Abstract
The strip shape inheritance model is widely applied to improve the strip shape quality in tandem cold rolling (TCR). However, the inheritance mechanism is still currently unclear. To bridge this gap, this paper presents a new numerical method for calculating the strip crown inheritance factor. In addition, the effects of the entry strip crown on exit strip crown and flatness were quantitatively analysed at each stand in the TCR using a novel three-dimensional (3D) multi-stand elastic–plastic finite element (FE) model. The results show that the strip crown inheritance factor increases slowly from S1 (stand 1) to S3 (stand 3), while rising sharply from S3 to S5 (stand 5), reaching a peak value of 0.495 μm/μm at S5. This trend coincides with that of strip plastic rigidity, which verifies that the strip crown inheritance factor is dependent on the strip plastic rigidity. Furthermore, the variation of strip crown and flatness under different entry strip crowns from S1 to S5 is jointly influenced by the pass reduction and strip plastic rigidity. Moreover, the strip crown inheritance factor increases with the deformation resistance of the strip at both S1 and S5. These findings not only offer a fresh perspective to understand the mechanism of strip crown inheritance, but also provide an important basis for optimising the strip shape control in the TCR process.
Highlights
Except a portion of hot-rolled strips used directly in the manufacturing field, the rest are used as raw material for cold rolling
From S1 to S3, the deflection of work roll (WR) axis is hill-like in shape along the strip width direction, forming the large crown of the loaded roll gap, causing the large exit strip crown. In comparison, when it comes to S4 and S5, the deflection of WR axis distributes more uniformly along the strip width direction, so the crown of the loaded roll gap profile is relatively small, resulting in a small exit strip crown
This result can be explained by the fact that: first, the strip plastic rigidity is too large [21], causing the strip hard to deform; second, the pass reduction during the downstream stands is relatively small, especially for S5 only with the reduction of 0.057 mm, and any small fluctuation of entry strip crown will have a significant influence on the plastic deformation of the strip
Summary
Except a portion of hot-rolled strips used directly in the manufacturing field, the rest are used as raw material for cold rolling. Aljabri et al [12] analysed the effect of work roll crossing on the strip crown employing a 3D symmetrical FE model. Wang et al [18] explored the effects of IRS on strip edge drop in a six-high tandem cold mill employing a 3D elastic–plastic FE model based on the explicit method. Linghu et al [20] developed a 3D FE model for multi-pass rolling in a 6-high continuously variable crown (CVC) cold mill, but data transfer between the neighbouring stands like the strip crown inheritance was not clear. In our previous study [21], a novel 3D multi-stand FE model for the TCR was proposed considering the work hardening effect, making it available for investigating the strip crown inheritance. In this paper is reported, for the first time, the study of strip crown inheritance in the TCR process employing a novel 3D multi-stand FE model. The rolling experiment was conducted on a 2180mm TCR production line to validate the established FE model in terms of the strip cross-section profile and rolling force
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