CTOA Measurements of Welds in X100 Pipeline Steel

2008 ◽  
Author(s):  
Elizabeth Drexler ◽  
Philippe Darcis ◽  
Christopher McCowan ◽  
J. Matthew Treinen ◽  
Avigdor Shtechman ◽  
...  
Keyword(s):  
Stress Field ◽  
Base Metal ◽  
Pipeline Steel ◽  
Base Material ◽  
Fusion Line ◽  
Opening Angle ◽  
Seam Weld ◽  
Weld Material ◽  
X100 Pipeline Steel ◽  
Girth Welds

A suite of tests characterizing X100 pipeline steels was initiated at the National Institute of Standards and Technology (NIST) in Boulder. Part of the test matrix included testing the toughness of the base metal, welds, and heat-affected zones (HAZ) by use of modified double cantilever beam specimens for crack tip opening angle (CTOA) testing. The thickness of the test section was either 3 mm or 8 mm. Girth welds perpendicular to the growing crack, and seam welds and their HAZ parallel with the crack, were tested with a crosshead displacement rate of 0.02 mm/s (with the exception of one girth weld specimen for each thickness, which were tested at 0.002 mm/s). Analysis of the data revealed some general differences among the weld specimens. The tests where the crack ran perpendicular to the girth weld demonstrated changes in CTOA and crack growth rate as the crack moved through the base metal, HAZ, and weld material. We observed the values for CTOA increasing and the crack propagation slowing as the crack moved through the weld and approached the fusion line. The stress field appeared to be strongly influenced by the thin HAZ, the fusion line, and the tougher base material. Consequently, the CTOA of the HAZ associated with the girth weld was larger than that of the seam-weld HAZ. It was not possible to obtain CTOA data for the seam weld, with the crack parallel within the weld, because the crack immediately diverted out of the stronger weld material into the weaker HAZ. CTOA values from both girth welds and seam-weld HAZ were smaller than those of the base material. The 8 mm thick specimens consistently produced larger CTOA values than their 3 mm counterparts, introducing the possibility that there may be limitations to CTOA as a material property. Further tests are needed to determine whether a threshold thickness exists below which the constraints and stress field are sufficiently changed to affect the CTOA value.

Crack Formation in Charpy Tests of the Heat-Affected Zone of Large-Diameter Linepipe Material

2018 ◽  
Author(s):  
Lars Schemmann ◽  
Charles Stallybrass ◽  
Jens Schröder ◽  
Andreas Liessem ◽  
Stefan Zaefferer
Keyword(s):  
Base Metal ◽  
Heat Affected Zone ◽  
Volume Fraction ◽  
Large Diameter ◽  
Base Material ◽  
Fusion Line ◽  
3D Analysis ◽  
Pipe Material ◽  
Austenite Grain Size ◽  
Secondary Cracks

Double submerged arc welding is an efficient process used during the production of longitudinally-welded large-diameter pipes. It is well known that the associated high heat input has a negative influence on the toughness of the heat-affected zone (HAZ). The toughness drop is related to changes in the HAZ microstructure compared to the base metal. The austenite grain size increases significantly and larger carbon-rich martensite/austenite particles (M/A-particles) are formed within a coarse bainitic matrix during the phase transformation compared to the as-rolled base material. The exact relationship between the microstructure, the processing conditions, base metal composition and the weld metal are at the focus of attention of materials development efforts at EUROPIPE and Salzgitter Mannesmann Forschung GmbH (SZMF). In the present study, scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) were used to investigate the HAZ of X70 large-diameter pipe material as well as tested Charpy specimens from the same material. Secondary cracks in the direct vicinity of the primary fracture surface of tested Charpy specimens from the HAZ were analyzed by EBSD and SEM to investigate the damage mechanism in detail. It was found that these cracks originate at M/A-particles and that the dominant crack path depends on the crystallographic orientation of the surrounding matrix. The analysis of several EBSD measurements and a 3D-analysis of the propagation direction of the crack showed that secondary cracks frequently propagate parallel to {100} and rarely along {110}-planes. It is known from literature that these are preferred cleavage planes in ferritic steels. The SEM analysis performed in the HAZ of the investigated steel showed that the volume fraction of elongated M/A-particles is elevated close to the fusion line and decreases within the first few hundred micrometers distance from the fusion line. The EBSD measurements illustrate that the geometrically necessary dislocation density is significantly increased in the neighborhood of M/A-particles. This indicates that the bainitic matrix is work-hardened around the M/A-particles during testing and is therefore more prone to the formation of microcracks than other surrounding regions.

