JPS5911387B2 - Square steel pipe manufacturing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for manufacturing square steel pipes used for construction steel frames and the like.

When square steel pipes are used for the steel frame of steel-framed or steel-framed reinforced concrete structures, they are effective in reducing the weight of the structure, increasing the effective floor area of the building, and reducing construction costs. Structures using square steel pipes are gradually increasing.

Conventionally, this type of square steel pipe was manufactured by welding two steel plates bent into a U-shape butted together.
Since this method increases the welding length and increases the manufacturing cost, recently, a single steel plate is press-formed to form the required square steel pipe 20 with a slightly open seam as shown in Figure 1.
A method for producing a single piece into a square steel pipe by forming a workpiece 1 with a cross-sectional shape approximating that of Similar to the production of sewn steel pipes, a steel plate wound into a coil is formed into a circular cross-section from one end, the seam is high-frequency welded to form a circular pipe, and then the required square cross-section is formed using forming rolls using a continuous manufacturing method. began to be manufactured. For seam welding in the former single-item production, submerged welding has conventionally been generally used for the reasons described below. As is well known, submerged welding has a faster welding speed than ordinary manual welding, but is much slower than high-frequency welding. Therefore, endless manufacturing using a continuous manufacturing method is much better in terms of production efficiency, but continuous manufacturing requires a long production line, requires a very large factory area and site, and requires a large initial investment. There is a drawback that the forehead becomes an art school. Now, when applying high frequency welding to the manufacture of single-piece square steel pipes, there are problems as described below.

When high-frequency welding the seam of a workpiece 1 having the cross-sectional shape shown in FIG. 1, conventionally several sets (two sets in the figure) of forming rolls 3, 4 are placed upstream of the welding point 2, as shown in FIG. By running the workpiece 1 between these forming rolls, the gap at the seam opening of the workpiece 1 is gradually narrowed, and the squeeze roll 5 as the final stage of the forming rolls is used to create a regular shape. Form to the dimensions of. The seam forming edge 1a of the workpiece 1 is pre-applied with an offset amount u of several u, and when it is pressed down to the regular size with the squeeze roll 5, the above-mentioned offset amount u is crushed and the defective part of the end surface becomes the base material. It protrudes on both sides of the seam, and the base materials on both sides of the seam are completely pressed together. At least the outer surfaces of the protruding portions on both sides of the base material are scraped off with a bead cutter (not shown). The welding start point 2 of high frequency welding is very slightly upstream from the position of the squeeze roll 5, and is the contact point between the base materials on both sides where the offset amounts u on both sides begin to bite into each other.

One contact chip 6, 6' is provided to contact the upper surface of the seam forming edge 1a of the base metal on both uncontacted sides upstream of the welding point 2, and a high frequency current is passed between them. As a result, the current flows along the seam forming edge 1a of the workpiece 1 through the welding point 2, thereby heating the portion through which the current flows. Since the workpiece 1 is traveling at a constant speed in the direction shown by the arrow 7 in the figure, a point on the seam forming edge 1a of the workpiece 1 is located at the contact tip 6 or 6'.
This point is heated to a certain suitable welding temperature from the point of contact to the welding point 2, and as mentioned above, the offset amounts bite into each other and the base metals on both sides, which are closely pressed and welded, are completely high-frequency welded. Before starting welding of the front end of the workpiece 1, the front end of the workpiece 1 is first moved so that the base material on both sides of the seam, which has been pressed down to the regular size by the squeeze roll 5, maintains a predetermined approach angle θ. As shown in FIG. 2, it is necessary to set the squeeze roll 5 so that it protrudes by a considerable amount a on the downstream side, and then tighten the forming rolls 3, 4 and the squeeze roll 5 to a predetermined position. From this state, the workpiece 1 starts traveling, and at the same time the contact tips 6, 6
' Even if a current is applied between
Since the time required for the seam forming edge to reach the welding point 2 is shorter than the predetermined heating time, the seam forming edge formed at the portion b between the contact tip 6 and the contact tip 6, 6' is insufficiently heated, resulting in a defective weld. Therefore, in the above-mentioned device, it is inevitable that a welding defect will occur at the front end of the workpiece 1, which is at least the sum of the above-mentioned protrusion amount a and the distance b from the squeeze roll to the contact tip. It is necessary to set the front end of workpiece 1 by a distance a from the squeeze roll, then tighten each roll to a predetermined position, and then run workpiece 1.
Ivy.

