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AssigneeEdison S.P.A.
InventorsGiovanni Giunchi, Sergio Ceresara
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A method is described for the production of superconductive wires based on hollow filaments made of MgB2, which comprises: a) the formation of a composite billet by means of the coaxial insertion in a tubular metallic container of a cylindrical bar made of metallic magnesium and amorphous boron powder in the interspace between the container and bar, said powder being pressed between the metallic container and the magnesium bar, in such a quantity that the weight ratio magnesium/boron is higher than 1.2; b) at least one plastic deformation treatment of the composite billet thus obtained until a wire with a pre-fixed diameter is obtained, with the subsequent winding of the wire onto a support; c) a thermal treatment of the filament product thus obtained, at a temperature ranging from 700° C. to 950° C. for a time ranging from 15 minutes to three hours.
A method for the production of superconductor wires based on hollow filaments made of MgB2, which comprises:
The method according to any of the previous claims, characterized in that the tubular metallic container consists of steel with a low carbon content, i.e. with a carbon content lower than 0.2% by weight, or Cu or one of its alloys containing Ni, or different layers of the above metals.
The method according to any of the claims from 2 to 9, characterized in that the Nb sheath consists of a tube or a sheet rolled up various times, having a total thickness, s, linked to the internal diameter of the metallic container, dc, according to the relation:
The method according to any of the claims from 1 to 9, characterized in that the metallic magnesium bar is a cylindrical solid pure magnesium bar (<99%), with a diameter, dMg, within the range:
The method according to any of the claims from 1 to 9, characterized in that the non-crystalline boron powder has a purity ≧95% (excluding the possible presence of metallic Mg) and a particle-size with an average diameter of less than 20 micrometers.
The method according to any of the claims from 1 to 9, characterized in that the quantity of boron powder inserted in the interspace is at least that corresponding to a vertical gravitational filling, assisted by vibrations and manual pressure applied with a tube which can be inserted in the interspace, with a final weight ratio between Mg and B ranging from 1.20 to 1.60.
The method according to any of the claims from 1 to 9, characterized in that the plastic deformation treatment is selected from extrusion, drawing, swaging or rolling.
Dependencies are inferred from the claim text.