Predictive Modelling of Pinching in Cold Rolling of Advanced High Strength Steels

Duration

Start: 01-09-2017
End: 31-08-2021

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Description

During the last few decades lower CO2 emissions through weight reduction became point of great interest, especially for the automotive industry. Advanced High Strength Steel (AHSS) grades allow to reduce thickness of the finished components, while maintaining high mechanical performances. Therefore, steel producers need to meet an increasing demand for thin gauge AHSS products. However, cold rolling of thin strips is a critical process, which often suffers from instabilities. Indeed, during rolling of thin sheets defects may occur, such as local waviness, surface ruptures, and sometimes strip breaks (see Figure 1). These phenomena, commonly referred to as “pinching”, have been observed in combination with snaking problems (strip sideward movements) during tailing out, but even in continuous rolling processes. Pinches compromise the quality of the strip and, in the most severe cases, damage to the work rolls can also be caused. This clearly affects the production, resulting in process delays and extra costs.

Figure 1: Defects in thin sheet rolling

Even though pinching is a widely experienced issue, during both hot and cold rolling, it is not clear what mechanism is behind it. Pinches occur due to disruptions in the rolling process, therefore pinching sensitive operative regimes need to be identified such that mill operations can be performed in a way that keeps the process stable.

Currently, pinching cannot be predicted by rolling simulation models. Therefore, the task of this research work is to develop a simulation tool (FEM model) in which pinches can be predicted as a consequence of disruptions in the process. The numerical modelling is based on in-depth experimental investigation of pinching phenomena, which has the objective of detecting the major underlying factors and circumstances leading to pinching.