NbTi superconducting wires are used to conduct high electric currents with virtually no dissipation loss, particularly in superconducting magnetic coils for generating strong magnetic fields. In this case, NbTi has the advantage of favorable ductility, which facilitates processing of the material; for example, favorable plastic deformation is possible.
The current-carrying capacity of an NbTi superconducting wire can be improved by means of artificial pinning centers in the superconducting material that hold the magnetic flux tubes in place.
A frequently used method of incorporating pinning centers into NbTi material uses a succession of heat treatments and tensile deformations (“rod and wire drawing”). This results in depositions at the NbTi grain boundaries of α-Ti that act as pinning centers. Furthermore, the method is known for incorporating filaments of a transition metal (such as niobium, titanium, or vanadium) into an NbTi matrix, which act as artificial pinning centers. The method has also become known for assembling niobium and titanium in alternating layers into a blank, drawing the blank, and then bundling it into a second blank. The second blank is subjected to the hot isostatic pressing (HIP) process, extruded, and formed into a wire. NbTi is produced at the interfaces of Ti and Nb, but a normally conductive material is left over because of the insufficient reaction. The method is also known for enclosing stacks of alternating Nb layers and Ti layers in Nb and inserting them into a copper extrusion sleeve. After the HIP process, extrusion, and drawing, the extrusion sleeve is removed and the obtained filaments are stacked. After this, they are again introduced into a Cu extrusion sleeve, subjected to a HIP process, extruded, and drawn, the extrusion sleeve is removed, and the filaments are again stacked and surrounded with Nb. By again carrying out insertion into a Cu extrusion sleeve, a HIP process, extruding, and drawing, a finished NbTi-containing wire is finally obtained. These methods are summarized for example in U.S. Pat. No. 5,223,348.
The introduction of pinning centers into a NbTi superconducting material by known methods is complex and difficult. A highly precise process is required for deposition of α-titanium. Complex mechanical combination steps are required for inserting other materials into a NbTi matrix; the same applies to the combination of alternating layers of Nb and Ti.
In order to produce metallic components based on CAD data, the method has become known for producing the component in layers by local melting of a metal powder with a laser beam or electron beam (“selective laser melting” or “selective electron beam melting”), for example, the web page http://netzkonstrukteur.de/fertigungstechnik/3d-druck/selektives-laserschmelzen/, or the web page http://netzkonstrukteur.de/fertigungstechnik/3d-druck/selektives-elektronenstrahlschmelzen/. This production method requires no negative molds and allows undercuts.