JPH06179096A - Method for cutting and removing tab sheet of steel tube - Google Patents

Abstract

PURPOSE:To surely cut off the welded part of a tab sheet by cutting a part of a tube end and removing it together with the tab sheet in a state where a cutting blade is inclined at a specific angle. CONSTITUTION:The tab sheet 1 is cut and removed from the steel tube P by rotating a disk like cutting blade B. Then, the cutting blade B is inclined at an angle theta which is 0 deg. to >=20 deg. against the section orthogonally crossing the longitudinal axis of the steel tube P. In such state, a notch is provided at the point on the circumference of the end face of the tube P, which is outward from the intersection between the long side face of the tab sheet 1 and the end face of the tube P, and the part of the end of the tube P is cut off and removed together with the tab sheet 1. Under the condition where the outside diameter of the cutting blade B is smaller than the inside diameter of the steel tube P, the cutting is performed while the cutting blade B is positioned inwardly of the tube. Consequently, the cutting line is smooth, no slag is generated, no subsequent work is necessitated, and an excellent workability is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cutting and removing a tab plate used when welding a steel pipe.

[0002]

2. Description of the Related Art In the welding process for UO steel pipes, a tab plate is attached to the pipe end in advance prior to welding, and the tab plate is provided with a starting point for welding so that the welding quality of the welding main body portion of the steel pipe is improved. I try to prevent the decline.

This tab plate is cut and removed after welding is completed. When cutting and removing the tab plate, a cutting torch is generally used as shown in Japanese Patent Publication No. 9109/1989. Some Japanese Patent Laid-Open No. 61-203229 use a cutting grindstone.

When a cutting torch is used, as shown in FIGS. 11 and 12, the gas arc cutting torch 50 is not moved, so that a part of the UO steel pipe P having a width wider than that of the tab plate 1 has a shallow trapezoidal shape. It is to cut into. The cutting line is indicated by C'and the welding line is indicated by S (the same applies hereinafter). FIG. 13 shows a case where the tab plate 1 is displaced. In any case, the reason for also cutting off a part of the pipe end is to cut off the tube end weld S ′ of the tab plate 1 as shown in FIG. 2 which will be used later in connection with the method of the present invention.

On the other hand, when a cutting grindstone is used, the tab plate 1 is cut in a direction orthogonal to the outer surface thereof as shown by an imaginary line B'in FIG.

Thus, the UO steel pipe with the tab plate 1 cut off was subjected to an X-ray inspection to confirm that no welding defect remained on the end face portion, and then the end face was chamfered (see FIG. 14). Bevel processing Pa is performed diagonally by (not shown).

[0007]

However, in the conventional method of cutting using the cutting grindstone, the limit is to cut at the base of the tab plate 1 to the maximum, and the heat including the welded portion S'shown in FIG. 2 is limited. The affected area cannot be essentially removed.

The reason for this is that the cutting grindstone is moved to a position where there is no welding heat affected zone closer to the steel pipe side than the tab plate welded portion B ', and the cutting grindstone is perpendicular to the steel pipe major axis from the outer surface of the steel pipe at that position. When trying to cut the welding heat affected zone and the tab plate, the rotation spindle of the grindstone extending in the horizontal direction shown in FIG. 2 becomes an obstacle, and the cutting grindstone cannot be moved further in the central axis direction of the steel pipe. As a result, further cutting of the steel pipe is impossible, and the tab plate cannot be cut off.

On the other hand, with a part of the rotary blade of the cutting grindstone biting into the steel pipe, the steel pipe is gradually rotated, or conversely, the rotary blade of the cutting grindstone is moved along the outer circumference of the steel pipe over the entire circumference. For example, although the end surface of the steel pipe can be cut and separated together with the tab plate, it takes a lot of time for cutting, and thus this method cannot be actually adopted.

Further, as shown in FIG. 13, tab plates 1, 1
If there is a deviation, the cutting is performed at the base of the tab plate 1 on the side protruding outward, and the other tab plate 1 is cut halfway. Therefore, with this cutting method, it is possible to cut the tab plate itself to the maximum extent, and it is not possible to remove even the welding heat-affected zone where there is a risk of inclusion of welding defects.

It is indispensable to cut the pipe end welding heat affected zone together with the cutting torch 50 in order to further ensure quality assurance.

However, when the cutting is performed by the cutting torch 50, there are the following drawbacks. First, the cutting line C ′ shown in FIG. 11 is not microscopically smooth, and in particular, the unevenness is severe at the cutting start portion. If the above-described bevel processing Pa is performed in this state, there is a drawback that the chamfering tool is often chipped.

