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Authors:
Alec Williamson - alecwilliamson@mines.edu
Sam Findley, David Ulrich, Dominic Piccone, Sam Nikolai, Colton Brown, Emmanuel De Moor, Lawrence Cho
Advanced Steel Processing and Products Research Center (ASPPRC)
Colorado School of Mines
Matthew Merwin, Matthew McCosby, U. S. Steel
Malavikha Rajivmoorthy, Eliseo Hernandez, Cleveland-Cliffs
Robert Goldstein, Fluxtrol
Laurent Lesne, David Barbier, Fives Group
Project Objectives
- To advance electrified induction heating technology for sustainable (energy-efficient and clean) steel processing
- To explore the feasibility of induction heating to (entirely) replace conventional gas-fired furnaces in continuous annealing line while enhancing steel performance, with a focus on the rapid induction heating applications to AHSS.
- Computational and laboratory induction annealing simulations
- Student engagement with the steel industry
Background: Industrial Electrification
Continuous Annealing Line and Combustion Heat
Key Challenges and Opportunities
- Metallurgical Aspects and Opportunities
- Processing-Microstructure-Property relationship optimization needed across various steel grades
- Emphasis on initial microstructure, e.g. cold-rolled reduction
- Processing, Operation, and Maintenance
- Different processing windows/routes
- Magnetic permeability versus energy input
- Temperature uniformity (e.g. edge of sheet)
- Temperature measurement and control
- Steel strip feeding rate compatible with desired heating rate
- Cost of electricity
- Surface quality control
- Scale reduction and selective oxidation on uncoated and coated products
- Re-optimize gas atmosphere conditions (e.g. dew point)
CSMMAC Meeting (April 17, 2024)
Discussion between ASPPRC and industrial mentors (U.S. Steel, Cleveland-Cliffs, and Fluxtrol)
Compare Conventional Q&P vs Q&P Involving Induction Heating
- Medium Mn (3-5%) steels, provided by POSCO
- Designed industrially relevant conventional and induction Q&P cycles
- For the Fe-0.3C-5Mn-1.6Si-1.0Cr alloy, soaking temperatures used were 830°C for conventional and 850°C for rapid.
As-Received Microstructures
- Cold-rolled condition.
- Microstructure likely consisting of bainite, retained austenite, and fine cementite.
- Vickers hardness: 370 ± 4.5 HV (3Mn)
Dilatometry and M' s Temperature (3Mn)
Retained Austenite Stability
Quenched and Partitioned Microstructure
Quenched and Partitioned Microstructure 3Mn
Quenched and Partitioned Microstructure (5Mn)
Quenched and Partitioned Microstructure
Conf. Index Mapping Showing Retained Austenite Morphology (5Mn)
Electrifying Current Lines
- Computational ELTA simulation for multi-stage strip heating to determine the optimal induction processes.
- Thermal and electric efficiency during stage heating investigated for longitudinal and transverse flux.
- Significant efficiency benefit to heating with transverse flux at and above Curie temperature.
Ultra-Rapid Q&P Opportunities
- Equivalent diffusion calculations were used to determine an equivalent rapid partitioning step.
- Sensitivity between 1-5s will be investigated.
- An equivalent ret. austenite fraction can be stabilized.
Conclusions
- This project explores the feasibility of induction heating to (entirely) replace conventional gas-fired furnaces in continuous annealing lines, with a focus on the rapid induction heating applications to AHSS.
- Q&P involving rapid induction heating stabilizes higher fractions of retained austenite compared to conventionally continuous-annealed microstructures
- Rapid heating could result in finer distributions of retained austenite due to inhomogeneous microstructures.
- Rapid partitioning can effectively stabilize equivalent fractions of retained austenite.
Alec Williamson
alecwilliamson@mines.edu
Acknowledgements
- We gratefully acknowledge the support provided by the AIST Foundation, Fluxtrol, and the sponsors of the ASPPRC, including U.S. Steel, Cleveland-Cliffs, and POSCO
- Contributions by Sam Findley, David Ulrich, and the Senior Design team (Dominic Piccone, Sam Nikolai, Colton Brown, Marty Martin) are also acknowledged
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