Characterization of the Austenite Recrystallization by Comparing Double Deformation and Stress Relaxation Tests

Abstract

A high amount of deformation below the non-recrystallization temperature (T nr ) is a common industrial practice to achieve a good combination of toughness and strength in microalloyed steels. To combine the industrially relevant optimum combination of high productivity and product quality, an accurate knowledge of T nr and the recrystallization kinetics is required. Although a lot of literature data is available on the recrystallization behaviour of microalloyed steels, correlations are often difficult to be made due to the effect of different experimental setups, types of analysis and test schedules that are used to obtain this data. Although this would significantly improve the knowledge about these steels, so far, no systematic comparison has been presented in literature to correlate the different techniques and methods. In this study, different hot rolling simulation techniques, testing schedules and types of analysis were used to determine the recrystallization kinetics of a microalloyed steel. On the one hand, good agreement was found between the results from different test equipment for the double deformations tests. On the other hand, stress relaxation tests showed accelerated kinetics and appeared to be less effective.

Crystallographic Reconstruction Study of the Effects of Finish Rolling Temperature on the Variant Selection During Bainite Transformation in C-Mn High-Strength Steels

“…Note that the latter slopes might serve as an accurate parameter for assessing the recrystallisation fraction in hot-rolled steels. This possibility must be confirmed using mechanical methods, such as double-hit and stress-relaxation tests [67].…”

Accounting for the Inhomogeneity of Deformation in Identification of Microstructure Evolution Model / Niejednorodność Odkształcenia W I Dentyfikacji Modelu Rozwoju Mikrostruktury

“…The most recent applications of this method include steel 300M [8] and steel GCr 15 [9]. Authors of the paper [10] compared stress relaxation and 2 step deformation methods and concluded that stress relaxation tests are less effective in determining the recrystallization behaviour of microalloyed steels. First of all, a very difficult and precise setup and control of the temperature and the deformation system is necessary.…”

“…Finally, the resulting recrystallization kinetics cannot be compared with results from double deformation. In [10] accelerated kinetics was found when the stress relaxation method was used. Among the several methods developed to determine the fractional softening obtained from double deformation tests, there are two which better separate the effect of recovery and are thus more suitable to describe at an elevated temperature.…”

“…Similarly, values of the average stress for curves in the first and the second deformation, require calculation of the area under the stress-strain curve in relevant intervals of strains 0 -0.4 and 0.4 -0.8. Thus, numerical integration of the stressstrain curves is needed to calculate the softening parameter from equation (10). Whatever the method of calculation of the softening parameter is used, it does not account for the inhomogeneity of deformation and for the local influence of the recovery.…”

Strain induced grain boundary migration effects on grain growth of an austenitic stainless steel during static and metadynamic recrystallization

“…Using different interpass times the softening kinetics can be evaluated. However, no indications about the recrystallized microstructure evolution can be gathered with indirect methods as DH, therefore direct observations have to be carried out [8][9][10].…”