The effect of titanium addition on the SAW weld metal microstructure of API 5L-X70 pipeline steel was investigated. The relationship between microstructure and toughness of the weld deposit was studied by means of full metallographic, longitudinal tensile, Charpy-V notch and HIC tests on the specimens cut transversely to the weld beads. The best combination of microstructure and impact properties was obtained in the range of 0.02-0.05% titanium. By further increasing of titanium content, the microstructure was changed from a mixture of acicular ferrite, grain-boundary ferrite and Widmanstätten ferrite to a mixture of acicular ferrite, grain-boundary ferrite, bainite and ferrite with M/A microconstituent. Therefore, the mode of fracture also changed from dimpled ductile to quasi-cleavage. The results showed an increase in the titanium content of inclusions with increased titanium levels of weld metal. Titanium-base inclusions improve impact toughness by increasing the formation of acicular ferrite in the microstructure. No HIC susceptibility was found in the weld metals with titanium contents less than 0.09%.


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    Title :

    Effect of titanium addition on the microstructure and inclusion formation in submerged arc welded HSLA pipeline steel


    Contributors:
    Beidokhti, B. (author) / Koukabi, A.H. (author) / Dolati, A. (author)

    Published in:

    Publication date :

    2009


    Size :

    9 Seiten, 8 Bilder, 7 Tabellen, 33 Quellen




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English