12% Cr耐熱鋼の研究 (第7報) : 0.1% C-12% Cr耐熱鋼のδフェライトに及ぼすソーキングの影響

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0.1%C-12% Chromium heat resisting steel is being appreciated as steel for steam turbine blade etc. The uniformity of structure, among characteristics requested for blade material, is one of the most important nature as well as mechanical properties and creep rupture.Accordingly, micro segregation and Delta Ferrite are inclined to be one cause of fatigue rupture and materials having uniformed sorbite structure are requested.The present study is, following the report chiefly written about nature of materials (inner nature, mechanical properties, creep rupture) in from the 1st to 6th report, concerning improvement of structure and investigated about the rise and fall of Delta Ferrite, a big point in manufacturing 0.1%C-12% Chromium heat resisting steel mainly the effects of soaking treatment.As the results, it was found that uniform macrostructure with no segreagation and Delta Ferrite could be obtained under 1100-1200°C soaking, if was C 0.11-0.15% and Cr 11.5-12.0% and the growth of Delta Ferrite caused by temperature higher than 1200°C could be out by means of re-soaking of 1050-1200°C.It is needless to mention that the above written fact follow exactly as per the phase diagram.
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