetermined size is fed into a press 3 by a transfer roller 10, where bending is performed at portions corresponding to the corners of the square steel pipe.

In this forming process, as shown in FIG. 2, the corner 16 of the steel plate 1 is bent at a predetermined angle, then the corner 17 is bent, then the corner 19 is bent, and finally the corner 18 is bent.

The degree of this bending process is such that the angle A between corners 16 and 19 is 92°.
, the angle C between the corners 17 and 18 is preferably 115°.

Through this forming process, a cross-sectional shape similar to that of a rectangular steel pipe is obtained as shown by the solid line in FIG.
The upper part is sent sequentially in the length direction.

At this time, the running tackifiers disposed on both sides of the transfer roller 10 tack the front end of the following molded product 13 to the rear end of the preceding molded product 13 by means of the tacking machine 7 .

This temporary attachment may be performed in the region 25 at the end of the upper side, as shown in FIGS. 2 and 3.

For temporary attachment of this part, the upper sides of the front and rear molded parts must match perfectly in order to weld, so if there is a difference between the two, adjust it to make the two match. The running tacking means, for example a pressing roller from the side or the top, may be provided on the machine 7 or may be provided separately.

The traveling tacking machine 7 reciprocates on the rails 8 placed on both sides of the transfer roller 10, welds the tacking while traveling with the molded product 13 close to the forming roll 4, and then welds the tack with the following molded product. It is configured to return to the joint portion 22 and repeat the same operation.

Therefore, the molded product 13 is connected to the molding roll 4 and fed thereto.

Here, while being pressed and fed by rollers from above and below, it is pressed down step by step by rollers on both sides, and the corners 17, 1
Welding is sequentially performed by the high-frequency welding machine 5 with the angle of 8 being 90° and both ends of the steel plates butted together.

In this welding, welding is done over the entire thickness of the plate, so
Welding from the inside is not required, so welding is completed in one step.

Moreover, in the case of high frequency welding, unlike conventional submerged arc welding, etc., since no weld metal is used, the amount of heat applied is small, and the distortion that occurs in the product can be reduced.

Furthermore, since beveling is not required, the process can be simplified.

Note that this welding may be performed using either high-frequency induction welding or high-frequency resistance welding.

In addition, since the molded parts are connected sequentially in this welding process, it is possible to weld multiple molded parts in succession without interrupting welding for each molded part, thus increasing the welding speed. can.

However, in the welding process, it took a considerable amount of time to start and stop welding each time a molded product was sent, but by connecting molded products as described above, multiple molded products can be processed in one pass. By doing this, it is possible to save time for starting welding and cutting each molded product.

In addition, when welding each unit molded product, unweldable or defective parts may occur at the welding start and end ends, resulting in wasted material and deteriorating product quality. According to the method, both of these deficiencies can be improved.

The molded product 14, which has been welded into a predetermined steel pipe shape, is sent out by the transfer roller 10, and the temporary attachment portion 25 is cut by a traveling cutter 26 disposed on the side thereof.

Then, for each unit molded product, the welded part 23 on the outer surface is
After cutting off the excess thickness and making it smooth, it is sent to the distortion correction device 9,
Here, distortions mainly in the longitudinal direction are corrected using a press or a roller.

Next, the molded products 14 are sent by a transfer roller 10, and after passing through an inspection device 20 such as an ultrasonic flaw detector to inspect the welded parts, they are arranged as finished products 30.

As explained below, the present invention continuously draws out steel plates from a coil of steel plate material and continuously manufactures a rectangular steel pipe having only one weld line from one steel plate. It has many effects such as:

That is, first of all, the amount of welding is halved compared to the conventional two welding lines, so the welding work is significantly reduced, and in particular, since the present invention uses high frequency welding, it is difficult to process the groove and the inner surface of the steel pipe. There is no need for additional welding, and therefore the distortion caused by welding is small, making it easier to eliminate distortion and simplifying the process.

Furthermore, since each process is carried out continuously from the raw material to the finished product, it is possible to eliminate transfers between processes and other operational irregularities, and therefore, the number of workers can be reduced and mass production can be carried out efficiently.

Furthermore, since the present invention performs welding continuously, there is no loss of work time due to interruption and restart of welding, and the disadvantages of this, such as wasted material and quality deterioration due to poor welding at the start and end of welding, are improved. Moreover, the time of the whole process can be shortened.

This is a great advantage especially when the length of the molded product is short.

Because of this rationalization in various aspects, rectangular steel pipes can be manufactured at a very low cost, and are of great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an apparatus for implementing the present invention, FIG. 2 is a cross-sectional view of a steel plate in a state of bending, and FIG. 3 is a perspective view of a joint of a molded product. DESCRIPTION OF SYMBOLS 1... Steel plate, 3... Press, 5... High frequency welding device, 6... Cutting machine, 7... Traveling tack attachment machine, 10...
・Transfer roller, 11... Steel plate coil, 25... Temporary attachment part, 26... Traveling cutting machine.

Claims (1)

[Claims] 1. In the method of manufacturing large-diameter square steel pipes, steel plates are pulled out from a coil of steel plate material, and after removing strain using a leveler, they are sequentially cut to a certain length, and both sides are trimmed, and then a press is used to cut the steel plates into pieces corresponding to the four corners of the square steel pipe. The position is bent and formed into a shape approximating a square steel pipe, and then, while being transferred in the length direction, at least the butt portion between the rear end in the transfer direction and the front end of the next molded product is formed. The tack welding is carried out using a machine that travels between adjacent parts, and then this connected product is sequentially pressed from the outside with rollers so that it takes the shape of a rectangular steel pipe, and while being transferred in the length direction, it is welded to length using high frequency welding. After welding the butt parts in the horizontal direction and then cutting off the tacked parts using a traveling cutting machine,
A method for producing a large diameter rectangular steel pipe characterized by removing strain using a strain relief press or rollers.