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.

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.

scholarly journals Laser Welding of New Grade of Advanced High Strength Steel STRENX 1100 MC

2017 ◽  
Vol 62 (3) ◽  
pp. 1651-1657 ◽  
Author(s):  
A. Kurc-Lisiecka ◽  
J. Piwnik ◽  
A. Lisiecki
Keyword(s):  
Laser Welding ◽  
Base Metal ◽  
Mechanical Performance ◽  
High Strength ◽  
Carbon Equivalent ◽  
Welding Parameters ◽  
Low Carbon ◽  
Butt Joints ◽  
Significant Drop ◽  
Metal Impact

AbstractThe article presents results of investigations on autogenous laser welding of new grade STRENX 1100 MC steel. The modern Disk laser was applied for of 5.0 mm thick butt joints welding. The influence of laser welding parameters, mainly the energy input of laser welding on the penetration shape, weld quality, structure and mechanical performance was investigated. It was found that the investigated steel has surprisingly low carbon equivalent CET just 0.328, and also relatively high temperature of martensitic transformation Msat 430.6°C. Despite very rapid cooling times t8/5in a range from 0.6 to 1.3 s, thus rapid solidification there was no tendency to cracking of weld metal or HAZ. Significant drop of microhardness in the HAZ resulted in a decrease of tensile strength of joints, compared to the base metal. Impact toughness of test joints was at only 50÷60% of the base metal.

Examinations Regarding the Sour Gas Resistance of Girth Welds Carried Out on API Grade X80 Seamless Pipe Steel (Heavy Wall)

2014 ◽  
Author(s):  
Diana Toma ◽  
Jörg Wiebe ◽  
Dorothee Niklasch ◽  
Ashraf Koka
Keyword(s):  
High Strength ◽  
Mechanical Tests ◽  
Carbon Equivalent ◽  
Welding Parameters ◽  
Line Pipe ◽  
Sea Bed ◽  
Steel Grades ◽  
Girth Welds ◽  
Welding Procedure ◽  
Sour Gas

Various accessories such as buckle arrestors and J-lay collars are needed in some cases to successfully lay and secure an offshore pipeline on the sea bed. For such applications the using of high strength seamless pipes in Grade X70 and X80 with heavy wall are necessary. However, there is only small information regarding the welding procedure for such grades in heavy wall dimensions. In comparison to steels used for lower strength level, the chemistry of high strength steel pipes includes higher amounts of micro-alloying elements as well as requires a more complex heat treatment. Due to the higher carbon equivalent these steel grades react more sensitive on heat input during welding. Consequently, the range of welding parameters which ensure suitable mechanical properties has to be adapted. This article presents the results of weldability trials carried out on seamless API X80 heavy wall (> 50mm) line pipe. The welding trials were performed using different preheating temperatures and heat inputs followed by microstructure investigations and mechanical tests of the multilayer welds. The sour gas resistance has to be demonstrated by SSC-tests because it stays challenging to guarantee values below 250 HV10.

Effect of the Root Gap on the Structure and Properties of High Strength Steel S700MC Welds

2021 ◽  
Vol 890 ◽  
pp. 201-208
Author(s):  
Nikolay Ferdinandov ◽  
Danail Gospodinov ◽  
Mariana Ilieva ◽  
Rossen Radev
Keyword(s):  
High Strength Steels ◽  
High Strength ◽  
Pressure Vessels ◽  
Coarse Grained ◽  
Carbon Equivalent ◽  
Welding Parameters ◽  
Low Carbon ◽  
Negative Effect ◽  
Ultra High Strength Steels ◽  
Time Required

Nowadays, the use of high strength (HS) and ultra-high strength steels (UHS) increases, notably in welded constructions. These steels are mainly exploited in heavy loaded welded constructions such as bridges, cranes and excavators, in pressure vessels, vehicles, ships, drilling rigs etc. working at room or lower temperatures. As the welded constructions have specific requirements, the development of high strength and ultra-high strength steels imposes the need for research on the factors influencing their weldability. Among the possible negative implications are: cold cracks formation, softening of the heat affected zone, brittleness in the coarse grained zone. When complying with the generally accepted rules for welding, HS and UHS are readily welded by all conventional welding methods. Recommendations for welding of steels after normalization, thermo-mechanical treatment and quenching and tempering are given in the standard EN 1011 -1, 2. The use of thermo-mechanically treated (hot-rolled) steels with low carbon equivalent, such as S700MC, allows reduction in time required for welding as the preheating temperature is lowered or even preheating is not necessary. A more pronounced negative effect on the weld quality has the presence of different defects. S700MC can be welded by all conventional methods, and a reduction in the softened zone can be achieved by using appropriate welding parameters. Joint preparation for welding of HS and UHS steels is described in the standards EN ISO 9692-1:2013 and EN ISO 9692-2:2001. Nevertheless, the root gap is often the closing part in constructions and does not comply with the standard recommendations. That is why the effect of the root gap on welds has to be researched. The present work introduces results of a research studying the effect of the root gap on the structure and some mechanical and technological properties of S700MS welds, welded by submerged arc welding.

