Next Article in Journal
Excessively High Vapor Pressure of Al-based Amorphous Alloys
Next Article in Special Issue
Characterization of Precipitates in a Microalloyed Steel Using Quantitative X-ray Diffraction
Previous Article in Journal
Characterization of Deformation Behavior of Individual Grains in Polycrystalline Cu-Al-Mn Superelastic Alloy Using White X-ray Microbeam Diffraction
Open AccessArticle

The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© Steels

1
School of Mechanical, Materials & Mechatronic Engineering, University of Wollongong, Northfields Ave, Wollongong 2500, Australia
2
Manager Hot Rolled Product Development, Sales and Marketing, BlueScope Steel, Five Islands Road, Port Kembla 2505, Australia
*
Author to whom correspondence should be addressed.
Academic Editor: Isabel Gutierrez
Metals 2015, 5(4), 1857-1877; https://doi.org/10.3390/met5041857
Received: 3 September 2015 / Revised: 18 September 2015 / Accepted: 25 September 2015 / Published: 9 October 2015
(This article belongs to the Special Issue Microalloyed Steel)
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. View Full-Text
Keywords: CCT diagrams; direct strip casting; UCS; CASTRIP; Nb microalloying; hardenability; bainitic ferrite; phase nomenclature CCT diagrams; direct strip casting; UCS; CASTRIP; Nb microalloying; hardenability; bainitic ferrite; phase nomenclature
Show Figures

Figure 1

MDPI and ACS Style

Carpenter, K.R.; Killmore, C.R. The Effect of Nb on the Continuous Cooling Transformation Curves of Ultra-Thin Strip CASTRIP© Steels. Metals 2015, 5, 1857-1877.

Show more citation formats Show less citations formats

Article Access Map by Country/Region

1
Only visits after 24 November 2015 are recorded.
Back to TopTop