Site:           Vacuumschmelze (VAC)
                P.O. Box 23 53
                D-63450 Hanau, Germany
Date Visited:   11 June 1996
WTEC Attendees: R.D. Blaugher (report author), 
                D. Larbalestier
Host:           Dr. Helmut Krauth, Deputy Director, 
                   Vacuumschmelze GmbH Superconductor Division Gruener Weg 37

BACKGROUND AND CURRENT HTS RESEARCH AND DEVELOPMENT

Following the realization of Type II superconductors in 1962, Vacuumschmelze GmbH was one of the first companies to initiate, in 1966, the production of conventional low-temperature superconducting (LTS) wires such as Nb-Ti and Nb₃Sn. Vacuumschmelze (VAC) is currently the world's third leading manufacturer of conventional LTS wires, behind Intermagnetics General Corp. (IGC) and Oxford. Most of VAC's LTS production, much like that of IGC and Oxford, is for the MRI market. VAC is only interested in the SC wire or tape market, with no past and no expressed future interest in the fabrication of SC devices such as magnets, leads, etc. VAC, which is fully owned by Siemens, is nevertheless free to sell (or buy) wire from anyone. This "free market" ability would also apply to VAC's HTS conductor products. VAC has been active in HTS wire development since the initial HTS discovery in 1986. The HTS research at VAC, in fact, provided one of the major HTS wire achievements when Heine, Tenbrink, and Thoener published their results (1989) on powder-in-tube Bi-2212 wires that showed high current density of 1.5 x 10⁴ A/cm² at 4.2 K in a magnetic field of 26 T, which exceeded the performance of all LTS conductors at this magnetic field level. These results excited the SC community and precipitated the expansion of HTS wire development programs worldwide, particularly in the United States and Japan.

VAC is one of the world's leading producers of special metallic materials, with broad interests in a wide range of products beyond superconductivity. VAC, which started in 1923 to melt alloys under vacuum, has grown to have a product range of over 200 special alloys covering a large number of applications. VAC employs approximately 2,000 people and has an annual revenue of ~ DM 420 million ($300 million). The main works and head office for VAC is in Hanau, Germany, which is roughly 25 km from the Hauptbahnhof of Frankfurt. The superconductivity effort at VAC, which is also housed within the Hanau facility, involves approximately 60 people, principally in LTS manufacturing, with about 6 people devoted to HTS development. Dr. Helmut Krauth directs all of the superconductivity efforts at VAC. Superconductivity revenues for both LTS and HTS total around $15-20 million/yr., which represents 5-7% of VAC total sales.

Krauth was very clear on the ground rules for continued operation of the superconductivity effort at VAC: "It must operate in the black." In fact, due to previous poor years, it was heavily scrutinized by Siemens as to its future existence. Following this evaluation, the decision was made to continue the HTS operation in close cooperation with the research group at Erlangen. The Siemens HTS effort, which is ~3x larger than the VAC group, is currently providing support on Bi-2223 production, which will eventually be completely carried out at Hanau starting in late 1997. Siemens is providing support to VAC on sheath alloy development for improved ac losses and mechanical strength. At the time of the WTEC visit, VAC was expanding its facilities to accommodate the production of Bi-2223 tape at longer lengths of many km, up from the ~500 m lengths that it had been able to produce previously. VAC fabricates round Bi-2223 wire that is delivered to Siemens, where it is then rolled and heat-treated. The nominal long-length current density of the VAC/Siemens wire is above 2.0 x 10⁴ A/cm² at 77 K, H(0), with short lengths approximately a factor of two higher in J_c. VAC, in parallel with the Bi-2223 scale-up, will continue to produce Bi-2212 tape. The primary applications and market potential for the two bismuth compound conductors are as follows:

• Bi-2212 will be used for magnets operating at very high fields (10-25 T) in liquid helium, with a high field magnet market expected three to four years out
• Bi-2223 will be used for energy applications operating at higher temperatures

VAC management expects that the HTS market may develop in about 10 years, with transmission cables and transformers as the first major applications. HTS conductor will be needed near-term (2002) for transmission cable demonstrations. The high Ag content and high processing expense for the present PIT approach is a major cost driver, especially for the Bi-2223 conductor. A more practical conductor with less Ag is needed long term.

VAC has no current internal plans for processing or developing the other oxide materials. The YBCO coated conductor work, i.e., IBAD, etc., is being pursued at Siemens, which is emphasizing large area YBCO depositions for fault-current limiters. VAC, through Siemens, will follow this activity and when appropriate will enter the market. VAC similarly has no effort on Tl or Hg compounds and is depending on the German universities, such as Freyhardt's work at Gottingen, for input on the potential of these materials. The WTEC team's hosts at VAC stated that they wish to and intend to remain a major supplier of superconducting wire and tape in both the LTS and HTS markets. It should be possible for VAC to maintain this position with the continued interest and support from Siemens, which provides a unique relationship between an SC wire manufacturer and end user. The continued support of the German government (BMBF) is also important in maintaining the essential funding for HTS research at Siemens and in turn VAC. The major part of the HTS effort at VAC is performed within a BMBF-funded project lead by Siemens that includes VAC, FZK Karlsruhe, and IFW Dresden as the principal partners. Additional support on this program is also obtained from other German research institutions. The Bi-2223 tape for the Siemens (3,000 A) cable demonstration was supplied by VAC with assistance from IFW Dresden on some of the thermomechanical treatments.