EP0512633B1 - Procédé pour traiter postérieurement la trace focale d'une anode rotative sur tubes à rayons X - Google Patents

Procédé pour traiter postérieurement la trace focale d'une anode rotative sur tubes à rayons X Download PDF

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Publication number
EP0512633B1
EP0512633B1 EP92201234A EP92201234A EP0512633B1 EP 0512633 B1 EP0512633 B1 EP 0512633B1 EP 92201234 A EP92201234 A EP 92201234A EP 92201234 A EP92201234 A EP 92201234A EP 0512633 B1 EP0512633 B1 EP 0512633B1
Authority
EP
European Patent Office
Prior art keywords
melting
ray
manufacturing
rotary anode
focal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP92201234A
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German (de)
English (en)
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EP0512633A3 (en
EP0512633A2 (fr
Inventor
Peter Dr. Rödhammer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Metallwerk Plansee GmbH
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Metallwerk Plansee GmbH
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Application filed by Metallwerk Plansee GmbH filed Critical Metallwerk Plansee GmbH
Publication of EP0512633A2 publication Critical patent/EP0512633A2/fr
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/14—Manufacture of electrodes or electrode systems of non-emitting electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/08—Anodes; Anti cathodes
    • H01J35/10—Rotary anodes; Arrangements for rotating anodes; Cooling rotary anodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J2235/00—X-ray tubes
    • H01J2235/08—Targets (anodes) and X-ray converters
    • H01J2235/085—Target treatment, e.g. ageing, heating

