Patent Application
20120083346
This application is the US National Stage of International Application No. PCT/EP2010/058095 filed Jun. 9, 2010, and claims the benefit thereof The International Application claims the benefits of German Patent Application No. 10 2009 024 580.4 DE filed Jun. 10, 2009. All of the applications are incorporated by reference herein in their entirety.
The present invention relates to a method of testing a fusion weld for a shaft and to a device for testing a fusion welding operation of a shaft.
During fusion welding of rotor shafts, particularly in the field of turbine and generator construction, narrow-gap arc welding technology is used to assemble forged shaft parts into a complete rotor. An important quality criterion is the formation of a first tubular ring seam, i.e. a so-called first welding bead or root weld, because the dynamic properties of the rotor are crucially influenced by the shape and freedom from defects of this root. The core cross section of the shaft subsection is hollowed out by turning, i.e. the root weld produces a tubular ring seam. In order to inspect this root formation, the weld joints are generally X-rayed over the entire circumference in individual segments and hence the quality is checked. In many cases, after the root welding and after introducing some additional welding beads a second X-ray examination is carried out.
The X-ray examination is effected conventionally in such a way that an X-ray tube on the one side is directed in an axial direction towards the center of the ring. On the opposite side a radiation-sensitive film is disposed, the darkening of which provides information about the seam quality. Depending on a thickness of the root seam and the diameter of the rotor some 8 to 20 segment radiographs at the circumference and, for each radiograph, exposure times of between approx. 4 and 11 minutes are required. Prior to this, the preheating of the rotor from approx. 100° C. to 170° C. that is required for the welding operation has to be reduced, namely to temperatures below 50° C., in order not to damage the film material. Cooling-down and re-heating phases for the final welding of the residual seam take a considerable amount of time, particularly in the case of large rotor masses.
An object of the present invention is, when carrying out narrow-gap arc welding of shaft subsections, in particular of a rotor shaft for a turbine and/or a generator, to improve a quality of a first tubular ring seam, i.e. of a first welding bead or root weld, in a simple and effective manner. The quality of the first tubular ring seam is moreover to be evaluated after and/or during the welding operation.
The object is achieved by a method and by a device as claimed in the claims.
According to a first aspect a method of inspecting a fusion welding operation of a shaft, in particular of a rotor shaft for a turbine and/or a generator, is proposed, which comprises the following steps: Produce at least two shaft subsections, which are symmetrical about an axis of rotation and comprise at least one cylinder coaxially along the axis of rotation and have in each case two main delimiting circular faces perpendicular to the axis of rotation; from the direction of at least one main delimiting circular face remove in each case a core region of in each case one shaft subsection about the axis of rotation in order to produce in each case an open recess in at least one of the cylinders within a remaining tubular web; position in each case two shaft subsections coaxially one on top of the other along the vertical axis of rotation, wherein in each case two webs are mutually adjacent and in each case two recesses forth a hollow space; in other words, a joining of two shaft pieces is effected in a known manner by placing the end faces, which are combined in each case in the form of an annular web, against/into one another. By virtue of the annular webs, the shaft pieces thus joined form a hollow space in the center of the shaft axis; produce a first tubular ring seam for the welded connection of the two webs by means of narrow-gap arc welding wherein, in one of the two shaft subsections a passage is produced from outside into the hollow space. The method is notable for the fact that an evaluation of a quality of the first tubular ring seam is effected from within the hollow space during and/or after the welding operation by means of a detection device or radiation source that is introduced through the passage into the hollow space.
Shaft subsections have in each case two main delimiting circular faces perpendicular to the axis of rotation. These are a bottom surface and a top surface of the shaft subsection, which comprises at least one cylinder positioned coaxially along the axis of rotation. This means that the bottom surface may be the bottom surface of a cylinder of the shaft subsection and the top surface may be the top surface of a further cylinder of the shaft subsection. If the shaft subsection has only one cylinder, then the bottom surface and the top surface are the bottom surface and the top surface of this cylinder. A first tubular ring seam is also referred to as a root weld.
A web is generally a raised area of material.
According to a second aspect a rotor shaft, in particular for a turbine and/or a generator, is manufactured by means of a method as claimed in the invention.
According to a third aspect a detection device or a radiation source for evaluating a quality of a first tubular ring seam from within a hollow space during and/or after the welding operation may be introduced through a passage into the hollow space.
For producing a root weld, in a conventional manner an axial bore of the rotor is used to flush the root interior with shielding gas. This bore may then be used additionally to introduce a detection device or radiation source. It is thereby possible to use the following effects either individually or in combination: Observe the root interior during the welding process; view and assess the root formation after the welding process; it is possible to dispense entirely with an X-ray examination because the seam formation may be evaluated immediately. Costly non-productive periods as a result of temperature changes with cooling-down and reheating of the rotor parts are avoided. The final welding of the seam joint may directly follow inspection.
