Stainless Steel Strands Research Articles

20 T Compact Superconducting Outsert Employing Y123 Coated Conductors for a 45 T Hybrid Magnet

We have been developing high-strength Nb3Sn strand cables to construct a high-field superconducting outsert for a 45 T hybrid magnet with a 25 T water-cooled resistive magnet. Evidence for cold work strengthening of repeated bending treatment (prebending effect) on Nb3Sn strands internally reinforced with CuNb stabilizer, which exhibits significant enhancement of the critical current density, has been found in the superconducting magnet fabrication process using a react-and-wind method. The strand cables were designed by controlling the constituent number of CuNb/Nb3Sn strands with the prebending effect and stainless steel strands, which are expected to have a stress limit 580 MPa at 0.4% strain. In order to design a compact superconducting outsert, high-strength strand cables are adopted in a magnetic field region below 14 T to maintain relatively large engineering current densities (Je). In a higher-field region above 14 T, YBa2Cu3O7 (Y123) coated conductors are employed for an insert coil. Using combination of Y123, Nb3Sn and NbTi superconductors, a 20 T superconducting outsert with a room temperature bore of 400 mm consisting of three layers made of Y123, two layers of CuNb/Nb3Sn and two layers of NbTi was designed. The coil parameters are 440 mm inner diameter, 1080 mm outer diameter and 1138 mm coil height. A very compact 20 T superconducting outsert with a stored magnetic energy 72 MJ at an operation current 903 A can be developed for a 45 T hybrid magnet.

Case Study of a 20 T-$\phi$400 mm Room Temperature Bore Superconducting Outsert for a 45 T Hybrid Magnet

The High Field Laboratory for Superconducting Materials (HFLSM) and the Tsukuba Magnet Laboratory (TML) conducted in collaboration a case study on development of a 50 T-class hybrid magnet. To construct a high magnetic field magnet with compact and energy-saving design as well as with easy operation and maintenance, one has to develop high-strength NbSn strand cables, with maximized superconducting characteristics and which can withstand a large electromagnetic force over 500 MPa. For this purpose, the HFLSM has proposed and investigated the effect of repeated bending treatment (pre bending) on NbSn strands internally reinforced with CuNb stabilizer leading to significant enhancement of the critical current density. In this report we present our results on application of the pre bending effect to the development of high-strength strand cables. The designed prebent-strand cables are composed of three CuNb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands (3 times Phi =1.73 mm) and four stainless steel strands ( 4 times Phi =1.73 mm). High-strength CuNb/Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand cables have shown a stress limit of 552 MPa at 0.4% strain, and a critical current of I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> =1000 A at 18.5 T and 2.0 K. For such high-strength strand cables, a 20 T superconducting magnet with a room temperature bore (Phi =400 mm) consisting of five layers made of CuNb/NbSn and two layers of NbTi was designed. The coil parameters are: inner diameter Phi = 440 mm, outer diameter Phi = 1332 mm, coil height 1321 mm, inductance 350 H and magnetic stored energy 144 MJ at 908 A of the operation current. Winding of the coil was experimentally successfully simulated using dummy 3 + 4 strands cable composed of three Cu strands and 4 stainless steel strands with a similar design to the 3 + 4 strands superconducting cable presented above. The 20 T superconducting coil will be used as a 20 T outsert for a 25 T water-cooled resistive insert to obtain a 45 T hybrid magnet.

The conductors of the 50 kA superconducting transformer for SSTF

The 50 kA transformer for Samsung Superconductor Test Facility (SSTF), which will charge the Korean Superconducting Tokamak Advanced Research cable-in-conduit conductor samples for 1 s is under design. The NbTi based conductors for primary and secondary windings are described. The primary winding conductor consists of six NbTi and six stainless steel strands cabled around rectangular copper core. Such a design was previously used by Kurchatov Institute in small SMES windings. The secondary winding conductor consists of 24 subcables wrapped around and soldered to a copper strip. Each subcable consists of six NbTi strands cabled around one copper strand. NbTi strands for both primary and secondary windings are 0.85 mm in diameter. NbTi wires have 8910 6-μm filaments. Both primary and secondary winding conductors have large current and temperature margins to ensure a reliable operation of the superconducting transformer.

The superconducting transformer of the Samsung Superconductor Test Facility (SSTF)

In the frames of designing the SSTF (Samsung Superconductor Test Facility) for the KSTAR (Korea Superconducting Tokamak Advanced Research), the 50 kA transformer charging a CICC (cable-in-conduit conductor) short sample for one second is now under design. The primary winding conductor consists of six NbTi and six stainless steel strands tabled around a low RRR rectangular copper core, which was used by Kurchatov Institute in small SMES (superconducting magnetic energy storage) windings. The secondary winding consists of 24 subcables wrapped around and soldered to a low RRR copper strip. Each subcable consists of six NbTi strands cabled around a copper strand. The strands for primary and secondary windings are 0.85 mm diameter NbTi wires with six micrometer 8910 filaments. Both primary and secondary conductors have large current and temperature margins to ensure a reliable operation of the superconducting transformer. The primary coil is placed in a cylindrical LHe vessel. The four secondary turns are glued to the outer surface of the LHe vessel. The joints between the transformer and the sample are described.

Development and test results of a double 0.5 MJ coil SMES system

The design and test results of a SMES system built for the Korea Electrical Power Company are described. The system consists mainly of two superconducting (SC) coils, two cryostats, a primary power supply and a DC-AC-DC power converter to transfer the stored energy from one coil to another and vice versa. Each of two almost identical coils can store more than 0.5 MJ at about 1.55 kA. Minimum energy transfer time is about 2 s. The conductor is made by cabling of several SC, copper and stainless steel strands around a copper core. At 2 s transfer time mode, the AC losses in each coil are about 500 J. The cryostats are manufactured mainly of thin-walled stainless steel. Their eddy current losses at liquid helium temperatures are lower than AC losses in the coils. After preliminary tests in Moscow, the system was delivered to Republic of Korea and successfully tested at Korea Electrotechnology Research Institute.

