12Cr 강의 이동 화염경화 공정 특성

• Published in: Biuletyn Uniejowski Vol. 39; no. 2; pp. 49 - 56
• Main Authors: 김광호(Gwang-Ho Kim), 이민구(Min-Ku Lee), 김경호(Kyeong-Ho Kim), 김흥회(Whung-Whoe Kim), 이창규(Chang-Kyu Rhee), 김길무(Gil-Mu Kim)
• Format: Journal Article
• Language: Korean
• Published: 한국표면공학회 2006
• Subjects: 기계공학; Steam turbine blade; Heat treatment; 12Cr steel; Residual stress; Flame hardening; Heart treatment
• ISSN: 1225-8024; 2299-8403; 2288-8403

In this study, the movable flame hardening process of 12Cr steel for a uniform hardness and desirable residual stress have been investigated. For this, the temperature cycles have been controlled accurately as a function of the three processing variables, the flame intensity $I_f$, the scanning velocity $V_s$, and the initial flame holding time $t_h$, where the standard surface temperature $T_{s,\;max}$, was maintained at $960^{\circ}C$. The optimized conditions were $V_s=0.68mn/s\;and\;t_h=67sec$ for the $C_3H_8:O_2\;=\;5:20l/min,\;V_s=0.80mm/s$ and $t_h=56sec$ for the $C_3H_8:O_2=6:24l/min,\;V_s=1.01mm/s\;and\;t_h=48sec$ for the $C_3H_8:O_2=7:28l/min,\;and\;V_s=1.15mm/s$ and $t_h=39sec$ for the $C_3H_8:O_2$=8:32 l/min. The optimally flame-hardened surface exhibited uniform distributions of the hardness and residual compressive stress over the treated area with moderate levels of $470{\sim}490HV_{0.2}$in hardness and $-300{\sim}-450MPa$ in residual stress, which were acceptable on the basis of the acceptance criteria of Siemens AG-KWU and GE Power Generation Engineering.