Stainless Steel Tape Research Articles

Investigation of the energizing characteristics of a metal-insulation iron-based superconducting coil

With the progress of iron-based superconducting wire and tape fabrication technologies, extensive research has been conducted on iron-based superconducting coils. A deep understanding of the energizing characteristics of these coils is crucial for their large-scale application. This study investigates two metal-insulated double pancake coils, each having a different number of turns and co-wound with Ba0.6K0.4Fe2As2 iron-based superconducting tape and stainless-steel tape. We conducted critical current tests, sudden-discharge experiments, and charge-discharge cycles at 4.2 K to obtain the time constants and characteristic resistances of the coils. Additionally, the impact of stainless-steel as co-wound material on coil performance was analyzed. Theoretical models were employed to calculate the charging processes and validate them against experimental results. This research offers valuable insights for the practical application of iron-based superconducting materials.

26.86-tesla direct-current magnetic field generated with an all-REBCO superconducting magnet

This paper reports an all REBCO (REBa2Cu3Ox, where RE = Y, Gd) superconducting magnet that generated a direct-current magnetic field of 26.86 T at 4.2 K in self-field, which is the highest magnetic field achieved by the high temperature superconducting (HTS) magnet. The magnet consists of a stack of 10 double pancake (DP) coils wound with two different width REBCO conductors, and the no-insulation (NI) winding technology was applied to increase its engineering current density. The inner and outer winding diameters and overall height of the magnet are 30 mm, 103.98 mm, and 102.6 mm, respectively. In order to control the stress risk in HTS magnet, the over-banding made of high elastic modulus stainless steel tapes was employed to the magnet. In addition, no obvious degradation was found in the performance of the magnet after quench at 26.86 T of 295.5 A. These test results demonstrate the great potential of REBCO magnets in high field applications.

Numerical Study on Fault Current Characteristics of Self-Shielded HTS DC Cables Made of REBCO Tapes in Parallel With Stainless Steel Tapes

Numerical Study on Fault Current Characteristics of Self-Shielded HTS DC Cables Made of REBCO Tapes in Parallel With Stainless Steel Tapes

Development of metal-insulated iron-based superconducting coils and charging tests under high magnetic fields up to 32 T

To explore the potential of iron-based superconducting (IBS) tapes in high-field applications, IBS pancake coils were dry-wound using the uninsulated IBS tape, supplemented with cowound stainless steel tapes for reinforcement. We have successfully fabricated a double pancake coil (DP-1) and a series-connected coil consisting of six DP coils (DP-6). These coils underwent multiple charging tests in a 35 T resistive magnet and retesting in a 14 T superconducting magnet. After conducting multiple rounds of retesting in two different background field magnets, it was found that the IBS coils did not show any degradation in their current-carrying performance. The critical current (I c) value of the DP-1 at 4.2 K and 32 T reached 60 A. To systematically evaluate the I c performance of the six coils in the DP-6, we monitored the V–I curves between 26 voltage taps. The resistive voltage rise was observed at low charging currents, indicating that each coil has suffered different levels of damage. Nevertheless, the overcurrent tests demonstrated that the IBS coil can still carry a current far exceeding its I c without irreversible degradation. We concluded the possible reasons for these phenomena by analyzing the experimental details and test data. In addition, the coil’s internal structure was observed to assess the quality of coil winding, joint soldering, and epoxy resin impregnation. This study will provide references for the electromagnetic and mechanical properties of IBS tapes under ultra-high magnetic fields and contribute to the future development of higher-performance practical IBS coils.

Measurement and analysis of winding stresses in dry-wound pancake coils considering nonlinear compressive behaviors

Considering coil stress management, conductor thermal stability, and susceptibility to delamination, the dry-winding approach has been gradually applied and tested in high-temperature-superconducting coils wound with REBa2Cu3O (REBCO) coated conductors (CCs). In dry-wound coils, the winding tension can be a useful tool for managing the mechanical stresses and maintaining the structural stability. It is also related to the contact resistivity characteristics of no-insulation and metal-as-insulation coils. In this paper, we present a study on the winding stresses in dry-wound pancake coils considering nonlinear compressive behaviors in the radial direction. Coils wound with stainless-steel (SS) tapes and REBCO CCs were prepared, respectively, with various sizes (90–140 turns) and winding tensions (26–61 MPa). The radial pressure was obtained by applying the pressure measurement films, which cover a pressure range up to 50 MPa. A relatively moderate radial pressure buildup was observed in coils wound with SS tapes, indicating that the effective radial modulus of the coil as an entity is considerably lower compared to the tensile modulus in the azimuthal direction. This is consistent with the nonlinear stress–strain relationship of stacked thin sheets under transverse compression, which can be further explained by the contact behaviors between two rough surfaces. The average radial pressure in CC coils shared similar characteristics as that in SS coils, whereas the radial stress along the conductor edges were significantly higher compared to the middle. Cross-sectional microscopy of the CCs suggests that this can be primarily attributed to the thickness variations across the conductor width. These results suggest that the microscopic rough-surface contact and thickness variation of the wound tape play a critical role in the coil stiffness as well as the winding stress distributions.

