Correlation of morphological anisotropy and Lankford value of deep drawing sheets hot-rolled by compact strip production

Abstract

Cold-rolled steel sheets in automotive applications require an excellent deep draw ability, which is characterized by the Lankford value (r-value). In this study, a correlation was identified between r-value and pancake-shaped grain flatness which is indicated as the ratio of grain diameter in the rolling direction (RD) and normal direction (ND) of sheets (d _r/d _n). A mathematical model $\left( {r = e^{0.345\left( {d_n^{ - 1/2} - d_r^{ - 1/2} } \right)} } \right)$ was developed to calculate r-value by the microstructure of steel sheets hot-rolled by compact strip production (CSP). It is shown that the r-value is higher, if the microstructure of steel sheet is of pancake-shaped grains elongated in the rolling direction. The calculated r-value is confirmed to fit exactly to the measured one from the large-scale production.

Keywords

cold rolling / compact strip production (CSP) / steel sheets / deep drawing / anisotropy / Lankford values / microstructure

References

[1] Ravi Kumar D. Formability analysis of extra-deep drawing steel. J. Mater. Process. Technol., 2002, 130–131, 31

[2] Ohwue T., Hashimoto K., Kuriyama Y., Ushioda K. Analysis of flange wrinkle in square-shell deep drawing of anisotropic sheet. J. Iron Steel Inst. Jpn., 2007, 93(11): 709

[3] Daniel D., Savoie J., Jonas J.J. Textures induced by tension and deep drawing in low carbon and extra low carbon steel sheets. Acta Metall., 1993, 41(6): 1905

[4] Daniel D., Jonas J.J. Measurement and prediction of plastic anisotropy in deep-drawing steels. Metall. Trans. A, 1990, 21(1): 331

[5] Yoshinaga N., Sugiura N., Hiwatashi S., Ushioda K., Kada O. Deep drawability of electro-deposited pure iron having an extremely sharp 〈111〉//ND texture. ISIJ Int., 2008, 48(5): 667

[6] Liao J.Y. Objective analyzing of thin slab continuous casting and rolling technology. Iron Steel Vanadium Titanium, 2008, 29(4): 63.

[7] Kang Y., Yu H., Fu J., Wang K., Wang Z. Morphology and precipitation kinetics of AlN in hot strip of low carbon steel produced by compact strip production. Mater. Sci. Eng. A, 2003, 351(1–2): 265.

[8] Jia Z., Misra R.D.K., O’Malley R., Jansto S.J. Fine-scale precipitation and mechanical properties of thin slab processed titanium-niobium bearing high strength steels. Mater. Sci. Eng. A, 2011, 528(22–23): 7077.

[9] Guillet A., Es-Sadiqi E., L’espérance G., Hamel F.G. Microstructure and mechanical properties of strip cast 1008 steel after simulated coiling, cold rolling and batch annealing. ISIJ Int., 1996, 36(9): 1190

[10] Reip C.P., Shanmugam S., Misra R.D.K. High strength microalloyed CMn (V-Nb-Ti) and CMn (V-Nb) pipeline steels processed through CSP thin-slab technology: microstructure, precipitation and mechanical properties. Mater. Sci. Eng. A, 2006, 424(1–2): 307.

[11] Yu H., Kang Y., Dong H. Comparison and analysis of dislocation density, morphology and evolution in microstructure of low-carbon steel produced using different technologies. J. Univ. Sci. Technol. Beijing, 2006, 13(5): 406

[12] Riva R., Mapelli C., Venturini R. Effect of coiling temperature on formability and mechanical properties of mild low carbon and HSLA steels processed by thin slab casting and direct rolling. ISIJ Int., 2007, 47(8): 1204

[13] Xu G., Liu L., Chen Z., Jiang B., Guo F. Drawing properties of cold rolled sheets produced from thin-slab-casting-rolling hot strips. ISIJ Int., 2008, 48(9): 1225

[14] Xu G., Yang Y., Zhang X., Zhang H. Influence of annealing technology on drawing properties of cold sheets rolled with compact strip production hot bands. ISIJ Int., 2007, 47(12): 1767

[15] Li H., Han J., Pi H., Jiang Z., Wei D., Tieu A.K. Modeling texture development during cold rolling of IF steel by crystal plasticity finite element method. J. Univ. Sci. Technol. Beijing, 2008, 15(6): 696

[16] Hu H. The strain-dependence of plastic strain ratio (r _m value) of deep drawing sheet steels determined by simple tension test. Metall. Trans. A, 1975, 6(4): 945