EP1976657A1

EP1976657A1 - Welding process

Info

Publication number: EP1976657A1
Application number: EP07722762A
Authority: EP
Inventors: Roger Müller; Johannes Fisch
Original assignee: Schmidt and Clemens GmbH and Co KG
Current assignee: Schmidt and Clemens GmbH and Co KG
Priority date: 2006-01-23
Filing date: 2007-01-23
Publication date: 2008-10-08
Also published as: CN101415515B; DE102006033992A1; CN101415515A; CA2639918A1; BRPI0706665A2; US20090212024A1; JP2009523615A; WO2007098827A1

Abstract

In a welding process for joining the end of a first pipe to the end of a second pipe by means of a welding seam along a circumferential joint, the first and second pipes are arranged relative to one another in the position required to form the circumferential joint, a coolant-discharging cooling body is inserted into the first and/or second pipe in such a way that the coolant discharged can cool at least one of the pipes, in the region of the end being welded, the pipes and a welding torch are moved relative to each other along the circumferential joint, in order to form the welding seam, and welded by the welding torch, and the coolant is discharged at predetermined intervals.

Description

"Fusion"

The invention relates to a method of welding and more particularly to the use of a welding method for welding stainless steel tubes, nickel-based tubes, especially nickel-based tubes with high carbon content and centrifugally cast tubes.

When welding tubes together, either in fixed tubes of the welding torch along the peripheral joint in a plane perpendicular to the longitudinal axis of the tubes is moved around the tube ends or fixed at a fixed torch, the first and the second tube synchronously by means of corresponding embodiments of the holders holding them under the Welding torch rotated so that the welding torch can close the circumferential joint by means of a weld.

EP 0 884 126 B1 describes a possible procedure for producing the weld seam by means of a pivoting welding torch. The complicated sequence described in EP 0 884 126 B1 individual, performed only on circular arc segments in one piece welds with varying directional guidance of the welding torch show what complex measures are taken to produce a high-quality weld. In practice, one or more of the nachfofgenden goals is verfofgt: Through welding of the root, low number of Füllschweißungen, good connection of a first weld to the second weld and the least possible structural change of the pipe material in adjacent to the weld area.

Against this background, the object of the invention is to propose a welding method which enables economical and, in particular, device-less welding and in particular enables good welding of stainless steel tubes, nickel-based tubes, nickel-based tubes with high carbon contents and centrifugally cast tubes. The object is achieved by a welding method according to the independent claims 1 and 6. Advantageous embodiments are specified in the subclaims.

The invention is based inter alia on the fact that, in particular during welding, a coolant is to be applied, which can cool at least one of the tubes in the region of the end to be welded and that this coolant should not be applied continuously during the welding process but only at certain intervals. For example, as part of a welding program, it may be provided to first weld a root pass without cooling by dispensing coolant. This has the advantage that the discharged inside the pipe / tubes coolant does not push the resulting root layer from the inside out and thus creates an unwanted seam shape. According to such an embodiment of the invention can then take place, for example, for the welding of the applied to the root pass filling or cover layer, a cooling of the tube / tubes by applying coolant. The discharge of the coolant would therefore be limited, for example, to the specific time interval of welding the cover layer.

The idea according to the invention of not applying the coolant permanently, but only at quite specific intervals, can also be applied to other intervals. For example, the interval does not have to be defined in terms of time, but can be determined as a function of the burner tip position or the burner tip position. For example, it may be defined in a controller that whenever the torch tip is in a particular position and / or position, coolant is dispensed.

The invention is thus based on the basic knowledge that the discharge of the coolant can be used specifically from influencing factor for the shape of the weld, so for example, can be used for certain shape of the root pass (you want to push them outward) or at certain positions of the welding torch, For example, arranged at the side of the tubes burner tip, can ensure that even in this welding position a desired seam shape is achieved. In addition to this knowledge that the coolant can be used as a targeted design element of the seam shape, the inventive limitation of the coolant output to certain time intervals offers the advantage of lower coolant consumption. According to the invention, the coolant is therefore not constantly applied during welding, but only at certain intervals. The intervals can always be the same length. Preferably, however, the length of the time interval is varied by a controller, for example as a function of a selected welding program. This allows for different sections the welding process to provide a different cooling of the pipe ends and thereby offers the advantage of further optimization of the coolant consumption.

