JP2013248625A - Method of manufacturing steel pipe with projection - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a steel pipe with a projection, which has low possibility of burn-through and thermal deformation of the steel pipe and can secure a sufficient penetration amount to the steel pipe.SOLUTION: A pair of patches 2, 2 are arranged on an inner surface of a steel pipe 1 at intervals. In carrying out build-up welding between the patches while relatively moving the patches 2, 2 and a welding torch 5 to the inner surface of the steel pipe 1, an axial direction of the welding torch 5 is inclined with respect to a vertical direction so that an upper side of the welding torch 5 inclines to an opposite side to a moving direction of the steel pipe 1. Thus, in carrying out the build-up welding on the inner surface of the steel pipe, it is less likely that burn-through and thermal deformation of the steel pipe occur, and a sufficient penetration amount to the steel pipe can be secured.

Description

  The present invention relates to a method of manufacturing a steel pipe with projections using overlay welding.

  In the civil engineering or construction field, a composite structure in which a steel pipe is filled with concrete or a steel pipe is embedded in the concrete is used for a building column or a foundation pile. In the composite structure of these steel pipes and concrete, protrusions are provided on the inner surface of the steel pipe in order to increase the adhesion between the steel pipe and the concrete.

As one method for providing protrusions on the inner surface of a steel pipe, a method for manufacturing a steel pipe with protrusions described in Patent Document 1 is known.
In this manufacturing method, a pair of contact plates are arranged at an interval on the inner surface of a steel pipe, and overlay welding is performed between these contact plates while moving the contact plate and the welding torch relative to the inner surface of the steel pipe. It is characterized by.
According to such a method for manufacturing a steel pipe with a projection, a projection having a high height can be easily formed.

Japanese Patent No. 3926326

By the way, in order to raise the protrusion which can be manufactured per pass of overlay welding, it is necessary to melt a lot of welding wires. For this purpose, there are methods such as increasing the heat input (increasing the current / voltage or / and decreasing the welding speed), increasing the length of the welding wire, or decreasing the diameter of the welding wire.
However, if the amount of heat input is increased too much, there is a high possibility that the steel pipe will be melted or thermally deformed, and this becomes a problem particularly when the plate thickness is thin.
Further, if the length of the welding wire is increased or the diameter of the welding wire is reduced, the number of melting welding wires increases, but the penetration into the base material (steel pipe) is reduced and the steel pipe and the projection are not integrated, which is a problem.

  The present invention has been made in view of such circumstances, and a method of manufacturing a steel pipe with protrusions that is unlikely to cause melting or thermal deformation of the steel pipe and that can secure a sufficient amount of penetration into the steel pipe. The purpose is to provide.

In order to achieve the above object, the method for producing a steel pipe with projections according to the present invention is a method for producing a steel pipe with projections by forming projections on the inner surface of the steel pipe by overlay welding,
When placing a pair of contact plates on the inner surface of the steel pipe at an interval and moving these contact plates and the welding torch relative to the inner surface of the steel pipe while performing overlay welding between these contact plates,
The axial direction of the welding torch is inclined so that the upper side of the welding torch is inclined to the opposite side to the moving direction of the steel pipe with respect to the vertical direction.

In the present invention, the axial direction of the welding torch is inclined so that the upper side of the welding torch is inclined to the opposite side to the moving direction of the steel pipe, that is, a receding angle is provided in the welding torch. Therefore, since welding can be performed while pushing away the melted wire due to the arc pressure, a sufficient amount of penetration can be ensured.
Further, since it is not necessary to increase the amount of heat input too much, the possibility that the steel pipe will be melted or thermally deformed is reduced.

In the above-described configuration of the present invention, it is preferable that an inclination angle (retraction angle) in the axial direction of the torch is set to 8 to 15 °.
This is because if the receding angle θ is too small, that is, less than 8 °, the force to push back the molten wire is not sufficiently exerted, and if the receding angle θ is too large, that is, exceeds 15 °, the projection shape is not stable.

