Modelling of Flow Stress and Prediction of Workability by Processing Map for Hot Compression of 43CrNi Steel

Abstract

The isothermal hot compression tests of 43CrNi steel was carried out at temperatures 800°C to 1 050°C at an interval of 50°C and at constant strain rates of 0.01, 0.1, 1.0 and 10 s − 1 for total true strain of 0.7. The values of experimental stress were corrected for adiabatic heating which was used for flow stress modeling, and further its predictability was verified with experimental results. The true stress-true strain curves exhibit peak stresses followed by softening due to occurrence of DRX. The activation energy was calculated based on sinh type equation and found to be increasing with increase in strain. The obtained stress exponent 5.4, suggests that the mechanism of hot deformation is dislocation glide controlled by dislocation climb. Strain rate sensitivity maps and processing maps were developed using dynamic materials model (DMM), modified DMM with different instability criteria. The instability parameter, κ j , is directly related to the dissipative function which is associated to microstructural changes, J, whereas the instability parameters, ξ and κ, are associated with the strain rate sensitivity parameter, m. Therefore, the instability parameter, κ j , is more mathematically precise as it eliminates m from its calculations. The microstructures of deformed specimens were studied and correlated with the domains of processing maps to validate the workability region.KEY WORDS: medium carbon low alloy steel; processing maps; hot deformation; constitutive analysis; thermo mechanical simulator.

Critical condition parameters and kinetics of dynamic recrystallization for hot deformed 1 wt%Cr-1 wt%Mo rotor steel

“…These values of material constants and activation energy are closer to the reported values of similar kind of hot deformed steels [22][23][24]. Due to the effect of alloying elements, the apparent activation energy for hot deformation (456.42 kJmol −1 ) of present steel is much larger than the self-diffusion activation energy of austenitic steel i.e 312 kJmol −1 [25,26].…”

Correlation among the Power Dissipation Efficiency, Flow Stress Course, and Activation Energy Evolution in Cr-Mo Low-Alloyed Steel

“…In order to evaluate the accuracy of the above performed MLP-approximation, the Pearson's correlation coefficient [59], R (-), and the average absolute relative error, AARE (%), have been calculated-see Equations (10) and (11) [17]. In these equations, the T i (MPa) and A i (MPa) represent the flow stress values of the target (i.e., experimental) and approximated dataset, respectively.…”

“…The calculated material constants of the above-introduced polynomials (7)-(9) are listed in Tables 3-5 together with the achieved values of the Pearson's correlation coefficient [59], R (-), Equation (10). In this equation, in association with the polynomials (7)-(9), T i (K, -, MPa −1 ) and A i (K, -, MPa −1 ) represent the target and approximated values of the studied parameters, i.e., M(ε, b3,3 0.00 × 10 0 b4,3 0.00 × 10 0 b0, 4 1.93 × 10 −10 b1,4 0.00 × 10 0 b2,4 0.00 × 10 0 b3,4 0.00 × 10 0 b4,4 0.00 × 10 0 R 0.996660…”

“…together with the achieved values of the Pearson's correlation coefficient[59], R (-), Equation(10). In this equation, in association with the polynomials (7)-(9), Ti (K, -, MPa −1 ) and Ai (K, -, MPa −1 ) represent the target and approximated values of the studied parameters, i.e., M( , ), n( , ), and α(ε,T).…”

Extension of Experimentally Assembled Processing Maps of 10CrMo9-10 Steel via a Predicted Dataset and the Influence on Overall Informative Possibilities

“…Since the end of the 20th century, processing maps, i.e., power dissipation maps superimposed by flow instability maps, have been extensively studied as a very convenient tool for the optimization of hot forming processes, such as rolling, forging, etc. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. These maps simply display the combinations of thermomechanical conditions, i.e., strain, strain rate, and deformation temperature, which are suitable for the forming processes of an examined material.…”