A new method of assessment of the inlet roll cone in the piercing mills was proposed. A new all-round method of determination of the profile and length parameters of the working plug section was developed for piercing billets. The method is based on the calculation of the working section length ensuring required drafts ahead of the plug nose (u_(nose)) and at the gorge (u_g). Profile of the working plug section can be determined for any law of wall thickness variation at this plug section. The work used the law of constancy of reduction of area in each cycle. This work recommendations were used in the development of the plug designs for the piercing mills operated at PNTZ JSC tube rolling plants. Industrial tests confirmed the possibility of reducing metal slippage in axial direction and increasing piercing speed. The obtained results were in accord with the conclusions made in theoretical studies with the use of the method of electrohydrodynamic analogies. A method for analysis of the shoe position in the deformation zone with the use of the relative parameter factorial planes was proposed.
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