Development of Optimized Weld Metal Chemistries for Pipeline Girth Welding of High Strength Line Pipe

2008 ◽  
Author(s):  
Susan R. Fiore ◽  
James A. Gianetto ◽  
Mark G. Hudson ◽  
Suhas Vaze ◽  
Shuchi Khurana ◽  
...  
Keyword(s):  
Mechanical Property ◽  
Yield Strength ◽  
Weld Metal ◽  
High Strength ◽  
Process Variations ◽  
Line Pipe ◽  
Girth Welding ◽  
Dimensional Finite Element ◽  
Initial Work ◽  
Girth Welds

The primary objectives of this program were to provide a better understanding of the factors that control strength and toughness in high strength steel girth welds and to develop optimized welding consumables and welding procedures for high strength pipelines. The initial work on the program involved developing cooling rate models so that optimized weld metal compositions for high-strength pipelines could be developed, ensuring that the ideal balance of strength and ductility, together with tolerance to process variations and resistance to hydrogen cracking is achieved. The model, which was developed under a companion program, uses a two-dimensional finite element approach. Complete details can be found in Reference [1]. The model predicts the cooling rates during various weld passes in narrow groove welding of X80 and X100 pipes. Using this model, along with experimental datasets, a neural network model was developed which has been used to predict weld metal properties for various weld metal compositions. Based on the predictions, eight target compositions were selected and were manufactured by one of the team partners. The results of mechanical property testing showed that it was possible to develop weld metal compositions which exceeded the target yield strength of 820 MPa and also provided excellent toughness (>50J at −60°C). It was also found that the weld metal yield strength measured close to the ID of the pipe was significantly higher than that which was measured closer to the OD of the pipe. Complete mechanical property results, including results for round-bar and strip tensiles, CVN impact toughness, microhardness and more, are presented.

Semi-Automatic Gas-Less Process for Girth Welding X-80 Line Pipe

2006 ◽  
Author(s):  
Badri K. Narayanan ◽  
Patrick Soltis ◽  
Marie Quintana
Keyword(s):  
Yield Strength ◽  
Weld Metal ◽  
Slag System ◽  
High Strength ◽  
Automatic Process ◽  
Line Pipe ◽  
High Toughness ◽  
New Process ◽  
Girth Welding ◽  
Acidic Components

A new process (M2M™) to girth weld API Grade X-80 line pipe with a gas-less technology is presented. This process combines innovations in controlling arc length and energy input with microstructure control of the weld metal deposited to achieve high strength (over matching 550 MPa yield strength) and Charpy V-Notch toughness of over 60 Joules at −20°C. This paper will concentrate on the metallurgical aspects of the weld metal and the systematic steps taken to achieve high strength weld metal without sacrificing toughness. The development of an appropriate slag system to achieve the best possible microstructure for high toughness weld metal is discussed. The indirect effects of the slag system on the weld metal composition, which in turn affects the microstructure and physical properties, are detailed. In order to achieve sound weld metal without gas protection using a semi-automatic process, a basic slag system with minimal acidic components is used to improve the cleanliness of the weld metal without sacrificing weldability. In addition, a complex combination of micro-alloying elements is used to achieve the optimum precipitation sequence of nitrides that is critical for high toughness. The final part of this paper gives details about the robustness of this process to weld high strength pipe. The results show that this is a practical and unique solution for girth welding of X-80 pipe to achieve acceptable toughness and over a 15% overmatch in yield strength of X-80 pipe without sacrificing productivity.

Tensile and Toughness Properties of Pipeline Girth Welds

2006 ◽  
Author(s):  
J. A. Gianetto ◽  
J. T. Bowker ◽  
R. Bouchard ◽  
D. V. Dorling ◽  
D. Horsley
Keyword(s):  
Weld Metal ◽  
Welding Process ◽  
Strain Curve ◽  
High Strength ◽  
Primary Objective ◽  
Stress Strain ◽  
Line Pipe ◽  
Arc Welding Process ◽  
Girth Welds ◽  
Metal Microstructure

