Influence of Niobium and Molybdenum on Mechanical; Strength and Wear Resistance of Microalloyed Steels

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Abstract

The HSLA (High-Strength Low Alloy) steels are used in the production of pipes, flanges and connectors to build ducts for ore, oil and gas transport. The conventional processes are the rolling or forging. In the transport of ore and heavy oil, the abrasive particles impair the surfaces and reduce the pipelines lifetime. Therefore, besides the mechanical properties as API 5L, it is important to verify the wear resistance of these steels. In this context, two microalloyed steels were forged in the form of square bars. Thereafter, specimens of these bars were annealed at 930 ºC, quenched at 900 ºC and tempered at 600 ºC. Tensile and wear tests were performed. The results show that molybdenum and niobium present similar effects on phase transformation of steels, promoting a desired acicular ferrite/bainite microstructure and fulfill the mechanical strength of API 5L-X70 standard. The molybdenum has dominating effect in the hardenability when in solid solution, however, after tempering, thermodynamic simulation by FactSage software indicates that niobium probably promotes secondary hardening.

Details

Original languageEnglish
Pages (from-to)1029 - 1034
JournalMaterials Research
Volume20
Issue number4
Publication statusPublished - Jun 2017

Keywords

  • Wear tests of microalloyed steels, FactSage software, Steels containing niobium and molybdenum, Heat treatments, Mechanical strength of microalloyed steels