Tecnologia em Metalurgia, Materiais e Mineração
Tecnologia em Metalurgia, Materiais e Mineração
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John Speer, Blake Whitley, Stephanie Kaster, Kip Findley, David Matlock, Emmanuel De Moor

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Niobium-microalloying technology has been increasingly applied in a wide range of steel applications over the past half-century to enhance properties; namely to increase strength, control microstructure, and enable a variety of applications. To achieve desired performance levels, thermomechanically processed microalloyed steels are widely supplied by the steel industry for high volume applications in hot-rolled plate, sheet and structural steels. However, in steel long products and forgings, the final properties are often generated by downstream users, after heat-treatment, surface hardening, forging or wire drawing. Two examples are presented highlighting advancements associated with Nb-microalloying to enhance microstructures and properties developed during thermomechanical and/or downstream processing. In the first example, a 0.02 wt. pct. Nb addition was made to a medium-carbon bar steel intended for induction-hardening applications requiring fatigue and fracture resistance in bending and torsion. The Nb addition as well as thermomechanical bar processing led to beneficial refinement of both the pre-induction and post-induction microstructures. In the second example, a 0.01 wt. pct. Nb addition to a high-carbon wire rod was found to refine the pearlite interlamellar spacing, and increase the hardness.


Niobium; Forgings; Induction; Wire rod; Microalloyed.


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12 Cryderman R, Whitley B, Speer J. Microstructural evolution in microalloyed steels with high-speed thermomechanical bar and rod rolling. In: Proceedings of 23rd IFHTSE Congress; 2016; Savannah, USA. Materials Park: ASM International; 2016. p. 181-187.

13 Cryderman RL, Speer JG. Microstructure and notched fracture resistance of 0.56% C steels simulated induction hardening. In: Proceedings of the 29th Heat Treating Society Conference; 2017; Columbus, Ohio. Materials Park: ASM International; 2017. p. 226-233.

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21 Miller SL, De Moor E, Eavenson G. Thermomechanical processing simulation of mill deformation of high carbon wire rod. In: AISTech 2014 Proceedings; 2014; Indianapolis. Warrendale: AIST; 2014. p. 2735-2742.

22 De Moor E, Miller SL. Effects of niobium additions to a vanadium microalloyed high carbon wire steel. Wire Journal International. 2014;47:69-72.

23 Miller SL, De Moor E. Vanadium and niobium microalloying to increase strength of high-carbon wire steels. In: Proceedings of the 83rd Annual Convention of the Wire Association International Interwire Trade Exposition; 2013 Apr 22-25; Atlanta, Georgia. Guilford: WAI; 2013. p. 1-13.

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