An Optimized Heat Treatment Process to Reduce the Weld Residual Stress by Auxiliary Heating

2019 ◽  
Author(s):  
Yun Luo ◽  
Teng Gao ◽  
Wenchun Jiang
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Residual Stresses ◽  
Axial Stress ◽  
Axial Direction ◽  
Auxiliary Heating ◽  
Weld Residual Stress ◽  
Before And After ◽  
Weld Toe ◽  
Stress And Deformation

Abstract Local post welding heat treatment (PWHT) is a popular method to reduce the residual stress of bigger weld structures. In this paper, the weld residual stresses before and after local PWHT were investigated. The results show that there are larger axial stresses concentration in weld toe and an inconsistent deformation along axial direction during heating stage which may leads to crack. The residual stresses in outer surface are decreased greatly after local PWHT. An optimized local PWHT with auxiliary heating (AH) temperature 800°C and width 800mm were proposed. The axial stress and deformation inconsistent in weld can be reduced by AH, thus leads to the reduction of crack risk in weld toe.

Residual Stresses in Steel-Titanium Composite Manufactured by Explosive Welding

2012 ◽  
Vol 726 ◽  
pp. 125-132 ◽  
Author(s):  
Aleksander Karolczuk ◽  
Krzysztof Kluger ◽  
Mateusz Kowalski ◽  
Fabian Żok ◽  
Grzegorz Robak
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Residual Stresses ◽  
Hole Drilling ◽  
Element Analysis ◽  
Welded Steel ◽  
Hole Drilling Method ◽  
Drilling Method ◽  
Before And After ◽  
Stress States

The main aim of the paper is determination of residual stresses in explosively welded steel-titanium bimetal. The analysis considers two bimetallic specimens: before and after the heat treatment. In residual stress determination the hole drilling method along with finite element analysis were applied. The results show different residual stress states depending on the heat treatment. The obtained results are confirmed by thermal stress calculation.

Research on the Vibratory Stress Relief Used to Reduce Residual Stress of Mismatch Butt Welds of a Cylinder

2007 ◽  
Author(s):  
Xin Ren ◽  
Yuan Tian ◽  
Zengliang Gao ◽  
Kangda Zhang
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Relief ◽  
Butt Weld ◽  
Butt Welds ◽  
Blind Hole ◽  
Dissimilar Steel ◽  
Weld Residual Stress ◽  
Before And After

The residual stresses of mismatch butt welds of a cylinder were measured by the blind-hole method before and after a vibratory residual stress relief treatment. The results show that this treatment could greatly reduce the maximal butt weld residual stress of dissimilar steel from 540MPa to 119MPa. The concentrated distributions of the first and the second principal residual stresses became gentle after the vibratory residual stress relief treatment.

Effect of Ageing on Residual Stresses in a Girth Welded Stainless Steel 316 L Pipe

2019 ◽  
Author(s):  
R. J. Coulthard ◽  
M. Mostafavi ◽  
C. E. Truman
Keyword(s):  
Residual Stress ◽  
Stainless Steel ◽  
Residual Stresses ◽  
Service Use ◽  
Hole Drilling ◽  
Stainless Steel 316L ◽  
Weld Residual Stress ◽  
Before And After ◽  
Maximum Residual Stress ◽  
Stainless Steel 316

Abstract Residual stresses within welded components can redistribute when exposed to high temperatures and large levels of loading. The ageing process for a specimen attempts to replicate the temperature regime experienced during typical service use of the component, redistributing stresses from the as-welded condition to post-ageing. The aim of this investigation was to study the effects of ageing on weld residual stress redistribution and to evaluate the changes in the residual stress profiles before and after the pipe had been aged. In this investigation the through thickness residual stresses within a narrow gap girth TIG welded stainless steel 316L pipe were measured. The ageing of the pipe specimen involved heating to 400°C for 3000 hours. To measure residual stress the incremental Deep-Hole Drilling (iDHD) method was employed; two measurements were taken, once before and after ageing. Analysis of the measured pre and post-ageing residual stresses showed a consistent reduction in the magnitude of approximately 50 MPa, corresponding to the change in the yield stress of the material at room and elevated (400°C) temperatures; the maximum residual stress, of 450 MPa, was measured at 4 mm from the external surface of the pipe.

scholarly journals Residual Stress State of X65 Pipeline Girth Welds Before and After Local and Furnace Post Weld Heat Treatment

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Yao Ren ◽  
Anna Paradowska ◽  
Bin Wang ◽  
Elvin Eren ◽  
Yin Jin Janin
Keyword(s):  
Heat Treatment ◽  
Residual Stress ◽  
Residual Stresses ◽  
Outer Surface ◽  
Post Weld Heat Treatment ◽  
Pipe Length ◽  
Stress Profiles ◽  
Girth Welds ◽  
Welded Pipe ◽  
Weld Heat

