The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© Steels
The effect of Nb on the hardenability of ultra-thin cast strip (UCS) steels produced via the unique regime of rapid solidification, large austenite grain size, and inclusion engineering of the CASTRIP© process was investigated. Continuous cooling transformation (CCT) diagrams were constructed for 0,...
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| Format: | Article |
| Language: | English |
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MDPI AG
2015-10-01
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| Series: | Metals |
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| Online Access: | http://www.mdpi.com/2075-4701/5/4/1857 |
| _version_ | 1819002423770873856 |
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| author | Kristin R. Carpenter Chris R. Killmore |
| author_facet | Kristin R. Carpenter Chris R. Killmore |
| author_sort | Kristin R. Carpenter |
| collection | DOAJ |
| description | The effect of Nb on the hardenability of ultra-thin cast strip (UCS) steels produced via the unique regime of rapid solidification, large austenite grain size, and inclusion engineering of the CASTRIP© process was investigated. Continuous cooling transformation (CCT) diagrams were constructed for 0, 0.014, 0.024, 0.04, 0.06 and 0.08 wt% Nb containing UCS steels. Phase nomenclature for the identification of lower transformation product in low carbon steels was reviewed. Even a small addition of 0.014 wt% Nb showed a potent effect on hardenability, shifting the ferrite C-curve to the right and expanding the bainitic ferrite and acicular ferrite phase fields. Higher Nb additions increased hardenability further, suppressed the formation of ferrite to even lower cooling rates, progressively lowered the transformation start and finish temperatures and promoted the transformation of bainite instead of acicular ferrite. The latter was due to Nb suppressing the formation of allotriomorphic ferrite and allowing bainite to nucleate at prior austenite grain boundaries, a lower energy site than that for the intragranular nucleation of acicular ferrite at inclusions. Strength and hardness increased with increasing Nb additions, largely due to microstructural strengthening and solid solution hardening, but not from precipitation hardening. |
| first_indexed | 2024-12-20T23:04:53Z |
| format | Article |
| id | doaj.art-c1cd323d003847aea866bbea322b2873 |
| institution | Directory Open Access Journal |
| issn | 2075-4701 |
| language | English |
| last_indexed | 2024-12-20T23:04:53Z |
| publishDate | 2015-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Metals |
| spelling | doaj.art-c1cd323d003847aea866bbea322b28732022-12-21T19:23:54ZengMDPI AGMetals2075-47012015-10-01541857187710.3390/met5041857met5041857The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© SteelsKristin R. Carpenter0Chris R. Killmore1School of Mechanical, Materials & Mechatronic Engineering, University of Wollongong, Northfields Ave, Wollongong 2500, AustraliaManager Hot Rolled Product Development, Sales and Marketing, BlueScope Steel, Five Islands Road, Port Kembla 2505, AustraliaThe effect of Nb on the hardenability of ultra-thin cast strip (UCS) steels produced via the unique regime of rapid solidification, large austenite grain size, and inclusion engineering of the CASTRIP© process was investigated. Continuous cooling transformation (CCT) diagrams were constructed for 0, 0.014, 0.024, 0.04, 0.06 and 0.08 wt% Nb containing UCS steels. Phase nomenclature for the identification of lower transformation product in low carbon steels was reviewed. Even a small addition of 0.014 wt% Nb showed a potent effect on hardenability, shifting the ferrite C-curve to the right and expanding the bainitic ferrite and acicular ferrite phase fields. Higher Nb additions increased hardenability further, suppressed the formation of ferrite to even lower cooling rates, progressively lowered the transformation start and finish temperatures and promoted the transformation of bainite instead of acicular ferrite. The latter was due to Nb suppressing the formation of allotriomorphic ferrite and allowing bainite to nucleate at prior austenite grain boundaries, a lower energy site than that for the intragranular nucleation of acicular ferrite at inclusions. Strength and hardness increased with increasing Nb additions, largely due to microstructural strengthening and solid solution hardening, but not from precipitation hardening.http://www.mdpi.com/2075-4701/5/4/1857CCT diagramsdirect strip castingUCSCASTRIPNb microalloyinghardenabilitybainitic ferritephase nomenclature |
| spellingShingle | Kristin R. Carpenter Chris R. Killmore The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© Steels Metals CCT diagrams direct strip casting UCS CASTRIP Nb microalloying hardenability bainitic ferrite phase nomenclature |
| title | The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© Steels |
| title_full | The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© Steels |
| title_fullStr | The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© Steels |
| title_full_unstemmed | The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© Steels |
| title_short | The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© Steels |
| title_sort | effect of nb on the continuous cooling transformation curves of ultra thin strip castrip c steels |
| topic | CCT diagrams direct strip casting UCS CASTRIP Nb microalloying hardenability bainitic ferrite phase nomenclature |
| url | http://www.mdpi.com/2075-4701/5/4/1857 |
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