Effect on Hardness and Microstructures of Rail Joint with Ultra-Narrow Gap Arc Welding by Post Weld Heat Treatment

2017 ◽  
Vol 737 ◽  
pp. 90-94 ◽  
Author(s):  
Lian Gong ◽  
Liang Zhu ◽  
Hong Xiang Zhou
Keyword(s):  
Heat Treatment ◽  
Arc Welding ◽  
Weld Seam ◽  
Stress Relief ◽  
Post Weld Heat Treatment ◽  
Test Results ◽  
Narrow Gap ◽  
Narrow Gap Welding ◽  
Scanning Electron ◽  
Weld Heat

U71Mn rails were welded by ultra-narrow gap welding with constrained arc by flux strips，then normalizing treatment and stress relief annealing were performed for the joints. Another sample with no heat treatment, was studied in comparison. The effect of post weld heat treatment on the hardness and microstructure of rail joint were studied by scanning electron microscope (SEM) and microhardness test. The test results showed that normalizing treatment can improve the hardness of weld seam and base metal, and stress relief annealing couldn’t improve the hardness of joints obviously.

scholarly journals The Influence of the Post-Weld Heat Treatment on the Microstructure of Inconel 625/Carbon Steel Bimetal Joint Obtained by Explosive Welding

Metals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 246 ◽  
Author(s):  
Robert Kosturek ◽  
Marcin Wachowski ◽  
Lucjan Śnieżek ◽  
Michał Gloc
Keyword(s):  
Heat Treatment ◽  
Diffusion Zone ◽  
Explosive Welding ◽  
Stress Relief ◽  
Scanning Transmission Electron Microscope ◽  
Post Weld Heat Treatment ◽  
Inconel 625 ◽  
Scanning Transmission ◽  
Inconel 625 Alloy ◽  
Weld Heat

Inconel 625 and steel P355NH were bonded by explosive welding in this study. Explosively welded bimetal clad-plate was subjected to the two separated post-weld heat treatment processes: stress relief annealing (at 620 °C for 90 min) and normalizing (at 910 °C for 30 min). Effect of heat treatments on the microstructure of the joint has been evaluated using light and scanning electron microscopy, EDS analysis techniques, and microhardness tests, respectively. It has been stated that stress relief annealing leads to partial recrystallization of steel P355NH microstructure in the joint zone. At the same time, normalizing caused not only the recrystallization of both materials, but also the formation of a diffusion zone and precipitates in Inconel 625. The precipitates in Inconel 625 have been identified as two types of carbides: chromium-rich M23C6 and molybdenum-rich M6C. It has been reported that diffusion of alloying elements into steel P355NH takes place along grain boundaries with additional formation of voids. Scanning transmission electron microscope observation of the grain microstructure in the diffusion zone shows that this area consists of equiaxed grains (at the side of Inconel 625 alloy) and columnar grains (at the side of steel P355NH).

Residual Stress Relaxation in a Tube Attachment Weld Inside a Pressure Vessel Forging During Post Weld Heat Treatment

2007 ◽  
Author(s):  
P. R. Hurrell ◽  
J. Davies ◽  
N. A. Leggatt ◽  
R. J. Dennis ◽  
R. H. Leggatt
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Stress Relaxation ◽  
Pressure Vessel ◽  
Hold Time ◽  
Stress Relief ◽  
Post Weld Heat Treatment ◽  
Secondary Creep ◽  
Axial Tensile ◽  
Weld Heat

This paper presents analyses done to determine residual stress relief achieved by post weld heat treatment (PWHT) of tube attachment welds inside a thick SA508 steel pressure vessel forging. Finite element (FE) analyses were performed modelling the manufacturing operations in detail including welding, machining and PWHT. The analyses demonstrate that PWHT at 600°C for 8 hours is effective in reducing as-welded residual stress levels from tensile yield magnitude (+500MPa approx) to <100MPa. The maximum residual stress was computed to be 90MPa sub-surface in a region of hydrostatic (tri-axial tensile) stress. Secondary creep was modelled using data from creep tests on SA508 steel uni-axial tensile specimens. Practically all of the stress relaxation is due to creep strain with minimal additional plastic strain. Most stress relief occurs during the first hour of soak, with diminishing benefit thereafter. Analysis results also indicate that PWHT effectiveness is more sensitive to soak temperature than hold time. These FE results are considered slightly pessimistic but are reasonably consistent with other analytical predictions. By comparison surface hole drilling stress measurements of <50MPa (10% yield strength) were recorded from a representative welded test block. Analysis pessimism was attributed to ignoring both primary creep and relaxation during the slow warm up phase of the heat treatment cycle.

