INVESTIGATION ON THE MANUFACTURING CONDIT IONS OF COMMERCIALLY PURE TITANIUM SEAMLESS PIPES BY THE INCLINED ROLLING PROCESS

The manufacturing conditions of commercially pure titanium seamless pi pes by inclined rolling process were investigated on laboratory scale. Elevated temperature torsion test was carried out to alpha forged and beta forged billets. Piercing condition was determined by a model pie rcing mill. A part of pierced shell was hot rolled and annealed to inv estigate the possibilities to attain equiaxed structure in the product s. The results were summarized as follows. (1)Piercing operation above 1223K is recommendable to avoid low piercing efficiency of the commer cially pure titanium. while the material possesses sufficient deformab ility in beta phase region. (2)Equiaxed structure is obtainable by the piercing operation in beta phase region, followed by rolling in alpha phase region and annealing at 1023K. Piercing operation below 1373K i s necessary to achieve equiaxed structure. (3)Fine grain alpha forged material possesses superior deformability at elevated temperature to c oarse grain beta forged material. However, the beta forged material po ssesses sufficient deformability for the piercing operation in beta ph ase region.