Manufacturing method of Nb
Disclosed is a manufacturing method of an Nb 3 Sn superconductive wire using a powder technique, the method including the steps of: filling, as a raw powder, an intermetallic compound powder obtained from a metallic powder containing at least one metallic powder selected from Ta powder and Nb powder, and Sn powder, or a mixture of the metallic powder and the Sn powder into a sheath made of Nb or an Nb based alloy; performing a diameter-reduction process on the sheath to form a wire; heat treating the wire; and, forming a superconductive layer on the interface between the sheath and the powder, wherein at least one of the metallic powders selected from the Ta powder and the Nb powder is obtained by aggregating fine particles (primary) in shape of coral to form secondary particles.
1. A manufacturing method of an Nb 3 Sn superconductive wire using a powder technique, the method comprising the steps of:
reducing oxygen in primary particles of at least one of metallic powders selected from Ta powder and Nb powder using Na, Mg, or Ca;
aggregating the primary particles thereby obtaining secondary particles in a shape of coral;
filling, as a raw powder, an intermetallic compound powder obtained from said secondary particles and Sn powder, or a mixture of the secondary particles and the Sn powder, into a sheath made of Nb or an Nb based alloy;
performing a diameter-reduction process on the sheath to form a wire;
heat treating the wire; and
forming a superconductive layer on the interface between the sheath and the filled powder.
2. The method according to claim 1 , wherein an average particle size of primary particles of the at least one metallic powder selected from the Ta powder and the Nb powder is 20 μm or below.
3. The method according to claim 1 , wherein hydrogen concentration in the at least one metallic powder selected from the Ta powder and the Nb powder is 100 ppm or below, and oxygen concentration therein is 3000 ppm or below.
4. The method according to claim 1 , wherein oxygen concentration in the Sn powder is 2000 ppm or below.
5. The method according to claim 4 , wherein the Sn powder is obtained from an inert gas atomization method.
6. The method according to claim 1 , wherein the raw powder is isostatically pressed before being filled into the sheath.
7. The method according to claim 6 , wherein the raw powder before being isostatically pressed contains 5 mass % or more nonreactive Sn.
8. The method according to claim 1 , wherein the raw powder further contains Cu powder.
9. The method according to claim 8 , wherein the Sn powder is mixed with at least one metallic powder selected from the Ta powder and the Nb powder to prepare a Ta—Sn compound powder or an Nb—Sn compound powder, and Cu powder is added to the compound powder and filled into the sheath.