| Co-Investigator(Kenkyū-buntansha) |
木村 勲 新日本製鐵, 中央研究本部第二技術研究所, 所長
YAMAZAKI Taketomo Tsuruoka Technical College, Department of Industrial Chemistry, Professor,, 工業化学科, 教授 (30166649)
SATOH Kazunori The Technological University of Nagaoka, Analysis Center,Assistent,, 分析計測センター, 助手 (20143828)
INOUE Yasunori The Technological University of Nagaoka, Analysis Center,Assistant Professor,, 分析計測センター, 助教授 (30016133)
上野 學 長岡技術科学大学, 機械系, 教授 (70134963)
UENO Manabu The Technological University of Nagaoka, Department of Mechanical Engineering, P
KIMURA Isao Nippon Steel Corporation, R & D Laboratories, <II> , Director.
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| Research Abstract |
The stable region of <gamma> at 800 --1,100゜C in the ternary Mn-Al-Fe system diagram and also the effect of aluminum on the stress-induced martensite transformation of the <gamma> phase at room temperature were determined. Solid solubility limit of aluminum in <gamma> -Mn-Fe solid solution at 1,000゜C increases with increasing manganese contents and reach the limits of 5.5% (20%Mn) and 7.5% (30%Mn) in aluminum content. The addition of aluminum to <gamma> -Mn-Fe alloys supresses the <epsilon> transformation by decreasing Ms point of the alloys. The <gamma> -> <epsilon> -> <alpha> ' and <gamma> -> <alpha> ' transformations in the 20%Mn- 0 --4%Al-Fe alloys are promoted by deformation. Initial stages of deformation give birth to the <gamma> -> <epsilon> transformation and <gamma> ->twins formation in the 20%Mn-1.7%Al-Fe alloy and in the 20%Mn-4.4%Al-Fe alloy, respectively. The <gamma> -> <gamma> -twins formation in the 30%Mn-0 --4%Al-Fe alloys are accelerated by the lowering of temperature,
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which result in the increase in elongation, especially at the lower temperatures. Thus, even in the austenitic alloys, remarkable change of the mechanical properties with the contents of manganese and aluminum appears, showing n values of 33Mn-7Al-0.5C-0.05Si(AS) and 30Mn-10Al-1C-0.05Si(HD) to be 0.3 and 0.1. Next, other properties of the alloys, such as corrosion resistance, high temperature oxidation resistance, hot corrosion resistance, press formablity, and weldability, as well as productivities as hot and cold rolling ability were investigated. The results showed that the sheet steels have excellent characteristics. Finally, three aus-tenitic alloys were selected as candidates; AS,HD, and 30Mn-10Al-1 C-0.7Si(HF), and prepared by melting in a large scale and processing in usual procedures as Ni-Cr steels. Bright annealed sheets were evaluated for the properties mentioned above. Among them, only hot workability, weldability, and corrosion resistance were rather worse than those of SUS 304. Corrosion resistance was improved by surface treatments such as bright annealing, ion nitriding, and gas nitriding. Corrosion resistance of the gas nitrided surface against 1 N <H_2> <SO_4> solution was almost equal to that of SUS 304. Other properties were satisfied to meet the requirements equal to Ni-Cr aus-tenitic stainless steels. Less
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