DISSOLUTION BEHAVIOR OF NB-RICH PRECIPITATES DURING REHEATING OF MICROALLOYED STEEL HEAVY PLATES
Fábio Dian Murari, Antônio Adel dos Santos, André Luiz Vasconcellos da Costa e Silva, José María Rodriguez-Ibabe
The effect of reheating temperature of slabs on the dissolution of precipitates and mechanical properties of Ti-Nb
microalloyed steel was investigated in pilot scale. Transmission electron microscopy indicated a significant decrease in the
presence of precipitates formed during the solidification of the steel as the reheating temperature increased from 1100°C to
1200°C. With further temperature increase up to 1280°C no significant changes in size and shape of the precipitates were
observed. Together with the precipitates dissolution behavior, an increase in strength was observed with the elevation of
the reheating temperature up to 1200°C, due in part to the reprecipitation of fine Nb-rich precipitates during hot rolling.
When reheating at 1200°C the presence of deformed ferrite on the microstructure contributed to the additional increase
in strength. After reheating above 1200°C up to 1280°C, a decrease in strength of the rolled plates was observed. This
effect has been credited to the absence of deformed ferrite grains and to a small increase in the low angle grain boundaries
size. The results were in agreement with Thermo-Calc and Dictra simulations.
1 Jun HJ, Kang KB, Park CG. Effects of cooling rate and isothermal holding on the precipitation behavior during continuous casting of Nb-Ti bearing HSLA steels. Scripta Materialia. 2003;49(11):1081-1086.
2 Murari FD, Santos AA, Gusmão AMR, Pereda B, Lopez B, Rebellato MA. Heating rate effect on the precipitates jdissolution and mechanical properties of microalloyed steel plates. Rolling and Metal Forming Seminar. 2018;55(55):525-536.
3 Zheng S, Davis C, Strangwood M. Elemental segregation and subsequent precipitation during solidification of continuous cast Nb-V-Ti high-strength low-alloy steels. Materials Characterization. 2014;95:94-104.
4 Nishioka K, Ichikawa K. Progress in thermomechanical control of steel plates and their commercialization. Science and Technology of Advanced Materials. 2012;13:1-20.
5 Chen Z, Loretto MH, Cochrane RC. Nature of large precipitates in titanium-containing HSLA steels. Materials Science and Technology. 1987;3(10):836-844.
6 Carboni MC, Mesquita RA, Cruz EB, Fridman DP, Nogueira MAS. Characterization of precipitates in segregated regions of a Nb bearing API-X70 microalloyed steel. In: Proceedings of the 42nd ABM Steelmaking Seminar; 2011; Salvador, Brasil. São Paulo: ABM; 2011. p. 476-488.
7 Chakrabarti D, Davis C, Strangwood M. Development of bimodal grain structures in Nb-containing high-strength low-alloy steels during slab reheating. Metallurgical and Materials Transactions A, Physical Metallurgy and Materials Science. 2008;39(8):1963-1977.
8 Rodriguez-Ibabe JM. The role of microstructure in toughness behavior of microalloyed steels. Materials Science Forum. 1998;284-286:51-62.
9 Schiavo CP, Gonzalez BM, Santos AA, Marra KM. Influence of solubilization parameters: soaking temperature and time, on Tnr of microalloyed (Nb, V and Ti) steel. Tecnologica em Metalurgia, Materiais e Mineração. 2011;8(1):14-18.
10 Ding W, Stalheim D, Li S, Bai X, Jiang Z, Li J, et al. Research and development in the low temperature toughness of large diameter heavy wall X80 pipeline steel at Shougang Steel. In: Proceedings of the 9th International Pipeline Conference; 2012; Calgary, Alberta, Canada. New York: American Society of Mechanical Engineers; 2012. p. 249-255.
11 Borba EC, Castro CSB, Escobar DMP, Murari FD, Taiss EJM, Silva ALVC, et al. A study of the dissolution of precipitates during microalloyed steels reheating using computational thermodynamics. In: Anais do 72º Congresso Anual da ABM; 2017; São Paulo. São Paulo: ABM; 2017. p. 2054-2063.
12 Uranga P, Isasti N, Rodriguez-Ibabe JM, Stalheim D, Kendrick V, Frye B, et al. Optimized cost-effective production of structural hot rolled CSP coils through proper austenite conditioning. Proceedings of AISTech. 2017;2017:2975-2987.