scholarly journals The Influence of Post-Weld Heat Treatment on the Microstructure and Fatigue Properties of Sc-Modified AA2519 Friction Stir-Welded Joint

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 583 ◽  
Author(s):  
Robert Kosturek ◽  
Lucjan Śnieżek ◽  
Marcin Wachowski ◽  
Janusz Torzewski
Keyword(s):  
Heat Treatment ◽  
Precipitation Hardening ◽  
Low Cycle Fatigue ◽  
True Strain ◽  
Welding Process ◽  
Post Weld Heat Treatment ◽  
Fatigue Properties ◽  
Friction Stir ◽  
Scanning Electron ◽  
Weld Heat

The aim of this research was to investigate the influence of post-weld heat treatment (PWHT, precipitation hardening) on the microstructure and fatigue properties of an AA2519 joint obtained in a friction stir-welding process. The welding process was performed with three sets of parameters. One part of the obtained joints was investigated in the as-welded state and the second part of joints was subjected to the post-weld heat treatment (precipitation hardening) and then investigated. In order to establish the influence of the heat treatment on the microstructure of obtained joints both light and scanning electron microscopy observations were performed. Additionally, microhardness analysis for each sample was carried out. Fatigue properties of the samples in the as-welded state and the samples after post-weld heat treatment were established in a low-cycle fatigue test with constant true strain amplitude equal to ε = 0.25% and cycle asymmetry coefficient R = 0.1. Hysteresis loops together with changes of stress and plastic strain versus number of cycles are presented in this paper. The fatigue fracture in tested samples was analyzed with the use of scanning electron microscope. Our results show that post-weld heat treatment of AA2519 friction stir-welded joints significantly decreases their fatigue life.

Finite Element Modelling of a Tube to Vessel Attachment Weld and Local Post-Weld Heat Treatment

2011 ◽  
Author(s):  
Benjamin M. E. Pellereau ◽  
Paul R. Hurrell ◽  
Christopher M. Gill ◽  
Sarah L. Allen
Keyword(s):  
Heat Treatment ◽  
Finite Element ◽  
Pressure Vessel ◽  
Hold Time ◽  
Measurement Data ◽  
Stress Relief ◽  
Post Weld Heat Treatment ◽  
Isotropic Hardening ◽  
Fe Model ◽  
Weld Heat

This paper describes Finite Element (FE) modelling of a weld between a tube and a machined feature on a curved pressure vessel surface. The components were manufactured from a ferritic steel with a matched weld metal deposited by a mechanised TIG process. The weld region then underwent a local Post-Weld Heat Treatment (PWHT) which used heating bands and cooling air flows to control the temperature distribution. The PWHT’s aim was to provide stress relief and HAZ tempering, while minimising the stresses due to thermal gradients in the component. Trial welds on representative test pieces had predicted significant welding-induced distortions. Therefore, during the weld and PWHT, restraints were applied to the tube to prevent excessive deformation. The material behaviour was represented using Abaqus’ built-in material options, with the same properties for both the base metal and the filler. Isotropic hardening was assumed and the stress relaxation during the PWHT was modelled by applying a Norton creep law only during the hold time. Phase transformation effects in the ferritic material were not included. Initial modelling used a 2D axisymmetric model to allow sensitivity studies to inform the development of the PWHT process. These showed that the degree of stress relief was much more sensitive to the soak temperature than the hold time. Subsequent runs analysed a 3D model using a segmented block-dumping technique, with the deposition modelled by introducing the weld elements in 90° segments. The 3D modelling was undertaken in order to more accurately model potentially asymmetric welding distortions and residual stresses. The torch was represented by a body flux into each segment after its introduction. This model was also run without restraint to provide validation by comparing the predicted distortion with measurements from the welding trials; a good match was demonstrated. Further comparisons were made between the predicted stresses and results of Incremental Centre Hole-Drilling (ICHD) stress measurements made on the trial specimens both in the as-welded condition and after PWHT. The measured stresses were close to those predicted by the FE analysis and the key features of the predicted stress field were apparent in the measurement data. Due to the location of the tube’s attachment to the pressure vessel, thermal expansion of the vessel during the PWHT caused the tube to bend. The induced bending stresses were then relaxed during the soak and re-introduced in the opposite sense as the system cooled. This effect was captured by running the analysis as a submodel of a global FE model with displacements read across at nodes in the pressure vessel shell immediately below the weld.

