Journal of Failure Analysis and Prevention

, Volume 13, Issue 6, pp 658–665 | Cite as

Failure Analysis of Welded Radiant Tubes Made of Cast Heat-Resisting Steel

  • Ali Reihani
  • Seyyed Ali Razavi
  • Ehsan Abbasi
  • Ahmad-Reza Etemadi
Case History---Peer-Reviewed


Radiant tubes made of cast heat-resisting steels were cracked after 4 years of operation at 1020 °C temperature in hydrocarbon cracking furnace. Optical microscopy of the tubes showed that there was extensive precipitation and intermetallic compound formation especially as brittle networks with progressive reduction in toughness and resistance to thermal and mechanical stresses. SEM and EDS analysis proved both decarburization and oxidation on interior and exterior surfaces. Apart from cracking due to long-term heating, the tubes experienced high temperature creep. HAZ cracking after welding of cracked and/or creeped tubes due to formation of brittle carbide networks was overcome by localized solution heat treatment followed by fast dry air cooling. Localized dissolution of carbide networks and intermetallic compounds resulted in lower strain microstructures and enhanced resistance of parts to thermal and mechanical stresses during repair welding. It is evident that localized solution heat treating other than lowering strains can cause the precipitates to be more uniformly and finely distributed. Fast dry air cooling rate after solution heat treating and similar cooling after welding can help to control precipitation of carbides. Detailed non-destructive testing after welding along with tensile testing proved that post-weld cracking was controlled.


Embrittlement Cracks Decarburization Heat-affected zone Welding 



The authors would like to thank all staffs in the Welding/NDT section, Assessment and Integrity Division of Arya-Sasol Polymer Company, Southern Pars of Special Zone.


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Copyright information

© ASM International 2013

Authors and Affiliations

  • Ali Reihani
    • 1
  • Seyyed Ali Razavi
    • 1
  • Ehsan Abbasi
    • 1
  • Ahmad-Reza Etemadi
    • 2
  1. 1.Welding & NDT Section, Assessment, Integrity DepartmentArya-Sasol Company, Southern Pars of Special ZoneAsaluyehIran
  2. 2.Department of Materials & Metallurgical EngineeringNew Mexico TechSocorroUSA

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