When manufacturing rectangular steel pipes continuously from the above-mentioned time loss and material loss & ζ coil, the ratio to the whole is small and there is no problem, but when manufacturing a single item, the loss ratio becomes large and it is extremely inconvenient. This was the reason why high frequency welding was not used to manufacture single square steel pipes.

In order to improve this point, the present inventors have made it possible to open and close at least a part of the rolls 3, 4, and 5 while the workpiece 1 is running, as shown in FIG. We have previously proposed a square steel pipe manufacturing device that is equipped with an auxiliary squeeze roll 8 on the upstream side that can also be opened and closed while the workpiece is running. As a result, the workpiece 1, which is formed into a cross-sectional shape with an open seam, is inserted between the open rolls 3, 4, 8, and 5 while running, and as soon as the tip of the workpiece passes through, the workpiece By sequentially tightening each roll to a predetermined position while the workpiece 1 is traveling, the seam forming edge is pressed at the welding point, and the welding process begins while the workpiece 1 is traveling. People can. At this time, the workpiece 1 is
Since the seam forming edges on both sides of the workpiece 1 can be brought into contact at a predetermined welding point 2 at a predetermined advance angle θ when the tip of the workpiece 1 enters, there is no need to protrude only by a as in the conventional case.
When the front end of the workpiece comes into contact with the welding point 2, it is possible to start energizing between the contact tips 6 and 6'. Therefore, the number of welding defects at the front end of the workpiece can be reduced by at least a compared to the conventional method, and material loss and time loss are significantly improved compared to the conventional method. However, when electricity starts, welding point 2 (contact point) and contact tip 6,
seam forming edge 1 of workpiece 1 in the range l between
Since the heating time in a is shorter than the predetermined time, the welding temperature does not reach the appropriate welding temperature, resulting in a welding defect area.

As a countermeasure for the above, seam forming edges 1a on both sides of the workpiece 1
By providing a welding tab-shaped conductive plate at the front end of the welding point 2, it is possible to bring the conductive plate into contact and heat the conductive plate before the original tip of the workpiece 1 comes into contact with the welding point 2, but if the tab is too long, Then, depending on the thickness of the board, the tabs on both sides will be connected to each other. There is a high possibility that the desired purpose cannot be achieved because the tabs may be misaligned like force beaks or may be deformed depending on the pressing force of the tabs on both sides.

The object of the present invention is to provide a square steel pipe manufacturing apparatus in which there are no or almost no weld defects occurring at the tip of the workpiece, as described above in the conventionally proposed square steel pipe wandering apparatus using high frequency welding. do.

Hereinafter, the present invention will be described in detail based on drawings showing embodiments thereof.

As shown in FIGS. 4 and 5, in the square steel pipe manufacturing apparatus according to the present invention, the positions of the contact tips 6, 6' on both sides and the welding point 2 of the previously proposed apparatus explained in FIG. along the seam forming edge 1a of the work 1 so that the generally letter-shaped portion formed by the seam forming edge 1a of the work 1 between the contact tips 6, 6' abuts the surface of the work base material on the opposite side. A conductive member 10 is provided having a letter-shaped inner edge 10a.

The V-shaped inner edge 10a4ζ of the conductive member 10 is provided at a position several u back from the seam forming edge 1a of the workpiece 1. As shown in detail in FIG. 5, in the conductive member 10, a conductive part 11 that directly contacts the inner surface of the workpiece 1 is brazed to a V-shaped conductive part support member 12, and the support member 12 has an axis around its center. 13 so as to be able to swing by a slight angle with respect to the mounting member 14, and the vicinity of both front and rear ends are supported by the mounting member 14 via compression springs 15.

The attachment member 14 is attached to the upper end of a lifting device, for example, a hydraulic or pneumatic cylinder 17, which is attached to an arm 16 inserted into the interior of the workpiece 1 from the main body of the manufacturing apparatus through the seam opening of the workpiece 1. The conductive part 11 is made of a good electrical conductor having the same heat resistance and wear resistance as the contact chips 6, 6', and the conductive part support member 12 is made of a good electrical conductor such as copper.

