Assessment of the sulfide corrosion fatigue strength for a multi-pass welded A106 Gr B steel pipe below the low SSCC limit

다국어 초록 (Multilingual Abstract)

In the area of heavy construction, welding processes are vital in the production and maintenance of pipelines and power plants. Welding processes happen to produce residual stresses and change the metal structure as a result of the large nonlinear thermal loading that is created by a moving heat source. The fusion welding process generates formidable

welding residual stresses and metallurgical change, which increase the crack driving force and reduce the resistance to the brittle fracture as well as the environmental fracture. This is a serious problem with many alloys as well as the A106 Gr B steel pipe. This pipe that is used in petrochemical and heavy chemical plants either degrades due to corrosive environments, e.g., chlorides and sulfides, and/or become damaged during service due to the various corrosion

damage mechanisms. Thus, in this study, after numerically and experimentally analyzing the welding residual stress of a multi-pass welded A106 Gr B steel pipe, the sulfide stress corrosion cracking (SSCC) characteristics were assessed in a 3.5 wt.% NaCl solution that was saturated with H₂S gas at room temperature on the basis of NACE TM 0177-90. The

specimens used are of two kinds: un-notched and notched. Then, the sulfide corrosion fatigue (SCF) strength for the un-notched specimen was assessed below the low SSCC limit that was previously obtained from the SSCC tests for the notched specimen. From the results, in terms of the SSCC and SCF, all the specimens failed at the heat-affected zone, where a high welding residual stress is distributed. It was found that the low SSCC limit of un-notched specimens

(σSSCCun-notched) was 46% (230 MPa) of the ultimate tensile strength (σU=502 MPa) of a multi-pass welded A106 Gr B steel pipe, and the notched specimens (σSSCCnotched) had 40% (200 MPa) of the ultimate tensile strength. Thus, it was determined that σSSCCun-notched was 13% lower than σSSCCnotched. Further, the sulfide corrosion fatigue limit (σSCFun-notched) was 32% (160 MPa) of the ultimate tensile strength of welded specimens. This σSCF un-notched was 20% lower than σSSCCnotched.

참고문헌 (Reference)

1 D. H. Bae, 16 (16): 1054-1064, 2002

2 C. H. Kim, "Welding residual stress analysis and fatigue crack growth characteristics of multi-pass weld pipe weldment" Key Engineering Materials 1345-1360, 2000

3 "Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements" 2002

4 DongHo-Bae, "Numerical Analysis of Welding Residual Stress Using Heat Source Models for the Multi-Pass Weldment" 대한기계학회 16 (16): 3-1064, 2002

5 A. John Sedriks, "National Association of Corrosion Engineers" 1990

6 Dongho Bae, "Corrosion Fatigue Characteristics in the Weld of Multi-Pass Welded A106 Gr B Steel Pipe" 대한기계학회 18 (18): 114-121, 2004

7 G. Y. Lee, "Analysis of welding residual stress of A106 Gr B steel multi-pass welding considering the moving heat source" KSME 384-389, 2008