| About this Abstract |
| Meeting |
Materials Science & Technology 2020
|
| Symposium
|
Advanced Steel Metallurgy
|
| Presentation Title |
Double-Twist Torsion Testing to Assess Partial Recrystallization in Microalloyed Steels |
| Author(s) |
Trevor J. Ballard, John Speer, Kip Findley, Emmanuel De Moor |
| On-Site Speaker (Planned) |
Trevor J. Ballard |
| Abstract Scope |
The non-recrystallization temperature (Tnr) represents an important parameter in the development of controlled rolling schedules for processing microalloyed steels. Tnr has been used to define the transition from complete to incomplete austenite recrystallization, although multiple and slightly varying definitions exist. Controlled rolling usually involves deformation at higher temperature to refine the austenite via recrystallization above Tnr, with finishing at a lower temperature where recrystallization is fully suppressed to enable austenite “pancaking.” Thus, Tnr is important since knowledge of the temperatures where transitions in austenite recrystallization behavior occur is required for effective microstructural control in the final product A double-twist torsion test has been applied here to a Fe 0.065C 0.060Nb 0.021V (wt pct) microalloyed steel for experimental determination of the temperature region where partial recrystallization occurs. The double-twist torsion test allows the effect of multiple deformation and recrystallization cycles on Tnr to be assessed while maintaining a link to the austenite microstructure via measurements of fractional softening. Pairs of isothermal torsional deformation steps with a true strain of 0.2 per pass and a shear strain rate of 5 s-1 separated by an interpass time of 5 s were applied to a single specimen in the range of 1200 to 800 ˚C in 50 ˚C decrements. The extent of recrystallization in the austenite was estimated from the extent of softening that occurred during the interpass time. Three methods used to determine fractional softening were applied to the experimental data and compared. The temperature region of partial recrystallization was estimated from the fractional softening measurements and compared to Tnr determined using traditional methods of double-hit compression and multi-step hot torsion testing. |