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

摘要:

由于钛合金对应变速率十分敏感，因此轧辊运动对钛合金大环热辗扩成形过程有重要作用。提出了相对速率vr的概念来表征轧辊运动参数的综合作用，涉及的运动参数包括驱动辊旋转速率n1和芯辊进给速率v，并且基于稳定成形条件采用解析方法确定了vr的合理取值范围。其次，运用动力显式有限元程序ABAQUS/Explicit建立了可靠的钛合金大环热辗扩成形过程的热力耦合三维有限元模型。最后，采用有限云模拟方法，探究了vr对该成形过程的影响效应及其机制。结果表明；尽管通过减小n1来增大vr与通过增大v来增大vr均使每转进给量Δhi增大，但它们对成形过程的影响效应并非完全一致，比如对非均匀应变分布的影响；较大的vr有助于提高成形环件的端面质量和应变与温度分布的均匀性，但对成形力有不利影响。

Abstract:

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 vr was proposed to synthesize motion parameters of rolls, including the rotational velocity of the driver roll n1 and the feed rate of the idle roll v, and then the reasonable range of vr 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 vr on the process was studied using FE simulation. The results obtained show that although increasing vr by two different ways, i.e., by decreasing n1 or by increasing v, makes the feed amount per revolution Δhi 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 vr 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.