This research investigated the effects of global (in other words, furnace-based) and local post weld heat treatment (PWHT) on residual stress (RS) relaxation in API 5L X65 pipe girth welds. All pipe spools were fabricated using identical pipeline production procedures for manufacturing multipass narrow gap welds. Nondestructive neutron diffraction (ND) strain scanning was carried out on girth welded pipe spools and strain-free comb samples for the determination of the lattice spacing. All residual stress measurements were carried out at the KOWARI strain scanning instrument at the Australian Nuclear Science and Technology Organization (ANSTO). Residual stresses were measured on two pipe spools in as-welded condition and two pipe spools after local and furnace PWHT. Measurements were conducted through the thickness in the weld material and adjacent parent metal starting from the weld toes. Besides, three line-scans along pipe length were made 3 mm below outer surface, at pipe wall midthickness, and 3 mm above the inner surface. PWHT was carried out for stress relief; one pipe was conventionally heat treated entirely in an enclosed furnace, and the other was locally heated by a flexible ceramic heating pad. Residual stresses measured after PWHT were at exactly the same locations as those in as-welded condition. Residual stress states of the pipe spools in as-welded condition and after PWHT were compared, and the results were presented in full stress maps. Additionally, through-thickness residual stress profiles and the results of one line scan (3 mm below outer surface) were compared with the respective residual stress profiles advised in British Standard BS 7910 “Guide to methods for assessing the acceptability of flaws in metallic structures” and the UK nuclear industry's R6 procedure. The residual stress profiles in as-welded condition were similar. With the given parameters, local PWHT has effectively reduced residual stresses in the pipe spool to such a level that it prompted the thought that local PWHT can be considered a substitute for global PWHT.

Weld Residual Stress in Large Diameter Nuclear Nozzles

2011 ◽  
Author(s):  
Tao Zhang ◽  
F. W. Brust ◽  
Gery Wilkowski
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Nuclear Power ◽  
Kinematic Hardening ◽  
Large Diameter ◽  
Thick Wall ◽  
Isotropic Hardening ◽  
Residual Stress Field ◽  
Mixed Hardening ◽  
Weld Residual Stress

Weld residual stresses in nuclear power plant can lead to cracking concerns caused by stress corrosion. These are large diameter thick wall pipe and nozzles. Many factors can lead to the development of the weld residual stresses and the distributions of the stress through the wall thickness can vary markedly. Hence, understanding the residual stress distribution is important to evaluate the reliability of pipe and nozzle joints with welds. This paper represents an examination of the weld residual stress distributions which occur in various different size nozzles. The detailed weld residual stress predictions for these nozzles are summarized. Many such weld residual stress solutions have been developed by the authors in the last five years. These distributions will be categorized and organized in this paper and general trends for the causes of the distributions will be established. The residual stress field can therefore feed into a crack growth analysis. The solutions are made using several different constitutive models such as kinematic hardening, isotropic hardening, and mixed hardening model. Necessary fabrication procedures such as repair, overlay and post weld heat treatment are also considered. Some general discussions and comments will conclude the paper.

On the Mechanics of Residual Stresses in Girth Welds

2006 ◽  
Vol 129 (3) ◽  
pp. 345-354 ◽  
Author(s):  
P. Dong
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Relative Importance ◽  
Stress Distributions ◽  
Unified Framework ◽  
Joint Geometry ◽  
Weld Residual Stress ◽  
Girth Welds ◽  
Welding Procedure

In this paper, some of the important controlling parameters governing weld residual stress distributions are presented for girth welds in pipe and vessel components, based on a large number of residual stress solutions available to date. The focus is placed upon the understanding of some of the overall characteristics in through-wall residual stress distributions and their generalization for vessel and pipe girth welds. In doing so, a unified framework for prescribing residual stress distributions is outlined for fitness-for-service assessment of vessel and pipe girth welds. The effects of various joint geometry and welding procedure parameters on through thickness residual stress distributions are also demonstrated in the order of their relative importance.

Weld Residual Stress and Fracture Behavior of NASA Layered Pressure Vessels

2019 ◽  
Author(s):  
F. W. Brust ◽  
R. H. Dodds ◽  
J. Hobbs ◽  
B. Stoltz ◽  
D. Wells
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Fracture Behavior ◽  
Service Evaluation ◽  
Pressure Vessels ◽  
Weld Residual Stress ◽  
Proof Testing ◽  
Fracture Assessment ◽  
High Level ◽  
Initial Results

Abstract NASA has hundreds of non-code layered pressure vessel (LPV) tanks that hold various gases at pressure. Many of the NASA tanks were fabricated in the 1950s and 1960s and are still in use. An agency wide effort is in progress to assess the fitness for continued service of these vessels. Layered tanks typically consist of an inner liner/shell (often about 12.5 mm thick) with different layers of thinner shells surrounding the inner liner each with thickness of about 6.25-mm. The layers serve as crack arrestors for crack growth through the thickness. The number of thinner layers required depends on the thickness required for the complete vessel with most tanks having between 4 and 20 layers. Cylindrical layers are welded longitudinally with staggering so that the weld heat affected zones do not overlap. The built-up shells are then circumferentially welded together or welded to a header to complete the tank construction. This paper presents some initial results which consider weld residual stress and fracture assessment of some layered pressure vessels and is a small part of the much larger fitness for service evaluation of these tanks. This effort considers the effect of weld residual stresses on fracture for an inner layer longitudinal weld. All fabrication steps are modeled, and the high-level proof testing of the vessels has an important effect on the final WRS state. Finally, cracks are introduced, and service loading applied to determine the effects of WRS on fracture.