Further advantageous developments are claimed in conjunction with the sub-claims.
According to an advantageous development the detection device may be an optical detection device. Given use of an optical detection device, it is possible to observe for example a coloring during the welding process and/or a size of the molten material. These sizes may advantageously be used to regulate the welding process.
According to a further advantageous development the optical detection device may be an endoscope or a video camera. Given the use of a video camera, a recording of the video signals for electronic image documentation is available as a quality demonstration record.
According to a further advantageous development the detection device may be a temperature detection device and/or infrared camera. In this way it is possible to use for example a root penetration temperature for metrological evaluation of the root weld. A surface temperature of the first ring seam may moreover be detected and evaluated.
According to a further advantageous development the welding operation may be regulated by means of the detection device during the welding operation on the basis of acquired data. Such data is particularly advantageously a size of the molten material of the ring seam, a coloring of the ring seam, a root penetration temperature or a surface temperature of the weld seam. Root penetration temperature is the temperature of the ring weld seam at the side of the hollow space, since a welding device is positioned from the opposite side.
According to a further advantageous development a power pulse current intensity and/or a voltage may be regulated as welding parameters of a welding device. These are particularly simple options for regulation purposes.
According to a further advantageous development the regulating may be carried out automatically. Equally, an operator of a welding device may regulate the welding operation manually on the basis of a video recording. According to the present invention it is possible to use the following effects either individually or in combination: observe the root interior during the welding process; view and assess the root formation after the welding operation; automatic online regulation of the welding parameters for optimum root formation, for example by means of a metrological evaluation of the root penetration temperature. In this way, by virtue of regulation good quality assurance that is independent of operator control is possible in a particularly advantageous manner.
According to a further advantageous development the radiation source may be an X-ray unit or an isotopic radiator. If the radiation source is an X-ray unit, the quality of the root weld may be effected by X-ray examination from the inside out. For this purpose only one web wall has to be X-rayed. Thus, compared to conventional X-raying less energy is expended for X-raying. There is moreover a marked effective improvement in the quality of the X-ray image.
According to a further advantageous development the passage may be produced by means of drilling along the axis of rotation through the shaft subsection with an open recess, from one side of the open recess.
According to a further advantageous development the passage may alternatively be produced by means of drilling along the axis of rotation through a shaft subsection, from a side without a recess.
According to a further advantageous development the narrow-gap arc welding may be tungsten inert-gas narrow-gap arc welding or gas metal arc welding.
The present invention is described in detail with reference to exemplary embodiments in conjunction with the figures, in which
The main delimiting circular faces 7 are therefore bottom and top surfaces of a cylinder 3 or bottom surface and top surface of two different cylinders 3. From at least one main delimiting circular face side in each case a core region of in each case one shaft subsection 5 is removed around the axis of rotation 2. In this way, on at least one main delimiting circular face side of a shaft subsection 5 an open recess 11 is produced. Such an open recess 11 has been produced in at least one of the cylinders 3. Around such an open recess 11 a tubular web 13 remains.
A web 13 is delimited in each case by a remainder of a main delimiting circular face 7. The inside and outside diameters of mutually adjacent webs 13 may be identical. According to an advantageous development the shaft subsections may be forged. Equally, shaft subsection end pieces may be forged.
According to a further advantageous development the removal of the core regions may be effected by turning, in particular by hollowing out by turning.
The portion of the rotor shaft 1 represented in
The circle at the top right of
Particularly suitable as narrow-gap arc welding is tungsten inert-gas narrow-gap arc welding. Other gas metal arc welding methods are equally possible. By means of a passage 18 produced in one of the two adjacent shaft subsections 5 a shielding gas may be introduced into the hollow space 15. According to
Furthermore, as an alternative to manual regulation by means of an operator, i.e. a welder, automatic regulation of the welding parameters for optimum embodiment of the first tubular ring seam 17 is possible during the welding operation. For example a root penetration temperature may be evaluated metrologically. By means of the regulation for example on the basis of a temperature measurement a power pulse current intensity of a welding device may be regulated. In this way the quality of the first tubular ring seam 17 may be effectively improved. It is further possible after the welding operation to position a radiation source 19a, for example an X-ray unit or an isotopic radiator, in the hollow space 15. Thus, a conventional X-ray examination of the first tubular ring seam 17 may be effected. X-ray examination from within makes it possible to X-ray merely a portion of a first tubular ring seam 17, which is represented in
From within, only one wall of two webs 13 that have been welded together has to be X-rayed. In this way a conventional X-ray examination is improved in that less energy is required and the quality of the X-ray images is improved. Welding parameters may be for example likewise a welding voltage of a welding device. A passage 18 may be produced alternatively by means of drilling along the axis of rotation 2 through a shaft part end piece 5a from a side without a recess. This is represented at the bottom of the upper representation in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2009 024 580.4 | Jun 2009 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP10/58095 | 6/9/2010 | WO | 00 | 12/7/2011 |