In the above structure of the present invention, it is preferable to weld the tip of the welding wire of the welding torch toward the lowermost part of the inner surface of the steel pipe.
Because, when welding is performed at a position shifted from the lowermost part of the inner surface of the steel pipe in the moving (rotating) direction of the steel pipe, the molten welding wire quickly flows from a high position to the lower position of the steel pipe, and covers the welding portion. This is because the amount of welding material (welding wire solidified after melting) into the base material (steel pipe) is reduced.
Also, if welding is performed at a position deviated from the lowermost part of the inner surface of the steel pipe in the direction opposite to the rotation direction of the steel pipe, the molten welding wire also flows quickly from a high position to the lower position of the steel pipe in this case. This is because the amount of the weld wire melted becomes extremely small, so that the steel pipe is easily melted and undercut.

  Furthermore, in the above structure of the present invention, the height is 6 mm or more, the width is 5 mm or more, the angle formed between the side part and the inner surface of the steel pipe is 60 to 90 °, the side part has a straight part, and the upper part is a curve. It is preferable to form a projection having a cross-sectional shape on the inner surface of the steel pipe.

Thereby, it is possible to easily form a projection having a straight section on the side portion and a high cross-sectional shape with a curved upper portion easily and economically with a minimum amount of weld metal by one welding. it can.
Further, for example, when concrete is filled in a steel pipe with an inner surface protrusion to obtain a concrete-filled steel pipe, the height of the protrusion is high, so that sufficient adhesion between the steel pipe and the concrete can be obtained even if the interval between the protrusions is reduced. Since the protrusion height can be increased by setting the protrusion height to 6 mm or more as in the present invention, the number of protrusions (the number of windings when the protrusion is spiral) can be reduced, and the protrusion can be formed. The man-hours and costs required can be greatly reduced. Further, in the case of a cast-in-place steel pipe concrete pile for a foundation, since the protrusion height is high, it is possible to reduce the influence on the adhesion force of the hole wall stabilizing liquid such as bentonite when placing concrete. The same effect can be obtained for the steel pipe with an outer protrusion.

In addition, if the angle formed between the inner surface of the steel pipe and the side of the projection is too small, the concrete slips, and if it is 90 ° or more, it becomes difficult to remove the contact plate after the welding is finished. When the angle is 60 to 90 °, these problems do not occur.
In addition, if the cross-sectional shape of the protrusion is an arc, the concrete may slide, and if the upper part is straight like the cross-sectional shape of the protrusion is trapezoidal, stress is applied to the intersection of the side surface and the upper surface. Concentration is likely to occur and the adhesive force may be reduced, but these problems can be avoided if the protrusion has a cross-sectional shape with a straight portion on the side and a curved upper portion as in the present invention.

  According to the present invention, when overlay welding is performed on the inner surface of a steel pipe, it is unlikely that the steel pipe will melt or undergo thermal deformation, and a sufficient amount of penetration into the steel pipe can be ensured.

It is a sectional side view which shows the manufacturing method of the steel pipe with a protrusion which concerns on embodiment of this invention. It is an expansion perspective view of the principal part of FIG. It is for demonstrating the manufacturing method of the steel pipe with a projection concerning embodiment of this invention, (a) Sectional drawing which shows the principal part of the conventional manufacturing method, (b) The principal part of the manufacturing method which concerns on this invention It is sectional drawing shown. It is sectional drawing of the processus | protrusion which concerns on embodiment of this invention. It is for demonstrating the manufacturing method which concerns on this invention, and is sectional drawing of the principal part which shows the state in which overlay welding is carried out.

Embodiments of the present invention will be described below with reference to the drawings.
1 and 2 are views showing a method of manufacturing a steel pipe with projections according to an embodiment of the present invention. FIG. 1 is a side sectional view, and FIG. 2 is an enlarged perspective view of a main part.
As shown in these drawings, in order to form protrusions on the inner surface of the steel pipe in the circumferential direction, first, the steel pipe 1 is placed sideways, and a pair of contact plates 2 are placed on the lower side of the inner surface of the steel pipe 1. 2 are arranged. As the backing plate 2, a water-cooled copper plate (water-cooled copper plate) is usually used, but a ceramic plate or the like can also be used. The bottom surface of the backing plate 2 is formed in an arc shape along the inner surface of the steel pipe 1. The pair of contact plates 2 and 2 are arranged in parallel to the inner surface of the steel pipe 1 with a space therebetween.

