Improvements in strength and toughness of experimental Fe--Cr--C steels

Conference · Thu Apr 01 04:00:00 EST 1976

OSTI ID:7273938

Carlson, M F; Rao, B V.N.; Ritchie, R O; Thomas, G

Efforts to improve Fe-Cr-C steel by modification of heat treatment and alloying additions are described. An important result of this work is in the evaluation of toughness with austenitizing temperature. The resistance to fracture of the conventionally (870/sup 0/C) austenitized structure is greatest ahead of a rounded notch (i.e., in Charpy and K/sub A/ tests), whereas it is least ahead of a sharp crack (i.e., in K/sub Ic/ test). Therefore, the advantages of increased fracture touchness, K/sub Ic/, with increased austenitizing temperature, must be weighed against the deterioration of ductility and Charpy impact energy. However, an optimum austenitizing temperature can be chosen (in the range 1000 to 1100/sup 0/C), where a 30 to 50 percent increase occurs in fracture toughness, K/sub Ic/, with no loss of strength and little reduction in impact energy and ductility. Moreover, low alloy additions of Mn and Ni can further increase the toughness of the alloy without reduction in strength. This was possible because the strengthening in these quaternary alloys was achieved primarily through solid solution hardening and not from substructural twinning in martensite. The toughness properties obtained for Fe-4Cr-2Mn-0.26C steel are superior to conventional 4340 and 300-M steels at the 200 ksi yield strength level, and yet would be cheaper to produce in large quantities.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7273938
• Report Number(s): LBL-5111; CONF-760804-1
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103* -- Metals & Alloys-- Mechanical Properties
ALLOYS
AUSTENITE
BENDING
CARBON ADDITIONS
CHARPY TEST
CHEMICAL COMPOSITION
CHROMIUM ALLOYS
CHROMIUM STEELS
ELECTRON MICROSCOPY
FRACTURE PROPERTIES
HEAT TREATMENTS
IRON ALLOYS
IRON BASE ALLOYS
MANGANESE ADDITIONS
MANGANESE ALLOYS
MECHANICAL PROPERTIES
MICROSCOPY
NICKEL ADDITIONS
NICKEL ALLOYS
STEELS
TENSILE PROPERTIES
VERY HIGH TEMPERATURE