Secondly, as shown in FIG. 11, when fusing with the cutting torch 50, the slag 51 is scattered and adhered to the lower and upper surfaces of the inner surface of the pipe P, and is bitten by the slide portion in the next pipe expanding step. There is a risk that it will get caught, so that Noro 51 in advance
It is necessary to perform maintenance by using a hand grinder, and there is a problem that this maintenance work requires a lot of labor.

Therefore, the object of the present invention is not only to cut the tab plate, but also to reliably cut the tab plate welding heat-affected zone where there is a risk of welding defects being mixed, and to make the cutting line smooth and smooth. The purpose of this is to prevent the occurrence of such a phenomenon, to completely guarantee the quality of the welded portion of the pipe end tab plate, and to have excellent workability in which the cutting work is completed in a short time.

[0015]

The above object is to provide a method for rotating a disc-shaped cutting blade to cut and remove a tab plate from a steel pipe, wherein the cutting blade is 0 degree with respect to a cross section orthogonal to the long axis of the steel pipe. With the cutting blade inclined at an angle of more than 20 ° and not more than 20 °, the cut end is at a point on the circumference of the pipe end face outside the intersection where the long side face of the tab plate and the pipe end face intersect. The problem can be solved by cutting a part of the tube end and removing it together with the tab plate.

In this case, when the outer diameter of the cutting blade is smaller than the inner diameter of the target steel pipe, cutting is performed while the cutting blade is positioned inside the pipe, and the center of the cutting blade is moved in the inner circumferential direction of the pipe. By cutting while moving, the cutting efficiency is improved.

[0017]

In the present invention, the cutting blade (referred to as a carbide blade cold saw or cutting grindstone) is tilted, and the circle of the pipe end face outside the intersection where the long side face of the tab plate and the pipe end face intersect. By having a cut end at a point on the circumference and cutting a part of the pipe end, the carbon dioxide gas welded portion S ′ of the tab plate 1 (see FIG.
Can also be removed. Further, since the cutting blade is inclined, it is possible to cut only a necessary part without cutting the entire pipe end portion, so that the cutting time is shorter than the entire circumference cutting of the steel pipe, The yield is also high.

Moreover, since the cutting blade is used, the cutting surface is smooth and uniform, and when the beveling Pa is performed, the chamfering bite is not damaged, and no slag is generated or adhered to the inner surface. Therefore, essentially no subsequent care is required.

[0019]

The present invention will be described in more detail by way of examples with reference to the drawings. In the present invention, in the method of cutting and removing the tab plate 1 from the UO steel pipe P by rotating the disc-shaped cutting blade B, as shown in FIGS.
As shown in FIGS. 4 and 5, when the cutting blade B is inclined at an angle θ of more than 0 ° and 20 ° or less, more preferably 15 ° or less, with the O steel pipe P end plate, as shown in FIGS. 1 has the cut ends Cs, Ce outside the respective lines L, L at which the respective side faces 1a, 1a and the pipe end face intersect, and a part of the steel pipe is cut and removed together with the tab plate 1. Note that the angle θ
If is too large, the cutting blade easily escapes, and eventually it becomes impossible to cut.

As an automatic cutting means, the device shown in FIG. 1 can be used. That is, a rail 10 is laid in the direction of the steel pipe P at a position facing the end surface of the steel pipe P, and a carriage 11 is mounted on the rail 10 so as to be able to move back and forth. Further, a transverse carriage 12 is installed in the carriage 11 so as to be traversable through a groove in a direction penetrating the plane of the drawing. A tilting arm 13 is attached to the traverse carriage 12 at its fulcrum 1
It is provided so that the inclination angle can be adjusted around 4 by the expansion / contraction means 15. Further, a cutting blade feed drive motor 16 is fixed to the tilt arm 13, so that the sliding portion 17 engaged with the tilt arm 13 can slide along the tilt arm 13. Further, a rotary drive motor 18 is mounted on the sliding portion 17, whereby the cutting blade B is
Is designed to rotate. Note that FIG. 2 is an enlarged view of the X portion of FIG.

When cutting with the cutting blade B, for example, when the diameter of the cutting blade B is larger than the width of the tab plate 1 or the required cutting width W as shown in FIG.
Are arranged along a line passing through the center of the steel pipe P, and once the cutting blade B
The cutting can be performed by slightly lowering it to prevent it from escaping and making a flaw, inclining the cutting blade B at a predetermined angle, and then simply lowering it. Note that FIG.
In the figure, a cutting line C'by a conventional cutting torch is comparatively shown in comparison with the cutting line C according to the present invention. Here, the separation distance between the cutting line C and the pipe end face can be appropriately selected within a range of 10 mm or less where the welding heat affected zone can be removed because the welding heat affected zone is about 10 mm at maximum.

