Method for determining duration of dispersion hardening

Abstract

The invention relates to the use of a measuring arrangement for determining the duration of thermal dispersion hardening of a metal sheet (1) having a front side (2), a rear side, side surfaces (3), a longitudinal edge (4) and a transverse edge (5), wherein the metal sheet (1) is connected to a current or voltage source (12) via a first electrical contact surface (11a) and a second electrical contact surface and to a voltage or current measuring device (14) via a third electrical contact surface (13a) and a fourth electrical contact surface (13b), and wherein the first electrical contact surface (11a) is located entirely between the front side (2), the rear side and the lateral side (3) intersecting surfaces (8a, 8b) with an imaginary first cylinder. The cylinder axis of the imaginary first cylinder passes through one of the corners of the front side (2), and the second electrical contact surface lies entirely in the plane consisting of the intersection surfaces (10a, 10b) of the front side (2), the rear side and the side surface (3) with the imaginary second cylinder, wherein the cylinder axis of the imaginary second cylinder passes through a corner of the front side (2) at a maximum distance from the corner through which the cylinder axis of the imaginary first cylinder passes.

Description

[0001] It is well known that the mechanical strength of metallic materials can be significantly increased by dispersion hardening, in particular for high temperature applications. Dispersion hardened metals contain non-metallic particles, such as oxide particles, dispersed in a metal matrix. When dispersion hardening is performed using oxide particles, the metal thus obtained is also referred to as "ODS" metal (ODS: "Oxide Dispersion Strengthened").

[0002] In this context, reference may be made, for example, to the following textbook references:

[0003] -G.Gottstein, “Materialwissenschaft und Werkstofftechnik–

[0004] Physikalische Grundlagen,” 4th edition, 2014, SpringerVieweg, page 276

[0005] - A.C. Reardon (ed.), “Metallurgy for the Non-Metallurgist,” 2nd ed., 2011, ASM International, pp. 69-70 (“Other Important Strengthening Mechanisms–Dispersion Strengthening”)

[0006] -WDCallister and DGRethwisch, “Materials Science and Engineering

[0007] –An Introduction,” 10th ed., 2018, Wiley, p. 571 (“Dispersion-

[0008] Strengthened Composites)

[0009] Dispersion hardened metals are particularly interesting for high temperature applications because the inorganic particles dispersed in the metal matrix are thermally stable even at high temperatures, ie, they do not dissolve in the surrounding metal matrix even at high temperatures, for example.

[0010] Dispersion hardening may be performed, for example, by powder metallurgical means by mechanical grinding (eg, grinding oxide particles into a metal matrix) and subsequent compaction by a sintering process.

[0011] Alternatively, in a melt metallurgical process, a starting alloy containing alloying elements that can be oxidized at low concentrations can be first produced. By treating the starting alloy in an oxidizing atmosphere, the oxidizable alloying elements are converted into oxide particles, and a dispersion-solidified material containing a metal matrix and oxide particles dispersed therein is obtained. This type of dispersion hardening is also called "internal oxidation".

[0012] A variety of different metals can be used for dispersion hardening.

[0013] Moulded bodies made of platinum are often used in high-temperature processes in which the material must have a high corrosion resistance. For example, components containing platinum such as stirrers or glass fiber bushings are used in the glass industry. Since platinum has a low mechanical strength at high temperatures, components made of dispersion-hardened platinum alloys are often used for applications in high-temperature processes.

[0014] The preparation, processing and physical properties of such dispersion-hardened platinum compositions are known, for example, from the documents EP 3971 311 B1, GB 1 280 815 A, GB 1 340 076 A, GB 2 082 205 A, EP 0 683240 A2, EP 0 870 844 A1, EP 0 947 595 A2, EP 1 188 844 A1, EP 1 295 953 A1, EP 1 964 938 A1, US 2 636 819 A, US 4 507 156 A, DE 23 55 122 A1, WO 81 / 01013 A1 and WO 2015 / 082630 A1.

[0015] For example, during the production of a dispersion solidified molded body, a starting alloy is first used to produce a semi-finished product (e.g., a metal sheet or tube) by melt metallurgical means (e.g., by casting into a mold), optionally formed into the desired shape by a forming process, and then heat treated in an oxidizing atmosphere so that oxide particles dispersed in the metal matrix can be formed.

[0016] The preparation of dispersion solidified alloys is a complex and time consuming process. The oxide particles in the metal matrix are formed via internal oxidation by diffusion of oxygen into the shaped body.

[0017] The alloying elements added to the alloy to form oxide particles should be oxidized as completely as possible throughout the alloy volume. In general, the larger the volume of the material to be hardened, the longer the time period required to achieve complete oxidation. This applies in particular to semi-finished products such as metal sheets or tubes which have a significant size in at least two spatial directions compared to wires.

[0018] The degree of oxidation of an alloy can be determined, for example, by determining the oxygen content using quantitative IR spectroscopy. However, this method first requires that a defined sample amount be taken from the material to be checked and that a subsequent spectroscopic analysis be performed using an NDIR sensor. Alternatively, the degree of oxidation of a sample can be checked by areal analysis in metallographic specimens, which also requires sample preparation that destroys the shaped body. Furthermore, in both cases (i.e. measuring the oxygen content by means of IR spectroscopy or areal analysis in metallographic specimens), the internal oxidation process must be interrupted and only after a measurement has been made can it be decided whether the material is completely oxidized or whether the oxidation process must be continued.

[0019] M. Bruncko et al., "In-situ monitoring of internal oxidation of dilute alloys," Corrosion Science, 49, 2007, pp. 1228-1244, describe a method in which the electrical resistance of an alloy is determined via a four-wire measurement during its dispersion hardening in order to draw conclusions about the degree of oxidation of the alloy and the required dispersion hardening duration. The measurements were carried out on wires (length: 150 mm; diameter: 0.5 mm) and thus essentially one-dimensional shaped bodies.

[0020] The object of the present invention is to provide a measuring method which, during the diffusion hardening of shaped bodies having significant dimensions in at least two spatial directions, in particular metal sheets, tubes or rods, allows reliable conclusions to be drawn about the degree of oxidation of the shaped bodies without having to interrupt the diffusion hardening and without having to destroy the shaped bodies.

[0021] According to a first embodiment of the invention, this object is achieved by a method for measuring electrical variables of a metal-containing shaped body during thermal diffusion hardening of the metal-containing shaped body, wherein

[0022] The metal-containing shaped body is a metal sheet having a front side, a rear side opposite to the front side, and a side surface connecting the front side and the rear side to each other, wherein

[0023] The front side and the rear side have in each case a length L 纵向边缘 A longitudinal edge of at least 50 mm, length L 横向边缘 is at least 50 mm of the transverse edges and the corners where the longitudinal edges meet the transverse edges,

[0024] The metal sheet has a first electrical contact surface and a second electrical contact surface connected to a current and / or voltage source, wherein

[0025] The first electrical contact surface is completely located in a plane formed by the intersection of the front side, the rear side and the side surface with an imaginary first cylinder, wherein the cylinder axis of the imaginary first cylinder is perpendicular to the front side of the metal sheet and passes through one of the corners of the front side, and the cylinder sheath of the imaginary first cylinder intersects the longitudinal edge of the front side at a distance a1 from the cylinder axis and intersects the transverse edge of the front side at a distance b1 from the cylinder axis, wherein

[0026] a1≤0.2×L 纵向边缘 And b1≤0.2×L 横向边缘

[0027] in

[0028] L 纵向边缘 is the length of the longitudinal edge and L 横向边缘 is the length of the transverse edge with which the longitudinal edge meets at the corner through which the cylinder axis of the imaginary first cylinder passes,

[0029] The second electrical contact surface is completely located in a plane formed by the intersection of the front side, the rear side and the side surface with an imaginary second cylinder, wherein the cylinder axis of the imaginary second cylinder is perpendicular to the front side of the metal sheet and passes through the corner of the front side at the maximum distance from the corner through which the cylinder axis of the imaginary first cylinder passes, and the cylindrical sheath of the imaginary second cylinder intersects the longitudinal edge of the front side at a distance a2 from the cylinder axis and intersects the transverse edge of the front side at a distance b2 from the cylinder axis, wherein

[0030] a2≤0.2×L 纵向边缘 And b2≤0.2×L 横向边缘

[0031] in

[0032] L 纵向边缘 is the length of the longitudinal edge and L 横向边缘 is the length of the transverse edge with which the longitudinal edge meets at the corner through which the cylinder axis of the imaginary second cylinder passes,

[0033] The metal sheet has a third electrical contact surface and a fourth electrical contact surface, which are connected to the voltage measuring device when the first electrical contact surface and the second electrical contact surface are connected to the current source, or connected to the current measuring device when the first electrical contact surface and the second electrical contact surface are connected to the voltage source,

[0034] heat treating a metal sheet connected via its first and second electrical contact surfaces to a current or voltage source and via its third and fourth electrical contact surfaces to a voltage or current measuring device, so that oxide particles are formed in the metal sheet, and

[0035] During the heat treatment, the electrical resistance of the metal sheet or an electrical variable proportional to the electrical resistance is determined.