Electro-Thermal Behavior of Layer-Wound BSCCO Coils With and Without Insulation

In this work, the electro-thermal behavior of two layer-wound High Temperature Superconducting (HTS) coils, realized with and without electrical insulation, is compared. Both coils are wound from the same BSCCO tape, and have a very similar geometry, with the same number of turns and layers. A heat input is applied to both coils, by tuning the current supplied to resistive heaters realized through stainless steel tapes wound on the mandrel at the inner surface of both coils. The heaters are in contact with one full inner turn of the winding. The coils are cooled in a liquid nitrogen bath, and the heaters are supplied with a constant current. Then, the windings are charged until the tape critical current is exceeded, and the tests are repeated for different heat loads. The signals acquired through voltage taps, suitably soldered at the same locations in both windings, are compared at the same testing conditions. Finally, the electrical characteristic of the different layers of the coils is related to the temperature of the heater and of the various turns of the coil by means of a 1-D thermal model.

Effect of the SS304 coating layer on the electrical and thermal properties of REBCO commercial tape

The effect of the 304 stainless steel (SS)-coated layer on the electrical and thermal properties in the radial direction of REBCO commercial tape was systematically investigated. The single SS-coated layer significantly increased electrical resistivity and decreased thermal conductivity. In contrast, double SS tape demonstrated a lower electrical resistivity than the original commercial REBCO tape due to the clean procedure to remove the possible carbon and oxidation in the Cu layer. We found that the surface microhardness of the SS-coated REBCO tape, a previously neglected factor, could be one of the primary factors determining turn-to-turn electrical resistivity. The other possible factor could be interface heterogeneity. The different materials on both sides of the interface could bring apparent different electrical and thermal resistivity. This study provides a possible method to increase the turn-to-turn electrical resistivity of REBCO tape without increasing tape thickness, sacrificing the critical engineering current density.

Numerical Study on Thermal Stability of No-Insulation Coils Using a Three-Dimensional Finite-Element Model

No-insulation (NI) coils possessing maximized volume current and quench recovery ability have become one of the most promising technologies for high-field high-temperature superconducting windings. In this article, we constructed a complete 3-D finite element model incorporated with the circuit and heat modules that allows a detailed simulation on the transportation behaviors of the NI coils. Critical problems including the circulating and radial electro-magnetic transportation behaviors during the excitation process with different ramping rates; the thermal propagation in the overcurrent circumstance and related quench protection; and the effect of parallel winding of stainless steel tapes have been investigated using the newly proposed model. A detailed comparison of NI and metal-insulated coils on thermal stability and quench recovery ability with the presence of hot spots has been implemented. Such a 3-D model enables a close look at the electrical and magnetic field distribution, and predicts more accurate coil-parameters for the circuit model where detailed material properties can as well be included.

Evaluation of surface disinfection methods to inactivate the beta coronavirus Murine Hepatitis Virus

The list of EPA-approved disinfectants for coronavirus features many products for use on hard, non-porous materials. There are significantly fewer products registered for use on porous materials. Further, many common, high-touch surfaces fall in between non-porous materials such as glass and porous materials such as soft fabrics. The objective of this study was to assess the efficacy of selected commercially available disinfectant products against coronaviruses on common, high-touch surfaces. Four disinfectants (Clorox Total 360, Bleach solution, Vital Oxide, and Peroxide Multi-Surface Cleaner) were evaluated against Murine Hepatitis Virus A59 (MHV) as a surrogate coronavirus for SARS-CoV-2. MHV in cell culture medium was inoculated onto four materials: stainless steel, latex-painted drywall tape, Styrene Butadiene rubber (rubber), and bus seat fabric. Immediately (T0) or 2-hr (T2) post-inoculation, disinfectants were applied by trigger-pull or electrostatic sprayer and either held for recommended contact times (Spray only) or immediately wiped (Spray and Wipe). Recovered infectious MHV was quantified by median tissue culture infectious dose assay. Bleach solution, Clorox Total 360, and Vital Oxide were all effective (>3-log10 reduction or complete kill of infectious virus) with both the Spray Only and Spray and Wipe methods on stainless steel, rubber, and painted drywall tape when used at recommended contact times at both T0 and T2 hr. Multi-Surface Cleaner unexpectedly showed limited efficacy against MHV on stainless steel within the recommended contact time; however, it showed increased (2.3 times greater efficacy) when used in the Spray and Wipe method compared to Spray Only. The only products to achieve a 3-log10 reduction on fabric were Vital Oxide and Clorox Total 360; however, the efficacy of Vital Oxide against MHV on fabric was reduced to below 3-log10 when applied by an electrostatic sprayer compared to a trigger-pull sprayer. This study highlights the importance of considering the material, product, and application method when developing a disinfection strategy for coronaviruses on high-touch surfaces.