  Next, the boom 4 of the welding device 3 located outside the steel pipe 1 is inserted into the steel pipe 1, and the welding wire 6 of the welding torch 5 provided at the tip end of the boom 4 is connected to the pair of contact plates 2, Insert between 2. Then, while rotating the steel pipe 1 in the circumferential direction, an arc is generated in the space formed by the inner surface of the steel pipe 1 and the contact plates 2 and 2 to perform overlay welding. The contact plates 2 and 2 are supported by the boom 4 and the like. For welding, gas metal arc welding such as carbon dioxide arc welding, MAG welding or MIG welding can be used as appropriate.

It is necessary to finish the side surface of the contact plate 2 that forms the space for overlay welding in order to form a protrusion having a straight line portion on the side portion of the cross-sectional shape. In order that the angle (rise angle) formed between the side surface of the protrusion formed on the inner surface of the steel pipe 1 and the inner surface of the steel pipe 1 forms a predetermined acute angle, a predetermined angle can be given to the side surface of the backing plate 2. . If the angle of the side surface of the backing plate 2 exceeds 90 °, it will be difficult to remove the backing plate 2 after the end of welding, so it is set to about 60 to 90 °, for example.
The height of the backing plate 2 needs to be higher than the height of the projections to be formed. However, if it is too high, the cost of the backing plate will be excessive, and the welding arc will be difficult to see and workability will deteriorate. It is preferable to set the height appropriately.
If the distance between the contact plates 2 and 2 is too narrow, damage due to the welding arc will occur, so it is necessary to make it about 5 mm or more. However, if it is too wide, extra welding material will be required and the economy will be low. Too much is not preferable. The width of the protrusion formed on the inner surface of the steel pipe 1 is substantially equal to the distance between the contact plates 2 and 2.

  In order to obtain a continuous projection on the inner surface of the steel pipe 1, it is necessary to rotate the steel pipe 1 and move the inner surface of the steel pipe 1, the welding torch 5 and the pair of contact plates 2, 2 relatively. When the length of the backing plates 2 and 2 is short, the molten metal flows out from the lateral (longitudinal direction of the backing plate 2) opening. On the other hand, if the contact plates 2 and 2 are too long, the frictional force between the side surfaces of the protrusions formed by solidification of the molten metal and the contact plate 2 becomes large, and it becomes difficult to move stably and the contact with the inner surface of the steel pipe 1. Since it becomes difficult to maintain the adhesiveness with the plate 2, it is necessary to set the length appropriately. The length of the backing plate 2 usually needs to be about 25 mm or more and about 120 mm or less, and is preferably about 100 mm or less, more preferably about 80 mm or less in consideration of workability.

  In order to increase the height of the protrusions, there is a method of forming protrusions by means of a multi-layer, but it takes time for welding work, and extra time is required for accurately aligning the positions of the contact plates 2 and 2 with the positions of the existing protrusions. In addition, since the frictional force between the side surfaces of the contact plates 2 and 2 and the side surfaces of the existing protrusions is large and the workability is deteriorated, it is preferable to obtain the required protrusion height by one welding. For this purpose, it is preferable to perform welding with a welding current of 250 to 450 A, a welding voltage of 25 to 45 V, and a welding speed of 30 to 80 cm / min.

When forming projections on the thin-walled steel pipe 1, the welding torch 5 of the welding torch 5 is used to prevent melting, reduce thermal deformation, and ensure a sufficient amount of penetration into the base material (steel pipe 1). The axial direction is inclined with respect to the vertical direction so that the upper side of the welding torch 5 is inclined opposite to the moving direction of the steel pipe 1 (clockwise in FIG. 3).
That is, conventionally, as shown in FIG. 3A, the axial direction of the welding torch 5 is set to the vertical direction, but in this embodiment, as shown in FIG. The direction inclination angle (retraction angle θ) is set to 8 to 15 °, more preferably 8 to 12 °.
This is because if the receding angle θ is too small, the force to push back the molten wire is not sufficiently exerted, and if the receding angle θ is too large, the projection shape is not stable.

