| Ti 첨가 가속냉각형 고장력강의 용접열영향부 연화에 미치는 질소함량의 영향 |
| 방국수1,*,, 정호신2, 박찬2 |
1부경대학교 신소재시스템공학과
2부경대학교 재료공학과 |
| Effects of Nitrogen Content on the HAZ Softening of Ti-Containing High Strength Steels Manufactured by Accelerated Cooling |
| Kook-soo Bang1,*,, Ho-shin Jung2, Chan Park2 |
1Dept. of Materials System Eng., Pukyong National University, Busan 48547, Republic of Korea
2Dept. of Materials Sci. and Eng., Pukyong National University, Busan 48547, Republic of Korea |
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Received: 4 August 2016; Accepted: 31 August 2016. Published online: 3 March 2017. |
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| ABSTRACT |
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The effects of nitrogen content on the HAZ softening of Ti-containing high strength steels manufactured by accelerating cooling were investigated and interpreted in terms of the microstructures in the softening zone. Regardless of their content, all of the steels investigated showed a softened zone 9-10 mm wide. The minimum hardness in the zone, however, was different, with lower hardness in the higher nitrogen content steel. Microstructural observations of the steel showed that the amount of soft ferrite was increased in the zone with an increase of nitrogen content of the steel, suggesting that microstructural evolution in the HAZ is influenced by the nitrogen content. Measurements of TiN particles showed that the degree of particles coarsening in the HAZ was lower in the higher nitrogen content steel. Therefore, it is believed that finer TiN particles in the HAZ inhibit austenite grain growth more effectively, and lead to an accelerated ferrite transformation in higher nitrogen content steel, resulting in a higher amount of soft ferrite microstructure in the softened zone. |
| Keywords:
alloys, welding, microstructure, hardness test, HAZ softening |
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