Effect of Alloying Additions in the Final Microstructure of Nb-Mo Steels Processed by Thin Slab Direct Rolling Technologies P. Uranga , J. Ganzarain, D. Jorge-Badiola and J.M. Rodriguez-Ibabe [email protected]MS&T’08 Conference October 6-9, 2008, Pittsburgh, PA CEIT and TECNUN (University of Navarra) Donostia-San Sebastián Basque Country, Spain
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Effect of Alloying Additions in the Final Microstructure of Nb-Mo steels Processed by Thin Slab Direct Rolling Technologies
Presentation made at Materials Science and Technology 2008 Conference held in Pittsburgh
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Effect of Alloying Additions in the Final Microstructure of Nb-Mo Steels Processed by Thin
Slab Direct Rolling Technologies
P. Uranga, J. Ganzarain, D. Jorge-Badiola and J.M. [email protected]
MS&T’08 ConferenceOctober 6-9, 2008, Pittsburgh, PA
CEIT and TECNUN (University of Navarra)Donostia-San SebastiánBasque Country, Spain
MS&T’08 Conference, Pittsburgh, PA
Introduction
• Multiple alloying combinations for high strength properties
• Thin slab direct rolling metallurgical peculiarities– As-cast coarse grains– Alloying elements in solid solution
• Study of combined effect in softening and precipitation kinetics
• Modeling and microstructural evolution validation for schedule optimization
• Homogenous ferrite microstructures correspond to high angle GB units
Tini = 1100ºC 3N
b-M
o31
MS&T’08 Conference, Pittsburgh, PA
Microstructural Units EBSD• Prior austenite coarse grains transform to
coarse ferrite units or acicular structures: forming low angle GB areas.
Tini = 1050ºC
3Nb-
Mo3
1
MS&T’08 Conference, Pittsburgh, PA
Conclusions• Mo addition to Nb microalloyed steels: important
increase in the delay of static rex kinetics → The refinement of the initial as-cast structure is retarded.
• For homogeneous microstructures: EBSD show that ferrite grains are diversely oriented with high-angle grain boundaries.
• Structures transformed from non-refined as-cast grains form coarse microstructural units, bigger than those observed with the optical microscope. Toughness will be impaired.
• For optimized thermomechanical schedules, Mo affects hardenability. This factor can be useful for the formation of complex microstructures with high strength and toughness levels.
Effect of Alloying Additions in the Final Microstructure of Nb-Mo Steels Processed by Thin
Slab Direct Rolling Technologies
P. Uranga, J. Ganzarain, D. Jorge-Badiola and J.M. [email protected]
MS&T’08 ConferenceOctober 6-9, 2008, Pittsburgh, PA
CEIT and TECNUN (University of Navarra)Donostia-San SebastiánBasque Country, Spain