Influence of Ti on hot ductility of C–Mn–Al steels

Hot ductility of high Al TWIP steels containing Nb and Nb-V

“…The present work where reheating is used does not give any information on this but previous work on melted samples [10] has shown for HSLA steels where prevention of inter-granular failure is critical that again the ductility of Ti containing steels improves when the cooling rate is reduced from 60 o C/min to 12 o C/min and particles coarsen.…”

“…In addition the TiN particles that form need to be sufficiently coarse (>15nm) to no longer influence the hot ductility [9]. Ideally for this to occur, the cooling rate to the straightening temperature has to be slow ≤ 25 o C/min [10,11]. Provided enough Ti is added to combine with all the N, high N levels (~0.01%N) can be readily accommodated, this becoming more essential with the increasing use of scrap in the melt and the use of the electric arc furnace for melting.…”

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

“…A considerable amount ofresearch has been conducted to improve the hot ductility of Nbcontaining steels, mostly by the addition of alloying elements such as Ti, [6,79,81,113] Ca, [143] Zr,[I13] and y [113]. Boron has been considered as another possible element likely to improve the hot ductility in the Nb-containing steel.…”

“…[112] As weil, it has been shown that the coarsening of precipitates is quite effective in improving the hot ductility ofvarious steels at high temperatures. [3,79,113] Hence, at first sight, the reason for better ductility in the B-steel, compared to the Nbsteel, can be ascribed to the Fe23(B,C)6 particles which, although at grain boundaries, are relatively coarse,[1l2) and then not as much detrimental to the hot ductility. Fe23(B,C)6 particles contain N, as shown by Kim et al [112) Thus, precipitation of Fe23(B,C)6 reduces the amounts ofboth N and C, not only at the grain boundary but also in the grain interior, available for the precipitation of fine Nb(C,N) precipitate, which is the main cause of the hot ductility loss in the Nb-containing steel.…”

“…First of ail, Ti is beneficial to the hot ductility since it scavenges nitrogen. [81] Secondly, fast cooling rates lead to the hot ductility deterioration through encouraging finer TiN, Nb(CN), and AlNprecipitates [23,79] and precipitation of low-melting liquid FeS films at grain boundaries in lieu of MnS. [163] Thirdly, the temperature oscillation in the thermal schedule is likely to deteriorate the hot ductility by enhancing NbCN precipitation and, consequently, retarding dynamic recrystallization.…”