[0036] The method according to the invention is a four-wire measurement. Using this method, which is known in principle to a person skilled in the art, the (ohmic) resistance of a test body or an electrical measured variable proportional thereto can be determined. However, as described in detail below, within the scope of the invention, it is necessary to attach a connection to a current source (or alternatively a voltage source) to the surface of the metal sheet.

[0037] Like any metal sheet, the metal sheet to which the measuring method according to the invention is applied has a front side, a rear side opposite the front side and side faces connecting the front side and the rear side to one another. The front side and the rear side each have a longitudinal edge, a transverse edge and a corner at which the longitudinal edge meets the transverse edge. The longitudinal edge and the transverse edge have a length of at least 50 mm.

[0038] Such an exemplary metal sheet which can be subjected to the measurement method according to the invention is Figure 1 Shown in.

[0039] Figure 1 The metal sheet 1 shown has a front side 2. The rear side of the metal sheet is located opposite the front side 2. The front side 2 and the rear side of the metal sheet are connected to each other via side faces 3 and have in each case a longitudinal edge 4, a transverse edge 5 and a corner 6 at which the longitudinal edge 4 and the transverse edge 5 meet.

[0040] In an exemplary embodiment, the longitudinal edge has a length L of 50 mm to 2000 mm. 纵向边缘 and / or the transverse edge has a length L of 50 mm to 2000 mm 横向边缘 The front and rear sides of the metal sheet may, for example, have a substantially square shape (ie, L 纵向边缘 and L 横向边缘 are the same or at least have very similar values) or alternatively have an elongated shape (ie, L 纵向边缘 and L 横向边缘 The longitudinal edge and the transverse edge of the front side or rear side are, for example, substantially perpendicular to each other (for example at an angle of 90°+ / -10°). The metal sheet has, for example, a thickness of at most 15 mm.

[0041] The metal sheet is therefore a shaped body having a significant size in at least two spatial directions.Therefore, in principle there are many possibilities for contacting the metal sheet with a current source (or alternatively a voltage source) in the context of a four-wire measurement for determining the resistance of the metal sheet.

[0042] In the method of the invention, a four-wire measurement is performed during the dispersion hardening of a metal sheet. In the context of the invention, it has been recognized that more reliable conclusions about the degree of oxidation and thus the progress of the dispersion hardening can be drawn from the measurement of the resistance of the metal sheet (or an electrical variable proportional to the resistance, such as a voltage or a current) using the four-wire measurement if the contacting of the metal sheet with a current source (or alternatively a voltage source) takes place in such a way that a first electrical contact surface is positioned relatively close to a first corner of the metal sheet, while a second electrical contact surface is positioned as close as possible to a corner at a maximum distance relative to the first corner. In the case of a rectangular metal sheet, these are diagonally opposite corners.

[0043] The first electrical contact surface is completely located within the plane formed by the intersection of the front side, the rear side and the side of the metal sheet and the imaginary first cylinder. The intersection of the front side, the rear side and the side of the metal sheet and the imaginary first cylinder is the plane where the front side, the rear side and the side are located within the imaginary first cylinder. Like any cylinder, the imaginary first cylinder has a cylinder axis and a cylinder sheath. The cylinder axis of the imaginary first cylinder is perpendicular to the front side of the metal sheet and passes through one of the corners where one of the longitudinal edges of the front side meets one of the transverse edges. The cylindrical sheath of the imaginary first cylinder intersects with the longitudinal edge of the front side at a distance a1 from the cylinder axis and intersects with the transverse edge of the front side at a distance b1 from the cylinder axis, where

[0044] a1≤0.2×L 纵向边缘 And b1≤0.2×L 横向边缘

[0045] in

[0046] L 纵向边缘 is the length of the longitudinal edge and L 横向边缘 is the length of the transverse edge with which the longitudinal edge meets at the corner through which the cylinder axis of the imaginary first cylinder passes.

[0047] The imaginary first cylinder may be a circular cylinder or an elliptical cylinder. The distance of a point from the axis of the cylinder is the length of the shortest connecting line between the point and the axis of the cylinder.

[0048] In an exemplary embodiment, a1 and L 纵向边缘 and b1 and L 横向边缘 The following relations are satisfied:

[0049] a1≤0.14×L 纵向边缘 And b1≤0.14×L 横向边缘

[0050] The second electrical contact surface is completely located within the plane formed by the intersection of the front side, the rear side and the side of the metal sheet with the imaginary second cylinder. The intersection of the front side, the rear side and the side of the metal sheet with the imaginary second cylinder is the plane where the front side, the rear side and the side are located within the imaginary second cylinder. The cylinder axis of the imaginary second cylinder is perpendicular to the front side of the metal sheet and passes through the corner of the front side at the maximum distance from the corner through which the cylinder axis of the imaginary first cylinder passes. The cylindrical sheath of the imaginary second cylinder intersects with the longitudinal edge of the front side at a distance a2 from the cylinder axis and intersects with the transverse edge of the front side at a distance b2 from the cylinder axis, wherein

[0051] a2≤0.2×L 纵向边缘 And b2≤0.2×L 横向边缘

[0052] in

[0053] L 纵向边缘 is the length of the longitudinal edge and L 横向边缘 is the length of the transverse edge with which the longitudinal edge meets at the corner through which the cylinder axis of the imaginary second cylinder passes.

[0054] The imaginary second cylinder may be a circular cylinder or an elliptical cylinder. The distance of a point from the axis of the cylinder is the length of the shortest connecting line between the point and the axis of the cylinder.

[0055] In an exemplary embodiment, a2 and L 纵向边缘 and b2 and L 横向边缘 The following relations are satisfied:

[0056] a2≤0.14×L 纵向边缘 And b2≤0.14×L 横向边缘

[0057] exist Figure 2 (L 纵向边缘 =L 横向边缘 )and Figure 3 (L 纵向边缘 >>L 横向边缘 ) shows an imaginary first cylinder and an imaginary second cylinder as well as the intersection surfaces of the front and side surfaces of the metal sheet with these imaginary cylinders.

