Investigation on the manufacturing condition Ti-6Al-4V seamless pipes by inclined rolling process

Manufacturing conditions for Ti-6Al-4V alloy seamless pipes by inclined rol ling process were investigated on laboratory scale. Elevated temperature to rsion tests and piercing tests were carried out on Ti-6Al-4V alloy ingot an d forged materials after various conditions. A portion of the pierced shell were hot rolled and annealed to predict microstructure and tensile propert ies of products by the inclined rolling process. The results were as follow s. (1) Grain size affects deformability at elevated temperatures. Material wit h finer grain size possesses higher deformability as well as wider temperat ure range of high deformability in alpha + beta temperature region. (2) The material forged in beta region with coarse grain size possesses suf ficient deformabilities for the piercing operation. There is no effect of t he forging conditions on tensile properties after piercing operation. (3) The microstructure on the final products consists of fine acicular stru cture and their tensile properties satisfy the specification for Ti-6Al-4V seamless pipes. (4) Piercing temperature at 1373K and reheating temperature at 1223K are re commended for the inclined rolling process to avoid formation of grain boun dary alpha phase which deteriorates ductility of the products.