Steel plates processed according to a conventional and controlled (low finishing temperature) rolling practice were studied to establish reasons for a superior notch toughness in the controlled-rolled product. The lower transition temperature (Charpy V-notch 15 ft-lb) in plates investigated is derived largely from a smaller ferrite grain size. Experimental evidence was also obtained to indicate that a part of the improvement results from a microfissuring in the plane of the plate at the notch root, with the effect that stress triaxiality is relieved and transition temperature depressed. The origin of the flaws responsible for the fissures was not determined with certainty, but there was good indication that they were simply inclusions in a fiber structure too fine in scale for observation with normal metallographic techniques. The criteria presented for microfissuring were: (1) a flaw structure dispersed on a scale no greater than the size of the plastic volume from which the brittle crack originated; (2) a ratio of the critical fracture stress in thickness (Z) to rolling (R) direction no greater than about 1/2. The necessary fracturing anisotropy was favored by more intense fibering (lower sigma sub Z) and finer grain size (higher sigma sub R). The criteria were most nearly satisfied by controlled-rolled plate. Correlations between sigma sub Z and visible inclusion content showed the decrease in sigma sub Z to be paralleled by more elongated inclusions, as if visible changes are indicative of changes in the fine-scale fiber structure.

  • Corporate Authors:

    Oxelosunds Jarnverksaktiebolag

    Oxelosund,   Sweden 

    Massachusetts Institute of Technology

    Department of Civil Engineering, 77 Massachusetts Avenue
    Cambridge, MA  United States  02139

    Ship Structure Committee

    National Academy of Science, 2101 Constitution Avenue, NW
    Washington, DC  United States  20418
  • Authors:
    • Kazinczy, F de
    • Backofen, W A
  • Publication Date: 1960-11-10

Media Info

  • Features: References;
  • Pagination: 26 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00331914
  • Record Type: Publication
  • Source Agency: Ship Structure Committee
  • Report/Paper Numbers: SSC-126 Prog Rpt.
  • Contract Numbers: NObs-72386, NObs-72046
  • Files: TRIS
  • Created Date: May 21 1981 12:00AM