[0058] Figure 2is a plan view of the front side 2 of the metal sheet 1, wherein the longitudinal edge 4 and the transverse edge 5 of the front side 2 have the same length and meet at a corner 6. The cylinder axis 7a of the imaginary first cylinder 7 passes through one of the corners 6 and is perpendicular to the front side 2 of the metal sheet 1. The cylinder jacket 7b of the imaginary first cylinder intersects the longitudinal edge 4 at a distance a1 from the cylinder axis 7a and intersects the transverse edge 5 at a distance b1 from the cylinder axis 7a. Since the front side 2 has a square shape (i.e. L 纵向边缘 =L 横向边缘 ), so the following applies: a1 = b1 = 0.2 × L 纵向边缘 =0.2×L 横向边缘 The front side 2 intersects with the imaginary first cylinder 7 to produce an intersection surface 8a ( Figure 2 In addition to the intersection surface 8a, there are other intersection surfaces ( Figure 2 ). The first electrical contact surface of the metal sheet 1, via which it is connected to a current or voltage source of the measuring arrangement, is located in a plane formed by (i.e., consisting of) the intersection surface 8a of the front side 2 with the imaginary first cylinder 7, the intersection surface of the rear side with the imaginary first cylinder and the intersection surface of the side surface with the imaginary first cylinder. The cylinder axis 9a of the imaginary second cylinder 9 is perpendicular to the front side 2 of the metal sheet 1 and passes through the corner 6 of the front side 2 at the maximum distance from the corner 6 passed by the cylinder axis 7a of the imaginary first cylinder 7. The cylinder jacket 9b of the imaginary second cylinder intersects the longitudinal edge 4 at a distance a2 from the cylinder axis 9a and intersects the longitudinal edge 5 at a distance b2 from the cylinder axis 9a. The following also applies to the imaginary second cylinder: a2=b2=0.2×L 纵向边缘 =0.2×L 横向边缘 The intersection surface 10a of the front side 2 and the imaginary second cylinder is indicated by hatching. In addition to this intersection surface, there are other intersection surfaces ( Figure 2 (not shown in FIG. 1 ). A second electrical contact surface is selected within these intersecting surfaces, via which the metal sheet is connected to a current or voltage source of the measuring arrangement.

[0059] Figure 3 is a plan view of the front side 2 of the metal sheet 1, wherein the longitudinal edge 4 and the transverse edge 5 of the front side 2 have significantly different lengths and meet at the corner 6. The cylindrical jacket 7b of the imaginary first cylinder 7 intersects the longitudinal edge 4 at a distance a1 from the cylinder axis 7a and intersects the longitudinal edge 5 at a distance b1 from the cylinder axis 7a, where a1=0.2×L 纵向边缘 And b1=0.2×L 横向边缘The front side 2 of the metal sheet 1 intersects the imaginary first cylinder 7 at the intersection plane 8a. The cylinder jacket 9b of the imaginary second cylinder 9 intersects the longitudinal edge 4 at a distance a2 from the cylinder axis 9a and intersects the longitudinal edge 5 at a distance b2 from the cylinder axis 9a, where a2 = 0.2 × L 纵向边缘 And b2 = 0.2 × L 横向边缘 The front side 2 of the metal sheet 1 intersects with the imaginary second cylinder at an intersection surface 10a.

[0060] As already described above, the electrical contact surfaces of the metal sheet with which it is connected to the current or voltage source are to be selected so that they lie in each case within the plane consisting of the intersection of the front, rear and side faces of the metal sheet with the imaginary first cylinder or the imaginary second cylinder.

[0061] exist Figure 4 In the exemplary embodiment shown, the front side 2 of the metal sheet 1 intersects with the imaginary first cylinder ( Figure 4 ) intersects with the imaginary second cylinder ( Figure 4 The side surface 3 intersects the first imaginary cylinder and the second imaginary cylinder at intersection surfaces 8b and 10b, etc. The first electrical contact surface 11a for connecting to the current source 12 is located on the intersection surface 8b, while the second electrical contact surface ( Figure 4 ) is located at the intersection of the opposite side surface and the imaginary second cylinder.

[0062] exist Figure 5 In the figure, the intersection surfaces 8a, 8b, 10a and 10b of the front side 2 and the side 3 correspond to Figure 4 The imaginary cylinder with the intersection shown. Figure 4 , the first electrical contact surface 11a is located in the intersection surface 8b for connecting to the current source 12. Figure 5 In the exemplary embodiment shown, the second electrical contact surface 11 b is located within the intersection surface 10 a .

[0063] A connection is established between the metal sheet and the voltage or current measuring device via the third electrical contact surface and the fourth electrical contact surface of the metal sheet. When the first electrical contact surface and the second electrical contact surface of the metal sheet are connected to the current source, the third electrical contact surface and the fourth electrical contact surface of the metal sheet are connected to the voltage measuring device. When the first electrical contact surface and the second electrical contact surface of the metal sheet are connected to the voltage source, the third electrical contact surface and the fourth electrical contact surface of the metal sheet are connected to the current measuring device.

[0064] Contact elements known to those skilled in the art can be used to contact the electrical contact surface of the metal sheet with a current or voltage source and a voltage or current measuring device. For example, the electrical contact surface is connected to the current or voltage source and to the voltage or current measuring device via terminals (e.g., Kelvin terminals or coil terminals) or contact pins.

[0065] Thermal diffusion hardening is usually carried out at a relatively high temperature and sometimes for a relatively long period of time. In order to achieve reliable electrical contact between the metal sheet and the current or voltage source in a simple and effective manner under these conditions, the first electrical contact surface or the second electrical contact surface can be preferably brought into contact with the wire of the current or voltage source under the weight of the metal sheet, for example, by placing the metal sheet on the wire (for example, via its front side or one of its side surfaces), and the third electrical contact surface and the fourth electrical contact surface can be brought into contact with the wire of the voltage or current measuring device. The metal sheet is placed on the wire, for example, with one of its side surfaces. In this preferred embodiment, the number of required contact terminals can be significantly reduced.

[0066] A person skilled in the art will be able to determine the appropriate size of the electrical contact surface on the metal sheet based on his professional knowledge or by routine testing. For example, the electrical contact surface of the metal sheet each has at least 1 mm 2 area.

[0067] In the method according to the invention, it is essential that the first and second electrical contact surfaces of the metal sheet (i.e. the contact surfaces of the metal sheet via which the metal sheet is connected to a current or voltage source) are selected so that they are in each case located within a plane consisting of the intersection of the front side, the rear side and the side surfaces with an imaginary cylinder. This ensures that the first electrical contact surface is positioned relatively close to one of the corners of the metal sheet, while the second electrical contact surface is positioned as close as possible to the opposite corner.

[0068] The positions of the third and fourth electrical contact surfaces (i.e., the contact surfaces of the metal sheet via which the metal sheet is connected to the voltage or current measuring device) on the metal sheet can be freely selected. A person skilled in the art can determine suitable positions based on his general expertise and by routine tests.

[0069] For example, the third electrical contact surface and the fourth electrical contact surface

[0070] is at a greater distance from the corner through which the cylinder axis of the imaginary first cylinder passes than the first electrical contact surface, and

[0071] Compared with the second electrical contact surface, the second electrical contact surface is at a greater distance from the corner through which the cylinder axis of the imaginary second cylinder passes. The distance is the shortest straight line connecting the contact surface and the corner.

[0072] For example, the third electrical contact surface and the fourth electrical contact surface are located outside the intersection surface of the front side, the rear side and the side surface with the imaginary first cylinder, and outside the intersection surface of the front side, the rear side and the side surface with the imaginary second cylinder.

[0073] For example, the distance between the third electrical contact surface and the fourth electrical contact surface is smaller than the distance between the first electrical contact surface and the second electrical contact surface. The distance is the shortest straight line connecting the two corresponding contact surfaces.

[0074] For example, the first electrical contact surface, the third electrical contact surface and the fourth electrical contact surface are on the same side of the metal sheet, and the second electrical contact surface is on another side of the metal sheet, preferably the opposite side. Figure 6 Regarding the positions of the intersections 8a, 8b, 10a and 10b of the front side 2 and the side surface 3 with the imaginary cylinder and the first electrical contact surface 11a and the second electrical contact surface (for connecting to the current source 12), Figure 6 Corresponds to Figure 4 The metal sheet 1 is connected to a voltage measuring device 14 via electrical contact surfaces 13a and 13b.

[0075] A metal sheet connected via first and second electrical contact surfaces to a current or voltage source and via third and fourth electrical contact surfaces to a voltage or current measuring device is heat treated so that oxide particles are formed in the metal sheet.

[0076] Suitable metals in the form of alloys which form oxide particles during a heat treatment in an oxidizing atmosphere (so that a metal matrix and oxide particles dispersed therein are obtained) and which are suitable for dispersion hardening are known to the person skilled in the art.

