Experimental and theoretical investigation on tilting in bar and rod rolling using diamond-square pass and square-oval pass

Metals under bar and rod rolling often exhibit tilting, due to smaller width height ratio of bar and wire rod under rolling. Design of calibers and rolling conditions to reduce tilting of stock is of industrial importance, as tilting may result in wrinkling and overfilling of rolled product, or miss rolling of bar and wire rod. Characteristics of tilting under bar rolling are investigated experimentally and analytically, aiming to clarify threshold for the occurrence of overturning and restoration resulting from tilting. Tilting of bar under rolling can be classified into two modes. Mode 1 tilting is resulting from steady-state twisting deformation in roll bite. This mode takes place even though position of entrance cross-section is constrained strongly by guide or previous stand, and this mode can be directly analyzed by steady-state FE analysis. Mode 2 tilting takes place in the bar before rolling, when constraint from guide or previous stand is relatively small. This mode can be evaluated using normalized moment acting to entrance of bar obtained by FE analysis. Steady-state FE analysis of bar under rolling is successfully applied to predict tilting of bar in Square-Diamond Pass and Square-Oval Pass. Predicted results agree well with the experimental measurements for tilting of mode 1 as well as mode 2. It can be concluded that FE analysis is helpful to the design of calibers and rolling conditions for bar rolling and rod rolling.