Evaluation of Weld Metal Strength Mismatch in X100 Pipeline Girth Welds

2004 ◽  
Author(s):  
Henryk G. Pisarski ◽  
Yuri Tkach ◽  
Marie Quintana
Keyword(s):  
Fracture Toughness ◽  
Adverse Effects ◽  
Weld Metal ◽  
Axial Stress ◽  
Limit Load ◽  
Allowable Stress ◽  
Simple Method ◽  
Weld Width ◽  
Girth Welds ◽  
Assessment Procedures

A relatively simple method based on standard fracture mechanics flaw assessment procedures, such as BS 7910, but modified using published mismatch limit load solutions is described. It is used to illustrate the effects of weld width and strength mismatch on CTOD requirements for girth welds in Grade X100 strength pipeline material subjected to axial stress. It is shown that fracture toughness requirements based on standard analyses not allowing for mismatch effects can be unnecessarily conservative when either undermatched or overmatched welds are present. Adverse effects of undermatching, in reducing the allowable stress, can be mitigated by reducing weld width. It is shown that even small amounts of overmatching (e.g. 10%) can be beneficial by allowing axial stress to exceed the SMYS of the parent pipe and reducing CTOD requirements.

Fracture Toughness Estimation for Pipeline Girth Welds

2002 ◽  
Author(s):  
Henryk G. Pisarski ◽  
Colin M. Wignall
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Specimen Geometry ◽  
Single Edge ◽  
Single Edge Notch ◽  
Edge Notch ◽  
Loading Modes ◽  
Girth Welds ◽  
The Relationship ◽  
Single Edge Notch Bend

The relationship between fracture toughness estimated using standard single edge notch bend (SENB), single edge notch tension (SENT) test specimens and fracture toughness associated with a circumferential flaw in a pipe girth weld is explored in terms of constraint using the Q parameter. It is shown that in the elastic-plastic regime, use of standard deeply notched SENB specimens provides a conservative assessment of fracture toughness, for both weld metal and HAZ, because of the high constraint associated with this specimen geometry. Use of specimen geometries and loading modes associated with lower constraint (e.g. SENT and shallowed notched SENB specimens), allow for improved estimates of fracture toughness to be made that are appropriate for the assessment of circumferential flaws in pipe girth welds. Recommendations are given on the specimen designs and notch orientations to be employed when evaluating weld metal and HAZ fracture toughness.

scholarly journals Effect of Weld Strength Mismatch and Weld Width on the Fracture Toughness Determined From SENB Specimens

2018 ◽  
Author(s):  
Philippa L. Moore ◽  
Natalia Garban ◽  
Philippe Bastid ◽  
Kevin Hughes
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Weld Strength ◽  
Material Strength ◽  
Homogeneous Material ◽  
Fracture Toughness Test ◽  
Standard Methods ◽  
Weld Width ◽  
Metal Fracture ◽  
Toughness Test

In fracture toughness test standard BS EN ISO 15653 for weld and HAZ specimens, there is limited guidance about how the weld width, and the weld metal to parent yield strength mismatch ratio can affect the fracture toughness of materials, nor how to interpret the results should these parameters fall outside the permitted limits given in the Standard. This research was carried out to evaluate how the values of J determined from fracture toughness test results are affected by the weld width and weld strength mismatch, by using FEA models of single edge notched bend (SENB) specimens. Fracture toughness results from specimens notched into the weld centreline, of different mismatch ratios and weld widths, are compared with homogeneous materials specimens. The results show that for any mismatch ratio, fracture toughness for welds wider than 20mm are similar to homogeneous material. However, the fracture toughness decreases as the weld become narrower than 20mm. When this variation is taken as a percentage between a homogeneous material and a welded specimen, J varies for each weld width following the same trend for a specific mismatch ratio, independently of the material strength. To enable prediction of the fracture toughness behaviour of welded specimens, equations have been developed for comparison to homogeneous weld metal or homogeneous parent metal, as a function of the weld mismatch ratio and the weld width. The real question is whether the Standard methods can nonetheless determine weld metal fracture toughness accurately in overmatched welds of different widths. From comparisons of J values extracted directly from the contour integral, and J values calculated using the standard equation (but based on load-CMOD data), it was found that standard methods vary by less than 5% in the majority of the cases. The exception was for the combination of mismatch ratio above 1.46 and welds narrower than 20mm. Therefore, it could be said that the Standard BS EN ISO 15653 is conservative with the overestimation percentage of 10%, since all model cases within the Standard limits of mismatch of 1.5, the largest over-estimation was only 6%, and typically less than 4%.