scholarly journals STRENGTH AND FRACTURE TOUGHNESS OF THE WELDED JOINTS MADE OF HIGH-STRENGTH FERRITIC STEEL

2013 ◽  
Vol 7 (4) ◽  
pp. 226-229 ◽  
Author(s):  
Ihor Dzioba ◽  
Tadeusz Pała ◽  
Ilkka Valkonen
Keyword(s):  
Fracture Toughness ◽  
Heat Affected Zone ◽  
Welded Joints ◽  
Ferritic Steel ◽  
Base Material ◽  
High Strength ◽  
Experimental Results ◽  
Strength Characteristics ◽  
Fusion Line ◽  
Weld Material

Abstract The paper presents experimental results of the characteristics of strength and fracture toughness of the material from the different zones of welded joints made of different participation of the linear welding energy. Strength characteristics and fracture toughness were determined in the weld material, in the area of fusion line, in the material of the heat affected zone and in the base material

Numerical Simulation of Residual Stresses Due to Cladding Process

2007 ◽  
Author(s):  
Dieter Siegele ◽  
Marcus Brand
Keyword(s):  
Numerical Simulation ◽  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Residual Stresses ◽  
Base Metal ◽  
Base Material ◽  
Pressure Vessels ◽  
Measured Temperature ◽  
Residual Stress Field

The inner surface of reactor pressure vessels is protected against corrosion by an austenitic cladding. Generally, the cladding is welded on the ferritic base metal with two layers to avoid sub-clad cracks and to improve the microstructure of the cladding material. On the other hand, due to the cladding process and the difference of the thermal expansion coefficient of the austenitic cladding and the ferritic base material residual stresses act in the component. This residual stress field is important for assessing crack postulates in the cladding or subclad flaws in the base metal. For the determination of the residual stress field, plates of RPV steel were cladded and heat treated representative to the RPV relevant conditions. During the cladding process the temperature and distortion were measured as basis for the validation of the finite element simulations. The numerical simulation was performed with the finite element code SYSWELD. The heat source of the model was calibrated on the measured temperature profile. In the analysis, the temperature dependent material properties as well as the transformation behavior of the ferritic base metal were taken into account. The calculated residual stresses show tensile stresses in the cladding followed by compressive stresses in the base metal that are in agreement with measurements with X-ray diffraction technique.

Evaluating Mechanical Properties of Hybrid Laser Arc Girth Welds

2010 ◽  
Author(s):  
L. N. Pussegoda ◽  
D. Begg ◽  
R. Holdstock ◽  
A. Jodoin ◽  
K. Light ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Pipeline Steel ◽  
Standard Test ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Fracture Transition ◽  
X100 Pipeline Steel ◽  
Girth Welds ◽  
Inspection Data ◽  
Crack Tip Opening

This paper presents the challenges and results associated with mechanical testing of overmatched X80 and X100 pipeline steel girth welds that were produced by Hybrid Laser Arc Welding (HLAW). The weld profile produced by this process is characterized as having a broad weld cap and a narrow leg, which traverses the through thickness direction. The development and testing of the HLAW process was conducted on NPS36 pipes of 10.4 mm and 14.3 mm thickness, respectively. The welds were deposited in the 5G welding position with all parameters and laser visual inspection data being collected for each weld pass. Subsequent sample extraction and testing of the hybrid laser arc welds were achieved by standard test practices for girth welds and modifications of these practices, where the latter was required to facilitate testing of the narrow HLAW geometry. Charpy results indicate that the fracture transition temperature, with the notch in either the weld metal or the heat-affected zone (HAZ), is higher at the 3 and 9 o’clock positions when compared to 9 and 12 o’clock positions. The likelihood of crack deviation influencing the results due to the non-conventional weld geometry needs to be examined in a further study. For crack tip opening displacement (CTOD) testing, shorter fatigue crack lengths were employed to reduce the possibility of fatigue crack deviation. The results show that this method does not influence the validity of the test outcomes.

