PIERCING METHOD FOR MAKING SEAMLESS PIPE Russian patent published in 2007 - IPC B21B19/04 

FIELD: piercing processes for making seamless pipes.

SUBSTANCE: method comprises steps of providing feed angle β and interaxial angle γ of main rolls in range determined according to expressions: 8° ≤ β ≤20°; 15°≤ β + γ ≤ 50°; setting relation of outer diameter do of solid blank with outer diameter d and thickness t of wall of hollow rolled piece after piercing according to expression: 1.5 ≤ - Ψ_r/Ψ_θ≤ 4.5 where Ψ_r =ln(2 t/do) and Ψ_θ = ln{2(d - t)/do}; setting relation of inlet diameter D1 and outlet diameter D2 of main rolls with said do, d and γ according to expression: (d/do)/(0.75 + 0.025γ) ≤ D2/D1.

EFFECT: possibility for suppressing effects of rotary forging and excess shear deformation without excess narrowing of roll diameter.

3 cl, 6 dwg, 2 ex, 2 tbl