Superconducting bare and thin strip and methods and apparatus for making same

Abstract

This application relates to a superconducting bare tape and a superconducting thin tape, as well as a method and apparatus for preparing both. The superconducting bare tape comprises a metal substrate having a first surface and a second surface that are opposite to each other. The first surface is sequentially deposited with a textured layer, a superconducting layer, and a silver layer. At least a portion of the second surface is a treated surface that has undergone polishing and / or chemical etching to thin it, and the thinning thickness of the metal substrate at the treated surface is not less than 5 micrometers. This application aims to obtain thin superconducting tapes using a simple and feasible method, thereby improving the engineering current density of the superconducting tape.

Description

Technical Field

[0001] This application relates to the field of superconductivity, specifically to a superconducting bare tape and a superconducting thin tape, as well as the preparation method and equipment for both. Background Technology

[0002] After more than 20 years of development, there are now more than 10 developers of second-generation high-temperature superconducting tapes in the world. Second-generation superconducting tapes are now widely used to manufacture superconducting current limiters, superconducting magnets and power cables, forming an emerging industry.

[0003] Second-generation superconducting tapes are made by sequentially depositing a texture layer, a superconducting layer, and a silver layer on the upper surface of a flexible metal alloy substrate, forming a bare superconducting tape—also known as a coated conductor. Finally, stabilizing layers, also called encapsulation, are prepared on the top and bottom surfaces of the bare superconducting tape to form the final product. Stabilizing layer materials include copper, brass, and stainless steel. Encapsulation methods include electroplating the stabilizing layer or brazing the stabilizing layer. The metal substrate of second-generation tapes uses Hastelloy, a high-temperature oxidation-resistant alloy, and is typically hundreds to thousands of meters long, a few to tens of millimeters wide, and 50-100 micrometers thick. The thickness of the superconducting thin film + textured thin film + silver layer deposited on it is about 5-6 micrometers. For a 4-millimeter-wide tape, the critical current Ic of commercially available superconducting tapes is generally 100-170A, and the price of the tape is generally proportional to Ic.

[0004] Recently, with the widespread application of second-generation superconducting tapes, users have discovered that the key performance indicator (KPI) is not the critical current (Ic), but rather the engineering current density (Ie), where Ie = Ic / tape thickness. More and more users are starting to pay based on engineering current density. For example, for the same 150A tape, if the thickness of the metal substrate is reduced from 60 micrometers to 30 micrometers, and the encapsulation is copper-plated with a thickness of 30 micrometers, the total thickness is reduced from 90 micrometers to 60 micrometers, increasing the price by 50%. Besides increasing Ie, thinner tapes, at the same bending radius, result in less stress acting on the superconducting film, allowing for the winding of small-diameter superconducting cables or the fabrication of high-torsion superconducting conductors. Thinner superconducting bare tapes also improve the yield of soldered encapsulations because the stabilizing layer experiences less elastic deformation during soldering, making it less prone to springing open after extrusion, thus preventing insufficient solder in the encapsulation tape.

[0005] Several years ago, various strip manufacturers began developing second-generation thin strip products. However, this is not an easy task because: 1. The problem of strip deformation must be solved. One important reason why the current strip thickness is no less than 50 micrometers, or even no less than 60 micrometers, is that most strip deposition systems use strip winding systems, allowing the strip to continuously pass through the heated substrate / deposition area N times. This can increase the throughput N times, but it also increases the friction on the strip N times. If the strip is too thin, it will deform, so the strip cannot be too thin. To produce thin strips now, the strip delivery system must be modified or even rebuilt so that it can run thin strips without deformation. This is a costly project, and currently only two companies in the world have initially completed this work.

[0006] 2. Significantly thinning the strip introduces various processing problems. For example, the inherent stress in the thinner film causes the strip to bend, resulting in misalignment between the strip and the heating substrate, affecting temperature control. As the deposition thickness increases, the film stress gradually increases, and the strip bending becomes more severe, causing the strip temperature to deviate further from the optimal temperature. Worse still, the bending causes uneven temperature distribution across the strip width, making it impossible to simultaneously reach the optimal deposition temperature within the strip width, leading to a decline in strip performance. This necessitates the development of new, complex processes, which are costly and time-consuming. Generally, the more complex the process, the higher the control requirements, and the lower the yield.

