TRANSDUCER COMPRISING A DIAPHRAGM FOR USE WITH HYDROGEN-CONTAINING FLUID MEDIA

Abstract

A transducer for determining a pressure of a hydrogen-containing fluid medium confined in a first space includes a pressure side end configured to be disposed facing the fluid medium. The transducer includes a housing, which defines a second space, and a measuring arrangement disposed in the second space. The pressure side end includes a diaphragm configured and disposed for hermetically separating the first space from the second space. The diaphragm includes a metallic material that is made of a high-alloy martensite.

Claims

1. A transducer for determining a pressure of a hydrogen-containing fluid medium disposed in a first space, the transducer comprising: a pressure side end configured to be disposed to face the fluid medium and including a diaphragm; a housing, which defines a second space; a measuring arrangement disposed in the second space; wherein the diaphragm is configured and disposed for hermetically separating the first space from the second space; wherein the diaphragm includes a metallic material made of a high-alloy martensite.

2. The transducer according to claim 1, wherein the metallic material of the diaphragm is made of a high-alloy martensite with partially coherent precipitates.

3. The transducer of claim 1, wherein the metallic material of the diaphragm is made of a high-alloy lancet martensite with partially coherent precipitates.

4. The transducer of claim 1, wherein the metallic material is resistant to hydrogen corrosion; and wherein the metallic material is not permeable to atomic hydrogen with a leakage rate of the diaphragm for hydrogen of less than 10.sup.-6 mbar l/s, and wherein the diaphragm thickness is at most 500 .Math.m.

5. The transducer of claim 1, wherein the content of at least one of the elements chromium or molybdenum or nickel in the metallic material exceeds 5% by weight.

6. The transducer of claim 1, wherein the metallic material of the diaphragm has a chromium content of at least 10% by weight.

7. The transducer of claim 1, wherein the metallic material of the diaphragm has an average grain size of less than 20 .Math.m, which renders the metallic material suitable for the production of thin-walled diaphragms with geometric dimensions of less than 500 .Math.m.

8. The transducer of claim 1, wherein the metallic material of the diaphragm has a residual austenite content of between 0% and 30% by volume.

9. The transducer of claim 8, wherein the metallic material of the diaphragm has a residual austenite content greater than 1% by volume.

10. The transducer of claim 1, wherein the metallic material of the diaphragm has a yield strength of at least 600 MPa and at most 1500 MPa.

11. The transducer of claim 1, wherein the metallic material of the diaphragm has a chromium content of at least 10% by weight and a nickel content of at least 4% by weight; and wherein the proportion by weight of non-metals is less than 0.20% by weight; and wherein the material of the diaphragm has a coefficient of thermal expansion between 10.Math.10.sup.-6 K.sup.-1 and 11.3.Math.10.sup.-6 K.sup.-1, in the temperature range between 20° C. and 100° C.

12. The transducer of claim 1, wherein the diaphragm defines a corrugation in a surface of the metallic material configured and disposed to face the fluid medium in the first space; wherein the notch stress attributable to the corrugation is less than 1500 MPa, or wherein the corrugation is defined by transitions between two non-parallel planes, and wherein the transitions have radii of at least 100 .Math.m and/or facets of at least 30 .Math.m.

13. The transducer of claim 1, wherein the diaphragm defines a surface quality at least in a region which is configured to be disposed in contact with the fluid medium in the first space during use with a mean roughness index Ra of less than 0.8 .Math.m.

14. The transducer of claim 1, wherein the metallic material of the diaphragm has a hardness according to Rockwell C between 38 and 50 HRC.

15. The transducer of claim 1, wherein the housing and the diaphragm are connected by a material bonding connection; wherein the diaphragm has a first region which is configured to be in contact with the fluid medium during use; wherein the diaphragm has a second region which is configured so as not to be in contact with the fluid medium during use; and wherein the material bonding connection is positioned in the second region.

16. The transducer according to claim 1, wherein the metallic material of the diaphragm is made of a high-alloy martensite with partially incoherent precipitates.

17. The transducer of claim 1, wherein the metallic material of the diaphragm is made of a high-alloy lancet martensite with partially incoherent precipitates.

18. The transducer of claim 1, wherein the metallic material of the diaphragm has a residual austenite content of between 0% and 10% by volume.

19. The transducer of claim 18, wherein the metallic material of the diaphragm has a residual austenite content greater than 1% by volume.

