摘要
在我国有色金属加工工业中,冷轧生产铌、钛短板时普遍不施加张力轧制,在实际生产中,轧制效率低,生产节奏慢,消耗能源多,生产效率低下。本文针对以上问题深入的分析了铌、钛材本身的金属学性质,提出在张力作用下冷轧铌、钛短板。由于铌、钛金属变形时与本身的晶体结构有关,尤其是钛在变形时滑移系少,塑性变形原动力的滑移被限制在特定的方向上,显示出很强的各向异性。同时钛的屈服极限与抗拉极限接近,增加了冷变形过程的难度。经过在铌、钛短板两端施加张力进行冷轧实验,在张力作用下,有效地改善了铌、钛短板塑性变形条件和应力状态,可以实现大压下量变形,显著提高了轧制效率。采用本方法灵活简单,便于应用到实际生产中。
由于铌、钛材力学性能各向异性的特点,本文以Hill的异性屈服准则为基础,推导出Hill平面变形塑性力学方程,从而在理论上验证了张力对冷轧铌、钛短板的塑性变形条件和应力状态具有改善作用。
由于张力对冷轧变形具有诸多的作用,可以改善铌、钛短板的轧制条件。针对以上的分析在东北大学轧制技术及连轧自动化国家重点实验室的直拉式四辊可逆冷轧实验机上对铌、钛短板进行了张力冷轧实验研究。经过反复的实验摸索,施加一定的张力,冷轧铌可以明显的提高轧制效率；钛板经过3个道次的轧制,变形率达到62.5%,而且板形良好,极大的提高了轧制效率。施加张力后还可大幅的降低轧制力,从而可有效的减小轧辊压扁,更有利于铌、钛短板的轧薄。
实验结果表明,张力冷轧铌、钛短板的最大优点是能够有效地提高轧制效率,保证良好板形的前提下实现单道次的大压下变形,提高生产效率,降低能耗。张力的加载灵活简单,易于调整。是实用有效的新型生产方式,值得进行推广和应用。
In the nonferrous metal rolling processing, tension will not be usually applied during cold rolling niobium or titanium short slab in China, which result in lower rolling efficency, production, but higher energy consumption. Based on the analysis of metallic characters of niobium and titanium, cold rolling niobium and titanium slab under tension condition was brought forward. The deformation of niobium and titanium slab correlates with their crystal structures, espescially titanium has fewer slip systems, so that slippings are restricted to given directions when it deforms and shows strong aeolotropy. The yield limit and tensile limit of titanium are adjacent, which increase the difficulty of cold deformation. Applying tension to both sides of niobium or titanium short slab when rolling, the plastic deformation and stress conditions are improved, which permits larger pressure and improves efficency. It is also easy to be adopted in practical processing.
Based on the Hill isomerism yield principle, the planar deformation plastic mechanical equation was educed, which also validated the effects of tension to cold rolling niobium or titanium short slab.
Tension also improves the rolling conditions of niobium or titanium short slabs as verified. A four-high reversing rolling mill from the State Key Laboratory of Rolling and Automation was used to go on the experiment so that the optimizing process was put forward. Under certain tension, the cold rolling efficiency of niobium was improved obviously. After three passes,the deformation rate of titanium slab reachs 62.5 percent and the shape of the strip is perfect. Rolling under tension can also reduce the draught pressure with decreased roller flattening,which is favorable to reduce the thickness of cold rolling niobium or titanium short slabs.
The experiment and the theoretical analysis show that tension improves rolling and producing efficiency, reduces the cost of energy, And make it possible to roll with maximum press and perfect strip shape in a single pass. The loading of tension is flexible and simple.So it is a new effective mode of production which should be applied and extended in practical producing.
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