Improvements of Modeling Incremental Permeability in the 3MA System for on-Line Steel Strip Property Assessment.

Meilland, Philip; ArcelorMittal Maizières Research; France

Meilland, P.; ArcelorMittal Global Research; France
Lombard, P.; ArcelorMittal Global Research; France

ID: ECNDT-0218-2018
Download: PDF
Session: Modeling and data processing Electromagnetic Techniques 2
Room: J2
Date: 2018-06-12
Time: 11:10 - 11:30

P. Meilland (ArcelorMittal Maizières Research), P. Lombard (Altair)
IzfP’s 3MA system is a promising solution for contactless on-line assessment of strip properties at e.g. the exit of continuous annealing and galvanizing lines. However, interpreting its outputs in relation to the strip properties meets the following complexities:
• 3MA operation includes the incremental permeability mode, which consists of reading the impedance of a high frequency eddy-current pick-up coil during the application of a low frequency magnetization cycle with a U-shaped yoke electromagnet
• The strip is considered as a multilayer material, with a bulk material sandwiched between skin-passed layers and Zn coating – each layer having its thickness and electromagnetic properties
To model this system, the Flux 2D code developed by Cedrat/Altair was adapted in order to be able to take into account magnetic hysteresis with the original implementation of an invertible vector model based on the Jiles-Atherton approximation. This allowed the 3MA incremental permeability signals to be modelled in the case of a Dual-Phase (DP) steel coated with variable Zn thicknesses.
Several issues were then addressed when extending the application of this simulation strategy to the case of Interstitial Free (IF) steels, which are softer:
• They feature high dB/dH slopes, in such a way that Jiles-Atherton optimized solution comes in with negative permeability. This was overcome by considering minor cycles which do not bring the material to saturation.
• The model considers 2D vectorial anisotropic permeability instead of the scalar approach which provided satisfactory results with hard DP grades.
• The hysteretic region was extended from the area below the pick-up coil to the full sheet volume between the poles.
With such improvements, the soft steel behavior and subsequent 3MA signals could be successfully modeled, leading to sensitivity analyses which proved consistent with laboratory measurements.