Definitions

  • the invention relates to a method for producing an X-ray rotary anode with a base body made of refractory metals or graphite, or a combination of both materials as a base material with an annular focal path region made of refractory metals, which is produced by powder metallurgy or by means of CVD or PVD processes, e.g. Tungsten or tungsten rhenium.
  • X-ray rotary anodes Today, high-melting metals or graphite, or a combination of both materials, are used as the base material for X-ray rotary anodes.
  • the actual generation area of the X-rays, the focal path area consists of tungsten, molybdenum or their alloys.
  • Metallic X-ray rotary anodes are manufactured according to sintered metallurgical processes for reasons of shape, the materials used and the required properties; the focal path area itself is produced using sintered metallurgical processes or more recently also using CVD or PVD coating processes.
  • Such rotating anodes or focal path areas have a residual porosity in the range of 0.1-10% in the finished state, measured on the theoretical density.
  • Such an X-ray rotary anode is described in EP-A-0 116 385, the rotary anode optionally being post-treated and heat-treated after the focal path layer has been applied in accordance with the process there.
  • This residual porosity has a number of disruptive disadvantages for the operation of X-ray rotary anodes, which is generally carried out in a high vacuum.
  • the porosity causes the release of gases trapped in the pores. This in turn leads to gas discharges in the high vacuum of the tube with undesirable tube short circuits, which in turn cause anode melting.
  • the thermal conductivity that is so important for the resilience of X-ray tubes decreases about with the square of the porosity.
  • Porosity of the focal track surface causes increased surface roughness and reduces the X-ray yield due to self-absorption.
  • porous surfaces also mean the risk of particle breakouts from the surface, which significantly increases the negative effects of gas leaks.
  • the mechanical bonding of the individual crystallites in the structure depends on the porosity, but also on the metallurgical conditions at the grain boundaries, in particular on impurities at the grain boundaries. In the course of powder metallurgical manufacturing processes, however, a concentration of impurities that are insoluble in the metal at the grain boundaries is unavoidable; this means another disruptive factor when operating X-ray anodes.
  • Focal path linings produced by sintered metallurgical processes in particular made of tungsten-rhenium, occasionally show a brittle, intermetallic tungsten-rhenium phase, the so-called sigma phase, which is due to inhomogeneities due to inadequate mixing of the individual alloy components in the powder batch.
  • the inevitable thermal shock loading of rotating anodes during operation then leads, particularly in these and in the areas emanating from them, to highly undesirable crack formation, with a reduction in the X-ray yield in the focal path area as a result.
  • DE-C-10 11 533 describes a "method for increasing the puncture resistance of X-ray tube anodes made of high-melting sintered metals". The process is tailored for use with standing anodes. In the course of the manufacture of the tube, the anode, which has residual porosity, is melted on the surface and it becomes the Anode surface is compressed due to the cohesive forces that become effective during solidification. A more homogeneous structure and thus higher density and thermal conductivity are mentioned as advantages.
  • JP-A 2-10628 describes a method for producing an X-ray rotating anode.
  • the focal path of the rotating anode is heated to recrystallization temperature or above before use in order to remove the residual gas present in the rotating anode.
  • the annealing temperature is preferably 2200 ° or above.
  • JP-A 54-52487 mentions a method for producing an X-ray composite anode.
  • the tungsten or tungsten alloy coating initially applied as a paste is converted into a molten phase by means of a laser beam and solidified on the underlying substrate well connected with this.
  • the object of the present invention is then the elimination or a substantial reduction in the aforementioned disadvantages.
  • the task is to reduce the porosity and the impurities, especially at the grain boundaries in the focal path area.
  • the previous manufacturing processes prowder metallurgy and CVD or PVD processes
  • the object is achieved according to the invention by a method according to which the focal path area of an X-ray rotary anode is aftertreated at a depth of less than 1.5 mm by means of local, superficial melting.
  • the inventive aftertreatment by means of superficial melting is carried out in accordance with a method which has been tried and tested in practice by the action of focused beams of high-energy electrons or photons on the surface of the focal path area of X-ray rotary anodes down to a certain depth of action.
  • a changed metallic structure is formed in this area, the porosity and the proportion of impurities, in particular in the grain boundary area, are significantly reduced.
  • the grain structure remains comparatively fine in contrast to conventional melt metallurgical processes.
  • the grain size that can be achieved corresponds to that which is customary in powder metallurgy or by means of application methods of the focal path regions.
  • the melting can be carried out once or several times in succession and influences the metallic structure of the focal path area that can be achieved in the final state. With the removal of the residual porosity, the previous disturbances in the operation of x-ray rotary anodes shown at the beginning also disappear.
  • Suitable focusable energy sources for the melting process are the laser, devices for generating particle beams, in particular electron beams, and highly focusable high-power lamps.
  • the material-related degree of conversion of radiated energy / heat is important for the energy source selected in the individual case.
  • the equipment complexity and the processing e.g. B. Treatment under protective gas or in a high vacuum, a role. Due to the high reflectivity of refractory metals for electromagnetic waves in the spectral range 0.3 - 20 ⁇ m (> 80%), the use of electron beams with an efficiency of ⁇ 60% usually offers advantages.
  • the desired melting depth according to the inventive method is to be dimensioned to match the thermomechanical loads to be expected during operation of the focal path area.
  • a melting depth between 0.05 and 1.5 mm has proven to be useful. In the majority of applications, a melting depth between 0.5 and 0.8 mm offers the best cost-benefit ratio.
  • the process of melting and rapid cooling results in the structure states being amorphous, very fine-grained isotropic, fine-grained or coarse-crystalline.
  • the resulting stresses in the structure can be reduced by a subsequent vacuum annealing in the range 900 - 1600 ° C.
  • the melting process leads to a very smooth surface with a low surface roughness in the focal path area. Nevertheless, due to the extremely high demands on the surface smoothness of X-ray rotary anodes in the focal path area, it is generally unavoidable to grind the surface after the melting process.
  • a rotary anode base body with a tungsten / rhenium focal track area which is manufactured in the usual powder metallurgical way, is - like later in operation - mounted on a rotating holding shaft and inserted into a piston that can be evacuated to high vacuum.
  • the rotating anode focal path area is arranged opposite a focussing glow emission cathode.
  • the slowly rotating rotating anode is brought uniformly to approx. 800 ° C by means of a defocused electron beam.
  • the rotating anode is degassed, which means that foreign atoms and insufficiently adhering material particles are removed from the surface.
  • the electron beam is brought to a line focus of 20 mm in length and 2 mm in width and to an output of 6 kW and the rotating anode rotating at 3-6 revolutions per minute is melted on the surface in three successive revolutions.
  • the melt lying horizontally due to the arrangement solidifies during the subsequent cooling process so smoothly that even with subsequent ablation of 0.2 - 0.3 mm, a smooth burn sheet surface that meets the requirements is achieved by grinding.
  • the structure of a focal path region melted in this way has directionally solidified crystallites with an average diameter of 150 ⁇ m. It shows no pores and gives reliable information for an excellent bond between the individual grains or crystallites.
  • An X-ray rotary anode manufactured according to the present invention was compared with a rotary anode manufactured according to the prior art.
  • both comparison rotating anodes were tested with the following loading cycles: electron beam power 60 kW, focus 12 x 1.8 mm2, irradiation cycle 7 x 0.1 s (Sec ) with 0.1 s (sec) pause (corresponds to an x-ray) and 59 s (sec) cooling, total number of exposures 1200.
  • the two comparison rotating anodes were checked for their superficial structural changes both under a scanning electron microscope and measured for surface roughness using the stylus.
  • the roughening of the rotating anode according to the present invention due to material fatigue was not only less, but, based on the entire surface area of the focal path, was more uniform than with the rotating anode according to the prior art. Accordingly, the x-ray rotating anode according to the invention showed a more uniform and less dense crack network with smaller crack widths than the comparison anode according to the prior art.
  • the rotating anode according to the invention has a very high vacuum stability. This significantly shortens the so-called run-in phase, in which a rotating anode in the tube is heated under the electron beam with continuous evacuation of escaping residual gases and brought to operating conditions for the first time.
  • the electrical stability of the rotating anode during operation was perfect.
  • the X-ray dose per exposure measured at the end of the test was 20% higher in the rotary anode produced according to the invention than in the comparison anode according to the prior art. The life expectancy of the X-ray rotary anode was therefore significantly higher than that of the comparison anode due to the aforementioned quality improvements.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • X-Ray Techniques (AREA)
  • Analysing Materials By The Use Of Radiation (AREA)
  • Powder Metallurgy (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Light Receiving Elements (AREA)

