Post Welding Heat Treatment Simulation in Welded Stainless Steel Pipe and Comparison with Experiment

2009 ◽  
Vol 83-86 ◽  
pp. 237-243
Author(s):  
Mohammad Sedighi ◽  
B. Davoodi
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Stainless Steel ◽  
Stress Distribution ◽  
Numerical Models ◽  
Welding Process ◽  
Steel Pipe ◽  
Hole Drilling ◽  
Distribution Data ◽  
Stainless Steel Pipe

Due to the intense concentration of heat in the welding process, residual stresses are produced in the specimen. One of the most effective ways to relief welding stress is Post Welding Heat Treatment (PWHT). In this paper, finite element method is employed to model and analyze PWHT for two pass butt-welded SUS304 stainless steel pipe. In this simulation, firstly, the welding process has been modeled. Then the stress distribution of the specimen has been transferred to a second analysis for stress relaxation modeling. Norton law is used to investigate creep in stress relief process. Experimental tests are also carried out to verify the effectiveness of the proposed numerical models. The hole drilling method is used to measure the stress distribution in the specimen. The residual stress distribution data before and after PWHT are compared to investigate the effect of heat treatment on residual stress. Based on the modeling and experimental results, the tensile and compressive stresses distributions have been reduced. They are in a reasonable agreement with each other and prove the capability of the proposed modeling technique to simulate PWHT.

scholarly journals Evaluation of Residual Stress Distribution in Austenitic Stainless Steel Pipe Butt-Welded Joint

2009 ◽  
Vol 27 (2) ◽  
pp. 240s-244s ◽  
Author(s):  
Akira MAEKAWA ◽  
Michiyasu NODA ◽  
Shigeru TAKAHASHI ◽  
Toru OUMAYA ◽  
Hisashi SERIZAWA ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Stress Distribution ◽  
Welded Joint ◽  
Residual Stress Distribution ◽  
Steel Pipe ◽  
Stainless Steel Pipe

Numerical Simulation of Residual Stress in Multi-Pass Butt-Welded Stainless Steel Pipe

2009 ◽  
Author(s):  
S. Kasa ◽  
M. Mouri ◽  
M. Tsunori ◽  
D. Takakura
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Three Dimensional ◽  
Structural Response ◽  
Welding Residual Stress ◽  
Steel Pipe ◽  
Inelastic Behavior ◽  
Axisymmetric Model ◽  
Stiffness Method ◽  
Stainless Steel Pipe

It is necessary to obtain an accurate welding residual stress distribution for the evaluation of stress corrosion cracking (SCC) behavior. However, a welding residual stress simulation for pipes is often performed by a two dimensional axisymmetric model because this type of simulation requires significant time to analyze the complicated inelastic behavior. This approximation deteriorates the modeling accuracy since the welding heat input and the structural response are approximated by axisymmetric responses although they are originally three dimensional. The authors propose “a virtual additional stiffness method” in order to improve the accuracy of the axisymmetric model. With this method, the difference between the axisymmetric model and a three dimensional behavior was greatly reduced. The virtual additional stiffness method was used to reproduce three dimensional constraints that were not taken into account in the axisymmetric model. In the case of the axisymmetric model, an unrealistic large thermal expansion was observed because of simultaneous heating along a hoop direction of the whole pipe. In order to compensate this unrealistic deformation, a virtual additional stiffness was added in axial and radial directions on the axisymmetric model. This stiffness was added by using spring elements whose positions and spring constants were determined by comparing the two and three dimensional models. Results obtained by this new method in the multi-pass butt-welded stainless steel pipe were in very good agreement with measurements of the mock-up specimens.

Finite Element Analysis of Effects of Preheating and Postweld Heat Treatment on Residual Stress in Pipe Welding

2011 ◽  
Vol 314-316 ◽  
pp. 428-431 ◽  
Author(s):  
Hui Du ◽  
Dong Po Wang ◽  
Chun Xiu Liu ◽  
Hai Zhang
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Finite Element ◽  
Stress Distribution ◽  
Welding Process ◽  
Postweld Heat Treatment ◽  
Element Model ◽  
Element Analysis ◽  
Pipe Welding ◽  
Postweld Heat

To simulate preheating and postweld heat treatment of Q345 steel pipe welding, the finite element model was established. The welding process was simulated by method of the ANSYS element birth and death technique. In this paper, to obtain the distribution of the temperature field and stress field in different situations, preheating processes with two different values of temperature and postweld heat treatment process were simulated respectively. The results show that preheating can homogenize residual stress distribution of the weldment and decrease the residual stress. The heat treatment reduces the residual stress in inner and outer walls by 24% and 70% respectively and the stress distribution is more even and stress concentration is reduced.