The primary objective of this study was to develop a better understanding of all-weld-metal tensile testing using both round and strip tensile specimens in order to establish the variation of weld metal strength with respect to test specimen through-thickness position as well as the location around the circumference of a given girth weld. Results from a series of high strength pipeline girth welds have shown that there can be considerable differences in measured engineering 0.2% offset and 0.5% extension yield strengths using round and strip tensile specimens. To determine whether or not the specimen type influenced the observed stress-strain behaviour a series of tests were conducted on high strength X70, X80 and X100 line pipe steels and two double joint welds produced in X70 linepipe using a double-submerged-arc welding process. These results confirmed that the same form of stress-strain curve is obtained with both round and strip tensile specimens, although with the narrowest strip specimen slightly higher strengths were observed for the X70 and X100 linepipe steels. For the double joint welds the discontinuous stress-strain curves were observed for both the round and modified strip specimens. Tests conducted on the rolled X100 mechanized girth welds established that the round bar tensile specimens exhibited higher strength than the strip specimens. In addition, the trends for the split-strip specimens, which consistently exhibit lower strength for the specimen towards the OD and higher for the mid-thickness positioned specimen has also been confirmed. This further substantiates the through-thickness strength variation that has been observed in other X100 narrow gap welds. A second objective of this study was to provide an evaluation of the weld metal toughness and to characterize the weld metal microstructure for the series of mechanized girth welds examined.

Effect of Strain Ageing on Mechanical Properties of Pipeline Girth Welds

2011 ◽  
Author(s):  
Badri K. Narayanan ◽  
Jon Ogborn
Keyword(s):  
Yield Strength ◽  
Weld Metal ◽  
Base Material ◽  
Dynamic Strain ◽  
Pipe Material ◽  
Cored Wire ◽  
Line Pipe ◽  
Strain Ageing ◽  
Girth Welds ◽  
Welding Processes

Pipeline girth welds for on-shore and off-shore pipelines use a variety of arc welding processes. The trend towards strain based designs for line pipe installation and the effect of coatings for off-shore pipelines have resulted in evaluation and testing of pipe material subjected to strain ageing. However, very little work has been done to systematically study the effect on ferritic weld metal. This work details some initial work done on evaluating the effect of strain ageing on ferritic weld metal deposited with a 1.2 mm diameter flux cored wire under 75% Ar −25% CO2 shielding gas. Pipeline girth welds were welded on API Grade X-70 pipe and tested to get all weld metal tensile and Charpy V-Notch properties. The weld metal strength overmatched the base material by 7–9%. The ductile to brittle transition temperature for the weld metal was −40°C. The effect of strain ageing on weld metal properties was evaluated. All weld metal tensile samples were subjected to varying levels of pre-strain and ageing treatments to evaluate the effect on yield strength and post-yield behavior. An increase in yield strength after straining and ageing as well as the re-appearance of yield point is observed. Increase in pre-strain decreases elongation. Increase in ageing temperature delays the appearance of dynamic strain ageing. The activation energy for the increase in strength after strain ageing has been measured by assuming a diffusion controlled mechanism. Charpy V-Notch samples were taken to generate transition curves of weld metal after strain ageing and compared to the as-welded condition.

Structure and Properties of X80 and X100 Pipeline Girth Welds

2004 ◽  
Author(s):  
J. A. Gianetto ◽  
J. T. Bowker ◽  
D. V. Dorling ◽  
D. Horsley
Keyword(s):  
Yield Strength ◽  
Weld Metal ◽  
Tensile Properties ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Narrow Gap ◽  
Line Pipe ◽  
Metal Arc Welding ◽  
Girth Welds ◽  
Strength And Toughness

This study aims to provide an understanding of the factors that control weld metal strength and toughness of mechanized field girth welds produced in X80 and X100 line pipe steels using a range of pipeline gas metal arc welding procedures. In the investigation of X80 welds, a series of experimental single and dual torch gas metal arc welds were prepared with three C-Mn-Si wires, which contained additions of Ti, Ni-Ti and Ni-Mo-Ti. The weld metal microstructures, tensile properties, notch toughness, and fracture resistance were evaluated. The results indicate that high weld metal yield strength and good toughness can be achieved. The X80 single torch welds exhibited higher yield strength but lower toughness compared to the corresponding dual torch welds. For the development and evaluation of welding procedures for mainline girth welding of X100 pipe, two narrow gap mechanized gas metal arc welding procedures were evaluated with emphasis placed on measurement of the tensile properties. The results show that dramatically different properties (strength and toughness) can be found as a result of differences in energy input, interpass temperature and weld width or offset distance. Additionally, the preliminary tensile testing, which utilized both standard round bar and modified strip tensile specimens, illustrates the potential variation that can occur when assessing all-weld-metal tensile properties of narrow gap pipeline girth welds.

