Author : European Communities
Release : 2004
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Improvement of Weld Properties of High Nitrogen Alloyed Stainless Steels (N Weld) - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Improvement of Weld Properties of High Nitrogen Alloyed Stainless Steels (N Weld) write by European Communities. This book was released on 2004. Improvement of Weld Properties of High Nitrogen Alloyed Stainless Steels (N Weld) available in PDF, EPUB and Kindle. The objective of the research, through both an experimental and a modelling approach, was to determine the parameters controlling the nitrogen level in a weld. A second objective was to study the relationship between the weld microstructure and the corrosion properties. More particularly, the potential interest of microelectrode techniques has been investigated. TIG welding has been investigated through both an experimental and a modelling approach. TIG and A TIG tests have confirmed tnat it is necessary to add nitrogen in the shielding gas in order to prevent nitrogen loss during welding. For duplex stainless steel, 2.5 % nitrogen in the shielding gas is sufficient, whereas for high nitrogen content austenitic stainless steels higher levels are necessary. It has also been shown that, for a given grade, the nitrogen content increases when the penetration increases. Penetration depends on the material composition, with a beneficial effect of surface active elements (0, S, etc.). The model developed was based on the nitrogen exchange between the plasma, the weld pool and the shielding gas. It was first developed to describe nitrogen evolution during a stationary arc situation. The results were in good agreement with experiments. The model was then adapted to the case of welding with an active flux. An attempt was made to describe the traveling arc situation. However, some improvements are still necessary. Pitting corrosion tests have confirmed the influence of nitrogen content on the corrosion sensitivity of TIG welds. Microelectrode techniques have been used to characterise the local corrosion behaviour of welds. It has been shown that the scanning vibrating electrode technique was of limited utility to study corrosion resistance of highly alloyed stainless steels. More promising results have been obtained with microcapillary technique which make local electrochemical measurements possible. Finally, MIG tests have been performed in order to study the influence of the shielding gas composition on nitrogen content in the weld and also on the formation of porosities. For superduplex stainless steel, it has been demonstrated that nitrogen must be added in the gas to prevent nitrogen loss. It has also been shown that the number of porosities in the weld depends on the C02 content in the gas and not on the nitrogen content.