The support member 12 and the mounting member 14 are electrically insulated by, for example, placing an insulator sleeve 18 over the shaft 13 and sandwiching an insulator plate 19 between the spring 15 and the support member 12. This device is configured as described above, so
When the workpiece 1 is inserted into the device, the front end of the workpiece 1, which has been advanced by the forming rolls to almost a predetermined advance angle as shown in FIG.
, 6' (a position l upstream from the welding point 2), the contact chips 6, 6' are brought into contact with the upper surface of the workpiece 1, and at the same time, the lifting device 17 is activated to lift the conductive member 10. It is raised and brought into contact with the lower surface of the seam forming edge of the workpiece 1. Since the conductive part support member 12 is mounted so as to be able to swing at a certain angle around the shaft 13 provided on the mounting member 14, the upper surface of the workpiece 1 is slightly inclined with respect to the horizontal during the process of being formed by the forming rolls. The upper surface of the conductive part 11 and the inner surface of the work 1 are in complete contact with each other even when the conductive part 11 is in contact with the inner surface of the work 1. As described above, when the contact chips 6, 6' and the conductive member 10 are brought into contact with the workpiece 1 and a high-frequency current is applied at the same time, the current flows from one contact chip 6 to the workpiece base material 1, the conductive member 10, and the other workpiece. Contact tip 6'-
．． It flows.

Then, as shown in FIG. 8, the seam forming edge 1a of the work 1
When the conductive member 10 and the workpiece 1 overlap to some extent, the current flows through both the workpiece 1 and the conductive member 11 at points 4 and 6, as shown in FIG.
If the flow is as follows, the workpiece 1 will not be heated as required. However, in this device, the v of the conductive member 10
Since the inner edge 10a of the letter shape is located at a position slightly set back from the seam forming edge 1a of the workpiece 1, in the area where the workpiece 1 and the conductive member 10 overlap, the current flows selectively to the protruding end face. Due to the characteristics of the high-frequency current, only 4 currents flow through the seam forming edge 1a of the workpiece 1, and there is no Φ current flowing through the conductive member 10, and at the tip of the workpiece 1, the current transfers to the conductive member 10 that has receded slightly and reverses. It will flow to the side seam forming edges. Therefore,
The seam forming edge 1a of the workpiece 1 is heated with a predetermined current for a predetermined time until it reaches the welding point 2. When the tip of the workpiece 1 reaches the welding point 2 and the left and right seam forming edges 1a come into contact, current flows directly between the workpiece base materials, and the mission of the conductive member 10 ends here.
Therefore, by lowering the conductive member 10 using the lifting device 17 and separating it from the workpiece 1, unnecessary wear of the conductive part 11 can be prevented. Since the conductive part support member 12 and the mounting member 14 are electrically insulated, current is prevented from flowing to other parts and causing sparks.

As described above, according to the present invention, it is possible to eliminate or almost eliminate welding defects at the tip of the workpiece with a simple configuration without affecting work efficiency, etc. It has a remarkable effect on improving the economic efficiency of manufacturing.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of the workpiece before welding the seam, Figure 2
Figures 3 and 3 are plan views showing examples of conventional devices, respectively;
FIG. 4 is a plan view showing an embodiment of the present invention, FIG. 5 is a side view thereof, FIGS. 6 to 8 are plan views explaining the operation of the embodiment of the present invention step by step, and FIG. 9 FIG. 2 is a schematic diagram illustrating how current flows through the conductive member of the present invention and the workpiece that comes into contact with the conductive member. DESCRIPTION OF SYMBOLS 1... Workpiece, 1a... Seam formation line, 2... Welding point, 3, 4, 5, 8... Forming roll, 6, 6'...
・Contact chip, 10... Conductive member, 10a...
・Inner edge of conductive member.

Claims (1)

[Scope of Claims] 1. After forming a steel plate into a cross-sectional shape approximately similar to a predetermined square steel pipe with an open seam, the steel plate is inserted into a forming lawn from the front end and run on both sides to form a seam. The edges of the base metal are formed into a predetermined cross-sectional shape by maintaining a constant approach angle to the welding point, and at the same time, the contact tip contacts the edges of the base metal on both sides on the upstream side of the welding point. In a square steel pipe manufacturing apparatus that heats the seam forming edges of the base metal on both sides by passing a high-frequency current between them, the seam is welded by high-frequency resistance through the welding point. along the seam forming edge of the base material so as to abut the surface of the base material opposite the contact tip in a generally V-shaped portion formed by the seam forming edge of the base metal between the location of the contact tip and the welding point. A square steel pipe manufacturing apparatus characterized in that a conductive member having a V-shaped inner edge is provided so as to be able to come into contact with and separate from a surface of a base material. 2. The square steel pipe manufacturing apparatus according to claim 1, wherein the V-shaped inner edge of the conductive member is located at a position slightly set back from the seam forming edge of the base material.