Detection and In-Field Verification of Potential Pipeline Expansion Due to Low Yield Strength Pipe in High Strength Line Pipe

2010 ◽  
Author(s):  
Jill Braun ◽  
Stuart Clouston
Keyword(s):  
High Resolution ◽  
Yield Strength ◽  
Measurement Errors ◽  
High Strength ◽  
Lessons Learned ◽  
Chemical Compositions ◽  
Line Pipe ◽  
Variable Yield ◽  
Field Verification ◽  
Pipe Joints

On May 21, 2009, the Pipeline & Hazardous Materials Safety Administration (PHMSA) issued an Advisory Bulletin (PHMSA-2009-0148) entitled, “Potential for Low and Variable Yield, Tensile Strength and Chemical Compositions in High Strength Line Pipe” [1] recommending that pipeline operators investigate whether recently constructed pipelines contain pipe joints not meeting the minimum specification requirements (74FR2390). Based on PHMSA’s technical reviews, high resolution deformation tool inspection combined with comprehensive infield verification has been recommended in accordance with the “Interim Guidelines for Confirming Pipe Strength in Pipe Susceptible to Low Yield Strength,” issued by PHMSA in September 2009[2]. Kern River Gas Transmission Company (Kern River) underwent a detailed program of engineering and assessment in order to proactively demonstrate compliance with the interim guidelines. This paper discusses the process, inspection results and infield verifications performed by the pipeline operator. In particular, detailed consideration to the methodology of detection and assessment of potential pipeline expansions is presented with discussion on the special considerations needed for low level anomaly identification, reporting and verification of expansions as defined in the PHMSA guidelines. High resolution caliper analysis approaches developed for this particular application are discussed and appropriate techniques are recommended that consider the effects of possible asymmetry of expansions and impact of other deformations such as ovality. Field verification practices and findings are reviewed in detail with particular focus on the challenges facing the pipeline operator in resolving both tool and in-field measurement errors that can significantly impact the number of identifiable candidate expansions for verification. In conclusion, an overview of the assessment criteria and field activity to comply with the PHMSA interim guidelines are presented along with the lessons learned from the analysis, verification and remediation steps that may assist other pipeline operators as they address these newly established regulatory requirements.

Evaluation of Hydrogen Cracking Susceptibility in X120 Girth Welds

2004 ◽  
Author(s):  
M. L. Macia ◽  
D. P. Fairchild ◽  
J. Y. Koo ◽  
N. V. Bangaru
Keyword(s):  
Laboratory Tests ◽  
High Strength ◽  
Test Method ◽  
Laboratory Studies ◽  
Long Distance ◽  
Hydrogen Cracking ◽  
Girth Welding ◽  
Groove Test ◽  
Girth Welds ◽  
The Cost

To reduce the cost of long distance gas transmission, high strength pipeline steels are being developed. Implementation of high strength pipeline materials requires the avoidance of hydrogen cracking during field girth welding. A study of hydrogen cracking in X120 girth welds has been conducted. Cracking resistance of both the weld metal and heat affected zone (HAZ) were investigated. The laboratory tests included the controlled thermal severity (CTS) test, the WIC test and the Y-groove test. In addition, multi-pass plate welds and full pipe welds were completed and examined for the presence of hydrogen cracks. The suitability of each test method for predicting cracking in X120 girth welds is determined. The morphology of hydrogen cracks in X120 girth welds is described, and the conditions necessary to prevent hydrogen cracking are identified. Following the laboratory studies, construction of X120 pipelines without cracking was demonstrated through a 1.6 km field trial.

Weld Metal Hydrogen Cracking in Transmission Pipelines Construction

2010 ◽  
Author(s):  
Sheida Sarrafan ◽  
Farshid Malek Ghaini ◽  
Esmaeel Rahimi
Keyword(s):  
Weld Metal ◽  
Construction Projects ◽  
High Strength Steels ◽  
High Strength ◽  
Carbon Equivalent ◽  
Transverse Cracks ◽  
Diffusible Hydrogen ◽  
Hydrogen Cracking ◽  
Girth Welds ◽  
Welding Position

Developments of high strength steels for natural gas pipelines have been in the forefront of steelmaking and rolling technology in the past decades. However, parallel to such developments in steel industry, the welding technology especially with regards to SMAW process which is still widely used in many projects has not evolved accordingly. Decreasing carbon equivalent has shifted the tendency of hydrogen cracking from the HAZ to the weld metal. Hydrogen cracking due to its complex mechanism is affected by a range of interactive parameters. Experience and data gained from field welding of pipeline construction projects indicated that weld metal hydrogen cracking is related to welding position as it occurs more in the 6 o’clock position of pipeline girth welds. In this research an attempt is made to open up the above observation in order to investigate the contributory factors such as welding position and welding progression in terms of diffusible hydrogen and possibly residual stress considerations. It was observed that transverse cracks produced in laboratory condition may not be detected by radiography. But, the higher tendency for cracking at 6 o’clock position was confirmed through bend test. It is shown that more hydrogen can be absorbed by the weld metal in the overhead position. It is shown that welding progression may also have a significant effect on cracking susceptibility and it is proposed that to be due to the way that weld residual stresses are developed. The observations can have an important impact on planning for welding procedure approval regarding prevention of transverse cracking in pipeline girth welds.

