Proceedings of PAC09, Vancouver, BC, Canada TU6PFP001 PRODUCTION OF HIGH-PURITY-NIOBIUM UNDER INDUSTRIAL SCALE FOR UPCOMING LINEAR COLLIDER PROJECTS R. Grill , PLANSEE SE, Reutte, Austria W. Simader, PLANSEE Metall GmbH, Reutte, Austria B. Spaniol, W. Feuring, W. C. Heraeus GmbH, Hanau, Germany Abstract material requirements. For RRR-Niobium sheet material Sheet, tubes and formed parts made of high-purity in December 2007 the PLANSEE Metall GmbH was Niobium with a high residual resistivity ratio (RRR- successful qualified as supplier for RRR-Niobium sheets Niobium) is the key component for future linear [4,5]. Both companies are now joining their competencies accelerators based on the superconducting radio- in the field of RRR-Niobium - from the electron beam frequency technology. To be prepared for large production melting, the processing into semi-finished products by use scale quantities, which are demanded for the upcoming of advanced manufacturing technologies and numerous projects like XFEL and ILC respectively, W. C. Heraeus analytical capabilities – to offer a complete product and GmbH (D) and PLANSEE Metall GmbH (A) joined their technology package for the accelerator industry. competencies in the field of RRR-Niobium. In 2007 the qualification procedure as material supplier for the XFEL MELTING project could be successfully finished and a complete Production of RRR-Niobium starts with standard product and technology package for products made of Niobium ingots melted by electron beam or electro-arc- RRR-Niobium was established. melting. The further refining is done by electron beam Based on the combination of the high expertise and melting where Niobium is purified in a vacuum at over long-term experience in electron beam melting of 2500 °C. In Fig. 1 the several reactions between the metal different RRR-Niobium qualities, the knowledge and and the gases, as well the reactions between the gases availability of various processing technologies for itself are shown [6]. In particular, Niobium reacts readily manufacturing of semi-finished and ready to assemble with Oxygen and Nitrogen wherever it gets the chance. components, and the unique analytical capabilities for Vacuum remelting and special conditioning technique advanced quality control along the process chain, during melting leads to Oxygen contrentations lower than customized product solutions can be realized for the 5 µg/g. With a crucible diameter of around 300 mm and a accelerator industry. Besides, a general overview about weight in the range of 1,4 tons a modern melting plant for the production capabilities available investigation production of RRR-Niobium is available at W. C. Heraeus methods for characterization and quality assurance of GmbH. RRR-Niobium large production scale quantities will be discussed. INTRODUCTION In 2007, at the German Electron Synchrotron (DESY) in Hamburg the starting signal was given for the construction of XFEL (X-ray free electron laser). For the heart of the linear accelerator high purity niobium, so called RRR-Niobium grade, will be used for the cavity resonators [1]. In preparation of this cutting edge Figure 1: Metal-gas and gas-gas reactions during international project W. C. Heraeus GmbH (D) and Niobium refining. PLANSEE Metall GmbH (A) started in 2004 a project to bundle the competencies of both companies on RRR- Niobium. PRODUCTS AND COMPONENTS W. C. Heraeus GmbH (part of the Heraeus group) is Starting material are melted blocks with a typical working since many years on RRR-Niobium and is diameter of around 300 mm and a length between 800 and worldwide supplying research laboratories with melt- 2000 mm. Forging is the first step for refining the as-cast ingots and semi-finished products and components for grain structure and setting up the proper shape for further cavity resonators [2]. PLANSEE Metall GmbH (part of processing. After surface conditioning subsequent rolling the PLANSEE group) is specialized in manufacturing of for sheet production or forging and drawing respectively products made of Molybdenum, Tungsten, Tantalum, for production of rods or tubes is applied. Niobium and Chromium [3]. Based on available Due to the wide range of available production equipment PLANSEE Metall GmbH set up a production equipment within both companies semi-finished products line for RRR-Niobium to allow the manufacturing of semi in various geometries and sizes such as sheets, plates, finished products and components according to customer discs and seamless tubes are available. Further processing Applications of Accelerators T27 - Industrial Collaboration 1287 TU6PFP001 Proceedings of PAC09, Vancouver, BC, Canada on the basis of machining and chipless forming allows the nevertheless also metallic elements, especially