원자로압력용기용 SA508 Gr.4N Ni-Mo-Cr계 저합금강 용접열영향부의 용접후열처리에 따른 미세조직과 기계적 특성 평가 (Evaluation of Microstructure and Mechanical Properties on Post-Weld Heat Treatment in the Heat Affected Zone of SA508 Gr.4N Ni-Mo-Cr Low Alloy Steel for Reactor Pressure Vessel)

서지정보

· 발행기관 : 대한금속·재료학회
· 수록지 정보 : 대한금속·재료학회지 / 47권 / 3호 / 139 ~ 146페이지
· 저자명 : 이윤선, 김민철, 이봉상, 이창희

초록

The heat-affected zone (HAZ) of SA508 Gr.4N Ni-Mo-Cr low alloy steel, which has higher Ni and
Cr contents than SA508 Gr.3 Mn-Mo-Ni low alloy steel, was investigated on the microstructure and
mechanical properties. The HAZ was categorized into seven characteristic zones (CGCG, FGCG, ICCG, SCCG,
FGFG, ICIC and SCSC-HAZ) according to the peak temperature from the thermal cycle experienced during
multi-pass welding. Post Weld Heat Treatment (PWHT) was conducted in the temperature range of
550~610˚C for 30 hours to evaluate the effect of PWHT conditions on the microstructure and mechanical
properties. Before PWHT, CGHAZ and FGFGHAZ showed high yield strength (YS) ranging from 1000 to 1250
MPa, while YS of SCSCHAZ decreased from 607 MPa (observed for base metal) to 501 MPa. The Charpy
impact energies of sub-HAZs fell below 100J at −29˚C, except in the SCSCHAZ. By applying PWHT to sub-
HAZ specimens, YS decreased as the PWHT temperature increased. In the case of CGHAZs and FGFGHAZ
heat-treated at 610˚C, YS dropped drastically to the range of 654~686 MPa. From the Charpy impact test,
the upper-shelf energy (USE) increased to approximately 250J and Index temperature (T68J) decreased below
−50˚C. Specifically, in FGFG, ICIC and SCSC-HAZ, T68J was below −110, which was lower than the case of
base metal.

영어초록

The heat-affected zone (HAZ) of SA508 Gr.4N Ni-Mo-Cr low alloy steel, which has higher Ni and
Cr contents than SA508 Gr.3 Mn-Mo-Ni low alloy steel, was investigated on the microstructure and
mechanical properties. The HAZ was categorized into seven characteristic zones (CGCG, FGCG, ICCG, SCCG,
FGFG, ICIC and SCSC-HAZ) according to the peak temperature from the thermal cycle experienced during
multi-pass welding. Post Weld Heat Treatment (PWHT) was conducted in the temperature range of
550~610˚C for 30 hours to evaluate the effect of PWHT conditions on the microstructure and mechanical
properties. Before PWHT, CGHAZ and FGFGHAZ showed high yield strength (YS) ranging from 1000 to 1250
MPa, while YS of SCSCHAZ decreased from 607 MPa (observed for base metal) to 501 MPa. The Charpy
impact energies of sub-HAZs fell below 100J at −29˚C, except in the SCSCHAZ. By applying PWHT to sub-
HAZ specimens, YS decreased as the PWHT temperature increased. In the case of CGHAZs and FGFGHAZ
heat-treated at 610˚C, YS dropped drastically to the range of 654~686 MPa. From the Charpy impact test,
the upper-shelf energy (USE) increased to approximately 250J and Index temperature (T68J) decreased below
−50˚C. Specifically, in FGFG, ICIC and SCSC-HAZ, T68J was below −110, which was lower than the case of
base metal.

참고자료

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