JP2007210012A - Method and device for overlaying steel tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for overlaying a steel tube capable of unifying the overlaying thickness, suppressing the cost of a material necessary for the overlaying, and reducing the labor during the overlaying. <P>SOLUTION: A steel tube 11 of a furnace wall 10 is overlaid in the circumferential direction by a welding equipment in which a welding torch 40 is moved along a substantially circular shaped rail 30. The welding torch 40 is moved along an outer circumferential surface of the steel tube 11 while the arc length from the welding torch 40, in other words, the space between the welding torch 40 and the steel tube 11 is kept constant. The overlaying thickness is unified in the circumferential direction of the steel tube 11 thereby, the overlaying thickness is reduced on the whole, and the use of an overlaying material is suppressed to reduce cost. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a build-up welding method for a steel pipe constituting a furnace wall of a boiler and a build-up welding apparatus used therefor.

In an industrial boiler such as a coal-fired boiler and a garbage incinerator, the furnace wall of the boiler is composed of a panel composed of a plurality of steel pipes and fins. Carbon steel and low alloy steel are used for these steel pipes. And the surface inside the boiler wall of such a furnace wall is welded by welding in order to resist corrosion caused by sulfur content, high temperature oxidation or the like generated during combustion in the boiler.
Conventionally, as shown in FIG. 7, the welding torch 2 is advanced along the axial direction of the steel pipe 1, and overlay welding is performed, and the adjacent weld beads 3 are overlapped with each other, thereby 1 is increased in thickness (see, for example, Patent Documents 1 and 2).

Japanese Patent Publication No. 60-32544 JP 2000-84665 A

For the build-up of the steel pipe 1 made of carbon steel or low alloy steel, stainless steel or Inconel welding material having excellent corrosion resistance is used, but in particular, in the case of Inconel welding material, it is very expensive. There is a demand to reduce the material cost as much as possible while securing the minimum thickness that can provide durability.
In place of overlay welding, if overlaying is performed using thermal spraying, the thickness of the overlay can be reduced. In that case, in order to adhere the molten alloy particles to the surface of the steel pipe 1, the overlayed portion Becomes porous (a large number of voids exist), and therefore, there is a problem that peeling of the built-up portion is likely to occur.

Further, in the case of an Inconel-based welding material, since a large amount of Ni is contained, the end portion 3a of the weld bead 3 tends to be convex as shown in FIG. 8 as compared with a welding material of carbon steel or low alloy steel. There is. For this reason, when the weld beads 3 adjacent to each other are overlapped by about 1/3 to 1/2 of the bead width, the thickness of the overlaid portion is significantly increased in the convex portion.
If the build-up is uneven, local corrosion tends to occur in the recess 3b. Therefore, the minimum build-up thickness is defined by the thickness of the recess 3b, and management during build-up welding is performed. It takes time to measure the thickness of the recess 3b. Moreover, if the minimum build-up thickness is ensured by the recess 3b, the other portions will have an extra build-up thickness, and an extra welding material is required particularly at the convex portion of the end portion 3a. This leads to an increase in material costs.
The present invention has been made on the basis of such a technical problem, and it is possible to make the build-up thickness uniform, reduce the material cost necessary for build-up, and reduce the labor during build-up welding. An object of the present invention is to provide a build-up welding method and build-up welding apparatus for a steel pipe.

The present invention made for this purpose is a method of overlay welding the surface of a steel pipe, the step of overlay welding the surface of the steel pipe in the circumferential direction by moving the welding torch in the circumferential direction of the steel pipe, Repeating the step of moving the welding torch in the axial direction of the steel pipe. Here, when the welding torch is moved in the axial direction of the steel pipe, the welding torch is moved in the axial direction by a dimension smaller than the width dimension of the weld bead formed on the surface of the steel pipe by the welding arc generated between the welding torch and the steel pipe. Move the weld beads to overlap.
In order to build-up weld the steel pipe in the circumferential direction, it is preferable to move the torch holding part holding the welding torch along an arc-shaped rail arranged substantially concentrically with respect to the axis of the steel pipe.
Such a steel pipe build-up welding method can be used for any purpose, but a steel pipe to be build-up welded forms a furnace wall of a boiler by installing a plurality of steel pipes side by side. It is particularly effective in some cases. Moreover, when the furnace wall of a boiler is an existing thing, the furnace wall is the state located in the substantially vertical plane. Thus, when the overlay welding method for steel pipes of the present invention is applied to a steel pipe forming an existing furnace wall, the welding torch is directed downward in the step of moving the welding torch in the axial direction of the steel pipe. It is preferable to move them. Thereby, the whole steel pipe can be build-up-welded by progressing downward sequentially while carrying out the build-up welding of the steel pipe in the circumferential direction.
As a welding material used for such overlay welding, a base metal and a co-metal material, a stainless steel material, or an inconel material can be used. Particularly in the case of Inconel-based materials, the weld bead for overlay welding can be made smooth. Further, when the corrosion thinning is not so severe, it is preferable to weld the corrosion-thinned steel pipe using a material equivalent to the base material.
Further, when overlay welding the surface of the steel pipe in the circumferential direction, the welding torch may be reciprocated with a constant width in the axial direction of the steel pipe while moving in the circumferential direction. This is a technique called weaving or oscillation, whereby the width of the weld bead can be widened and efficient overlay welding can be performed.

