Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H9/00—Machining specially adapted for treating particular metal objects or for obtaining special effects or results on metal objects
  • B23H9/10—Working turbine blades or nozzles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H5/00—Combined machining
  • B23H5/02—Electrical discharge machining combined with electrochemical machining
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H5/00—Combined machining
  • B23H5/04—Electrical discharge machining combined with mechanical working
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H5/00—Combined machining
  • B23H5/06—Electrochemical machining combined with mechanical working, e.g. grinding or honing
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
  • B23H5/00—Combined machining
  • B23H5/14—Supply or regeneration of working media
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
  • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
  • B23P15/02—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass turbine or like blades from one piece

Definitions

• the invention relates to a method for producing a component for a thermal machine, in particular for producing a component for a turbine, a compressor or an expander, in which a blank of the component processed by eroding at least in sections and the surface produced by erosion by superfinishing is processed further. Furthermore, the invention relates to a component for a thermal machine, which is produced by means of the inventive method.
• Thermal machines such as turbines, compressors or expander
• components some of which have very complex shapes, such as turbine blades.
• erosion is increasingly used, a thermal, erosive manufacturing process for conductive components, in which material is removed by electrical discharge processes between an electrode and the component.
• complex recesses can be formed by eroding, for example specially shaped grooves, pockets with complex cross-sectional shapes or the like.
• a disadvantage of the use of erosion is that the eroded surface portions, ie the surface portions at which the spark discharge took place, are covered with fine craters and the surfaces show a pitted structure. Furthermore, in peripheral zones of the component, discharge processes, which are often associated with very high temperatures, lead to microstructural changes in the near-surface layer, whereby this near-surface layer is frequently interspersed with microcracks.
• This layer is also referred to as “recast layer” (also called recast layer) or “white layer”, wherein the thickness and nature of the recast layer, among other things, the setting parameters, the combination of tools and components, the desired surface roughness and Machine depends.
• the recast layer on the one hand no longer corresponds to the metallurgical structure of the base material used and thus has deviating properties, it is not desirable in particular in the manufacture of components for thermal machines.
• the recast layer has a comparatively high average roughness Ra in accordance with DIN EN ISO 3274 or DIN EN ISO 4287. This can be in a range of 3 to 4 microns, which is also undesirable for certain applications of components for thermal machines. For this reason, with thermal engine components, the recast layer has hitherto been removed by manual grinding processes.
• the object of the invention is to provide a method for producing components for thermal machines, with which components of complex shapes with high quality, in particular with high repeatability and surface quality, can be manufactured.
• this object is achieved by a method having the features according to claim 1 and, in particular, by the fact that fine machining or after a preceding superfinishing of the eroded surfaces is followed by sliding machining and / or electropolishing.
• electropolishing is also proposed for removing the recast layers.
• the recast layer can be completely removed by suitable selection of the electrolyte as well as by selective adjustment of the processing time, the current density and the electrolyte temperature, which can also be processed for the grinding inaccessible surface sections.
• targeted desired average roughness can be generated on the surface to be polished.
• the blank is produced for example by conventional methods, in particular by primary or forming such as casting, forging or the like and / or, in particular from forging or round material, prepared by machining processes for the inventive method.
• the erosion of the surfaces preferably takes place in several stages.
• the material removal is reduced on the one hand by the multi-stage erosion, on the other hand the influence on the structure of further internal layers is reduced. At the same time, this results in a low average roughness than in a single erosion with a larger material removal, which is advantageous for the subsequent superfinishing steps.
• the eroded body is placed together with grinding wheels and - preferably - a liquid, in particular water, in a working container, which oscillating for Gleitspanen and / or rotating movement performs.
• the abrasive particles are guided past the surfaces to be treated, wherein the removal of material takes place.
• ceramic abrasives are used as the abrasive body, which are mixed with appropriate abrasives.
• additives are preferably added to the liquid.
• additives can be added to the additives, which also promote the corrosion protection of the components and / or at the same time have a degreasing effect. If a pickling effect is to be achieved, it is also possible to add acidic additives. In the case of flat components, it is also possible to add mechanical release agents (for example small plastic beads) which prevent the components from adhering to one another.
• the removal of the recast layer during slip cutting can be additionally increased by the addition of chemicals to produce oxalate and phosphate compounds on the eroded surfaces.
• oxalate and phosphate coatings are produced in particular at the roughness peaks, which have a significantly lower hardness compared to the abrasives.
• the material removal during sliding machining can be further increased, while at the same time the average roughness can be further reduced.
• an additional polishing step can follow the sliding chip. If sliding lubrication is assisted by the addition of chemicals for the production of oxalate and phosphate compounds, the polishing can also take place immediately afterwards in the same working container, with the appropriate choice of polishing liquid.
• a polishing liquid is preferably added to the working container, which neutralizes the chemicals causing the production of oxalate and phosphate compounds and is inert to the material of the component.
• a polishing liquid for example, a mixture of phosphate salts and Gleitffentensi- is the.
• the eroded body is placed, at least with portions of its eroded surfaces, in an electrolyte bath of a material-specific electrode. submerged and switched as an anode. Subsequently, the workpiece is subjected to either constant or pulsed direct current. In particular, the use of pulsed current ensures that the recast layer dissolves particularly well from the eroded surface sections.
• the electropolishing can also be referred to simply as reverse plating.
• the material removal and the roughness of the surface can be set by specifying a defined processing time, a certain current density or by specifying a specific electrolyte temperature.
• the electrolyte used is preferably a mixture of water and inorganic acids. Depending on the material of the component, however, it is also possible to use other inorganic acids as the electrolyte, for example a mixture of phosphoric acid and sulfuric acid. The addition of alcohols is possible.
• slip chipping and electropolishing can be stated in different orders, for example, first sliding glazings with subsequent electropolishing or vice versa.
• the sliding machining and / or electropolishing can also take place in several stages, optionally alternately.
• the component After machining the eroded and treated by Gleitspanen and / or electropolishing surfaces, the component can be subjected to further processing steps, such as machining steps or steps for material or material hardening.
• the inventive method makes it possible for the first time to manufacture components for thermal machines with high repeatability and precision using erosion.
• the invention relates to a component for a thermal machine, which is produced by means of the method according to the invention.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
• ing And Chemical Polishing (AREA)

Applications Claiming Priority (2)

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• 2008
  • 2008-02-13 DE DE200810008894 patent/DE102008008894A1/de not_active Withdrawn
  • 2008-11-19 EP EP08872454A patent/EP2240290A1/de not_active Withdrawn
  • 2008-11-19 WO PCT/EP2008/009784 patent/WO2009100745A1/de active Application Filing
  • 2008-11-19 JP JP2010546220A patent/JP2011511716A/ja not_active Withdrawn
  • 2008-11-19 CN CN2008801268053A patent/CN101970165A/zh active Pending

Non-Patent Citations (1)

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