[0077] For example, the metal from which the metal sheet is made is a precious metal alloy containing one or more non-precious metals. For example, the precious metal alloy contains non-precious metals in a concentration of not more than 1% by weight, and the remainder is one or more precious metals and inevitable impurities. The non-precious metals are, for example, selected from zirconium, cerium, scandium and yttrium, and the precious metals are, for example, selected from ruthenium, rhodium, gold, palladium, platinum, iridium and osmium. The precious metal alloy contains, for example, the first precious metal as the main element and other precious metals (if any), with a total concentration of not more than 29.95% by weight, provided that the first precious metal is different from the other precious metals.

[0078] By "major element" it is meant that the element is present in a higher concentration than any of the other elements.

[0079] Suitable temperatures for dispersion hardening are known to those skilled in the art or can optionally be determined by routine testing. For example, the heat treatment of the metal sheet is carried out at a temperature of at least 750°C, for example in the range of 750°C to 1400°C or 800°C to 1200°C.

[0080] Dispersion hardening is carried out in an oxidizing atmosphere. Suitable oxidizing atmospheres for dispersion hardening of alloys are known to those skilled in the art. For example, an oxidizing atmosphere is an atmosphere containing oxygen. For example, the oxygen content of the oxidizing atmosphere is at least 5 volume %, more preferably at least 10 volume %. In an exemplary embodiment, air is used as the oxidizing atmosphere.

[0081] During the heat treatment, the electrical resistance of the metal sheet or an electrical variable proportional to the electrical resistance is determined.

[0082] The resistance (also called ohmic resistance) is determined using the known relationship R = U / I, where

[0083] I is the current source (connected to the first electrical contact surface and the second electrical contact surface of the metal sheet)

[0084] the current intensity of the supplied current, and U is the voltage measured with a voltage measuring device (connected to the third and fourth electrical contact surfaces of the metal sheet), or

[0085] U is the voltage applied by the voltage source (connected to the first and second electrical contacts of the metal sheet), and I is the current intensity measured with the current measuring device (connected to the third and fourth electrical contacts of the metal sheet).

[0086] The measured resistance is affected by the degree of oxidation of the metal sheet.For example, the heat treatment is ended when the resistance of the metal sheet has a constant value (eg not varying by more than + / - 1%) for a defined duration (eg at least 1 hour or at least 4 hours).

[0087] Instead of the electrical resistance of the metal sheet, a variable proportional to the electrical resistance, such as voltage or current intensity, can be used to determine the required duration of the dispersion hardening. For example, it may be sufficient to measure the voltage or current intensity at the third and fourth contact surfaces and to terminate the heat treatment when the voltage or current intensity measured at these contact surfaces has a constant value (e.g., a variation of no more than + / - 1%) for a defined duration (e.g., at least 1 hour or at least 4 hours).

[0088] The resistance or an electrical variable proportional thereto can be determined, for example, continuously or at defined time intervals.

[0089] According to another embodiment of the invention, the object is achieved by a method for measuring electrical variables of a metal-containing shaped body during thermal diffusion hardening of the metal-containing shaped body, wherein

[0090] The metal-containing shaped body is a metal tube or a metal rod, wherein the metal tube or the metal rod

[0091] Having a length L of at least 50 mm 成型体 and a diameter D in the range of 10 mm to 300 mm 成型体 ,

[0092] end portions, having a first end surface at one of the ends and a second end surface at the opposite end thereof, the first end surface and the second end surface being connected to each other by a lateral surface, the first end surface and the second end surface being each defined by an outer boundary line,

[0093] The metal tube or the metal rod has a first electrical contact surface and a second electrical contact surface, and these electrical contact surfaces are connected to a current or voltage source, wherein

[0094] The first electrical contact surface is completely located in a plane formed by the intersection of the lateral surface and the first end surface with an imaginary first ellipsoid, wherein the imaginary first ellipsoid has a center point and semi-axes a1, b1 and c1, wherein the center point is located on the outer boundary line of the first end surface of the metal tube or metal rod, and the semi-axis a1 is parallel to the longitudinal axis of the metal tube or metal rod and has a length L a1 ≤0.2×L 成型体 , and the semi-axes b1 and c1 have length L b1 =L c1 ≤0.4×D 成型 体 ,

[0095] The second electrical contact surface is completely located in the plane formed by the intersection of the lateral surface and the second end surface and the imaginary second ellipsoid, wherein the imaginary second ellipsoid has a center point and semi-axes a2, b2 and c2, the center point of the imaginary second ellipsoid is the point on the outer boundary line of the second end surface of the metal tube or metal rod that is farthest from the center point of the imaginary first ellipsoid, and the semi-axis a2 is parallel to the longitudinal axis of the metal tube or metal rod and has a length L a2 ≤0.2×L 成型体 , and the semi-axes b2 and c2 have length L b2 =L c2 ≤0.4×D 成型体 ,

[0096] The metal tube or the metal rod has a third electrical contact surface and a fourth electrical contact surface, and when the first electrical contact surface and the second electrical contact surface are connected to the current source, these electrical contact surfaces are connected to the voltage measuring device, or when the first electrical contact surface and the second electrical contact surface are connected to the voltage source, these electrical contact surfaces are connected to the current measuring device,

[0097] A metal tube or a metal rod connected to a current or voltage source via its first and second electrical contact surfaces and to a voltage or current measuring device via its third and fourth electrical contact surfaces is subjected to a heat treatment so that oxide particles are formed in the metal tube or the metal rod, and

[0098] During the heat treatment of a metal tube or bar, its electrical resistance or an electrical variable proportional to the resistance is determined.

[0099] Within the scope of the present invention, the term "ellipsoid" also includes a sphere as a limiting case.

[0100] The semi-axes a1, b1 and c1 of the imaginary first ellipsoid are generally perpendicular to each other. The semi-axes a2, b2 and c2 of the imaginary second ellipsoid are also generally perpendicular to each other.

[0101] If the shaped body is a metal tube, the diameter D 成型体 is the outer diameter of the metal tube. In the case of a metal tube, both the first end face and the second end face also have an inner boundary line close to the outer boundary line.

[0102] An exemplary metal pipe to which the measuring method according to the invention can be applied is Figure 7 Shown in.

[0103] Figure 7 The metal tube 15 shown terminates at one of its ends with a first end face 16. The first end face 16 is bounded by an outer boundary line 18 and an inner boundary line 19. The outer boundary line 18 corresponds to the outer periphery of the tube 15, while the inner boundary line 19 corresponds to the inner periphery of the tube 15. At the opposite end, the tube 15 terminates with a second end face ( Figure 7 The first end face 16 and the opposite second end face are connected to each other through a lateral face 17.

[0104] The metal tube or metal rod has a length L of, for example, 50 mm to 3,000 mm. 成型体 .

[0105] The metal tube or metal rod has an L of, for example, at least 2, more preferably at least 5. 成型体 With D 成型体 ratio.

[0106] The tube is, for example, a circular tube or a polygonal tube (eg, a rectangular tube).

[0107] The selection of a suitable wall thickness for the tube depends, for example, on the intended use of the tube. For example, the tube has a ratio of wall thickness to outer diameter of at least 0.01. The tube has, for example, a wall thickness of no more than 15 mm.

[0108] Figure 8 and Fig. 9 , imaginary ellipsoids and intersection surfaces of the end faces and lateral faces of the metal tube with these imaginary ellipsoids are shown.

[0109] Figure 8 The metal tube 15 is shown in the direction of its longitudinal axis. The center point 20a of the imaginary first ellipsoid 20 is located on the outer boundary line 18 of the first end surface 16. The figure shows the semi-axes a1 and b1 of the ellipsoid 20. The first end surface 16 intersects with the imaginary first ellipsoid 20 at the intersection surface 21a. In addition to the intersection surface 21a, there is also an intersection surface ( Figure 8 not shown).

