Papers by Keyword: Repair Weld

Abstract: In this study the repair weld simulation of an austenitic steel pipe is performed to measure the residual stresses caused by the welding. The simulation consists of three work tasks. First the girth welding of the pipe is performed on simplified geometries to decrease the calculation time. The next work task is the simulation of the machining of the repair weld excavation, performed in one simulation step. The last task is the simulation of the repair welding. Residual stress measurements are performed on weld repair to provide validation of the simulation performed on the model.

Abstract: In common with all mechanical strain relief residual stress measurement methods, extra care must be taken when making measurements on components containing highly triaxial residual stress fields which are close to yield. The introduction of a free surface, created as part of the measurement procedure, can lead to plastic redistribution of the residual stress field. Usually, this is not accounted for in the elastic inversion algorithms of the experimental procedure. This paper demon­strates the usefulness and accuracy of deep-hole drilling (DHD) method [1] in a component predicted to contain a triaxial residual stress field. Previous measurements [2] are compared with the results of a DHD simulation on a type 316H stainless steel pipe containing a repair weld offset from an original girth weld. The influence of different material models was also studied.

Abstract: Conventionally, shielded-metal arc welding (SMAW) process has been applied to join pipes of reactor coolant loop, which caused defects and lot of loss in time and cost due to excessive heat input in joining section. Recently, narrow-gap welding (NGW) process was introduced to overcome the disadvantages of SMAW. However, the application of NGW to nuclear power plant is not yet commonly used, because safety of NGW process is not fully proven. In the present paper, welded coupons are made of stainless steel. They are manufactured under different processes; general welding (GW), and repair welding after GW. Performed are various mechanical tests to investigate microstructure, tensile strength and so on. It is verified that the mechanical properties of stainless steel are slightly changed after repair welding process. It is also found from stress corrosion cracking tests that the failure time of repair welding is shorter than that of general welding.

Abstract: Finite element prediction of residual stresses in a 3-bead letterbox-type repair weld is investigated in the present study. The repair is performed on a 2¼CrMo low alloy ferritic steel plate, containing a machined central groove where three weld beads are deposited using AL CROMO S 225 2¼CrMo electrodes. The proposed simulation procedure, which is based on decoupled thermal and mechanical analyses and the “birth and death of elements” technique, is evaluated through comparison of predicted stresses with neutron diffraction testing data. Parametric studies include modelling aspects such as 2-D plane strain versus 3-D analysis, re-melting of weld material during sequential bead deposition, melting of base plate near the fusion line and annealing. It is concluded that numerical results come, in general, in satisfied agreement with the experimental data.

Abstract: Conventionally, shield metal arc welding (SMAW) process was applied to join pipes of RCL, which caused lot of loss in time and cost due to excessive heat input and defects in joining section. Recently, narrow-gap welding (NGW) process was introduced to overcome the disadvantages of SMAW. However, the application of NGW to nuclear power plant is not yet common because safety of NGW process is not proven. In present paper, the welded coupons are manufactured under different welding processes in carbon steel. Then, microstructure observations and various mechanical tests are performed. It is verified that the mechanical properties of carbon steel are greatly changed after repair welding process due to applied heat flux, and that the effect of post-welding heat treatment is beneficial.