Furthermore, in the present embodiment, the tip of the welding wire 6 of the welding torch 5 is welded toward the lowermost part of the inner surface of the steel pipe 1.
If welding is performed at a position shifted in the rotational direction of the steel pipe 1 from the lowermost part of the inner surface of the steel pipe 1, the molten welding wire 6 flows quickly from a high position to the lower position of the steel pipe, and covers the welding location. This is because the amount of the welding material (welding wire solidified after being melted) into the base material (steel pipe 1) is reduced.
Further, when welding is performed at a position shifted from the lowermost part of the inner surface of the steel pipe 1 in the direction opposite to the rotation direction of the steel pipe 1, the molten welding wire also flows quickly from a high position to the lower position of the steel pipe in this case. This is because the amount of the molten welding wire at the location is extremely reduced, so that the steel pipe 1 is likely to be melted or undercut.

  According to the method of manufacturing a steel pipe with a protrusion as described above, a high protrusion T as shown in FIG. 4 on the inner surface of the steel pipe 1, that is, a width B of 5 mm or more, a height H of 6 mm or more, The angle formed by the side surface of the protrusion T (rise angle) α is 60 to 90 °, the straight part is formed on both sides, and the upper surface is curved. Can be formed.

In order to form the protrusion T on the inner surface of the steel pipe 1, first, the height is slightly higher than the height of the protrusion T to be formed, the length is 25 to 120 mm, and the angle between the side surface and the inner surface of the steel pipe 1 is 60 to 90. A pair of contact plates 2, 2 made of a water-cooled copper plate that is set to be ° and whose side surface is flat or substantially flat and whose bottom surface is formed in an arc shape along the inner surface of the steel pipe 1 Place in parallel at intervals on the lower side of the inner surface. The distance between the contact plates 2 and 2 may be determined according to the width of the protrusion T, but may be slightly widened in consideration of the heat shrinkage allowance as necessary.
Next, while rotating the steel pipe 1 in the circumferential direction, the welding current is 250 to 450 A, the welding voltage is 25 to 45 V, and the welding speed is 30 in the space formed by the inner surface of the steel pipe 1 and the contact plates 2 and 2. Overlay welding is performed by downward carbon dioxide arc welding or MAG welding using a mixed gas of carbon dioxide and argon gas at -80 cm / min.

As shown in FIG. 5, in the present embodiment, the steel pipe 1 is rotated at the lowermost part of the inner surface of the steel pipe 1 (the portion where the line segment perpendicular to the center of the steel pipe 1 intersects the inner surface of the steel pipe 1). However, since the welded wire 6 flows to the lower position of the steel pipe due to the curvature of the steel pipe 1 because overlay welding is performed, an arc is generated on the upper surface of the melted wire, so that it melts into the base material (steel pipe). Becomes smaller.
However, by providing the welding torch 5 with the receding angle θ as described above, welding can be performed while pushing away the welding wire 6 melted by the arc pressure, so that a sufficient amount of penetration can be ensured.
Moreover, since it is not necessary to raise the amount of heat input too much, the possibility that the steel pipe 1 is melted down or thermally deformed is reduced.

  Thus, when concrete is filled into the steel pipe with projections with the projections T formed on the inner surface to form a concrete-filled steel pipe pile, the height of the projections is high, so even if the interval between the projections is reduced, the steel pipe and the concrete are sufficient. Adhesive force can be obtained. The protrusion interval of the steel pipe with protrusions currently used is about 40 mm, but the protrusion interval can be increased by setting the protrusion height to 6 mm or more as in the present invention, and the protrusion in a good stress transmission region. It is also possible to set the distance between the protrusions to 90 mm or more by setting the distance to height ratio of 10 to 20. Since the distance between the protrusions can be increased, the number of protrusions (the number of windings when the protrusion is spiral) can be reduced, and the man-hour and cost required for forming the protrusion can be greatly reduced. Further, since the height of the protrusion is high, the influence on the adhesion force of the hole wall stabilizing liquid such as bentonite at the time of placing concrete can be reduced.