Morphology and Distribution of M7C3 and TiC In Situ Synthesized in Plasma Surfacing

2012 ◽  
Vol 557-559 ◽  
pp. 1752-1755
Author(s):  
Yun Hai Su ◽  
De Guang Wu ◽  
Guang Chao Liu
Keyword(s):  
Base Metal ◽  
Low Carbon Steel ◽  
Base Material ◽  
Fusion Line ◽  
Large Temperature ◽  
Bonding Layer ◽  
Plasma Arc ◽  
Low Carbon ◽  
Metallurgical Bonding

In order to systematically study the morphology and distribution of M7C3 and TiC which in situ synthesized by plasma arc in the surfacing layer, plasma arc was used to clad the Fe-Cr-Ti-C wear-resistant alloy on low-carbon steel. And high corrosion experiment was applied to the surfacing layer. The hardness, microstructure and phase constitution of the surfacing layer were investigated through the tests of hardness, OM, EDS, SEM and XRD analysis. The results shows that irregular hexagonal (Cross-section) and strip (Side) M7C3 and petal-like, granular TiC were in situ synthesized in the surfacing layer. The M7C3 and TiC was combined closely. The M7C3 grains which closed to the fusion line of the base metal and surfacing layer are fine, but the ones that away from the fusion line are larger caused by the large temperature gradient. Smooth metallurgical bonding layer was formed between the surfacing layer and the base metal, it has a good metallurgical bonding. The phenomenon that carbon diffusion into the base material was clearly, the hardness near the fusion zone was improved effectively.

The Development of Large Diameter and Thickness X80 HSAW Linepipe

2008 ◽  
Author(s):  
Weiwei Li ◽  
Chunyong Huo ◽  
Qiurong Ma ◽  
Yaorong Feng
Keyword(s):  
Bauschinger Effect ◽  
Pipeline Steel ◽  
Large Diameter ◽  
Base Material ◽  
Longitudinal Direction ◽  
Strength Loss ◽  
Ring Test ◽  
Low Carbon ◽  
Pipeline Project ◽  
Submerged Arc

For the requirement of 2nd West-East Pipeline Project of China, X80 large diameter & thickness linepipe with helical seam submerged arc welded (HSAW) were developed, with 1219 mm OD and 18.4 mm WT. Acicular ferrite type and super-low carbon, high Niobium chemical composition pipeline steel was adopted for the base material. The very stringent requirements at −10 °C for toughness, i.e. 220J/170J for average/minimum for pipe body and 80J/60J for average/minimum for weld and HAZ were meet successfully. The yield strength loss due to Bauschinger effect was found lower than 20MPa, which benefited. The very low residual stress level was testified by cut-ring test which cuts a section pipe about exceed 100mm long, and then cut the section apart from welds 100mm along the longitudinal direction.

scholarly journals The Pitting Susceptibility Investigation of Passive Films Formed on X70, X80, and X100 Pipeline Steels by Electrochemical Noise and Mott-Schottky Measurements

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Yang Zhao ◽  
Ping Liang ◽  
Yanhua Shi ◽  
Yunxia Zhang ◽  
Tao Yang
Keyword(s):  
Distribution Function ◽  
Electrochemical Noise ◽  
Pipeline Steel ◽  
Stochastic Theory ◽  
Gumbel Distribution ◽  
Passive Films ◽  
Initiation Rate ◽  
Pipeline Steels ◽  
X100 Pipeline Steel ◽  
Pit Initiation