Full-Field Displacement Measurement Method of Metal-As-Insulation Pancake at Liquid Nitrogen Temperature

In situ measurement of metal-as-insulation (MI) high temperature superconductor (HTS) pancake deformation gives insight to its actual mechanical state. Measurement of hoop strain for inner / outer turn of MI pancake is usually made by strain gauges. This measurement is however local and faces electromagnetic compatibility (EMC) and thermal issues. Non-contact full-field displacement measurement is an interesting alternative solution. This technique is based on digital image correlation (DIC), which derives the displacement field in specified region of interest (ROI) by correlation between the deformed state image and the reference state image. In this article, we present a novel DIC experiment setup for displacement measurement of MI pancake in cryogenic cooling. The setup is validated by a cooling test of 304 stainless steel disc. Then, it is used for cooling test of MI pancake made of co-wound copper beryllium - 304 stainless steel tapes. Both tests are done at 80 K by conduction cooling using liquid nitrogen. Finally, experimental results are compared to numerical results obtained from an analytical formulation of the mechanical equilibrium using generalized plane strain assumption.

Controllable rectification on the irreversible strain limit of 2G HTS coated conductors

The second generation high-temperature superconducting coated conductors (CCs) have excellent electrical and mechanical properties, and are extensively used in superconducting devices such as fault current limiters, magnets and motors. During the operation of these superconducting devices, superconducting CCs inevitably bear the combination of electromagnetic force and thermal mismatch stress, resulting in straining of YBa2Cu3O7− δ (YBCO) layer along the tape length. It is well known that the strains of superconducting CCs cause degradation of critical current (I c). Generally, the irreversible strain limit () is used to characterize the phenomenon that I c of superconducting CCs degrades with axial strain. When the axial strain of superconducting CCs is less than , I c can be reversibly recovered by over 99% after being unloaded. Therefore, is a key parameter for the design and application of superconducting CC devices. For this reason, to carry out a practical engineering method for improving of superconducting CCs has become a challenge and aroused interests among researchers. This study is based on the idea of precompression. A 316LN stainless steel tape was pretensioned at 77 K to improve its elastic strain limit. Then, two superconducting CCs were soldered onto both surfaces of pretensioned stainless steel tape respectively. As a result, of the superconducting CCs can be controlled manually with different precompressions. Taking YBCO CCs produced by SuperPower Inc. as an example, the measurement results show that the of the YBCO CCs increased from 0.39% to 0.73%. Meanwhile, the thickness of the sample did not increase more than once.

Fault Current Characteristics of Parallel Stainless Steel & REBCO Tapes and a 6 kV/400 V HTS Transformer

In order to improve the ability of superconducting transformer on limiting fault current, the parallel stainless steel & REBCO tapes are used as the winding materials. Firstly, the critical current of an individual REBCO tape and the parallel stainless steel & REBCO tapes under fault current are measured experimentally to compare their ability of limiting fault current. Then the current distribution in the parallel stainless steel & REBCO tapes under different fault currents are simulated. Lastly, a 6 kV/400 V (120kVA) HTS transformer is designed, and the fault current characteristics of wingdings are simulated based on finite element method (FEM). Experimental and simulation results show that the parallel stainless steel tape can improve the current limiting performance of the windings, which is of important referential value for the design of HTS transformer.

