JPS6049812A - Manufacture of large-sized square steel pipe - Google Patents

Abstract

PURPOSE:To make a tack welding operation simple and efficient by previously cutting the end face of blank material so that a part of tack welding line of the face provided with a butt welding edge of the end faces in the longitudinal direction of the unit semiformed blank material is formed into a projecting shape with respect to the transferring direction of a steel pipe. CONSTITUTION:A unit semiformed blank material 13 having the cross section formed nearly into a square steel pipe is transferred in its longitudinal direction and the side edges in the longitudinal direction of the material 13 are butt welded to each other by the contactors 32 of a high-frequency welder through forming rolls 4 and squeezing rolls 31 after providing a tack welding to the front and rear end-faces 22 of material 13 to join the materials 13 in one body. At that time, as for the joining part of material 13, a notched part 25-1 is previously formed at the rear end-face provided with a butt welding edge of the preceding material 13, and also a projected part 25-2 is formed at the front end-face of the succeeding material 13 corresponding to the former to relax a clamping force acting on the tack welding part. In this way, the tack welding operation of the joining part can be remarkably cut down, and a breakage trouble of this part is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The method of the present invention relates to a method for manufacturing large diameter rectangular steel pipes, particularly (=techniques for improving processing efficiency in forming and welding processes).

Conventional technology When manufacturing small-diameter lightweight rectangular steel pipes, a band-shaped plate is bent at four locations in the longitudinal direction and welded and formed using a single weld line. Thickness 20rMl
When manufacturing large-diameter rectangular steel pipes with a cross section of 35 x 35 cm and a length of about 187 nm, there are many difficult problems such as bending (medium processing), (lh equipment investment is huge, and there are various problems in thick plate processing). Therefore, it was considered impossible to manufacture large-diameter square steel pipes from two sheets of steel.

Therefore, by butt welding the longitudinal side edges of two thick steel plates whose cross sections were bent into a cross-section shape,
Manufacturing method for forming large diameter rectangular steel pipes;
In this manufacturing method, two weld lines are formed on one steel pipe (2T, r"), which requires a lot of welding materials and processing costs (=, a lot of welding distortion occurs, and it is difficult to correct it. There are few inconveniences such as time consuming.

Recently, a band-shaped thick steel plate was cut into unit lengths,
The parts corresponding to the corners are bent four times along the longitudinal direction by press working, and the 1U square cross section in the longitudinal direction is formed into a semi-formed product with an external shape close to a half-open square, and then passed through a forming roller to form the required square shape. A technology has been developed to manufacture steel pipes by closing the opening side edges, butting and temporarily welding both side edges, and then gas welding the butted surfaces.

However, according to this manufacturing method, the welding process is not only complicated, but also requires beveling the ends, applying abutment metal to the inside, and welding the thick wall from both the inside and outside. , Due to the work process, there is a limit to the machining length,
It is necessary to perform processing for each unit length, and with this, it is not possible to maintain the angle of approach to the forming roller, and the final 1m of the weld may be defective, resulting in inconveniences such as cutting off. It is difficult to place the material on the surface, so improvement is needed in terms of machining efficiency.

In order to solve this problem, a unit thick steel plate is bent and formed into a half-open half-formed product whose longitudinal end face is nearly square, and then the cross section is shaped into the desired shape using a forming roller, squeeze roller, etc. In addition to shaping it into a rectangle, the opening and butt portions were welded continuously (double electric welding, for example by high frequency resistance welding means, and continuously butt welded).

According to the above-mentioned manufacturing method, continuous welding of steel pipes is possible (7), so after forming a unit of square steel pipe material into a semi-formed product (two parts), both longitudinal ends are temporarily attached to each other to form a continuous welding process. By forming a semi-molded product and sending it to the electric welding equipment described above, the angle of approach to the forming roller can be kept constant, making it possible to form a large diameter rectangular steel pipe in an assembly line.

The molded products are then made into final products one by one by not cutting off the welded ends of each temporary weld. By adopting this manufacturing method, it was possible to significantly improve molding and processing efficiency with a relatively small capital investment compared to the work capacity, and it was possible to reduce product costs. .