Post-weld Heat Treatment and Groove Angles Affect the Mechanical Properties of T92/Super 304H Dissimilar Steel Weld Joints

2018 ◽  
Vol 37 (7) ◽  
pp. 649-654 ◽  
Author(s):  
Wang Shuo ◽  
Wei Limin ◽  
Cheng Yi ◽  
Tan Shuping
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Weld Metal ◽  
Arc Welding ◽  
Post Weld Heat Treatment ◽  
Steel Weld ◽  
Dissimilar Weld ◽  
Weld Joints ◽  
Gas Tungsten Arc ◽  
Weld Heat

AbstractThe microstructures and mechanical properties of dissimilar weld joints between T92 and Super 304H steels were investigated. Dissimilar weld joints with four groove angles were constructed using gas tungsten arc welding. The results showed that post-weld heat treatment improved the mechanical properties of the dissimilar weld joints. The optimal groove angle for T92/Super 304H dissimilar weld joints was found to be 20°, considering mechanical properties. Furthermore, the transformation from equiaxed dendrites to columnar dendrites was observed in the weld metal. Epitaxial growth and delta ferrites were found around the fusion line between the Super 304H and the weld metal.

An Arrhenius equation-based model to predict the residual stress relief of post weld heat treatment of Ti-6Al-4V plate

2018 ◽  
Vol 32 ◽  
pp. 763-772 ◽  
Author(s):  
Guangxu Yan ◽  
Alexandru Crivoi ◽  
Yajuan Sun ◽  
Niroj Maharjan ◽  
Xu Song ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Arrhenius Equation ◽  
Stress Relief ◽  
Post Weld Heat Treatment ◽  
Weld Heat

Microstructural Evolution and Resulting Mechanical Properties of Weld Joints upon Flux Cored Arc Welding and Post-Weld Heat Treatment

2009 ◽  
Vol 283-286 ◽  
pp. 439-446 ◽  
Author(s):  
Hui Yu ◽  
Kee Sam Shin ◽  
Ji Ling Dong ◽  
Dae Hwang Yoo ◽  
Woong Lee ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Impact Toughness ◽  
Arc Welding ◽  
Compositional Analysis ◽  
Post Weld Heat Treatment ◽  
Grain Structure ◽  
Automatic Welding ◽  
Weld Joints ◽  
Flux Cored Arc Welding ◽  
Weld Heat

The objective of this study is to determine the mechanism of the dramatic increase of impact toughness at low temperatures after post-weld heat treatment on weld joints. In this study, weld joints using two semi-automatic welding consumables were fabricated by flux cored arc welding with subsequent PWHT at 660°C for 65 min and 195 min, respectively. Tests of the tensile and yield strength, microhardness and impact toughness, were carried out. The microstructure was inspected by optical, scanning electron, and transmission electron microscopy in addition to compositional analysis using energy dispersive spectrometry. PWHT was observed to result in grain coarsening, sub-grain structure formation and decrease of the dislocation density. The increase of impact toughness is attributed to the relieved thermal stress, the inclusions and precipitations, softening of the structure, dislocation recovery and sub-grain structure.

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