Contribution to the Modelling of Processes Controlling the Acicular Ferrite (AF) Formation in C-Mn Steels

• Autorzy: Mazancová E. , Jonšta Z. , Mazanec K.
• Konferencja: International Conference Computer Simulation in Machine Design - COSIM 2006 (11 ; 2006 ; Krynica Zdrój, Poland)
• Języki publikacji: EN

Abstrakty

EN

Due to special morphology, AF microstructure makes possible to obtain a very favourable combination of mechanical properties (strength, ductility and toughness). The significant parameter is the deflection mechanism limiting cleavage crack propagation. Although the nucleation role of fine special non-metallic inclusions as inoculants controlling the austenite (A)-decomposition into ferrite has been described in great number of works, the comprehensive mechanism of these processes has not been developed. Due to large variety of non-metallic particles acting as inoculants in above considered transformation process, this solution is not facile. The nucleation potency of individual phases comprising complex inclusions has not been assessed so far. In the present contribution the investigation will be devoted to the finding of model being able to describe the nucleating behaviour of some complex inclusions based on manganese - silicate (MnO-SiO2) and on the nucleating effect of Mg-addition (MgO) to the basic chemical constitution resulting from deoxidization with Mn/Si/Ti. Among considered mechanism as the most perspective one could be held the formation of Mn-depleted zone being the nucleation site for intragranular A-decomposition into ferrite phase. It has been proposed this zone is formed around inclusion by the subsequent MnS nucleation on it. This process is accompanied with the subsequent Mn-diffusion running in the steel matrix to the MnS-nuclei. The following conclusions can be determined from the achieved results in investigated steel types. The nucleation potency of some inclusions complex represents a decisive initiation parameter in decomposition of A into AF. It has been established the higher density number of dispersed fine intragranular particles (0.5-2.0 µm) is very effective in the refinement of ferrite plates by AF nucleation. The non-metallic inclusions type participating in the considered nucleation process is determined by steel deoxidization. Precipitation of MnS on primary inclusions (investigated influence of Mn/Si and Mn/Si/Ti) has been analyzed. For both examples the same physical metallurgical characteristics leading to the formation of Mn-depleted zone and simultaneously realized MnS nucleation on applied non-metallic inclusions have been found. In case of AF nucleation on inclusions after Mg addition the mechanism of Mn-depleted zone has been also confirmed. The mechanism of AF formation in connection with Mn-depleted zone existence around the primary steel inclusions accompanied with MnS formation has been analyzed in detail. This complex mechanism can be considered as a very attractive model making possible to predict the AF nucleability in austenitic matrix.

Słowa kluczowe

EN

physical metallurgy; acicular ferrite; steel; manganese steel; nucleation

PL

metaloznawstwo; ferryt iglasty; stal; stal manganowa; zarodkowanie

• Wydawca: Oficyna Wydawnicza Politechniki Warszawskiej
• Czasopismo: Machine Dynamics Problems
• Rocznik: 2006
• Tom: Vol. 30, No. 4
• Strony: 60--67
• Opis fizyczny: Bibliogr. 6 poz., rys., wykr.

Twórcy

autor

Mazancová E.

autor

Jonšta Z.

autor

Mazanec K.

• Technical University of Ostrava. Faculty of Metallurgy and Material Engineering,

Bibliografia

• Byun, J. S., Shim, H., Cho, Y. W., Lee, D. N., 2003, Non-metallic inclusions and intragranular nucleation of ferrite in Ti-killed C-Mn steel, Acta Materalia, 51, 1593-1606.
• Chang, C. H., Jung, I. H., Park, S. C., Kim, H. S., Lee, H. G., 2005, Effect of Mg on the evolution of non-metallic inclusions in Mn-Si-Ti deoxidized steel during solidification; Experiments and thermodynamic calculations, Ironmaking and Steelmaking, 32, 251-257.
• Kim, H. S., Chang, Ch. H., Lee, H. G., 2005, Evolution of inclusions and resultant microstructural change with Mg addition in Mn/Si/Ti deoxidized steels, Scripta Materialia, 53, 1253-1258.
• Kim, H. S., Lee, H. G., Oh, K. S., 2001, MnS precipitation in association with manganese silicate inclusions in Si/Mn deoxidized steel, Metal. Mater. Trans. A, 32A, 1519-1525.
• Kimura, S., Nakajima, K., Mizoguchi, S., 2001, Behaviour of aluminia magnesia complex inclusions and magnesia inclusions on the surface of molten low-carbon steels, Metal. Mater. Trans. B, 32B, 79-85.
• Yamamoto, K., Hasegawa, T., Takamura, J., 1996, Effect of boron on intragranular ferrite formation in Ti oxide bearing steel, ISIJ Internat., 36, 80-86.