The discharge of the refrigerant at certain intervals may be controlled by the operator himself, for example by opening and closing a supply valve. Particularly preferably, the control, or even the regulation of the discharge of the coolant via a controller, or via a control. Various welding programs can be stored in this control or regulation, with each program being assigned a specific sequence of specific intervals. Depending on the type of pipes to be welded, the operator can then select the best welding program for this purpose, depending on the pipe materials, the pipe dimensions, the weld seam preparation or the like.

The welding process used is particularly preferably the tungsten inert gas welding process (TIG welding process), which is well known as such. It has been shown that the advantages of the invention can be implemented particularly well in this method. The welding torch preferably has an inert gas supply, which can be made movable with the burner as well as stationary. Furthermore, a wire feed can be provided for the welding material. Welding material may optionally be supplied when welding individual layers or, for example, a complete layer may be welded without supplying welding material.

In the embodiments of the method according to the invention described hereinbefore and hereinafter, the first tube and the second tube are welded together at the end. In this case, tube is understood to mean both the long body of the actual word "pipe" and a pipe bend, the tubular shoulder of a T-piece or any other body which has a substantially annular, in particular annular, end face in cross-section.

The end-side end surfaces of the tubes can be untreated or subjected to a weld preparation. For example, the end surfaces can be beveled to produce a V-seam or other seaming. Particularly preferably, the end face is partly perpendicular to the tube axis formed obliquely to the tube axis, so that, for example, the root layer as I-seam and the top layer or filling layer are welded as a V-seam.

When assigning the tubes in the necessary for the formation of the peripheral joint position, the tubes are arranged in particular so that as possible no transitions occur at the outer peripheries. The tubes to be welded often do not have an exact circular cross-section, for example, have slightly varying Wall thicknesses and / or, for example, an outer peripheral shape different from the inner peripheral shape, for example an elliptical outer peripheral shape. Advantages are now achieved when the tubes are aligned with each other so that the two outer circumferences are aligned as possible. For example, while the tubes could be coaxially aligned, it is preferred that the outer circumference be used as a measure of the orientation of the tubes relative to each other. Particularly preferably, the tubes are mediated to each other so that there is a minimum offset both on the inside and on the outside. The mutually aligned tubes can be non-rotatably connected to each other by selective welding ("stapling"). As a result, the other tube is rotated during rotation of a tube. Under circumferential joint is also the immediate, for example, jerky Aneinanderetzen understood to connect the pipe cross-sections, even if there is no or only a minimal gap between the pipe ends.

With regard to the mounting of the tubes, in the embodiments described hereinbefore and hereinafter, the tube can hold the tube in a rotationally fixed manner to the holder, for example in the receptacle of a rotary drive. In particular, however, the holder is designed as a pure support for the tube. For example, the support may be circular arc-shaped in cross-section and have rollers in this cross-section, on which the inserted into the support tube can roll when it is rotated about its tube axis. The holding a pipe holder is preferably formed so that it holds the tube in a raised, horizontal position. In particular, the bracket engages the outside of the pipe. For the purposes of this invention is understood as a holder for a pipe but also any other requirement for a pipe or roller supports for pipes (linets) or even a laying on the floor.

According to another basic aspect of the invention, the tubes are welded to the multi-layered weld by the welding torch, the torch being held in a first welding position to produce a first layer and a second position in a second welding position to produce a second layer. The first welding position differs from the second welding position with respect to the position of the burner tip with respect to a zero position in which the burner tip is arranged vertically above the upper vertex (dead center) of the tubes, and / or with respect to the position of the longitudinal axis of the welding torch in Relation to the horizontal. In this case, not only the root position is to be understood as "first position", since the knowledge according to the invention can also be applied to the sequence of other layers, for example a first filling layer and a second filling layer or a filling layer and a cover layer.

This offers the advantage that the individual layers with for the welding of the respective Position optimal orientation of the welding torch can be generated. For example, it has been found that a root pass can be produced particularly favorably with a torch tip which is in a first welding position with a first position and with a first orientation of the longitudinal axis, while, for example, a covering position or a filling position preferably with a different welding position is produced. The burner tip is preferably held stationary in the one welding position for producing a complete position, wherein a "complete layer" can also be understood as meaning a slight over-welding. After this first layer is created (including a possible slight Überweißens), the welding process can be interrupted and the welding torch are brought into a second welding position.

