Zirconium and zirconium alloy plastic good, can be made into tube, plate, rod and wire, which tube for the main products. The processing of zirconium and zirconium alloys depends on the basic properties of zirconium and the special requirements of zirconium components for nuclear reactors. The basic properties of zirconium are: easy to be polluted by oxygen, nitrogen, hydrogen and so on, easy to stick to the mold, there are homogenous and heterocrystalline transformation. The requirements for zirconium components in nuclear reactors are high dimensional accuracy, strict microstructure requirements and stable performance. The most widely used seamless zirconium tube processing process is: preparation of consumable electrode, casting, forging, hot extrusion (tube billet), cold processing, finishing.
Vacuum consumable arc smelting is the most popular method for the production of zirconium and zirconium alloys. High quality ingot can only be obtained by proper alloying method, proper proportion of new and old materials and reasonable casting system.
Ingot billet opening is generally carried out in the zone of phase, which is beneficial to deformation and reduces the segregation of alloying elements. The secondary forging temperature is lower than the opening temperature. The pure zirconium and zr-2 alloy are forged in the high temperature zone of the main phase zone, and the zr-2.5nb alloy is forged in the phase zone of (1 + 2). The final forging temperature shall not be lower than 700℃. The hot rolling temperature is similar to the secondary forging temperature, and the extrusion temperature is lower. To prevent oxidation and adhesion, billets are coated with copper or coated with glass before extrusion. Pure zirconium still has good plasticity at liquid nitrogen temperature. When rolling at room temperature, the cold working capacity between two annealing can reach 40% or more. The cold processing system before the finished product has important influence on the quality and performance of zirconium - tin alloy pipes. In order to obtain the pipe with good comprehensive performance, the total compression ratio of cold rolling before the finished product should be more than 50%.
T-zr with dense hexagonal structure at room temperature is easy to form texture in cold deformation processing. The texture of zirconium tube has important influence on its strength, creep property, hydride orientation and irradiation growth. The zr-4 alloy cladding tubes used in reactors usually require a near-radial base texture (that is, the c-axis of the hexagonal lattice is essentially parallel to the diameter of the tube). In general, the texture orientation can be obtained easily when the ratio of wall thickness reduction to diameter shrinkage in the final cold working process is greater than 1. In the production of zr-2.5 Nb pressure tube, the extrusion process parameters and the blank organization are controlled to control the texture. The flake hydride in zr-2.5 Nb alloy is randomly oriented, and the flake hydride can be tangentially distributed to obtain the desired texture by controlling the pressure tube process. After recrystallization annealing (approx. 650℃), the texture of cold-processed materials changes and the hydride orientation becomes chaotic (see preferred orientation).
