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β-열처리시 Nb 첨가량과 냉각속도가 Zr 합금의 상변태에 미치는 영향
최병권 ( B. K. Choi ),김현길 ( H. G. Kim ),정용환 ( Y. H. Jeong ) 한국열처리공학회 2004 熱處理工學會誌 Vol.17 No.5
N/A Zr-xNb alloys (x = 0.2, 0.8, 1.5 wt.%) were prepared to study the characteristics of the phase transformation in Zr-Nb system. The samples were heat treated at 0-temperature (1020℃) for 20 min and then cooled with different cooling rate. The microstructures of the specimens having the same compositions were changed with cooling rate and Nb content. The Widmanstatten structure was observed on the furnace-cooled sample. The relationship between α-Widmansta¨tten and β-phase was the {0001}α//{110}β, <112 ̄0>//<111>. The β-phase in Widmansta¨tten structure of Zr-Nb alloys containing Nb more than solubility limit was identified as β_(zr) phase which was a stable phase at high temperature. In the water quenched samples, two kinds of martensite structures were observed depending on the Nb-concentration. The lath martensite was formed in Zr-0.2, 0.8 wt.% Nb alloys and the plate martensite having twins was formed in Zr-1.5 wt.% Nb alloy.
The Construction of the Harmony and the Heritage Jackets for the Santa Ynez Unit
B. K. Choi(崔秉權) 한국해양공학회 1987 韓國海洋工學會誌 Vol.1 No.2
現代 重工業(株)은 1985년 ‘7월 15얼자로 美國 EXXON社로푸더 水深 約 366m인 미국 California 연안에 설치될 海上 platform 2基를 收注하여, 現在 가장 어려운 공정인 roll-up을 완료하였으며, 제작공정 93%을 達成하여 1988년 4월 loadout을 目標로 순조롭게 제작 進行中에 있다. 정차 深海에서 oil을 採取하여야 하는 추세로 볼 때, 本 공사의 成功은 海洋 産業 分野의 새로운 움직임에 對備한 準備를 완료시킨 凱歌라고도 볼 수 있다. 이에 本 EXXON 工事를 紹介함으로써 우리나라의 해양 산업의 現況을 이해하는데 도움이 되고자 한다.
이명호,김준환,최병권,정용환,Lee M. H.,Kim J. H.,Choi B. K.,Jeong Y. H. 한국재료학회 2004 한국재료학회지 Vol.14 No.10
To study the dynamic strain aging behavior of Zr-0.4Sn-1.5Nb-0.2Fe sample tube for nuclear fuel cladding in the range of pressurized water reactor (PWR) operation temperature, the tensile tests of the tube specimens, which had been finally heat-treated at $470^{\circ}C\;and\;510^{\circ}C$, had been carried out with the strain rate $1.67{\times}10^{-2}/s\;and\;8.33{\times}10^{-5}/s$ at the various temperatures from room temperature to $500^{\circ}C$. It was observed that the elongation of the specimens got shortened as the temperature increased from $200^{\circ}C\;to\;340^{\circ}C$. The specimens that were finally heat-treated at $470^{\circ}C$ showed a plateau more remarkably on the plot of yield strength-temperature than those heat-treated at $510^{\circ}C$. In the range of $310\sim400^{\circ}C$, the strain rate sensitivity of the specimens finally heat-treated at $510^{\circ}C$ was $30.4\%\sim33.7\%$ lower but the work hardening exponent index of the specimens was a little higher than that without dynamic strain aging effect.
논문 : 부식환경 ; 알칼리 수용액에서 Zr 합금의 산화막 성장기구
정용환 ( Y. H. Jeong ),백종혁 ( J. H. Baek ),김선재 ( S. J. Kim ),김경호 ( K. H. Kim ),최병권 ( B. K. Choi ),방제건 ( J. G. Bang ) 대한금속재료학회 ( 구 대한금속학회 ) 1998 대한금속·재료학회지 Vol.36 No.7
The autoclave corrosion test was performed on the zirconium alloys in various aqueous solutions of LiOH, NaOH, KOH, RbOH, and CsOH, The oxide growth mechanism at metal-oxide interface was evaluated using SEM on the samples which were prepared to have an equal oxide thickness at pre-transition regime and post transition regime. At a low concentration (4.3 mmol), the corrosion rate was gradually decreased as the ionic radius of cation increased. However. at a high concentration (32.5 mmol). the corrosion rate was significantly accelerated in LiOH solution and slightly in NaOH solution. The morphologies and the growth rates of the oxides at metal-oxide interface were dependent on the ionic radius of cation even if the samples have an equal oxide thickness in LiOH, NaOH, and KOH, The grain orientation in Zr matrix also controlled the growth rates and the morphologies of the oxides. Therefore. It is considered that the oxide growth mechanism of Zr alloys can be controlled by the cation incorporation into zirconium oxide.