Development of a Cryogen-Free Compact 3 T Superconducting Magnet for an Electromagnetic Property Measurement System

A cryogen-free portable 3 T high-temperature superconducting magnet for an electromagnetic property measurement system has been developed to serve as a user facility at the Korea Basic Science Institute. The metallic insulation method was adopted to reduce the charging delay without sacrificing the self-protecting feature. A genetic-algorithm-aided optimized design was carried out to minimize the superconducting tape consumption while satisfying several design constraints. After the design, the compact high-temperature superconducting magnet composed of eight double-pancake coil modules was wound with high-temperature superconducting tape and stainless steel tape, and integrated with a two-stage cryo-cooler. The 3 T magnet was successfully cooled to approximately 20 K with a cryo-cooler and reached the target field of 3 T without any problems. Long-term measurements and a range of other tests were also implemented to verity the performance of the magnet. Test results demonstrated the feasibility of a cryogen-free portable high-temperature superconducting magnet system for electromagnetic property measurement experiments.

Investigation on the Electrical Contact Resistance of Soldered Metal Insulation REBCO Coil

No-insulation (NI) winding techniques are widely used in fabricating thermally, mechanically, and electrically robust REBCO magnets. However, NI coils have disadvantages during charging operation, such as charging delay and heat loss due to leakage current. Leakage current can be reduced by increasing contact resistance. Metal-insulation (MI) winding methods are also used by co-winding high-resistive metal insulators between the winding turns of REBCO wires. Although the contact resistance of MI coils can be substantially increased, quantitative estimation of the magnet contact resistance is difficult owing to the dry-contact between the winding turns. Moreover, special care is needed during epoxy impregnation of MI or NI magnets owing to delamination problems induced by the epoxy layer between the winding turns. In this study, a soldered metal insulation (SMI) method is proposed to remove the drawbacks of the MI coil, such as the hardly predictable contact resistance and the delamination issue during conduction cooling applications. The SMI coils were wound using a tin-plated stainless-steel (SS) tape between the REBCO wires as in the MI coil and they were heated in a furnace to produce soldered contacts between winding turns. To investigate the electric characteristics, sudden discharge and charge/discharge experiments were conducted at 77 K. In this paper, the test coils were fabricated using the NI, MI, and SMI winding methods and the contact resistance of each coil was investigated. The results show that the SMI winding method can be used to create expected or controllable contact resistance.

First performance test of the iron-based superconducting racetrack coils at 10 T

Iron-based superconducting (IBS) racetrack coils were firstly fabricated by using 100-m 7-filamentary Ba1-xKxFe2As2 (Ba122) tapes at the Institute of High Energy Physics, Chinese Academy of Sciences (IHEP, CAS). The IBS tape was wound in parallel with stainless steel tape to withstand the high tensile hoop stress under high magnetic field. After the heat treatment, the coils were impregnated with epoxy resin. Then the IBS coils were tested in a low-temperature superconducting Common-Coil dipole magnet which provided a maximum background field of 10 T at 4.2 K. Most importantly, the best IBS racetrack coil quenched at 4.2 K and 10 T with an operating current of 65 A, which is still as high as 86.7% of critical current of the short sample at 10 T. The details of the fabrication process and performance test results were presented in this paper. The performance test demonstrated the IBS conductor is a promising candidate for the application of high field magnets especially for future high-energy accelerators.

Effects of stainless steel thickness and winding tension on electrical and thermal characteristics of metal insulation racetrack coils for 10-MW-class HTS wind generator

Experimental results on the electrical and thermal characteristics of GdBCO racetrack coils co-wound with stainless steel (SS) tapes of various thicknesses and winding tensions are presented in this paper. The SS thickness and winding tension are identified as the factors affecting the charging time and thermal stability of metal insulation (MI) coils. To verify these characteristics, three types of MI-SS racetrack coils were fabricated with various SS thicknesses and winding tensions: 100-μm SS thickness and 10-kgf winding tension; 100-μm SS thickness and 5-kgf winding tension; and 50-μm SS thickness and 10-kgf winding tension. Further, three MI-SS racetrack coils were characterized by sudden discharging, charging, and overcurrent tests. The sudden discharging and charging tests were performed in a steady state to investigate the decay time constant of the center magnetic field discharging the coils and the delay time of the magnetic field charging the test coils, respectively. To estimate the thermal stability of the three MI-SS coils, overcurrent tests were conducted in a transient state at 1.1 times the critical current (Ic) and 1.05 Ic. Based on the experimental results of three small-scale test coils, the total contact resistance between the layers of the test coils was calculated and applied to design a field winding using a second-generation high-temperature superconducting (HTS) tape for a 10-MW-class HTS generator used in an offshore wind turbine environment. Subsequently, an equivalent electrical circuit model was proposed to analyze the electromagnetic response and thermal stability characteristics of three HTS field coils of a 10-MW-class HTS generator with the key parameters of the HTS field coils, which were obtained using electromagnetic finite-element analysis. Finally, the charging delay time and thermal stability of the three HTS field coils were compared and analyzed in detail.

