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.

Claims

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 m.

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.

Description

SHORT DESCRIPTION OF THE FIGURES

[0047] Embodiments of the present invention are explained in more detail below by means of figures. These are for illustrative purposes only and are not to be interpreted restrictively. It shows

[0048] FIG. 1 Schematic step sequence of the method according to the invention as block diagram;

[0049] FIG. 2 Microscopic image of a metal wire wound on the carrier according to step a)-only a fragment is shown;

[0050] FIG. 3 Microscopic images of a metal coil which were obtained by the method of the invention.

DETAILED DESCRIPTION OF THE FIGURES

[0051] FIG. 1 shows a schematic representation of four alternative exemplary step sequences of the method of the invention, from left to right. In the first embodiment, on the far left, steps a), b) and c) are performed immediately or not immediately after the start of the method, wherein the method is deemed to have ended immediately or not immediately after step c). In the other exemplary embodiments (2nd, 3rd and 4th from left), the method further comprises step d), step d) being performed either immediately or not immediately after step c), after step a) or after step b).

[0052] FIG. 2 shows a microscopic image of a metal wire wound on the carrier in front of a rough surface as background. A small section is shown, which illustrates a twist of the metal wire around the carrier. The surfaces of the carrier and of the metal wire are smooth. In the embodiment shown, the metal wire does not contact the carrier along the entire length of the metal wire, i.e. there are section-by-section areas where the wound metal wire does not contact the carrier. However, embodiments are possible in which the metal wire contacts the carrier in its entire length, does not contact, or contacts it in sections and/or does not contact it in sections.

[0053] FIG. 3 shows microscopic images of two tungsten coils according to the invention in front of a rough surface as background. The metal coils have an even and smooth surface, with no signs of etching or acid effect. The tungsten coils shown consist of a metal wire, which in turn comprises only one metal wire, i.e. the wire is not a wire twisted from several wires, although such an embodiment also falls within the scope of the invention. The metal coil shown in the bottom figure has a pitch of 50 m and was cleaned in an ultrasonic bath with acetone after the separation from the rest of the carrier.