[0007] Even with sufficient financial and time investment, current methods will eventually reach their limits. The thinner the metal substrate, the more complex the processing equipment, the lower the yield, and the higher the cost, eventually making it impossible to achieve. The thinnest tape reported in the world is currently 30-35 micrometers (a company once claimed to be developing a 25-micrometer tape, but the final product was only 30 micrometers), indicating that 30 micrometers is already the limit of current methods. Applications hope for higher Ie values ​​and thinner superconducting tapes in the future, allowing for smaller superconducting power devices, reduced cooling costs, and, more importantly, increased magnetic field strength, reduced magnetic field inhomogeneity, stress inhomogeneity, and shielding current. Summary of the Invention

[0008] The technical problem to be solved by this application is: to address the above-mentioned problems, to propose a method and equipment for preparing superconducting bare tape and superconducting thin tape, and to obtain thin superconducting tape in a simpler way, so as to improve the engineering current density of superconducting tape.

[0009] The technical solution of this application is:

[0010] A superconducting bare tape includes a metal substrate having a first surface and a second surface that are opposite to each other. The first surface is sequentially deposited with a textured layer, a superconducting layer and a silver layer. At least a portion of the second surface is a treated surface that has been thinned by polishing and / or chemical etching, and the thinning thickness of the superconducting bare tape at the treated surface is not less than 5 micrometers.

[0011] Preferably, all parts of the second surface are treated surfaces that have been polished or / and chemically etched.

[0012] Preferably, the second surface is subjected to different degrees of polishing and / or chemical etching treatment, so that the metal substrate has an uneven thickness in its length direction.

[0013] A superconducting thin strip material includes a superconducting bare strip with the above-described structure and a stabilizing layer bonded to the superconducting bare strip.

[0014] A method for preparing a superconducting bare tape includes: sequentially depositing a textured layer, a superconducting layer, and a silver layer on a first surface of a metal substrate, and then thinning a second surface of the metal substrate that is away from the first surface.

[0015] Preferably, the thinning process includes mechanical polishing and / or chemical etching of the second surface of the metal substrate.

[0016] Preferably, the mechanical grinding is selected from any one or any combination of two or more of the following: grinding wheel grinding, belt sander grinding, vibratory grinding, and sandblasting.

[0017] A method for preparing a superconducting thin strip includes:

[0018] The steps for preparing superconducting bare tapes using the above-described method; and

[0019] The step of fabricating a stabilizing layer on the superconducting bare tape.

[0020] An apparatus for preparing superconducting bare tapes or superconducting thin tapes, comprising:

[0021] A superconducting bare tape unwinder used to provide and release the superconducting bare tape to be polished.

[0022] A superconducting tape rewinder for continuously unwinding the superconducting bare tape to be polished, and

[0023] A superconducting bare tape polisher is arranged between the superconducting bare tape unwinder and the superconducting bare tape rewinder, and a backup superconducting bare tape polisher is used to replace the superconducting bare tape polisher.

[0024] Preferably, both the superconducting bare tape polishing machine and the superconducting bare tape backup polishing machine are belt polishing machines, each belt polishing machine comprising a rotating polishing belt, a portion of which is immersed in a coolant tank containing coolant.

[0025] The beneficial effects of this application are:

[0026] 1. After obtaining a superconducting bare tape of a certain thickness using existing mature processes, this application further thins the metal substrate in the superconducting bare tape, avoiding a series of problems associated with depositing high-temperature superconducting thin films on existing alloy thin tapes. Moreover, the superconducting bare tape can be thinned to various sizes, breaking through the current limit of 30 micrometers for superconducting tapes and improving the engineering current density of superconducting tapes.

[0027] 2. This application only grinds the side of the metal substrate that is away from the texture layer, superconducting layer, and silver layer, without damaging the texture layer, superconducting layer, and silver layer on the other side. Moreover, the part that is ground off is entirely the metal substrate and will not affect the conductivity of the superconducting tape product.

[0028] 3. Using the method of this application, the grinding area of ​​the metal substrate can be selected as needed, without having to grind the entire back surface of the metal substrate. Even if we grind the entire back surface of the metal substrate, different parts can be ground to different degrees, thereby giving the metal substrate an uneven thickness along its length to meet the needs of special products.

[0029] 4. By installing working and standby grinding machines along the conveying route of the superconducting bare tape, continuous and uninterrupted production of the superconducting bare tape is achieved.

