Microstructure, Hardness, and Residual Stress Distributions in T-Joint Weld of HSLA S500MC Steel
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INTRODUCTION
HIGH-strength low-alloy (HSLA) steels are widely used for the welded constructions in various domains (transport, construction, off-shore structures, etc.) due to their good weldability, high yield strength, toughness, and formability as is described by Manganello.[1] However, the mechanical properties of HSLA steel can be changed due to welding process and more exactly due to the heat input and the cooling rate.[2] The phase transformation induced by welding process and heterogeneous plastic deformation lead to the modification of the microstructure in the weld metal (WM) and the heat-affected zone (HAZ) which can deteriorate the performance of the welding structure and lead to the appearance of residual stresses as demonstrated by Scholtes[3] and Lu.[4] Maddox[5] and Zhang[6] found that the modification of the grain size and the transformation of phases during cooling have an impact on the levels of welding residual stresses and hardness distribution which may cause fatigue strength diminution. Recently, several studies have investigated the influence of the grain size and phases transformation on microstructure, hardness, and residual stresses in the different regions of HSLA steel butt-welded joint.[7,8] Alipooramirabada,[9] noted that high level of residual stresses and hardness might be correlated with the presence of bainite and Widmansta¨tten ferrite in the fusion zone. Oyyaravelu[2] found a good correlation between the microstructure of HSLA steel weld and their mechanical properties. Nathan[10] demonstrated that high hardness values are related to the presence of bainitic ferrite, carbides, and acicular ferrite in the WM. However, there are few
INTISSAR FRIH, GUILLAUME MONTAY, and PIERREANTOINE ADRAGNA are with LASMIS, UMR ICD 6281, University of Technology of Troyes, 12 rue Marie Curie, 10004 Troyes Cedex, France. Contact e-mail: [email protected] Manuscript submitted May 7, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
studies on the characterization of HSLA steel T-weld joint. For this, in the present study, the microstructure, hardness, and residual stress of the T-weld joint have been studied. Residual stress is an essential factor when evaluating the integrity of welded structure. The contour method (CM) was chosen to evaluate the residual stress across the full surface of the T-weld. This method is widely used to evaluate the residual stress in thickwelded joints.[11–13] It is a destructive technique that gives a longitudinal residual stress map over the whole cutting surface. The CM consists of four main steps: (1) specimen cutting, (2) displacements measuring, (3) surface data processing, and (4) residual stress calculation by finite elements method (FEM). Several researchers have studied the credibility of the results given by the CM for welding components. Prime et al.[14] found an acceptable agreement between measurement given by CM and those of neutron diffraction method for a welded sample. Kartal et al.[15] confirmed a good agreement between these two techniques used to meas
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