Определение статического и динамического усилия для изготовления гофрированных лент для теплообменников аэродинамических труб

The article presents the results of an experimental study aimed at determining the required load when rolling a corrugated heat exchanger belt for wind tunnels. The experiments are carried out on a horizontal milling machine model 6H81. The results of the experiment are applied to stainless steel tapes with a thickness of 0,3 to 0,4 mm.

Preliminary Study on Different Winding Processes of ReBCO Coils

This article intends to explore the optimal electrical characteristics of different winding processes for future high-field accelerator magnet insert. In the study, five double-pancake (DPC) racetrack ReBCO coils were wound by dry winding with no insulation (NI) process, dry winding with Kapton insulation (KI) process, wet winding with KI process, wet winding with NI process, and dry winding cowound with stainless steel tape process, respectively. The five DPC racetrack coils were fabricated and tested at 77 K in the Institute of High Energy Physics, Chinese Academy of Sciences. The article mainly presented the two winding processes, dry winding with NI and cowind with 304 stainless steel tape insulation since their special self-protect character during quench and delay effects during excitation and demagnetization. Through the experiments, we studied the characteristics of different winding processes and quench protection methods, which are important for the future application of High-temperature superconducting (HTS) insert coils.

Design, construction and testing of parabolic solar cooker for rural households and refugee camp

This research paper demonstrates the importance of Parabolic Solar Cooker both for developing countries and for refugee camps. This cooker's main purpose was to concentrate the solar radiation and convert it to heat using different reflective materials. Some essential factors were considered as the surface of the reflector must be smooth and shiny, and control (loading, tracking, temperature sensing.) variables and uncontrolled (wind, ambient temperature) variables also need to consider. Several Parabolic Solar cookers had designed various reflective materials such as Stainless Steel, Aluminum Foil, and Mylar Tape. Additionally, multiple testing had done with those Parabolic Solar cookers. Besides, in this research three different forms of temperature were measured: Concentrating surface temperature, vessel temperature, and water temperature. The notable success of this research work was the third design. The third design was implemented with Mylar Tape as a reflective material. Boiled Rice, Fried egg and Fried potato had cooked within a short period with the third design. Firstly, stainless steel as a reflective material was used to construct the first prototype. Moreover, 58.2 °C maximum water temperature was achieved from the first prototype. After that, the second prototype was used aluminum foil as reflective material. Besides, 74.5 °C maximum water temperature was achieved from the second prototype. Finally, the third prototype was used Mylar tape as a reflective material. Alongside, 74.5 °C maximum water temperature was achieved from the third prototype. Moreover, in the wood we got 239 °C as well as in paper we got 105.4 °C.

Contact resistivity due to oxide layers between two REBCO tapes

In a no-insulation (NI) REBCO magnet, the turn-to-turn contact resistivity (ρc) determines its quench self-protection capability, charging delay time and the energy loss during field ramps. Therefore it is critically important to be able to control a range of ρc values suitable for various NI magnet coils. In this work, we investigate two possibilities to control ρc: by controlling the oxide layer of the copper surface of REBCO tapes; and by controlling the oxide layer in stainless steel co-wind tapes. We used a commercial oxidizing agent Ebonol® C to treat the copper surface of REBCO tapes. The copper oxide layer was characterized by cross-sectional transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). The oxide layer formed in Ebonol® C at 98 °C for 1 min is Cu2O of 0.5–1 μm. The ρc between two oxidized REBCO is in the order of 35 mΩ cm2 at 4.2 K which decreases to 10 mΩ cm2 after 30 000 contact pressure cycles. The ρc increases but only by 5% at 77 K. We also investigated the effect of oxidation of stainless steel co-wind tape on ρc. The native oxides on 316 stainless steel tape as well as those heated in air at 200 °C–600 °C were examined by TEM and XPS. The native oxides layer is about 3 nm thick. After heating at 300 °C for 8 min and 600 °C for 1 min, its thickness increases to about 10 and 30 nm respectively. For the stainless steel tapes with about 10 nm surface oxides, pressure cycling for 30 000 cycles decreases ρc by almost 4 orders of magnitude. Whereas at 77 K, it only decreases by a factor of 3. For a surface with 30 nm oxide, the ρc decreases moderately with load cycles. The results suggest that for an oxidized stainless steel to achieve stable ρc over large number of load cycles a relatively thick oxide film is needed.