Variation in Mechanical Properties and Heterogeneity in Microstructure of High-Strength Ferritic Steel During Mill Trial
IR@NML: CSIR-National Metallurgical Laboratory, Jamshedpur
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Title |
Variation in Mechanical Properties and Heterogeneity in
Microstructure of High-Strength Ferritic Steel During Mill Trial
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Creator |
Ghosh, M
Barat, K Das, Swapan K Ravi Kumar, B Pramanick, A K Chakraborty, J Das , Goutam Hadas, S Bharathy, S Ray , S K |
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Subject |
Materials Charcterization
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Description |
HS600 and HS800 are two new generation, high-strength advanced ferritic steels that find
widespread application in automobiles. During commercial production of the same grades with
different thicknesses, it has been found that mechanical properties like tensile strength and
stretchability varied widely and became inconsistent. In the current endeavor, two different
thicknesses have been chosen from a mill trial sample of HS600 and HS800. An in-depth
structural characterization was carried out for all four alloys to explain the variation in their
respective mechanical and shear punch properties. The carbon content was smaller and Ti+
Mo quantity was higher in case of HS800 with respect to HS600. The microstructure of both
steels consisted of the dispersion of (Ti,Mo)C in a ferrite matrix. The grain size of HS800 was
little larger than HS600 due to an increased coiling temperature (CT) of the former in comparison
to the latter. It was found that in case of same grade of steel with a different thickness, a
variation in microstructure occurred due to change in strain, CT, and cooling rate. The strength
and stretch formability of these two alloys were predominantly governed by a microalloyed
carbide. In this respect, carbides with a size range above 5 nm were responsible for loosing
coherency with ferrite matrix. In case of HS600, both £5 and>5-nm size (Ti,Mo)C precipitates
shared a nearly equal fraction of microalloyed precipitates. However, for HS800,>5-nm size
(Ti,Mo)C carbide was substantially higher than £5-nm size alloy carbides. The ultimate tensile
strength and yield strength of HS800 was superior to that of HS600 owing to a higher quantity
of microalloyed carbide with a decreased column width and interparticle distance. A higher
degree of in-coherency of HS800 made the alloy prone to crack formation with low stretchability.
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Publisher |
Springer
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Date |
2014
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Type |
Article
PeerReviewed |
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Format |
application/pdf
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Identifier |
http://eprints.nmlindia.org/6916/1/Met_Trans_45A_2014__2724.pdf
Ghosh, M and Barat, K and Das, Swapan K and Ravi Kumar, B and Pramanick, A K and Chakraborty, J and Das , Goutam and Hadas, S and Bharathy, S and Ray , S K (2014) Variation in Mechanical Properties and Heterogeneity in Microstructure of High-Strength Ferritic Steel During Mill Trial. Metallurgical Transaction A, 45A (IF-1.730). pp. 2719-2731. |
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Relation |
DOI: 10.1007/s11661-014-2226-0
http://eprints.nmlindia.org/6916/ |
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