In recent years, high-temperature superconducting (HTS) technology has shown great potential in fields such as nuclear fusion devices, high-power motors, maglev transportation, and power grid transmission and distribution. As the carrier substrate for the superconducting coating—the HTS substrate tape—its material properties directly determine the crystalline quality of the superconducting layer and the critical current density. Currently, ultra-thin cold-rolled precision stainless steel strip has become one of the mainstream substrate materials due to its excellent mechanical strength, thermal stability, and cost advantages.

      Ideal superconducting substrate tapes must meet several special requirements: the thickness needs to be significantly reduced to lower AC losses; the surface roughness must reach a precision grade to ensure uniform deposition of subsequent oxide buffer layers; the chemical composition must be highly pure to prevent the diffusion of elements like Fe and Cr from contaminating the superconducting layer; and it must maintain dimensional stability during high-temperature processes in preparation, without warping or abnormal grain growth.

      These requirements pose specific challenges to the manufacturing process of stainless steel strip. Traditional cold rolling processes can easily introduce residual stress or surface scratches, while inadequate cleaning can leave behind oil residues or metal ions, affecting the adhesion of subsequent coatings. Therefore, every step from smelting and hot rolling to multi-pass cold rolling, electropolishing, high-purity cleaning, and oxygen-free annealing requires precise control.

      It is worth mentioning that the substrate tape also needs to possess a specific cube texture or have a template structure built through Ion Beam Assisted Deposition (IBAD), which imposes requirements on the grain orientation uniformity of the original strip. For this reason, an increasing number of superconducting projects are beginning to collaborate with material enterprises that have full-process control capabilities to jointly develop customized substrate tape solutions.