[0110] exist Fig. 9 In the embodiment, the first end face 16 and the lateral face 17 of the metal tube 15 intersect with the imaginary first ellipsoid (not shown) at the intersection faces 21a and 21b. The lateral face 17 intersects with the imaginary second ellipsoid (not shown) at the intersection face 23b. The intersection face of the second end face and the imaginary second ellipsoid is Fig. 9 The first electrical contact surface 22a and the second electrical contact surface 22b are located in the intersection surfaces 21b and 23b and connect the metal tube 15 to the current source 12.

[0111] In an exemplary embodiment, the following relationships apply to the lengths of the semi-axes a1, b1, and c1 of the imaginary first ellipsoid and the lengths of the semi-axes a2, b2, and c2 of the imaginary second ellipsoid:

[0112] L a1 ≤0.14×L 成型体 ; L b1 =L c1 ≤0.25×D 成型体 ;

[0113] L a2 ≤0.14×L 成型体 ; L b2 =L c2 ≤0.25×D 成型体 .

[0114] As in the first embodiment according to the invention (i.e. the metal sheet as a shaped body), in the second embodiment of the method according to the invention, the connection to the voltage or current measuring device is also established via the third electrical contact surface and the fourth electrical contact surface of the metal shaped body. When the first electrical contact surface and the second electrical contact surface of the metal rod or the metal tube are connected to the current source, the third electrical contact surface and the fourth electrical contact surface of the metal rod or the metal tube are connected to the voltage measuring device. When the first electrical contact surface and the second electrical contact surface of the metal rod or the metal tube are connected to the voltage source, the third electrical contact surface and the fourth electrical contact surface of the metal rod or the metal tube are connected to the current measuring device.

[0115] Contact elements known to those skilled in the art can be used to contact the electrical contact surface of the metal rod or metal tube with a current or voltage source and a voltage or current measuring device. For example, the electrical contact surface is connected to the current or voltage source and to the voltage or current measuring device via terminals (e.g., Kelvin terminals or coil terminals).

[0116] In a preferred embodiment, the first electrical contact surface is brought into contact with the wires of the current or voltage source and the third and fourth electrical contact surfaces are brought into contact with the wires of the voltage or current measuring device under the weight of the metal rod or metal tube, for example by placing the metal rod or metal tube (for example with its lateral surface or one of its end surfaces) on the wires. In this preferred embodiment, the number of required contact terminals can be significantly reduced.

[0117] A person skilled in the art will be able to determine the appropriate size of the electrical contact surface on the metal rod or metal tube based on his professional knowledge and through routine testing. For example, the electrical contact surface of the metal rod or metal tube each has a diameter of at least 1 mm. 2 area.

[0118] In the method according to the invention, it is essential that the first and second electrical contact surfaces of the metal rod or metal tube (i.e. the contact surfaces via which the metal rod or metal tube is connected to the current or voltage source) are selected so that they are in each case located within the plane consisting of the intersection of the end surface and the lateral surface with the imaginary first ellipsoid or the imaginary second ellipsoid. This ensures that the first and second electrical contact surfaces are at as great a distance from each other as possible.

[0119] The intersection of the lateral surface and the first end surface with the imaginary first ellipsoid is the surface where the lateral surface and the first end surface are located inside the imaginary first ellipsoid. The intersection of the lateral surface and the second end surface with the imaginary second ellipsoid is the surface where the lateral surface and the second end surface are located inside the imaginary second ellipsoid.

[0120] The positions of the third and fourth electrical contact surfaces (i.e., the contact surfaces of the metal tube or metal rod via which the connection to the voltage or current measuring device is formed) on the metal tube or metal rod can be freely selected. A person skilled in the art can determine suitable positions based on his general expertise and by routine tests.

[0121] For example, the third electrical contact surface and the fourth electrical contact surface

[0122] is at a greater distance from the center point of the imaginary first ellipsoid than the first electrical contact surface, and

[0123] The second electrical contact surface is located at a greater distance from the center point of the imaginary second ellipsoid.

[0124] This distance is the shortest straight line connecting the contact surface and the center point of the ellipsoid.

[0125] For example, the third electrical contact surface and the fourth electrical contact surface are located outside the intersection surface of the end surface and the lateral surface with the imaginary ellipsoid.

[0126] For example, the distance between the third electrical contact surface and the fourth electrical contact surface is smaller than the distance between the first electrical contact surface and the second electrical contact surface. The distance is the shortest straight line connecting the two corresponding electrical contact surfaces.

[0127] exist Fig.10 In FIG. 1 , the intersection surfaces 21a, 21b and 23b and the electrical contact surfaces 22a and 22b (via which the metal tube 15 is connected to the current source 12) correspond to Fig. 9 The embodiment shown. The third electrical contact surface 24a and the fourth electrical contact surface 24b of the metal tube 15, via which it is connected to the voltage measuring device 14, are arranged substantially linearly relative to the first electrical contact surface 22a. This can be achieved, for example, by placing the metal tube 15 with its lateral surface 17 on the wires connected to the current source and the voltage measuring device.

[0128] As in the first embodiment according to the invention, in the second embodiment of the method according to the invention, the metal molded body connected via its first and second electrical contact surfaces to a current or voltage source and via its third and fourth electrical contact surfaces to a voltage or current measuring device is also subjected to a heat treatment, so that oxide particles are formed in the metal tube, and during the heat treatment of the metal molded body, its resistance or an electrical variable proportional to the resistance is determined. For further details on these method steps and suitable metal alloys, reference is therefore made to the above description of the first embodiment according to the invention.

[0129] Furthermore, the invention relates to a measuring arrangement comprising:

[0130] Current or voltage source,

[0131] Voltage or current measuring devices,

[0132] A metal-containing shaped body, wherein the metal-containing shaped body is a metal sheet,

[0133] The metal sheet has a front side, a rear side opposite to the front side, and a side surface connecting the front side and the rear side to each other, wherein

[0134] The front side and the rear side have in each case a length L 纵向边缘 A longitudinal edge of at least 50 mm, length L 横向边缘 is at least 50 mm of the transverse edges and the corners where the longitudinal edges meet the transverse edges,

[0135] The metal sheet has a first electrical contact surface and a second electrical contact surface connected to a current or voltage source, wherein

[0136] The first electrical contact surface is completely located in a plane formed by the intersection of the front side, the rear side and the side surface with an imaginary first cylinder, wherein the cylinder axis of the imaginary first cylinder is perpendicular to the front side of the metal sheet and passes through one of the corners of the front side, and the cylinder sheath of the imaginary first cylinder intersects the longitudinal edge of the front side at a distance a1 from the cylinder axis and intersects the transverse edge of the front side at a distance b1 from the cylinder axis, wherein

[0137] a1≤0.2×L 纵向边缘 And b1≤0.2×L 横向边缘

[0138] in

[0139] L 纵向边缘 is the length of the longitudinal edge and L 横向边缘 is the length of the transverse edge with which the longitudinal edge meets at the corner through which the cylinder axis of the imaginary first cylinder passes,

[0140] The second electrical contact surface is completely located in a plane formed by the intersection of the front side, the rear side and the side surface with an imaginary second cylinder, wherein the cylinder axis of the imaginary second cylinder is perpendicular to the front side and passes through the corner of the front side at the maximum distance from the corner through which the cylinder axis of the imaginary first cylinder passes, and the cylinder sheath of the imaginary second cylinder intersects the longitudinal edge of the front side at a distance a2 from the cylinder axis and intersects the transverse edge of the front side at a distance b2 from the cylinder axis, wherein

[0141] a2≤0.2×L 纵向边缘 And b2≤0.2×L 横向边缘

[0142] in

[0143] L 纵向边缘is the length of the longitudinal edge and L 横向边缘 is the length of the transverse edge with which the longitudinal edge meets at the corner through which the cylinder axis of the imaginary second cylinder passes,

[0144] The metal sheet has a third electrical contact surface and a fourth electrical contact surface, and these electrical contact surfaces are connected to the voltage measuring device when the first electrical contact surface and the second electrical contact surface are connected to the current source, or when the first electrical contact surface and the second electrical contact surface are connected to the voltage source, these electrical contact surfaces are connected to the current measuring device.

