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Effect of Austenitizing Temperature on Bainite Transformation in the Fe-0.88C-1.45Si-0.95Cr-0.37Mn Steel

Author: HeKun
Tutor: LiuQingSuo
School: Tianjin University of Technology
Course: Materials Physics and Chemistry
Keywords: Austenitizing temperature Atypical slats wispy upper bainite Atypical acicular lower bainite Fine structure Bainite transformation
CLC: TG111.5
Type: Master's thesis
Year: 2010
Downloads: 74
Quote: 0
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Abstract


In this paper, the vacuum induction furnace Fe-0.88C-1.45Si-0.95Cr-0.37Mn as experimental steel. Using optical and transmission electron microscopy microstructure observation, X-ray diffraction analysis and combination of hardness, impact toughness and tensile strength testing different temperature austenitizing treatment of experimental steel bainite microstructure state and mechanical properties the impact of the law. It was found that the experiment of steel in the Acm near the lower temperature austenitizing cooled to 300 ℃ isothermal formation of bainite lath bundle, while away from the high temperature of the Acm austenitizing cooled to 300 ° C isothermal organization only acicular lower bainite experimental steel austenitizing Acm near the lower temperature, even if the sample is not to stay in the upper bainite transition area, remained very prominent on the bainite transformation organizing feature and experimental austenitizing of steel in the the Acm near lower temperature (such as 850 ° C or 880 ℃) cooled to 300 ° C short-time temperature (This article 20min or less) to form a lattice expansion on bainite, while away from the Acm a high temperature (such as 950 ℃) austenitization temperature was cooled to 300 ℃ short (within this article 20min) also forming a lattice expansion of lower bainite, the degree of expansion of the lattice is higher than the upper bainite, but lower than the martensite. Narrow Microstructure observation showed that, the experimental steels short bainite transformation stage (As used herein 300 ℃ isothermal 20min less) formed in the upper and lower bainite the slats have similar morphology by oversaturation The solid solution of carbon atoms in the ferrite phase constituted the bainitic ferrite alkylene structure also are dislocations, can be called atypical, lower bainite; atypical between bainite article under intersect the role of bainite boundary morphology can lead to significant changes, atypical on the intersection between the role of the bainite Article no significant effect on the morphology of the bainite bar. Experimental results show that the growth of atypical bainite containing cut disguised become stars, but atypical growth lower bainite containing cut disguised become stars projecting, having cut the growth of atypical upper bainite disguised Variable The ingredient is weak, unfit completely the martensitic transformation theoretical characterization of the experimental steel atypical bainitic transformation. Experimental steel with atypical upper bainite lath bundles organizational structure gives the material excellent toughness, but considering the strength and toughness, with a needle-like structure of the atypical lower bainite can give superior material strong / toughness.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallurgy ( Physical Metallurgy ) > Physics of metals > Metal solid -phase structure and phase transition
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