METHOD OF DETERMINING TECHNOLOGICAL PARAMETERS OF PIERCING IN SKEW-ROLL MILL Russian patent published in 1995 - IPC

FIELD: metal pressure forming. SUBSTANCE: method comprises steps of making cylindrical templates with length values, equal to 1.5-1.7 of their diameter from steel, being tested; heating two of these templates up to temperatures, corresponding to critical point Ac₃ and to a point, being more, than the above mentioned critical point by 150 C; rolling them in a skew roll rolling mill with reduction value (6-7); measuring a depth of funnels at ends of the templates; calculating a value of total displacement of peripheral layers relative to central ones Δl by summing values of recesses of the funnels, had been created at both ends; substituting the received values for both temperatures respectively in a mathematical expression for calculating a pitch Δl₁ and Δl₂ and determining its value; heating remaining samples up to temperature values, successively increasing by the pitch value Δt_n+1; interrupting investigations, when the pitch value is equal to zero or a negative value, that corresponds to termination of growing of displacement of peripheral layers and to decreasing of metal ductility with further temperature increase. At optimal temperature value the displacement of the peripheral layers relative to central layers is maximum. EFFECT: enhanced accuracy of parameters determination. 1 cl, 1 dwg