It is conducted in a vacuum furnace with a vacuum degree of 1 x 10-2 ~ 1 x 10-3 Pa. A thick, full-sized workpiece with a protective coating or foreskin allows rapid heat treatment in the atmosphere. Zircaloy tube stick in the middle of the annealing temperature about 700 ℃, recrystallization began about 500 ℃, 600 ℃ when the grain coarsening obviously. Finished pipes of eliminating stress annealing at 450 ~ 450 ℃, finished pipes of recrystallization annealing at 530 ~ 530 ℃.
The zircaloy last intermediate annealing heat instead to beta or alpha high temperature quenching, again after the final cold working and heat treatment for finished products finished pipe material, better corrosion resistance, the reason may be that the finished tube small scattered, the second phase of microstructure and alloy element is added in the alpha - Zr content of solid solution in the matrix. The operation of the reactor indicates that the zirconium tin alloy tube after the above heat treatment as the nuclear fuel element cladding tube can ease the furuncle corrosion of the fuel cladding in the operation of the reactor. But because of quenching furnace pipe manufacturing and cleaning the surface of the tube after quenching difficulties, semi-finished pipes quenching is not easy to implement in the industry, so the producers tend to just before or after forging extrusion, the massive blank or alpha beta phase of drier heated nasty cold treatment, although the effect of this treatment is a bit poor, but still corrosion resistance can be optimized.
Zirconium and niobium alloy is a heat treatment strengthened alloy, and the quench-cold processing aging treatment can also improve the corrosion resistance.
Before leaving the factory, the product performance inspection shall examine the chemical composition, corrosion performance, mechanical performance, surface quality, hydride orientation, metallographic organization, dimensional deviation, non-destructive inspection, etc., to ensure that the chemical composition and corrosion performance of the pipe bar are the same, and the mechanical performance indexes are similar. The thermal neutron capture cross section of zirconium material is very small, which is one of the excellent nuclear physical properties. The thermal neutron capture cross section of the zirconium tin alloy tube rod is not greater than 0.24b and that of the pure zirconium tube rod is not greater than 0.18b. In addition, the ability to resist irradiation growth is another nuclear physical characteristic of zirconium materials, which is not only related to reactor working condition, but also related to the amount of cold processing and crystal texture of zirconium materials.
Zircaloy tube rod should be sampled before leaving the factory, in 400 ℃ and 10.3 MPa steam 3 or 14 days corrosion test, and measure the weight should be less than 3 days 22 mg/dm2, weight should be less than 14 days 38 mg/dm2, generated on the surface of the black bright protective film. The mechanical properties of finished re-bonded zirconium tin alloy pipes are as follows: the strength limit at room temperature is equal to 413MPa, the yield strength is equal to 241MPa, the elongation is equal to 20%, and the mechanical properties of high-temperature strength and stress-relieving tube are determined by the agreement of the supplier and supplier. Zirconium and niobium alloy rods are ideal materials for pressurized water nuclear reactors, although they are slightly heavier and stronger than zirconium and tin alloy rods.
Test, zirconium and zirconium zircaloy, niobium alloy after corrosion test sample weight gain can usually be described by the empirical formula: Δ m = Ktn, or lg Δ m = K + NLGT, type of Δ m weight (mg/dm2); T stands for experimental time, K and n are specific coefficients.