[0030] 5. Immerse a portion of the grinding belt of the grinder into the coolant tank to cool the heated grinding belt using the coolant stored in the tank. Furthermore, the rotating grinding belt will deliver coolant to the grinding surface of the superconducting strip, cooling the superconducting strip from the grinding surface without contaminating the non-grinding surfaces. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings of the embodiments will be briefly described below. Obviously, the drawings described below only relate to some embodiments of this application, and are not intended to limit this application.

[0032] Figure 1 This is a schematic diagram of the structure of the superconducting bare tape in the embodiments of this application.

[0033] Figure 2 This is a schematic diagram of the structure of the superconducting bare tape thinning device in the embodiments of this application.

[0034] Wherein: 100-superconducting bare tape, 101-metal base tape, 102-textured layer, 103-superconducting layer, 104-silver layer, 200-superconducting bare tape polishing machine, 300-superconducting bare tape spare polishing machine, 231-polishing belt, 232-coolant tank, 233-coolant, 400-superconducting bare tape unwinder, 500-superconducting tape rewinder, 600-guide roller. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the described embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0036] Reference Figure 1 As shown, similar to the traditional method for preparing superconducting bare tapes, the method proposed in this embodiment also includes the steps of sequentially depositing a textured layer 102, a superconducting layer 103, and a silver layer 104 on the first surface of the metal substrate 101. The metal substrate 101 used as the raw material still employs the traditional thickness of 50 micrometers or more.

[0037] After completing the aforementioned processes, conventional superconducting bare tapes are already finished. However, as described in the background section of this application, such superconducting bare tapes are relatively thick, resulting in superconducting tapes made from these bare tapes typically having a thickness of 50 micrometers or more and a relatively low engineering current density. For this reason, in this embodiment, after completing the deposition processes of the texture layer 102, the superconducting layer 103, and the silver layer 104, the second surface (non-deposition surface) of the metal substrate 101 facing away from the first surface is thinned, thereby reducing the thickness of the superconducting bare tape.

[0038] After reducing the thickness of the superconducting bare strip 100 by the above-mentioned thinning treatment, it is only necessary to use the superconducting bare strip 100 as raw material to perform conventional processing using the existing mature process—including the fabrication of a stabilizing layer on the superconducting bare strip—to obtain a superconducting thin strip material with small thickness and high engineering current density.

[0039] In this embodiment, the aforementioned thinning process specifically involves mechanically grinding the second surface of the metal substrate. Of course, other processes can also be used to implement the thinning process, such as chemically etching the second surface of the metal substrate, or simultaneously mechanically grinding and chemically etching the second surface of the metal substrate.

[0040] There are many types of mechanical grinding, including grinding with a grinding wheel, belt sander, vibratory grinding, or sandblasting, and of course, a combination of the above four grinding methods.

[0041] Because in this embodiment, after obtaining a superconducting bare tape with a certain thickness, the metal base strip in the superconducting bare tape is mechanically polished. Even if the metal base strip is polished to a few micrometers, the remaining thickness of the superconducting bare tape still has enough structural strength to resist the polishing friction, so that the superconducting bare tape is not easily deformed during the polishing process.

[0042] In this embodiment, only the side of the metal substrate 101 that is away from the texture layer 102, superconducting layer 103, and silver layer 104 (the second surface) is polished, without damaging the texture layer 102, superconducting layer 103, and silver layer 104 on the other side. Moreover, only the metal substrate 101 is polished, and it does not affect the conductivity of the superconducting tape.

[0043] In practical applications, we can select specific areas of the second surface of the metal substrate 101 to be polished, rather than polishing the entire second surface. Even if we polish the entire second surface of the metal substrate 101, we can still polish different areas to varying degrees, resulting in a non-uniform thickness of the metal substrate 101 along its length. For example, when winding certain magnets with superconducting tape, the inner ring needs to be thinner and the outer ring thicker. This type of superconducting tape with varying thickness along its length provides a completely new application method, enabling some products to achieve functions that were previously impossible.

[0044] To significantly reduce the thickness of the superconducting material and thus substantially increase its engineering current density, the polishing thickness of the second surface of the metal substrate 101 should ideally be above 5 micrometers. We know that, due to manufacturing processes, the unpolished back surface (second surface) of a raw superconducting strip has the following characteristics: a relatively thick intrinsic oxide layer containing elements Gd, Y, Cu, and Ba from high-temperature superconducting films, and inevitably also containing elements Mg, La, Al, and Y from the texture layer (especially at the edges of the back surface). When we polish away more than 5 micrometers of the back surface of the raw superconducting strip, these characteristics almost entirely disappear. If we can detect an intrinsic oxide layer thickness of less than 10 nanometers on the back surface of the superconducting strip, or if we cannot detect elements Gd, Y, Cu, and Ba from high-temperature superconducting films, or elements Mg, La, Al, and Y from the texture layer on the back surface of the superconducting strip, we can indirectly prove that the back surface has been polished, and that the polishing thickness is above 5 micrometers.