those with supply of RF cavity components and supporting parts higher melting points as Niobium (e.g. Ta, W), must be ready to assemble such as HOM-coupler, housings, end- controlled very careful over the whole supply and tubes and flanges. In Fig. 2 the production steps for the production chain due to thermal stability and increase of manufacture of RRR-Niobium products and components concentration during purification by melting [6,7,8]. are given. In order to ensure product quality along the process chain, all the RRR-Niobium output passes through advanced quality control procedures including chemical analysis, characterization of mechanical properties and RRR measurement repeatably. Niobium - Prematerial several Electron Beam Melting repetitions Forging Surface Conditioning Cutting Figure 3: RRR value for Niobium as function of the Sheet Rolling Rotary Forging interstitial solved gases Oxygen and Nitrogen. In order to maintain the high purity level over the Roller Levelling Drawing whole production route the parameters for deformation, heat treatment and machining must be well defined and Grinding Machining controlled to prevent reaction with the atmospheric gases. Pickling Pickling Furthermore, due to the mechanical softness of the material and the cold welding tendency of Niobium a Heat Treatment Heat Treatment careful handling during processing is mendatory to prevent surface defects or surface contaminations. Quality Control Quality Control Spot like concentrations of interstitially disolved gases or metallic impurities, small defects in the microstructure or scratches or inclusion of foreign material in the surface RRR-Niobium sheet RRR-Niobium components can lead to problems in the performance of the cavity (fine grained) (coupler, tubes, flanges, housings) resonator. Therefore, analytical techniques with high Figure 2: Production steps for manufacturing of RRR- detection sensitivity are applied for characterization and Niobium products and components. quality assurance of RRR-Niobium. In both companies advanced quality control procedures were established and For sheet manufacturing the parameters for rolling and used for characterization and quality assurance of heat treatment are critical for production of fine grained industrial RRR-Niobium production as listed below sheet with equiaxed material properties meeting customer [9,10]. specification. For production of large scale quantities of Gas analysis in solid materials: RRR-Niobium sheet a rolling mill with useable width of • Trace determination of of C, O, H, N and S in the 800 mm and a high vacuum annealing furnace with a bulk by fusion extraction using the platinum flux useable length of about 3000 mm at PLANSEE Metall technique. GmbH are available. • Determination of moisture and carbon on the Final conditioning operations for sheet manufacturing surface. like e.g. roller levelling, grinding and pickling according Physical properties: to costumer specification can be made on fully automized • equipment. RRR measurement (according established standard for XFEL). • Determination of thermal conductivity and thermal QUALITY ASSURANCE expansion coefficient. RRR values of 300 and higher are achieved by marked • Measurement of heat capacity. reduction in the contents of interstitially dissolved non- Mechanical and non-destructive testing methods: metal element impurities by several electron-beam- • Tensile strength, bending strength and hardness melting refining steps. Mainly the content of the tests. interstitially disolved elements Oxygen and Nitrogen have • Determination of strain hardening coefficient and a strong influence on the RRR value (Fig. 3). But plastic strain ratio. Applications of Accelerators 1288 T27 - Industrial Collaboration Proceedings of PAC09, Vancouver, BC, Canada TU6PFP001 • Ultrasonic testing. industrial production of semi-finished products and • SQUID (eddy current testing with superconducting components made of RRR-Niobium. magnetic field sensors). • USM (ultrasonic microscopy for determination of REFERENCES volumetric defects). [1] R. Brinkmann, “The European XFEL SC Linac Metallographic analysis: Project”, LINAC 08, Victoria BC, September 2008, • Qualitative and quantitative microstructure analysis. MO102, p.6 (2008); http://www.JACoW.org • Micro hardness and low-load hardness tests. [2] W. C. Heraeus GmbH, D-63450 Hanau, Germany; • High resolution electron scanning microscopy. www.wc-heraeus.com/special-metals-technology • EBSD analysis for determination of crystallographic [3] PLANSEE Metall GmbH, A-6600 Reutte, Austria; orientation and micro-texture. www.plansee.com Surface analysis: [4] A. Brinkmann rt al., “Progress of the test cavity • EDX/WDX analysis by use of scanning electron program for the European XFEL”, SRF