In a preferred embodiment, the tubes and the welding torch are moved relative to each other in a first direction to produce the first layer of the weld and moved in the first opposite direction to produce the second layer of the weld. Namely, depending on the position to be welded and the welding position, it may be advantageous to move the tubes once in the manner of a rising seam and once in the manner of a falling seam relative to the welding torch.

In a preferred embodiment of the invention, it is provided to reduce the intended pivoting range for the burner and to move it only along a circular arc segment which is smaller than 180 ° degrees. Thus, the very complex structures that provide a pivoting of the burner along the entire circumferential joint, ie by 360 ° degrees, can be avoided. At the same time, this welding method allows setting of different relative velocities between the tube and the burner. For example, the burner can be moved in one direction within its arcuate segment and the tubes in the other direction by means of its (then driven) brackets, if that is advantageous for a particular circular arc segment, while in other circular arc segments the tubes are stationary to hold and only to move the burner in its circular arc segment.

The pivoting device for the burner preferably has a holder in which the welding torch is held with its possibly provided additional elements. This holder is preferably directly or by the interposition of a holding arm along a backdrop, such as a circular arc-shaped rail, movable and held to it. In this case, a rail is understood as meaning both a body that has been shaped to a conventional rail body and any other body along the surface of which the holder is directly or indirectly supported a pivotal movement of the burner along the inventively limited circular arc segment can complete.

The advantage of this aspect of the invention lies in the fact that a rail - as it is provided as a guide for the holder - must not be led around the pipes to form a complete circle. But even with an invention also possible use of a pivot arm as a support for the support of the welding torch benefits are achieved because the pivot arm must perform only limited movements to move the burner according to the invention along the circular arc segment. It is no longer necessary to form the pivot arm so that it can fully embrace the pipes to be welded.

According to a further aspect of the invention, in the welding method, the longitudinal axis of the burner is tilted by a tilting device about a tipping point from a first to a second position. According to the invention, the burner can be moved in this tilted position to form the weld along the peripheral joint. In this case, the longitudinal axis of the burner is preferably tilted within the plane perpendicular to the longitudinal axis of the tube from the usual radially aligned to the tubes layer in an angle to the radial direction of the tubes at an angle. It has been found that the weld can be better produced with a tilted burner. This is especially true when the longitudinal axis of the burner for generating the weld is tilted away from top dead center. For example, a weld may be produced in the inventive welding process in which the torch is radially aligned with the tube at top dead center and then moved down a circular arc segment, during which downward movement the degree of tilt of the longitudinal axis may be changed from the radial orientation.

In a preferred embodiment, the tilting point is provided in the region of the burner tip. It has been found that the control of the welding method according to the invention can be programmed more easily if the burner tip is defined as a fixed point. For the control, it is advantageous if the movement of the burner tip along the selected arc segment is determined and the tilting of the burner is added as an additional effect, but does not change the position of the burner tip on the circular arc segment.

In a preferred embodiment of the welding method, a rotary drive rotates one of the tubes held in one of the holders in a clockwise and counterclockwise direction about its longitudinal axis. This reversal of the direction of rotation makes it possible to increase the relative movements between the burner tip and the two welding pipes. Also, this reversal of direction makes it possible to quickly reach the start point of the next weld when juxtaposing individual welds, because reversing the direction allows the shortest path from the end point of the just ended weld to the starting point of the next starting weld to be selected.

In a preferred embodiment, a heat sink, which can cool the tube from the inside, at least inserted into a tube. Such a heat sink makes it possible to introduce cooling gas from the inside to the tube ends and thus to achieve interpass temperatures which cause only a small shrinkage in the weld region, or to prevent or at least reduce, for example, structural changes in the material of the tube in the region of the weld.

In particular, the heat sink preferably has an outlet section with at least one outlet for a coolant and sealing lips projecting from the heat sink and delimiting the outlet section. Particularly preferably, the heat sink is of cylindrical construction and has two annular disks as sealing lips, which delimit the outlet section provided on the mantle surface of the cylindrical heat sink in each case at the end. Preferably, the sealing lips are made at least in their outer edge portions of elastic material. Thus, the heat sink can be easily pulled out of the tube after completion of the welding. In many cases, the heat sink is partially pushed beyond the end region of the first tube into the end region of the second tube, so that the outlet section is arranged below the peripheral joint. The elastic formation of the sealing lip now makes it possible to pull the heat sink out of the tubes even when the root of the weld projects into the interior of the connected tubes. If the sealing lip were not elastic in this area, it could not be moved over the bead of the weld root. The sealing lips may preferably be designed to be interchangeable in order to allow easy adaptation to different inner cross sections of the pipes to be welded.

