الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 127 |  |  |
| | | from | 127 | | |
Abstract
Duplex stainless steels (DSSs) are gaining extensively increased applications as structural
materials in various industrial sectors, such as offshore construction, chemical, petrochemical,
pulp and paper, power generation, desalination, as well as oil and gas. DSSs have superior
mechanical properties and corrosion characteristics relative to other stainless steels and
structural steels. However, it was reported that 2205 DSS is susceptible to intergranular stress
corrosion cracking (lGSCC) as a result of high weld-induced tensile residual stresses. Tensile
residual stresses are generally detrimental, increasing the susceptibility of a weld to fatigue
damage, stress corrosion cracking, and fracture. Therefore, a good estimation of weld-induced
residual stresses field is thus needed. Recently, in view of increasing applications of DSSs, it
is important to have a better understanding of the issues associated with its welds to dissimilar
metals.
A three-dimensional sequentially coupled thermo-me~hanical transient finite element model
(FEM) has been developed to estimate the weld pool geometry and size and to analyze the
temperature field, weld thermal cycles, and residual stresses due to the keyhole plasma arc
welding (PA W) in 2205 DSS butt-welded plate. An adaptive heat source model is proposed
for the numerical analysis of the process, considering the ”bugle-like” configuration feature of
keyhole PA W welds. The thermal analysis has revealed temperature contours that indicate the
size and geometry of the weld fusion zone. The initial models are validated against
experimental data and show very good correlation. Such good correlation indicates the validity
of the numerical heat transfer model and the analytical model of molten metal flow. A variety
of welding heat inputs are then simulated. Effect of welding heat input on the size and
geometry of the weld fusion zone and the distribution of residual stresses were investigated.
The results indicated that the peak longitudinal tensile residual stresses on the top surface of
2205 DSS plate near the WCL are above the yield strength of the material at room temperature
so that it can accordingly contribute to expanding crack propagation