However, as shown in FIG. 8 and FIG. 9, when the diameter of the cutting blade B is smaller than the required cutting width W, uncut residue occurs, so that the center of the cutting blade B is on the center line of the steel pipe P. After positioning at a position and a position where the end surface of the cutting blade B abuts the inner surface of the steel pipe P, the cutting blade B is tilted at a predetermined angle, then moved to the right side (or left side), and then sequentially cut downward. The cutting can be performed by moving the steel pipe P in the circumferential direction in the clockwise direction (or counterclockwise direction).
Thus, the cutting efficiency is increased by adopting the circumferential movement method. The same method can be adopted even when the diameter of the cutting blade B is larger than the required cutting width W.

An outline of the simple cutting-down cutting method and the cutting method by moving the cutting blade B in the circumferential direction is shown in FIGS. 5 and 6. FIG. 6 and FIG. 7 show a cutting mode when the tab plates 1 and 1 are deviated, and also show that the tab plate 1 on the retracted side is used as a reference at the time of cutting. Is. In any case, the aspect of the cut end face finally obtained is as shown in FIG.

Here, as compared with the simple undercutting method of the cutting blade B, the present inventor cuts the cutting method by moving in the circumferential direction as shown in FIGS. 6, 8 and 9. We know that time will be shortened. By the way, as shown in FIG. 15 and FIG. 16, the tab plate 1 having various sizes is simulated in the same manner as the horizontal cutting corresponding to the above-mentioned simple lowering method and the above-mentioned circumferential movement. Regarding the case of performing vertical cutting corresponding to the cutting method by
When the time required for cutting was examined, the results shown in Table 1 were obtained.

[0025]

[Table 1]

According to this result, it can be seen that the vertical cutting as shown in FIG. 16 shortens the cutting time and enables the cutting even if the thickness a is large.

As another aspect of the present invention, as shown in FIG. 10, an example of cutting from the outer surface of the steel pipe P is also included.
In this case, there is an advantage that the cutting resistance becomes small.

[0028]

As described above, according to the present invention, the welded portion of the tab plate can be reliably cut off, the cutting line is smooth, no slag is generated, and no subsequent maintenance is required, resulting in excellent workability. It becomes a thing.

[Brief description of drawings]

FIG. 1 is a schematic front view showing an example of a cutting method of the present invention and a cutting device used for the same.

FIG. 2 is an enlarged view of the X-ray portion.

FIG. 3 is a perspective view showing a cut end face after cutting.

FIG. 4 is an explanatory view showing a relationship between a steel pipe and a cutting blade and a cutting line.

FIG. 5 is a schematic perspective view of a cutting situation.

FIG. 6 is a schematic perspective view of another cutting situation.

FIG. 7 is a schematic perspective view of another cutting situation.

FIG. 8 is a movement trajectory diagram of a cutting blade.

FIG. 9 is another movement trajectory diagram of the cutting blade.

FIG. 10 is a schematic front view showing another embodiment of the present invention.

FIG. 11 is a schematic perspective view of a conventional example.

FIG. 12 is a plan view showing a cutting line of a conventional example.

FIG. 13 is a plan view showing a cutting line of a conventional example of an example in which the tab plates are not aligned.

FIG. 14 is a front view of the steel pipe after beveling.

FIG. 15 is an explanatory diagram of a horizontal cutting mode for the tab plate.

FIG. 16 is an explanatory diagram of a vertical cutting mode for the tab plate.

[Explanation of symbols]

P ... UO steel pipe, B ... Cutting blade, S ... Weld seam line, 1 ... Tab plate, Cs, Ce ... Cut end.

Claims (2)

[Claims] 1. A method for cutting and removing a tab plate from a steel pipe by rotating a disc-shaped cutting blade, wherein the cutting blade has an angle of more than 0 ° and 20 ° or less with respect to a cross section orthogonal to the long axis of the steel pipe. However, in a state in which the cutting blade is inclined, having a cutting end at a point on the circumference of the pipe end face outside the intersection where the long side surface of the tab plate and the pipe end face intersect,
A method for cutting and removing a tab plate of a steel pipe, characterized in that a part of the pipe end is cut and removed together with the tab plate. 2. When the outer diameter of the cutting blade is smaller than the inner diameter of the target steel pipe, cutting is performed while the cutting blade is positioned inside the pipe, and the center of the cutting blade is moved in the inner circumferential direction of the pipe. The method for cutting and removing a tab plate of a steel pipe according to claim 1, wherein the cutting is performed while performing the cutting.