The Mean and Local Wall Thickness Change in Tubes During Their Reducing and Sizing

摘要

1. Equations given in [2] and [15] have been corrected for calculation of S_I (S_k) and ΔS_I (ΔS_(total)). This has enabled a rather precise definition of technological and power-and-force parameters involved in the tube reducing (sizing) process within a broad range of m_I≤10%, m_(total)= 10-80%,S_(I-1)/D_(I-1) (S_0/D_0) ≤0.5 and Z_I(Z_(total)) ≤ 0.75. 2. New a_1, a_2 and as coefficients have been determined instead of ones given in [20]. This has allowed to define ΔS_I_θ more precisely in the two-roll oval pass zones and ΔS_I values around the tube perimeter corresponding to those obtainable with other equations can be obtained. 3. Utilization of the new mill design with 45°turn of one stand group (6) relative to other (8) makes it possible to reduce by 59.8% the cross-sectional wall-thickness variation in thick-walled 83X15 mm (S_k/D_k=0.18) finished tubes during stretch reducing (sizing) of 133X12 mm (S_0/D_0=0.09) tubes, Z_(total)=0, in 14 stands. 4. Employment of stretching, Z_(total) ≤ 0.4, during reducing (sizing) of thick-walled tubes reduces the final cross-sectional wall thickness variation to a still higher degree.