JPS6011594B2 - 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 as the steel frame of steel-framed or steel-framed reinforced concrete structures, large-diameter steel pipes can be used to reduce the weight of the structure, increase the effective floor area of the building, and reduce construction costs. Structures using square steel pipes are gradually increasing.

Conventionally, this type of square steel pipe was manufactured by butting two steel plates bent into a U-shape and melting them, but this method requires a long welding length and increases manufacturing costs, so recently it has been As shown in Fig. 1, a sheet of steel plate is pressed and formed into a workpiece 1 with a cross-sectional shape approximating the required square steel pipe 201 with a slightly open seam. After temporarily attaching the seam portion 21, the seam is welded to produce a square steel pipe.The method also involves manufacturing an open-seam steel pipe.A steel plate wound around a coil is formed from one end into a circular cross section. It has come to be manufactured using the Rentsugi manufacturing method, in which a round tube is welded and then formed into a desired square cross section using forming rolls. Submerged welding is generally used for seam welding in the former case of single-piece production, and high-frequency welding is used in the latter case of continuous production.

As is well known, submerged welding has a faster welding speed than ordinary manual welding, but is much slower than high-frequency welding. If we compare the speed numerically, submerged welding is 1 to 2 meters per minute, while high frequency welding is 20 to 20 meters per minute.
Up to 30 enemies. However, when high-frequency welding is introduced into the production of single-piece square steel pipes, there are problems as described below. When welding the seam part of a workpiece 1 having the cross-sectional shape shown in FIG. 1 by high-frequency welding, conventionally, as shown in FIG. By providing the rolls 3 and 4 at appropriate intervals and running the workpiece 1 between these forming rolls,
The gap between the closed seam portion of the workpiece 1 is gradually narrowed, and the workpiece 1 is formed into a regular size by a squeeze roll 5 as the final stage of forming rolls. The seam forming green of the workpiece 1 has an upset amount u of several ribs attached in advance, and when it is pressed down to the regular size with the squeeze roll 5, the upset amount u is crushed and the defective part on the end surface is formed. It protrudes from both sides of the material,
The base material on both sides of the seam should be completely pressed together. At least the outer surface of the protruding portions on both sides of the base material is cut off using a pide cutter (not shown). The welding start point 2 of high frequency welding is very slightly upstream from the position of the squeeze roller,
This is set at a point after the upset amounts u on both sides begin to bite into each other.

One contact tip 6 is provided in contact with the seam forming green on both sides of the wire contact on the upstream side of the welding start point 2, and a high frequency current is passed between the contact tips on both sides through the workpiece. As a result, the current flows along the seam-forming edge of the workpiece through the welding start point 2, thereby heating the area through which the current flows.

Since the workpiece 1 is traveling at a constant speed in the direction indicated by the arrow 7 in the figure, the welded part of the workpiece is heated to a constant appropriate temperature while the welded part of the workpiece reaches the welding start point 2 from the position where it contacts the contact tip 6. As mentioned above, the upset amounts on both sides bite into each other and the base metals on both sides are tightly pressed together and 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 in order to maintain a predetermined approach angle a of the base material on both sides of the seam, which has been pressed down to the regular size with the squeeze roll 5. As shown in Fig. 2, after setting the squeeze roll 5 so as to protrude by a considerable amount a on the downstream side, the forming rolls 3, 4 and the squeeze roll 5 are set.
It is necessary to tighten it to the specified position.

Even if the workpiece 1 starts traveling from this state and current is applied to the contact tip at the same time, the seam forming green in the part b between the squeeze roll 5 and the contact tip 6 reaches the welding start point 2 at the start of traveling. Since the heating time is shorter than the predetermined heating time, heating becomes insufficient, resulting in defective welding.

As described above, in the conventional apparatus, it is inevitable that a welding defect will occur at the front end of the workpiece 1 at least as much as the sum of the protrusion amount a and the distance b from the squeeze roll to the contact tip.

In order to maintain the approach angle of the seam forming edges of the base metal on both sides at the welding starting point 2 at an optimal constant angle of 8', the third
As shown in Figures 2 and 4, a seam guide roll 8 having tapered sides on both sides of the periphery is installed at a position a suitable distance c away from the welding point 2 upstream, and the lower end of the roll is placed just as the bicycle tire is touching the soft ground. Insert the tapered part into workpiece 1 so that the
By inserting a certain amount into the opening □ of the seam,
The width of the seam opening in that area is regulated.

