| Tempering is a core procedure of the cold-rolled strip steel finishing processes. Due to the issues of dusts, metal powders, and visible marks on the strip steel surface in dry temper, wet temper process for cold-rolled strip steel is widely used. In this paper, flow-fileds of emulsion spray and blowing-off in a dual-stand temper mill were simulated numerically and experimentally studied.Pro/E was adopted to establish a full three-dimensional physical model of the backup roll surface impinging jet flow field, and full hexahedral structural grids were meshed by ICEM CFD. Steady-state, implicit pressure-based solver and standard k–ε turbulence model solver was choosed. Pressure and velocity were coupled by SIMPLE algorithm. Wet temper emulsion spray flow field model, consists of 8 Lechler 660.404.16 nozzles, emulsion ramp and partial of backup roll surface, was calculated and solved by VOF method.The impacts of process parameter, such as twist angle, liquid-supply pressure, target distance and spray incidence angle, on fluid velocity field, pressure field, flow trajectories, liquid flow dynamic pressure and impact force were obtained.Wet temper blow-off flow field physics model of the dual-stand temper mill and its full hexahedral structural grids were established with the same modelling and meshing softwares. And the blow-off flow field was simulated numerically by S–A model in Fluent. Some influence factors, involving blow-off nozzle supply pressure, flip-angle and blow-off incidence angle, etc. on blow-off flow field velocity distribution, pressure field distribution, action characteristics and force distribution rule on roll-gap were explored. Dynamic-pressure distribution rules on the work and backup roll-gap and near the roll surface were analyzed. Thereafter, roll surface dynamic pressure amplification effect was proposed.Since the number of influence factors and their levels on spray flow field and the blow-off flow field was large in cold-rolled strip steel wet temper, to determine the optimum technological conditions or other working condition parameters, orthogonal experimental design and numerical simulation experiments on wet temper emulsion spray and blow-off flow field were combined. 9 groups of 4 factors, 3 levels and 2 resulting indicators of orthogonal numerical simulation experiments on spray flow field and 16 groups orthogonal numerical simulation experiments of 5 factors, 4 levels and single indicator on blow-off flow field were designed. The numerical simulation experimental indicators were analyzed afterwards the relative schemes were numerically simulated. Range analysis and variance analysis on the main influence factors, including air-supply pressure, liquid-supply pressure, flip-angle, twist angle, spray incidence angle, target distance, spray or blow-off nozzles spacing were performed. The order of influence degree and significance of the wide variety of influence factors effected on dynamic pressure and impact force were discussed, and the optimum technological or other working condition parameters were acquired.Barrel surface spray and sand blow-off experimental devices were designed and constructed, and relative wet temper spray and blow-off experiments were accomplished. Flow patterns were directly observed, and flow characteristic parameters were measured. In the meanwhile, pressure–flux curve, dynamic pressure distribution and flow pattern and residual sand profile observation results were compared with the ones of numerical simulation. The correctness of wet spray and blow-off flow field numerical simulation was verified.This study provides theoretical references for on-site installation and adjustment of the wet temper emulsion spray and blow-off system, reduction of spray and blow-off blind zone, improvement of spray and blow-off effects, elimination of residual emulsion and resulting emulsion marks phenomenon and enhancement of cold-rolled strip-steel surface quality in cold-rolled strip steel factory. |
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