Toughness study of API 5L X80 steel for testing the impact on heat affected zone by simulated multipass

• Published in: Tecnologia em Metalurgia, Materiais e Mineracao Vol. 20110718; pp. 39 - 48
• Main Authors: Chavez, Giancarlo Franko Sanchez, Rocha, David Bellentani, Brandi, Sergio Duarte
• Format: Journal Article
• Language: English
• Published: 01.01.2011
• Subjects: API; Ferrite; High strength low alloy steels; Scanning electron microscopy; Simulation; Steels; Welded joints; Welding
• ISSN: 2176-1515

The API 5L X80 pipeline steels are high strength low alloy steels (HSLA), which have good mechanical properties and toughness. These steels are used in the manufacture of seam welded tubes for oil and gas industrial application. Its microstructure consists mainly of bainite, acicular ferrite, polygonal ferrite and MA constituent, which is formed during welding and may impair the properties of the welded joint. The aim of this study is to evaluate the effect of different thermal cycles multipass of welding on the mechanical properties of simulated joints of API 5L X80 pipeline steels regarding circumferential welded joint and seam welded joint position. Different thermal cycles were simulated in API5L X80 steel samples with different peak temperatures of 900-800 and 900-800-650 degree C. The specimens were machined with 12x12x80 mm and simulated in the Gleeble registered equipment. The Charpy V-notch impact tests were performed at 0 degree C to evaluate the effect of thermal cycling on the properties of steels. The fractured surfaces were observed by scanning electron microscope (SEM). The results showed that the amount of MA constituent in the simulated microstructures of the heat affect zone (HAZ) is higher than that found in the base metal. This value was changed when they were made simulations of multipass welding.