异步轧制7xxx系铝合金中厚板形变及翘曲优化研究

发布时间：2018-01-31 23:46

本文关键词： 铝合金中厚板异步轧制形变翘曲力学性能　出处：《北京科技大学》2016年博士论文　论文类型：学位论文

【摘要】：异步轧制作为一种可引入剧烈附加剪切变形而使板材心部缺陷消除、厚向组织及性能均匀性获得改善的加工技术被广泛应用于薄板带材生产和研究。然而异步轧制过程中存在的板材翘曲问题限制了其在中厚板轧制生产中的应用。因此在确保异步轧制引入剧烈剪切变形的同时,最小化或消除板材翘曲现象成为其应用于中厚板生产需解决的关键问题。本文利用有限元数值模拟和实验研究了异步轧制中厚铝板的变形行为及关键工艺参数对组织演化的影响,并基于关键异步轧制工艺参数对翘曲的影响,发现多轧制参数间的关联规律,获得无翘曲或翘曲最小化异步轧制控制原理和工艺,实现了无翘曲连续化异步轧制和板材制备,明显提高板材的综合力学性能。主要结论如下：模拟研究发现,异步轧制变形区内板材受到的总剪切变形是前滑区引入的正剪切变形和后滑区引入的负剪切变形共同作用结果,使多道次异步轧板获得更高剪切变形,尤其轧板心部剪切应变由同步轧制的0.026提高到0.836。采用刻蚀“标志线”法研究异步轧制铝合金中厚板材的宏观变形行为发现,多道次异步轧制可大幅提高板厚向的剪切和等效应变,而同步轧制的剪切变形只集中于板材表面。虽然异步轧板表面应变的增加远高于心部并导致应变分布不均匀性增加,但由于异步轧板心部剪切与压缩变形的大小处同一量级,故该应变不均匀性未显著增加后续组织不均匀性。总压下量一定,减少道次压下量可累积更多附加剪切变形,并大幅提高板厚向变形均匀性。采用10-30%的异步轧制道次压下量可获得厚向均匀分布的细小晶粒,明显改善T6态延伸率及其厚向均匀性。针对异步轧制变形路径的研究发现,ASR-R变形路径可通过道次间附加剪切变形的相互交叉促进变形向板材心部深入,从而提高板厚向变形及组织均匀性。基于异步轧板翘曲曲率与关键工艺参数间演变规律的研究,构建了异步轧板实现“变曲”现象所需临界道次压下量与异速比、轧辊辊径和轧板初始厚度间的关联工艺图及经验关系式;利用所获无翘曲异步轧制工艺原理,首次实现了40mm7050中厚板的无翘曲连续异步轧制,获得了板型平直的异步轧板,其T6态延伸率、LT和TL方向上的断裂韧性均较同步轧板明显提高。
[Abstract]:Asynchronous rolling as a kind of severe additional shear deformation can be introduced to eliminate plate core defects. The processing technology of improving the homogeneity of thick structure and properties has been widely used in the production and research of thin plate and strip. However, the warpage problem in asynchronous rolling process limits its application in the production of medium and thick plate. Therefore, while ensuring the introduction of severe shear deformation in asynchronous rolling. Minimizing or eliminating the warpage is the key problem to be solved in plate production. In this paper, finite element numerical simulation and experiment are used to study the deformation behavior and key process parameters of asynchronous rolling medium and thick aluminum plate. The influence of organizational evolution. Based on the influence of key parameters of asynchronous rolling on warpage, the correlation rule of multi-rolling parameters is found, and the control principle and process of non-warpage or warpage minimization are obtained. Non-warping continuous asynchronous rolling and plate preparation can obviously improve the comprehensive mechanical properties of the plate. The main conclusions are as follows: simulation research found. The total shear deformation of plate in the deformation zone of asynchronous rolling is the result of both the positive shear deformation introduced by the front slip zone and the negative shear deformation introduced by the backward slip zone, which makes the multi-pass asynchronous rolling plate obtain higher shear deformation. Especially, the shear strain in the center of rolling plate was increased from 0.026 to 0.836. The macroscopic deformation behavior of asynchronous rolling aluminum alloy plate was studied by etching "mark line" method. Multi-pass asynchronous rolling can greatly increase the thickness shear and equivalent strain of the plate. While the shear deformation of synchronous rolling is only concentrated on the surface of the plate, although the increase of strain on the surface of asynchronous rolling plate is much higher than that of the center, which results in an increase in the uneven distribution of the strain. However, due to the same order of magnitude of shear and compression deformation in the center of asynchronous rolling plate, the strain inhomogeneity does not significantly increase the inhomogeneity of subsequent microstructure, and the total reduction is constant. Reducing pass reduction can accumulate more additional shear deformation and greatly improve the uniformity of plate thickness deformation. The fine grains with uniform thickness distribution can be obtained by using 10-30% of the secondary reduction of pass in asynchronous rolling. The elongation of T6 state and its thickness uniformity are obviously improved. The ASR-R deformation path can promote the deformation to the center of the plate through the intersecting of the additional shear deformation between the passes. In order to improve the thickness deformation and microstructure uniformity of the plate, based on the asynchronous rolling plate warpage curvature and key process parameters of the evolution of the study. The correlation process diagram and empirical relation between the critical pass reduction rate and the different speed ratio, the roll diameter and the initial thickness of the rolling plate are constructed for the realization of "bending" phenomenon in asynchronous rolling plate. Based on the principle of non-warping asynchronous rolling, 40mm 7050 plate without warping has been rolled continuously for the first time, and the straight plate has been obtained, and its T6 elongation has been obtained. The fracture toughness of LT and TL direction is obviously higher than that of synchronous rolling plate.
【学位授予单位】：北京科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TG339

【相似文献】