Search

For the past couple decades, 316LN stainless steel has remained the "go-to" alloy for structural components intended for cryogenic temperature service, partially because of its favorable mechanical properties, but also because of the data available in the literature for T = 4 K. In recent years, some interest has arisen to investigate and develop stronger and tougher alloys for cryogenic structural components, particularly for magnet systems like ITER. This study presents new 4 K fatigue crack growth rate (FCGR) and fracture toughness data for Nitronic® 50 and JK2LB stainless steels, compiles existing data for these alloys, and compares them with 316LN data found in literature. This study intends to further expand the existing cryogenic data set for these alloys, clarify key differences between them to better facilitate mechanical design, and potentially bolster further alloy development.

The tie plate structure for the ITER Central Solenoid (CS) is required to have high strength and good fatigue and fracture behavior at both room temperature and 4 K. A super-austenitic stainless steel - UNS 20910, commonly referred to by its trade name, Nitronic 50 (N50) - has been chosen for consideration to fulfill this task, due to its good room temperature and cryogenic yield strengths and weldability. Although N50 is often considered for cryogenic applications, little published data exists at 4 K. Here, a full series of tests have been conducted at 295 K and 4 K, and static tensile properties of four forgings of commercially-available N50 are reported along with fatigue life, fatigue crack growth rate (FCGR), and fracture toughness data. This study makes a significant contribution to the cryogenic mechanical properties database of high strength, paramagnetic alloys with potential for superconducting magnet applications.

The result of a Nitronic 50 (N50) weld-screening program conducted in support of CS-Tie Plate Structure Design and Development is reported here. The goal of this program is to evaluate four different weld practices and to select the best weld practice for thick section welding of the N50 tie plate structure. The structure design specifies both the weld and base metals have the same minimum mechanical properties requirements. The criteria for selecting the best weld practice are based on the combination of the 295 K tensile properties and the 4 K-tensile, fatigue, and fracture-toughness properties.

In cable-in-conduit conductor (CICC) magnets, such as the ITER TF coils, the conduit is the primary structural component. This function creates requirements for 4 K strength, toughness, fatigue crack resistance, and ductility after exposure to the superconductor's reaction heat treatment. The tensile ductility of a steel is a quality factor related to fatigue and fracture resistance that can be evaluated more economically with tensile tests rather than fatigue and fracture tests. Here we subject 316LN modified base metal and welds to a range of cold work from 0% to 20% and a subsequent Nb3Sn reaction heat treatment to evaluate the effects on the tensile properties. With the addition of cold work, the 4 K yield strength increases while tensile elongation decreases in both the base metal and weld. The results are compared to previously published data on the same alloy to evaluate the use of tensile ductility parameters as a materials qualification specification in magnet design.

Multifilamentary Ag-sheathed Bi2Sr2CaCu2Ox (Bi-2212) wire can carry sufficient critical current density Jc for the development of powerful superconducting magnets. However, the range of its applications is limited by the low mechanical strength of the Ag/Bi-2212 strand. A potential solution is to cable Ag/Bi-2212 wire with high-strength materials that are compatible with the Bi-2212 heat treatment in an oxygen atmosphere. Past attempts have not always been successful, because the high-strength materials reacted with Bi-2212 wires, significantly reducing their Jc. We examined the nature of reactions occurring when Ag/Bi-2212 wires are heat-treated in direct contact with several commonly used high-strength alloys and a new Fe-Cr-Al alloy. INCONEL X750 and INCONEL 600 resulted in significant Jc loss, whereas Ni80-Cr caused little or no Jc loss; however, all of them formed chromium oxide that subsequently reacted with silver, creating cracks in the silver sheath. We found that Fe-Cr-Al did not show significant reactions with Ag/Bi-2212 strands. Scanning electron microscopy (SEM) and energy dispersive x-ray (EDS) examinations revealed that the Fe-Cr-Al alloy benefits from the formation of a uniform, crack-free, continuous alumina layer on its surface that does not react with Ag and that helps minimize the Cu loss found with INCONEL X750 and INCONEL 600. We fabricated prototype 6-around-1 cables with six Bi-2212 strands twisted and transposed around an Fe-Cr-Al alloy core coated with TiO2. After standard 1 bar melt processing, the cable retained 100% of the total current-carrying capability of its strands, and, after a 10 bar overpressure processing, the cable reached a total current of 1025 A at 4.2 K and 10 T. Tensile tests showed that Fe-Cr-Al becomes brittle after being cooled to 4.2 K, whereas INCONEL X750 remains ductile and retains a modulus of 183 GPa. We proposed new cable designs that take advantage of the chemical compatibility of Fe-Cr-Al and high strength of INCONEL X750 for various high-field magnet applications.

The performance of Nb3Sn composite superconducting wire is highly dependent on its strain state, which is difficult to predict or measure accurately. There is limited data in the literature on Nb3Sn or conduit alloys for the thermal expansion/contraction that occurs during reaction heat treatments. Thermal expansion measurements of two contemporary Nb3Sn wires and two conduit alloys-316LN and JK2LB-are taken individually during reaction heat treatments in a wide temperature range (4-1200 K) dilatometer system at the NHMFL. The measurements observed here are compared with the existing data and predicted models. This work significantly increases the available data for Nb3Sn superconductors and conduit alloys that can be used in magnet design and predictive modeling.

Insulation in a high field superconducting magnet plays a critical role. For high field magnets using coated conductor, insulation faces a few special challenges. In order to maximize the engineering current density, the conductor insulation has to be very thin (e.g.

In the late 1950s the aerodynamicists at what is now the Hatfield site of British Aerospace accepted the challenge and met British European Airways’ demand for a 600 m. p. h. ( ca . 966 km h -1 ) short-haul jet airliner (the Trident). The experience and organization resulting from that project was the cornerstone on which the subsequent success story of civil wing design has been built. The substantial advances in efficiency achieved by the Hatfield team in the following designs for the 125 Business Jet, the 146 Feederliner and for the Airbus Industrie family of Wide-Body Mainline aircraft, has been supported by research programmes in the government establishments and universities as well as industry itself. Each project had its individual demands for fuel economy, high lift capability and structural efficiency, with commercial competition continually driving technological progress. The major highlights and achievements of the aerodynamic development programmes for these projects are reviewed. Turning to the present, the Hatfield team are currently working on the aerodynamic design for the combined Airbus A330/340 project. Technological progress continues apace with major investment in computational fluid mechanics, but the still essential role of experimental test techniques and facilities is emphasized.

The A300B, otherwise known as the European Airbus, is an international collaborative project. Hawker Siddeley Aviation are under contract to Airbus Industrie to design and manufacture the wing. Manufacture is now well advanced, the first wing having been delivered to Toulouse in November 1971.In describing the aerodynamic development of the wing for this aircraft, it is necessary to describe events before the advent of the designation A300B, as the aerodynamic design philosophy was established prior to that date. In particular reference will be made to the preceding paper project the A300 and to a lesser extent to projects being considered before the opening of technical discussions between Sud Aviation, Deutsche Airbus, and Hawker Siddeley Aviation.