Mechanical Properties and Microstructure of Weld Metal and HAZ Regions in X100 Single and Dual Torch Girth Welds

2010 ◽  
Author(s):  
James Gianetto ◽  
William Tyson ◽  
Yong-Yi Wang ◽  
John Bowker ◽  
Dong-Yeob Park ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Weld Metal ◽  
Welding Process ◽  
T Test ◽  
Fusion Line ◽  
Small Scale ◽  
Single Edge ◽  
Testing Procedures ◽  
Girth Welds

The main objectives of the current study were to further develop tensile and toughness testing protocols and to provide a better understanding of the factors that control both weld metal and HAZ microstructure and properties in pipeline girth welds. In this investigation, two series of rolled (1G) girth welds were made in X100 pipe of 36 in. diameter and 0.750 in. wall thickness using two pulsed-gas metal arc welding process variants: single and dual torch. The small-scale testing program included evaluations of all-weld-metal tensile strength, Charpy impact and standard fracture toughness measured by single-edge bend SE(B) tests, along with preliminary fracture toughness results using a single-edge tension SE(T) test developed at CANMET. Additional information was obtained from detailed microstructural characterizations of weld metal and HAZ regions along with microhardness testing. All-weld-metal tensile tests using round and strip tensile specimens showed variations with through-thickness location and in some case with clock position. Full stress-strain curves were generated, and 0.2% offset yield strength, flow stress, ultimate tensile strength, and uniform strain were measured and compared with pipe properties using calculated weld strength mismatch factors based on these properties. Charpy V-notch transition curves were generated for both weld metal and HAZ (notched within 0.5 mm of the fusion line). Fracture toughness of both weld metal and HAZ regions of single torch welds was assessed using standard SE(B) testing procedures with Bx2B preferred specimens notched through–thickness at the weld centerline and in the HAZ (within 0.5 mm of the fusion line). Full J-resistance curves were measured using SE(T) tests of surface-notched WM and HAZ specimens; the SE(T) test was designed to match the constraint of full-size pipeline girth welds.

Effect of Chemistry on the Fracture Toughness of Low Carbon X70 Girth Weld Heat Affected Zone

2014 ◽  
Author(s):  
M. Rashid ◽  
L. E. Collins ◽  
Y. Bian
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Heat Affected Zone ◽  
High Strength ◽  
Carbon Equivalent ◽  
Welding Parameters ◽  
Low Carbon ◽  
Girth Welds ◽  
Ferrite Nucleation ◽  
Linepipe Steel

Addition of alloying elements can alter the properties of high-strength linepipe steel. Particularly the addition of Chromium and Molybdenum acts to suppress ferrite nucleation and promote the formation of acicular bainite microstructures and thereby increase the tensile properties of modern linepipe steel. While chemistry is a factor, welding parameters can also be influential and affect the HAZ toughness. The present work compares the effect of C, Cr, and Mo on the girth weld HAZ fracture toughness of X70 in identical welds. Three pipes of size 48″ OD × 0.528″ WT with different combinations of C, Cr, and Mo were produced. Identical welding procedures were employed to produce two girth welds so that a low-C, Cr pipe (CE = 0.238) was joined to a high-C, Cr pipe (CE = 0.268) which in turn was joined to a low-C, Mo pipe (CE = 0.224). By evaluating the HAZ properties on either side of a weld, it was possible to accurately assess chemistry affects on HAZ properties. These girth welds were subjected to different testing for the evaluation of girth weld HAZ impact and fracture toughness. These included all-weld metal and pipe body tensile testing, micro hardness testing of HAZ, microstructure analysis, Charpy V-notch testing of weld metal and HAZ, and CTOD testing of weld metal and HAZ at −5 °C and −20 °C. In addition, to investigate the transformation behaviour, Gleeble simulations of coarse-grain heat affected zone (CG-HAZ) were conducted using skelp samples, which were taken from the same coils as the pipe samples. The results demonstrated that among the low and high carbon equivalent (CE) alloys, materials with low CE values showed better toughness properties. While among the low CE materials, the material with high Mo performed better in terms of toughness. No clear effect of weld position around the pipe circumference on the CTOD values was observed.

Analysis and Testing of a 13Cr Pipeline to Demonstrate “Leak Before Break”

2012 ◽  
Author(s):  
Robert M. Andrews ◽  
Neil Millwood ◽  
Sanjay Tiku ◽  
Nick Pussegoda ◽  
Menno Hoekstra ◽  
...  
Keyword(s):  
Fracture Mechanics ◽  
Weld Metal ◽  
Limit Load ◽  
Parent Material ◽  
Full Scale ◽  
Small Scale ◽  
Element Analysis ◽  
Girth Welds ◽  
Full Scale Tests ◽  
Leak Before Break

As part of a safety case for a subsea 13Cr pipeline, the operator wished to demonstrate that if a circumferential through wall crack developed, the crack would remain stable as a leak rather than growing to a full bore rupture. An initial fracture mechanics analysis had suggested that the margins on crack length were too small to make such a “leak before break” argument. This paper reports an integrated programme of small scale testing, numerical modelling and full scale testing which showed that a leak before break case could be made. 13Cr martensitic steel generally shows excellent toughness at the service temperature, as does the super duplex weld metal that was used for the girth welds. However, as the pipeline had been installed by reeling, there was some concern that the toughness may have been reduced. Hence a programme of fracture toughness testing was designed to generate tearing resistance curves for both as-received and pre-strained parent material and weld metal. Deep and shallow through thickness notched specimen geometries were tested to explore the effect of constraint on the toughness. Finite element analysis was used to predict the stress intensity for a range of crack lengths, including the effects of misalignment. Non-linear analyses were used to estimate the limit load for the cracked pipe. The test results were used as input to tearing analyses to Level 3 of BS 7910. These showed that the tolerable length of a through wall crack exceeded the length of anticipated defects by a factor of at least two. To confirm the fracture mechanics predictions, two full scale tests were carried out. These used pressure cycling to grow a through wall crack by fatigue. These cracks were stable under an internal pressure equal to the pipeline design pressure. The cracked specimens were then axially loaded to failure. Extensive tearing occurred before final failure at loads above those predicted by the fracture analysis, confirming the conservatism of the predictions.

