EFFECT OF LOW PHOSPHORUS CONTENTS ON THE TOUGHNESS PROPERTIES OF CREEP-RESISTANT STEEL 30-CRMONIV-5-11

The toughness performance and the embrittlement after an exposure for over 10 000 hours at temperatures of 500 and 550-degrees-C have been investigated on forging specimens of creep-resistant steel 30 CrMoNiV 11. The steel specimens have been specially produced with low phosphorus contents, i.e. minimum 0.002%, as part of production melts. Notched-bar impact energy vs. temperature curves have been developed, and the FAT (Fracture Appearance Transition) temperature has been determined. The tests failed to reveal any significant effect of the phosphorus content on toughness performance, i.e. a change of notch impact strength or a shift of the FAT temperature could not be established. There is therefore no need of implementing additional metallurgical measures in order to achieve particularly low phosphorus contents in creep-resistant forging steel.