Further, if the angle α formed between the inner surface of the steel pipe 1 and the side surface of the projection T is too small, the concrete slips, and if it is 90 ° or more, it becomes difficult to remove the contact plates 2 and 2 after the welding is finished. When the angle is set to 60 to 90 °, these problems can be avoided.
Moreover, when the cross-sectional shape of the protrusion is an arc shape as a whole, the concrete may slide. In addition, when the upper part is a straight line such that the cross-sectional shape of the protrusion is trapezoidal, stress concentration is likely to occur at the intersection between the side surface and the upper surface, and the adhesive force may be reduced. Since the protrusion T has a shape having a straight portion on the side of the cross section and a curved upper portion, these problems do not occur.

When it is desired to form a spiral projection on the inner surface of the steel pipe 1, the steel pipe 1 may be moved in the axial direction of the steel pipe 1 while rotating the steel pipe 1, or the steel pipe 1 may be rotated while rotating. The plates 2 and 2 and the welding torch 5 may be moved in the axial direction of the steel pipe 1.
Moreover, when it is desired to form a plurality of projections at a time, the plurality of welding torches 5 and the contact plates 2 and 2 disposed on both sides of each welding torch 5 may be used.
Further, the protrusion can be formed continuously or intermittently.

Hereinafter, the present invention will be specifically described by way of examples.
First, the contact plates 2 and 2 made of a water-cooled copper plate having a length of 100 mm, a height of 20 mm, and a width of 40 mm are parallel to the lower position of the inner surface of the steel pipe 1 having an inner diameter of 1376 mm with an interval of 6 mm. Put it on.
Next, while rotating the steel pipe 1 in the circumferential direction, a welding current is 340 A, a welding voltage is 35 V, a welding speed is 41 cm / min, and welding is performed in a space formed by the inner surface of the steel pipe 1 and the contact plates 2 and 2. Overlay welding is performed by MAG welding using a mixed gas of carbon dioxide gas and argon gas downward with a wire diameter of 1.4 mm, the projection height H is about 7.5 mm, the width B is about 6 mm, and the rising angle α is about The protrusion T having a flat 90 ° side surface and a curved upper surface could be easily formed in the circumferential direction by one welding.

In addition, as a condition, steel pipe diameter: 1200 mm, plate thickness: 10 mm, current: 340 A, voltage: 35 V, welding welding at 41 cm / min as described above, and build-up T is formed on the inner surface of the steel pipe 1. The results of the evaluation are shown in Table 1.
As shown in Table 1, it was confirmed that the inclination angle in the axial direction of the torch is preferably set to 8 to 15 °.

DESCRIPTION OF SYMBOLS 1 Steel pipe 2 Contact plate 3 Welding device 4 Boom 5 Welding torch 6 Welding wire T Protrusion B Protrusion width H Protrusion height α Angle formed between the side surface of the protrusion and the inner surface of the steel pipe (rise angle)
θ Axis tilt angle (backward angle) of torch

Claims (4)

A method of manufacturing a steel pipe with a protrusion by forming protrusions on the inner surface of the steel pipe by overlay welding,
When placing a pair of contact plates on the inner surface of the steel pipe at an interval and moving these contact plates and the welding torch relative to the inner surface of the steel pipe while performing overlay welding between these contact plates,
A method of manufacturing a steel pipe with projections, characterized in that the axial direction of the welding torch is inclined with respect to the vertical direction so that the upper side of the welding torch is inclined opposite to the moving direction of the steel pipe.   The method of manufacturing a steel pipe with projections according to claim 1, wherein an inclination angle in an axial direction of the torch is set to 8 to 15 °.   The method for manufacturing a steel pipe with projections according to claim 1 or 2, wherein a tip of a welding wire of the welding torch is welded toward a lowermost part of an inner surface of the steel pipe.   A protrusion having a cross-sectional shape having a height of 6 mm or more, a width of 5 mm or more, an angle between the side portion and the inner or outer surface of the steel pipe of 60 to 90 °, a straight portion on the side portion, and a curved portion on the upper side. It forms in the inner surface of a steel pipe, The manufacturing method of the steel pipe with a protrusion of any one of Claims 1-3 characterized by the above-mentioned.

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