Evaluation of toughness in AISI 4340 alloy steel austenitized at low and high temperatures
- Univ. of California, Berkeley
It has been reported for as-quenched AISI 4340 steel that high temperature austenitizing treatments at 1200/sup 0/C, instead of conventional heat-treatment at 870/sup 0/C, result in a two-fold increase in fracture toughness, K/sub Ic/, but a decrease in Charpy impact energy. This paper seeks to find an explanation for this discrepancy in Charpy and fracture toughness data in terms of the difference between K/sub Ic/ and impact tests. It is shown that the observed behavior is independent of shear lip energy and strain rate effects, but can be rationalized in terms of the differing response of the structure produced by each austenitizing treatment to the influence of notch root radius on toughness. The microstructural factors which affect this behavior are discussed. Based on these and other observations, it is considered that the use of high temperature austenitizing be questioned as a practical heat-treatment procedure for ultrahigh strength, low alloy steels. Finally, it is suggested that evaluation of material toughness should not be based solely on K/sub Ic/ or Charpy impact energy values alone; both sharp crack fracture toughness and rounded notch impact energy tests are required.
- OSTI ID:
- 6850704
- Journal Information:
- Metall. Trans., A; (United States), Vol. 7
- Country of Publication:
- United States
- Language:
- English
Similar Records
Improvements in strength and toughness of experimental Fe--Cr--C steels
Effect of austenitizing temperature upon the microstructure and mechanical properties of experimental Fe/Cr/C and Fe/Cr/C/Ti steels