Modelling of strip buckling in the continuous annealing process

Abstract

This paper considers the equipment and technological characteristics of continuous annealing process (CAP) to solve the issue of strip buckling. It analyses the mechanism of hot buckling and transverse compressive stresses from internal and external forces. A basic description of strip buckling is given together with a new concept of a buckling index. The critical buckling condition is presented, and the model of strip buckling index in the CAP is proposed. The distribution of strip buckling index in different sections of the process is analysed quantitatively along with the influence of incoming strip shape, transverse temperature difference, roller profile, friction coefficient, set tension and strip processing speed on the strip hot buckling index in CAP. Results show that with the influence of thermal stress, the transverse compressive stress that affects the middle part of the strip is largest in the heating section, which is also where hot buckling occurs most easily; centripetal force is dominant in the soaking and slow cooling sections, and in these sections buckling occurs at the roller shoulder. In different sections, the strip buckling index distribution differs, whereas the influence of other parameters on buckling index remains similar.

Development of a virtual shapemeter based on a shape control model for continuous annealing

“…The prediction accuracy of the virtual shapemeter mainly depends on the accuracy of the shape model, and the strip shape in the annealing furnace is affected by the original strip shape, heating temperature, set tension and roller profile. Thus, according to the field test, calculations of strip shape can refer to the shape model in Reference (Bai et al, 2017).…”

“…Therefore, it is very necessary to precisely measure and control the strip shape. The wave shape of strip changes very obviously with residual stress and sometimes the hot buckling will appear along the longitudinal or oblique direction of strip (Kpogan and Potier-Ferry, 2017;Bai et al, 2016), which are mainly affected by furnace roller profile (Elias and Onno, 2017), tension (Shi et al, 2017), thermal stress, etc. The analytical method (Rui et al, 2017) and finite element method (Pietrzyk et al, 2014;Jacques et al, 2007) have been extensively used to study buckling deformation, residual stress distribution and influence factors.…”

“…The analytical method (Rui et al, 2017) and finite element method (Pietrzyk et al, 2014;Jacques et al, 2007) have been extensively used to study buckling deformation, residual stress distribution and influence factors. Especially, Bai et al (2017Bai et al ( , 2015 put forward a basic description of strip buckling with a new concept of buckling index, established a model of strip buckling index in continuous annealing, quantitatively analysed the influence of original strip shape and transverse temperature difference on buckling. He provided a set of comprehensive control models suitable for continuous annealing process and developed a set of online prediction and control technology for cold rolling strip shape.…”

“…The shape control includes two aspects, namely, the first is shape control in processing stage, which ensures stable operation of strip, and the second is to get the exit shape closest to the target shape. So, the objective function (F X ð Þ ) to be optimised can be expressed as equation ( 17) (Bai et al, 2017).…”

Comprehensive optimisation technology of roller profile in continuous annealing furnace

“…At the same time, according to the calculation model of the buckling index [20], the buckling index lcan be expressed by the following formula:…”