AMORPHOUS METAL STRIP AND METHOD FOR PRODUCING AN AMORPHOUS METAL STRIP

Abstract

A method for the production of a metal strip is provided. The method includes providing an amorphous metal strip having a first main surface and a second, opposing main surface. The first and/or the second main surface are treated with a wet-chemical etching process and/or a photochemical etching process.

Claims

1. A method for producing a metal strip, comprising: providing an amorphous metal strip having a first main surface and a second, opposing main surface, inspecting a surface and/or cross-section of the first and/or the second main surface of the amorphous metal strip, covering at least parts of the first main surface and/or at least parts of the second main surface with a chemically resistant coating, and photochemical etching and/or wet-chemical etching at least one region of the first main surface which is not covered by, or before covering with, the chemically resistant coating and/or at least one region of the second main surface which is not covered by, or before covering with, the chemically resistant coating.

2. (canceled)

3. (canceled)

4. (canceled)

5. A method according to claim 1, wherein the etching removes at least a part of the strip and reduces the surface roughness R.sub.a and/or R.sub.max.

6. A method according to claim 1, wherein the inspecting a surface and/or cross-section of the first and/or the second main surface of the amorphous metal strip comprises: visually examining a surface and/or performing a cross-section inspection of the amorphous metal strip, optically examining a surface and/or performing a cross-section inspection of the amorphous metal strip, or placing a profilometer on the first and/or the second main surface of the amorphous metal strip that contacts the first and/or second main surface of the amorphous strip to examine the surface and/or cross-section of the amorphous metal strip.

7. (canceled)

8. (canceled)

9. A method according to claim 1, wherein the method is carried out as part of a single- or multi-step reel-to-reel process.

10. A method according to claim 1, further comprising: producing the metal strip using a rapid solidification technology.

11. A method according to claim 10, wherein the amorphous metal strip is formed by casting a molten mass made of an alloy with a metalloid content of 15 at. % to 30 at. % onto a moving outer surface of a moving cooling body, the molten mass solidifying on the outer surface and forming the amorphous metal strip.

12. A method according to claim 10, wherein the outer surface of the cooling body is continuously processed in order to smooth the outer surface of the cooling body while the molten mass is cast on the moving outer surface of the cooling body.

13. A method according to claim 1, further comprising: heat treating the amorphous metal strip in order to transform the amorphous metal strip to a nanocrystalline state.

14. (canceled)

15. A method according to claim 13, wherein the heat treatment is carried out at a temperature Ta, where 450 C.T.sub.a750 C., in order to produce a nanocrystalline structure in the metal strip in which at least 80 vol. % of the grains have an average size of less than 100 nm.

16. A method according to claim 15, wherein the metal strip is continuously heat treated under tensile stress of 1 MPa to 1000 MPa.

17. A method according to claim 16, wherein the metal strip is pulled continuously through a continuous furnace at a speed s such that a dwell time of the metal strip in a zone of the continuous furnace with a temperature T.sub.a is between two seconds and 10 minutes.

18. (canceled)

19. A method according to claim 1, the amorphous metal strip having the following alloy composition and up to 0.5 wt. % incidental impurities:
Fe.sub.100-a-b-w-x-y-zT.sub.a M.sub.bSi.sub.wB.sub.xP.sub.y C.sub.z (in at. %), T denoting one or more of the elements in the group consisting of Co, Ni, Cu, Cr and V, M denoting one or more of the elements in the group consisting of Nb, Mo and T.sub.a, and where 0a70, 0b9, 0w18, 5x20, 0y7 and 0z2.

20. (canceled)

21. (canceled)

22. (canceled)

23. (canceled)

24. (canceled)

25. (canceled)

26. A method according to claim 1, wherein the etching step includes wet-chemical etching the entire first and second main surfaces of the amorphous metal strip, and the covering step includes applying the chemically resistant coating to at least parts of the first main surface and/or at least parts of the second main surface after the wet-chemically etching.

27. A method according to claim 1 including identifying defects in the first main surface and/or second main surface, the covering step includes applying the chemically resistant coating such that the defects are uncovered by the chemically resistant coating and remaining regions of the first main surface and/or second main surface are covered by the chemically resistant coating, and the etching step including etching the defects.

28. A method according to claim 27, wherein the covering step includes selectively applying the chemically resistant coating to the first main surface and/or the second main surface such that the defects are uncovered by the chemically resistant coating.

29. A method according to claim 28, wherein the chemically resistant coating is selectively applied by printing.

30. A method according to claim 1, wherein the chemically resistant coating comprises a photosensitive material and is selectively illuminated by light, wherein regions of the chemically resistant coating which are not illuminated by light are removed to uncover defects.

31. A method according to claim 1, further comprising removing the chemically resistant coating.

32. A method according to claim 31, further comprising forming a manufactured part from the etched amorphous metal strip, wherein the manufactured part is one or more of the group consisting of a coil spring, a leaf spring, a mechanical and magnetic spring, a blade, a shaving foil, a part comprising scratch-resistant and cut-resistant surfaces, a bendable protective sheathing, a planar single-layer inductor, a layer of a stacked, multi-layer planar inductor, a layer of a stacked, multi-layer, annular planar inductor and a part of an inductive component.

