The effect and interactions of interstitial hydrogen and nitrogen in ferritic steels.
This thesis details work that has been carried out in three main areas, these are: The evaluation of a physical as opposed to a chemical method for measuring the quantity of ammonia formed when hydrogen is reacted with the free nitrogen in a steel sample. Unfortunately the work has shown that due to the very small quantities of ammonia produced this is not a viable technique. The findings also indicate that any method using hydrogen to extract nitrogen as ammonia will give an over estimate of the free nitrogen content. The commissioning of a Vibran Interstitial Analyser and the design and development of a mathematical model which allows the free (uncombined) nitrogen and carbon contents to be determined from the measured data. The results from this work have been used to produce a modified equation for the predicting of the Impact Transition Temperature. There is also the possibility of developing a new method for measuring hydrogen in steel. In the third section of the work experimental evidence has been produced to show that hydrogen in iron at low temperatures can show metallic behaviour. Further testing of hydrogen treated materials has shown that at temperatures in the range -56 to -20°C hydrogen reduces the work hardening coefficient of Armco iron and mild steels with both low and high free nitrogen contents.
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Sheffield Hallam University (United Kingdom).