Investigation of key-hole weldability of line pipe steel grade X70M in terms of fracture toughness

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Metalurji ve Malzeme Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2017

Öğrenci: MEHMET ÇAĞIRICI

Eş Danışman: CEMİL HAKAN GÜR, KORAY YURTIŞIK

Özet:

Micro-alloyed and thermomechanically rolled HSLA line pipe steels promise optimum strength and toughness. Their microstructure contains generally globular and acicular ferrite. However, the heat induced by welding during line pipe fabrication alters the microstructure at the proximity of the fusion zone which affects indirectly microstructure of the heat affected zone, consequently the fracture toughness, is governed by the chemistry of the material and the thermal cycles during the welding process. In fabrication generally submerged arc welding (SAW) is applied. The hybrid plasma arc welding (HPAW) might save filler consumption and reduce the heat input of the process. The purpose of this work is to investigate weldability of X70M by using the key-hole based hybrid welding process by focusing on fracture toughness.