Secondary ion analysis of segregation in welded steels

• The role of weld defects, such as root cracks, or cold cracking in helping to initiate fatigue failure or reducing the impact toughness of welded constructions is now fairly well established. In the case of cold cracking, it is now standard procedure to use the basic (low-hydrogen) electrodes when welding high-strength micro alloyed fine grained or quenched and tempered steels. However, it has to be acknowledged that the mechanism of cold cracking and its relation to the dispersion of inclusions or the amount of hydrogen in steels is not well understood. It has been established that cold cracking may arise in welds containing martensite due evidently to the fact that hydrogen has a lower solubility in martensite than ferrite. However, whether the expelled hydrogen then congregates at the martensite/ferrite phase boundary or elsewhere has not been clarified. It was thus the object of the present work to consider some of the metallurgical consequences of using basic or rutile electrodes when welding high-strength steels, with particular reference to the segregation of the various alloying elements around inclusions. For this purpose the relatively new technique of secondary ion analysis was employed in conjunction with light and electron microscopy. The unique feature of secondary ion analysis is that hydrogen can be detected even when present in relatively small amounts.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik -- Metallurgi och metalliska material (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering -- Metallurgy and Metallic Materials (hsv//eng)

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