  If the entire surface of the steel pipe cannot be welded on one side of the furnace wall due to interference with other adjacent steel pipes, the welding torch is moved in the axial direction of the steel pipe at both circumferential ends of the steel pipe. It is also possible to perform overlay welding and perform circumferential build-up welding in the region between the portions where the overlay welding is performed in the axial direction.

The present invention includes a frame that is set along the inner peripheral surface of a furnace wall of a boiler, and a steel pipe that is supported so as to be movable along the inner peripheral surface of the furnace wall with respect to the frame and builds up a steel pipe that constitutes the furnace wall A torch holding part for holding a welding torch for carrying out, and the torch holding part can be welded to the steel pipe along the circumferential direction of the steel pipe with the welding torch by moving along the arc-shaped rail It can also be set as the overlay welding apparatus characterized by being comprised.
In this case, the frame preferably supports the torch holding part so as to be movable at least in the axial direction of the steel pipe in a plane substantially parallel to the furnace wall.
The torch holding part preferably keeps the angle of the welding torch with respect to the surface of the steel pipe constant when moving along the rail.

  According to the present invention, the build-up thickness can be made uniform in the circumferential direction by welding the steel pipe in the circumferential direction. If the build-up thickness can be made uniform in this way, the build-up material in the thick part of the build-up will not be wasted, as in the case where the build-up is made in accordance with the thinnest part. The build-up thickness can be reduced, and the amount of build-up material used can be suppressed to reduce the cost. Moreover, compared to thermal spraying, in the case of overlay welding, peeling of the overlay portion is less likely to occur, and the durability is excellent.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a diagram for explaining a method for overlaying a furnace wall in the present embodiment.
As shown in FIG. 1, a furnace wall 10 such as an industrial boiler or a coal-fired boiler is arranged in a panel shape by arranging a plurality of steel pipes 11 and joining between adjacent steel pipes 11 and 11 by a plate 12. Is formed.

In order to build up such a furnace wall 10, a welding apparatus 20 as shown in FIG. 2 is used.
The welding apparatus 20 includes a pair of upper and lower base frames (frames) 21 that are adsorbed and supported by a magnetic force on the steel pipe 11 of the furnace wall 10 or screwed to a plate temporarily attached to the furnace wall 10, and the base frame 21. A horizontal movement carriage 22 provided so as to be movable along the horizontal direction, a vertical rail (frame) 23 attached to the upper and lower horizontal movement carriages 22, and a movement along the vertical rail 23. A vertical movement carriage 24 and a torch holding part 25 attached to the vertical movement carriage 24 are provided.
The torch holding part 25 is movable in the vertical and horizontal directions by the movement of the laterally movable carriage 22 and the longitudinally movable carriage 24. Further, the laterally movable carriage 22 and the longitudinally movable carriage 24 can perform a predetermined operation based on a remote control or a program inputted in advance.
As such a welding apparatus 20, for example, the one disclosed in Japanese Patent Publication No. 60-32544 can be used.

As shown in FIG. 1A, the torch holding part 25 is provided with a torch holder 31 movably provided along a substantially arc-shaped rail 30 so that the welding torch 40 is held by the torch holder 31. It has become.
A rack gear 32 is formed on the peripheral surface of the rail 30. On the other hand, the torch holder 31 incorporates a pinion gear (not shown) that meshes with the rack gear 32, and the torch holder 31 is configured to be movable along the rail 30 by rotating the pinion gear with a motor (not shown). Yes.

