Effect of titanium content on the refinement of coarse columnar austenite grains during the solidification of peritectic steel

Abstract

The effect of titanium content on the refinement of austenite grain size in as-cast peritectic carbon steel was investigated by fast directional solidification experiments with simulating the solidification and growth of surface and subsurface austenite in continuously cast slabs. Transmission electron microscope (TEM) and scanning electron microscope (SEM) were used to analyze the size and distribution of Ti(C,N) precipitates during solidification. Based on these results, the pinning pressure of Ti(C,N) precipitates on the growth of coarse columnar grains (CCGs) was studied. The results show that the austenite microstructure of as-cast peritectic carbon steel is mainly composed of the regions of CCGs and fine columnar grains (FCGs). Increasing the content of titanium reduces the region and the short axis of the CCGs. When the content of titanium is 0.09wt%, there is no CCG region. Dispersed microscale particles will firstly form in the liquid, which will decrease the transition temperature from FCGs to CCGs. The chain-like nanoscale Ti(C,N) will precipitate with the decrease of the transition temperature. Furthermore, calculations shows that the refinement of the CCGs is caused by the pinning effect of Ti(C,N) precipitates.

Keywords

peritectic steel / grain refinement / coarse columnar grain / titanium carbonitride / pinning pressure

References

[1] Ohno M, Tsuchiya S, Matsuura K. Microstructural features and formation processes of as-cast austenite grain structures in hypoperitectic carbon steels. ISIJ Int., 2015, 55(11): 2374.

[2] Tasi H T, Yin H, Lowry M, Morales S. Analysis of transverse corner cracks on slabs and countermeasures. Iron Steel Technol., 2006, 3, 23

[3] Mintz B, Arrowsmith JM. Hot-ductility behaviour of C−Mn−Nb−Al steels and its relationship to crack propagation during the straightening of continuously cast strand. Met. Technol., 1979, 6(1): 24.

[4] H. Yasuda, T. Suga, K. Ichida, T. Narumi, and K. Morishita, In situ observation of austenite coarsening induced by massive-like transformation during solidification in Fe−C alloys, IOP Conf. Ser.: Mater. Sci. Eng., 861(2020), No. 1, art. No. 012051.

[5] Azizi G, Thomas BG, Asle Zaeem M. Review of peritectic solidification mechanisms and effects in steel casting. Metall. Mater. Trans. B, 2020, 51(5): 1875.

[6] Pottore NS, Garcia CI, DeArdo AJ. Interrupted and isothermal solidification studies of low and medium carbon steels. Metall. Trans. A, 1991, 22(8): 1871.

[7] Maruyama T, Matsuura K, Kudoh M, Itoh Y. Peritectic transformation and austenite grain formation for hyper-peritectic carbon steel. Tetsu-to-Hagane, 1999, 85(8): 585.

[8] Yoshida N, Umezawa O, Nagai K. Analysis on refinement of columnar γ grain by phosphorus in continuously cast 0.1 mass% carbon steel. ISIJ Int., 2004, 44(3): 547.

[9] Tsuchiya S, Ohno M, Matsuura K, Isobe K. Formation mechanism of coarse columnar γ grains in as-cast hyperperitectic carbon steels. Acta Mater., 2011, 59(9): 3334.

[10] Ohno M, Tsuchiya S, Matsuura K. Formation conditions of coarse columnar austenite grain structure in peritectic carbon steels by the discontinuous grain growth mechanism. Acta Mater., 2011, 59(14): 5700.

[11] Kencana S, Ohno M, Matsuura K, Isobe K. Effects of Al and P additions on as-cast austenite grain structure in 0.2 mass% carbon steel. ISIJ Int., 2010, 50(12): 1965.

[12] Tsuchiya S, Ohno M, Matsuura K, Isobe K. Effects of Cr addition on coarse columnar austenite structure in as-cast 0.2 mass% carbon steel. ISIJ Int., 2010, 50(12): 1959.

[13] Wang YL, Chen YL, Yu W. Effect of Cr/Mn segregation on pearlite-martensite banded structure of high carbon bearing steel. Int. J. Miner. Metall. Mater., 2021, 28(4): 665.

[14] Medina SF, Chapa M, Valles P, Quispe A, Vega MI. Influence of Ti and N contents on austenite grain control and precipitate size in structural steels. ISIJ Int., 1999, 39(9): 930.

[15] Wan XL, Wu KM, Huang G, Wei R, Cheng L. In situ observation of austenite grain growth behavior in the simulated coarse-grained heat-affected zone of Ti-microalloyed steels. Int. J. Miner. Metall. Mater., 2014, 21(9): 878.

[16] Feng B, Chandra T, Dunne DP. Effect of alloy nitride particle size distribution on austenite grain coarsening in Ti and Ti−Nb bearing HSLA steels. Mater. Forum, 1989, 13(2): 139

[17] Vaz Penna R, Bartlett LN, O’Malley R. Influence of TiN additions on the microstructure of a lightweight Fe−Mn−Al steel. Int. J. Metalcast., 2020, 14(2): 342.

[18] A. Graux, S. Cazottes, D. de Castro, D. San Martín, C. Capdevila, J.M. Cabrera, S. Molas, S. Schreiber, D. Mirković, F. Danoix, M. Bugnet, D. Fabrègue, and M. Perez, Precipitation and grain growth modelling in Ti−Nb microalloyed steels, Materialia, 5(2019), art. No. 100233.

[19] Wei R, Shang CJ, Wu KM. Grain refinement in the coarse-grained region of the heat-affected zone in low-carbon high-strength microalloyed steels. Int. J. Miner. Metall. Mater., 2010, 17(6): 737.

[20] Ohno M, Matsuura K. Refinement of as-cast austenite microstructure in S45C steel by titanium addition. ISIJ Int., 2008, 48(10): 1373.

[21] Tsuchiya S, Ohno M, Matsuura K. Transition of solidification mode and the as-cast γ grain structure in hyperperitectic carbon steels. Acta Mater., 2012, 60(6–7): 2927.

[22] Maehara Y, Yasumoto K, Sugitani Y, Gunji K. Effect of carbon on hot ductility of as-cast low alloy steels. ISIJ Int., 1985, 25(10): 1045.

[23] Gui LT, Long MJ, Zhang HH, Chen DF, Liu S, Wang QZ, Duan HM. Study on the precipitation and coarsening of TiN inclusions in Ti-microalloyed steel by a modified coupling model. J. Mater. Res. Technol., 2020, 9(3): 5499.

[24] Huang Y, Liu WN, Zhao AM, Han JK, Wang ZG, Yin HX. Effect of Mo content on the thermal stability of Ti−Mo-bearing ferritic steel. Int. J. Miner. Metall. Mater., 2021, 28(3): 412.

[25] Kato T, Ito Y, Kawamoto M, Yamanaka A, Watanabe T. Prevention of slab surface transverse cracking by microstructure control. ISIJ Int., 2003, 43(11): 1742.

[26] Andersen I, Grong Ø. Analytical modelling of grain growth in metals and alloys in the presence of growing and dissolving precipitates—I. Normal grain growth. Acta Metall. Mater., 1995, 43(7): 2673.

[27] G.E. Pellissier and S.M. Purdy, Stereology and Quantitative Metallography, American Society for Testing and Materals, Easton, 1972.