Hot Ductility and Compression Deformation Behavior of TRIP980 at Elevated Temperatures

Abstract

The hot ductility tests of a kind of 980 MPa class Fe-0.31C (wt pct) TRIP steel (TRIP980) with the addition of Ti/V/Nb were conducted on a Gleeble-3500 thermomechanical simulator in the temperatures ranging from 873 K to 1573 K (600°C to 1300°C) at a constant strain rate of 0.001 s À1 . It is found that the hot ductility trough ranges from 873 K to 1123 K (600°C to 850°C). The recommended straightening temperatures are from 1173 K to 1523 K (900°C to 1250°C). The isothermal hot compression deformation behavior was also studied by means of Gleeble-3500 in the temperatures ranging from 1173 K to 1373 K (900°C to 1100°C) at strain rates ranging from 0.01 s À1 to 10 s À1 . The results show that the peak stress decreases with the increasing temperature and the decreasing strain rate. The deformation activation energy of the test steel is 436.7 kJ/mol. The hot deformation equation of the steel has been established, and the processing maps have been developed on the basis of experimental data and the principle of dynamic materials model (DMM). By analyzing the processing maps of strains of 0.5, 0.7, and 0.9, it is found that dynamic recrystallization occurs in the peak power dissipation efficiency domain, which is the optimal area of hot working. Finally, the factors influencing hot ductility and thermal activation energy of the test steel were investigated by means of microscopic analysis. It indicates that the additional microalloying elements play important roles both in the loss of hot ductility and in the enormous increase of deformation activation energy for the TRIP980 steel.

Characterization of Oxidation Behavior of Mn Fumes Generated in the Vacuum Treatment of Melting Mn Steels

“…[1][2][3][4] In particular, as fully austenitic high-Mn steels with 12-30 wt% Mn, transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) steels have attracted intense attention due to their remarkable mechanical properties, including high strength, excellent ductility, and high energy absorption capacity, and are promising candidate for the fourth-generation automotive steels. [5][6][7] Therefore, most studies of high-Mn steels have focused on their mechanical properties such as solidification structures, [8,9] nonmetallic inclusions, [10][11][12] tensile ductility [13,14] and deformation behavior, [15,16] etc., whereas studies of the smelting process have been rarely reported.…”

Transformation of Inclusions in Solid GCr15 Bearing Steels During Heat Treatment

“…Extensive research on the formation, removal, and modification of non-metallic inclusions in the molten steel at steelmaking temperatures have been conducted, such as the calcium treatment [7][8][9][10][11][12][13][14][15], the rare earth element treatment [16,17], slag refining [18][19][20][21][22], and reoxidation [23,24]. However, less attention has been paid to the variation of oxide inclusions in the solid steel during heat treatment.…”