Deformation and Elongation Efficiency of Metals When Rolled in Different Stretching Passes of Square-Flat, Square-Oval, Square-Diamond and Round-Oval

Abstract

In order to improve the production capacity and reduction of rolling energy consumption in breaking down pass sequences of rolling of wire and rod, it is required to employ such pass sequences and rolling conditions that increase elongation per pass and elongation efficiency (f_w) defined as a ratio of natural elongation (lnλ) to natural draught (ln λ_max) imposed by the pass.
Influences of main geometrical factors, i.e., pass shape factor (m_k) thickness ratio (H₁/D₀), relative draught and degree of filling of pass (ξ) on the cross section of products and elongation efficiency are investigated for passes mentioned in the title by means of simulative rolling test using white plasticine and model plaster rolls. These simulations are checked by hot rolling of commercial steel.
The main results obtained are as follows:
1) A higher value of f_w can be obtained in the pass-rolling than in the square-flat rolling only when ξ is sufficiently high. Especially in such passes as square-diamond and round-oval where central zones in stock width get relatively heavy reduction or in passes which have high m_k value, f_w depends sensitively on ξ.
2) Limiting coefficient of elongation, λ(1), defined as a maximum permissible coefficient of elongation for a given pass increases by decreasing m_k, which tends to lower f_w. When H₁/D₀ is increased, however, λ(1) and f_w increases and drop of f_w by lowering m_k becomes alleviated.