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- Sotkovszki, P., et al.
(author)
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Secondary ion analysis of segregation in welded steels
- 1979
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In: Metal Science. - : Maney Publishing. - 0306-3453. ; 13:10, s. 597-601
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Journal article (peer-reviewed)abstract
- 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.
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- Åström, H., et al.
(author)
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Hot cracking and micro-segregation in 18-1 0 stainless steel welds
- 1976
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In: Metal Science. - : Maney Publishing. - 0306-3453. ; 10:7, s. 225-234
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Journal article (peer-reviewed)abstract
- Advanced quantitative chemical and image analysis techniques based on scanning and scanning-transmission electron miCroscopy have been used to study hot cracking and micro-segregation in an 18%Cr-10%Ni weld metal. It is found that the main cause of hot cracking is sulphur segregation. In fully austenitic welds, manganese remains in solution and when the last of the S-rich 'melt solidifies Mn is simply not available to break up the sulphide films. The present practice of substantially increasing the amount of Mn in austenitic welds, or adding cerium, would thus seem to be justified. Phosphorus also aggravates the problem of hot cracking, but fortunately it does not appear to segregate so markedly as sulphur, being much more soluble in austenite. If the weld metal is so alloyed that solidification to the two-phase austenite plus ferrite occurs, hot cracking does not occur. The two main reasons are concluded to be: (1) manganese is less soluble in ferrite than austenite and a sufficient quantity of Mn is evidently released to combine with S and form inclusions; (2) the structural refinement of two-phase structures, compared to the single-phase austenite, results in a more even distribution of Sand P throughout the weld metal, and marked segregation is thus avoided.
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