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US 10,825,978 B2Granted
Strand critical current density in Nb3Sn superconducting strands via a novel heat treatment
AssigneeBruker OST LLC
InventorsMichael Field, Hanping Miao, Carlos Sanabria, Jeffrey Parrell
Life of this patent
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Abstract
A new heat treatment for Internal-Tin Nb3Sn strands is described. The heat treatment uses Nausite membranes to decrease the volume fraction of the η phase and therefore minimize its liquefaction—ultimately resulting in better connected Nb3Sn. The heat treatment requires only one stage aside from the final Nb3Sn reaction stage. This heat treatment enables an increase in critical current density (at 16 T) of 28%.
Claims6
A method for producing a high current density Nb3Sn superconducting wire comprising the steps of:
- a) fabricating a Cu clad internal tin Nb3Sn precursor wire containing Nb, Sn, Cu and a dopant of Ti and or Ta, drawn to an outer wire diameter between 0.2 mm and 2.0 mm, the precursor wire having a composition with an Nb fraction of 50-65% by area and an Sn fraction of 20-25% by area, with a Cu fraction representing the balance of the composition;
- and
- b) performing a heat treatment reaction wherein a Cu diffusion plateau between 350° C. and 380° C. is performed for 100 to 400 hours, thereby significantly reducing formation of (Nb0.75Cu0.25)Sn2 (“Nausite”), and a Nb3Sn reaction plateau is performed above 620° C. and below 750° C. for 24 to 400 hours.
Dependencies are inferred from the claim text.