[0145] The above method according to the first embodiment according to the invention can be carried out with this measuring arrangement.Therefore, for further properties of the metal sheet and the electrical contact surface of the metal sheet, reference is made to the above description of the first embodiment according to the invention.

[0146] Furthermore, the invention relates to a measuring arrangement comprising:

[0147] Current or voltage source,

[0148] Voltage or current measuring devices,

[0149] A shaped body containing metal, wherein the shaped body containing metal is a metal tube or a metal rod, wherein the metal tube or the metal rod

[0150] Having a length L of at least 50 mm 成型体 and a diameter D in the range of 10 mm to 300 mm 成型体 ,

[0151] end portions, having a first end face at one of the ends and a second end face at the opposite end thereof, the end faces being connected to one another by lateral faces and being each delimited by an outer boundary line,

[0152] The metal tube or the metal rod has a first electrical contact surface and a second electrical contact surface, which are connected to a current or voltage source, wherein

[0153] The first electrical contact surface is completely located in a plane formed by the intersection of the lateral surface and the first end surface with an imaginary first ellipsoid, wherein the imaginary first ellipsoid has a center point and semi-axes a1, b1 and c1, wherein the center point is located on the outer boundary line of the first end surface of the metal tube or metal rod, and the semi-axis a1 is parallel to the longitudinal axis of the metal tube or metal rod and has a length L a1 ≤0.2×L 成型体 , and the semi-axes b1 and c1 have length L b1 =L c1 ≤0.4×D 成型 体 ,

[0154] The second electrical contact surface is completely located in the plane formed by the intersection of the lateral surface and the second end surface and the imaginary second ellipsoid, wherein the imaginary second ellipsoid has a center point and semi-axes a2, b2 and c2, the center point of the imaginary second ellipsoid is the point on the outer boundary line of the second end surface of the metal tube or metal rod that is farthest from the center point of the imaginary first ellipsoid, and the semi-axis a2 is parallel to the longitudinal axis of the metal tube or metal rod and has a length L a2 ≤0.2×L 成型体 , and the semi-axes b2 and c2 have length L b2 =L c2 ≤0.4×D 成型体 ,

[0155] The metal tube or the metal rod has a third electrical contact surface and a fourth electrical contact surface, and when the first electrical contact surface and the second electrical contact surface are connected to the current source, these electrical contact surfaces are connected to the voltage measuring device, or when the first electrical contact surface and the second electrical contact surface are connected to the voltage source, these electrical contact surfaces are connected to the current measuring device.

[0156] The above method according to the second embodiment according to the invention can be carried out with this measuring arrangement.Therefore, for further properties of the metal tube or metal rod and the electrical contact surface of the metal tube or metal rod, reference is made to the above description according to the second embodiment of the invention.

[0157] The invention also relates to the use of the above-described measuring arrangement for determining the duration of thermal diffusion hardening of a metal sheet, metal rod or metal tube.

[0158] The present invention is explained in more detail with reference to the following examples. Example

[0159] Two starting metal sheets are produced with matched size and matched chemical composition.

[0160] L 纵向边缘 (i.e., the length of the longitudinal edge of the metal sheet): 150 mm

[0161] L 横向边缘 (i.e., the length of the lateral edge of the metal sheet): 120 mm

[0162] The two starting sheets were produced using a platinum alloy as described in Example 3 of EP 3971311 B1.

[0163] Each of the starting sheets with matching chemical composition was then subjected to thermal dispersion hardening under identical conditions in an oxidizing atmosphere. The dispersion hardening was carried out in each case at a temperature of 1,000° C. in an air atmosphere.

[0164] The aim of dispersion hardening is to oxidize the non-noble metals in the alloy as completely as possible (forming oxide particles dispersed in a noble metal matrix).

[0165] For both metal sheets, the electrical resistance was determined over time during dispersion hardening using a four-wire measurement. However, as described in detail below, a different measurement arrangement has been used for the four-wire measurement.

[0166] The measuring arrangements of the comparative embodiment and the embodiment according to the invention differ in the relative arrangement of the first electrical contact surface and the second electrical contact surface with respect to one another.

[0167] In the measurement arrangement of the comparative embodiment, the first electrical contact surface is on one of the side surfaces close to a first corner of the metal sheet, and the second electrical contact surface is on the same side surface close to a corner adjacent to the first corner.

[0168] Distance from the first electrical contact surface to the first corner: 15mm

[0169] Distance from the second electrical contact surface to the corner adjacent to the first corner: 15 mm

[0170] In a measuring arrangement according to an embodiment of the invention, the position of the second electrical contact surface is changed so that it is located on an opposite side near a corner opposite to the first corner.

[0171] Distance from the second electrical contact surface to the opposite corner: 15mm

[0172] Figure 6 is a schematic diagram of a measurement arrangement used in an embodiment according to the invention.

[0173] Fig.11 is a schematic diagram of a measurement arrangement of a comparative example.

[0174] according to Figure 6 , Fig.11 A metal sheet 1 is shown, which has a front side 2, a side 3, a longitudinal edge 4, a transverse edge 5 and intersection surfaces 8a, 8b, 10a, 10b of the front side 2 and the side 3 with an imaginary cylinder. A voltage source 14 is connected to the metal sheet 1 via a third electrical contact surface 13a and a fourth electrical contact surface 13b. A current source 12 is connected to the metal sheet via a first electrical contact surface 11a and a second electrical contact surface 11b. In contrast to the embodiment according to the invention, in the comparative embodiment, the second electrical contact surface 11b is not located on any of the intersection surfaces of the front side, the rear side or the side of the metal sheet with the imaginary second cylinder.

[0175] In both cases, the heat treatment is terminated if the electrical resistance has a constant value over a period of 2 hours.

[0176] The measuring arrangement according to the invention yields a constant resistance value after 144 hours.

[0177] The measurement arrangement of the comparative example yielded a constant resistance value after 60 hours.

[0178] For both metal sheets, the oxygen content was determined by quantitative IR spectroscopy at the end of dispersion hardening using a device from LECO (ONH836). More details about this method can be found in EP 3 971 311 B1. If the chemical composition of the alloy is known, the degree of oxidation can be calculated from the measured oxygen. The degree of oxidation indicates the proportion of the non-precious metal that has been converted into the corresponding oxide during dispersion hardening. Values ​​as close to 100% as possible will be desirable.

[0179] The results are summarized in the following table:

[0180]

[0181] The data show that the measuring arrangement according to the invention allows a significantly more reliable determination of the time required for diffusion hardening.

[0182] List of reference numerals:

[0183] 1 Metal sheet

[0184] 2 Front side of the metal sheet

[0185] 3 Sides of the metal sheet

[0186] 4 Longitudinal edges of the front and rear sides of the metal sheet

[0187] 5 Transverse edges of the front and rear sides of the metal sheet

[0188] 6 Corners of metal sheets

[0189] 7 Imaginary first cylinder

[0190] 7a The axis of the imaginary first cylinder

[0191] 7b Cylindrical jacket of the imaginary first cylinder

[0192] 8a, 8b Intersection surfaces of the front and side surfaces of the metal sheet and the imaginary first cylinder

[0193] 9 Imaginary Second Cylinder

[0194] 9a The axis of the imaginary second cylinder

[0195] 9b Cylindrical jacket of an imaginary second cylinder

[0196] 10a, 10b Intersection surfaces of the front and side surfaces of the metal sheet and the imaginary second cylinder

[0197] 11a First electrical contact surface of the metal sheet

[0198] 11b Second electrical contact surface of the metal sheet

[0199] 12 Current or voltage source

[0200] 13a, 13b: third electrical contact surface and fourth electrical contact surface of the metal sheet

[0201] 14 Voltage or current measuring device

[0202] 15 Metal pipe

[0203] 16 First end face of metal tube

[0204] 17 Lateral surface of metal tube

[0205] 18 Outer boundary line of the first end face

[0206] 19 Inner boundary line of the first end face

[0207] 20 Imaginary first ellipsoid

[0208] 20a Center point of the imaginary first ellipsoid

[0209] 21a, 21b Intersection surface of the first end surface and the lateral surface with the imaginary first ellipsoid

