Method of producing superconducting niobium pipe. It is characterized by the following steps: taking cylindrical high-purity niobium ingots to drill holes to get hollow ingots, extruding the hollow ingots at room temperature to get tube billets, and then rolling the tube billets to get finished niobium tube. The invention adopts the pressure processing method of "positive extrusion at room temperature + pipe rolling" to realize the production of pure niobium pipe for superconducting accelerator. On the premise of simple process and no tooling, high purity niobium pipe with RRR value ≥300 can be processed. The invention adopts the positive extrusion method at room temperature to extrude the tube billet, and controls the temperature rise degree of the material in the extrusion process by controlling the extrusion speed, which can effectively avoid the serious loss of RRR value. The finished pipe with high dimensional precision and small ellipticity can be made by multi-roll pipe mill.
The key parameter for the superconducting performance of high-purity niobium tubes for superconducting accelerators is the RRR value (i.e., the residual resistivity of the material at 4.2K temperature), which is generally required to be greater than 300. The higher the RRR value, the better the superconducting performance of the tubes. The main factor affecting the superconducting performance of high-purity niobium pipe in processing is the temperature rise degree from ingot to finished product processing. The higher the temperature rise in processing, the more serious the RRR value attenuation. Therefore, the processing method is very important for the production of pure niobium pipe for superconducting acceleration.
Superconducting acceleration is used at present, the global production technology of pure niobium tube sheet welding method, the backward extrusion method, main forging deep reaming method and rafa four categories, but the following drawbacks: (1) sheet of plate straightness, welding technology and welding method roundness by such as the demand is higher, and need to ingot casting processing onto a plate for welding, production cycle is long; 2) The reverse extrusion method requires high precision for the extrusion equipment tooling and lubrication system, and the finished product needs machining, and the material utilization rate is low; 3) The forging and reaming method have the problems of low material utilization rate, slow production efficiency and high tooling cost. Moreover, the above four methods are difficult to make pipe with diameter below 9 50mm and wall thickness above 3mm. The purpose is to provide a method to produce superconducting niobium pipe, which can effectively avoid the serious loss of RRR value of niobium pipe material and significantly improve the material utilization and product processing efficiency.
