Online 3D line-laser detection and physics-guided asymmetric cooling control of C-warp in hot-rolled strip laminar cooling

Widthwise C-warp in hot-rolled strip may develop or intensify during laminar cooling because of asymmetric heat transfer, through thickness temperature gradients, and inherited shape defects. This industrial case study presents a measurement assisted and physics guided method for evaluating and suppressing widthwise C-warp during hot-strip laminar cooling. A high-density three-dimensional line-laser measurement system was installed at the exit of the laminar cooling section to reconstruct the full-width strip profile, and the C-warp height was extracted through point-cloud stitching, outlier removal, reference-plane correction, and transverse profile fitting. A thermo-mechanical finite element model incorporating initial C-warp defects was developed and validated using plant measurements. The predicted final C-warp heights agreed well with measured values under different strip thicknesses, widths, and initial C-warp conditions, with relative errors below 5%. The validated model showed that increasing strip thickness and width intensified post-cooling C-warp evolution, whereas tension variation within the investigated industrial range had little influence. Based on the relationship between the water flow ratio of bottom header to top header and the heat transfer coefficient ratio of top surface to bottom surface, an asymmetric cooling compensation strategy was proposed. For 1200 mm × 2.5 mm DP590 strips with initial C-warp heights of 5–20 mm, optimized water flow ratios of bottom header to top header of 1.72–2.47 reduced the final C-warp height to 0.3–1.2 mm, corresponding to reduction rates of 91.8%–94.9%. Industrial validation using 320 coils further showed that the qualified rate increased from 15.0% to 88.0%–93.0%. The results demonstrate that the proposed method can effectively improve thermal-process uniformity and post-cooling widthwise flatness in hot-strip production.