- freely available
Metals 2019, 9(8), 814; https://doi.org/10.3390/met9080814
2. Materials and Methods
2.1. Torsion Simulations
2.2. Microstructural Analysis
3.1. Stress–Strain Curves from the Plate Rolling Simulations
3.2. Optical Microscopy Results
3.3. Calculation of the Critical Strains for the Onset of DT and DRX
4.1. Mean Flow Stresses
4.2. Volume Fraction of DT Ferrite per Pass
4.3. Production/Retention Tendencies for the Formation of DT Ferrite
4.4. Microstructure Analysis
- The number of roughing passes employed before the finishing simulations influenced the levels of flow curves during the five-pass simulated Steckel mill operation. The DT ferrite inherited from the higher number of roughing passes (higher retained strain) contributed to the increase in softening observed during the finishing passes.
- Thermomechanical schedules with a higher number of roughing passes produced higher amounts of ferrite volume fractions which sharply reduced the levels of the MFS. This is supported by images from optical microscopy. The perceptive MFS increase from the first to the second pass is attributable to strain accumulation.
- The critical strains to dynamic transformation in the finishing passes were shown to be dependent on the number of roughing passes. Higher numbers of roughing strains led to lower values of critical strain to DT in the first finishing pass of the five-pass simulations. This value decreases from pass to pass due to retained work hardening from the previous pass.
- Microstructure analysis showed that ferrite is mostly present in a polygonal form after each strain. This is a result of the displacive mechanism that occurs on the critical strain, which then coalesces diffusionaly into polygonal grains on continued straining.
Conflicts of Interest
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|C||Mn||Si||Cr||Nb||N||Orthoequilibrium Ae3||Paraequilibrium Ae3|
|0.047||1.56||0.25||0.21||0.092||0.008||846.1 °C||811.2 °C|
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