Mathematic modeling on flexible cooling system in hot strip mill

Abstract

A novel cooling system combining ultra fast cooling rigs with laminar cooling devices was investigated. Based on the different cooling mechanisms, a serial of mathematic models were established to describe the relationship between water flow and spraying pressure and the relationship between water spraying heat flux and layout of nozzles installed on the top and bottom cooling headers. Model parameters were validated by measured data. Heat transfer models including air convection model, heat radiation model and water cooling capacity model were detailedly introduced. In addition, effects on cooling capacity by water temperature and different valve patterns were also presented. Finally, the comparison results from UFC used or not have been provided with respect to temperature evolution and mechanical properties of Q235B steel grade with thickness of 7.8 mm. Since online application of the sophisticated CTC process control system based on these models, run-out table cooling control system has been running stably and reliably to produce resource-saving, low-cost steels with smaller grain size.

Keywords

mathematic model / ultra fast cooling / laminar flow cooling / variable frequency control / coiling temperature control

References

[1] ImanariH, DengW-f, ShimodaN. Advanced coiling temperature control system in hot strip mill [C]. Proceedings of the 10th International Conference on Steel Rolling, 2010, Beijing, Metallurgical Industry Press: 473-479

[2] HermanJ C. Impact of new rolling and cooling technology on thermo mechanically processed steels [J]. Ironmaking and Steelmaking, 2001, 28(2): 159-163

[3] SimonP, FischbachJ P, RicheP. Ultra fast cooling on the run-out table of the hot strip mill [J]. Revue de Metallurgie, 1996, 93(3): 409-415

[4] HouyouxC, HermanJ C, SimonP. Metallurgical aspects of ultra fast cooling on a hot strip mill [J]. Revue de Metallurgie, Cahiersd’ Informations Techniques, 1997, 97: 58-59

[5] LeeuwenY V, OninkM, SietsmaJ, van der ZwaagS. The gamma-alpha transformation kinetics of low carbon steels under ultra-fast cooling conditions [J]. ISIJ International, 2001, 41(9): 1037-1046

[6] LiuX-h, SheG-f, JiaoJ-m, ZhangZ-p, PengL-g, WangG-dong. An ultra fast cooling system for the products of hot flat rolling [J]. Iron and Steel, 2004, 39(8): 71-74

[7] BuzzichelliG, AnelliE. Present status and perspectives of European research in the field of advanced structural steels [J]. ISIJ International, 2002, 42(12): 1354-1363

[8] KagechikaH. Production and technology of iron and steel in Japan during 2005 [J]. ISIJ International, 2006, 46(7): 939-958

[9] Super-OLAC H introduced at hot strip mill for automotive steel sheet production [EB/OL]. [2002-06]. httrp://www.jfe-holdings.co.jp/en/release/nkk/42-5/art06.html.

[10] WangG-dong. The new generation TMCP with the key technology of ultra fast cooling [J]. Shanghai Metals, 2008, 30(2): 1-5

[11] TianY, TangS, WangB-x, WangZ-d, WangG-dong. Development and industrial application of ultra fast cooling technology [J]. Science China, 2012, 55(6): 1566-1571

[12] PengL-g, ZhaoX-m, WuD, GaoY, ZhangZ-p, LiuY, SunL, YuD-hong. Study on ultra fast cooling technology in hot strip mill [J]. Advanced Materials Research, 2012, 418-420: 1635-1639

[13] MaierlJ, HaringB, BurgerR, WeinzierlK. Advanced strip cooling solutions for hot-strip mills mechanical actuators, microstructure target cooling and microstructure monitor for online control of strip properties [C]. Proceedings of the 10th International Conference on Steel Rolling, 2010, Beijing, Metallurgical Industry Press: 492-498

[14] PengL-g, LiuE-y, ZhangD-h, LiuX-hua. Development and application of advanced coiling temperature control system in hot strip mill [J]. Advanced Materials Research, 2012, 421: 140-146

[15] LiuE-y, PengL-g, YuanG, WangZ-d, ZhangD-h, WangG-dong. Advanced run-out table cooling technology based on ultra fast cooling and laminar cooling in hot strip mill [J]. Journal of Central South University, 2012, 19(5): 1341-1345

[16] PengL-g, GaoY, ZhaoX-m, WuD, ZhangZ-p, LiuY, SunL, RenL-xin. Development of ultra fast cooling variable frequency control system in hot strip mill [J]. Advanced Materials Research, 2012, 442: 199-203

[17] DevadasC, SamarasekeraI V. Heat transfer during hot rolling of steel strip [J]. Ironmaking and Steelmaking, 1986, 13(6): 311-321