Effect of nitrogen on supersolidus sintering of high speed steel

Abstract

We have developed high performance silver sheathed Bi2223 wire. The progress in three years is especially remarkable. This dramatic development has been made with the controlled overpressure (CT-OP) sintering technique. The CT-OP sintering technique improves not only the critical current but also other performances such as n-value and mechanical strength, because of the improvement of the relative density up to almost 100%, the homogenization of the Bi2223 phase and the stronger connectivity between the Bi2223 grains. The dense Bi2223 wire prevents the ballooning phenomenon which is caused by the gasification of the trapped liquid nitrogen during warming up to room temperature.Present critical current has reached as about twice high as that in those days and shows over 200 A (77 K, self-field), which showed an excellent critical current property in a magnetic field.