Using the body-centered cubic crystal structure of niobium material and the excellent plastic characteristics of niobium material, the niobium slab is deformed by a rolling process with a large deformation rate of not less than 85% for each rolling process. Generally, the deformation process with a large deformation rate is rarely used in the processing of refractory metals. It greatly reduces the risk of introducing impurities and affecting the surface quality of niobium material in the multi-process rolling and intermediate processing process. On the other hand, the internal structure of the niobium slab is fully deformed through large deformation, which ensures the uniform organization of the finished wide plate barrier layer niobium sheet in the drawing process of preparing superconducting wire, and avoids excessive fracture due to the grain size range in the drawing process. Thus, the superconductivity and magnetic field of the large scientific device are not affected, and the gap of niobium tablets required for the domestic superconducting large scientific device is solved. At the same time, under the rolling process with a large deformation rate of not less than 85% for each rolling process, the internal structure of the niobium slab is deeply deformed. The method of vacuum annealing heat treatment is adopted after each rolling process, and the temperature of the vacuum annealing heat treatment is controlled to be 750℃ ~ 830℃, and the time is 1h ~ 1.5h. The grains with deep deformation are recovered and completely recrystallized, forming uniform microstructure, avoiding the phenomenon of partial grain growth caused by high temperature annealing in the prior art, affecting the uniformity of the structure, and then causing the fracture of the superconducting wire in the process of wire drawing, and finally obtaining a wide plate barrier layer niobium sheet with good surface quality, small average grain size and uniformity.
The preparation method of a wide plate barrier layer niobium sheet for superconducting wire is characterized in that the equipment used for the first rolling process in step 1 is 800mm four-high reversible hot rolling mill; The equipment used for the second rolling process in step 2 is 800mm UCM cold rolling mill. As a typical rare metal material with high melting point, niobium and niobium alloys have high temperature tensile strength equivalent to that of some steels at room temperature. Therefore, niobium and niobium alloy have much greater deformation resistance than other metal materials during hot rolling. In the process of deformation of niobium and niobium alloy in cold rolling, due to rapid work hardening, deformation resistance increases rapidly, rolling equipment carries huge compressive stress in the rolling deformation process, resulting in large elastic deformation and accelerated friction loss, which makes the rolled parts easy to produce uneven deformation, resulting in rolled parts edge cracking and different sizes. The optimized equipment has the advantages of high roll hardness, strong plate shape control ability and high dimensional accuracy, and can effectively realize the rolling with large deformation rate and the rolling effect is good.