Claims (9)

  1. Procédé de fabrication d'une anode rotative sur tubes à rayons X avec un corps de base constitué de métaux à point de fusion élevé ou de graphite ou d'une combinaison des deux matériaux comme matériau de base et avec une trace focale annulaire constituée de métaux à point de fusion élevé et fabriquée par des méthodes relevant de la métallurgie des poudres ou au moyen d'un procédé CVD ou PVD, caractérisé par le fait que la trace focale est traitée postérieurement par fusion locale superficielle sur une profondeur inférieure à 1,5 mm.
  2. Procédé de fabrication d'une anode rotative sur tubes à rayons X selon la revendication 1, caractérisé par le fait que la fusion s'effectue jusqu'à une profondeur comprise entre 0,05 et 1,5 mm.
  3. Procédé de fabrication d'une anode rotative sur tubes à rayons X selon la revendication 2, caractérisé par le fait que la fusion s'effectue jusqu'à une profondeur comprise entre 0,5 et 0,8 mm.
  4. Procédé de fabrication d'une anode rotative sur tubes à rayons X selon les revendications 1 à 3, caractérisé par le fait que la fusion s'effectue au moyen d'un rayon électronique focalisé.
  5. Procédé de fabrication d'une anode rotative sur tubes à rayons X selon les revendications 1 à 3, caractérisé par le fait que la fusion s'effectue au moyen d'un rayon laser.
  6. Procédé de fabrication d'une anode rotative sur tubes à rayons X selon les revendications 1 à 5, caractérisé par le fait que la surface de la zone fondue est lissée par des moyens mécaniques.
  7. Procédé de fabrication d'une anode rotative sur tubes à rayons X selon les revendications 1 à 6, caractérisé par le fait que la zone fondue est soumise de plus à un recuit.
  8. Procédé de fabrication d'une anode rotative sur tubes à rayons X selon les revendications 1 à 7, caractérisé par le fait que la fusion de la trace focale est répétée une ou plusieurs fois.
  9. Procédé de fabrication d'une anode rotative sur tubes à rayons X selon les revendications 1 à 8, caractérisé par le fait que le matériau de la trace focale est un alliage tungstène-rhénium.
EP92201234A 1991-05-07 1992-05-04 Procédé pour traiter postérieurement la trace focale d'une anode rotative sur tubes à rayons X Expired - Lifetime EP0512633B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AT0094791A AT397005B (de) 1991-05-07 1991-05-07 Verfahren zur herstellung einer röntgendrehanode
AT947/91 1991-05-07

Publications (3)

Publication Number Publication Date
EP0512633A2 EP0512633A2 (fr) 1992-11-11
EP0512633A3 EP0512633A3 (en) 1993-02-17
EP0512633B1 true EP0512633B1 (fr) 1994-07-20

Family

ID=3503501

Family Applications (1)

Application Number Title Priority Date Filing Date
EP92201234A Expired - Lifetime EP0512633B1 (fr) 1991-05-07 1992-05-04 Procédé pour traiter postérieurement la trace focale d'une anode rotative sur tubes à rayons X

Country Status (4)

Country Link
EP (1) EP0512633B1 (fr)
JP (1) JP3345439B2 (fr)
AT (2) AT397005B (fr)
DE (1) DE59200292D1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102008026910A1 (de) 2008-06-05 2009-12-10 H.C. Starck Gmbh Verfahren zur Herstellung von reinem Ammoniumperrphenat
DE102012217194A1 (de) 2012-09-24 2014-03-27 Siemens Aktiengesellschaft Herstellen eines Refraktärmetall-Bauteils
US11043352B1 (en) * 2019-12-20 2021-06-22 Varex Imaging Corporation Aligned grain structure targets, systems, and methods of forming

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD109768A1 (fr) * 1974-01-10 1974-11-12
NL8300251A (nl) * 1983-01-25 1984-08-16 Philips Nv Werkwijze voor het vervaardigen van een draaianode voor roentgenbuizen en zo verkregen anode.

Also Published As

Publication number Publication date
DE59200292D1 (de) 1994-08-25
AT397005B (de) 1994-01-25
EP0512633A3 (en) 1993-02-17
ATE108948T1 (de) 1994-08-15
EP0512633A2 (fr) 1992-11-11
ATA94791A (de) 1993-05-15
JP3345439B2 (ja) 2002-11-18
JPH05151891A (ja) 1993-06-18

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