An Approach to Micro Segregation Level in Medium Carbon Low Alloy Steels and Presence of Quench Cracks

Forged and heat treated product samples  with different quench crack histories have been stored over years, waiting to be examined.  

The main investigation is SEM EDS/WDS on micro segregations to see if trends follow the expectations based on experiences from production.  Segregation level was then used as selection criteria for sampling material from present running production quench crack cases. As quenched tensile properties were used as an effect indicator on variations.

Parameters related to results from the investigations are intended to be transformed to be used in steel purchase specifications. Examples that show the relevance of requirements, are product fields like subsea and aerospace. Among the requirements are micro hardness on segregations for a given heat treatment condition, colour contrasts by etching and ESR/VAR production routes.  These requirements have, from different points of view, advantages and disadvantages.