However, in the above-mentioned electric welding equipment, when the forming roller and the squeeze roller squeeze the steel pipe semi-formed product into a square cross section, a high-frequency current is applied to the position where the opening is closed, and the same side edges are mutually heated. Although the process includes butt welding of steel pipes, the wall of the steel pipe is
It receives the force of bending inward from each roller in turn. In other words, a steel pipe semi-formed product is subjected to a considerably large shearing force T (for example,
When a semi-formed product is being shaped by a squeeze roller, bending force is applied to the far side of the semi-formed product through the edge of the tack roller. Since force is generated, it is easy to use rx
When welding, the same part breaks during shaping, and the assembly process is interrupted.

(In other words, temporary welding between the end faces of the semi-formed product) is sufficient as long as the part concerned has the strength necessary to transport a long steel pipe material in its longitudinal direction. ,
When bending the four sides of the steel pipe material (unless it has enough strength to withstand the shearing force that occurs)
No.

For this reason, it is necessary to reliably and carefully weld the end faces of the material not only to the side with the high-frequency butt welded part, but also to the adjacent side parts, and this welding work requires a considerable amount of work time and materials. I needed it. This has restricted the efficiency of forming steel pipes by electric welding.

By the way, in this type of steel pipe manufacturing method, the external force applied to the rectangular semi-formed product from the shaping rolls, etc. is such that the side edges of the cross-sectional shape are folded inward around both corners of the lower side forming the steel pipe. It can be analyzed as adding the action of bending, the action of bringing the opening edges of the upper side closer to and abutting each other, and the action of shaping so that both pieces forming the upper side lie within one plane.

And, if a reliable connection is formed between the adjacent upper sides that resists the external force that brings the opening edges of the two sides closer together and abutting each other, it will be effective against other external forces as well. I understand. In this case, the rear end surface of the preceding semi-molded product is
It acts to narrow down the front end of the subsequent semi-molded product.

Therefore, among the end faces to be temporarily welded, those with high-frequency butt welds have sides that are convex in the direction of transport of the semi-formed product.
If they are shifted to form a row shape, when the rear end of the preceding semi-molded product is squeezed inward by forming rolls, the external force is transferred to the front end of the following semi-molded product through the in-row engagement. The above-mentioned rig shear force is injected.
The load is applied in a low shape, thereby making it possible to simplify the tack welding.

! Therefore, the manufacturing method of the present invention utilizes the above-described configuration to simplify and streamline the temporary welding of semi-formed products to each other, thereby facilitating the forming and forming of large-diameter rectangular steel pipes. The purpose is to improve the efficiency of welding processing, to ensure that tack welding works reliably even if there are some discrepancies in welding, and to reduce the incidence of non-standard products due to this, thereby reducing manufacturing costs. This is the purpose.

Structure The method for manufacturing a large diameter square steel pipe according to the present invention includes bending a unit strip-shaped thick steel plate at four locations corresponding to the corners along the longitudinal direction, and forming the cross section into a shape similar to that of a square steel pipe. Next, the pre-fertilized half-formed material is transferred in the longitudinal direction, and after the transfer direction of each unit half-formed material ☆T: The surface is temporarily welded to the front end in the transfer direction of the next unit half-formed material. In the manufacturing method of large-diameter square steel pipes, the cross-sectional shape of the steel pipes is formed into a predetermined square steel pipe, and the longitudinally opposite side edges are butted and electrically welded. Both longitudinal end surfaces of the strip-shaped thick steel plate are cut in advance so that the temporary raked line portion of the longitudinal end surface of the forming material on the surface with the butt welded edge forms a convex shape with respect to the transport direction of the steel pipe. A molding method characterized by leaving the mold in place.

One embodiment of the present invention will now be described with reference to the drawings.

fc, the manufacturing method of the present invention is described in Patent Application Publication No. 1121.28 of 1980 (Patent Application No. 19985 of 1978), which was filed by the patent applicant before this application, for manufacturing large diameter square steel pipes. Since this method is based on the method, we will briefly describe the method with reference to the explanation in the same publication for other details.

