Influence of Steel Chemistry and Field Girth Welding Procedure on Performance of Api X70 Pipelines

Abstract Owing to recent concerns regarding pipeline field girth weld performance, particularly heat affected zone (HAZ) softening and toughness, EVRAZ North America has initiated a research program to evaluate the response of API grade line pipe to the current field girth welding practices. In particular, this study aims to elucidate the role of steel alloy design as well as the welding procedure on field girth weld and HAZ properties. This understanding is critical to balance the detrimental effects of HAZ softening on the overall joint strength against factors affecting HAZ toughness. A selection of several different steels with different levels of alloying elements, Ceq and Pcm have been subjected to welding trials to assess the effects of chemistry on joint performance. Furthermore, an analysis on the effect of welding process parameters on the joint properties has been made. The welds, fabricated via a manual shielded metal arc welding (M-SMAW) process, were evaluated in terms of toughness, local vs global strain distribution during tensile testing using digital image correlation (DIC) technique, and hardness contour mapping of the weld and HAZ regions. The results explicitly show that the extent of HAZ softening decreased as the amount of Mo, Mn, Ti/N and Ceq increased. However, this alloying addition resulted in a detrimental effect on the HAZ toughness, particularly towards the cap and fill passes. The HAZ softening increased as the inter-pass temperature and the welding heat input increased. In addition, the strain analysis confirmed the weld passes towards the root/hot passes are more prone to HAZ softening compared with the upper cap and fill passes.

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Analysis of Welding Technology about Bimetallic Clad Pipelines

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.905.9 ◽

2022 ◽

Vol 905 ◽

pp. 9-13

Author(s):

Fu Shan Wang ◽

Fa Gen Li ◽

Ya Jun Li ◽

Xue Qiang Mao ◽

Bai Chun Liu ◽

...

Keyword(s):

Welding Process ◽

Paper Analysis ◽

Future Application ◽

Test Results ◽

Welding Material ◽

Girth Welding ◽

Corrosion Resistant Alloy ◽

Welding Procedure ◽

Welding Processes ◽

Welding Materials

Butt girth welding was a knotty problem for future application of bimetallic clad pipelines. At present, there were two kinds of problems: 1) To decide whether to use a variety of alloy welding procedure or to use corrosion resistant alloy full welding procedure; 2) After selecting the procedure, what kind of welding material should be equipped. In view of the above problems, taking 316L SS or 2205 DSS clad pipe as an example, welding process design and experimental analysis were conduted in this paper. Analysis of welding process from theory, standard and practice pointed out the control of welding hardness under different welding materials and procedure and directional suggestions of welding for bimetallic clad pipelines were provided. Futher the hardness distribution and CVN absorbed Energy test results of different welding processes showed welding quality could be guaranteed only when ENiCrMo-3 welding material was chosen for the whole weld.

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Attributes of Modern Linepipes and Their Implications on Girth Weld Strain Capacity

Volume 3: Operations, Monitoring, and Maintenance; Materials and Joining ◽

10.1115/ipc2018-78809 ◽

2018 ◽

Author(s):

Yong-Yi Wang ◽

Steve Rapp ◽

David Horsley ◽

David Warman ◽

Jim Gianetto

Keyword(s):

Tensile Properties ◽

Weld Strength ◽

Potential Contribution ◽

Contributing Factors ◽

Strain Capacity ◽

Strain Tolerance ◽

Industry Standards ◽

Girth Welding ◽

Girth Welds ◽

Welding Procedure

There has been a number of unexpected girth weld failures in newly constructed pipelines. Girth weld failures have also been observed in pre-service hydrostatic testing. Post-incident investigations indicated that the pipes met the requirements of industry standards, such as API 5L. The welds were qualified per accepted industry standards, such as API 1104. The field girth welding was performed, inspected, and accepted per industry standards, such as API 1104. Some of the traditional causes of girth weld failures, such as hydrogen cracks and high-low misalignment, were not a factor in these incidents. This paper starts with a review of the recent girth weld incidents. A few key features of a failed weld and their implications are examined. The characteristics of the recent failures is summarized, and the major contributing factors known to date are given. Some of the options to prevent future failures include (1) changes to the tensile properties of the pipes and enhanced hardenability, (2) welding options aimed at increasing the weld strength and minimizing heat-affected zone (HAZ) softening, and (3) reduction of stresses on girth welds. This paper focuses on the first two options. The trends of chemical composition and tensile properties of linepipe are reviewed. The potential contribution of these trends to the girth weld incidents is examined. Possible changes to the linepipe properties and necessary updates in the testing and qualification requirements of the linepipes are provided. Welding options beneficial to enhanced girth weld strain capacity are discussed. Possible revisions to welding procedure qualification requirements, aimed at achieving a minimum level of strain tolerance/capacity, are proposed. The application of previously developed tools in estimating the propensity of HAZ softening is reviewed.

