Tempering of steel is carried out to relieve internal stresses in steel and also to bring toughness within a material. Since the process is a sub-critical heating process, so cooling in any manner will not bring any change. Certain compositions of steel if tempered at a temperature of 400oC – 600oC lose a considerable amount of hardness. This loss in hardness during tempering is termed as Tempe embrittlement. The main culprit of temper embrittlement in steel is Arsenic, Phosphorus and Antimony.