The pitting susceptibility of passive films formed on X70, X80, and X100 pipeline steels was investigated by means of electrochemical noise (EN) and Mott-Schottky measurements. The EN results were analyzed according to the shot-noise theory and stochastic theory. Pit initiation process was analyzed quantitatively using the Weibull distribution function. Pit growth process was simulated by Gumbel distribution function. The experimental results of Mott-Schottky plots showed that the passive films formed on the three pipeline steels displayed an n-type semiconductor character, and the passive film for X100 pipeline steel has the lowest donor density (ND) among the three passive films. The EN results demonstrated that X100 pipeline steel had the lowest pit initiation rate and pit growth probability, which implied that the X100 pipeline steel had the lowest pitting susceptibility.

scholarly journals Experimental Research on Fatigue Properties of X80 Pipeline Steel for Synthetic Natural Gas Transmission

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Li Yan–hua ◽  
Feng Hui ◽  
Chi Qiang ◽  
Fei Fan ◽  
Gao Xiong-xiong ◽  
...  
Keyword(s):  
Natural Gas ◽  
Base Metal ◽  
Hydrogen Content ◽  
Volume Fraction ◽  
Pipeline Steel ◽  
Fatigue Properties ◽  
High Grade ◽  
Long Distance ◽  
X80 Pipeline Steel ◽  
Synthetic Natural Gas

In recent years, many synthetic natural gas demonstration projects have been put into operation all over the world, and hydrogen is usually contained in synthetic natural gas. X80 is the most commonly used high-grade pipeline steel in the construction of natural gas pipelines. The compatibility between high-grade pipeline steel and hydrogen directly affects safety and reliability of long-distance pipelines. Therefore, in order to study the effect of hydrogen content on fatigue properties of high-grade pipeline steel, fatigue specimens were taken from base metal, spiral welds, and girth weld of submerged arc spiral welded pipes, respectively. Specifically, the total pressure was 12 MPa and hydrogen content was from 0 to 5vol%. Experimental results indicate that the hydrogen significantly increases the fatigue crack growth rate for both base metal, spiral weld, and heat-affected zone of X80 pipeline steel for about ten times compared with reference environment nitrogen, hydrogen would greatly reduce the fatigue life of the X80 pipeline steel, and the fatigue lifetime would decrease with the increase in hydrogen volume fraction. In order to ensure the safe operation of SNG pipeline, the hydrogen content should be controlled as low as possible.

Development of Selective Seam Weld Corrosion Test Method

2014 ◽  
Author(s):  
J. A. Beavers ◽  
C. S. Brossia ◽  
R. A. Denzine
Keyword(s):  
Base Metal ◽  
Field Testing ◽  
Test Method ◽  
Transportation Safety ◽  
Seam Weld ◽  
Corrosion Kinetics ◽  
Pipeline Failures ◽  
Weld Corrosion ◽  
Pipeline Safety ◽  
Non Destructive

Selective seam weld corrosion (SSWC) of electric resistance welded (ERW) pipelines has been identified as a potential risk to pipeline safety. Due to recent pipeline failures, where seam weld defects may have played a significant role, the National Transportation Safety Board called upon the Pipeline and Hazardous Materials Safety Administration (PHMSA) to conduct a comprehensive study to identify actions that can be used by operators to eliminate catastrophic longitudinal seam failures in pipelines. Battelle contracted Kiefner and Associates, Inc. and Det Norse Veritas (U.S.A.) Inc. (DNV GL) with the objective to assist PHMSA in addressing this issue. The objective of one of the tasks performed by DNV GL was to develop a reliable, rapid, non-destructive, field-deployable test method that can quantify SSWC susceptibility on operating pipelines containing ERW seams. For this effort, two different, field deployable, non-destructive methods were evaluated in laboratory testing. The methods were validated using a standard destructive test for assessing SSWC susceptibility. One method was based on measurement of the local potential difference between the seam weld and the adjacent base metal while the second was based on differences in the corrosion kinetics between the seam weld and the base metal. The method that is based on corrosion kinetics was found to be most effective in identifying SSWC susceptible pipe steels. It utilizes a barnacle cell to conduct linear polarization resistance measurements on small, selected areas of the pipe (e.g., the weldment or base metal). Additional laboratory as well as field-testing is planned to further validate the test method.

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