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Pipe Bending Test With Girth Welding on X80 Grade SAW Pipes

2010 8th International Pipeline Conference, Volume 4 ◽

10.1115/ipc2010-31433 ◽

2010 ◽

Author(s):

Masahiko Hamada ◽

Hidenori Shitamoto ◽

Shuji Okaguchi ◽

Nobuaki Takahashi ◽

Izumi Takeuchi ◽

...

Keyword(s):

Full Scale ◽

Bending Test ◽

Test Program ◽

Bending Tests ◽

Girth Welding ◽

Manufacturing Procedure ◽

Girth Welds ◽

Welding Procedure ◽

Pipe Manufacturing ◽

Pipe Bending

This study was planned as a part of a test program to confirm the effect of girth welds on the strain capacity of pipes. In this study, full-scale pipe bending tests are performed by using X80 SAW pipe. This paper covers pipe manufacturing procedure, developed welding procedure to obtain even match weld metal and properties of welded joints. And this work demonstrated that the X80 pipes welded under the developed procedure fractured in base metal remote from girth welded portion by full scale pipe bending test conducted under the internal pressure of 72% SMYS of X80.

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Application of Thermal Analysis Tool for Girth Welding Procedure Qualification

Volume 3: Operations, Monitoring and Maintenance; Materials and Joining ◽

10.1115/ipc2016-64629 ◽

2016 ◽

Author(s):

Aditya Dekhane ◽

Alex Wang ◽

Yong-Yi Wang ◽

Marie Quintana

Keyword(s):

Mechanical Properties ◽

Arc Welding ◽

Gas Metal Arc Welding ◽

Welding Parameters ◽

Analysis Tool ◽

Thermal Cycles ◽

Cooling Rates ◽

Metal Arc Welding ◽

Girth Welding ◽

Welding Procedure

The mechanical properties of welds are governed by the final microstructure that develops as an interaction between the chemical composition and cooling rates produced by welding thermal cycles. For welds in modern microalloyed thermomechanically controlled processed (TMCP) pipeline steels, the microstructure and mechanical properties can be extremely sensitive to cooling rates. The development and qualification of welding procedures to achieve targeted mechanical properties is often an iterative process. Accurate knowledge of welding thermal cycles and cooling rates as a function of welding parameters is valuable for optimization of welding process development. This paper covers the development, validation, and application of a girth welding thermal analysis tool. The core of the tool is a numerical model that has a two-dimensional, axi-symmetrical finite element procedure to simulate the transient heat transfer processes both in the weld metal and the heat affected zone (HAZ). The tool takes welding parameters, pipe and bevel geometry, and thermal properties as inputs and predicts thermal cycles and cooling rates in weld metal and HAZ. The comparison of thermal cycles between experimental measurements and the model predictions show the tool was robust and accurate. This tool is particularly effective in understanding the thermal history and resulting microstructure and mechanical properties of welds produced with high-productivity gas metal arc welding (GMAW), such as mechanized dual-torch pulsed gas metal arc welding (DT GMAW-P). The tool was used in optimization of development and qualification of welding procedures of a DT GMAW-P process under a tight time schedule. The actual welds were fabricated according to the optimized welding procedures followed by the mechanical testing of welds. Good agreement was found between the predicted tensile properties and those from experimental tests. The welding procedures were qualified within the tight time schedule by avoiding iterative trials, and reducing the cost associated with the making of trial welds and mechanical testing by approximately 50%. This tool has also been applied in the application of essential welding variables methodology (EWVM) for X80 and X70 linepipe steels [1, 2]. Future applications of the tools include the revamp of the approach to essential variables in welding procedure qualification. In particular, the parameters affecting cooling rates may be “bundled” together towards the one critical factor affecting weld properties, i.e., cooling rate. The individual parameters may be varied beyond the limits in the current codes and standards as long as their combined effects make the cooling rate stay within a narrow band. It is expected that the same framework of approaches to GMAW processes can be extended other welding processes, such as FCAW and SMAW.

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