2004 Volume 90 Issue 10 Pages 812-818
The effect of Mn content on simulated heat affected zone toughness of large heat input welding in Ti-oxide bearing steel was examined. A simulated heat affected zone microstructure is classified into four regions: i) a microstructure mainly composed of fine-grained ferrite, ii) a mixed microstructure composed of coarse grain boundary ferrite, ferrite sideplate and intra-granular ferrite, iii) a microstructure mainly composed of intra-granular ferrite, and iv) a mixed microstructure composed of intra-granular ferrite and martensite-austenite constituent with varying Mn content and peak temperature. The best simulated heat affected zone toughness was shown when the microstructure was mainly composed of intra-granular ferrite in Mn content of 1.71%. The simulated HAZ toughness also had a good relationship with effective grain size for fracture defined as a maximum thickness of grain boundary ferrite and ferrite sideplate in the range of peak temperature from 1350 to 1450°C. The simulated heat affected zone toughness began to deteriorate due to the formation of martensite-austenite constituent even when the microstructure was mainly composed of intra-granular ferrite in Mn content of 1.95%.