Simple Benchmark Problems for Finite Element Weld Residual Stress Simulation

2013 ◽  
Author(s):  
Mike C. Smith ◽  
Steve Bate ◽  
P. John Bouchard
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Phase Transformation ◽  
Solid State ◽  
Residual Stresses ◽  
Benchmark Problems ◽  
Transient Temperature ◽  
Beam Specimen ◽  
Weld Residual Stress ◽  
Solid State Phase Transformation

Finite element methods are used increasingly to predict weld residual stresses. This is a relatively complex use of the finite element method, and it is important that its practitioners are able to demonstrate their ability to produce accurate predictions. Extensively characterised benchmark problems are a vital tool in achieving this. However, existing benchmarks are relatively complex and not suitable for analysis by novice weld modellers. This paper describes two benchmarks based upon a simple beam specimen with a single autogenous weld bead laid along its top edge. This geometry may be analysed using either 3D or 2D FE models and employing either block-dumped or moving heat source techniques. The first, simpler, benchmark is manufactured from AISI 316 steel, which does not undergo solid state phase transformation, while the second, more complex, benchmark is manufactured from SA508 Cl 3 steel, which undergoes solid state phase transformation during welding. A number of such beams were manufactured using an automated TIG process, and instrumented with thermocouples and strain gauges to record the transient temperature and strain response during welding. The resulting residual stresses were measured using diverse techniques, and showed markedly different distributions in the austenitic and ferritic beams. The paper presents the information necessary to perform and validate finite element weld residual stress simulations in both the simple austenitic beam and the more complex ferritic beam, and provides performance measures for the austenitic beam problem.

The Effect of Specimen Size on the Determination of Residual Stress in Polymer Pipe Wall

2014 ◽  
Vol 627 ◽  
pp. 141-144 ◽  
Author(s):  
Jan Poduška ◽  
Jaroslav Kučera ◽  
Pavel Hutař ◽  
Martin Ševčík ◽  
J. Křivánek ◽  
...  
Keyword(s):  
Residual Stress ◽  
Axial Stress ◽  
Three Dimensional ◽  
Axial Direction ◽  
Polymer Materials ◽  
Axial Residual Stress ◽  
Axial Dimension ◽  
Measured Deformation ◽  
Different Dimensions

As a result of the production process, there are axial and tangential residual stresses present in pressure pipes made of polymer materials such as polyethylene or polypropylene. The residual stress magnitude and distribution have a significant influence on the pipe lifetime. In this contribution the results from experiments focused on determining the tangential residual stress distribution in the walls of polypropylene pipes of different dimensions are compared. The experimental method used involves measuring the deformation of ring shaped specimens that were slit in the axial direction. Measured deformation of the ring specimen is a result of the tangential and axial stress superposition. However, the effect of the axial residual stress depends on the specimen axial dimension and tangential residual stress estimated basing on experimental data should be corrected according to axial dimension of the specimen used. The correction suggested in this article is determined based on three-dimensional FEM simulations of the experiment.

Effects of Weld Geometry on Residual Stress and Crack Driving Force for Centerhole Control Rod Drive Mechanism Nozzles: Part I — Weld Residual Stress

2005 ◽  
Author(s):  
Wentao Cheng ◽  
David L. Rudland ◽  
Gery Wilkowski ◽  
Wallace Norris
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Driving Force ◽  
Nuclear Regulatory Commission ◽  
Crack Driving Force ◽  
Control Rod ◽  
Drive Mechanism ◽  
Weld Geometry ◽  
Weld Residual Stress ◽  
Regulatory Commission

The U.S. Nuclear Regulatory Commission (NRC) has undertaken a program to assess the integrity of control rod drive mechanism (CRDM) nozzles in existing plants that are not immediately replacing their RPV heads. This two-part paper summarizes some of the efforts undertaken on the behalf of the U.S.NRC for the development of detailed residual stress and circumferential crack-driving force solutions to be used in probabilistic determinations of the time from detectable leakage to failure. In this first paper, the finite element (FE) simulations were conducted to investigate the effects of weld geometry on the residual stresses in the J-weld for a centerhole CRDM nozzle. The variables of weld geometry included three weld heights (weld sizes) and three groove angles for each weld height while keeping the same weld size. The analysis results indicate that the overall weld residual stress decreases as the groove angle increases and higher residual stress magnitude is associated with certain weld height. The results also reveal that the axial residual stresses in the Alloy 600 tube are very sensitive to the weld height, and that the tube hoop stresses above the J-weld root increase with the increasing weld height.

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