However, if the rear end of the workpiece 1 comes off the seam guide roll 8, the normal approach angle cannot be maintained, so complete melting cannot be expected in the length c of the rear part of the seam. If the seam guide roll 8 is placed as close to the welding start point 2 as possible, the welding defect at the rear end of the workpiece c
The length of the seam guide roll 8 can be reduced.
When the contact tip 6 approaches the contact tip 6, a portion of the current flows through the seam guide roll 8, thereby inhibiting the heating effect on the base material of the weld. The seam guide roll 8 is not often made of an insulating material other than metal due to its strength and brittleness. As described above, in the conventional square steel pipe manufacturing equipment using high frequency welding, the tip of the workpiece is set so as to protrude considerably from the squeeze rolls before starting the welding process, and then each roll is tightened to a predetermined position and the workpiece is run. In addition, it was inevitable that a considerable length of defective welding would occur at both the front and rear ends of the workpiece.

The above-mentioned time loss and material loss are not a problem when manufacturing rectangular steel pipes from coils continuously, as their proportion to the whole is small, but when manufacturing a single item, the loss ratio becomes large and extremely It is uneconomical, and this is the reason why high-frequency welding is not used to manufacture single square steel pipes.

However, continuous manufacturing requires the largest production line;
The disadvantage is that it requires a very large factory area and site, and the initial investment amount is extremely large. In view of the above-mentioned problems of conventional square steel pipe manufacturing equipment, this invention minimizes the length of defective welds when manufacturing square steel pipes by high-frequency welding, and reduces the downtime of the workpiece, thereby improving the quality of the material. The purpose of the present invention is to provide a rectangular steel pipe manufacturing device that has little loss, is capable of high-speed processing, and is economical even when manufacturing single items.

Hereinafter, the present invention will be explained in detail with reference to drawings showing embodiments thereof.

As shown in FIG.
Provided with a squeeze.

A welding start point 2 is provided very slightly upstream of the point narrowed down to the regular product dimensions by the squeeze roller 5, and contacts are provided at positions contacting the seam forming edges on both sides, separated by a distance b upstream from the squeeze roller 5. The provision of the chip 6 is similar to the secondary device described with reference to FIG. However, the rolls 3, 4, and 5 described above can be opened and closed while the workpiece 1 is running. Also, squeeze roll 5
An auxiliary squeeze roll 9, which can also be opened and closed while the workpiece is traveling, is provided slightly upstream of the workpiece.Also, the peripheral tapered part provided in the conventional device is inserted into the seam closing part of the workpiece 1. Instead of the seam guide roll 8 of the type that maintains the approach angle of the base at the welding start point 2, a sixth seam guide roll 8 is used.
As shown in the figure, a seam roll unit 11 has rolls 10 on both left and right sides that press horizontally the inner surfaces of side plates on both sides perpendicular to the seam surface of the work 1 at a position slightly upstream of the contact point of the squeeze roll. It is provided.

Furthermore, a contact tip receiver 12 having a shape similar to the welding tabs attached to both ends of the welding line in submerged welding is connected to the rear end of the seam forming green of the workpiece 1 to be seam welded by this device. It is installed by

The operation of welding the seam of a square steel pipe using this device will be explained below.

As shown in FIG. 1, the workpiece 1, which is formed into a cross-sectional shape with an open seam, is run while its leading end is sequentially inserted into the forming roll 3.4, the auxiliary squeeze roll 9, and the squeeze roll 5.

Each roll is in an open state when the workpiece tip is inserted;
The tip of the workpiece is inserted smoothly, but once the tip has passed, each roll is tightened one by one to a predetermined position while the workpiece is running. When the roll 3 is tightened, the gap between the seam forming edges of the workpiece 1 becomes tapered, so in some cases it may not be necessary to tighten the roll 4. The squeeze roll 5 has the role of squeezing the upset amount u and narrowing it down to the regular product dimensions, so it is necessary to tighten it to the regular position. In this way, the seam forming edge is brought into contact with the welding point while the workpiece 1 is traveling (), and the welding process can be started while the workpiece 1 is traveling (). By the way, high-frequency welding must be started at a position slightly upstream of the position of the squeeze roll 5, but in a conventional device that does not use the auxiliary squeeze roll 9, the tip of the workpiece 1 is pressed down by the squeeze roll 5. Before the left and right seam forming edges come into contact with each other, no current can be applied, and a welding defect occurs due to insufficient heating in a length that is at least longer than the distance b between the squeeze roll 5 and the contact tip 6.

