Seminar Nasional Tahunan Teknik Mesin (SNTTM) VIII Universitas Diponegoro, Semarang 11-12 Agustus 2009 588 M3-013 Mechanical Properties and Corrosion Behaviour of Spiral Welded API 5L X-52 Steel Line Pipe Mochammad Noer Ilman a , Nur Subeki b and Jarot Wijayanto c a Department of Mechanical and Industrial Engineering, Gadjah Mada University, Yogyakarta b Department of Mechanical Engineering, Muhammadiyah University of Malang, Malang c Department of Mechanical Engineering, IST Akrprind, Yogyakarta Phone/Fax : (0274)521673, E-mail : ilman_noer@ugm.ac.id ABSTRACT Spiral welded API 5L X-52 steel line pipes have been in service for many years as oil and gas transmission pipes. Such pipes are usually produced by forming hot-rolled coil (HRC) steels into tubular products and welding is performed along spirally joining lines using submerged arc welding (SAW) process. The weld metal used for oil and gas line pipes must fulfil the more stringent requirements such as high strength, good impact toughness and high corrosion resistance. The present investigation aims to study mechanical properties and corrosion behaviour of submerged arc spiral welded API 5L X-52 steel line pipe. The spiral welded steel API X-52 line pipes were produced using submerged arc welding with the filler of EM12K and flux of OK10,71. Welding parameters, i.e., current, voltage and heat input were 825 A, 35 volt and 2.1 kJ/mm respectively. Subsequently, a sequence of experiments were carried out including microstructural examination, hardness and tensile tests, V-Charpy notch impact test and corrosion test. The corrosion rate was measured using three electrode potential method with saturated calomel (Hg 2 Cl 2 ) electrode (SCE) as the standard electrode whereas the auxiliary electrode was platinum. Results show that microstructure of submerged arc weld metal for spiral welded steel API X-52 line pipes is composed of acicular ferrite as the dominant phase when filler, flux and welding parameters are properly selected and this type of microstructure seems to give high strength (ultimate strength of 563 MPa and yield stress of 488) and good impact toughness with the ductile- brittle transition temperature of 0 o C. Keywords: spiral welded pipe, acicular ferrite and mechanical properties 1. Introduction The oil and gas related industries employ pipelines as the primary mode for transporting gas, crude oil and various petroleum products. For economic reasons, oil or gas pipelines are made of carbon- manganese steels or high strength low alloy (HSLA) steels [1]. In recent years, spiral welded pipes have