In order to build up the furnace wall 10 using such a welding apparatus 20, build-up welding is performed while moving the welding torch 40 along the circumferential direction of the steel pipe 11 of the furnace wall 10. For this purpose, the torch holding part 25 is positioned so that the arc center of the substantially arc-shaped rail 30 is aligned with the axis of one steel pipe 11 or shifted in the depth direction. The arc is generated from the welding torch 40 while moving the torch holder 31 along the rail 30 at a predetermined speed. As a result, the arc length from the welding torch 40, that is, the distance between the welding torch 40 and the steel pipe 11 is kept constant, and the welding torch 40 moves along the outer peripheral surface of the steel pipe 11. Is welded in the circumferential direction, and the thickness of the steel pipe 11 can be kept constant in the circumferential direction.
Then, when overlay welding is performed from one end 11 a to the other end 11 b on the surface of the steel pipe 11 exposed on the inner surface side of the furnace wall 10 by the welding torch 40, the welding torch 40 is attached to the rail 30. Move in the opposite direction along. Further, by sequentially lowering the torch holding part 25 along the axial direction of the steel pipe 11, the welding torch 40 can be moved in a zigzag shape as indicated by the arrow in FIG. .
Thereby, the full length of the steel pipe 11 can be build-up welded in the circumferential direction.

  When build-up welding of one steel pipe 11 is completed, the torch holding part 25 is moved to a position corresponding to another adjacent steel pipe 11 and build-up welding is performed in the same manner as described above. By repeating this, the steel pipe 11 constituting the furnace wall 10 can be welded on the inner peripheral surface side of the furnace wall 10.

As described above, the welding thickness of the steel pipe 11 is increased by welding the steel pipe 11 of the furnace wall 10 in the circumferential direction by the welding device 20 in which the welding torch 40 moves along the substantially arc-shaped rail 30. Uniform in the circumferential direction. If the build-up thickness can be made uniform in this way, the build-up material in the thick part of the build-up will not be wasted, as in the case where the build-up is made in accordance with the thinnest part. The build-up thickness can be reduced, and the amount of build-up material used can be suppressed to reduce the cost. Moreover, compared to thermal spraying, in the case of overlay welding, peeling of the overlay portion is less likely to occur, and the durability is excellent.
Further, as described above, in the case of the Inconel-based welding material, since a large amount of Ni is contained, as shown in FIG. 8, the end portion 3a of the weld bead 3 is compared with the welding wire of carbon steel or low alloy steel. However, when weld welding is performed in the circumferential direction of the steel pipe 11 as described above, since the weld material melted during overlay welding hangs down due to gravity, the weld beads positioned above and below are Even with the same lead rod pitch (pitch between adjacent weld beads) as when the steel pipe 11 is welded in the axial direction, the amount of welding material in the overlapped portion of the weld beads increases. This seems to increase the amount of Ni, lower the viscosity, and make the weld bead smooth with little unevenness. This also leads to uniform build-up thickness.
3 is a cross-sectional photograph of the steel pipe 11 when the steel pipe 11 is welded in the circumferential direction (FIG. 3A) and when the steel pipe 11 is welded in the axial direction as in the prior art (FIG. 3B). Is shown. As apparent from FIG. 3, the build-up welding thickness becomes uniform when the steel pipe 11 is build-up welded in the circumferential direction.
In this way, by making the thickness of overlay welding uniform, it is also easy to measure and manage the overlay thickness during overlay welding, and the effect of reducing the material cost by reducing the amount of welding material used. can get.

By the way, in the above, build-up welding is performed in the circumferential direction of the steel pipe 11, but the welding arc is in contact with the steel pipe 11 because the welding torch 40 and the substantially arc-shaped rail 30 interfere with another adjacent steel pipe 11. In some cases, the entire range of the surface of the steel pipe 11 that does not reach the joint of the plate 12 and faces the inner side of the furnace wall 10 cannot be welded.
In such a case, as shown in FIG. 4, as for the joint portion A of the steel pipe 11 and the plate 12, overlay welding is performed in the axial direction of the steel pipe 11 as in the prior art, and the remaining part B of the steel pipe 11 is Similarly, overlay welding may be performed in the circumferential direction. Even in that case, the same effect as described above can be obtained for the portion welded in the circumferential direction.

Further, the welding torch 40 is placed in a predetermined direction (in the case of FIG. 1 in the circumferential direction, in the case of FIG. 4 only the portion A of the joint between the steel pipe 11 and the plate 12 is the axial direction of the steel pipe 11 and the remaining portion B is in the circumferential direction). When carrying a rod, so-called weaving or oscillation can be performed in which build-up welding is performed while finely shaking the welding torch 40 in a direction substantially perpendicular to the carrying rod direction (width direction of the weld bead). For this purpose, while moving the welding torch 40 along the rail 30, the torch holding part 25 may be moved up and down with a constant width along the axial direction of the steel pipe 11, but the configuration shown in FIG. 5 is used. It is effective to vibrate only the tip 40 a of the welding torch 40 with the permanent magnet 41 and the electromagnet 42. As such a welding torch 40, the structure described in JP-A-6-15449 can be used.
If it does in this way, the width of a weld bead will become wide and welding can be performed efficiently. Thus, when weaving is performed in a direction (axial direction of the steel pipe 11) substantially orthogonal to the welding torch 40 while moving the welding torch 40 in the circumferential direction of the steel pipe 11 as shown in FIG. Thus, the torch angle with respect to the surface of the steel pipe 11 of the welding torch 40 is always constant. On the other hand, when the welding torch 40 is moved in the axial direction of the steel pipe 11 as in the prior art and the tip of the welding torch 40 is vibrated in a direction substantially perpendicular to the welding torch 40, weaving is performed as shown in FIG. Since the steel pipe 11 is circular, the torch angle of the welding torch 40 with respect to the surface of the steel pipe 11 and the distance between the welding torch 40 and the surface of the steel pipe 11 also vary depending on the position. This also leads to uneven build-up thickness, but such a problem does not occur if the configuration is as in the present embodiment. That is, when performing weaving, it is particularly effective to perform overlay welding in the circumferential direction as in the present embodiment.