20. The transducer of claim 1, wherein the metallic material of the diaphragm is of quenched and tempered grade 1.4418 steel having a yield strength of less than or equal to 900 MPa at room temperature; and wherein the material of the diaphragm has a coefficient of thermal expansion between 10.Math.10.sup.-6 K.sup.-1 and 11.3.Math.10.sup.-6 K.sup.-1, in the temperature range between 20° C. and 100° C.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF EXEMPLARY DRAWINGS

[0061] In the following, the invention is explained in more detail by way of example with reference to the figures in which:

[0062] FIG. 1 shows a schematic sectional view of an embodiment of a transducer with an embodiment of a diaphragm according to the invention;

[0063] FIG. 2 shows a schematic partial view of a sectional view of a transducer with a diaphragm according to FIG. 1 which is arranged in a wall; and

[0064] FIG. 3 shows a schematic representation of a diagram in which hardness is plotted against the thermal aging time of a material at a given temperature.

[0065] Throughout the figures, identical reference numerals refer to identical features.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION

[0066] FIGS. 1 and 2 each show a schematic sectional view of an embodiment of a transducer 1 comprising a diaphragm 2. The transducer 1 is suitable for determining a pressure of a fluid medium 13. The transducer 1 comprises a pressure side end 11 facing the fluid medium. The transducer 1 comprises a housing 7. A measuring arrangement 16 is arranged inside the housing 7.

[0067] The diaphragm 2 is arranged at the pressure side end 11 of the transducer 1 and hermetically separates the measuring arrangement 16 from the fluid medium 13.

[0068] In the representation of FIG. 1, which is not drawn to scale, an optional coating of the metallic material 3 is shown as a dot-dashed line.

[0069] FIG. 2 shows a further embodiment of a diaphragm. In both Figures, the thickness of the diaphragm 2 is not drawn to scale for better clarity.

[0070] The diaphragm 2 of FIGS. 1 and 2 comprises a metallic material 3 and hermetically separates a first space 14 from a second space 15. In the first space 14 is arranged a fluid medium 13 at least one physical variable of which can be determined. A physical variable is a pressure and/or a temperature, for example.

[0071] The diaphragm 2 comprises a first region 9 which is in contact with the fluid medium 13 when the diaphragm 2 is in use. The diaphragm 2 comprises a second region 10 which during use is not in contact with the fluid medium 13, as shown in FIGS. 1 and 2.

[0072] The surface 6 of the diaphragm 2 which is in direct contact with the fluid medium 13 during use advantageously has a corrugation wherein the notch stress caused by this corrugation is less than 1500 MPa. The surface of the diaphragm is shown in FIGS. 1 and 2. Transitions between two non-parallel planes have radii 18 of at least 100 .Math.m and/or facets 18 of at least 30 .Math.m.

[0073] The housing 7 and the diaphragm 2 of the transducer 1 are connected by a material bonding connection 8. The diaphragm 2 comprises a first region 9 which is in contact with the fluid medium 13 during use. The diaphragm 2 comprises a second region 10 which is not in contact with the fluid medium 13 during use. The first region 9 and second region 10 are separated from each other by a sealing element 12 when the transducer 1 is in use. In each of the embodiments shown, the material bonding connection 8 is positioned in the second region 10.

[0074] However, it is also conceivable to arrange the material bonding connection 8 in a region which is in contact with the fluid medium 13 when the diaphragm 2 is in use. In this case, the material bonding connection 8 is advantageously completely covered by the coating 4 (not shown).

[0075] FIG. 2 shows the transducer 1 for determining a pressure of a fluid medium 13 inserted into a wall 17. The wall 17 may be, for example, a wall 17 of a storage tank for a fluid medium 13, of a compressor, a heat pump, a refrigerating machine, a pipe for a fluid medium 13, of a combustion chamber of an internal combustion engine or of a gas turbine.

[0076] FIG. 3 schematically shows the relationship of the hardness of a metallic material, for example a precipitation-hardening martensite, as a function of the thermal aging time t at a specific aging temperature. The hardness increases with increasing thermal aging time up to a global maximum where maximum hardness is reached and then decreases again. The thermal aging time is a specified time that indicates the duration of the thermal treatment at a specific temperature. The maximum hardness H.sub.max of a material is reached at a thermal aging time t(maximum hardness). So-called partially coherent precipitates are present at this maximum hardness H.sub.max. Incoherent precipitates are present with longer thermal aging times. Preferentially, the precipitates form at grain boundaries within the material as described in Metallkunde, E. Hornbogen and H. Warlimont, 4th edition, Springer Verlag 2001.

[0077] It is, of course, possible to combine the embodiments of the transducer 1 or the diaphragm 2 disclosed in this document with each other. Explicitly included in this document are also embodiments which comprise a combination of the features of embodiments described herein.

TABLE-US-00001 List of reference numerals 1 transducer 2 diaphragm 3 metallic material 6 surface 7 housing 8 material bonding connection 9 first region 10 second region 11 pressure side end 12 sealing element 13 fluid medium 14 first space 15 second space 16 measuring arrangement 17 wall 18 phase / facet / curvature 21 thin-walled region