Effects of sulphur on hot ductility of low-carbon steel austenite

Hot ductility of TWIP steels

“…Other effects of increasing the strain rate include the observed decrease in the extent of grain boundary sliding [23] and precipitate coarsening [60]. The latter is presumably due to the higher dislocation densities, which can increase the pipe diffusion rates.…”

“…There are two instances when an increase in strain rate has been found to yield worse ductility [60,62]. However, in both these cases this occurred at high strain rates such as 10 -1~1 0 -2 s -1 and is therefore not applicable to typical tensile test strain rates.…”

“…However, in both these cases this occurred at high strain rates such as 10 -1~1 0 -2 s -1 and is therefore not applicable to typical tensile test strain rates. In one case, the steel contained unstable precipitates such as FeMn sulphides, so that lower strain rates allowed for rapid coarsening of inclusions so they were not able to pin austenite grain boundaries [60]. In the other instance, the high strain rate resulted in there being insufficient time for recovery or dynamic recrystallisation processes to occur and so ductility can be impaired [62].…”

Effect of High Temperature Deformation on the Hot Ductility of Nb Microalloyed Steel

“…[66] The surface cracking during the pro cess of continuous casting or the direct rolling is mainly caused by the precipitation of carbonitrides or sulfides or by the segregation of impurity atoms to the austenite grain boundaries in the temperature range from austenite to austenite/ferrite duplex phase region, accompanying the intergranular fracture of austenite. [1,30,37,50,78,96,100,101] Such ductility, as explained before, has been weIl known to depend largely on the grain size and to decrease inversely proportional to the initial grain size. Maehara et al [66] have found that the austenite grain size significantly varies with C content in remelted specimens, i.e.…”

“…[95][96][97] It has been demonstrated that segregated S exerts an attractive force on the electrons associated with the bonding of Fe atoms, reducing the strength of the boundaries in this way. [98] In low Mn, ultra high purity steels, heated directly to the test temperature, it was found that AIN reduced the hot ductility only indirectly by pinning the boundaries, so that S was able to segregate to them and embrittle the materialy,95 1 Thus, when the S levels were very low «0.001 wt%), the hot ductility was excellent even when high volume fractions of AIN were present, both at the austenite grain boundaries and within the matrix.…”