Capacitor-grade lead wires with increased tensile strength and hardness
View Patent ↗A capacitor-grade wire made from powder metallurgy containing at least niobium and silicon, wherein the niobium is the highest weight percent metal present in the niobium wire. The wire having a controlled tensile strength at finish diameter exceeds the strength of capacitor-grade wire formed by ingot metallurgy. Also, the powder metallurgy wire hardness exceeds capacitor-grade wire formed from ingot metallurgy with electrical leakage meeting the specifications normally applied to capacitor grade tantalum, niobium or niobium-zirconium lead wire at sinter temperatures of about 1150° C. and above.
1. A process for making a silicone-doped niobium lead wire comprising:
(a) forming a low oxygen niobium powder by hydriding a niobium ingot or a niobium bar and grinding or milling the ingot or the bar, and thereby making a powder having a Fisher Average Particle Diameter particle size range of less than 150 microns;
(b) (i) dehydriding the niobium powder, and
(ii) deoxidating the dehydrided niobium powder thereby forming a low oxygen niobium powder;
(c) blending the low oxygen niobium powder with a silicon additive powder, and compacting the powder blend of low oxygen niobium powder and silicon additive powder by cold isotactic pressing to form a bar;
(d) thermomechanically processing the bar into a rod; and
(e) subjecting the rod to the following sequential steps,
(i) annealing at a temperature of about 2500° F. for 1.5 hours,
(ii) rolling to a diameter of about 0.440 inches,
(iii) annealing at a temperature of about 2500° F. for 1.5 hours
(iv) reducing to a diameter of about 0.1 inches, and
(v) drawing to a wire having a diameter of at least about 0.005 inches.
2. The process of claim 1 , wherein the silicon is added in an amount that is less than about 600 ppm.
3. The process of claim 1 , wherein the silicon is added in an amount ranging from about 150 to about 300 ppm.
4. The process of claim 1 , wherein the wire further comprises a metal component selected from the group consisting of tantalum, zirconium, titanium, and combinations thereof.
5. The process of claim 1 , wherein the niobium powder has an oxygen level that is below about 400 ppm.
6. The process of claim 1 , wherein the wire has a tensile strength exceeding capacitor-grade niobium wire and niobium-zirconium alloys derived directly from ingot metallurgy.
7. The process of claim 1 wherein the niobium powder has an oxygen level of less than 200 ppm.