33. A method according to claim 11, the amorphous metal strip having the following alloy composition and up to 0.5 wt. % incidental impurities:
Fe100-a-b-w-x-y-z Ta Mb Siw Bx Py Cz (in at. %), T denoting one or more of the elements in the group consisting of Co, Ni, Cu, Cr and V, M denoting one or more of the elements in the group consisting of Nb, Mo and T.sub.a, and where 0a70, 0b9, 0w18, 5x20, 0y7, and 0z2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0139] FIG. 1 shows a schematic representation of a chain of processes for a reel-to-reel process.

[0140] FIG. 2 shows a schematic representation of a wet-chemical surface treatment process involving the complete etching of the strip.

[0141] FIG. 3 shows a schematic representation of a wet-chemical surface treatment process involving the filling of cavities with a chemically resistant coating and the subsequent etching away of the uncovered areas.

[0142] FIG. 4 shows a schematic representation of a wet-chemical surface treatment process involving the application of a chemically resistant coating around vertically projecting defects and the subsequent etching away of the uncovered areas.

[0143] FIG. 5 shows a schematic representation of a wet-chemical surface treatment process involving the application of etching fluid to vertically projecting defects only.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0144] FIG. 1 shows a schematic representation of a chain of processes for a reel-to-reel process for the production of a metal strip, in particular for the subsequent treatment of an amorphous or nanocrystalline metal strip 1. The metal strip 1 has a first main surface 2 and an opposing, second main surface 3 and has been produced as an amorphous strip or amorphous foil using a rapid solidification technology. Typically, the first main surface 2 is the side of the strip that solidified open to the air, while the second main surface 3 is the side of the strip that was in contact with the casting wheel.

[0145] The reel-to-reel process according to this embodiment features continuous surface inspection (A1) of both sides of the strip, measurement of the strip profile (A2) and measurement of the surface roughness (A3) as well as a wet-chemical surface treatment process (B) and a lateral photochemical etching process (C) for lateral shaping. The result is a metal strip 1 that is smoother and more plane-parallel. In addition, this metal strip 1 can be used to make smooth, plane-parallel amorphous plates 5.

[0146] The continuous surface inspection (A1) supplies images (x-y dimension) and position and size data on surface defects from both sides of the strip. Determining the strip profile (A2) provides the local thickness as a function of the lateral strip position y.

[0147] The process chain shown in FIG. 1 and described below can be used to produce specific smooth, plane-parallel amorphous plates 5 from amorphous metal strips or metal foils 1. The process chain may be one single reel-to-reel process or divided into a plurality of reel-to-reel processes.

[0148] Initially, the amorphous metal foil 1 undergoes a surface and cross-section inspection (A). To this end, the strip material 1 is subjected to a continuous surface inspection (A1) from both sides 2, 3 once it has been unwound from the start reel and is characterised in terms of surface defects (pimples, scoring, holes, etc.). Immediately before or after this, the strip profile (A2) and surface roughness are measured (A3) either continuously or at discrete intervals using a profilometer. The following data can be recorded during A and saved to a database: pimples, holes, scoring in various directions, thickness and shape of strip cross section and surface roughness. This data is used to control all the following processes in a spatially resolved manner. The data obtained may be spatially resolved and provide information about the extent of the defect.

[0149] The lateral and vertical extents of problematic surface defects are reduced in a wet-chemical surface treatment process (B). To this end, surface material is removed completely or selectively using a controlled etching process. The surface material can be removed from both sides of the strip, i.e. a) from the side 3 of the strip that was in contact with the casting wheel and b) from the side 2 of the strip that solidified open to the air. The following methods can be used singly or together or consecutively: the complete etching of the strip (B1) from one (FIG. 2) or both sides of the strip 2, 3, as shown schematically by the arrows 10; the filling of cavities or indentations 6 (FIG. 3) with a chemically resistant coating 7 (B2) and/or the application of a chemically resistant coating 7 around vertically projecting defects 8 (FIG. 4) (B3) and the subsequent etching away of uncovered areas 8, or the application of etching fluid 9 (FIG. 5) to the vertically projecting defects only 8 (B4).

[0150] The etching processes described in B require a knowledge of the lateral position and the lateral and vertical extent of the defects, e.g. the indented sections 6 and raised sections 8, and an etching process that is controlled in terms of time and quantity of etching fluid. The size of the surface treated depends on the way the process is conducted and may range from 1 mm.sup.2 to 100,000 cm.sup.2. Optionally, the strip that is wet-chemically treated in B can be subject to a further surface and cross-section inspection A. The process B can be carried out a plurality of times until the desired surface quality, e.g. reduced unevenness, reduced surface defects and reduced surface roughness, is achieved. In particular, optically undetectable crystals close to the surface can be removed by the separate, global etching of the strip 1 from one or both 2, 3 sides (B1). The process B may be dispensed with locally if the amorphous metal foil already has the desired surface quality locally.

