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Title

NIOBIUM MICROALLOYED CA-50 REBARS – DEVELOPMENT AND INVESTIGATION

Authorship

Silva, Ana Clara Fonseca da; Bittencourt, Tiago Seixas; Pereda, Beatriz; Lopez, Beatriz; Rebellato, Marcelo Arantes; Silva, Andre Luiz Vasconcellos da Costa e

Silva, Ana Clara Fonseca da

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Bittencourt, Tiago Seixas

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Pereda, Beatriz

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Lopez, Beatriz

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Rebellato, Marcelo Arantes

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Silva, Andre Luiz Vasconcellos da Costa e

27 Articles, Downloaded 17260 Times

DOI

10.5151/9785-9785-32319

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Abstract

Reinforcing steel bars are usually specified based on mechanical properties with flexibility in chemical composition and processing. Most developments, in these steels, are usually focused on alloy and process design to reach minimum cost and conformity to specification. Processing routes using quenching and self-tempering (QST) and accelerated cooling are the most common. Microalloying with V and Nb have been used in rebar. When acicular constituents must be avoided, a combination of Nb microalloying with judicious control of cooling is one of the preferred options. Niobium can contribute to improvement in tensile properties through austenitic grain size control during hot working, precipitation hardening due to carbonitrides or clusters, and hardenability increase. In the present work the alloy design and development processes of a Nb microalloyed steel for rebars are presented. The designed steel has fulfilled the required specification and is under regular production. Austenitic grain size refining – when comparing with the “basic composition” normally used was observed, even without any change in the thermomechanical processing cycle. There are indications that precipitation hardening may also occur. Results indicate that Nb is a good alternative as a microalloying element in rebars.

Keywords

microalloying, Niobium, Reinforcing bar, Phase transformation, Computational thermodynamics