Most preferably, the above-described welding methods are used to weld stainless steel tubes, nickel-based tubes, high carbon nickel-based tubes, and / or centrifugally cast tubes.

In the following, we will explain the invention in more detail on the basis of a drawing showing only an exemplary embodiment of the invention. Show:

Fig. 1 is a schematic side view of an apparatus on which the welding method according to the invention can be carried out; Fig. 2 is a schematic plan view of the device according to FIGS. 1 and

Fig. 3 is a sectional side view of an inserted into two tubes to be connected heat sink.

Fig. 1 shows a first tube 1 and a second tube 2, which are to be connected along a peripheral joint 3 by means of a weld. For this purpose, a welding torch 4 is provided. The tubes 1, 2 are located on linets 5, 6. A drive device 7 is provided to drive the tube 1 in rotation. The drive device 7 is designed such that it can rotate the tube 1 both clockwise and counterclockwise, as shown by the double arrow A in FIG.

Fig. 2 shows details of the welding torch apparatus. The welding torch 4 can be tilted about a tilting point 8 in both directions of the double arrow B by means of a tilting device, not shown. Kippositionen of the welding torch 4 are indicated in Fig. 2 with lighter line width. Furthermore, the welding torch device has a pivoting device, not shown, by means of which the welding torch 4 can be moved along a circular arc segment 9. The circular arc segment is <180 °.

Fig. 3 shows a heat sink 10 which is inserted into the tube 2 and the tube 1, that it is arranged symmetrically to the circumferential joint 3. The heat sink 10 has flexible sealing disks 11, 12. A cylindrically shaped main body 13 has outlets 14 for a coolant, which are supplied to the main body 13 via a feed line 15.

For connecting the first tube 1 to the second tube 2, the first and the second tube 1, 2 are arranged in the position necessary for the formation of the peripheral joint 3 to each other, in which they are placed on the linets 5, 6. Furthermore, the pipes are arranged such that a good compromise between an offset on the outside and an offset on the inside is achieved. An attempt is made to minimize the offset on both sides. Subsequently, the tube 2 is selectively connected to the tube 1 by means of stitching, so that a rotational movement then generated by the drive device 7 is transmitted from the tube 1 to the tube 2. Further, the heat sink 10 is inserted into the tubes 1, 2 in such a way that it is arranged symmetrically under the peripheral joint 3. Subsequently, the tube assembly of tube 1 and tube 2 is rotated by means of the drive device 7. Through the welding torch 4, the root position of the weld to be produced is generated during the rotation. To generate the following filling the welding torch 4 by means of the tilting device and the Pivoting device transferred to another position. The rotation of the tube assembly is reversed and welded with these settings, the filling. For this or a later filling is discharged via the heat sink coolant. The application of the coolant is limited to the interval of a rotation of the tube by 90 °. Thereafter, the coolant supply is interrupted for the further 90 ° rotation angle of the tube and then switched on again for 90 °. Finally, the top layer is welded. For this purpose, the welding torch 4 can again be brought into a new tilt position and a new pivot position. After completion of the welding process, the heat sink is pulled out of the pipe assembly. The elastic design of the sealing lip also allows the heat sink to be pulled out of the tubes, the root of the weld protruding into the interior of the connected tubes.

Claims

claims:

Welding process for the end-side connection of a first tube (1) with a second tube (2) along a peripheral joint (3) by means of a weld, in which

the first and the second tube (1, 2) are arranged in the position necessary for the formation of the peripheral joint (3), a cooling body (10) for discharging coolant into the first and / or the second tube (1, 2) is inserted so that the coolant discharged by him can cool at least one of the tubes in the region of the end to be welded, the tubes (1, 2) and a welding torch (4) for generating the weld along the peripheral joint are moved relative to each other and through the Welding torches are welded and the coolant is applied at certain intervals.

