Metal coil and method of its manufacture

Abstract

The present invention relates to a metal coil, in particular a tungsten coil. One aspect of the invention relates to a method of manufacturing said metal coil, a further aspect to the metal coil itself, and yet a further aspect to the use of the metal coil in a heat conduction vacuum gauge, a Pirani element, or as a glow filament.

1 . A method of manufacturing a metal coil, in particular a metal coil comprising or consisting of tungsten (W) or a tungsten alloy, wherein the method comprises the steps, in particular in the given order:
 a) winding a metal wire, in particular a metal wire comprising or consisting of tungsten (W) or a tungsten alloy, onto a carrier, in particular a rod-shaped carrier;   b) heating the metal wire wound on the carrier; and   c) separating the heated metal wire from the carrier or a remaining remnant of the carrier, which carrier or remaining remnant of the carrier has a reduced diameter as a result of step b) compared to the carrier of step a), thereby obtaining the metal coil.   
     
     
         2 . The method according to  claim 1 , wherein the carrier of step a) comprises an organic material, optionally consists of an organic material, wherein the material is in particular a natural or synthetic polymer, a non-polymer compound, or a mixture thereof. 
     
     
         3 . The method according to  claim 2 , wherein the carrier of step a) further comprises an inorganic core and the organic material is arranged in the form of a sheath around the inorganic core, wherein the inorganic core is in particular a glass fiber, a carbon fiber, a mineral fiber, a silica fiber, a ceramic fiber, or asbestos. 
     
     
         4 . The method according to  claim 1 , wherein the carrier of step a) consists of a material, which material has a negative coefficient of thermal expansion, in particular under the heating conditions in step b). 
     
     
         5 . The method according to  claim 2 , wherein the carrier of step a) comprises a material, which material has a negative coefficient of thermal expansion, in particular under the heating conditions in step b), optionally wherein the core of the carrier, in particular the inorganic core of the carrier, comprises or consists of a material, which material has a negative coefficient of thermal expansion, in particular under the heating conditions in step b). 
     
     
         6 . The method according to  claim 1 , wherein the method comprises a further step d), which step d) is performed before step a), before step b), after step b) or after step c), optionally immediately after step b) or immediately after step c), and wherein step d) comprises the formation of a protective layer on a surface of the metal wire, in particular by means of burnishing. 
     
     
         7 . The method according to  claim 1 , wherein the heating in step b) is performed in a reducing atmosphere, in particular in a forming gas atmosphere, or in an inert gas atmosphere, in particular in an argon atmosphere, and wherein the metal wire is heated to a temperature of 300° C. to 600° C., in particular 350° C. to 550° C., further in particular 400° C. to 500° C. 
     
     
         8 . The method according to  claim 1 , wherein the metal wire wound on the carrier is heated in step b) thermically in a heating furnace, or electrically by a contact of the metal wire with electricity, in particular with alternating current or direct current. 
     
     
         9 . The method according to  claim 1 , wherein the metal coil has a diameter of less than 1.00 mm, in particular a diameter in the range of 0.01 mm to 0.75 mm, further in particular 0.10 mm to 0.50 mm, or 0.10 mm to 0.25 mm. 
     
     
         10 . The method according to  claim 1 , wherein the method is performed acid-free, in particular aqua regia-free. 
     
     
         11 . A metal coil, in particular a metal coil comprising or consisting of tungsten (W) or a tungsten alloy, obtainable by the method according to  claim 1 , wherein the surface of the metal coil in particular has no traces of etching, wherein the surface of the metal coil is further free in particular of chloride ions and/or optionally has a roughness with a Ra value of 4 um to 1 μm. 
     
     
         12 . A use of the metal coil manufactured according to  claim 1 , in a heat conduction vacuum gauge, in particular in a Pirani element, further in particular as a glow filament. 
     
     
         13 . Heat conduction vacuum gauge having the metal coil manufactured according to  claim 1 . 
     
     
         14 . A use of the metal coil manufactured according to  claim 11  in a heat conduction vacuum gauge, in particular in a Pirani element, further in particular as a glow filament. 
     
     
         15 . Heat conduction vacuum gauge having the metal coil manufactured according to  claim 11 .