New temporary atrial and ventricular pacing leads for patients after cardiac operations

We have studied two new temporary pacing leads (Medtronic 6491 and 6492) intended for pacing after cardiac operations. The conductor has stainless steel strands coated with polyethylene connected to a 4 mm 2 surface area, stainless steel, smooth, tapered electrode. A soft 4-0 coiled polypropylene fiber served as a fixation mechanism in the heart. The study included 15 children (aged 3 months to 7 years, body weight 4.4 to 20 kg) with a variety of congenital heart defects and 15 adults (aged 45 to 78 years) with coronary artery disease ( n = 13) and aortic valve disease ( n = 2). A pair of leads each was placed in a bipolar fashion in the right atrial wall and nonsystemic ventricle in the children (median implant duration 12 days) and in the right atrial wall only in the adults (median implant duration 9 days). The atrial current threshold values in children increased from 0.61 ± 0.34 mA immediately after implant to 2.08 ± 1.86 mA at explant ( p < 0.002). In the adults the threshold values increased from 0.95 ± 1.44 mA immediately after implant to 2.76 ± 2.76 mA at explant ( p < 0.002). In the ventricle the threshold values increased from 0.38 ± 0.13 mA immediately after implant to 2.22 ± 1.63 mA at explant ( p < 0.002). Tissue resistance immediately after implant measured 809 ± 182 Ω in the atrium and increased to 820 ± 204 Ω at explant (children, p = not significant). Corresponding values in adults were 778 ± 190 Ω and 599 ± 91 Ω ( p < 0.004). In the ventricle resistances changed from 1019 ± 143 Ω to 876 ± 137 Ω ( p < 0.05). P wave amplitudes measured 1.8 ± 1.5 mV immediately after implant and decreased to 1.6 ± 1.2 mV at explant ( p = not significant, children) and 2.0 ± 1.3 mV to 1.8 ± 1.1 mV ( p = not significant, adults). R wave amplitudes were 13.1 ± 3.0 mV immediately after implant and fell to 8.7 ± 4.5 mV at explant ( p < 0.005). Thus threshold values, tissue resistances, and electrogram amplitudes assured a safe pacemaker function. The small diameter and pliable texture of these leads provided a smooth surgical handling. They were found particularly suitable in children. (J T HORAC C ARDIOVASC S URG 1995;110:1725-31)

Effect of composite structure on AC loss of superconducting wire

Investigations of quenching currents, stability and ac losses for two kinds of NbTi multifilamentary cable with very fine filaments are presented. Both of them comprise six strands of 0.1 mm diameter with many filaments of 0.5 μm dia. and a stainless steel strand of 0.1 mm diameter for reinforcement. These cables are epoxy-impregnated for practical windings. Even these designs result in good stability and low ac losses. If these cables are used in ac magnets, generating a maximum field of ac around 1.0 T, economical benefits are expected at power frequencies, 50 Hz/60 Hz.

オーステナイト系ステンレス PC 鋼線および鋼より線の開発

The effects of aging and stress-aging (called hot stretching) at the temperatures from 120°C to 700°C on the mechanical properties, relaxation values, Charpy impact values and SCC behavior of hard drawn SUS 304, SUS 316 stainless steel wires have been studied.The main results obtained are as follows:(1) Yield and tensile strength of the wires increased by aging at 230°C and 530°C as well as by hot stretching. The strengthening after 230°C treatment may be due to the strain aging by C and the increase of strength after 530°C treatment results from precipitation of Cr23C6 on dislocations.(2) Stress relaxation values up to 250°C are low due to precipitation of Cr23C6. Almost no difference can be observed between aging and hot stretching.(3) Impact value at -96°C of SUS 304 stainless steel wire which was measured with 1 mm V-notched specimen was found to be about the same as that of 9% Ni steel.(4) It is considered that in comparison with high carbon PC wire SUS 304 stainless steel showing high tensile strength is insensitive to SCC in NH4SCN and NH4NO3 solutions.(5) In practice, tension member of the austenitic stainless steel wire and strand which were produced by aging at 500°C may be useful in special industrial field, for example, (a) SUS 304, in cryogenic field use (b) SUS 316, in intensive magnetic field use as a nonmagnetic material.

Rigid Circumferential Constriction of the Arterial Wall: Part II

The distal thoracic aorta was partially occluded in 51 mongrel dogs. In some dogs single strands of size 00 Dacron, Teflon, and black silk were used, and in others the vessel was constricted by banding with a 2-cm long aluminum cylinder. In all instances the resultant diameter was 50% of the original diameter in systole. This study was performed as a sequel to similar experimentation reported by the authors in 1970 in which stainless steel mesh cylinders and single stainless steel strands were used. Because of unpromising results of earlier investigators—destructive changes of the vessel wall with fatal hemorrhage—we were surprised that all 86 dogs in our first study, and all 51 dogs in the current study, were alive and well at controlled intervals, some for up to 2 years.

An Evaluation of 55 Cobalt Substituted Nitinol Wire for Use in Orthodontics

The authors suggest that 55 cobalt substituted Nitinol wire be used in orthodontics by reason of its properties of elasticity and resistance to corrosion. The Nitinol wires are compared with single strand stainless steel and triple strand Twistflex wires. The authors suggest that 55 cobalt substituted Nitinol wire be used in orthodontics by reason of its properties of elasticity and resistance to corrosion. The Nitinol wires are compared with single strand stainless steel and triple strand Twistflex wires.