[0210] 22a First electrical contact surface of the metal tube

[0211] 22b Second electrical contact surface of the metal tube

[0212] 23b Intersection of the lateral surface and the imaginary second ellipsoid

[0213] 24a, 24b The third electrical contact surface and the fourth electrical contact surface of the metal tube

Claims

1. A method for measuring electrical variables of a metal-containing molded body during thermal diffusion hardening of the metal-containing molded body, wherein The metal-containing shaped body is a metal sheet (1) having a front side (2), a rear side opposite to the front side (2), and a side surface (3) connecting the front side (2) and the rear side to each other, wherein The front side (2) and the rear side have in each case a length L 纵向边缘 A longitudinal edge (4) of at least 50 mm, a length L 横向边缘 a transverse edge (5) of at least 50 mm and a corner (6) where the longitudinal edge (4) meets the transverse edge (5), The metal sheet (1) has a first electrical contact surface (11a) and a second electrical contact surface (11b) connected to a current or voltage source (12), wherein The first electrical contact surface (11a) is completely located in a plane formed by the intersection planes (8a, 8b) of the front side, the rear side and the side surfaces with an imaginary first cylinder (7), wherein the cylinder axis (7a) of the imaginary first cylinder (7) is perpendicular to the front side (2) of the metal sheet (1) and passes through one of the corners (6) of the front side (2), and the cylinder sheath (7b) of the imaginary first cylinder (7) intersects the longitudinal edge (4) of the front side (2) at a distance a1 from the cylinder axis (7a) and intersects the transverse edge (5) of the front side (2) at a distance b1 from the cylinder axis (7a), wherein a1≤0.2×L 纵向边缘 And b1≤0.2×L 横向边缘 in L 纵向边缘 is the length of the longitudinal edge (4) and L 横向边缘 is the length of the transverse edge (5), the longitudinal edge and the transverse edge meeting at the corner (6) through which the cylinder axis (7a) of the imaginary first cylinder (7) passes, The second electrical contact surface (11b) is completely located in a plane formed by the intersection planes (10a, 10b) of the front side, the rear side and the side surface with an imaginary second cylinder (9), wherein the cylinder axis (9a) of the imaginary second cylinder (9) is perpendicular to the front side (2) and passes through the corner (6) of the front side (2) at the maximum distance from the corner (6) through which the cylinder axis (7a) of the imaginary first cylinder (7) passes, and the cylinder sheath (9b) of the imaginary second cylinder (9) intersects the longitudinal edge (4) of the front side (2) at a distance a2 from the cylinder axis (9a) and intersects the transverse edge (5) of the front side (2) at a distance b2 from the cylinder axis (9a), wherein a2≤0.2×L 纵向边缘 And b2≤0.2×L 横向边缘 in L 纵向边缘 is the length of the longitudinal edge (4) and L 横向边缘 is the length of the transverse edge (5), the longitudinal edge and the transverse edge meeting at the corner (6) through which the cylinder axis (9a) of the imaginary second cylinder (9) passes, The metal sheet (1) has a third electrical contact surface (13a) and a fourth electrical contact surface (13b), and when the first electrical contact surface and the second electrical contact surface (11a, 11b) are connected to a current source (12), the third electrical contact surface and the fourth electrical contact surface are connected to a voltage measuring device (14), or when the first electrical contact surface and the second electrical contact surface (11a, 11b) are connected to a voltage source (12), the third electrical contact surface and the fourth electrical contact surface are connected to a current measuring device (14), The metal sheet (1) is connected to the current or voltage source (12) via its first and second electrical contact surfaces (11a, 11b) and to the voltage or current measuring device (14) via its third and fourth electrical contact surfaces (13a, 13b) by heat treatment, so that oxide particles are formed in the metal sheet (1), and During the heat treatment, the electrical resistance of the metal sheet (1) or an electrical variable proportional to the electrical resistance is determined.

2. The method according to claim 1, wherein the first and second electrical contact surfaces (11a, 11b) are on opposite sides (3) of the metal sheet (1).

3. The method according to claim 1 or 2, wherein the distance between the third electrical contact surface and the fourth electrical contact surface (13a, 13b) is smaller than the distance between the first electrical contact surface and the second electrical contact surface (11a, 11b); and / or wherein the third electrical contact surface and the fourth electrical contact surface (13a, 13b) are located outside the intersection surface (8a, 8b, 10a, 10b) of the front side, the rear side and the side surface of the metal sheet and the imaginary first cylinder and the imaginary second cylinder (7, 9).

4. The method according to any of the preceding claims, wherein the third and fourth electrical contact surfaces (13a, 13b) and the first electrical contact surface (11a) are on the same side (3) of the metal sheet (1), and the second electrical contact surface (11b) is on another side (3), preferably an opposite side (3), of the metal sheet (1).

5. The method according to any one of the preceding claims, wherein the first electrical contact surface or the second electrical contact surface (11a, 11b) is brought into contact with the wires of the current or voltage source (12) and the third and fourth electrical contact surfaces (13a, 13b) are brought into contact with the wires of the voltage or current measuring device (14) under the action of the weight of the metal sheet (1) by the following operation: the metal sheet (1) is placed on the wires via its front side (2), rear side or one of its side sides (3).

6. A method for measuring electrical variables of a metal-containing shaped body during thermal diffusion hardening of the metal-containing shaped body, wherein The metal-containing shaped body is a metal tube (15) or a metal rod, wherein the metal tube (15) or the metal rod Having a length L of at least 50 mm 成型体 and a diameter D in the range of 10 mm to 300 mm 成型体 , end portions, having a first end surface (16) at one of the end portions and a second end surface at the opposite end portion, the first end surface and the second end surface (16) being connected to each other via a lateral surface (17), the first end surface (16) and the second end surface being each defined by an outer boundary line (18), The metal tube (15) or the metal rod has a first electrical contact surface (22a) and a second electrical contact surface (22b), and these electrical contact surfaces are connected to a current or voltage source (12), wherein The first electrical contact surface (22a) is completely located in a plane formed by the intersection plane (21a, 21b) of the lateral surface (17) and the first end surface (16) with an imaginary first ellipsoid (20), wherein the imaginary first ellipsoid (20) has a center point (20a) and semi-axes a1, b1 and c1, wherein the center point (20a) is located on the outer boundary line (18) of the first end surface (16) of the metal tube (15) or the metal rod, and the semi-axis a1 is parallel to the longitudinal axis of the metal tube (15) or the metal rod and has a length L a1 ≤0.2×L 成型体 , and the semi-axes b1 and c1 have length L b1 =L c1 ≤0.4×D 成型体 , The second electrical contact surface (22b) is completely located in a plane formed by the lateral surface (17) and the intersection surface (23b) of the second end surface and an imaginary second ellipsoid, wherein the imaginary second ellipsoid has a center point and semi-axes a2, b2 and c2, the center point of the imaginary second ellipsoid being the point on the outer boundary line of the second end surface of the metal tube (15) or the metal rod that is farthest from the center point (20a) of the imaginary first ellipsoid (20), and the semi-axis a2 is parallel to the longitudinal axis of the metal tube (15) or the metal rod and has a length L a2 ≤0.2×L 成型体 , and the semi-axes b2 and c2 have length L b2 =L c2 ≤0.4×D 成型体 , The metal tube (15) or the metal rod has a third electrical contact surface (24a) and a fourth electrical contact surface (24b), and when the first electrical contact surface and the second electrical contact surface (22a, 22b) are connected to the current source (12), these electrical contact surfaces (24a, 24b) are connected to the voltage measuring device (14), or when the first electrical contact surface and the second electrical contact surface (22a, 22b) are connected to the voltage source (12), these electrical contact surfaces are connected to the current measuring device (14), The metal tube (15) or the metal rod connected to the current or voltage source (12) via its first and second electrical contact surfaces (22a, 22b) and to the voltage or current measuring device (14) via its third and fourth electrical contact surfaces (24a, 24b) is subjected to heat treatment so that oxide particles are formed in the metal tube (15) or the metal rod, and During said heat treatment of said metal tube (15) or metal rod, its electrical resistance or an electrical variable proportional to said electrical resistance is determined.

