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.

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.

Development of a Multi-Pass Weld Transverse Cracking Test

2008 ◽  
Author(s):  
L. N. Pussegoda ◽  
D. Begg ◽  
R. Lazor
Keyword(s):  
Large Diameter ◽  
High Strength Steels ◽  
High Strength ◽  
Test Methods ◽  
Primary Objective ◽  
Test Method ◽  
Thick Wall ◽  
Transverse Cracks ◽  
Delayed Cracking ◽  
Girth Welds

Transverse weld metal cracking has been occasionally observed in girth welds on large diameter thick wall pipelines that utilize high strength steels. The cracks are typically in the last one or two layers of the weld, and are not necessarily surface-breaking cracks. These cracks are a serious concern as they are parallel to the pipe axis, an orientation that is perpendicular to the hoop stress due to pipeline operation. Weldability tests have been developed or modified in recent years that were intended to specifically examine the tendency for cracking in multipass welds. Test methods are somewhat similar in that a multilayer full-thickness weld is deposited in a restrained (or self-restrained) weld joint, followed by examination to determine the occurrence of cracking after a specified delay period. The primary objective of this study has been to develop a test method that can then be used to compare the incidence of cracking to hydrogen-induced cracking prediction methods (for example delay time), also allowing one to develop welding conditions that would avoid cracking of field welds during pipeline construction. This could be achieved in two ways; a) determining delayed cracking time, and b) assessing the effects of pre-heat and interpass temperature. The test has been successful in producing transverse cracks in the top layers of the fill passes, similar to the cracking that has been observed on thick weldments in high strength steels. The test has been instrumented to assess the restraint level and also to attempt to detect cracking. The cracking has also been detected by UT and subsequent sectioning.

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.

Microstructure and Properties of High Strength Steel Weld Metals

2012 ◽  
Author(s):  
J. A. Gianetto ◽  
G. R. Goodall ◽  
W. R. Tyson ◽  
F. Fazeli ◽  
M. A. Quintana ◽  
...  
Keyword(s):  
Weld Metal ◽  
Gas Metal Arc Welding ◽  
Large Diameter ◽  
High Strength Steels ◽  
High Strength ◽  
High Productivity ◽  
Metal Arc Welding ◽  
Wide Range ◽  
Girth Welds ◽  
Welding Processes

With an industry trend towards application of modern high strength steels for construction of large diameter, high pressure pipelines from remote northern regions there is a need to develop high-productivity welding processes to reduce costs and deal with short construction seasons. Achieving the required level of weld metal overmatching together with adequate ductility and good low temperature toughness is another major challenge for joining high strength X80/100 pipes. It is important to develop an improved understanding of weld metal systems that are required for the successful production of high strength pipeline girth welds that are needed for such demanding pipeline construction. In this investigation a range of weld metal (WM) compositions based on (i) C-Mn-Si-Mo, (ii) C-Mn-Si-Ni-Mo-Ti and (iii) C-Mn-Si-Ni-Cr-Mo-Ti was selected for more detailed evaluation of experimental plate welds complemented by specimens simulated by Gleeble® thermal cycling. Five specially-designed experimental plate welds were made with a robotic single torch pulsed gas metal arc welding (GMAW-P) procedures with wire electrodes applicable for joining X100 pipe. The procedures consisted of three initial fill passes deposited at 0.5 kJ/mm and a final deep-fill pass at 1.5 kJ/mm to just fill the narrow-gap joint. An important part of the research focused on development of WM Continuous Cooling Transformation (CCT) diagrams to establish the influence of composition and thermal cycle (cooling time) on formation of fine-scale, predominantly martensite, bainite and acicular ferrite (AF) microstructures. For the relatively wide range of cooling times investigated (Δt800−500 = 2 to 50 s), the lowest-alloyed WM (LA90) exhibited microstructures dominated by bainite with martensite to AF, whereas the highest-alloyed WM (PT02) formed large fractions of martensite with bainite to AF. Weld metal toughness was evaluated using both through-thickness notched 2/3 sub-size Charpy-V-notch (CVN) specimens as well as full-size surface-notched specimens. Post-test metallographic and fractographic examinations of selected fractured specimens were used to correlate WM microstructure and notch toughness.

Development of High Steel Grade Seamless X100 Weldable

2008 ◽  
Author(s):  
Alfonso Izquierdo ◽  
Hector Quintanilla ◽  
Gilles Richard ◽  
Ettore Anelli ◽  
Gianluca Mannucci ◽  
...  
Keyword(s):  
Phase I ◽  
Phase Ii ◽  
Limit State ◽  
High Strength Steels ◽  
High Strength ◽  
Steel Grade ◽  
Technological Evolution ◽  
Complex Design ◽  
Exploration And Production ◽  
Girth Welds

The technological evolution in the offshore sector points out a trend towards an increasing use of high strength steels (grade 80ksi and higher), for both pipelines and risers. Pipeline specifications for deepwater offshore fields demand developments in design criteria (i.e. limit state design), welding, installation, and laying technologies. As long as the market goes deeper in offshore exploration and production, the market trend is to use heavier pipes in steel grade X65/X70 and some technological limits from several fronts are faced and more attractive becomes for the market to have a lighter high strength 100ksi seamless steel grade. The joint industrial program (JIP), termed “Seamless 100 ksi weldable” launched by Tenaris in order to address the complex design issues of high strength Q&T seamless pipes for ultra deep water applications has been finalized. The 100ksi steel grade has been achieved in two wall thickness 16 mm and 25 mm. The main results from both phase I devoted to the development and production of seamless pipes with minimum 100ksi and phase II devoted to evaluate the high strength seamless pipe weldability will be addressed in this paper. Main microstructural features promoting the best strength-toughness results obtained from phase I and the results from phase II, where the heat affected zone (HAZ) characterization made using stringent qualifying configuration such as API RP2Z and the promising results after qualifying the girth welds simulating a typical offshore operation and the Engineering Critical Assessment for installation will be addressed. The results from this development are of interest of all oil & gas companies who are facing as an output from the design project analysis the need to have high strength seamless pipes.

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.

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.

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.

Prediction of Post Weld Hardness of Advanced High Strength Steels for Automotive Application using a Dedicated Carbon Equivalent Number

2008 ◽  
Vol 52 (11-12) ◽  
pp. 18-29 ◽  
Author(s):  
N. J. den Uijl ◽  
H. Nishibata ◽  
S. Smith ◽  
T. Okada ◽  
T. van der Veldt ◽  
...  
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Automotive Application ◽  
Carbon Equivalent ◽  
Advanced High Strength Steels ◽  
Equivalent Number
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