Improve Uniformity of the Cores and Je of Bi-2212 Wires

At low temperature and high field, Bi-2212 wires have the highest critical current density (Jc), and the isotropic round wires are more easily to design solenoid than the tapes. So the Bi-2212 wires are the preferred conductor for high-field solenoids. If the Jc of Bi-2212 wires was highest, the diameter of core of the wires was about 20 μm. It is so thin that some cores were broken by inhomogeneous force. So it was important for Bi-2212 wires to deform uniformly during the drawing. Effect of technological parameters on the Uniformity and the engineering critical current density (Je) were studied. The results showed that the reduction per pass affected the Uniformity and Je of Bi-2212 wires. If the reduction per pass was too small, there were only a local deformation and the unfavourable stress-strain distribution could found in the transverse section of the wires. When the reduction per pass was large enough, there was a synchronous deformation of each part of the wires. So the uniformity of sample with large reduction per pass was better than that of sample with small reduction per pass. Its Je value was also higher than that of sample with small reduction per pass with the same diameter and there were the higher maximum Je value for it. When it was the smaller diameter, the sample with large reduction per pass reached to the maximum Je. 20 percent of reduction per pass basically met the requirement of the synchronous deformation and high Je of Bi-2212 wires.