Increasing the yield strength of Niobium micro-alloyed reinforcing bar
Date
2009-01-27T07:57:15Z
Authors
Rajkumar, Charishma
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Abstract
Reinforcing bar, which it is commonly abbreviated as rebar, is used in the
construction industry to impart tensile strength to concrete structures, which
by nature is very brittle. At ArcelorMittal South Africa Newcastle Works, 460
MPa (minimum yield strength) rebar is traditionally produced by using
Vanadium as a micro-alloying addition in order for the mild steel to attain the
required strength as specified. However, the fluctuating price of Vanadium
over the past years necessitated the use of alternative micro-alloying
elements. Niobium is currently used successfully instead of Vanadium on the
Rod mill, but not on the Bar mill, due to the difference in cooling facilities
between these rolling mills.
Alternative manufacturing routes and strengthening mechanisms for the cost
effective production of rebar containing Niobium on the Bar mill was
investigated. It was decided to produce a trial cast containing Niobium as a
micro-alloying element with a Chromium addition and subsequently roll it into
10 mm and 12 mm rebar at the Bar mill. The minimum yield strength of 460
MPa was not achieved. The average yield strength was approximately 430
MPa on both these sizes.