Zirconium and zirconium alloy have good plasticity, can be made of pipe, plate, bar and wire, of which the pipe is the main product. The processing process of zirconium and zirconium alloys depends on the basic properties of zirconium and the special requirements of nuclear reactors for zirconium components. The basic properties of zirconium are : easy to be polluted by oxygen, nitrogen, hydrogen and so on, easy to adhere to the mold, there is homogeneous heterocrystalline transformation. The requirements for zirconium components in nuclear reactors are high dimensional precision, strict microstructure and stable performance. The most widely used seamless zirconium tube processing main processes are: preparation of consumable electrode, melting casting, forging, hot extrusion (tube billet), cold processing, finishing.
Vacuum consumable arc smelting is the most common method for the industrial production of zirconium and zirconium alloys. High quality ingot can be obtained only by the correct method of adding alloying elements, the appropriate proportion of new and old materials and the reasonable melting casting system.
Ingot casting is generally carried out in the phase zone, which is conducive to deformation and reduces the segregation of alloy elements. The secondary forging temperature is lower than that of the blank. The pure zirconium and zr-2 alloy are forged in the high temperature region of the phase region, and the zr-2.5 Nb is forged in the phase region. The final forging temperature shall not be lower than 700℃.The temperature of hot rolling is close to that of secondary forging, and the temperature of extrusion is lower. To prevent oxidation and mold adhesion, the blank is coated with copper or glass before extrusion. Pure zirconium has good plasticity at liquid nitrogen temperature. At room temperature, the amount of cold working can reach 40% or higher between two annealing processes. The cold processing system before the finished product has an important effect on the quality and performance of zirconium alloy pipes. In order to obtain the tube with good comprehensive performance, the total compression rate of cold rolling should be more than 50%.
