Metadynamic Recrystallization in the Isothermal Double Compression of CP800 Steel

Area of Science:

• Materials Science
• Metallurgical Engineering
• Process Engineering

Background:

• The global push for decarbonization fuels interest in compact steel production (CSP) for automotive steel sheets.
• Understanding hot deformation and metadynamic softening is key to CSP feasibility for CP800 steel.

Purpose of the Study:

• Investigate metadynamic softening behavior of CP800 steel for CSP applications.
• Analyze the influence of deformation conditions and initial austenite grain size on metadynamic recrystallization (MDRX).
• Develop and validate a kinetic equation for MDRX in CP800 steel.

Main Methods:

• Isothermal double compression tests at 1173, 1273, 1373 K, strain rates of 0.1, 1, 5.0 s⁻¹, and interpass times of 1, 10, 20 s.
• Analysis of flow stress-strain curves to assess softening behavior.
• Evaluation of initial austenite grain sizes (42 μm and 92 μm) effects on MDRX.

Main Results:

• Final rolling pass temperature should exceed 1173 K to avoid mixed grain structures.
• Grain refinement via MDRX in CP800 steel is independent of initial grain size.
• Final grain size is sensitive to initial grain dimensions; lower holding temperatures and shorter durations are advisable for energy-efficient CSP.

Conclusions:

• Metadynamic recrystallization plays a vital role in CP800 steel's hot deformation behavior for CSP.
• Process parameters and initial grain size significantly influence MDRX and final microstructure.
• Optimized holding conditions can enhance energy efficiency in CSP production of CP800 steel.