Accession Number:

AD0276902

Title:

METALLURGICAL ASPECTS OF FRACTURE AT HIGH STRENGTH LEVEL

Descriptive Note:

Corporate Author:

MASSACHUSETTS INST OF TECH CAMBRIDGE METALS PROCESSING LAB

Personal Author(s):

Report Date:

1962-04-01

Pagination or Media Count:

1.0

Abstract:

Study of the effect of various austenitizing treatments on plane-strain fracture toughness K sub IC of AISI 4340 continued. As reported previously, K sub IC passed through a maximum as austenitizing temperature was increased. Typical fractures are illustrated. For the particular quantity of AISI 4340 tested, austenitizing above about 2050 F did not produce further increase in K sub IC rather, fracture followed prior austenite grain boundaries, and extensive slow crack growth occurred at mean stresses as low as 50 of the net fracture stress so that the average value of K sub IC begain to decrease and the scatter in K sub IC increased greatly. Behavior associated with the higher austenitizing temperatures is related to overheating, which continues to be an ill-understood problem in many forging operations. The actural overheating temperature varies among heats of AISI 4340, generally falling between 2100 and 2300 F. Author

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE