Influence of Nitrogen Content on Hot Ductility
of Nb-and B-added Ultra-low Carbon Steel
for Welded Cans
No.23 March 2018 - Special Issue on “Steel Sheet for Can-making”, “Steel Bar and Wire Rod” and “Slag Products”
Influence of Nitrogen Content on Hot Ductility of Nb-and B-added Ultra-low Carbon Steel for Welded Cans
TADA MasakiKOJIMA KatsumiNAGOSHI Masayasu
Abstract
The influence of nitrogen (N) content on the hot-ductility of combined niobium (Nb) and boron (B) added ultra low-carbon steel was investigated with use of the related commercial steel materials. Nb and B added ultra low-carbon steel in which nitrogen was 0.0048 mass% showed the bottom of ductility around 950℃ , which was slightly higher than the Ar3 transfor¬mation temperature. Reducing N content less than 0.0032 mass% improved the hot-ductility around the temperature of 950℃ . Both grain boundary ductile fracture and intragranular brittle fracture were observed in the fractured surface of the tested specimen. MnS, BN and AlN precipitates were observed at the grain boundaries, and the Nb (C, N) precipitates were observed in the ferrite matrix. These results suggest that the hot-ductility of combined Nb and B added ultra low-carbon steel is deteriorated by both the grain boundary ductile fracture dominated by the MnS, BN, AlN precipitates and the transgranular brittle fracture by the Nb (C, N) precipitates.
