NIE Yihong
,
HUI Weijun
,
FU Wantang
,
WENG Yuqing
钢铁研究学报(英文版)
The delayed fracture behavior of mediumcarbon high strength spring steel containing different amounts of boron (0000 5%, 0001 6%) was studied using sustained load delayed fracture test. The results show that delayed fracture resistance of boron containing steels is higher than that of conventional steel 60Si2MnA at the same strength level and it increases with the increase of boron content from 0000 5% to 0001 6%. The delayed fracture mode is mainly intergranular in the boron containing steels tempered at 350 ℃, which indicates that the addition of boron does not change the fracture character. However, the increase of boron content enlarges the size of the crack initiation area. Further study of phase analysis indicates that most boron is in solid solution, and only a very small quantity of boron is in the M3(C, B) phase.
关键词:
boron;delayed fracture resistance;mediumcarbon high strength spring steel
LIU Qingyou
,
DENG Suhuai
,
SUN Xinjun
,
DONG Han
,
WENG Yuqing
钢铁研究学报(英文版)
Hot deformation processing was designed to study the effects of niobium (Nb) on DIFT. A prestrain of 051 at 880 ℃ for different isothermal time was used for adjusting the deformed austenite constitution and Nb existing state, followed by a secondary heavy deformation at 780 ℃ for inducing the ferrite transformation. The volume fraction and grain size of deformation induced ferrite (DIF) obtained at different isothermal time between double hits were investigated. It was found that Nb dissolved in austenite is adverse to DIFT; however, the precipitation of Nb is beneficial to DIFT. As Nb plays the role in the conventional TMCP, Nb retards the recrystallization of deformed austenite and enhances the deformation stored energy in the multipass deformation, and in result, Nb promotes DIFT.
关键词:
niobium;precipitation;recrystallization;deformation induced ferrite transformation
