METALLURGICAL ASPECTS OF FRACTURE AT HIGH STRENGTH LEVEL
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1962
- Accession Number
- AD0276902
Entities
People
- M.l. Ebner
- W.a. Backofen
Organizations
- Massachusetts Institute of Technology