7. The method according to claim 6, wherein the diameter D of the metal tube (15) 成型体 is its outer diameter, and the first end face and the second end face (16) of the metal tube in each case have an inner boundary line (19) in addition to the outer boundary line (18).

8. A method according to claim 6 or 7, wherein the distance between the third electrical contact surface and the fourth electrical contact surface (24a, 24b) is smaller than the distance between the first electrical contact surface and the second electrical contact surface (22a, 22b); and / or wherein the third electrical contact surface and the fourth electrical contact surface (24a, 24b) are located outside the intersection surface (21a, 21b, 23b) of the end surface (16) and the lateral surface (17) with the imaginary first ellipsoid and the imaginary second ellipsoid (20).

9. The method according to any one of claims 6 to 8, wherein the first electrical contact surface or the second electrical contact surface (22a, 22b) is brought into contact with the wire of the current or voltage source (12) and the third electrical contact surface and the fourth electrical contact surface (24a, 24b) are brought into contact with the wire of the voltage or current measuring device (14) under the action of the gravity of the metal rod or the metal tube (15) by the following operation: the metal rod or the metal tube (15) is placed on the wire with its lateral surface (17) or one of its end surfaces (16).

10. The method according to any of the preceding claims, wherein the metal from which the metal sheet (1), the metal rod or the metal tube (15) is produced is a precious metal alloy containing one or more non-precious metals.

11. The method according to claim 10, wherein the non-noble metal is selected from zirconium, cerium, scandium and yttrium and is present in the noble metal alloy in a total concentration of not more than 1% by weight, and the remainder is one or more noble metals selected from ruthenium, rhodium, gold, palladium, platinum, iridium and osmium and unavoidable impurities.

12. The method according to any of the preceding claims, wherein the heat treatment of the metal sheet (1), metal tube (15) or metal rod is performed at a temperature of at least 750°C.

13. A method according to any one of the preceding claims, wherein the heat treatment of the metal sheet (1), the metal tube (15) or the metal rod is terminated when the electrical resistance of the metal sheet (1), the metal tube (15) or the metal rod or the electrical variable proportional thereto has a constant value for a defined minimum duration.

14. A measurement arrangement comprising A current or voltage source (12), a voltage or current measuring device (14), A metal-containing shaped body, wherein the metal-containing shaped body is a metal sheet (1), the metal sheet having a front side (2), a rear side opposite the front side, and a side surface (3) connecting the front side (2) and the rear side to each other, wherein The front side (2) and the rear side have in each case a length L 纵向边缘 A longitudinal edge (4) of at least 50 mm, a length L 横向边缘 a transverse edge (5) of at least 50 mm and a corner (6) where the longitudinal edge (4) meets the transverse edge (5), The metal sheet (1) has a first electrical contact surface (11a) and a second electrical contact surface (11b) connected to a current or voltage source (12), wherein The first electrical contact surface (11a) is completely located in a plane formed by the intersection plane (8a, 8b) of the front side (2), the rear side and the side surface (3) with an imaginary first cylinder (7), wherein the cylinder axis (7a) of the imaginary first cylinder (7) is perpendicular to the front side (2) of the metal sheet (1) and passes through one of the corners (6) of the front side (2), and the cylinder sheath (7b) of the imaginary first cylinder (7) intersects the longitudinal edge (4) of the front side (2) at a distance a1 from the cylinder axis (7a) and intersects the transverse edge (5) of the front side (2) at a distance b1 from the cylinder axis (7a), wherein a1≤0.2×L 纵向边缘 And b1≤0.2×L 横向边缘 in L 纵向边缘 is the length of the longitudinal edge (4) and L 横向边缘 is the length of the transverse edge (5), the longitudinal edge and the transverse edge meeting at the corner (6) through which the cylinder axis (7a) of the imaginary first cylinder (7) passes, The second electrical contact surface (11b) is completely located in a plane formed by the intersection plane (10a, 10b) of the front side (2), the rear side and the side surface (3) with an imaginary second cylinder (9), wherein the cylinder axis (9a) of the imaginary second cylinder (9) is perpendicular to the front side (2) and passes through the corner (6) of the front side (2) at the maximum distance from the corner (6) through which the cylinder axis (7a) of the imaginary first cylinder (7) passes, and the cylinder sheath (9b) of the imaginary second cylinder (9) intersects the longitudinal edge (4) of the front side (2) at a distance a2 from the cylinder axis (9a) and intersects the transverse edge (5) of the front side (2) at a distance b2 from the cylinder axis (9a), wherein a2≤0.2×L 纵向边缘 And b2≤0.2×L 横向边缘 in L 纵向边缘 is the length of the longitudinal edge (4) and L 横向边缘 is the length of the transverse edge (5), the longitudinal edge and the transverse edge meeting at the corner (6) through which the cylinder axis (9a) of the imaginary second cylinder (9) passes, The metal sheet (1) has a third electrical contact surface (13a) and a fourth electrical contact surface (13b), and when the first electrical contact surface and the second electrical contact surface (11a, 11b) are connected to the current source (12), these electrical contact surfaces (13a, 13b) are connected to the voltage measuring device (14), or when the first electrical contact surface and the second electrical contact surface (11a, 11b) are connected to the voltage source (12), these electrical contact surfaces are connected to the current measuring device (14).

15. A measurement arrangement comprising A current or voltage source (12), a voltage or current measuring device (14), A metal-containing shaped body, wherein the metal-containing shaped body is a metal tube (15) or a metal rod, wherein the metal tube (15) or the metal rod Having a length L of at least 50 mm 成型体 and a diameter D in the range of 10 mm to 300 mm 成型体 , end portions, having a first end surface (16) at one of the ends and a second end surface at the opposite end, the end surfaces (16) being connected to each other by lateral surfaces (17) and each being delimited by an outer boundary line (18), The metal tube (15) or the metal rod has a first electrical contact surface (22a) and a second electrical contact surface (22b), wherein the first electrical contact surface and the second electrical contact surface are connected to the current or voltage source (12), wherein The first electrical contact surface (22a) is completely located in a plane formed by the intersection plane (21a, 21b) of the lateral surface (17) and the first end surface (16) with an imaginary first ellipsoid (20), wherein the imaginary first ellipsoid (20) has a center point (20a) and semi-axes a1, b1 and c1, wherein the center point (20a) is located on the outer boundary line (18) of the first end surface (16) of the metal tube (15) or the metal rod, and the semi-axis a1 is parallel to the longitudinal axis of the metal tube (15) or the metal rod and has a length L a1 ≤0.2×L 成型体 , and the semi-axes b1 and c1 have length L b1 =L c1 ≤0.4×D 成型体 , The second electrical contact surface (22b) is completely located in a plane formed by the lateral surface (17) and the intersection surface (23b) of the second end surface and an imaginary second ellipsoid, wherein the imaginary second ellipsoid has a center point and semi-axes a2, b2 and c2, the center point of the imaginary second ellipsoid being the point on the outer boundary line of the second end surface of the metal tube (15) or the metal rod that is farthest from the center point (20a) of the imaginary first ellipsoid (20), and the semi-axis a2 is parallel to the longitudinal axis of the metal tube (15) or the metal rod and has a length L a2 ≤0.2×L 成型体 , and the semi-axes b2 and c2 have length L b2 =L c2 ≤0.4×D 成型体 , The metal tube (15) or the metal rod has a third electrical contact surface (24a) and a fourth electrical contact surface (24b), and when the first electrical contact surface and the second electrical contact surface (22a, 22b) are connected to a current source (12), these electrical contact surfaces (24a, 24b) are connected to a voltage measuring device (14), or when the first electrical contact surface and the second electrical contact surface (22a, 22b) are connected to a voltage source (12), these electrical contact surfaces are connected to a current measuring device (14).

16. Use of the measuring arrangement according to claim 14 or 15 for determining the duration of thermal diffusion hardening of the metal sheet (1), metal rod or metal tube (15).

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