Processing method of high RRR value high purity niobium material and niobium material for RF superconducting cavity, including ingot forging, billet sazing, billet surface machining, billet pickling, billet heat treatment, billet opening, slab repair, pickling, slab rolling, finished product blanking, polishing, pickling, finished product heat treatment, finished product cutting and finishing polishing, finished product pickling step, through the processing method of the invention, The grain size of the finished sheet is maintained between 4.5 and 5.5 grades, and the uniformity is good. The mechanical properties meet the requirements, the transverse and longitudinal differences are controlled within 15%, the tensile and yield are controlled within 10%, and the elongation is controlled within 10%; The RRR value is controlled above 300; The content of gas elements can meet the requirements; Moreover, it improves the direct yield of the product, can greatly reduce the manufacturing cost of the manufacturer, and can be mass-produced.
Superconducting niobium plate (RRR≥300) is mainly used to make resonators for RF superconducting linear accelerators, and is the core component of accelerator engineering. Most of the resonators are pressure vessels, and the forming process involves pressure forming process, which requires more performance requirements for superconducting niobium plate.
The main disadvantages of the prior art are: the RRR of the finished sheet can not reach more than 300; The grain size is not uniform, there are large grain size; Gas elements can not meet the corresponding requirements; The transverse and longitudinal difference of mechanical properties is more than 10%, the strain hardening coefficient n < 0.3, and the direct yield of the product is low, basically about 50%.
The advantages of the technical scheme are as follows: (1) Through the reasonable forging process of the invention, the grains with a single grain size of more than 200mm are broken, and the radial direction performance of the ingot is improved and the isotropy is improved by square and round casting; The grain is fully broken again and the yield difference is increased by the large rolling rate of more than 90% between two anneals. Then the transverse and longitudinal properties are consistent and optimized by calculating the transverse working rate and the three commutation method. By heat treatment process, the speed and size of grain growth are controlled, and the grain is homogenized, the anisotropy is improved, the transverse and longitudinal differences in mechanical properties are reduced, and the gas element of the sheet is reduced by vacuum annealing, so that the RRR value is effectively increased. By controlling the surface treatment process, the hardened layer and pollutants on the surface of the plate are removed, the introduction of gas elements is greatly reduced, the RRR value is increased, and the surface hardness of the material is reduced to a certain extent; Through the control of auxiliary parameters, the introduction of gas elements is reduced and the RRR value is increased. It can be widely used to make resonators for RF superconducting linear accelerators.
