Investigation of the effect of isothermal heat treatments on mechanical properties of thermo-mechanically rolled S700MC steel grade

Abstract

The effect of isothermal heat treatments (1 hour at 200, 400, 600 and 800°C) on mechanical properties of thermo-mechanically rolled S700MC steel has been investigated by extensive mechanical characterizations. Treatments at 600°C increase yield and tensile strength and decrease impact energy. Below 600°C the steel retains its bainitic structure. Precipitation kinetics simulations indicate that this secondary hardening effect arises from the nucleation of fine (Nb,Ti)C particles, indicating that the bainitic structure is unstable above 600°C due to its high supersaturation with respect to C, Nb and Ti. These results can help to optimize the operating practices for post-weld heat treatments.

Effect of Austenitization Temperature on Hot Ductility of C-Mn-Al HSLA Steel

“…Controlling factors for this embrittlement are grain boundary sliding and the localization of strain to the proeutectoid ferrite film along the austenite grain boundary, which is produced by the γ→α transformation. Although much research has been done, the embrittlement mechanism has not been understood completely yet [ 4 , 5 , 6 , 7 ]. Based on the results of previous research [ 34 ] where the γ→α phase transformation temperatures Ar 3 -Ar 1 (894–688 °C) were determined by Thermo-Calc software for C-Mn-Al HSLA steel, it can be believed that the above-mentioned mechanism was the cause of embrittlement in zone 3 (austenitization of 1250 °C/30 s) and zone 4 (austenitization of 1350 °C/30 s).…”

“…In relation to the improvement of surface quality of continuously cast steels, it is important to study the hot ductility behavior of steels, considering their solidifying thermal history together with the crack formation during casting. Increasing the casting speed and strain rate during straightening can be one of the useful methods to decrease crack formation shortly after the casting zone [ 1 , 2 , 3 , 4 , 5 , 6 ].…”

“…Loss of ductility in the intermediate temperature zone generally decreases with decreased cooling rate, decreased holding temperature, and increased holding time. Strain rate does not appear to have much influence on the ductility [ 5 , 6 , 7 , 12 ].…”

“…Dropping the C or Mn to low levels can promote ferrite formation, leading to very thin troughs, which make it considerably easier to avoid the problem of transverse cracking [ 19 ]. Due to the relatively low temperatures involved, the third low-ductility zone can be seen to be a factor only in the formation of surface and subsurface cracks [ 4 , 5 , 6 ].…”

The Influence of Annealing Temperature on the Magnetic Properties of Cryo-Rolled Non-Oriented Electrical Steel

“…In contrast, Jong-Tae et al [21] found that Goss texture and γ-fiber components are weakened during grain growth. Based on previous studies, few researches had reported the microstructure and texture of thin-gauge non-oriented silicon steel during recrystallization annealing [22][23][24][25][26]. A more indepth analysis of the influence of recrystallization annealing temperatures on microstructure, texture, and magnetic properties is subsequently required.…”