2. A welding method according to claim 1, characterized in that the discharge of the coolant in the predetermined time interval is effected by a controller.

3. Welding method according to claim 2, characterized in that the controller can vary the length of the time interval.

4. Welding method according to one of claims 1 to 3, characterized in that the first tube (1) in a first holder and the second tube (2) in a second holder to form a peripheral joint (3) between the first and the second tube is held and the tubes (1, 2) rotated during welding with the peripheral joint on a welding torch (4) and / or the welding torch is pivoted at least partially along the circumferential joint by means of a pivoting device and at least one tube in the region of its end to be welded by means of a coolant introduced into the tube is cooled, in which the coolant is applied at certain intervals.

5. Welding process according to one of claims 1 to 4, characterized by the use of the tungsten inert gas welding process (TIG welding process).

6. Welding method for the end-side connection of a first tube (1) with a second tube (2) along a peripheral joint (3) by means of a weld, in which

the first and the second tube (1, 2) in the for the formation of the peripheral joint (3) necessary position to each other, the tubes (1, 2) and a welding torch (4) for generating the weld along the peripheral joint (3) are moved relative to each other and welded to a weld with multiple layers by the welding torch and the welding torch (4 ) for maintaining a first position in a first welding position and for generating a second position in a second welding position, wherein the first welding position from the second welding position with respect to the position of the burner tip with respect to a zero position in which the burner tip vertically above the is arranged at the top apex of the tubes, and / or differs with respect to the position of the longitudinal axis of the welding torch with respect to the horizontal.

7. A welding method according to claim 6, characterized in that the tubes (1, 2) and the welding torch (4) for generating the first layer of the weld are moved relative to each other in a first direction and for generating the second layer of the weld in the first opposite direction to be moved.

8. Welding method according to one of claims 6 to 7, characterized by the use of the tungsten inert gas welding process (TIG welding process).

9. Welding method according to one of claims 6 to 8, characterized in that a cooling body (10), which can cool the tube from the inside, at least inserted into a tube.

10. Welding method according to one of claims 6 to 9, characterized by one or more of the method steps of a method according to one of claims 1 to 5.

11. Welding method according to one of claims 1 to 10, characterized in that the first tube (1) is held in a first holder and the second tube (2) is held in a second holder, wherein the first and the second holder the first and the second tube in the position necessary for the formation of the circumferential joint (3) hold each other, the welding torch (4) for producing the weld by means of a pivoting device, the burner with its burner tip along a circular arc segment of a substantially vertical longitudinal axis of the tube circle move only along a circular arc segment that is less than 180 degrees.

12. Welding method according to one of claims 1 to 11, characterized in that the first tube (1) is held in a first holder and the second tube (2) is held in a second holder, wherein the first and the second holder, the first and the second tube in the position necessary for the formation of the peripheral joint (3) hold each other and the longitudinal axis of the welding torch (4) for generating the weld around a tilting point (8) is tilted by means of a tilting device from a first to a second position.

13. Welding method according to claim 12, characterized in that the tilting point (8) is in the region of the burner tip.

14. Welding method according to one of claims 1 to 13, characterized in that at least one of the tubes held in one of the holders can rotate by a rotary drive in a clockwise and counterclockwise direction about its longitudinal axis.

15. A welding method according to claim any one of claims 1 to 5 and 9 to 14, characterized in that the cooling body (10) has an outlet portion with at least one outlet for a coolant and of the heat sink (10) projecting sealing lips which define the outlet portion ,

Use of a welding method according to any one of claims 1 to 15 for welding stainless steel pipes, nickel-based pipes, nickel-based high carbon pipes and / or centrifugally cast pipes.

17. Heatsink for cooling a pipe from the inside, characterized by a base body (13) and at least one end side of the heat sink protruding, elastic sealing lip.

18. A heat sink according to claim 17, characterized in that the sealing lip is arranged in a plane perpendicular to the longitudinal axis of the cylindrical base body (13).

19. A heat sink according to claim 17 or 18, characterized in that the sealing lip as an annular disc (1 1, 12) is formed.

20. A heat sink according to any one of claims 17 to 19, characterized by a coolant supply to the interior of the base body (13) and at least one coolant outlet (14), which leads from the interior of the body to the outside.

21. Use of a heat sink (10) according to any one of claims 17 to 20 in a welding method according to one of claims 1 to 15.