Article Article
Application of Non-Destructive Testing, ANSYS Analysis and Advanced Microstructural Characterization to Detect-Locate-Define and Simulate Defects in AHSS Steel Slabs

During continuously casting of steel slabs production, the presence of surface and internal defects takes place. These defects can include cracks, voids, coarse non-metallic inclusions and heavy local chemical and microstructural segregation. Many NDT techniques have been developed and used to assess the presence of these defects which have a specific “fingerprint” response to sound waves interaction. The factors responsible for these defects are often related to mechanical, thermal, or transformation stresses during the solidification process of the slabs. The high thermal stresses result from the difference in volume expansion or contraction behavior caused by the frequency of the temperature fluctuation during solidification. In order to study the effect of these temperature fluctuations a model of the thermal stress field using ANSYS simulation software was employed. In addition, to validate the model results a NDT-UT system was used to detect and localize the presence of the defects caused by thermal or transformation stresses. The results from the NDT-UT scanning were assessed with the image processing analysis to identify the size of the defects and their location in the slabs. These results were complemented with a systematic advanced microstructural characterization technique. The results of this study will be presented and discussed.

  • Thomas B.G., “Continuous Casting,” The Encyclopedia of Materials: Science and Technology. Vol. 2, 2001, pp. 1595-1599.
  • Yamanaka A, Nakajima K and Okamura K., “Critical strain for internal crack formation in continuous casting.”, Ironmaking and Steelmaking, 1995; 22(6):508–512.
  • Won YM, Kim KH, Yeo T and Oh KH., “Effect of cooling rate on ZST, LIT and ZDT of carbon steels near melting point.”, ISIJ International, 1998; 38(10):1093–1099.
  • Won YM, Han HN, Yeo T and Oh KH., “Analysis of solidification cracking using the specific crack susceptibility.” ISIJ International 2000; 40(2):129–136.
  • Bernard C, Hiebler H and Wolf M., “Simulation of shell strength properties by the SSCT test.” ISIJ International, 1996; 36(Suppl.): S163–S166.
  • C. S. Li and B. G. Thomas: Metall. Mater. Trans.B, 35 (2004), 1151.
  • S Lei, S Zeng, ZW Han, JW Yan, K Feng, and SP Qing: Contin. Cast., 2013, vol. 380, pp. 5–11.
  • Gur C. H. and Tekkaya A. E., “Finite element simulation of quench hardening”, Steel research (Steel res.), ISSN 0177-4832 CODEN STLRCX, 1996, vol. 67, no. 7, pp. 298- 306.
  • Kristiansson JO., “Thermal stresses in the early stage of solidification of steel.” Journal of Thermal Stresses, 1982; 5:315–330.
  • Savage J and Pritchard W H., “The problem of rupture of the billet in the continuous casting of steel.”, Journal of the Iron and Steel Institute, 1954, 178(27):269-277.
  • Miaoyong Zhu, Zhaozhen Cai and Sen Luo., Steel Research Int., 2012, Vol. 83:1-10.
  • J.M.Cabrera-Marrero, V.O. Galindo, R.D.Morales. ISIJ Int.1998 38(8): 812-821.
  • S Zhao, D Wei, R Li and L Zhang, Effect of Cooling Rate on Phase Transformation and Microstructure of Nb-Ti Microalloyed Steel, Materials Transactions, Vol. 55, No. 8 (2014) pp. 1274 to 1279
  • F. J. Ma, G.h. Wen,P. Tang, G.D. Xu, F. Mei and W.L.Wang. “Effect of Cooling Rate on the Precipitation Behavior of Carbonitride in Microalloyed Steel Slab”, Metallurgical and Materials Transactions B, 2011, 42(1), 81-86.
  • F. J. Ma, G. H. Wen, P. Tang, X. Yu, J. Y. Li, G. D. Xu and F. Mei. In situ observation and investigation of effect of cooling rate on slab surface microstructure evolution in microalloyed steel[J]. Ironmaking and Steelmaking. 2010, Vol. 37, No. 3, pp: 211-217.
  • M. Hua, C.I. Garcia, and A.J. Deardo. Precipitation behavior in ultra-low-carbon steels containing titanium and niobium. Metallurgical and Materials Transactions A. 1997, vol. 28A, pp. 1769–1780.
  • A. Ouispe, S.F. Medina, and P. Valles: ISIJ Int., 1997, vol. 37, pp. 783–88.
  • B. Weisgerber, M. Hecht, K. Harste. Improvement of surface quality on peritectic steel slabs[J].Steel Research, 2002,73(1):15
  • C. M.Chiman and K.Morwald. micromechanical investigation of the hot ductility behavior of steel. ISIJ International, 1999, 39(11): 1194-1197.
  • F. J. Ma, G. H. Wen, P. Tang, X. Yu, J. Y. Li, G. D. Xu and F. Mei. Causes of transverse corner cracks in micro alloyed steel in vertical bending continuous slab casters. Ironmaking & Steelmaking. 2010, Vol. 37, No.1, pp:73-79.
  • C.B. Shi, W. J. Liu, J. Li and L. Yu. Effect of Boron on the Hot Ductility of Low-Carbon Nb-Ti-Microalloyed Steel. Materials Transactions, Vol. 57, No.5, (2016), pp: 647-653.
  • O. Comineli, The Influence of cooling rate and microalloying addition of Ti and Nb on the hot ductility of HSLA steels, Thesis, In Dept. Mechanical Engineering and Aeronautics. 1998, City University: London.
  • K. Carpenter: MEng Thesis, University of Wollongong, 2004.
  • B. Mintz, J.M. Arrowsmith. Hot-ductility behaviour of C-Mn-Nb-Al steels and its relationship to crack propagation during the straightening of continously cast strand. Metals Technology, 1979. Vo. 6, 24~32
  • S.C. Moon: MEng Thesis, University of Wollongong, 2003.
  • Allazadeh M.R., C.I. Garcia and A. Deardo. “Analysis of Stress Concentration around Inclusions due to Thermally Induced Strain to the Steel Matrix.” Journal of ASTM International, Vol. 6, No.5, 2009, pp. 1-12.
  • Baker T. J. and Charles, J.A., “Further Aspects of Inclusion Deformation.”, Metals Techno, Vol. 1, 1974, pp.425-431.
Usage Shares
Total Views
214 Page Views
Total Shares
0 Tweets
0 PDF Downloads
0 Facebook Shares
Total Usage