METHOD OF CALIBRATION OF TUBULAR ARTICLES Russian patent published in 2005 - IPC

FIELD: plastic metal working; calibration of tubular articles.

SUBSTANCE: plastic metal working is performed on mandrel made from material whose coefficient of linear expansion exceeds coefficient of linear expansion of billet; proposed method includes simultaneous heating of billet and mandrel to aging temperature of billet material followed by subsequent cooling. First, preliminary calibration of article is made on mandrel whose outer diameter is found from the following expressions: D_mand=(D_nom+D_bil.α_art.t)(1+α_mandΔt) α_mand>(D_nom-d_bil/Δtd_bill +α_art, where D_mand is outer diameter of mandrel; D_nom is nominal inner diameter of finished article; D_bil is inner diameter of billet; d_bil is minimum inner diameter of billet; α_art and α_mand are coefficients of linear expansion of article and mandrel, respectively; Δt is difference between heating temperature and surrounding temperature; then, diameter of article is determined and final diameter of calibration mandrels is found from the following expression: d_mand=D_mand+D_nom-D₀, where D₀ is diameter of article without preliminary calibration; d_mand is final diameter of calibration mandrels.

EFFECT: improved quality; enhanced accuracy of diametric sizes of articles; facilitated procedure.

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