Numerical Study on Motions of Rolls in Hot Rolling of Titanium Alloy Large Rings

Titanium alloy is sensitive to strain rate, so motions of rolls are crucial to the hot rolling process of titanium alloy large rings. In the study, firstly, the relative velocity nu(r) was proposed to synthesize motion parameters of rolls, including the rotational velocity of the driver roll n(1) and the feed rate of the idle roll nu, and then the reasonable range of nu(r) was determined analytically based on the stable forming condition. Secondly, a reliably coupled thermo-mechanical 3D-FE model of the process was developed in the dynamic explicit code ABAQUS/Explicit. Finally, the effect of nu(r) on the process was studied using FE simulation. The results obtained show that although increasing nu(r) by two different ways, i.e., by decreasing n(1) or by increasing nu, makes the feed amount per revolution Delta h(i) increase, not all of their effects on the process are in agreement, such as for the nonuniformity of strain distribution. An appropriately larger value of nu(r) is helpful to improve the end-plane quality and make strain and temperature distributions in a deformed ring more uniform, but has an adverse influence on the roll force.