[0045] In theory, the maximum grinding size of the superconducting bare tape 100 is close to the thickness of the metal substrate 101. Therefore, by using the above processing method, the thickness of the superconducting bare tape 100 and the superconducting tape can be reduced to 30 micrometers or even smaller.

[0046] In order to implement the above process, Figure 2 This invention illustrates an apparatus for thinning raw superconducting tapes. Since thinning the raw superconducting tape is a step in fabricating a thin target superconducting tape, this apparatus is also a fabrication apparatus for superconducting tapes. Furthermore, because fabricating raw superconducting tapes is a step in fabricating thin superconducting tapes, this apparatus is also a fabrication apparatus for thin superconducting tapes.

[0047] The aforementioned equipment mainly includes a 400-unit superconducting bare tape unwinder, a 500-unit superconducting tape rewinder, and a 200-unit superconducting bare tape polishing machine. Among them:

[0048] A superconducting bare tape unwinder 400 is used to provide and unwind the superconducting bare tape 100 to be polished. A superconducting strip rewinder 500 is used to pull the superconducting bare tape to be polished released by the superconducting bare tape unwinder, so that the superconducting bare tape 100 to be polished is continuously unwound under the aforementioned traction force. A superconducting bare tape polisher 200 is arranged between the superconducting bare tape unwinder and the superconducting bare tape rewinder, that is, on the unwinding path of the superconducting bare tape 100, to polish the released superconducting bare tape.

[0049] Because the superconducting bare tape polisher 200 is continuously consumed during the polishing process, resulting in a decrease in polishing efficiency, it is necessary to stop the machine and replace the polishing workpiece—such as the abrasive belt. In order to achieve continuous and uninterrupted production of superconducting bare tape, this embodiment also configures a backup superconducting bare tape polisher 300 between the superconducting bare tape unwinder and the superconducting bare tape rewinder to replace the superconducting bare tape polisher 200.

[0050] Under normal circumstances, the superconducting bare tape polishing machine 200 is in working condition, while the standby polishing machine 300 is in a standby, non-working state, not in contact with the superconducting bare tape for polishing, but waiting to replace the polishing machine that has been worn out. When the superconducting bare tape polishing machine 200 reaches its set lifespan, it is de-contaminated from the superconducting bare tape, and at the same time, the standby polishing machine 300 moves to a position where it can contact the superconducting bare tape. This achieves seamless replacement of the working polishing machine by the standby polishing machine.

[0051] In this embodiment, both the superconducting bare tape polishing machine 200 and the standby superconducting bare tape polishing machine 300 are belt polishers, both including a rotating polishing belt 231. During operation, the polishing belt 231 contacts and polishes the superconducting bare tape. Furthermore, a portion of the polishing belt 231 is immersed in a coolant tank 232 to cool the heated polishing belt 231 using the coolant 233 stored in the coolant tank 232. The rotating polishing belt 231 immerses and carries the coolant 233 to the polished surface of the superconducting bare tape, cooling the superconducting bare tape from the polished surface without contaminating the non-polished surface of the superconducting bare tape.

[0052] The above are merely exemplary embodiments of this application and are not intended to limit the scope of protection of this application, which is determined by the appended claims.

Claims

1. A method for preparing a superconducting bare band, comprising: A textured layer, a superconducting layer, and a silver layer are sequentially deposited on the first surface of a metal substrate, characterized in that the second surface of the metal substrate facing away from the first surface is then thinned. The second surface is the lower surface of the metal substrate, and the thinning process includes mechanically polishing the second surface on the lower side of the superconducting bare strip using a polishing belt (231) of a superconducting bare strip polishing machine (200) that makes a rotary motion. A portion of the abrasive belt (231) is immersed in a coolant tank (232) containing coolant (233), thereby impregnating and carrying the coolant (233) to the second surface and thereby cooling the superconducting bare belt.

2. A method for preparing a superconducting thin strip, characterized in that, include: The steps for preparing superconducting bare tape using the preparation method described in claim 1; The step of fabricating a stabilizing layer on the superconducting bare tape.

Images