Silicon influence on the microstructure formation at cooling rates lower than the critical rate

• Autorzy: Pacyna J.
• Języki publikacji: EN

Abstrakty

EN

Purpose: On the bases of fundamental research [1], on the silicon influence on the kinetics of phase transformation of undercooled austenite in model ferrous alloys with carbon of a weak background of other alloying elements, it was found that up to the Si content of 1 mass % the steel hardenability decreases. The time before the start of the ferrite precipitation decreases as well as the time before the start of the pearlite and bainite formation. On the other hand in model ferrous alloys with carbon of a strong background of other elements, also in the range to app. 1 Si %, the time before the start of the ferrite precipitation and bainite formation is insignificantly prolonged (hardenability increases minimally), while the location of the start of the pearlitic transformation remains practically the same. This observation, being a part of designing the ferrous alloys structure, can be successfully utilised, among others, in steels for working rolls for plates cold-rolling. Due to that in these expensive tools we are able to soften the influence of the structural notch, which is formed - at a certain depth - by the upper bainite layer, in steels without silicon additions. Design/methodology/approach: Dilatometric investigations were performed using a DT 1000 dilatometer of a French company Adamel. Findings: An addition of 1 mass % of silicon causes a gradual vanishing of the steel bainitisation, being the bainite slipping in ‘under pearlite’, due to which the austenite, at continuous cooling, will be at first transformed into pearlite, on its grain boundaries, and only later - inside grains - into bainite. Even if it is the upper bainite its location inside grains, within the pearlite envelope, is less dangerous for the crack resistance than its location on grain boundaries. Research limitations/implications: These observations can be utilized for steels in which the bainitic transformations are shifted in the direction of shorter times (e.g. in chromium - molybdenum steels). Especially when this is the upper bainite known for its low crack resistance. Practical implications: Due to this work in expensive tools we are able to soften the influence of the structural notch, which is formed - at a certain depth - by the upper bainite layer, in steels without silicon additions. Originality/value: Details descriptions of influence of the Si content on the kinetics of phase transformations during cooling in model ferrous carbon alloys with a weak background and also strong background of other alloying elements.

Słowa kluczowe

EN

metallic materials; hardening; phase transformations; microstructure formation

• Wydawca: International OCSCO World Press
• Czasopismo: Journal of Achievements in Materials and Manufacturing Engineering
• Rocznik: 2012
• Tom: Vol. 54, nr 2
• Strony: 178--184
• Opis fizyczny: Bibliogr. 16 poz., rys.

Twórcy

autor

Pacyna J.

• Faculty of Metals Engineering and Industrial Computer Science, AGH University of Science and Technology, Al. Mickiewicza 30, 30-059 Kraków, Poland

Bibliografia

• [1] M. Strach, The structure and properties of silicon steels investigated on the model alloys of different content of silicon and carbon, PhD Thesis, University of Science and Technology (AGH), Cracow, 1995.
• [2] J. Pacyna, Retained austenite in the cracking process of steel on the working rolls of the cold sheet rolling mill, Steel Research 63/11 (1992) 500-503.
• [3] J. Pacyna, A. Mazur, Einfluss des Molybdans auf die Zähigkeit von Schnellarbeitsstahlen, Archiv für das Eisenhüttenwesen 53/4 (1982) 151-156 (in German).
• [4] J. Pacyna, The effect of molybdenum on the transformations in the matrix of high-speed steels during austenitizing and quenching, Archiv fur das Eisenhuttenwesen 55/6 (1984) 291-298.
• [5] J. Pacyna, The effect of molybdenum on the transformations in the quenched matrix of high-speed steels during tempering, Archiv für das Eisenhüttenwesen 55/7 (1984) 325-330.
• [6] A. Mazur, Nguyen-Cong Van, J. Pacyna, The fracture toughness of structural bainitic steel, Proceedings of the Conference VIII Hüttenmnnischen Materialprüfertagungen II, Balaton Szeplak, 1975, 595-602.
• [7] J. Pacyna, A. Jędrzejewska-Strach, The effect of manganese on the kinetics of phase transformation of austenite in structural steels, Proceedings of the 14th International Scientific Conference on Advanced Materials and Technologies, Gliwice-Zakopane, 1995, 341-344.
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• [9] J. Pacyna, A. Jędrzejewska-Strach, The effect of carbon on structure and properties of steels with silicon in the annealed state, Archives of Metallurgy 39/1 (1994) 53-69.
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• [16] J. Pacyna, Designing of chemical compositions of alloy steels, University of Mining and Metallurgy (AGH), Cracow, 1997 (in Polish).