Evaluation of Residual Stresses in Small Diameter Stainless Steel Pipe Welds by Two-Dimensional and Three-Dimensional Finite Element Analyses

2014 ◽  
Author(s):  
Francis H. Ku ◽  
Trevor G. Hicks ◽  
William R. Mabe ◽  
Jason R. Miller
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Three Dimensional ◽  
Steel Pipe ◽  
3D Analysis ◽  
Two Dimensional ◽  
Finite Element Analyses ◽  
Stainless Steel Pipe

Two-dimensional (2D) and three-dimensional (3D) weld-induced residual stress finite element analyses have been performed for 2-inch Schedule 80 Type-304 stainless steel pipe sections joined by a multi-layer segmented-bead pipe weld. The analyses investigate the similarities and differences between the two modeling approaches in terms of residual stresses and axial shrinkage induced by the pipe weld. The 2D analyses are of axisymmetric behavior and evaluate two different pipe end constraints, namely fixed-fixed and fixed-free, while the 3D analysis approximates the non-axisymmetric segmented welding expected in production, with fixed-free pipe end constraints. Based on the results presented, the following conclusions can be drawn. The welding temperature contour results between the 2D and 3D analyses are very similar. Only the 3D analysis is capable of simulating the non-axisymmetric behavior of the segmented welding technique. The 2D analyses yield similar hoop residual stresses to the 3D analysis, and closely capture the maximum and minimum ID surface hoop residual stresses from the 3D analysis. The primary difference in ID surface residual stresses between the 2D fixed-fixed and 2D fixed-free constraints cases is the higher tensile axial stresses in the pipe outside of the weld region. The 2D analyses under-predict the maximum axial residual stress compared to the 3D analysis. The 2D ID surface residual stress results tend to bound the averaged 3D results. 2D axisymmetric modeling tends to significantly under-predict weld shrinkage. Axial weld shrinkage from 3D modeling is of the same magnitude as values measured in the laboratory on a prototypic mockup.

Characterisation of the Residual Stress Field and Mechanical Properties of a Narrow-Gap Girth-Welded Stainless Steel Pipe and Subsequent Application to a Numerical Model

2011 ◽  
Author(s):  
Robert J. A. McCluskey ◽  
Andrew H. Sherry ◽  
Martin R. Goldthorpe
Keyword(s):  
Mechanical Properties ◽  
Residual Stress ◽  
Stainless Steel ◽  
Stress Field ◽  
Steel Pipe ◽  
Primary Circuit ◽  
Narrow Gap ◽  
Residual Stress Field ◽  
Butt Weld ◽  
Stainless Steel Pipe

Girth-butt welds are used to join sections of stainless steel pipe in the primary circuit of Pressurised Water Reactors. The welding process creates residual stress fields across the weldment, which can contribute to the crack driving force when a defect is present. Assessment procedures account for such defects, enabling safety justifications to be made for continued operation of nuclear power plant. Such procedures require the size and nature of the residual stress field to be determined in order to make reliable structural integrity assessments. This paper describes the investigation of the residual stress field and fracture behaviour of a recently developed narrow-gap 304-stainless steel girth-butt weld in a primary circuit pipe. Two residual stress measurement techniques, Neutron Diffraction (ND) and incremental Deep Hole Drilling (iDHD), were used to measure the original residual stress field in the pipe weld. A second pipe weld specimen was used to fabricate tensile and fracture toughness specimens from which the mechanical properties of the weld material were determined. The residual stress and mechanical test data were used to develop numerical models of the pipe weld containing a postulated circumferential defect under an applied axial load. The numerical simulation results were applied within a failure assessment diagram, comparing different interaction parameters on the prediction of component failure load.

HRSG-Pipeline Weld Residual-Stress Measurement to Assess Influence Over Creep-Analysis Results From Italian Code, American Standard

2019 ◽  
Author(s):  
Ottaviano Grisolia ◽  
Lorenzo Scano ◽  
Francesco Piccini ◽  
Antonietta Lo Conte ◽  
Massimiliano De Agostinis ◽  
...  
Keyword(s):  
Residual Stress ◽  
Stress Measurement ◽  
Numerical Models ◽  
Equivalent Stress ◽  
Welding Process ◽  
Diffraction Method ◽  
Hole Drilling ◽  
Creep Analysis ◽  
Maximum Residual Stress ◽  
American Standard

Abstract Previous study carried out residual stress characterization for the welds of the high-temperature-section (superheater / reheater) lower headers of the bottom-supported heat-recovery steam generator (HRSG). Modeling the gas-tungsten arc, manual welding process considered only weld-lay for the ASTM A 335-Grade P22 finned-tube angle joint to the cylinder. Present study aims at indirectly assessing findings of previous analysis measuring maximum residual stress on the joint’s exservice material. To achieve that a tee similar to the previous was not available: for both experimental and numerical analyses present study considers a P22 circumferential “V”-groove butt joint on HRSG pipeline section, creep-operated for the same period and temperature as the previous case. In the experimental activity X-ray diffraction method (or alternatively, hole-drilling strain gage one) applies as close as possible to the weld, being residual stress maximum at the fusion boundary. Thermal analysis for the previous case also showed it keeps nearly constant during weld cooling, relaxing most during creep: after 200,000 hours of operation, welding-process simulation predicted a maximum residual stress of 70 MPa; tee-joint creep-analysis found out a maximum equivalent stress of 91 MPa. As for the sample withdrawal, dimensions should be sufficient to avoid any interference with measurement area. The experimental procedures should comply with the European standard EN 15305 on the matter (the American standard ASTM E 837 for the alternate method). Comparison of analysis results for the two cases, confirms tendencies previously found out in creep-behavior, though different equivalent stress contributions. Comparison of predicted and observed residual stress values should allow for validation of numerical models used in both welding process and stress analysis.

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