M. Tendo et al., Effects of nitrogen, niobium and molybdenum on strengthening of austeniticstainless steel produced by thermo-mechanical control process, ISIJ INT, 41(3), 2001, pp. 262-267
Thermo-mechanical control process (TMCP) applied to high nitrogen austeniti
c stainless steels could produce high-strength thick plates with a 0.2 % pr
oof stress of higher than 600 MPa. The effects of nitrogen, niobium and mol
ybdenum on the strengthening have been examined by hot compression tests ar
ound 1 223 K. The hardness of the compressed specimens linearly increased w
ith increasing the nitrogen content, and the increment in hardness was larg
er than that of the specimens in a recrystallized state. This could be expl
ained in terms of enhanced work-hardening by nitrogen addition during hot c
ompression. in fact, the flow stress linearly increased with increasing the
nitrogen content. The planar dislocation structure observed in the specime
ns with high nitrogen contents also gave evidence that nitrogen affected th
e work-hardening behavior. Although it was not clear that nitrogen affected
dislocation glide or dynamic recovery, it could be predicted that nitrogen
addition was effective in increasing the dislocation density. Since niobiu
m (similar to0.1 mass%) had a marked effect on retarding the static recryst
allization, probably owing to the fine precipitates of NbN, niobium additio
n is an effective way to prevent softening before accelerated cooling in TM
CP.