FIG. 1 is a schematic diagram of an apparatus for carrying out the above-mentioned basic method, and the process is shown in the drawing from left-hand side A to right, unwinding a steel plate 1 from a hot-rolled coil (thickness: 9 to 25 mm) 11. After straightening the bend by passing it through a leveler 15, it is cut into unit lengths (-about 181 nm) by a slitter 6, and transferred in the longitudinal direction by a transfer roller 10.
The width of the steel plate is regulated through the press machine, and then the unit steel plate is fed into a predetermined position of the press machine and the mold 31 is lowered to bend the square steel pipe at four positions corresponding to the four corners. The cross section thereof is molded to have a cross-sectional shape as shown in FIG. 2 to form a semi-formed steel pipe 13.

At this time, it is advantageous for the subsequent manufacturing process to bend each corner of the semi-molded product 13 as close to 90 degrees as possible, but when inserting and removing the mold 31 from the opening... The bending angle is larger than that.

I can't hope. In the cross-sectional view of the semi-molded product in Fig. 2, corner portion 1
Preferably, the angle A between 6 and 19 is about 92°, and the angle C between corners 17.18 is about 115°.

Returning to FIG. 1 again, this semi-molded product 13 is placed in the press machine 3.
A plurality of semi-molded products 13 are taken out, arranged in a longitudinal direction, and their end surfaces butted against each other, and the running tacking, which is installed on both sides of the transfer roller 10, is attached to the rear end surface of the preceding semi-molded product 13 by the pattern 7, and the front end of the subsequent semi-molded product 13. Temporarily attach the sides.

The tentative welding blades 7 reciprocate on the rails 8 disposed on both sides of the transfer roller 10, and while the semi-formed product 13 moves close to the forming roll 4, the tentative welding of the end faces to each other is completed. If not, rz et rf. Semi-molded product 1 after tacking is completed
3 is fed into the welding machine while being pressed from below by forming rolls 4, etc., and is successively bent step by step by rollers on both sides, so that the angle C of corner 17, 1B is 90°.
Step 7: The open end sides of the plates are butted together and sent to the high frequency welding machine 5, where the entire thick plate is welded at once, completing the process in one step.

Since high-frequency welding means is adopted, consumable materials such as welding rods are not required, and there is less distortion due to welding. 7
Furthermore, since there is no need to prepare a groove on the butt welding surface, the process can be easily simplified.

fC Oh, this welding may be high frequency induction welding or high frequency resistance welding. In this way, we were able to improve the welding method to be suitable for continuous processing, and the tacking of the front and rear end surfaces of unit semi-formed products was welded continuously using a welding machine. Further, the rectangular steel pipe 5 formed into a predetermined shape is sent out by a transfer roller 1o, and a traveling cutting machine 26 installed on the side thereof cuts off the temporary part. The excess thickness of the welded part of the can opening of the unit molded product is scraped off, sent to a strain relief roller 9 to correct distortion mainly in the length direction, and then passed through an inspection device such as an ultrasonic flaw detector @ 20 to the finished product 3o. .

In the manufacturing method of square steel pipes consisting of the steps described above, there is the disadvantage explained in the previous section of the prior art in the processing step of the traveling tacking machine 7.In the manufacturing method of the present invention, this tacking is done by welding. This is related to the method, and if this method is followed, the parts will not break even if the tack welding is not done as reliably and carefully as in the past, and there may be slight defects in the welding. Since it functions reliably even when using a high-frequency welding machine, it is possible to greatly reduce the amount of welding work, and the processing efficiency of the high-frequency welding machine can be improved accordingly.

FIG. 3 is a schematic view of the half-molded product 13 under molding immediately before being fed into the high-frequency welding machine 5, viewed from the side with the opening, usually from above. 25-1 is a concave cutout in the center of the side including the high-frequency butt welding part on the rear end face of the preceding semi-molded product 13, and 25-2 is a notch for the subsequent semi-molded product. 13, the central part of the side including the high-frequency butt weld part is protruded in a convex shape, and is a convex part that perfectly fits into the notch part 25-1,
Examples include 5 to 10 protrusions or notches.

