• Proceedings of the Materials Research Society of Korea Conference
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• 1992.05a
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• pp.2-2
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• 1992

• Journal of the Korean Society of Industry Convergence
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• v.25 no.3
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• pp.325-331
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• 2022

In this study, austenitic 316L stainless steel was rolled at three different temperatures (100℃, -50℃, -196℃) at five rolling degree (0, 16, 33, 50, 66 and 80%). The rolled specimen was examined for micro structure, and the volume fraction and mechanical properties were evaluated. In particular, the rolling specimen detected the elastic wave generated in tensile and investigated the relationship between the rolling degree and the dominant frequency. As the rolling degree increased, austenite decreased and martensite increased. The volume fraction of martensite more increased at lower temperatures, but increased rapidly at the rolling degree of 50% of all rolling temperature. Tensile strength increased rapidly with the increase of the rolling degree, and was larger at lower temperatures. The elongation decreased sharply to the rolling degree of 33%, but decreased gently thereafter. The dominant frequency highly appeared as the volume fraction of martensite increased, but the dominant frequency was higher at the low temperature rolling temperature. A similar trend was also observed in the relationship between tensile strength and dominant frequency.

• Journal of the Korean Society for Heat Treatment
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• v.20 no.6
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• pp.323-328
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• 2007

This study has been investigated the effect of high temperature gas nitriding (HTGN) heat treatment of STS 444 (18Cr-0.01Ni-0.01C-0.2Nb) ferritic stainless steel in an atmosphere of nitrogen gas at the temperature range between $1050^{\circ}C\;and\;1150^{\circ}C$. The surface layer was changed into martensite and austenite with the nitrides of NbCrN by HTGN treatment. Due to the precipitation of nitrides and matrensite formation, the hardness of the surface layer showed $400Hv{\sim}530Hv$. The nitrogen concentration of the surface layer appeared as 0.05%, 0.12% and 0.92%, respectively, at $1050^{\circ}C,\;1100^{\circ}C\;and\;1150^{\circ}C$. When the nitrogen is permeated from surface to interior, Nb and Cr, which have strong affinities with nitrogen, also move from interior to surface. Therefore it is considered that this counter-current of atoms promotes the formation of NbCrN at the surface layer.