Methodology for Assessment of Surface Defects in Undermatched Pipeline Girth Welds

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
Aurélien Pépin ◽  
Tomasz Tkaczyk ◽  
Noel O'Dowd ◽  
Kamran Nikbin
Keyword(s):  
Weld Metal ◽  
Surface Defects ◽  
Analytical Formula ◽  
Strain Curve ◽  
High Strength ◽  
Cost Effective ◽  
Medium Size ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Girth Welds

The demand for subsea transport of highly corrosive constituents has noticeably increased in recent years. This has driven the requirement for high strength pipelines with enhanced corrosion resistance such as chromium stainless steel or bimetal pipes. The latter are carbon steel pipes with a corrosion resistant alloy lining. Reeling is a cost effective installation method for small to medium size subsea pipelines, up to 457.2 mm (18 in.) in diameter. However, plastic straining associated with reeling has an effect on weld defect acceptance criteria. The maximum acceptable defect sizes are typically developed using engineering critical assessment (ECA), based on the reference stress method, which requires that the weld metal is equal to or stronger than the parent metal in terms of the stress–strain curve. However, evenmatch/overmatch cannot always be achieved in the case of subsea stainless or bimetal pipelines. In this work, a parametric finite-element (FE) study was performed to assess the effect of weld metal undermatch on the crack driving force, expressed in terms of the crack tip opening displacement (CTOD). Subsequently, the fracture assessment methodology for reeled pipes was proposed, where the ECA as per BS7910 is first carried out. These acceptable defect sizes are then reduced, using an analytical formula developed in this work, to account for weld undermatch.

Welding of High Strength Pipelines

2004 ◽  
Author(s):  
Bill Bruce ◽  
Jose Ramirez ◽  
Matt Johnson ◽  
Robin Gordon
Keyword(s):  
Weld Metal ◽  
Charpy Impact ◽  
High Strength ◽  
Shielding Gas ◽  
Hydrogen Cracking ◽  
Mechanized Welding ◽  
Margin Of Safety ◽  
Girth Welds ◽  
Welding Consumables

This paper presents the results of a project jointly funded by PRCI and EWI to evaluate the welding of X100 pipe grades using commercially available welding consumables. The welding trials included manual, semi-automatic and mechanized welding procedures. It was found that the combination of Pulsed GMAW and ER100S-1 (using a mixed shielding gas) produced both excellent Charpy impact and CTOD performance, but could result in undermatched girth welds if the pipe significantly exceeds minimum strength requirements. Although ER120 S-1 provides an additional margin of safety in strength, which should accommodate variations in X-100 pipe properties, the toughness results were marginal at −10°C. The risk of weld metal hydrogen cracking in X100 girth welds was also investigated.

Effects of a Thermal Coating Process on X100 UOE Line Pipe

2005 ◽  
Author(s):  
Chris Timms ◽  
Duane DeGeer ◽  
Martin McLamb
Keyword(s):  
Heat Treatment ◽  
Yield Strength ◽  
Room Temperature ◽  
High Strength ◽  
Economic Benefits ◽  
Slight Reduction ◽  
Strength Increase ◽  
Coating Process ◽  
Line Pipe ◽  
Heat Treated

The increased demand for high strength linepipe for onshore and offshore pipeline systems has been well documented over the past few years. The economic benefits have been demonstrated, and solutions have been developed to address the technical issues facing high strength linepipe use. However, there are still a few unanswered questions, one of which is addressed in this paper: what is the effect of thermal treatment during the pipeline coating process on the material behaviour of high strength linepipe? This paper presents the results of a thermal coupon study investigating the effects of low temperature heat treatment on the tensile and compressive stress strain curves of samples taken from X100 linepipe. Thirty axial test coupons and thirty circumferential test coupons were machined from a 52 inch diameter, 21 mm wall thickness UOE X100 linepipe. Some of the coupons were maintained in the as-received condition (no heat treatment) while others were heat-treated in a manner that simulates a coating plant induction heat treatment process. All coupons were subsequently tested in tension or compression, either at room temperature or at −18°C. This study has provided a number of interesting results. In regards to material strength, the heat treatment increased the tensile and compressive yield strengths in the longitudinal and circumferential coupons. Axial tensile, axial compressive and circumferential tensile yield strength increases ranged from 5 to 10%. Circumferential compressive yield strength increases ranged from 14 to 24%. A Y/T ratio increase of approximately 7% was observed for all heat-treated tensile coupons. The coupon tests conducted at −18°C were only slightly different than their room temperature counterparts; with an average yield strength increase of 4% in all directions and orientations and a slight reduction in Y/T ratio.

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