[0151] After the wet-chemical etching process (B), a photochemical etching process C can be carried out in order to produce a smoother surface 2 and/or 3. The lateral shaping of the smooth, plane-parallel amorphous plate 5 takes place during the lateral photochemical etching process (C). First a chemically resistant and laterally structured coating of any shape is applied to one side, e.g. the main surface 2, of the amorphous metal foil 1, then the non-coated areas of the metal foil are etched through from the same side with an appropriate etching fluid. The other side of the amorphous metal foil, e.g. the second main surface 3, can also be covered with a chemically resistant coating. The photochemical etching takes place in a continuously running reel-to-reel process. The aforementioned chemically resistant and laterally structured coating is applied such that the positions of the plates 5 to be etched from it are continuously adjusted locally using the results of the surface and cross-section inspection (A). In particular, every effort is made to ensure that the plates are free of defects and have the least possible roughness and a plane-parallel cross section.

[0152] The unique combination of processes A+B+C ensures that the smooth, plane-parallel plates 5 used for the application have a reduced risk of breaking or tearing when the plate is being formed or bent, that the elongation at break and bending-fatigue strength of the plate 5 are increased, that the fill factor is increased for magnetic applications when stacking rings or plates, that transition to ferromagnetic saturation is improved and coercive field H.sub.c is reduced.

[0153] In other embodiments, either the wet-chemical etching process B or the photochemical etching process C may be used alone. It would also be possible to omit the optical inspection included in method A if the surface quality of the metal strip 1 treated were sufficient for the planned application. It would also be possible to repeat the entire process, i.e. processes A+B+C, or to repeat one or more of these processes. For example, processes A and/or B could be repeated several times and followed by process C, carried out only once.

[0154] Various etching processes B are schematically represented in FIGS. 2 to 5. FIG. 2 shows a schematic representation of a wet-chemical surface treatment process involving the complete etching of the strip 1 from either one or both sides of the strip 2, 3. As represented schematically by the arrows 10, the etching fluid removes a layer close to the surface, thereby reducing or even entirely eliminating the lateral and vertical extent of vertically projecting surface defects 11, as indicated by reference numeral 11. This occurs because the etching fluid is able to attack the material of the vertically projecting surface defects 11 both from above and from the side and that these surface defects are etched in preference to flatter regions of the surface. The etching process is controlled in terms of time and the quantity of etching fluid such that material is removed from the surface over a vertical range corresponding to the smallest or the largest (or an intermediary) original height of the project defects 11 within the area treated.

[0155] FIG. 3 shows a schematic representation of a wet-chemical surface treatment process involving the filling of cavities 6 with a chemically resistant coating 7 and the subsequent etching away of the uncovered areas 12, as schematically represented by the arrows 10. The result is a surface 1 with cavities 6 that are clearly flatter and even completely eliminated. The etching process is controlled in terms of time and quantity of etching fluid, as represented schematically by the arrows 10, such that material is removed from the surface over a vertical range corresponding to the smallest or the largest (or an intermediate) original depth of the cavities 6 within the area treated.

[0156] FIG. 4 shows a schematic representation of a wet-chemical surface treatment process involving the application of a chemically resistant coating 7 around vertically projecting defects 8 and the subsequent etching away of the uncovered areas, i.e. the projecting defects 8. The result is a metal strip 1 with a surface 2 and/or a surface 3 with clearly flatter projecting defects or even a surface with no projecting defects at all. The etching process is controlled in terms of time and quantity of etching fluid, as represented schematically by arrow 10, such that material is removed from the surface over a vertical range corresponding to the smallest or the largest (or an intermediate) original height of the projecting defects within the area treated.

[0157] FIG. 5 shows a schematic representation of a wet-chemical surface treatment process involving the application of etching fluid 9 to vertically projecting defects 8 only. The result is a metal strip 1 with a surface 2 and/or a surface 3 with clearly flatter projecting defects or even a surface with no projecting defects at all. The etching process is controlled in terms of time, location, extent and quantity of etching fluid (arrow 10) such that material is removed from the surface over a vertical range corresponding to the smallest or the largest (or an intermediate) original height of the projecting defects within the area treated.

[0158] The end products of the chain of processes described are parts 5 or plates that are ultimately detached from the continuous strip 1. The chain of processes described significantly reduces or completely removes surface defects and edge defects from these parts 5.

[0159] These smooth, plane-parallel, amorphous plates 5 can be used for mechanical applications such as: [0160] coil springs [0161] leaf springs [0162] combinations of mechanical and magnetic springs [0163] blades [0164] shaving foils [0165] scratch-resistant and cut-resistant surfaces, protective sheathing and/or for magnetic applications such as: [0166] planar (single-layer) inductors [0167] stacked, multi-layer planar inductors [0168] stacked, multi-layer, annular planar inductors [0169] inductive components.

[0170] The improvements in both mechanical properties and magnetic properties can be advantageous in magnetic applications.