NIMROD 617KS

Alloy Digest ◽  
2002 ◽  
Vol 51 (5) ◽  
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Weld Metal ◽  
Tensile Properties ◽  
Base Metal ◽  
Heat Treating ◽  
Nominal Composition

Abstract Nimrod 617KS is an Inconel-type consumable with a nominal composition of nickel, 24% Cr,12% Co, and 9% Mo and is used to join UNS N06617 and Nicrofer 6023 to themselves. The alloy is designed for high-temperature service and is often used as the weld metal in dissimilar cases to ensure the weld is as strong as the base metal. This datasheet provides information on composition, hardness, and tensile properties as well as fracture toughness. It also includes information on heat treating and joining. Filing Code: Ni-583. Producer or source: Metrode Products Ltd.

UNIFLUX VCM 125

Alloy Digest ◽  
1978 ◽  
Vol 27 (1) ◽  
Keyword(s):  
Carbon Dioxide ◽  
Fracture Toughness ◽  
Weld Metal ◽  
Heat Treating ◽  
Carbon Steels ◽  
Low Alloy Steels ◽  
Electrode Wire ◽  
Molybdenum Steel ◽  
Alloy Steels ◽  
Welding Electrode

Abstract UNIFLUX VCM 125 is a continuous flux-cored welding electrode (wire) that is used to deposit 1 1/4% chromium-1/2% molybdenum steel for which it was developed. Welding is protected by a shielding atmosphere of 100% carbon dioxide. This electrode also may be used to weld other low-alloy steels and carbon steels; however, the weld metal may differ somewhat from 1 1/4% chromium-1/2% molybdenum because of weld-metal dilution. When Uniflux VCM 125 is used to weld 1 1/4% chromium-1/2% molybdenum steel, it provides 95,000 psi tensile strength at 70 F and 24 foot-pounds Charpy V-notch impact at 40 F. This datasheet provides information on composition, physical properties, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as heat treating, machining, and joining. Filing Code: SA-340. Producer or source: Unicore Inc., United Nuclear Corporation.

Dynamic fracture toughness (JId) behavior of armor-grade Q&T steel weldments: Effect of weld metal composition and microstructure

2009 ◽  
Vol 15 (6) ◽  
pp. 1017-1026 ◽  
Author(s):  
Govindaraj Magudeeswaran ◽  
Visvalingam Balasubramanian ◽  
S. Sathyanarayanan ◽  
Gankidi Madhusudhan Reddy ◽  
A. Moitra ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Weld Metal ◽  
Dynamic Fracture ◽  
Dynamic Fracture Toughness ◽  
Metal Composition ◽  
Weld Metal Composition

scholarly journals Microstructure and Fracture Toughness of Fe–Nb Dissimilar Welded Joints

Metals ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 86
Author(s):  
Qiaoling Chu ◽  
Lin Zhang ◽  
Tuo Xia ◽  
Peng Cheng ◽  
Jianming Zheng ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Weld Metal ◽  
Thermal Cycle ◽  
Peak Load ◽  
Local Phase ◽  
Weld Formation ◽  
Lamellar Structures ◽  
Average Hardness ◽  
Radial Cracks

The relation between the microstructure and mechanical properties of the Fe–Nb dissimilar joint were investigated using nanoindentation. The weld metal consists mainly of Fe2Nb, α-Fe + Fe2Nb, Nb (s,s) and Fe7Nb6 phases. Radial cracks initiate from the corners of the impressions on the Fe2Nb phase (~20.5 GPa) when subjected to a peak load of 300 mN, whereas the fine lamellar structures (α-Fe + Fe2Nb) with an average hardness of 6.5 GPa are free from cracks. The calculated fracture toughness of the Fe2Nb intermetallics is 1.41 ± 0.53 MPam1/2. A simplified scenario of weld formation together with the thermal cycle is proposed to elaborate the way local phase determined the mechanical properties.

Simple Method for Evaluating of Fracture Toughness of Metallic Materials Utilizing Tensile Properties.

1997 ◽  
Vol 63 (611) ◽  
pp. 1437-1441 ◽  
Author(s):  
Naoto SHIRAKI ◽  
Shigeru NAKAYAMA ◽  
Yoshihiro SUGIYAMA ◽  
Katsutoshi ASAMI
Keyword(s):  
Fracture Toughness ◽  
Tensile Properties ◽  
Metallic Materials ◽  
Simple Method
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