UNTEMPERED ULTRA HIGH STRENGTH STEELS OF HIGH FRACTURE TOUGHNESS

The objective of the present investigation was to establish, in high yield strength steels, relationships between microstructure, fracture toughness and fatigue crack growth. Extensive microstructural examination and characterization were conducted on as-quenched, and quenched and tempered AISI 4340 steel which was austenitized both at the conventional (870 C) and the high (1200 C) austenitizing temperatures. Changes in fracture toughness resulting from variations in austenitizing and tempering treatments were related to changes in the amount and distribution of retained austenite, the morphology and distribution of carbides, and the martensite substructure and morphology. Influence of microstructure on fatigue crack propagation was investigated in as-quenched, and quenched and tempered 5Mo-0.3C secondary hardening steel. Microstructures resulting from several different tempering treatments were characterized and attempts were made to relate microstructural changes to observed differences in strength, fracture toughness and fatigue crack growth behavior.

• Corporate Authors:

  University of California, Berkeley

  Inorganic Materials Research Division, Lawrence Berkeley Lab
  Berkeley, CA  United States  94720
• Authors:
  • Parker, E R
  • Zackay, V F
  • Lai, G Y
  • Horn, R M
• Publication Date: 1974-4

Media Info

• Features: References;
• Pagination: 71 p.

Subject/Index Terms

• TRT Terms: Cracking; Fatigue cracking; Fracture properties; High strength steel; Metal heating
• Uncontrolled Terms: Heat treatment
• Subject Areas: Marine Transportation; Materials;

Filing Info

• Accession Number: 00057035
• Record Type: Publication
• Source Agency: Ship Structure Committee
• Report/Paper Numbers: AMMRC CTR-74-33 Final Rpt.
• Contract Numbers: DAAG46-73-C-0120
• Files: TRIS
• Created Date: Jul 31 1974 12:00AM