This thread is for a discussion on the causes and effects of temper embrittlement.  The topic comes up every now and then, and really deserves a thread to be able to point people to when needed.  I will do my best to keep things as simple as possible, while at the same time covering the important parts.  Besides a number of years as a practicing metallurgist in steel foundries I am also using my 3 most common reference books for this type of topic that I keep within reach on my desk:  The ASM He