scholarly journals The influence of the carbon equivalent on the weldability of high-strength low-alloy steel in the water environment

2019 ◽  
Vol 91 (5) ◽  
Author(s):  
Jacek Tomków ◽  
Michalina Tomków
Keyword(s):  
Weld Metal ◽  
Yield Point ◽  
Heat Affected Zone ◽  
Welded Joints ◽  
Water Environment ◽  
High Strength ◽  
Carbon Equivalent ◽  
Low Alloy Steels ◽  
Low Alloy Steel ◽  
Alloy Steels

From many years, the high strength low alloy steels are often used for offshore constructions. This constructions, due to the environment in which they work, require more frequent repairs than the constructions from the land. For economic reasons, repairs take place in the underwater conditions, however water significantly decreases the weldability of steel. The paper presents the results of the CTS weldability test for S460ML and S460 steels, which have a similar value of the yield point, but different carbon equivalent (CeMIS) values. The welded joints were cut into specimens, which were then subjected to Vickers HV10 hardness measurements. The experiment has shown that as the CeMIS value increases, the hardness in the heat affected zone (HAZ) of joints and in the weld metal increases.

ASTM A710

Alloy Digest ◽  
1990 ◽  
Vol 39 (4) ◽  
Keyword(s):  
Fracture Toughness ◽  
Tensile Properties ◽  
Precipitation Hardening ◽  
Steel Plate ◽  
High Strength ◽  
Heat Treating ◽  
Low Carbon ◽  
Bethlehem Steel Corporation ◽  
Strength Alloy ◽  
Carbon Precipitation

Abstract ASTM A710 is a low-carbon, precipitation hardening high-strength alloy steel plate. It is well suited to critical applications. This datasheet provides information on composition and tensile properties as well as fracture toughness. It also includes information on heat treating and joining. Filing Code: SA-446. Producer or source: Bethlehem Steel Corporation.

BETHSTAR 60

Alloy Digest ◽  
1986 ◽  
Vol 35 (8) ◽  
Keyword(s):  
Fracture Toughness ◽  
Yield Strength ◽  
Steel Plate ◽  
High Stress ◽  
High Strength ◽  
Heat Treating ◽  
Low Carbon ◽  
Bethlehem Steel Corporation ◽  
Low Sulfur ◽  
Minimum Yield

Abstract BethStar 60 steel plate is a high-strength product with a 60,000 psi minimum yield strength. It contains low carbon and low sulfur and has outstanding toughness, weldability and formability. It provides the design engineer with a an economical high-strength low-alloy (HSLA) grade that can be fabricated readily. Applications include weight-sensitive components subject to high stress such as frames for large off-highway haulers. This datasheet provides information on composition, physical properties, microstructure, elasticity, and tensile properties as well as fracture toughness. It also includes information on forming, heat treating, and joining. Filing Code: SA-421. Producer or source: Bethlehem Steel Corporation.

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.

A New Approach Using EBSD to Quantitatively Distinguish Complex Transformation Products Along the HAZ in X80 Linepipe Steel

2014 ◽  
Author(s):  
Jennifer M. Reichert ◽  
Matthias Militzer ◽  
Warren J. Poole ◽  
Laurie Collins
Keyword(s):  
Orientation Relationship ◽  
Transformation Temperature ◽  
Retained Austenite ◽  
Electron Backscatter Diffraction ◽  
High Strength ◽  
Transformation Products ◽  
Carbon Steels ◽  
Low Carbon ◽  
Structure Property ◽  
Linepipe Steel

State-of-the-art linepipe steels are microalloyed low-carbon steels that combine high strength and fracture toughness with good weldability. During welding of pipe sections the heat affected zone (HAZ) experiences rapid thermal cycles resulting in a graded microstructure that can be significantly different from that of the base metal. In particular a variety of bainitic microstructures can form in the HAZ. Depending on the type of bainite mechanical properties may be improved or may lead to poor fracture resistance and be detrimental to the overall HAZ performance. Optical microscopy is not sufficient to differentiate bainitic morphologies which vary with the transformation temperature. The investigated X80 linepipe steel also contains retained austenite at room temperature. Based on the retained austenite it is possible to characterize the orientation relationship (OR) between austenite and the transformation products. It is found that bainite shows an orientation relationship near Kurdjumov-Sachs with the prior austenite. Variant selection is related to the driving force for the bainite reaction and hence depends on the transformation temperature. In the current study Electron BackScatter Diffraction (EBSD) mapping is used to characterize transformation products based on their orientation relationship. This approach offers a quantitative way to determine volume fractions of different types of bainite in complex HAZ microstructures which is necessary to establish structure-property relationships of the HAZ.

Sign in / Sign up

Export Citation Format

Share Document