Effects of Manganese and Carbon on the HAZ Microstructural Evolution in Titanium Oxide Steel

Bang, Kook-Soo

Journal of KWJS 2004;22(2):78-84.
Published online September 15, 2004.

[연구논문] 티타늄 산화물강 열영향부 조직변태에 미치는 망간 및 탄소의 영향

Effects of Manganese and Carbon on the HAZ Microstructural Evolution in Titanium Oxide Steel

Abstract

Effects of manganese and carbon on the HAZ micro structural evolution in 500㎫ grade titanium oxide steels were investigated. Micro structural evolution primarily depends on super cooling . When cooled at 3˚C/s in 0.15％C-1.5％Mn steels, grain boundary and Widmanstatten ferrite formed at 640and 620˚C, respectively, followed by competitive formation of acicular ferrite and upper bainite inside of grain at 580˚C. With an increase of manganese, degree of super cooling increased while critical cooling rate for the formation of grain boundary ferrite decreased. Consequently, the amount of acicular ferrite in HAZ was decreased in 2.0％Mn after initial increase in 1.0 and 1.5％Mn. Therefore, aptimum super cooling should be maintained to accelerate acicular ferrite formation in titanium oxide steels. Low carbon steel, 0.11％C-1.5％Mn, showed larger amount of acicular ferrite than higher carbon steel because of effectiveness of diffusionless transformation in low caron steel.