When both sides of the preceding semi-formed product 13 are tightened by the forming roller 4 and the squeeze roller 31, and the opening width of l narrows, the pressing force is applied from the rear end surface to the subsequent semi-formed product via the temporary attachment part 22. Tightening is transmitted as force to the front end of the product,
At this time, a large fc cutting force will be applied to the welded part 22 during temporary attachment, but the in-low structure due to the fitting of the protrusion and notch 25-1. As a result, the stress in the temporary welding part 22 is reduced to a large 11%, and the temporary welding of this part eliminates the need for careful and reliable processing as in the prior art.

31 is the above-mentioned squeeze roller for high-frequency butt welding, which is located downstream of the contact 32 of the high-frequency welding machine in the direction of conveyance of the steel pipe blank, and closes the upper opening of the semi-formed product 13 and butts it. A high-frequency current is passed through the contacts from the contacts on both sides to heat and melt them, and then pressure is applied to butt weld them all at once. The arrow indicates the direction of transport of the semi-molded product.

FIG. 4 is a perspective view of the longitudinal end face of the semi-molded product, in which (a) is the rear end face of the preceding semi-molded product 13;
1 is a notch that is a part of the side that has an opening, and its (
b) is the front end surface of the succeeding semi-molded product 13 in the transport direction;
-2 is a convex part that protrudes from a part of the side that has the opening,
Its shape is large enough to fit into the notch 25-1 as is. The inward bending stress of the side edges of the semi-formed product by the forming roller 4 etc. becomes a tightening force, and the temporary attachment is performed at the connecting portion 22.
At the location, the uneven portion 25-+ is formed.

Most of the information is transmitted through the 25=2 fitting structure. For this purpose, the length of the protrusion or notch between the two in the longitudinal direction is sufficient to be approximately 5 to 10 I+II++.

Effects As described above, according to the manufacturing method of the present invention, the conventional work of temporarily attaching unit semi-molded products to each other can be omitted to a minimum, and in extreme terms, it is possible to omit the work necessary for passing high-frequency current. As long as the working time does not restrict the efficiency of the high-frequency welding process, [the tack bonding will prevent parts from breaking and will ensure reliable forming process. It can be applied stably and efficiently, and there is no need to worry about welding defects occurring at the edges of unit products.

Further, the uneven shape of the longitudinal end of the unit material is obtained by forming the blade of the slitter 6 into a convex shape when the steel plate is pulled out from the roll material 11 and cut into the steel plate 1 of unit length by the slitter 6. This prevents material from being wasted due to notches.

By doing this, the amount of capital investment can be reduced compared to the amount of processing and work efficiency, and it is possible to manufacture competitive large-diameter square steel pipes with stable quality.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the basic equipment for carrying out the method for manufacturing large-diameter square steel pipes of the present invention, and Figure 2 is a semi-formed square steel pipe whose corners are bent and formed using a press machine. 3 is a cross-sectional view of the product, and FIG. 3 is a schematic plan view illustrating the molding process and feeding the semi-molded product into a high-frequency welding machine, and FIG. This is a perspective view of the end face of the molded product, in which (al) is the rear end face of the preceding semi-molded product, and (b) is the front end face of the subsequent semi-molded product. 4... Forming roller 13... Large-diameter square steel pipe semi-formed product 14...Molded product 22...Temporarily attached part 25-+
, 25-2...Notch, protruding portion 31...Squeeze roller 32...Contactor representative of high frequency welding machine Patent attorney Nagai 1) Hiroshi -

Claims (1)

[Claims] A unit of band-shaped thick steel plate is bent at four locations corresponding to the corners along the longitudinal direction, and its cross section is formed into a shape similar to a square steel pipe.Then, the half-formed plate is transferred in the longitudinal direction to form each piece. After temporarily welding the rear end surface of a unit half-formed material in the transfer direction and the front end surface of the next unit half-formed material in the transfer direction, the cross-sectional shape is sequentially made into a predetermined square steel pipe. 2. A belt-shaped thick plate is formed in advance so that the longitudinally opposite side edges are abutted and the temporary raked line part of the surface with the welded edge forms a convex shape with respect to the transport direction of the steel pipe. A forming method characterized by cutting and placing both longitudinal end faces of a steel plate.