In addition, in the said embodiment, although the structure about the welding apparatus 20 was demonstrated, as long as the steel pipe 11 can be welded in the circumferential direction, about the structure, even if it changes into any other structure good. Further, the welding material and the material of the object of overlay welding may be any other material.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

It is a figure which shows the build-up welding method of the steel pipe in this Embodiment. It is a figure which shows the whole structure of a build-up welding apparatus. (A) shows the cross-sectional photograph of the steel pipe at the time of overlay welding of the steel pipe in the circumferential direction, (b) shows the steel pipe at the time of overlay welding at the axial direction. It is a figure which shows the example in the case of performing overlay welding only to the both ends of a steel pipe in the axial direction of a steel pipe. It is a figure which shows schematic structure of the welding torch for performing oscillation. (A) It is a figure which shows the comparison at the time of oscillating in the axial direction of a steel pipe, and the case where (b) oscillating in the circumferential direction of a steel pipe. It is a figure which shows the overlay welding method of the conventional steel pipe. It is a figure which shows the state which the unevenness | corrugation produced in the weld bead in the conventional method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Furnace wall, 11 ... Steel pipe, 12 ... Plate, 20 ... Welding device, 21 ... Base frame (frame), 23 ... Vertical rail (frame), 25 ... Torch holding part, 30 ... Rail, 31 ... Torch holder, 40 ... Welding torch

Claims (10)

A method of overlay welding a surface of a steel pipe,
Moving the welding torch in the circumferential direction of the steel pipe and overlay welding the surface of the steel pipe in the circumferential direction;
A step of moving the welding torch in the axial direction of the steel pipe by a dimension smaller than a width dimension of a weld bead formed on the surface of the steel pipe by a welding arc generated between the welding torch and the steel pipe. A build-up welding method for steel pipes.   The build-up welding in the circumferential direction is performed by moving a torch holding part holding the welding torch along an arc-shaped rail arranged substantially concentrically with respect to the axis of the steel pipe. The build-up welding method of the steel pipe of Claim 1 to do.   The steel pipe build-up welding method according to claim 1 or 2, wherein the steel pipe forms a furnace wall of a boiler by arranging a plurality of the steel pipes side by side.   The steel pipe according to claim 3, wherein the steel pipe is applied to the existing steel pipe forming the furnace wall, and in the step of moving the welding torch in the axial direction, the welding torch is moved downward. Overlay welding method.   5. The method for overlay welding of a steel pipe according to claim 1, wherein the welding material used for the overlay welding is a base metal and a co-metal material, a stainless steel material, or an Inconel material. .   6. The method according to claim 1, wherein when welding the surface of the steel pipe in the circumferential direction, the welding torch is reciprocated with a constant width in the axial direction while moving in the circumferential direction. The build-up welding method of the steel pipe in any one.   About the circumferential direction both ends of the steel pipe, the welding torch is moved in the axial direction to perform build-up welding, and the circumferential build-up is performed in a region between the portions in which the build-up welding is performed in the axial direction. The steel pipe overlay welding method according to any one of claims 1 to 6, wherein welding is performed. A frame set along the inner peripheral surface of the boiler furnace wall;
A torch holding portion that is supported so as to be movable along the inner peripheral surface of the furnace wall with respect to the frame and holds a welding torch for overlay welding a steel pipe constituting the furnace wall;
The torch holding part is configured to be able to build-up weld the steel pipe along the circumferential direction of the steel pipe with the welding torch by moving along an arc-shaped rail. Welding equipment.   The build-up welding apparatus according to claim 8, wherein the frame supports the torch holding part so as to be movable at least in an axial direction of the steel pipe in a plane substantially parallel to the furnace wall.   The overlay welding apparatus according to claim 8 or 9, wherein the torch holding portion keeps an angle of the welding torch with respect to a surface of the steel pipe constant when moving along the rail.

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