Closed-loop X-ray control of austenite content for consistent AHSS properties

The X-CAP® system brings inline X‑ray diffraction into the annealing furnace to measure austenite fraction in real time and enable true closed‑loop control of AHSS heat treatment. As part of the Intelligent Furnace concept, X-CAP® links Drever Matemathical Model and online measurement to compensate for upstream process and material variations. The result is tighter, repeatable mechanical properties coil‑to‑coil and along the strip, reduced rejects and higher yield for Continuous Annealing Lines (CAL) and Continuous Galvanizing Lines (CGL) regarding multi-phase steels.

X-CAP® device

Customer challenges addressed

  • Inconsistent mechanical properties along the coil and between coils due to uncontrolled austenite fraction before rapid cooling
  • High rejection rates and coil losses for modern AHSS grades (DP800 and higher) caused by process and material variability
  • Limited ability to perform closed‑loop control because conventional measurements occur downstream, after properties are fixed
  • Process drift and material variability from upstream steps that are hard to detect and correct in time
  • Operator dependence and limited predictability of final strength without direct in process phase measurement

Key features

  • Minimized coil losses and maximized yield through immediate compensation for process and material deviations
  • Significant rejection‑rate reductions demonstrated (e.g., DP600 47%, DP800HP 88%)
  • Continuous quantification of the austenite fraction inside the furnace enables precise control of phase transformation and final mechanical properties
  • Delivers more consistent product quality with reduced operator input - enabling higher throughput and boosting customer confidence
  • Easily integrated into existing CAL and CGL lines thanks to a movable X-ray gauge, protective water-cooled tubes, and low-attenuation windows

Highlights

  • Material properties of finished AHSS grades

    X‑ray diffraction-based phase data allow precise adjustment of the austenite fraction before rapid cooling, which determines the formation of the secondary hard phases and thus the final strength for AHSS grades. Demonstrated results include substantial reductions in rejection rates (example averages: DP600 47%, DP800HP 88%) and significant coil savings through compensation of process and material deviations. 

    Material properties along a strip length

  • Brownfield deployment

    X-CAP® integrates with the concept of Intelligent Furnace to enable inline phase measurement, furnace control, online strength measurement and prediction models. Suitable for brownfield retrofits on CAL and CGL lines, it provides deterministic control of microstructure-driven properties, reduces scrap, increases throughput and ensures repeatable coil-to-coil quality and higher overall yield.

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