Study on Annealing Process of Large Size Copper Nickel Alloy Tube

The annealing process of copper nickel alloy seamless pipe was studied. Six typical copper nickel alloy seamless tubes were selected and produced by drawing. The annealing test was carried out according to the proposed annealing test scheme. After annealing, samples were taken for performance test. By testing tensile strength, yield strength and elongation, as well as Bush hardness and Rockwell hardness, and carrying out metallographic test, that whether the microstructure change from processed state to single-phase recrystallized α structure was observed. When the annealing temperature was less than or equal to 700 ℃, it was impossible to obtain single-phase α structure with complete recrystallization. When the annealing temperature was higher than 730 ℃, the grains would grow continuously. Annealing holding time less than or equal to 30 minutes could not achieve all recrystallization, and more than 40 minutes could make the grain continue to grow. The optimal annealing process for seamless copper nickel alloy pipe was holding at(720±10) ℃ for 40 minutes.