However, in the device of this embodiment, the squeeze roll 5
Since an auxiliary squeeze roll 9 is provided slightly upstream of the workpiece, when the tip of the workpiece 1 enters, it presses the workpiece 1 into a predetermined position with this roll, so that the left and right seam forming edges at the tip of the workpiece are almost completely removed. Contact occurs at the welding start point 2, and current can be applied from the contact tip 6 at this point. Therefore, the length of the welding failure due to insufficient heating can be reduced to the distance b'1 between the contact tip 6 and the welding start point 2. Although the distance b'' changes depending on the settings of the upset amount u and the approach angle 8, it is fully possible to set it to about 50% of the distance b between the squeeze roll 5 and the contact tip 6. Therefore, the welding defect at the tip of the workpiece 1 is only the length b', which is much shorter than in the past. Furthermore, by providing a welding tab-shaped conductive plate 13 at the tip of the workpiece 1, it becomes possible to shorten the welding defective part from b. Next, when the welding position comes near the rear end of the workpiece 1, in the apparatus of this embodiment, the seam guide roll 10 presses the side plate of the workpiece 1 from the inner surface at a position extremely close to the pressing point of the squeeze roll 5. Therefore, the seam guide roll 10 does not separate from the workpiece 1 until seam welding at the final end of the workpiece 1 is completed, and can maintain a normal approach angle and perform a complete seam welding.

The seam guide roll 10 is provided very close to the pressure contact point of the squeeze roll 5, but its pressing position is not at the seam forming edge like the seam guide roll of the conventional device, but on the inner surface of the workpiece side plate. Therefore, the creepage distance from the contact tip 6 to the pressing point of the seam guide roll 10 becomes considerably long, and a part of the current flows through the seam guide roll 10, so that insufficient heating of the welded part does not occur.

When the welding start point approaches the rear end of the workpiece 1, the contact tip 6 comes to a position protruding from the rear edge of the workpiece 1, but connects to the rear end of the seam forming edge of the workpiece 1 and forms a welding tap-shaped contact tip. Since the contact tip receiver 12 is attached by welding, the contact tip 6 slides on it, and the current flows from the contact tip 6 to the seam weld via the contact tip receiver 12, and the current flows normally to the rear end of the workpiece 1. Complete welding is achieved by heating.

Therefore, there can be almost no welding defects at the rear end of the workpiece. As described above, according to the present invention, it is possible to significantly reduce welding defects at the front and rear ends of the workpiece with a simple configuration compared to the conventional method, and to perform continuous welding by setting the workpiece while it is traveling. As a result, losses in both processing time and materials are reduced, and it becomes possible to economically manufacture single square steel pipes by high-frequency welding, which is notable for reducing capital investment and improving production efficiency. You can get the following effect.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the cross-sectional shape of the workpiece before welding the seam part, Figure 2 is a plan view showing the conventional device with the front end of the workpiece set, and Figure 3 is the seam guy of the conventional device mentioned above. FIG. 4 is a side view of the seam guide roll, FIG. 5 is a plan view showing the embodiment of the present invention with the front end of the work inserted, and FIG. 6 is a plan view showing the workpiece rear end. It is a top view showing the seam guide roll of an apparatus, and the rear end part of a workpiece. 1... Workpiece, 2... Welding start point, 3, 4...
... Forming roll, 5... Forming roll (squeeze roll), 6... Contact tip, 9...
...Auxiliary squeeze roll, 10...Seam guide roll, 12...Contact tip holder, 13...
...Conductive plate. Figure 1 Figure 2 Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] 1. After forming a steel plate into a cross-sectional shape that approximates the required square steel pipe with an open seam, it is formed into the specified shape using forming rolls, and the edges of the base metal on both sides forming the seam are welded. In a square steel pipe manufacturing apparatus that manufactures square steel pipes by welding seams while keeping the angle of approach to a point constant with a seam guide roll, one of the forming rolls is a squeeze roll that squeezes the workpiece to the regular dimensions of the product. An auxiliary squeeze roll is provided upstream, and the seam guide roll is formed as a roll that presses the inner surfaces of both side plates perpendicular to the surface on which the seam is provided, and at least one of the forming rolls including the squeeze roll and the auxiliary squeeze roll is formed. A rectangular steel pipe manufacturing apparatus characterized in that when inserting a workpiece, the workpiece is opened and closed while the workpiece is running and set at a predetermined position, and the seam of the workpiece is welded by high frequency.