Temperature dependence of fracture toughness in cleavage fracture of iron and iron alloys

✍ Scribed by H Nakamura; T Naiki; H Okabayashi; M Kuribayashi; N Morishige

• Publisher: Elsevier Science
• Year: 1975
• Tongue: English
• Weight: 497 KB
• Volume: 7
• Category: Article
• ISSN: 0013-7944
• DOI: 10.1016/0013-7944(75)90054-5

✦ Synopsis

&&a&-In order to examine the temperature dependence of fracture toughness in cleavage fracture, exploratory work was carried out. Then dfects of alloying elements and miao-structure on the low temperature fracture toughness were studied quantitatively in iron and iron alloys. The results indicate that (1) the relationship between fracture toughness Q and testing temperature T at low temperatures is G,. = G. rxp (TI T& where G. and TO are the material constants; (2) G, exbiits a stroag dependence on solute carbon and nitrogen contents but is independent of micro-structure and other ekmcnts; (9 G, values increases with increasing solute carbon and nitrogen contents; (4) To depends on the structure; (5) l/TO vakw increase with increasing nickel and manganese contents, to the contrary, decrease with increasing carbon, silicon and phosphorus contents: and (6) I/ 7'0 values increase with decreasing &I size.

INTROJHJCTION

THE DEVELOPMENT of various new high-strength steels and the broadening range of their applications has brought about increased emphasis on the study of fracture characteristics. However, it is impossible yet to avoid fracture initiation perfectly, which occur in the welded structure. A considerable reason that the welded structural failure occurs at a low stress level is brittleness caused by the weld heat.

The degree of brittleness being present in the heat-affected zone depends on the chemical composition and the micro-structure of the steel. Then, exploratory work has been carried out which examines the effects of alloying elements and micro-structure on the low temperature toughness of iron and steels special-heat-treated.

Iron alloys containing various kind of alloying elements and commercial low alloy steels were used in this investigation. The chemical compositions of these materials are shown in Table .