Effect of Intercritical Heat Treatment on J-R Fracture Resistance of SA508 Gr.1A Low-Alloy Steels

Se Mi Hyun, Seokmin Hong, Min Chul Kim, Jongmin Kim, Seok Su Sohn

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


Abstract: SA508 Gr.1A low-alloy steel is used for main steam line piping in nuclear power plants. The yield strength and J-R fracture resistance of the piping material must be high in order to apply the leak-before-break concept. In this study, intercritical heat treatment (IHT) was applied to two SA508 Gr.1A low-alloy steels having different chemical compositions, namely, samples C and P; the latter containing Mo and V. Their microstructures, tensile properties, impact properties, and J-R fracture resistances were evaluated, and the effects of IHT on the mechanical properties of the steels were analyzed. After IHT, fine grains formed at grain boundaries and coarse cementite decomposed, which greatly improved toughness without reducing the strength. Further, a model to predict the J-R fracture resistance (JIc) of the SA508 Gr.1A low-alloy steel was developed by considering the microstructural and mechanical factors that affect the J-R fracture resistance. According to the JIc results of 12 kinds of SA508 Gr.1A low alloy steel, subjected to different heat treatments, the JIc was linearly proportional to the number of effective grains (N) contained in the plastic zone, which showed that N is the main factor affecting JIc. Furthermore, the yield and tensile strengths were considered to compensate for the strength difference owing to the different chemical compositions. The JIc prediction model was derived considering the effective grain size, plastic zone size, and tensile properties. The predicted JIc values agreed well with the test JIc values. Graphical abstract: [Figure not available: see fulltext.].

Original languageEnglish
Pages (from-to)2907-2918
Number of pages12
JournalMetals and Materials International
Issue number12
Publication statusPublished - 2022 Dec


  • Intercritical heat treatment
  • J prediction model
  • J-R fracture resistance
  • Microstructure
  • SA508 Gr.1A low-alloy steel

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys
  • Materials Chemistry


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