Double twist torsion testing to determine the non recrystallization temperature

Abstract

A double-twist torsion testing technique has been developed using a 316 stainless steel as an exemplar material to experimentally assess recrystallization behavior and determine the non-recrystallization temperature (Tnr). This new method was compared to the traditional methods of double-hit compression and multi-step hot torsion testing. The double-twist torsion test allows Tnr to be related to the extent of austenite recrystallization through measurements of fractional softening while accommodating multiple deformation and recrystallization steps with a single specimen. The double-twist torsion test resulted in average Tnr values similar to those determined with multi-step hot torsion, and a partially recrystallized microstructure was observed in the vicinity of the calculated Tnr for all three methods. The ability of the double-twist torsion test to relate the experimental Tnr to the evolution of austenite recrystallization via fractional softening measurements while incorporating effects of multiple deformation steps offers an advantage over traditional methods for quantifying changes in austenite recrystallization during thermomechanical processing.

Effect of Nb and Mo on Austenite Microstructural Evolution During Hot Deformation in Boron High Strength Steels

“…[10,11] Torsion double twist technique shows several advantages when compared to the traditional double-hit compression tests. [12] In addition, the initial austenite grain size (D 0 ) before the double twist torsion tests was measured. To that end, the samples were quenched after reheating and applying a roughing pass at 1175 °C.…”

Physical simulation of finish rolling of microalloyed steels in isothermal conditions

“…Due to short interpass time and adiabatic heating, it can be assumed that finish rolling happens under isothermal conditions [5]. As shown in Figure 1, the roughing stage is performed above the non-recrystallization temperature, T nr , temperature above which recrystallization is still complete [8][9][10][11]. Hot rolling at a finish rolling mill, is performed between T nr and A 3 , temperature below which recrystallization is suppressed as can be seen in Figure 1 [5,[7][8][9]10,12].…”

“…As shown in Figure 1, the roughing stage is performed above the non-recrystallization temperature, T nr , temperature above which recrystallization is still complete [8][9][10][11]. Hot rolling at a finish rolling mill, is performed between T nr and A 3 , temperature below which recrystallization is suppressed as can be seen in Figure 1 [5,[7][8][9]10,12]. Suppression of the recrystallization process depends on formation of precipitates (nitrides and/or carbonitrides) based on microalloying elements [13][14][15][16][17].…”

Effect of Sample Geometry on Strain Uniformity and Double Hit Compression Tests for Softening Kinetics Determination

“…[ 5–7 ] These machines use compression and torsion samples to investigate the key fundamental metallurgical processes such as softening, which is not economically viable on full‐scale plant trials. [ 8,9 ]…”

“…[5][6][7] These machines use compression and torsion samples to investigate the key fundamental metallurgical processes such as softening, which is not economically viable on full-scale plant trials. [8,9] Static softening occurs during hot rolling of steel and several methods are used to determine the softening fraction for a given strain, deformation temperature, and interpass time (time between two deformation strains). [10][11][12] Double hit test is a widely used approach to measure softening fraction using laboratory-based thermomechanical simulators.…”