Characterization Microstructural and Mechanical of X-60 Steel Heat-Treated
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Characterization Microstructural and Mechanical of X-60 Steel HeatTreated N. López Perrusquia1*, J. A. Ortega Herrera1, M.A. Doñu Ruiz1, V. J. Cortes Suarez2, L. D. Cruz Rosado3. 1
Instituto Politécnico Nacional, SEPI-ESIME, Adolfo López Mateos, Zacatenco. México.D.F. 07738. México. 2 Univerisdad Autónoma Metropolitana Unidad Azcapotzalco, Av. San Pablo 180 Azcapotzalco 02200, México .D.F. Área de Ciencia de los materiales. 3 Universidad Politécnica del Valle de México, Grupo Ciencia e Ingeniería de Materiales. Av. Mexiquense, Tultitlán. Edo. México. México. * E-mail: [email protected] ABSTRACT In this paper was study the effect of heat treatment on mechanical properties of an API X-60 steel used for storage and transportation of hydrocarbons. In the first stage evaluation are mechanical properties of steel heat treated by the technique of the three-point test according to ASTM 399-90 was carried out. In the second stage, characterization of the type of failure and microstructure through optical microscopy (OM) was determined; also heat treated samples were then mechanically tested for hardness (HRC) and nano-indentation. The presence of alloying elements by scanning electron microscopy (SEM) and the fracture surfaces generated in the steel with varying times, temperatures and cooling medium generated by different modes of solicitation (Bending), likewise with loading rates were determined. The results revealed a ductile fracture and microstructures (PF) ferrite-pearlite (DP), bainite -ferrite (BF) and martensite-retained and martensite/retained austenite (MA). Finally, this article discusses the effect of heat treatment followed by precipitation hardenable of steel API X-60 on the mechanical properties Keywords: steel, optical metallography, scanning electron microscopy (SEM), hardness, nanoindentation
INTRODUCTION Generally, heat treatment improves steels toughness and hardness, and it is absolutely necessary for the proper functioning of steels. The heat treatment usually consists of austenitizing, quenching and is followed by multiple tempering. After this procedure the steels gain properties that are suitable for industrial applications [1-2]. The steels specified API X-60 in the API standard (American Petroleum Institute), are mainly are used in the oil industry, where the principal alloying elements added to steel in widely varying amounts either singly or in complex mixtures are nickel, chromium, manganese, molybdenum, vanadium, niobium, silicon and cobalt; these alloying elements permit Precipitation hardening of steels API X-60 for hydrocarbons and storage are being proposed for such an application, yielding improved
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mechanical properties and increased life-time. Also the type of microstructure of the steel pipe is a significant feature that is required to increase its mechanical, physical and chemical properties. The test material is commercial steel API X-60, this type of steel is hot rolled, which is subsequently rapidly cooling; a structure obtained as austenite, pearlite and cementita [3-4].
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